Electrospun Polycaprolactone (PCL) Degradation: An In Vitro and In Vivo Study

Core-shell electrospun polycaprolactone nanofibers, loaded with rifampicin and coated with silver nanoparticles, for tissue engineering applications

In the field of tissue engineering, the use of core-shell fibers represents an advantageous approach to protect and finely tune the release of bioactive compounds with the aim to regulate their efficacy. In this work, core-shell electrospun polycaprolactone nanofiber-based membranes, loaded with rifampicin and coated with silver nanoparticles, were developed and characterized. The membranes are composed by randomly oriented nanofibers with a homogeneous diameter, as demonstrated by scanning electron microscopy (SEM). An air-plasma treatment was applied to increase the hydrophilicity of the membranes as confirmed by contact angle measurements. The rifampicin release from untreated and air-plasma treated membranes, evaluated by UV spectrophotometry, displayed a similar and constant over-time release profile, demonstrating that the air-plasma treatment does not degrade the rifampicin, loaded in the core region of the nanofibers. The presence and the distribution of silver nanoparticles on the nanofiber surface were investigated by SEM and Energy Dispersive Spectroscopy. Moreover, SEM imaging demonstrated that the produced membranes possess a good stability over time, in terms of structure maintenance. The developed membranes showed a good biocompatibility towards murine fibroblasts, human osteosarcoma cells and urotheliocytes, reveling the absence of cytotoxic effects. Moreover, doble-functionalized membranes inhibit the growth of E. coli and S. aureus. Thanks to the possibilities offered by the coaxial electrospinning, the membranes here proposed are promising for several tissue engineering applications.

Electrospun "Hard-Soft" Interpenetrating Nanofibrous Tissue Scaffolds Facilitating Enhanced Mechanical Strength and Cell Proliferation

"Soft" hydrogel-based macroporous scaffolds have been widely used in tissue engineering and drug delivery applications due to their hydrated interfaces and macroporous structures, but have drawbacks related to their weak mechanics and often weak adhesion to cells. In contrast, "hard" poly(caprolactone) (PCL) electrospun fibrous networks have desirable mechanical strength and ductility but offer minimal interfacial hydration and thus limited capacity for cell proliferation. Herein, we demonstrate the fabrication of interpenetrating nanofibrous networks based on coelectrospun PCL and poly(oligoethylene glycol methacrylate) (POEGMA) nanofibers that exhibit the mechanical benefits of PCL but the interfacial hydration benefits of hydrogels. The electrospinning process results in partially aligned but interpenetrating fiber network with minimal internal phase separation, leading to anisotropic but strong mechanical properties even in the hydrated state; apparent ultimate tensile strengths of the swollen scaffolds ranged from 429 ± 39 kPa in the direction of fiber alignment (longitudinal) to 86 ± 25 kPa perpendicular to fiber alignment (cross-longitudinal), typical of PCL-based scaffolds and enabling efficient suture retention in different directions. However, contact angle measurements indicate hydrogel-like interfacial properties due to the presence of the interpenetrating POEGMA network. C2C12 myoblast proliferation in the PCL-POEGMA scaffolds was 50% higher than that observed on PCL-only scaffolds, a result attributed to the presence of the more hydrophilic POEGMA interpenetrating nanofiber network. Overall, this method is demonstrated to represent a facile single-step strategy to fabricate strong macroporous but still interfacially hydrophilic scaffolds for tissue engineering applications.

Bioengineering strategy to promote CNS nerve growth and regeneration via chronic glutamate signaling

Being part of the mature mammalian central nervous system, impairments of the retina and optic nerves caused by trauma or diseases often cannot be restored. Progressive degeneration of retinal ganglion cells (RGCs) in glaucoma and other optic neuropathies gradually leads to permanent vision loss, which currently has no cure. The purpose of this study is to develop a biocompatible scaffold to support RGC survival and guide axon growth, facilitating optic nerve repair and regeneration. We here report that electrical stimulation (ES) significantly promoted neurite outgrowth and elongation from primary RGCs, mediated through glutamate receptor signaling. To mimic prolonged glutamate stimulation and facilitate sustained nerve growth, we fabricated biocompatible poly-γ-benzyl-L-glutamate (PBG) scaffolds for controlled glutamate release. These PBG scaffolds supported RGC survival and robust long-distance nerve growth in both retinal explants and isolated RGC cultures. In contrast, control polycaprolactone (PCL) scaffolds with similar physical structures showed little benefits on RGC survival or nerve growth. Moreover, PBG scaffolds promoted the differentiation and neurite outgrowth from embryonic stem cell-derived RGC progenitors. The aligned PBG scaffold drove directed nerve elongation along the fiber alignment. Transplantation of PBG-coated biocompatible conduits induced robust optic nerve regeneration in adult mice following nerve transection. Together, the findings present the exciting possibility of driving optic nerve regeneration and RGC progenitor cell differentiation by imitating ES or glutamate signaling. PBG presents a permissive biomaterial in supporting robust and directed axon growth with promising clinical applications in the future. STATEMENT OF SIGNIFICANCE: We here reported compelling findings that demonstrate the potent regenerative effects of a bioengineered scaffold incorporating poly-γ-benzyl-L-glutamate (PBG) on the optic nerve. Retinal ganglion cell (RGC) axons, which form the optic nerve, are incapable of regenerating in adulthood, posing a significant hurdle in restoring vision for patients with optic nerve diseases or injuries. Built upon the finding that electrical stimulation promotes RGC axonal growth through glutamate signaling, we developed PBG scaffolds to provide sustained glutamate stimulation and showed their exceptional effects on driving directed axonal elongation in cultured RGCs and neural progenitors, as well as supporting robust optic nerve regeneration after transection in vivo. The findings hold great promise for reversing vision loss in patients with optic nerve conditions.

A tissue bandage for pelvic ganglia injury

Neurogenic bladder often occurs after pelvic ganglia injury. Its symptoms, like severe urinary retention and incontinence, have a significant impact on individuals' quality of life. Unfortunately, there are currently no effective treatments available for this type of injury. Here, we designed a fiber-enhanced tissue bandage for injured pelvic ganglia. Tight junctions formed in tissue bandages create a mini tissue structure that enhances resistance in an in vivo environment and delivers growth factors to support the healing of ganglia. Strength fibers are similar to clinical bandages and guarantee ease of handling. Furthermore, tissue bandages can be stored at low temperatures over 5 months without compromising cell viability, meeting the requirements for clinical products. A tissue bandage was applied to a male rat with a bilateral major pelvic ganglia crush injury. Compared to the severe neurogenic bladder symptoms observed in the injury and scaffold groups, tissue bandages significantly improved bladder function. We found that tissue bandage increases resistance to mechanical injury by boosting the expression of cytoskeletal proteins within the major pelvic ganglia. Overall, tissue bandages show promise as a practical therapeutic approach for ganglia repair, offering hope for developing more effective treatments for this thorny condition.

Electrospun PCL/Alginate/Nanoclay Nerve Conduit with Olfactory Ectomesenchymal Stem Cells for Nerve Regeneration

Biocompatible and biodegradable nerve growth conduits (NGCs) provide a promising alternative to conventional nerve grafting for peripheral nerve regeneration. Incorporating nanoclay (NC) has been shown to increase the hydrophilicity and flexibility of polymeric scaffolds. In the present study, poly caprolactone-alginate (PCL-ALG) conduits with varying percentages of NC (0.1%, 0.2%, and 0.5%) were fabricated using the electrospinning technique. The conduit containing 0.5% NC showed a greater increase in elongation (33%) and porosity, reaching 95% with the lowest contact angle (10°). For in vitro, human olfactory ectomesenchymal stem cells (OE-MSCs) were used as a favorable choice for neuronal differentiation owing to the origin from the neural crest. The viability and proliferation of OE-MSCs were maintained after 5 days on scaffolds with 0.5% NC, as confirmed by the MTT assay, cell adhesion analysis, and live/dead staining. Furthermore, the impact of 0.5% PCL-ALG-NC on the paracrine activity of OE-MSCs was studied for a period of 7 days. Our results indicated that human OE-MSCs, when cocultured with PC12 cells on NGC, have the capability to release nerve growth factor levels of up to 1392.83 pg/mL. In summary, the electrospun PCL-ALG conduit containing an optimal NC dosage (0.5%) and seeded with human OE-MSCs shows promising outcomes as NGC scaffold for peripheral nerve regeneration.

Advances in Electrospun Poly(ε-caprolactone)-Based Nanofibrous Scaffolds for Tissue Engineering

Tissue engineering has great potential for the restoration of damaged tissue due to injury or disease. During tissue development, scaffolds provide structural support for cell growth. To grow healthy tissue, the principal components of such scaffolds must be biocompatible and nontoxic. Poly(ε-caprolactone) (PCL) is a biopolymer that has been used as a key component of composite scaffolds for tissue engineering applications due to its mechanical strength and biodegradability. However, PCL alone can have low cell adherence and wettability. Blends of biomaterials can be incorporated to achieve synergistic scaffold properties for tissue engineering. Electrospun PCL-based scaffolds consist of single or blended-composition nanofibers and nanofibers with multi-layered internal architectures (i.e., core-shell nanofibers or multi-layered nanofibers). Nanofiber diameter, composition, and mechanical properties, biocompatibility, and drug-loading capacity are among the tunable properties of electrospun PCL-based scaffolds. Scaffold properties including wettability, mechanical strength, and biocompatibility have been further enhanced with scaffold layering, surface modification, and coating techniques. In this article, we review nanofibrous electrospun PCL-based scaffold fabrication and the applications of PCL-based scaffolds in tissue engineering as reported in the recent literature.

Amino Acid-Based Poly(ester urea) Biodegradable Membrane for Guided Bone Regeneration

Barrier membranes (BM) for guided bone regeneration (GBR) aim to support the osteogenic healing process of a defined bony defect by excluding epithelial (gingival) ingrowth and enabling osteoprogenitor and stem cells to proliferate and differentiate into bone tissue. Currently, the most widely used membranes for these approaches are collagen-derived, and there is a discrepancy in defining the optimal collagen membrane in terms of biocompatibility, strength, and degradation rates. Motivated by these clinical observations, we designed a collagen-free membrane based on l-valine-co-l-phenylalanine-poly(ester urea) (PEU) copolymer via electrospinning. Degradation and mechanical properties of these membranes were performed on as-spun and water-aged samples. Alveolar-bone-derived stem cells (AvBMSCs) were seeded on the PEU BM to assess their cell compatibility and osteogenic characteristics, including cell viability, attachment/spreading, proliferation, and mineralized tissue-associated gene expression. In vivo, PEU BMs were subcutaneously implanted in rats to evaluate their potential to cause inflammatory responses and facilitate angiogenesis. Finally, critical-size calvarial defects and a periodontal model were used to assess the regenerative capacity of the electrospun PEU BM compared to clinically available Cytoflex synthetic membranes. PEU BM demonstrated equal biocompatibility to Cytoflex with superior mechanical performance in strength and elasticity. Additionally, after 14 days, PEU BM exhibited a higher expression of BGLAP/osteocalcin and superior in vivo performance-less inflammation and increased CD31 and VWF expression over time. When placed in critical-sized defects in the calvaria of rats, the PEU BM led to robust bone formation with high expression of osteogenesis and angiogenesis markers. Moreover, our membrane enhanced alveolar bone and cementum regeneration in an established periodontal model after 8 weeks. We demonstrate that the PEU BM exhibits favorable clinical properties, including mechanical stability, cytocompatibility, and facilitated bone formation in vitro and in vivo. This highlights its suitability for GBR in periodontal and craniofacial bone defects.

Engineering Shape to Overcome Contraction: The Role of Polymer-Collagen Hybrids in Advanced Dermal Substitutes

Collagen gels are the standard dermal equivalents par excellence, however the problem of rapid cell-mediated contraction remains unresolved. Therefore, the development of hybrid constructs (HCs) based on collagen and polymeric scaffolds is proposed to address the mechanical instability that usually limits the formation of new, functional tissue. Equally important, these synthetic structures should be temporary (degradable) while ensuring that cells are well-adapted to the new extracellular environment. In this study, we screened a library of scaffolds made of various polymers, including homopolymers of polycaprolactone (PCL) and poly D,L-lactide (PLA50), their blends (PCL/PLA50), and copolymers (poly(D,L-lactide-co-caprolactone), PCLLA50) to prepare HCs in a layer-by-layer fashion. The properties of polymers and copolymers along with their processability by electrospinning and 3D-printing were evaluated. Then, we assessed the HCs resistance toward cell-mediated contraction as well as the degradation of the polymeric scaffolds. Our results indicate that scaffolds with higher PLA50 content (e.g., PLA50 100%, PCL/PLA50 or PCLLA50, both at 50/50 caprolactone-to-D,L-lactide molar ratio) presented more drawbacks in terms of handleability and processing, while those with greater PCL presence showed structural steadiness and ease to use. All the scaffolds integrated well with the collagen gel to form the corresponding HCs. With few exceptions, the HCs demonstrated good resistance to cell-derived contraction over 3 weeks. Notably, HCs based on PCLLA50 90/10 (both versions, electrospun or 3D-printed) performed best, showing only a 5%-17% area reduction compared to the 93% observed in collagen-only gels. This copolymer displayed hydrolytic degradation depending on its shape, with up to 45% and 65% loss of molecular weight for the electrospun and 3D-printed forms, respectively, correlating with their progressive change in mechanical features. HCs containing PCLLA50 90/10 also exhibited a better fibroblast distribution, enhanced myofibroblastic differentiation, and a three-fold increase in cell proliferation (when the electrospun type was used) compared to collagen controls. These findings were instrumental in selecting a potential HC that might be used for future experiments in vivo.

Combining human liver ECM with topographically featured electrospun scaffolds for engineering hepatic microenvironment

Liver disease cases are rapidly expanding worldwide, and transplantation remains the only effective cure for end-stage disease. There is an increasing demand for developing potential drug treatments, and regenerative therapies using in-vitro culture platforms. Human decellularized extracellular matrix (dECM) is an appealing alternative to conventional animal tissues as it contains human-specific proteins and can serve as scaffolding materials. Herein we exploit this with human donor tissue from discarded liver which was not suitable for transplant using a synergistic approach to combining biological and topographical cues in electrospun materials as an in-vitro culture platform. To realise this, we developed a methodology for incorporating human liver dECM into electrospun polycaprolactone (PCL) fibres with surface nanotopographies (230-580 nm). The hybrid scaffolds were fabricated using varying concentrations of dECM; their morphology, mechanical properties, hydrophilicity and stability were analysed. The scaffolds were validated using HepG2 and primary mouse hepatocytes, with subsequent results indicating that the modified scaffolds-maintained cell growth and influenced cell attachment, proliferation and hepatic-related gene expression. This work demonstrates a novel approach to harvesting the potential from decellularized human tissues in the form of innovative in-vitro culture platforms for liver.

Dual-layer nanofibrous PCL/gelatin membrane as a sealant barrier to prevent postoperative pancreatic leakage

Post-operative pancreatic leakage is a severe surgical complication that can cause internal bleeding, infections, multiple organ damage, and even death. To prevent pancreatic leakage and enhance the protection of the suture lining and tissue regeneration, a dual-layer nanofibrous membrane composed of synthetic polymer polycaprolactone (PCL) and biopolymer gelatin was developed. The fabrication of this dual-layer (PGI-PGO) membrane was achieved through the electrospinning technique, with the inner layer (PGI) containing 2% PCL (w/v) and 10% gelatin (w/v), and the outer layer (PGO) containing 10% PCL (w/v) and 10% gelatin (w/v) in mixing ratios of 2:1 and 1:1, respectively. Experimental results indicated that a higher gelatin content reduced fiber diameter enhanced the hydrophilicity of the PGI layer compared to the PGO layer, improved the membrane's biodegradability, and increased its adhesive properties. In vitro biocompatibility assessments with L929 fibroblast cells showed enhanced cell proliferation in the PGI-PGO membrane. In vivo studies confirmed that the PGI-PGO membrane effectively protected the suture line without any instances of leakage and promoted wound healing within four weeks post-surgery. In conclusion, the nanofibrous PGI-PGO membrane demonstrates a promising therapeutic potential to prevent postoperative pancreatic leakage.

Development of multilayered artificial urethra graft for urethroplasty

To enhance the treatment of patients' urethral defects, such as strictures and hypospadias, we investigated the potential of using artificial urethral tissue. Our study aimed to generate this tissue and assess its effectiveness in a rabbit model. Two types of bioprinted grafts, based on methacrylated gelatin-silk fibroin (GelMA-SF) hydrogels, were produced: acellular, as well as loaded with autologous rabbit stem cells. Rabbit adipose stem cells (RASC) were differentiated toward smooth muscle in the GelMA-SF hydrogel, while rabbit buccal mucosa stem cells (RBMC), differentiated toward the epithelium, were seeded on its surface, forming two layers of the cell-laden tissue. The constructs were then reinforced with polycaprolactone-polylactic acid meshes to create implantable multilayered artificial urethral grafts. In vivo experiments showed that the cell-laden tissue integrated into the urethra with less fibrosis and inflammation compared to its acellular counterpart. Staining to trace the implanted cells confirmed integration into the host organism 3 months postsurgery.

Bacteria-responsive functional electrospun membrane: simultaneous on-site visual monitoring and inhibition of bacterial infection

Skin infections are a major threat to human health. Early diagnosis of bacterial infections is of great significance for implementing protective measures on the skin. Therefore, in this study, we designed an electrospun membrane (PPBT) for visual monitoring of colonized bacteria and responsive antibacterial ability. Specifically, the acidity of the microenvironment caused by bacterial metabolism was applied to drive the color change of bromothymol blue (BTB) on the PPBT membrane from green to yellow, thereby facilitating the early warning of infection and timely treatment. Within 4 h, different concentrations of Staphylococcus aureus (∼105 CFU mL-1), Escherichia coli (∼105 CFU mL-1), Pseudomonas aeruginosa (∼105 CFU mL-1) and Candida albicans (∼104 CFU mL-1) were visually monitored. Moreover, as the local acidity was enhanced via microbial metabolism, ZIF-8 nanoparticles loaded with TCS (TCS@ZIF-8) on the PPBT membrane could release TCS in an acid-responsive manner. At the same time, ROS were generated under 405 nm irradiation to achieve synergistic antibacterial ability. Experiments confirmed that the PPBT membrane has ideal and controllable antibacterial features based on acid responsive release and a synergistic photocatalytic antibacterial mechanism after monitoring. Therefore, the PPBT membrane developed in this work provides a feasible solution for bacterial monitoring and inactivation devices. More importantly, it can be beneficial for meeting the needs of clinical diagnosis and timely treatment of bacterial infection.

Electrospun bioresorbable polymer membranes for coronary artery stents

Percutaneous coronary intervention, a common treatment for atherosclerotic coronary artery lesions, occasionally results in perforations associated with increased mortality rates. Stents coated with a bioresorbable polymer membrane may offer an effective solution for sealing coronary artery perforations. Additionally, such coatings could be effective in mitigating neointimal hyperplasia within the vascular lumen and correcting symptomatic aneurysms. This study examines polymer membranes fabricated by electrospinning of polycaprolactone, polydioxanone, polylactide-co-caprolactone, and polylactide-co-glycolide. In uniaxial tensile tests, all the materials appear to surpass theoretically derived elongation thresholds necessary for stent deployment, albeit polydioxanone membranes are found to disintegrate during the experimental balloon expansion. As revealed by in vitro hemocompatibility testing, polylactide-co-caprolactone membranes exhibit higher thrombogenicity compared to other evaluated polymers, while polylactide-co-glycolide samples fail within the first day post-implantation into the abdominal aorta in rats. The PCL membrane exhibited significant water leakage in the permeability test. Comprehensive evaluation of mechanical testing, bio- and hemocompatibility, as well as biodegradation dynamics shows the advantage of membranes based on and the mixture of polylactide-co-caprolactone and polydioxanone over other polymer groups. These findings lay a foundational framework for conducting preclinical studies on stent configurations in large laboratory animals, emphasizing that further investigations under conditions closely mimicking clinical use are imperative for making definitive conclusions.

Synthesis and characterization of new electrospun medical scaffold-based modified cellulose nanofiber and bioactive natural propolis for potential wound dressing applications

Recently, the design of polymer nanofibers using the electrospinning process has attracted much interest. Particularly the use of natural polymers has promoted many advantages in their biomedical applications. However, the combination of multiple natural polymers remains a great challenge in terms of electrospun production and applied performance. From this perspective, the current investigation highlights the study of the preparation of electrospun nanomaterial scaffolds based on combined natural polymers for improved wound healing performance. First, we have synthesized a crosslinked polymer by reacting microcrystalline cellulose (MC) and chitosan (CS) biopolymer via the intermediate of citric acid as a crosslinking agent. Then a natural propolis biomolecule was incorporated into the polymer network. Different MC/CS blend ratios of 90/10 and 70/30 were then used and various machine parameters were optimized to obtain nanofiber scaffolds with excellent strength and structures. SEM, IR, physicochemical, mechanical, and morpho-logical characterization were then performed. SEM evaluation revealed homogeneous and bead-free nanofibrous structures, with well-defined morphology and a random deposition that could accurately mimic the extracellular matrix of native skin. The calculated average nanofiber diameters for the MC/CS blend ratios at 90/10 and 70/30 were 431.4 and 441.2 nm, respectively. The results showed that when the chitosan amount increased, larger nanofibers with narrow diameter distribution appeared. The prepared nanomaterials had a significant and close water vapor permeability of about 1735.12 and 1698.52 g per m per day for the two blend ratios of 90/10 and 70/30, respectively. The examination of swelling behavior revealed a noteworthy enhancement in hydrophilicity, a necessary attribute for improved healing efficacy. FT-IR analysis confirmed the success and the stability of the chemical crosslinking reaction between the two biopolymers before nanofiber conception. Excellent mechanical properties were acquired, based on the chitosan content. Both developed nanofiber scaffolds exhibited high tensile strength and Young's modulus values. The incorporation of 30% chitosan versus 10% results in an increase in tensile strength of 11% and 14% in Young's modulus. Therefore, we could adjust the different mechanical properties simply by varying the mixing rate of the electrospun polymers. Using epithelial HepG2 cells, viability and kinetic cell adhesion assays were assessed to obtain biological evaluation. No cytotoxicity was observed and good cytocompatibility was confirmed. Functionalized nanofiber biomaterials with different MC/CS ratios substantiated significant bactericidal effectiveness against Gram-positive and Gram-negative bacterial culture strains. The novel functional electrospun wound dressing scaffold demonstrated effective and promising biomedical performance, healing both acute and chronic wounds.

Surface-Conjugated Galactose on Electrospun Polycaprolactone Nanofibers: An Innovative Scaffold for Uterine Tissue Engineering

The uterus, a vital organ in the female reproductive system, nurtures and supports developing embryos until maturity. This study focuses on addressing uterine related problems by creating a nanofibrous scaffold to regenerate uterine myometrial tissue, closely resembling the native extracellular matrix (ECM) for enhanced efficacy. To achieve this, we utilized polycaprolactone (PCL) as a biomaterial and employed an electrospinning technique to generate PCL nanofibers in both random and aligned orientations. Due to the inherent hydrophobic nature of PCL nanofibers, a two-step wet chemistry surface modification technique is used, involving the conjugation of galactose onto them. Galactose, a lectin-binding sugar, was chosen to enhance the scaffold's hydrophilicity, thereby improving cell adhesion and fostering l-selectin-based interactions between the scaffold and uterine cells. These interactions, in turn, activated uterine fibroblasts, leading to ECM remodeling. The optimized electrospinning process successfully generated random and aligned nanofibers. Subsequent surface modification was carried out, and the modified scaffold was subjected to various physicochemical characterization, such as the ninhydrin assay, enzyme-linked lectin assay techniques that revealed successful galactose conjugation, and mechanical characterization to assess any changes in material bulk properties resulting from the modification. The tensile strength of random galactose-modified PCL fibers reached 0.041 ± 0.01 MPa, outperforming random unmodified PCL fibers (0.026 ± 0.01 MPa), aligned unmodified PCL fibers (0.011 ± 0.001 MPa), and aligned modified PCL fibers (0.016 ± 0.002 MPa). Cytocompatibility studies with human uterine fibroblast cells showed enhanced viability and proliferation on the modified scaffolds. Initial pilot studies were attempted in the current study involving subcutaneous implantation in the dorsal area of Wistar rats to assess biocompatibility and tissue response before proceeding to intrauterine implantation indicated that the modification did not induce adverse inflammation in vivo. In conclusion, our study introduces a surface-modified PCL nanofibrous material for myometrial tissue engineering, offering promise in addressing myometrial damage and advancing uterine health and reproductive well-being.

Non-immune factors cause prolonged myofibroblast phenotype in implanted synthetic heart valve scaffolds

The clinical application of heart valve scaffolds is hindered by complications associated with the activation of valvular interstitial cell-like (VIC-like) cells and their transdifferentiation into myofibroblasts. This study aimed to examine several molecular pathway(s) that may trigger the overactive myofibroblast phenotypes in the implanted scaffolds. So, we investigated the influence of three molecular pathways - macrophage-induced inflammation, the TGF-β1-SMAD2, and WNT/β-catenin β on VIC-like cells during tissue engineering of heart valve scaffolds. We implanted electrospun heart valve scaffolds in adult sheep for up to 6 months in the right ventricular outflow tract (RVOT) and analyzed biomolecular (gene and protein) expression associated with the above three pathways by the scaffold infiltrating cells. The results showed a gradual increase in gene and protein expression of markers related to the activation of VIC-like cells and the myofibroblast phenotypes over 6 months of scaffold implantation. Conversely, there was a gradual increase in macrophage activity for the first three months after scaffold implantation. However, a decrease in macrophage activity from three to six months of scaffold tissue engineering suggested that immunological signal factors were not the primary cause of myofibroblast phenotype. Similarly, the gene and protein expression of factors associated with the TGF-β1-SMAD2 pathway in the cells increased in the first three months but declined in the next three months. Contrastingly, the gene and protein expression of factors associated with the WNT/β-catenin pathway increased significantly over the six-month study. Thus, the WNT/β-catenin pathway could be the predominant mechanism in activating VIC-like cells and subsequent myofibroblast phenotype.

Melt electrowriting of poly(ϵ-caprolactone)-poly(ethylene glycol) backbone polymer blend scaffolds with improved hydrophilicity and functionality

Melt electrowriting (MEW) is an additive manufacturing technique that harnesses electro-hydrodynamic phenomena to produce 3D-printed fibres with diameters on the scale of 10s of microns. The ability to print at this small scale provides opportunities to create structures with incredibly fine resolution and highly defined morphology. The current gold standard material for MEW is poly(ϵ-caprolactone) (PCL), a polymer with excellent biocompatibility but lacking in chemical groups that can allow intrinsic additional functionality. To provide this functionality while maintaining PCL's positive attributes, blending was performed with a Poly(Ethylene Glycol) (PEG)-based Acrylate endcapped Urethane-based Precursor (AUP). AUPs are a group of polymers, built on a backbone of existing polymers, which introduce additional functionality by the addition of one or more acrylate groups that terminate the polymer chain of a backbone polymer. By blending with a 20kDa AUP-PEG in small amounts, it is shown that MEW attributes are preserved, producing high-quality meshes. Blends were produced in various PCL:AUP weight ratios (100:0, 90:10 and 0:100) and processed into both solvent-cast films and MEW meshes that were used to characterise the properties of the blends. It was found that the addition of AUP-PEG to PCL significantly increases the hydrophilicity of structures produced with these polymers, and adds swelling capability compared to the non-swelling PCL. The developed blend (90:10) is shown to be processable using MEW, and the quality of manufactured scaffolds is evaluated against pure PCL scaffolds by performing scanning electron microscopy image analysis, with the quality of the novel MEW blend scaffolds showing comparable quality to that of pure PCL. The presence of the functionalisable AUP material on the surface of the developed scaffolds is also confirmed using fluorescence labelling of the acrylate groups. Biocompatibility of the MEW-processable blend was confirmed through a cell viability study, which found a high degree of cytocompatibility.

Electrospun scaffolds based on a PCL/starch blend reinforced with CaO nanoparticles for bone tissue engineering

Electrospun nanocomposite scaffolds with improved bioactive and biological properties were fabricated from a blend of polycaprolactone (PCL) and starch, and then combined with 5 wt% of calcium oxide (CaO) nanoparticles sourced from eggshells. SEM analyses showed scaffolds with fibrillar morphology and a three-dimensional structure. The hydrophilicity of scaffolds was improved with starch and CaO nanoparticles, which was evidenced by enhanced water absorption (3500 %) for 7 days. In addition, PCL/Starch/CaO scaffolds exhibited major degradation, with a mass loss of approximately 60 % compared to PCL/Starch and PCL/CaO. The PCL/Starch/CaO scaffolds decreased in crystallinity as intermolecular interactions between the nanoparticles retarded the mobility of the polymeric chains, leading to a significant increase in Young's modulus (ca. 60 %) and a decrease in tensile strength and elongation at break, compared to neat PCL. SEM-EDS, FT-IR, and XRD analyses indicated that PCL/Starch/CaO scaffolds presented a higher biomineralization capacity due to the ability to form hydroxyapatite (HA) in their surface after 28 days. The PCL/Starch/CaO scaffolds showed attractive biological performance, allowing cell adhesion and viability of M3T3-E1 preosteoblastic cells. In vivo analysis using a subdermal dorsal model in Wistar rats showed superior biocompatibility and improved resorption process compared to a pure PCL matrix. This biological analysis suggested that the PCL/Starch/CaO electrospun mats are suitable scaffolds for guiding the regeneration of bone tissue.

The Modulation of Respiratory Epithelial Cell Differentiation by the Thickness of an Electrospun Poly-ε-Carprolactone Mesh Mimicking the Basement Membrane

The topology of the basement membrane (BM) affects cell physiology and pathology, and BM thickening is associated with various chronic lung diseases. In addition, the topology of commercially available poly (ethylene terephthalate) (PET) membranes, which are used in preclinical in vitro models, differs from that of the human BM, which has a fibrous and elastic structure. In this study, we verified the effect of BM thickness on the differentiation of normal human bronchial epithelial (NHBE) cells. To evaluate whether the thickness of poly-ε-carprolactone (PCL) mesh affects the differentiation of NHBE cells, cells were grown on thin- (6-layer) and thick-layer (80-layer) meshes consisting of electrospun PCL nanofibers using an air-liquid interface (ALI) cell culture system. It was found that the NHBE cells formed a normal pseudostratified epithelium composed of ciliated, goblet, and basal cells on the thin-layer PCL mesh; however, goblet cell hyperplasia was observed on the thick-layer PCL mesh. Differentiated NHBE cells cultured on the thick-layer PCL mesh also demonstrated increased epithelial-mesenchymal transition (EMT) compared to those cultured on the thin-layer PCL mesh. In addition, expression of Sox9, nuclear factor (NF)-κB, and oxidative stress-related markers, which are also associated with goblet cell hyperplasia, was increased in the differentiated NHBE cells cultured on the thick-layer PCL mesh. Thus, the use of thick electrospun PCL mesh led to NHBE cells differentiating into hyperplastic goblet cells via EMT and the oxidative stress-related signaling pathway. Therefore, the topology of the BM, for example, thickness, may affect the differentiation direction of human bronchial epithelial cells.

The nano-artificial periosteum made of PCL/MgO/AS-IV enhances MC3T3-E1 cell osteogenic differentiation and promotes bone defect repair via the EphB4/EphrinB2 signaling pathway

Bone regeneration plays a pivotal role in periodontal tissue repair. With advancements in biotechnology materials, the utilization of nanotechnology offers a reliable platform for bone restoration in periodontitis. In this study, we successfully established a long-term bacterial infection model using Porphyromonas gingivalis (P. gingivalis) with MOI = 50. CCK-8 and ROS immunofluorescence results demonstrated that the combined effect of Mg2+ and AS-IV significantly enhanced cell proliferation and effectively suppressed the inflammatory response during bacterial infection. Alkaline phosphatase and alizarin red staining revealed that the synergistic action of Mg2+ and AS-IV notably promoted osteogenic differentiation of MC3T3-E1 cells under P. gingivalis-infected conditions. Considering the properties of these two biomaterials, we fabricated polycaprolactone (PCL) artificial periosteum loaded with MgO and AS-IV using an electrostatic spinning technique. The findings indicated that PCL/MgO/AS-IV artificial periosteum exhibited excellent biocompatibility and hydrophilicity, thereby substantially enhancing cellular adhesion to its surface as well as augmenting cellular value-added rate. Moreover, efficient drug release from the PCL/MgO/AS-IV artificial bone membrane conferred remarkable antimicrobial activity along with in vitro osteogenic potentiality. The in vivo experiments conducted on animals further substantiated the exceptional properties exhibited by PCL/MgO/AS-IV artificial periosteum in bone defect repair. Additionally, it was observed that PCL/MgO/AS-IV artificial periosteum could modulate EphB4-EphrinB2 signaling to enhance osteogenic differentiation under P.gingivalis-infected conditions.This exciting outcome suggests that PCL/MgO/AS-IV artificial periosteum holds great promise as a biomaterial for treating periodontal bone loss.

Drug-Modified Contact Lenses-Properties, Release Kinetics, and Stability of Active Substances with Particular Emphasis on Cyclosporine A: A Review

The following review focuses on the manufacturing and parameterizing of ocular drug delivery systems (DDS) using polymeric materials to create soft contact lenses. It discusses the types of drugs embedded into contact lenses, the various polymeric materials used in their production, methods for assessing the mechanical properties of polymers, and techniques for studying drug release kinetics. The article also explores strategies for investigating the stability of active substances released from contact lenses. It specifically emphasizes the production of soft contact lenses modified with Cyclosporine A (CyA) for the topical treatment of specific ocular conditions. The review pays attention to methods for monitoring the stability of Cyclosporine A within the discussed DDS, as well as investigating the influence of polymer matrix type on the stability and release of CyA.

Biomimetic Scaffolds for Regeneration of Temporomandibular Joint Disc: A Narrative Review

Defects and dysfunctions of temporomandibular joint (TMJ) disc are responsible for the majority of TMJ diseases. Current treatments in this matter are usually short-term and only palliative, thus an alternative treatment that offers long-lasting repair is in great demand. In recent years great attempts have been made to prepare an ideal scaffold, which best resembles the native TMJ disc in characteristics such as mechanical, physical and biological properties. This narrative review focuses on developments of the recent ten years in fabrication of scaffolds using decellularized tissues, natural and synthetic biomaterials for regeneration of TMJ disc and compared their properties. PubMed and Google Scholar databases were searched using the following keywords ("TMJ" OR "temporomandibular joint" OR "TMD" OR "temporomandibular disease") AND ("scaffold" OR "hydrogels"). Randomized controlled trials, randomized clinical trials, case-controls, case reports, and animal studies were included. Comments, systematic reviews, meta-analyses, and non-English papers were excluded. The study concluded that hybrid scaffolds have exhibited favorable cell attachment and proliferation. Synthetic scaffolds have shown promise in providing better control over structural properties; however, additional processes are often required to provide biomimetic cell signaling. While there is still much to learn about the ideal scaffold for TMJ disc regeneration, both natural and synthetic scaffolds have shown promise in achieving the functional, structural, biological, and mechanical properties of a native TMJ disc.

Three-Dimensional-Printed Composite Scaffolds Containing Poly-ε-Caprolactone and Strontium-Doped Hydroxyapatite for Osteoporotic Bone Restoration

A challenge in tissue engineering and the pharmaceutical sector is the development of controlled local release of drugs that raise issues when systemic administration is applied. Strontium is an example of an effective anti-osteoporotic agent, used in treating osteoporosis due to both anti-resorptive and anabolic mechanisms of action. Designing bone scaffolds with a higher capability of promoting bone regeneration is a topical research subject. In this study, we developed composite multi-layer three-dimensional (3D) scaffolds for bone tissue engineering based on nano-hydroxyapatite (HA), Sr-containing nano-hydroxyapatite (SrHA), and poly-ε-caprolactone (PCL) through the material extrusion fabrication technique. Previously obtained HA and SrHA with various Sr content were used for the composite material. The chemical, morphological, and biocompatibility properties of the 3D-printed scaffolds obtained using HA/SrHA and PCL were investigated. The 3D composite scaffolds showed good cytocompatibility and osteogenic potential, which is specifically recommended in applications when faster mineralization is needed, such as osteoporosis treatment.

Alternating Current Electrospinning of Polycaprolactone/Chitosan Nanofibers for Wound Healing Applications

Traditional wound dressings have not been able to satisfy the needs of the regenerative medicine biomedical area. With the aim of improving tissue regeneration, nanofiber-based wound dressings fabricated by electrospinning (ES) processes have emerged as a powerful approach. Nowadays, nanofiber-based bioactive dressings are mainly developed with a combination of natural and synthetic polymers, such as polycaprolactone (PCL) and chitosan (CHI). Accordingly, herein, PCL/CHI nanofibers have been developed with varying PCL:CHI weight ratios (9:1, 8:2 and 7:3) or CHI viscosities (20, 100 and 600 mPa·s) using a novel alternating current ES (ACES) process. Such nanofibers were thoroughly characterized by determining physicochemical and nanomechanical properties, along with wettability, absorption capacity and hydrolytic plus enzymatic stability. Furthermore, PCL/CHI nanofiber biological safety was validated in terms of cytocompatibility and hemocompatibility (hemolysis < 2%), in addition to a notable antibacterial performance (bacterial reductions of 99.90% for S. aureus and 99.91% for P. aeruginosa). Lastly, the enhanced wound healing activity of PCL/CHI nanofibers was confirmed thanks to their ability to remarkably promote cell proliferation, which make them ideal candidates for long-term applications such as wound dressings.

Novel Bioresorbable Drug-Eluting Mesh Scaffold for Therapy of Muscle Injury

A novel bioresorbable drug-eluting polycaprolactone (PCL) mesh scaffold was developed, utilizing a solvent-cast additive manufacturing technique, to promote therapy of muscle injury. The degradation rate and mechanical properties strength of the PCL mesh were characterized after immersion in a buffer solution for different times. The in vitro release characteristics of vancomycin, ceftazidime, and lidocaine from the prepared mesh were evaluated using a high-performance liquid chromatography (HPLC) assay. In addition, the in vivo efficacy of PCL meshes for the repair of muscle injury was investigated on a rat model with histological examinations. It was found that the additively manufactured PCL meshes degraded by 13% after submission in buffered solution for four months. All PCL meshes with different pore sizes exhibited greater strength than rat muscle and survived through 10,000 cyclic loadings. Furthermore, the meshes could offer a sustained release of antibiotics and analgesics for more than 3 days in vitro. The results of this study suggest that drug-loaded PCL mesh exhibits superior ability to pure PCL mesh in terms of effectively promoting muscle repair in rat models. The histological assay also showed adequate biocompatibility of the resorbable meshes. The additively manufactured biodegradable drug-eluting meshes may be adopted in the future in humans for the therapy of muscle injuries.

Polyglycerol sebacate-based elastomeric materials for arterial regeneration

Synthetic vascular grafts are commonly used in patients with severe occlusive arterial disease when autologous grafts are not an option. Commercially available synthetic grafts are confronted with challenging outcomes: they have a lower patency rate than autologous grafts and are currently unable to promote arterial regeneration. Polyglycerol sebacate (PGS), a non-toxic polymer with a tunable degradation profile, has shown promising results as a small-diameter vascular graft component that can support the formation of neoarteries. In this review, we first present an overview of the synthesis and modification of PGS followed by an examination of its mechanical properties. We then report on the performance, degradation, regeneration, and remodeling of PGS-based small-diameter vascular grafts, with a focus on efforts to reduce thrombosis, prevent dilation, and promote cellular residency and extracellular matrix regeneration that resembles the native artery in spatial distribution and organization. We also highlight recent advances in the incorporation of novel in situ cell sources for arterial regeneration and their potential application in PGS-based vascular grafts. Finally, we compare vascular grafts fabricated using PGS-based materials with other elastomeric alternatives.

Hierarchical Composite Scaffold with Deferoxamine Delivery System to Promote Bone Regeneration via Optimizing Angiogenesis

A bone defect refers to the loss of bone tissue caused by trauma or lesion. Bone defects result in high morbidity and deformity rates worldwide. Autologous bone grafting has been widely applied in clinics as the gold standard of treatment; however, it has limitations. Hence, bone tissue engineering has been proposed and developed as a novel therapeutic strategy for treating bone defects. Rapid and effective vascularization is essential for bone regeneration. In this study, a hierarchical composite scaffold with deferoxamine (DFO) delivery system, DFO@GMs-pDA/PCL-HNTs (DGPN), is developed, focusing on vascularized bone regeneration. The hierarchical structure of DGPN imitates the microstructure of natural bone and interacts with the local extracellular matrix, facilitating cell adhesion and proliferation. The addition of 1 wt% of halloysite nanotubes (HNTs) improves the material properties. Hydrophilic and functional groups conferred by polydopamine (pDA) modifications strengthen the scaffold bioactivity. Gelatin microspheres (GMs) protect the pharmacological activity of DFO, achieving local application and sustained release for 7 days. DFO effectively promotes angiogenesis by activating the signaling pathway of hypoxia inducible factor-1 α. In addition, DFO synergizes with HNTs to promote osteogenic differentiation and matrix mineralization. These results indicate that DGPN promotes bone regeneration and accelerates cranial defect healing.

Combination of melt-electrospun poly-ε-caprolactone scaffolds and hepatocyte-like cells from footprint-free hiPSCs to create 3D biohybrid constructs for liver tissue engineering

The liver is a vital organ with numerous functions, including metabolic functions, detoxification, and the synthesis of secretory proteins. The increasing prevalence of liver diseases requires the development of effective treatments, models, and regenerative approaches. The field of liver tissue engineering represents a significant advance in overcoming these challenges. In this study, 3D biohybrid constructs were created by combining hepatocyte-like cells (HLCs) derived from patient-specific footprint-free human induced pluripotent stem cells (hiPSCs) and 3D melt-electrospun poly-ε-caprolactone (PCL) scaffolds. First, a differentiation procedure was established to obtain autologous HCLs from hiPSCs reprogrammed from renal epithelial cells using self-replicating mRNA. The obtained cells expressed hepatocyte-specific markers and exhibited important hepatocyte functions, such as albumin synthesis, cytochrome P450 activity, glycogen storage, and indocyanine green metabolism. Biocompatible PCL scaffolds were fabricated by melt-electrospinning and seeded with pre-differentiated hepatoblasts, which uniformly attached to the fibers of the scaffolds and successfully matured into HLCs. The use of patient-specific, footprint-free hiPSC-derived HLCs represents a promising cell source for personalized liver regeneration strategies. In combination with biocompatible 3D scaffolds, this innovative approach has a broader range of applications spanning liver tissue engineering, drug testing and discovery, and disease modeling.

Drivers of vascular growth and remodeling: A computational framework to promote benign adaptation in the Ross procedure

In the sixties, Dr Donald Ross designed a surgical solution for young patients with aortic valve disease by using the patients' own pulmonary valve. The Ross procedure is the only aortic valve replacement technique that can restore long-term survival and preserve quality of life. The main failure mode of the Ross procedure is wall dilatation, potentially leading to valve regurgitation and leakage. Dilatation occurs due to the inability of the pulmonary autograft to adapt to the sudden increase in loading when exposing to aortic pressures. Previous experimental data has shown that a permanent external support wrapped around the artery can prevent the acute dilatation of the arterial wall. However, the textile support leads to stress-shielding phenomena due to the loss of mechanical wall compliance. We present a pragmatic and modular computational framework of arterial growth and remodeling predicting the long-term outcomes of cardiovascular tissue adaptation, with and without textile wrapping. The model integrates mean, systolic and diastolic pressures and assumes the resulting wall stresses to drive the biological remodeling rules. Rather than a single mean pressure or stress deviation from the homeostatic state, we demonstrate that only pulsatile stresses can predict available experimental results. Therefore, we suggest that a biodegradable external support could induce benign remodeling in the Ross procedure. Indeed, a biodegradable textile wrapped around the autograft fulfills the trade-off between prevention of acute dilatation on the one hand and recovery of arterial wall compliance on the other hand. After further validation, the computational framework can set the basis for the development of an actual biodegradable external support for the Ross procedure with optimized polymer mechanical properties and degradation behavior.

Engineering subarachnoid trabeculae with electrospun poly(caprolactone) (PCL) scaffolds to study leptomeningeal metastasis in medulloblastoma

Leptomeningeal metastasis (LM) occurs when cancer cells infiltrate the subarachnoid space (SAS) and metastasize to the fibrous structures that surround the brain and spinal cord. These structures include the leptomeninges (i.e., the pia mater and arachnoid mater), as well as subarachnoid trabeculae, which are collagen-rich fibers that provide mechanical structure for the SAS, support resident cells, and mediate flow of cerebrospinal fluid (CSF). Although there is a strong expectation that the presence of fibers within the SAS influences LM to be a major driver of tumor progression and lethality, exactly how trabecular architecture relates to the process of metastasis in cancer is poorly understood. This lack of understanding is likely due in part to the difficulty of accessing and manipulating this tissue compartment in vivo. Here, we utilized electrospun polycaprolactone (PCL) to produce structures bearing remarkable morphological similarity to native SAS fiber architecture. First, we profiled the native architecture of leptomeningeal and trabecular fibers collected from rhesus macaque monkeys, evaluating both qualitative and quantitative differences in fiber ultrastructure for various regions of the CNS. We then varied electrospinning parameters to produce a small library of PCL scaffolds possessing distinct architectures mimicking the range of fiber properties observed in vivo. For proof of concept, we studied the metastasis-related behaviors of human pediatric medulloblastoma cells cultured in different fiber microenvironments. These studies demonstrated that a more open, porous fiber structure facilitates DAOY cell spread across and infiltration into the meningeal mimic. Our results present a new tissue engineered model of the subarachnoid space and affirm the expectation that fiber architecture plays an important role in mediating metastasis-related behaviors in an in vitro model of pediatric medulloblastoma.

Polymeric reinforcements for cellularized collagen-based vascular wall models: influence of the scaffold architecture on the mechanical and biological properties

A previously developed cellularized collagen-based vascular wall model showed promising results in mimicking the biological properties of a native vessel but lacked appropriate mechanical properties. In this work, we aim to improve this collagen-based model by reinforcing it using a tubular polymeric (reinforcement) scaffold. The polymeric reinforcements were fabricated exploiting commercial poly (ε-caprolactone) (PCL), a polymer already used to fabricate other FDA-approved and commercially available devices serving medical applications, through 1) solution electrospinning (SES), 2) 3D printing (3DP) and 3) melt electrowriting (MEW). The non-reinforced cellularized collagen-based model was used as a reference (COL). The effect of the scaffold's architecture on the resulting mechanical and biological properties of the reinforced collagen-based model were evaluated. SEM imaging showed the differences in scaffolds' architecture (fiber alignment, fiber diameter and pore size) at both the micro- and the macrolevel. The polymeric scaffold led to significantly improved mechanical properties for the reinforced collagen-based model (initial elastic moduli of 382.05 ± 132.01 kPa, 100.59 ± 31.15 kPa and 245.78 ± 33.54 kPa, respectively for SES, 3DP and MEW at day 7 of maturation) compared to the non-reinforced collagen-based model (16.63 ± 5.69 kPa). Moreover, on day 7, the developed collagen gels showed stresses (for strains between 20% and 55%) in the range of [5-15] kPa for COL, [80-350] kPa for SES, [20-70] kPa for 3DP and [100-190] kPa for MEW. In addition to the effect on the resulting mechanical properties, the polymeric tubes' architecture influenced cell behavior, in terms of proliferation and attachment, along with collagen gel compaction and extracellular matrix protein expression. The MEW reinforcement resulted in a collagen gel compaction similar to the COL reference, whereas 3DP and SES led to thinner and longer collagen gels. Overall, it can be concluded that 1) the selected processing technique influences the scaffolds' architecture, which in turn influences the resulting mechanical and biological properties, and 2) the incorporation of a polymeric reinforcement leads to mechanical properties closely matching those of native arteries.

The effect of conductive aligned fibers in an injectable hydrogel on nerve tissue regeneration

Injectable hydrogels are a promising treatment option for nervous system injuries due to the difficulty to replace lost cells and nervous factors but research on injectable conductive hydrogels is limited and these scaffolds have poor electromechanical properties. This study developed a chitosan/beta-glycerophosphate/salt hydrogel and added conductive aligned nanofibers (polycaprolactone/gelatin/single-wall carbon nanotube (SWCNT)) for the first time and inspired by natural nerve tissue to improve their biochemical and biophysical properties. The results showed that the degradation rate of hydrogels is proportional to the regrowth of axons and these hydrogels' mechanical (hydrogels without nanofibers or SWCNTs and hydrogels containing these additions have the same Young's modulus as the brain and spinal cord or peripheral nerves, respectively) and electrical properties, and the interconnective structure of the scaffolds have the ability to support cells.

Biological properties of polycaprolactone and barium titanate composite in biomedical applications

The ceramic-polymer composite materials are widely known for their exceptional mechanical and biological properties. Polycaprolactone (PCL) is a biodegradable polymer material extensively used in various biomedical applications. At the same time, barium titanate (BT), a ceramic material, exhibits piezoelectric properties similar to bone, which is essential for osseointegration. Furthermore, a composite material that combines the benefits of PCL and BT results in an innovative composite material with enhanced properties for biomedical applications. Thus, this review is organised into three sections. Firstly, it aims to provide an overview of the current research on evaluating biological properties, including antibacterial activity, cytotoxicity and osseointegration, of PCL polymeric matrices in its pure form and reinforced structures with ceramics, polymers and natural extracts. The second section investigates the biological properties of BT, both in its pure form and in combination with other supporting materials. Finally, the third section provides a summary of the biological properties of the PCLBT composite material. Furthermore, the existing challenges of PCL, BT and their composites, along with future research directions, have been presented. Therefore, this review will provide a state-of-the-art understanding of the biological properties of PCL and BT composites as potential futuristic materials in biomedical applications.

Influence of mechanochemically fabricated nano-hardystonite reinforcement in polycaprolactone scaffold for potential use in bone tissue engineering: Synthesis and characterization

Bone tissue engineering (BTE) has gained significant attention for the regeneration of bone tissue, particularly for critical-size bone defects. The aim of this research was first to synthesize nanopowders of hardystonite (HT) through ball milling and then to manufacture composite scaffolds for BTE use out of polycaprolactone (PCL) containing 0, 3, 5, and 10 wt% HT by electrospinning method. The crystallite size of the synthesized HT nanopowders was 42.8 nm. including up to 5 wt% HT into PCL scaffolds resulted in significant improvements, such as a reduction in the fiber diameter from 186.457±15.74 to 150.021±21.99 nm, a decrease in porosity volume from 85.2±2.5 to 80.3±3.3 %, an improvement in the mechanical properties (ultimate tensile strength: 5.7±0.2 MPa, elongation: 47.5±3.5 %, tensile modulus: 32.7±0.9 MPa), an improvement in the hydrophilicity, and biodegradability. Notably, PCL/5%HT exhibited the maximum cell viability (194±14 %). Additionally, following a 4-week of submersion in simulated body fluid (SBF), the constructed PCL/HT composite scaffolds showed a remarkable capacity to stimulate the development of hydroxyapatite (HA), which increased significantly for the 5 wt% HT scaffolds. However, at 10 wt% HT, nanopowder agglomeration led to an increase in the fiber diameter and a decrease in the mechanical characteristics. Collectively, the PCL/5%HT composite scaffolds can therefore help with the regeneration of the critical-size bone defects and offer tremendous potential for BTE applications.

Development and Characterization of Electrospun Composites Built on Polycaprolactone and Cerium-Containing Phases

The current study reports on the fabrication of composite scaffolds based on polycaprolactone (PCL) and cerium (Ce)-containing powders, followed by their characterization from compositional, structural, morphological, optical and biological points of view. First, CeO2, Ce-doped calcium phosphates and Ce-substituted bioglass were synthesized by wet-chemistry methods (precipitation/coprecipitation and sol-gel) and subsequently loaded on PCL fibres processed by electrospinning. The powders were proven to be nanometric or micrometric, while the investigation of their phase composition showed that Ce was present as a dopant within the crystal lattice of the obtained calcium phosphates or as crystalline domains inside the glassy matrix. The best bioactivity was attained in the case of Ce-containing bioglass, while the most pronounced antibacterial effect was visible for Ce-doped calcium phosphates calcined at a lower temperature. The scaffolds were composed of either dimensionally homogeneous fibres or mixtures of fibres with a wide size distribution and beads of different shapes. In most cases, the increase in polymer concentration in the precursor solution ensured the achievement of more ordered fibre mats. The immersion in SBF for 28 days triggered an incipient degradation of PCL, evidenced mostly through cracks and gaps. In terms of biological properties, the composite scaffolds displayed a very good biocompatibility when tested with human osteoblast cells, with a superior response for the samples consisting of the polymer and Ce-doped calcium phosphates.

Electrosprayed Core (Cellulose Acetate)-Shell (Polyvinylpyrrolidone) Nanoparticles for Smart Acetaminophen Delivery

Smart drug delivery, through which the drug molecules are delivered according to the requests of human biological rhythms or by maximizing drug therapeutic effects, is highly desired in pharmaceutics. Many biomacromolecules have been exploited for this application in the past few decades, both in industry and laboratories. Biphasic release, with an intentional pulsatile release and a following extended release stage, represents a typical smart drug delivery approach, which aims to provide fast therapeutic action and a long time period of effective blood drug concentration to the patients. In this study, based on the use of a well-known biomacromolecule, i.e., cellulose acetate (CA), as the drug (acetaminophen, ATP)-based sustained release carrier, a modified coaxial electrospraying process was developed to fabricate a new kind of core-shell nanoparticle. The nanoparticles were able to furnish a pulsatile release of ATP due to the shell polyvinylpyrrolidone (PVP). The time cost for a release of 30% was 0.32 h, whereas the core-shell particles were able to provide a 30.84-h sustained release of the 90% loaded ATP. The scanning electron microscope and transmission electron microscope results verified in terms of their round surface morphologies and the obvious core-shell double-chamber structures. ATP presented in both the core and shell sections in an amorphous state owing to its fine compatibility with CA and PVP. The controlled release mechanisms of ATP were suggested. The disclosed biomacromolecule-based process-structure-performance relationship can shed light on how to develop new sorts of advanced nano drug delivery systems.

Electrosprayed Stearic-Acid-Coated Ethylcellulose Microparticles for an Improved Sustained Release of Anticancer Drug

Sustained release is highly desired for "efficacious, safe and convenient" drug delivery, particularly for those anticancer drug molecules with toxicity. In this study, a modified coaxial electrospraying process was developed to coat a hydrophobic lipid, i.e., stearic acid (SA), on composites composed of the anticancer drug tamoxifen citrate (TC) and insoluble polymeric matrix ethylcellulose (EC). Compared with the electrosprayed TC-EC composite microparticles M1, the electrosprayed SA-coated hybrid microparticles M2 were able to provide an improved TC sustained-release profile. The 30% and 90% loaded drug sustained-release time periods were extended to 3.21 h and 19.43 h for M2, respectively, which were significantly longer than those provided by M1 (0.88 h and 9.98 h, respectively). The morphology, inner structure, physical state, and compatibility of the components of the particles M1 and M2 were disclosed through SEM, TEM, XRD, and FTIR. Based on the analyses, the drug sustained-release mechanism of multiple factors co-acting for microparticles M2 is suggested, which include the reasonable selections and organizations of lipid and polymeric excipient, the blank SA shell drug loading, the regularly round shape, and also the high density. The reported protocols pioneered a brand-new manner for developing sustained drug delivery hybrids through a combination of insoluble cellulose gels and lipid using modified coaxial electrospraying.

Effects of electrospun fibers containing ascorbic acid on oxidative stress reduction for cardiac tissue engineering

Tissue engineering provides promise for regeneration of cardiac tissue following myocardial infarction. However, the harsh microenvironment of the infarct hampers the efficacy of regenerative therapies. Ischemia-reperfusion injury dramatically increases the levels of reactive oxygen species (ROS) within the infarcted area, causing a cascade of further cellular injury. Implantable tissue engineered grafts can target this oxidative stress by delivering pharmaceutical compounds directly into the diseased tissue. Herein, we successfully fabricated electrospun polycaprolactone (PCL) fibers containing varying concentrations of ascorbic acid, a potent antioxidant well known for its ROS-scavenging capabilities. The antioxidant scaffolds displayed significantly improved scavenging of DPPH radicals, superoxide anions and hydroxyl radicals, in a dose dependent manner. Mechanical properties testing indicated that incorporation of ascorbic acid enhanced the strength and Young's modulus of the material, correlating with a moderate but non-significant increase in the crystallinity. Moreover, the scaffolds supported adhesion and maintained survival of human umbilical vein endothelial cells in vitro, indicating good cytocompatibility. These results provide motivation for the use of ascorbic acid-containing fibrous scaffolds to regulate the highly oxidative microenvironment following myocardial infarction.

Crosslinking of a polycaprolactone/tourmaline scaffold by sodium stearate with improved mechanical strength and bioactivity

Although polycaprolactone (PCL) matrix composites have been extensively studied, the weak interface with nanofillers limits their further applications in bone tissue engineering. Herein, this study has designed a porous bone scaffold model using the triply periodic minimal surfaces (TPMS), and the optimal porosity was determined by comparing the mechanical properties. A sodium stearate-modified PCL/tourmaline (PCL/TM) composite scaffold with a strong interfacial effect was prepared by selective laser sintering technology. Wherein, sodium stearate acts as a bridge to improve the interaction between TM and PCL interface, while promoting its uniform dispersion. The results showed that the PCL/3% modified TM specimens exhibit the optimum mechanical properties, and their ultimate tensile and compressive strength increases by 21.8% and 32.1%, respectively, compared with pure PCL. The factors of mechanical enhancement of composite scaffolds can be elaborated from the construction of interface bridges. On the one hand, the carboxyl group at one end of sodium stearate will interact with the hydroxyl group on the surface of TM to enhance interfacial adsorption by forming ionic bonds and hydrogen bonds. On the other hand, the hydrophobic long chain at the other end of sodium stearate is universally compatible with hydrophobic PCL, thereby improving the dispersion of TM. These characteristics make the PCL/TM composite scaffold a valuable reference for its application in bone tissue engineering.

Electrospun Scaffolds Enriched with Nanoparticle-Associated DNA: General Properties, DNA Release and Cell Transfection

Biomaterial-mediated, spatially localized gene delivery is important for the development of cell-populated scaffolds used in tissue engineering. Cells adhering to or penetrating into such a scaffold are to be transfected with a preloaded gene that induces the production of secreted proteins or cell reprogramming. In the present study, we produced silica nanoparticles-associated pDNA and electrospun scaffolds loaded with such nanoparticles, and studied the release of pDNA from scaffolds and cell-to-scaffold interactions in terms of cell viability and pDNA transfection efficacy. The pDNA-coated nanoparticles were characterized with dynamic light scattering and transmission electron microscopy. Particle sizes ranging from 56 to 78 nm were indicative of their potential for cell transfection. The scaffolds were characterized using scanning electron microscopy, X-ray photoelectron spectroscopy, stress-loading tests and interaction with HEK293T cells. It was found that the properties of materials and the pDNA released vary, depending on the scaffold's composition. The scaffolds loaded with pDNA-nanoparticles do not have a pronounced cytotoxic effect, and can be recommended for cell transfection. It was found that (pDNA-NPs) + PEI9-loaded scaffold demonstrates good potential for cell transfection. Thus, electrospun scaffolds suitable for the transfection of inhabiting cells are eligible for use in tissue engineering.

Nanostructured Electrospun Fibers with Self-Assembled Cyclo-L-Tryptophan-L-Tyrosine Dipeptide as Piezoelectric Materials and Optical Second Harmonic Generators

The potential use of nanostructured dipeptide self-assemblies in materials science for energy harvesting devices is a highly sought-after area of research. Specifically, aromatic cyclo-dipeptides containing tryptophan have garnered attention due to their wide-bandgap semiconductor properties, high mechanical rigidity, photoluminescence, and nonlinear optical behavior. In this study, we present the development of a hybrid system comprising biopolymer electrospun fibers incorporated with the chiral cyclo-dipeptide L-Tryptophan-L-Tyrosine. The resulting nanofibers are wide-bandgap semiconductors (bandgap energy 4.0 eV) consisting of self-assembled nanotubes embedded within a polymer matrix, exhibiting intense blue photoluminescence. Moreover, the cyclo-dipeptide L-Tryptophan-L-Tyrosine incorporated into polycaprolactone nanofibers displays a strong effective second harmonic generation signal of 0.36 pm/V and shows notable piezoelectric properties with a high effective coefficient of 22 pCN-1, a piezoelectric voltage coefficient of geff=1.2 VmN-1 and a peak power density delivered by the nanofiber mat of 0.16μWcm-2. These hybrid systems hold great promise for applications in the field of nanoenergy harvesting and nanophotonics.

Effect of Degradation in Small Intestinal Fluids on Mechanical Properties of Polycaprolactone and Poly-l-lactide-co-caprolactone

Polycaprolactone and poly-l-lactide-co-caprolactone are promising degradable biomaterials for many medical applications. Their mechanical properties, especially a low elastic modulus, make them particularly interesting for implantable devices and scaffolds that target soft tissues like the small intestine. However, the specific environment and mechanical loading in the intestinal lumen pose harsh boundary conditions on the design of these devices, and little is known about the degradation of those mechanical properties in small intestinal fluids. Here, we perform tensile tests on injection molded samples of both polymers during in vitro degradation of up to 70 days in human intestinal fluids. We report on yield stress, Young's modulus, elongation at break and viscoelastic parameters describing both materials at regular time steps during the degradation. These characteristics are bench-marked against degradation studies of the same materials in other media. As a result, we offer time dependent mechanical properties that can be readily used for the development of medical devices that operate in the small intestine.

Biomimetic in situ tracheal microvascularization for segmental tracheal reconstruction in one-step

Formation of functional and perfusable vascular network is critical to ensure the long-term survival and functionality of the engineered tissue tracheae after transplantation. However, the greatest challenge in tracheal-replacement therapy is the promotion of tissue regeneration by rapid graft vascularization. Traditional prevascularization methods for tracheal grafts typically utilize omentum or muscle flap wrapping, which requires a second operation; vascularized segment tracheal orthotopic transplantation in one step remains difficult. This study proposes a method to construct a tissue-engineered tracheal graft, which directly forms the microvascular network after orthotopic transplantation in vivo. The focus of this study was the preparation of a hybrid tracheal graft that is non-immunogenic, has good biomechanical properties, supports cell proliferation, and quickly vascularizes. The results showed that vacuum-assisted decellularized trachea-polycaprolactone hybrid scaffold could match most of the above requirements as closely as possible. Furthermore, endothelial progenitor cells (EPCs) were extracted and used as vascularized seed cells and seeded on the surfaces of hybrid grafts before and during the tracheal orthotopic transplantation. The results showed that the microvascularized tracheal grafts formed maintained the survival of the recipient, showing a satisfactory therapeutic outcome. This is the first study to utilize EPCs for microvascular construction of long-segment trachea in one-step; the approach represents a promising method for microvascular tracheal reconstruction.

Calcium Trimetaphosphate-Loaded Electrospun Poly(Ester Urea) Nanofibers for Periodontal Tissue Engineering

The objective of this research was to create and appraise biodegradable polymer-based nanofibers containing distinct concentrations of calcium trimetaphosphate (Ca-TMP) for periodontal tissue engineering. Poly(ester urea) (PEU) (5% w/v) solutions containing Ca-TMP (15%, 30%, 45% w/w) were electrospun into fibrous scaffolds. The fibers were evaluated using SEM, EDS, TGA, FTIR, XRD, and mechanical tests. Degradation rate, swelling ratio, and calcium release were also evaluated. Cell/Ca-TMP and cell/scaffold interaction were assessed using stem cells from human exfoliated deciduous teeth (SHEDs) for cell viability, adhesion, and alkaline phosphatase (ALP) activity. Analysis of variance (ANOVA) and post-hoc tests were used (α = 0.05). The PEU and PEU/Ca-TMP-based membranes presented fiber diameters at 469 nm and 414-672 nm, respectively. Chemical characterization attested to the Ca-TMP incorporation into the fibers. Adding Ca-TMP led to higher degradation stability and lower dimensional variation than the pure PEU fibers; however, similar mechanical characteristics were observed. Minimal calcium was released after 21 days of incubation in a lipase-enriched solution. Ca-TMP extracts enhanced cell viability and ALP activity, although no differences were found between the scaffold groups. Overall, Ca-TMP was effectively incorporated into the PEU fibers without compromising the morphological properties but did not promote significant cell function.

The Reliability of PCL/Anti-VEGF Electrospun Scaffolds to Support Limbal Stem Cells for Corneal Repair

Since only few reported studies propose anti-vascular endothelial growth factor (anti-VEGF) delivery through electrospun scaffolds, this study greatly contributes to the potential prevention of patient's vision loss, as it explores electrospun polycaprolactone (PCL) coated with anti-VEGF for the blockage of abnormal cornea vascularization. In terms of physicochemical properties, the biological component increased the PCL scaffold fiber diameter (by ~24%) and pore area (by ~82%), while ut slightly reduced its total porosity as the anti-VEGF solution filled the voids of the microfibrous structure. The addition of the anti-VEGF increased the scaffold stiffness almost three-fold at both strains of 5 and 10%, as well as its biodegradation rate (~36% after 60 days) with a sustained release profile after Day 4 of phosphate buffered saline incubation. In terms of scaffold application function, the PCL/Anti-VEGF scaffold proved to be more favorable for the adhesion of cultured limbal stem cells (LSCs); this was confirmed by the SEM images, where the cells showed flat and elongated conformations. Further support of the LSC growth and proliferation was confirmed by the identified p63 and CK3 markers after cell staining. These results demonstrate the advantageous effect of the surface-adsorbed anti-VEGF to stop vision loss and help damaged corneal tissue repair.

In Vitro and In Vivo Evaluation of a Polycaprolactone (PCL)/Polylactic-Co-Glycolic Acid (PLGA) (80:20) Scaffold for Improved Treatment of Chondral (Cartilage) Injuries

Articular cartilage is a specialized tissue that provides a smooth surface for joint movement and load transmission. Unfortunately, it has limited regenerative capacity. Tissue engineering, combining different cell types, scaffolds, growth factors, and physical stimulation has become an alternative for repairing and regenerating articular cartilage. Dental Follicle Mesenchymal Stem Cells (DFMSCs) are attractive candidates for cartilage tissue engineering because of their ability to differentiate into chondrocytes, on the other hand, the polymers blend like Polycaprolactone (PCL) and Poly Lactic-co-Glycolic Acid (PLGA) have shown promise given their mechanical properties and biocompatibility. In this work, the physicochemical properties of polymer blends were evaluated by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM) and were positive for both techniques. The DFMSCs demonstrated stemness by flow cytometry. The scaffold showed to be a non-toxic effect when we evaluated it with Alamar blue, and the samples were analyzed using SEM and phalloidin staining to evaluate cell adhesion to the scaffold. The synthesis of glycosaminoglycans was positive on the construct in vitro. Finally, the PCL/PLGA scaffold showed a better repair capacity than two commercial compounds, when tested in a chondral defect rat model. These results suggest that the PCL/PLGA (80:20) scaffold may be suitable for applications in the tissue engineering of articular hyaline cartilage.

Biodegradation Behavior Control for Shape Memory Polyester Poly(Glycerol-Dodecanoate): An In Vivo and In Vitro Study

Poly(glycerol-dodecanoate) (PGD) has garnered increasing attention in biomedical engineering for its degradability, shape memory, and rubber-like mechanical properties. Adjustable degradation is important for biodegradable implants and is affected by various aspects, including material properties, mechanical environments, temperature, pH, and enzyme catalysis. The crosslinking and chain length characteristics of poly(lactic acid) and poly(caprolactone) have been widely used to adjust the in vivo degradation rate. The PGD degradation rate is affected by its crosslink density in in vitro hydrolysis; however, there is no difference in vivo. We believe that this phenomenon is caused by the differences in enzymatic conditions in vitro and in vivo. In this study, it is found that the degradation products of PGD with different molar ratios of hydroxyl and carboxyl (MR_H/C) exhibit varied pH values, affecting the enzyme activity and thus achieving different degradation rates. The in vivo degradation of PGD is characterized by surface erosion, and its mass decreases linearly with degradation duration. The degradation duration of PGD is linearly extrapolated from 9-18 weeks when MR_H/C is in the range of 2.00-0.75, providing a protocol for adjusting the degradation durations of subsequent implants made by PGD.

In Vivo Stable Allogenic Cartilage Regeneration in a Goat Model Based on Immunoisolation Strategy Using Electrospun Semipermeable Membranes

Tissue engineering is a promising strategy for cartilage defect repair. However, autologous cartilage regeneration is limited by additional trauma to the donor site and a long in vitro culture period. Alternatively, allogenic cartilage regeneration has attracted attention because of the unique advantages of an abundant donor source and immediate supply, but it will cause immune rejection responses (IRRs), especially in immunocompetent large animals. Therefore, a universal technique needs to be established to overcome IRRs for allogenic cartilage regeneration in large animals. In the current study, a hybrid synthetic-natural electrospun thermoplastic polyurethane/gelatin (TPU/GT) semipermeable membrane to explore the feasibility of stable allogenic cartilage regeneration by an immunoisolation strategy is developed. In vitro results demonstrated that the rationally designed electrospun TPU/GT membranes has ideal biocompatibility, semipermeability, and an immunoisolation function. In vivo results further showed that the semipermeable membrane (SPM) efficiently blocked immune cell attack, decreased immune factor production, and cell apoptosis of the regenerated allogenic cartilage. Importantly, TPU/GT-encapsulated cartilage-sheet constructs achieved stable allogeneic cartilage regeneration in a goat model. The current study provides a novel strategy for allogenic cartilage regeneration and supplies a new cartilage donor source to repair various cartilage defects.

Electrospun Nanofibers Loaded with Plantago major L. Extract for Potential Use in Cutaneous Wound Healing

Plantago major L. is a plant available worldwide that has been traditionally used for several medical applications due to its wound healing, anti-inflammatory, and antimicrobial properties. This work aimed to develop and evaluate a nanostructured PCL electrospun dressing with P. major extract encapsulated in nanofibers for applications in wound healing. The extract from leaves was obtained by extraction in a mixture of water:ethanol = 1:1. The freeze-dried extract presented a minimum inhibitory concentration (MIC) for Staphylococcus Aureus susceptible and resistant to methicillin of 5.3 mg/mL, a high antioxidant capacity, but a low content of total flavonoids. Electrospun mats without defects were successfully produced using two P. major extract concentrations based on the MIC value. The extract incorporation in PCL nanofibers was confirmed using FTIR and contact angle measurements. The PCL/P. major extract was evaluated using DSC and TGA demonstrating that the incorporation of the extract decreases the thermal stability of the mats as well as the degree of crystallinity of PCL-based fibers. The P. major extract incorporation on electrospun mats produced a significant swelling degree (more than 400%) and increased the capacity of adsorbing wound exudates and moisture, important characteristics for skin healing. The extract-controlled release evaluated using in vitro study in PBS (pH, 7.4) shows that the P. major extract delivery from the mats occurs in the first 24 h, demonstrating their potential capacity to be used in wound healing.