Precipitation casting of polycaprolactone for applications in tissue engineering and drug delivery

Investigation of the biodegradation kinetics and associated mechanical properties of 3D-printed polycaprolactone during long-term preclinical testing

Polycaprolactone (PCL) is a bioresorbable polymer increasingly utilized for customized tissue reconstruction as it is readily 3D printed. A critical design requirement for PCL devices is determining the in vivo bioresorption rate and the resulting change in device mechanics suited for target tissue repair applications. The primary challenge with meeting this requirement involves accurate prediction of degradation in the target tissues. PCL undergoes bulk hydrolytic degradation following first order kinetics until an 80-90 % drop in the starting number average molecular weight (Mn) after 2-3 years in vivo. However, initial polymer architecture, composite incorporation, manufacturing modality, device architecture, and target tissue can impact degradation. In vitro models do not fully capture device degradation, and the limited long-term (2-3 year) models primarily utilize subcutaneous implants. In this study, we investigate the degradation rate of 3D-printed airway support devices (ASDs) comprised of PCL and 4 % hydroxyapatite (HA) when implanted on Yucatan porcine tracheas for two years. After one year of degradation, we report a mass loss of less than 1 % and Mn reduction of 25 %. After two years, mass and Mn decreased by 10 % and 50 % respectively. These changes are accompanied by an increase in elastic modulus from 146.7 ± 5.2 MPa for freshly printed ASDs to 291.7 ± 16.0 MPa after one year and 362.5 ± 102.4 MPa after two years. Additionally, there was a decrease in yield strain, and increase in yield stress from implantation to 1-year (p < 0.001). Plastic strain completely diminished by two years, resulting in brittle failure at a yield stress of 12.5 MPa. The significantly lower rate of hydrolysis coupled with hydrolytic embrittlement indicates alternate degradation kinetics compared to subcutaneous models. Fitting a new model for degradation and predicting elastic and damage properties of this new degradation paradigm provide significant advancements for 3D-printed device design in clinical repair applications.

Melt Electrowriting of Polyhydroxyalkanoates for Enzymatically Degradable Scaffolds

Melt electrowriting (MEW) enables precise scaffold fabrication for biomedical applications. With a limited number of processable materials with short and tunable degradation times, polyhydroxyalkanoates (PHAs) present an interesting option. Here, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and a blend of PHBV and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (PHBV+P34HB) are successfully melt electrowritten into scaffolds with various architectures. PHBV+P34HB exhibits greater thermal stability, making it a superior printing material compared to PHBV in MEW. The PHBV+P34HB scaffolds subjected to enzymatic degradation show tunable degradation times, governed by enzyme dilution, incubation time, and scaffold surface area. PHBV+P34HB scaffolds seeded with human dermal fibroblasts (HDFs), demonstrate enhanced cell adherence, proliferation, and spreading. The HDFs, when exposed to the enzyme solutions and enzymatic degradation residues, show good viability and proliferation rates. Additionally, HDFs grown on enzymatically pre-incubated scaffolds do not show any difference in behavior compared those grown on control scaffolds. It is concluded that PHAs, as biobased materials with enzymatically tunable degradability rates, are an important addition to the already limited set of materials available for MEW technology.

Inulin as a Biopolymer; Chemical Structure, Anticancer Effects, Nutraceutical Potential and Industrial Applications: A Comprehensive Review

Inulin is a versatile biopolymer that is non-digestible in the upper alimentary tract and acts as a bifidogenic prebiotic which selectively promotes gut health and modulates gut-organ axes through short-chain fatty acids and possibly yet-to-be-known interactions. Inulin usage as a fiber ingredient in food has been approved by the FDA since June 2018 and it is predicted that the universal inulin market demand will skyrocket in the near future because of its novel applications in health and diseases. This comprehensive review outlines the known applications of inulin in various disciplines ranging from medicine to industry, covering its benefits in gut health and diseases, metabolism, drug delivery, therapeutic pharmacology, nutrition, and the prebiotics industry. Furthermore, this review acknowledges the attention of researchers to knowledge gaps regarding the usages of inulin as a key modulator in the gut-organ axes.

Development and pharmacological evaluation of liposomes and nanocapsules containing paroxetine hydrochloride

Depression is one of the most common psychiatric disorders. Nanotechnology has emerged to optimize the pharmacological response. Therefore, the aim of this work was to develop and characterize liposomes and nanocapsules containing paroxetine hydrochloride and evaluate their antidepressant-like effect using the open field and tail suspension tests in mice. Liposomes and nanocapsules were prepared using the reverse-phase evaporation and nanoprecipitation methods, respectively. The particle size of the formulation ranged from 121.81 to 310.73 nm, the polydispersity index from 0.096 to 0.303, the zeta potential from -11.94 to -34.50 mV, the pH from 5.31 to 7.38, the drug content from 80.82 to 94.36 %, and the association efficiency was 98 %. Paroxetine hydrochloride showed slower release when associated with liposomes (43.82 %) compared to nanocapsules (95.59 %) after 10 h. In Vero cells, in vitro toxicity showed a concentration-dependent effect for paroxetine hydrochloride nanostructures. Both nanostructures decreased the immobility time in the TST at 2.5 mg/kg without affecting the number of crossings in the open field test, suggesting the antidepressant-like effect of paroxetine. In addition, the nanocapsules decreased the number of groomings, reinforcing the anxiolytic effect of this drug. These results suggest that the nanostructures were effective in preserving the antidepressant-like effect of paroxetine hydrochloride even at low doses.

Absorbable implants in sport medicine and arthroscopic surgery: A narrative review of recent development

Over the past two decades, advances in arthroscopic and minimally invasive surgical techniques have led to significant growth in sports medicine surgery. Implants such as suture anchors, interference screws, and endo-buttons are commonly used in these procedures. However, traditional implants made of metal or inert materials are not absorbable, leading to complications that affect treatment outcomes. To address this issue, absorbable materials with excellent mechanical properties, good biocompatibility, and controlled degradation rates have been developed and applied in clinical practice. These materials include absorbable polymers, absorbable bioceramics, and absorbable metals. In this paper, we will provide a comprehensive summary of these absorbable materials from the perspective of clinicians, and discuss their clinical applications and related research in sport medicine.

Combining Step-Growth and Chain-Growth Polymerizations in One Pot: Light-Induced Fabrication of Conductive Nanoporous PEDOT-PCL Scaffold

A novel method based on light-induced fabrication of a poly (3,4-ethylenedioxythiophene)-polycaprolactone (PEDOT-PCL) scaffold using phenacyl bromide (PAB) as a single-component photoinitiator is presented. HBr released from the step-growth polymerization of EDOT is utilized as an in situ catalyst for the chain-growth polymerization of ε-caprolactone. Detailed investigations disclose the formation of a self-assembled nanoporous electroconductive scaffold (1.2 mS cm-1 ). Fluorescence emission spectra of the fabricated scaffold exhibit a mixed solvatochromic behavior, indicating specific interactions between the self-assembled scaffold and solvents with varying polarities, as evidenced by transmission electron microscopy (TEM). Moreover, the same light-induced technique can also be applied for bulk photopolymerization showcasing the versatility and wide-ranging scope of the originated method. In brief, this study introduces a novel approach for light-induced polymerization reactions that is merging step-growth and chain-growth mechanisms. This innovative approach is promising to facilitate in situ polymerization of monomers possessing diverse functionalities.

In Vitro Investigation of Gelatin/Polycaprolactone Nanofibers in Modulating Human Gingival Mesenchymal Stromal Cells

The aesthetic constancy and functional stability of periodontium largely depend on the presence of healthy mucogingival tissue. Soft tissue management is crucial to the success of periodontal surgery. Recently, synthetic substitute materials have been proposed to be used for soft tissue augmentation, but the tissue compatibility of these materials needs to be further investigated. This study aims to assess the in vitro responses of human gingival mesenchymal stromal cells (hG-MSCs) cultured on a Gelatin/Polycaprolactone prototype (GPP) and volume-stable collagen matrix (VSCM). hG-MSCs were cultured onto the GPP, VSCM, or plastic for 3, 7, and 14 days. The proliferation and/or viability were measured by cell counting kit-8 assay and resazurin-based toxicity assay. Cell morphology and adhesion were evaluated by microscopy. The gene expression of collagen type I, alpha1 (COL1A1), α-smooth muscle actin (α-SMA), fibroblast growth factor (FGF-2), vascular endothelial growth factor A (VEGF-A), transforming growth factor beta-1 (TGF-β1), focal adhesion kinase (FAK), integrin beta-1 (ITG-β1), and interleukin 8 (IL-8) was investigated by RT-qPCR. The levels of VEGF-A, TGF-β1, and IL-8 proteins in conditioned media were tested by ELISA. GPP improved both cell proliferation and viability compared to VSCM. The cells grown on GPP exhibited a distinct morphology and attachment performance. COL1A1, α-SMA, VEGF-A, FGF-2, and FAK were positively modulated in hG-MSCs on GPP at different investigation times. GPP increased the gene expression of TGF-β1 but had no effect on protein production. The level of ITG-β1 had no significant changes in cells seeded on GPP at 7 days. At 3 days, notable differences in VEGF-A, TGF-β1, and α-SMA expression levels were observed between cells seeded on GPP and those on VSCM. Meanwhile, GPP showed higher COL1A1 expression compared to VSCM after 14 days, whereas VSCM demonstrated a more significant upregulation in the production of IL-8. Taken together, our data suggest that GPP electrospun nanofibers have great potential as substitutes for soft tissue regeneration in successful periodontal surgery.

An Overview of Scaffolds and Biomaterials for Skin Expansion and Soft Tissue Regeneration: Insights on Zinc and Magnesium as New Potential Key Elements

The utilization of materials in medical implants, serving as substitutes for non-functional biological structures, supporting damaged tissues, or reinforcing active organs, holds significant importance in modern healthcare, positively impacting the quality of life for millions of individuals worldwide. However, certain implants may only be required temporarily to aid in the healing process of diseased or injured tissues and tissue expansion. Biodegradable metals, including zinc (Zn), magnesium (Mg), iron, and others, present a new paradigm in the realm of implant materials. Ongoing research focuses on developing optimized materials that meet medical standards, encompassing controllable corrosion rates, sustained mechanical stability, and favorable biocompatibility. Achieving these objectives involves refining alloy compositions and tailoring processing techniques to carefully control microstructures and mechanical properties. Among the materials under investigation, Mg- and Zn-based biodegradable materials and their alloys demonstrate the ability to provide necessary support during tissue regeneration while gradually degrading over time. Furthermore, as essential elements in the human body, Mg and Zn offer additional benefits, including promoting wound healing, facilitating cell growth, and participating in gene generation while interacting with various vital biological functions. This review provides an overview of the physiological function and significance for human health of Mg and Zn and their usage as implants in tissue regeneration using tissue scaffolds. The scaffold qualities, such as biodegradation, mechanical characteristics, and biocompatibility, are also discussed.

Physical and biological changes of copper oxide and hydroxyapatite filled in polycaprolactone scaffolds: Cellular growth behavior and antibacterial activity

Burns have placed a devastating burden on public health because of leading to an increased risk of infection. Therefore, the development of an effective antibacterial dressing for wound healing is essential. The present work is mainly based on the fabrication of biodegradable polycaprolactone (PCL) films through a simple and cheap process of polymer casting using a novel combination of hydroxyapatite (HAP), cuprous oxide (Cu2O) NPs and graphene oxide (GO) nanosheets which have a great effect in preventing colonization and to modify the wound dreasing. The compositions played a key role in decreasing the contact angle of PCL from 47.02° to 11.53°. Further, the cell viability exhibited a viable cell ratio of 81.2% after 3 days of culturing. Moreover, the highest antibacterial activity was obtained from the film of Cu2O@PCl and showed high impact results in antibacterial behavior.

A bioactive microparticle-loaded osteogenically enhanced bioprinted scaffold that permits sustained release of BMP-2

Extrusion-based bioprinting technology is widely used for tissue regeneration and reconstruction. However, the method that uses only hydrogel as the bioink base material exhibits limited biofunctional properties and needs improvement to achieve the desired tissue regeneration. In this study, we present a three-dimensionally printed bioactive microparticle-loaded scaffold for use in bone regeneration applications. The unique structure of the microparticles provided sustained release of growth factor for > 4 weeks without the use of toxic or harmful substances. Before and after printing, the optimal particle ratio in the bioink for cell viability demonstrated a survival rate of ≥ 85% over 7 days. Notably, osteogenic differentiation and mineralization-mediated by human periosteum-derived cells in scaffolds with bioactive microparticles-increased over a 2-week interval. Here, we present an alternative bioprinting strategy that uses the sustained release of bioactive microparticles to improve biofunctional properties in a manner that is acceptable for clinical bone regeneration applications.

Evaluation of a Bioabsorbable Scaffold and Interlocked Nail System for Segmental Bone Defect

In the current study, we designed and manufactured a scaffold and fixation system for the reconstruction of long-bone segmental defects in a rabbit tibia model. We used biocompatible and biodegradable materials, polycaprolactone (PCL) and PCL soaked with sodium alginate (PCL-Alg) to manufacture the scaffold, interlocking nail and screws using a phase separation casing method. Degradation and mechanical tests on the PCL and PCL-Alg scaffolds indicated that both were suitable for faster degradation and early weight-bearing capacity. PCL scaffold surface porosity facilitated the infiltration of alginate hydrogel through the scaffold. Cell viability results showed that the number of cells increased on Day 7 and decreased marginally by Day 14. For accurate placement of the scaffold and fixation system, a surgical jig was designed and 3D-printed using biocompatible resin in a stereolithography (SLA) 3D printer, then cured with UV light for increased strength. Our cadaver tests using New Zealand White rabbit confirmed our novel jigs’ potential for accurate placement of the bone scaffold, intramedullary nail and the alignment of the fixation screws in future reconstructive surgeries on rabbit long-bone segmental defects. Additionally, the cadaver tests confirmed that our designed nails and screws were strong enough to carry the surgical insertion force. Therefore, our designed prototype has the potential for further clinical translational study using the rabbit tibia model.

Polymeric Gel Scaffolds and Biomimetic Environments for Wound Healing

Infected wounds that do not heal are a worldwide problem that is worsening, with more people dying and more money being spent on care. For any disease to be managed effectively, its root cause must be addressed. Effective wound care becomes a bigger problem when various traditional wound healing methods and products may not only fail to promote good healing. Still, it may also hinder the healing process, causing wounds to stay open longer. Progress in tissue regeneration has led to developing three-dimensional scaffolds (3D) or constructs that can be leveraged to facilitate cell growth and regeneration while preventing infection and accelerating wound healing. Tissue regeneration uses natural and fabricated biomaterials that encourage the growth of tissues or organs. Even though the clinical need is urgent, the demand for polymer-based therapeutic techniques for skin tissue abnormalities has grown quickly. Hydrogel scaffolds have become one of the most imperative 3D cross-linked scaffolds for tissue regeneration because they can hold water perfectly and are porous, biocompatible, biodegradable, and biomimetic. For damaged organs or tissues to heal well, the porosity topography of the natural extracellular matrix (ECM) should be imitated. This review details the scaffolds that heal wounds and helps skin tissue to develop. After a brief overview of the bioactive and drug-loaded polymeric hydrogels, the discussion moves on to how the scaffolds are made and what they are made of. It highlights the present uses of in vitro and in-vivo employed biomimetic scaffolds. The prospects of how well bioactiveloaded hydrogels heal wounds and how nanotechnology assists in healing and regeneration have been discussed.

Composite Fibers Based on Polycaprolactone and Calcium Magnesium Silicate Powders for Tissue Engineering Applications

The present work reports the synthesis and characterization of polycaprolactone fibers loaded with particulate calcium magnesium silicates, to form composite materials with bioresorbable and bioactive properties. The inorganic powders were achieved through a sol-gel method, starting from the compositions of diopside, akermanite, and merwinite, three mineral phases with suitable features for the field of hard tissue engineering. The fibrous composites were fabricated by electrospinning polymeric solutions with a content of 16% polycaprolactone and 5 or 10% inorganic powder. The physico-chemical evaluation from compositional and morphological points of view was followed by the biological assessment of powder bioactivity and scaffold biocompatibility. SEM investigation highlighted a significant reduction in fiber diameter, from around 3 μm to less than 100 nm after the loading stage, while EDX and FTIR spectra confirmed the existence of embedded mineral entities. The silicate phases were found be highly bioactive after 4 weeks of immersion in SBF, enriching the potential of the polymeric host that provides only biocompatibility and bioresorbability. Moreover, the cellular tests indicated a slight decrease in cell viability over the short-term, a compromise that can be accepted if the overall benefits of such multifunctional composites are considered.

Scalable and Room-Temperature Ring-Opening Polymerization of ε-Caprolactone Catalyzed by Active Lithium Tetramethylene-Tethered Bis[N-(N'-butylimidazol-2-ylidene)] N-Heterocyclic Carbene as a Lewis Acid Organocatalyst

The Lewis acid organocatalytic system of lithium tetramethylene-tethered bis[N-(N'-butylimidazol-2-ylidene)] N-heterocyclic carbene (1,4-bisNHC) including lithium benzyloxide and benzyl alcohol has been successfully utilized in the ring-opening polymerization (ROP) of ε-caprolactone (CL) for the first time. The catalytic performance of this organic catalyst in the synthesis of high-molecular-weight polymers was investigated via bulk polymerization using different combinations of tetramethylene-tethered bis[N-(N'-butylimidazolium)] hexafluorophosphate (1,4-bis[Bim][PF₆]), benzyl alcohol (BnOH), and n-butyl lithium (nBuLi) ([1,4-bis[Bim][PF₆]]/[BnOH]/[nBuLi]) with the molar ratios of 0:2:2, 1:1:3, 1:2:3, and 1:2:4. The results showed that the molar ratio of 1:2:3 efficiently and rapidly initiated the bulk ROP of CL at room temperature with a high molar ratio of CL to 1,4-bis[Bim][PF₆] of 3000/1 and produced the highest number of average-molecular-weight (M_n) poly(ε-caprolactone) (103,057 g mol^-1) with the dispersity (D̵) and %conversion of 1.73 and 98% in a short period of time (152 s). From comparative studies, the relative polymerization rates of the bulk ROP of CL with different [1,4-bis[Bim][PF₆]]/[BnOH]/[nBuLi] molar ratios was determined in the following order: 1:2:4 > 1:1:3 > 1:2:3 > 0:2:2. For mechanistic investigation, the bulk ROP mechanism of CL with our organic catalyst was proposed through the intramolecular bis-lithium-carbene interaction pathway for 1,4-bisNHC_1,1,3, 1,4-bisNHC_1,2,3, and 1,4-bisNHC_1,2,4 systems.

A standardized assessment of moldability parameters of thermoplastic materials used in orthotic manufacturing

Objective

To establish parameters for standardized assessment of the moldability of thermoplastic materials used in orthotic manufacturing and to develop tests for quantification of moldability parameters by simulating the demands of clinical practice, in order to enable accurate and controlled analysis of material properties.

Primary outcome measurements

Two commercially available materials were submitted to tests for standardized measurement of moldability. Results were correlated with manufacturer information. Moldability assessment was based on two parameters (conformation and fit), expressed as percentages.

Results

Tests, standardized molding procedures and measurements were described. Quantitative data (conformation and fit expressed in percentages) were derived from a pilot study comparing Aquaplast-T™ and Ezeform™. Findings of that study revealed that Aquaplast-T™ is more moldable than Ezeform™ and support technical information provided by the manufacturer.

Conclusions

The assessment method described enabled objective and repeatable measurement of the moldability of materials used in orthotic manufacturing and represent a significant advancement in comparative analysis of materials, with potential positive impacts on therapeutic procedures and clinical decision-making. Tests developed in this study can be used to quantify data provided by manufacturers in order to allow their use by researchers and professionals in rehabilitation.

Application of biomaterials and tissue engineering in bladder regeneration

The primary functions of the bladder are storing urine under low and stable pressure and micturition. Various forms of trauma, tumors, and iatrogenic injuries can cause the loss of or reduce bladder function or capacity. If such damage is not treated in time, it will eventually lead to kidney damage and can even be life-threatening in severe cases. The emergence of tissue engineering technology has led to the development of more possibilities for bladder repair and reconstruction, in which the selection of scaffolds is crucial. In recent years, a growing number of tissue-engineered bladder scaffolds have been constructed. Therefore, this paper will discuss the development of tissue-engineered bladder scaffolds and will further analyze the limitations of and challenges encountered in bladder reconstruction.

Natural Fiber-Reinforced Polycaprolactone Green and Hybrid Biocomposites for Various Advanced Applications

Recent developments within the topic of biomaterials has taken hold of researchers due to the mounting concern of current environmental pollution as well as scarcity resources. Amongst all compatible biomaterials, polycaprolactone (PCL) is deemed to be a great potential biomaterial, especially to the tissue engineering sector, due to its advantages, including its biocompatibility and low bioactivity exhibition. The commercialization of PCL is deemed as infant technology despite of all its advantages. This contributed to the disadvantages of PCL, including expensive, toxic, and complex. Therefore, the shift towards the utilization of PCL as an alternative biomaterial in the development of biocomposites has been exponentially increased in recent years. PCL-based biocomposites are unique and versatile technology equipped with several importance features. In addition, the understanding on the properties of PCL and its blend is vital as it is influenced by the application of biocomposites. The superior characteristics of PCL-based green and hybrid biocomposites has expanded their applications, such as in the biomedical field, as well as in tissue engineering and medical implants. Thus, this review is aimed to critically discuss the characteristics of PCL-based biocomposites, which cover each mechanical and thermal properties and their importance towards several applications. The emergence of nanomaterials as reinforcement agent in PCL-based biocomposites was also a tackled issue within this review. On the whole, recent developments of PCL as a potential biomaterial in recent applications is reviewed.

Design and Analysis of a Biodegradable Polycaprolactone Flow Diverting Stent for Brain Aneurysms

The flow diverting stent (FDS) has become a promising endovascular device for the treatment of aneurysms. This research presents a novel biodegradable and non-braided Polycaprolactone (PCL) FDS. The PCL FDS was designed and developed using an in-house fabrication unit and coated on two ends with BaSO₄ for angiographic visibility. The mechanical flexibility and quality of FDS surfaces were examined with the UniVert testing machine, scanning electron microscope (SEM), and 3D profilometer. Human umbilical vein endothelial cell (HUVEC) adhesion, proliferation, and cell morphology studies on PCL FDS were performed. The cytotoxicity and NO production by HUVECs with PCL FDS were also conducted. The longitudinal tensile, radial, and bending flexibility were found to be 1.20 ± 0.19 N/mm, 0.56 ± 0.11 N/mm, and 0.34 ± 0.03 N/mm, respectively. The FDS was returned to the original shape and diameter after repeated compression and bending without compromising mechanical integrity. Results also showed that the proliferation and adhesion of HUVECs on the FDS surface increased over time compared to control without FDS. Lactate dehydrogenase (LDH) release and NO production showed that PCL FDS were non-toxic and satisfactory. Cell morphology studies showed that HUVECs were elongated to cover the FD surface and developed an endothelial monolayer. This study is a step forward toward the development and clinical use of biodegradable flow diverting stents for endovascular treatment of the aneurysm.

Development of Novel Thin Polycaprolactone (PCL)/Clay Nanocomposite Films with Antimicrobial Activity Promoted by the Study of Mechanical, Thermal, and Surface Properties

Infection with pathogenic microorganisms is of great concern in many areas, especially in healthcare, but also in food packaging and storage, or in water purification systems. Antimicrobial polymer nanocomposites have gained great popularity in these areas. Therefore, this study focused on new approaches to develop thin antimicrobial films based on biodegradable polycaprolactone (PCL) with clay mineral natural vermiculite as a carrier for antimicrobial compounds, where the active organic antimicrobial component is antifungal ciclopirox olamine (CPX). For possible synergistic effects, a sample in combination with the inorganic antimicrobial active ingredient zinc oxide was also prepared. The structures of all the prepared samples were studied by X-ray diffraction, FTIR analysis and, predominantly, by SEM. The very different structure properties of the prepared nanofillers had a fundamental influence on the final structural arrangement of thin PCL nanocomposite films as well as on their mechanical, thermal, and surface properties. As sample PCL/ZnOVER_CPX possessed the best results for antimicrobial activity against examined microbial strains, the synergic effect of CPX and ZnO combination on antimicrobial activity was proved, but on the other hand, its mechanical resistance was the lowest.

Tissue-engineered nerve graft using silk-fibroin/polycaprolactone fibrous mats decorated with bioactive cerium oxide nanoparticles

The main aim of this study was to evaluate the efficacy of cerium oxide nanoparticles (CNPs) encapsulated in fabricated hybrid silk-fibroin (SF)/polycaprolactone (PCL) nanofibers as an artificial neural guidance conduit (NGC) applicable for peripheral nerve regeneration. The NGC was prepared by PCL and SF filled with CNPs. The mechanical properties, contact angle, and cell biocompatibility experiments showed that the optimized concentration of CNPs inside SF and SF/PCL wall of conduits was 1% (wt/wt). The SEM image analysis showed the nanoscale texture of the scaffold in different topologies depend on composition with fiber diameters at about 351 ± 54 nm and 420 ± 73 nm respectively for CNPs + SF and CNPs + SF/PCL fibrous mats. Furthermore, contact angle measurement confirmed the hydrophilic behavior of the membranes, ascribable to the SF content and surface modification through modified methanol treatment. The balance of morphological and biochemical properties of hybrid CNPs 1% (wt/wt) + SF/PCL construct improves cell adhesion and proliferation in comparison with lower concentrations of CNPs in nanofibrous scaffolds. The release of CNPs 1% (wt/wt) from both CNPs + SF and CNPs+ SF/PCL fibrous mats was highly controlled and very slow during the extended time of incubation until 60 days. Fabricated double-layered NGC using CNPs + SF and CNPs + SF/PCL fibers was consistent for application in nervous tissue engineering and regenerative medicine from a structural and biocompatible perspective.

Ring-opening copolymerization of ε-caprolactone and δ-valerolactone by a titanium-based metal–organic framework

Copolymerization of ε-caprolactone and δ-valerolactone without any co-catalyst in a solvent-free medium under eco-friendly conditions using earth abundant Ti-metal based MOF, MIL-125.

Locally Controlled Diffusive Release of Bone Morphogenetic Protein-2 Using Micropatterned Gelatin Methacrylate Hydrogel Carriers

In this work, a novel and simple bone morphogenetic protein (BMP)-2 carrier is developed, which enables localized and controlled release of BMP-2 and facilitates bone regeneration. BMP-2 is localized in the gelatin methacrylate (GelMA) micropatterns on hydrophilic semi-permeable membrane (SNM), and its controlled release is regulated by the concentration of GelMA hydrogel and BMP-2. The controlled release of BMP-2 is verified using computational analysis and quantified using fluorescein isothiocyanate-bovine serum albumin (FITC-BSA) diffusion model. The osteogenic differentiation of osteosarcoma MG-63 cells is manipulated by localized and controlled BMP-2 release. The calcium deposits are significantly higher and the actin skeletal networks are denser in MG-63 cells cultured in the BMP-2-immobilized GelMA micropattern than in the absence of BMP-2. The proposed BMP-2 carrier is expected to not only act as a barrier membrane that can prevent invasion of connective tissue during bone regeneration, but also as a carrier capable of localizing and controlling the release of BMP-2 due to GelMA micropatterning on SNM. This approach can be extensively applied to tissue engineering, including the localization and encapsulation of cells or drugs.

Dual Delivery of Gemcitabine and Paclitaxel by Wet-Spun Coaxial Fibers Induces Pancreatic Ductal Adenocarcinoma Cell Death, Reduces Tumor Volume, and Sensitizes Cells to Radiation

Pancreatic ductal adenocarcinoma (PDAC) has a dismal prognosis, with surgical resection of the tumor in conjunction with systemic chemotherapy the only potential curative therapy. Up to 80% of diagnosed cases are deemed unresectable, prompting the need for alternative treatment approaches. Herein, coaxial polymeric fibers loaded with two chemotherapeutic agents, gemcitabine (Gem) and paclitaxel (Ptx), are fabricated to investigate the effect of local drug delivery on PDAC cell growth in vitro and in vivo. A wet-spinning fabrication method to form a coaxial fiber with a polycaprolactone shell and alginate core loaded with Ptx and Gem, respectively, is used. In vitro, Gem+Ptx fibers display significant cytotoxicity as well as radiosensitizing properties toward PDAC cell lines greater than the equivalent free drugs, which may be attributed to a radiosensitizing effect of the polymers. In vivo studies assessing Gem+Ptx fiber efficacy found that Gem+Ptx fibers reduce tumor volume in a xenograft mouse model of PDAC. Importantly, no difference in mouse weight, circulating cytokines, or liver function is observed in mice treated with Gem+Ptx fibers compared to the empty fiber controls confirming the safety of the implant approach. With further development, Gem+Ptx fibers can improve the treatment of unresectable PDAC in the future.

Intervertebral Disc Regeneration Using Stem Cell/Growth Factor-Loaded Porous Particles with a Leaf-Stacked Structure

Although biological therapies based on growth factors and transplanted cells have demonstrated some positive outcomes for intervertebral disc (IVD) regeneration, repeated injection of growth factors and cell leakage from the injection site remain considerable challenges for human therapeutic use. Herein, we prepare human bone marrow-derived mesenchymal stem cells (hBMSCs) and transforming growth factor-β3 (TGF-β3)-loaded porous particles with a unique leaf-stack structural morphology (LSS particles) as a combination bioactive delivery matrix for degenerated IVD. The LSS particles are fabricated with clinically acceptable biomaterials (polycaprolactone and tetraglycol) and procedures (simple heating and cooling). The LSS particles allow sustained release of TGF-β3 for 18 days and stable cell adhesiveness without additional modifications of the particles. On the basis of in vitro and in vivo studies, it was observed that the hBMSCs/TGF-β3-loaded LSS particles can provide a suitable milieu for chondrogenic differentiation of hBMSCs and effectively induce IVD regeneration in a beagle dog model. Thus, therapeutically loaded LSS particles offer the promise of an effective bioactive delivery system for regeneration of various tissues including IVD.

Effect of temperature and ultraviolet light on the bacterial kill effectiveness of antibiotic-infused 3D printed implants

Drug eluting 3D printed polymeric implants have great potential in orthopaedic applications since they are relatively inexpensive and can be designed to be patient specific thereby providing quality care. Fused Deposition Modeling (FDM) and Stereolithography (SLA) are among the most popular techniques available to print such polymeric implants. These techniques facilitate introducing antibiotics into the material at microscales during the manufacturing stage and subsequently, the printed implants can be engineered to release drugs in a controlled manner. However, FDM uses high temperature to melt the filament as it passes through the nozzle and SLA relies on exposure to nanoscale wavelength ultraviolet (UV) light which can adversely affect the anti-bacterial effectiveness of the antibiotics. The focus of this article is two-fold: i) Examine the effect of high temperature on the bacterial kill-effectiveness of eluted antibiotics through Polycaprolactone (PCL) based femoral implants and ii) Examine the effect of exposure to ultraviolet (UV) light on the bacterial kill-effectiveness of eluted antibiotics through femoral implants made up of a composite resin with various weight fractions of Polyethylene Glycol (PEG) and Polyethylene Glycol Diacrylate (PEGDA). Results indicate that even after exposing doxycycline, vancomycin and cefazolin at different temperatures between 20oC and 230oC, the antibiotics did not lose their effectiveness (kill radius of at least 0.85 cm). For doxycycline infused implants exposed to UV light, it was seen that a resin with 20 % PEGDA and 80 % PEG had the highest efficacy (1.8 cm of kill radius) and the lowest efficacy was found in an implant with 100 % PEGDA (1.2 cm of kill radius).

Nano/microstructures of shape memory polymers: from materials to applications

Shape memory polymers (SMPs) are macromolecules in which linear chains and crosslinking points play a key role in providing a shape memory effect. As smart polymers, SMPs have the ability to change shape, stiffness, size, and structure when exposed to external stimuli, leading to potential uses for SMPs throughout our daily lives in a diverse range of areas including the aerospace and automotive industries, robotics, biomedical engineering, smart textiles, and tactile devices. SMPs can be fabricated in many forms and sizes from the nanoscale to the macroscale, including nanofibers, nanoparticles, thin films, microfoams, and bulk devices. The introduction of nanostructure into SMPs can result in enhanced mechanical properties, unique structural color, specific surface area, and multiple functions. It is necessary to enhance the current understanding of the various nano/microstructures of SMPs and their fabrication, and to find suitable approaches for constructing SMP-based nano/microstructures for different applications. In this review, we summarize the current state of different SMP nano/microstructures, fabrication techniques, and applications, and give suggestions for their future development.

Feedback-Controlled Release of Alendronate from Composite Microparticles

Extended bone fractures or fractures coexisting with bone disorders can lead to non-unions where surgical intervention is required. Composite drug delivery systems are being used increasingly more in order to treat such defects locally. Alendronate (ALD), a bisphosphonate extensively used in clinical practice to treat conditions, such as osteoporosis, has been shown to assist bone fracture healing through its antiresorptive capacity. This study reports the development of a polymeric composite system for the in situ delivery of ALD, which possesses enhanced encapsulation efficiency (EE%) and demonstrates controlled release over a 70-day period. ALD and calcium phosphate (CaP) were incorporated within poly (lactic-co-glycolic acid) (PLGA) microspheres, giving rise to a 70% increase in EE% compared to a control system. Finally, a preliminary toxicological evaluation demonstrated a positive effect of the system on pre-osteoblastic cells over 72 h.

Electrospun PCL/PGS Composite Fibers Incorporating Bioactive Glass Particles for Soft Tissue Engineering Applications

Poly(glycerol-sebacate) (PGS) and poly(epsilon caprolactone) (PCL) have been widely investigated for biomedical applications in combination with the electrospinning process. Among others, one advantage of this blend is its suitability to be processed with benign solvents for electrospinning. In this work, the suitability of PGS/PCL polymers for the fabrication of composite fibers incorporating bioactive glass (BG) particles was investigated. Composite electrospun fibers containing silicate or borosilicate glass particles (13-93 and 13-93BS, respectively) were obtained and characterized. Neat PCL and PCL composite electrospun fibers were used as control to investigate the possible effect of the presence of PGS and the influence of the bioactive glass particles. In fact, with the addition of PGS an increase in the average fiber diameter was observed, while in all the composite fibers, the presence of BG particles induced an increase in the fiber diameter distribution, without changing significantly the average fiber diameter. Results confirmed that the blended fibers are hydrophilic, while the addition of BG particles does not affect fiber wettability. Degradation test and acellular bioactivity test highlight the release of the BG particles from all composite fibers, relevant for all applications related to therapeutic ion release, i.e., wound healing. Because of weak interface between the incorporated BG particles and the polymeric fibers, mechanical properties were not improved in the composite fibers. Promising results were obtained from preliminary biological tests for potential use of the developed mats for soft tissue engineering applications.

Signaling Molecule-Immobilized Porous Particles with a Leaf-Stacked Structure as a Bioactive Filler System

The ultimate purpose of this study was to develop a bioactive filler system that would allow volume restoration (passive property) and continuous release of signaling molecules to recruit soft tissues (bioactive property) and thus effectively correct facial aging. To achieve this, we prepared porous particles with a leaf-stacked structure throughout the entire particle volume (LSS particles) using a simple heating-cooling technique. LSS particles were loaded with insulin-like growth factor-1 (IGF-1) and vascular endothelial growth factor (VEGF) separately, by immersing the particles in signaling molecule-containing solutions for target tissue recruitment (adipose by IGF-1 and blood vessels by VEGF). IGF-1 and VEGF were continuously released from LSS particles for 28 and 21 days in vitro, respectively, even without additional chemical/physical modifications, because of the unique morphology of the particles. Signaling molecules preserved their bioactivity in vitro (induction of adipogenic and angiogenic differentiation) and in vivo (recruitment of fat and blood vessels) for a sufficient period. Moreover, it was observed that the LSS particles themselves have stable volume retention characteristics in the body. Thus, we suggest that the signaling molecule-loaded LSS particles can function as a bioactive filler system for volume retention and target tissue regeneration.

Effect of Polymer Demixed Nanotopographies on Bacterial Adhesion and Biofilm Formation

As the current global threat of antimicrobial resistance (AMR) persists, developing alternatives to antibiotics that are less susceptible to resistance is becoming an urgent necessity. Recent advances in biomaterials have allowed for the development and fabrication of materials with discrete surface nanotopographies that can deter bacteria from adhering to their surface. Using binary polymer blends of polystyrene (PS), poly(methyl methacrylate) (PMMA) and polycaprolactone (PCL) and varying their relative concentrations, PS/PCL, PS/PMMA and PCL/PMMA polymer demixed thin films were developed with nanoisland, nanoribbon and nanopit topographies. In the PS/PCL system, PS segregates to the air-polymer interface, with the lower solubility PCL preferring the substrate-polymer interface. In the PS/PMMA and PCL/PMMA systems, PMMA prefers the air-polymer interface due to its greater solubility and lower surface energy. The anti-adhesion efficacy of the demixed films were tested against Pseudomonas aeruginosa (PA14). PS/PCL and PCL/PMMA demixed films showed a significant reduction in cell counts adhered on their surfaces compared to pure polymer control films, while no reduction was observed in the counts adhered on PS/PMMA demixed films. While the specific morphology did not affect the adhesion, a relationship between bacterial cell and topographical surface feature size was apparent. If the surface feature was smaller than the cell, then an anti-adhesion effect was observed; if the surface feature was larger than the cell, then the bacteria preferred to adhere.

Porous electrospun poly(ε-caprolactone)/gelatin nanofibrous mat containing cinnamon for wound healing application: in vitro and in vivo study

In this study, cinnamon (cin) was loaded into poly(ε-caprolactone)/gelatin (PCL/Gel) nanofibrous matrices in order to fabricate an appropriate mat to improve wound healing. Mats were fabricated from PCL/COLL [1:1 (w/w)] solution with 1, 5 and 25% (w/v) of cinnamon. Prepared mats were characterized with regard to their microstructure, mechanical properties, porosity, surface wettability, water-uptake capacity, water vapor permeability, blood compatibility, microbial penetration and cellular response. The fabricated mats with and without cinnamon were used to treat the full-thickness excisional wounds in Wistar rats. The results indicated that the amount of cinnamon had a direct effect on porosity, mechanical properties, water uptake capacity, water contact angle, water vapor transmission rate and cell proliferation. In addition, the results of in vivo study indicated that after 14 days, the wounds which were treated with PCL/Gel 5%cin had better wound closure (98%) among other groups. Our results suggest that the cinnamon can be used as a suitable material for wound healing.

Analysis of early cellular responses of anterior cruciate ligament fibroblasts seeded on different molecular weight polycaprolactone films functionalized by a bioactive poly(sodium styrene sulfonate) polymer

With the growing number of anterior cruciate ligament (ACL) ruptures and the increased interest for regenerative medicine procedures, many studies are now concentrated on developing bioactive and biodegradable synthetic ligaments. For this application, the choice of raw materials with appropriate physicochemical characteristics and long-term degradation features is essential. Polycaprolactone (PCL) has the advantage of slow degradation that depends on its molecular weight. This study evaluates two PCL materials: a technical grade (PC60: 60 kDa) versus a medical grade (PC12: 80 kDa), both before and after functionalization with poly(sodium styrene sulfonate) (pNaSS). After determining the grafting process had little to no effect on the PCL physicochemical properties, sheep ACL fibroblast responses were investigated. The PC12 films induced a significantly lower expression of the tumor necrosis factor alpha inflammatory gene compared to the PC60 films. Both film types induced an overproduction of fibroblast growth factor-2 and transforming growth factor beta compared to the controls on day 5 and demonstrated collagen gene expression profiles similar to the controls on day 7. Upon protein adsorption, pNaSS grafting caused a rapid cell adhesion in the first 30 min and an increased adhesion strength (1.5-fold higher). Moreover, after 7 days, an increase in cell density and actin network development were noted on the grafted films.

Comprehensive Evaluation of Degradable and Cost-Effective Plasmonic Nanoshells for Localized Photothermolysis of Cancer Cells

Integrating the concept of biodegradation and light-triggered localized therapy in a functional nanoformulation is the current approach in onco-nanomedicine. Morphology control with an enhanced photothermal response, minimal toxicity, and X-ray attenuation of polymer-based nanoparticles is a critical concern for image-guided photothermal therapy. Herein, we describe the simple design of cost-effective and degradable polycaprolactone-based plasmonic nanoshells for the integrated photothermolysis as well as localized imaging of cancer cells. The gold-deposited polycaprolactone-based plasmonic nanoshells (AuPCL NS) are synthesized in a scalable and facile way under ambient conditions. The synthesized nanoshells are monodisperse, fairly stable, and highly inert even at five times (250 μg/mL) the therapeutic concentration in a week-long test. AuPCL NS are capable of delivering standalone photothermal therapy for the complete ablation of cancer cells without using any anticancerous drugs and causing toxicity. It delivers the same therapeutic efficacy to different cancer cell lines, irrespective of their chemorefractory status and also works as a potential computed tomography contrast agent for the integrated imaging-directed photothermal cancer therapy. High biocompatibility, degradability, and promising photothermal efficacy of AuPCL NS are attractive aspects of this report that could open new horizons of localized plasmonic photothermal therapy for healthcare applications.

Semiconducting Perylene Diimide Nanostructure: Multifunctional Phototheranostic Nanoplatform

Precision medicine requires noninvasive and accurate early diagnosis and individually appropriate treatments. Phototheranostics has been considered a frontier precision medical technology to provide rapid and safe disease localization and efficient cure. Harnessing the power of advanced nanomedicine with photonics, phototheranostics is rapidly developing and progressively becoming irreplaceable in modern medicine. Nanoscale semiconducting materials, such as inorganic semiconductors, organic conjugated polymers, and small molecules with photonic properties, have been extensively explored in medical imaging (fluorescence imaging, optical coherence tomography, and photoacoustic [PA] imaging) and phototherapy (photothermal, photodynamic, and photocontrolled combination therapies). In practical clinical applications, organic semiconducting materials, because of their biocompatibility and natural metabolism, are preferred over inorganic materials for phototheranostics. Supramolecular self-assembly is considered a significant method for preparing organic detachable and multifunctional phototheranostics, as supramolecular interactions, such as π-π interactions, hydrogen bonding, hydrophobic effects, and electrostatic interactions, are non-covalent and dynamic. Developing new and effective organic supramolecular phototheranostics requires exploration of well-designed basic building blocks with optical properties, understanding of the assembly at the nanoscale, and optimization of the phototheranostics with unique and distinctive multifunctional efficacy. In this Account, we summarize our recent work on the development of small molecular semiconducting perylene diimide (SPDI) for advanced phototheranostics. SPDI is modified to have strong near-infrared absorption beyond 700 nm by the push-pull electronic effect and owns the merits of remarkable photostability, large extinction coefficient, and high photothermal conversion efficiency. By hydrophilic modification, the amphiphile can self-assemble into a nanomicellar structure that allows PA imaging and can serve as a photothermal conversion agent. After theranostics delivery is achieved, this SPDI can be further functionalized for multimodality imaging and photothermally triggered multimodal synergistic therapy. Several well-designed asymmetric structures of SPDI can be obtained by stepwise modification of imides. It is noteworthy that the self-assembly of SPDI is controllable, allowing the preparation of different-sized spherical nanoparticles and rodlike nanoparticles and nanodroplets. For biomedical applications of SPDI phototheranostics (SPDIPTs), the size effect of SPDIPTs has been highlighted in lymph node mapping and cancer imaging. The PA properties and targeting peptide modification of SPDIPTs have brought about the ultrasensitive imaging of early thrombus. The supramolecular nanoconstructs of SPDIPTs further permit multimodality-imaging-guided cancer therapy. In brief, the design of SPDIPTs considers synthetic chemistry, supramolecular self-assembly, nanotechnology, and photonics. Furthermore, SPDIPTs have diverse biomedical applications and offer many opportunities for advancing nanomedicine.

Effects of vitamin D3 release from 3D printed calcium phosphate scaffolds on osteoblast and osteoclast cell proliferation for bone tissue engineering

Vitamin D₃ is a hydrophobic micronutrient and is known for inhibiting osteoclastic bone resorption in vivo via suppression of the Receptor Activator of Nuclear factor-Kappa B (RANK ligand) expression in osteoblasts. Although vitamin D is well-known for its promotion in bone health, little is known on its effects directly on bone cells. The objective of this study was to understand the effects of vitamin D₃ release from 3D printed calcium phosphate scaffolds towards bone cell proliferation. In this study, cholecalciferol, a common intake form of vitamin D₃, was successfully able to release from the scaffold matrix via the use of polyethylene glycol. Results showed a decrease in osteoclast resorption pits and healthier osteoblast cellular morphology compared to the control. Additively manufactured tricalcium phosphate scaffolds with designed porosity were loaded with vitamin D₃ and showed controlled release profiles in phosphate buffer and acetate buffer solutions. The release kinetics of vitamin D₃ from calcium phosphate scaffolds enabling osteoblast proliferation and inhibiting osteoclastic resorption can enhance healing for low load bearing applications for bone defects or permeate voids left by tumor resection.

Release of Vitamin D₃, cholecalciferol, from 3D printed calcium phosphate scaffolds showed reduced osteoclast resorption activity.

Thermal Properties and Non-Isothermal Crystallization Kinetics of Poly (δ-Valerolactone) and Poly (δ-Valerolactone)/Titanium Dioxide Nanocomposites

New poly (δ-valerolactone)/titanium dioxide (PDVL/TiO2) nanocomposites with different TiO2 nanoparticle loadings were prepared by the solvent-casting method and characterized by Fourier transform infra-red, differential scanning calorimetry, X-ray diffraction and scanning electron microscopy, and thermogravimetry analyses. The results obtained reveal good dispersion of TiO2 nanoparticles in the polymer matrix and non-formation of new crystalline structures indicating the stability of the crystallinity of TiO2 in the composite. A significant increase in the degree of crystallinity was observed with increasing TiO2 content. The non-isothermal crystallization kinetics of the PDVL/TiO2 system indicate that the crystallization process involves the simultaneous occurrence of two- and three-dimensional spherulitic growths. The thermal degradation analysis of this nanocomposite reveals a significant improvement in the thermal stability with increasing TiO2 loading.