Tissue Engineering 3D Porous Scaffolds Prepared from Electrospun Recombinant Human Collagen (RHC) Polypeptides/Chitosan Nanofibers

A comprehensive in vitro characterization of non-crosslinked, diverse tissue-derived collagen-based membranes intended for assisting bone regeneration

Collagen-based membranes are class III-medical devices widely used in dental surgical procedures to favour bone regeneration. Here, we aimed to provide biophysical and biochemical data on this type of devices to support their optimal use and design/manufacturing. To the purpose, four commercial, non-crosslinked collagen-based-membranes, obtained from various sources (equine tendon, pericardium or cortical bone tissues, and porcine skin), were characterized in vitro. The main chemical, biophysical and biochemical properties, that have significant clinical implications, were evaluated. Membranes showed similar chemical features. They greatly differed in morphology as well as in porosity and density and showed a diverse ranking in relation to these latter two parameters. Samples highly hydrated in physiological medium (swelling-ratio values in the 2.5-6.0 range) and, for some membranes, an anisotropic expansion during hydration was, for the first time, highlighted. Rheological analyses revealed great differences in deformability (150-1500kPa G') also alerting about the marked variation in membrane mechanical behaviour upon hydration. Samples proved diverse sensitivity to collagenase, with the cortical-derived membrane showing the highest stability. Biological studies, using human-bone-derived cells, supported sample ability to allow cell proliferation and to prompt bone regeneration, while no relevant differences among membranes were recorded. Prediction of relative performance based on the findings was discussed. Overall, results represent a first wide panel of chemical/biophysical/biochemical data on collagen-based-membranes that 1) enhances our knowledge of these products, 2) aids their optimal use by providing clinicians with scientific basis for selecting products based on the specific clinical situation and 3) represents a valuable reference for optimizing their manufacturing.

Harnessing extracellular vesicles-mediated signaling for enhanced bone regeneration: novel insights into scaffold design

The increasing prevalence of bone replacements and complications associated with bone replacement procedures underscores the need for innovative tissue restoration approaches. Existing synthetic grafts cannot fully replicate bone vascularization and mechanical characteristics. This study introduces a novel strategy utilizing pectin, chitosan, and polyvinyl alcohol to create interpenetrating polymeric network (IPN) scaffolds incorporated with extracellular vesicles (EVs) isolated from human mesenchymal stem cells (hMSCs). We assess the osteointegration and osteoconduction abilities of these modelsin vitrousing hMSCs and MG-63 osteosarcoma cells. Additionally, we confirm exosome properties through Transmission Electron Microscopy (TEM), immunoblotting, and Dynamic Light Scattering (DLS).In vivo, chick allantoic membrane assay investigates vascularization characteristics. The study did not includein vivoanimal experiments. Our results demonstrate that the IPN scaffold is highly porous and interconnected, potentially suitable for bone implants. EVs, approximately 100 nm in size, enhance cell survival, proliferation, alkaline phosphatase activity, and the expression of osteogenic genes. EVs-mediated IPN scaffolds demonstrate promise as precise drug carriers, enabling customized treatments for bone-related conditions and regeneration efforts. Therefore, the EVs-mediated IPN scaffolds demonstrate promise as precise carriers for the transport of drugs, allowing for customized treatments for conditions connected to bone and efforts in regeneration.

Development of a highly porous bioscaffold by the combination of bubble entrapping and freezing-thawing techniques to fabricate hyaluronic acid/gelatin tri-layer wound dressing

The electrospun nanofibers and porous scaffolds hold great promise in regenerative medicine. A novel nanofiber-hydrogel‑silicone tri-layer wound dressing has been designed and fabricated to address the limitations of each platform. The bottom nanofiber layer with a 110 mm diameter meets the wound surface and regulates cell attachment and migration. The middle hydrogel layer was fabricated through the optimization of chemical crosslink formation and freezing-thawing cycles (physical crosslink). The fabricated hydrogel with interconnected porous structure has optimized properties (gel fraction (89.45 %) and porosity (80 %)) for wound dressing application. The silicone layer on the outer surface was designed to fix the wound dressing on the skin and prevent the penetration of pathogens. The scanning electron microscope micrograph showed structural integrity in the tri-layer scaffold. In vivo data showed that the tri-layer scaffold accelerates wound healing in the mice model and angiogenesis in the chorioallantoic membrane model. Therefore, the designed scaffold inspired by the skin's structure can be used as a wound dressing to treat wounds.

Electrospun PCL Filtration Membranes Enhanced with an Electrosprayed Lignin Coating to Control Wettability and Anti-Bacterial Properties

This study reports on the two-step manufacturing process of a filtration media obtained by first electrospinning a layer of polycaprolactone (PCL) non-woven fibers onto a paper filter backing and subsequently coating it by electrospraying with a second layer made of pure acidolysis lignin. The manufacturing of pure lignin coatings by solution electrospraying represents a novel development that requires fine control of the underlying electrodynamic processing. The effect of increasing deposition time on the lignin coating was investigated for electrospray time from 2.5 min to 120 min. Microstructural and physical characterization included SEM, surface roughness analysis, porosity tests, permeability tests by a Gurley densometer, ATR-FTIR analysis, and contact angle measurements vs. both water and oil. The results indicate that, from a functional viewpoint, such a natural coating endowed the membrane with an amphiphilic behavior that enabled modulating the nature of the bare PCL non-woven substrate. Accordingly, the intrinsic hydrophobic behavior of bare PCL electrospun fibers could be reduced, with a marked decrease already for a thin coating of less than 50 nm. Instead, the wettability of PCL vs. apolar liquids was altered in a less predictable manner, i.e., producing an initial increase of the oil contact angles (OCA) for thin lignin coating, followed by a steady decrease in OCA for higher densities of deposited lignin. To highlight the effect of the lignin type on the results, two grades of oak (AL-OA) of the Quercus cerris L. species and eucalyptus (AL-EU) of the Eucalyptus camaldulensis Dehnh species were compared throughout the investigation. All grades of lignin yielded coatings with measurable antibacterial properties, which were investigated against Staphylococcus aureus and Escherichia coli, yielding superior results for AL-EU. Remarkably, the lignin coatings did not change overall porosity but smoothed the surface roughness and allowed modulating air permeability, which is relevant for filtration applications. The findings are relevant for applications of this abundant biopolymer not only for filtration but also in biotechnology, health, packaging, and circular economy applications in general, where the reuse of such natural byproducts also brings a fundamental demanufacturing advantage.

Improving rodents and humans cardiac cell maturityin vitrothrough polycaprolactone and polyurethane nanofibers

Currently, numerous studies are conducted using nanofibers as a scaffold for culture cardiac cells; however, there still needs to be more research evaluating the impact of the physicochemical properties of polymer nanofibers on the structure and function of cardiac cells. We have studied how poly(ϵ-caprolactone) and polyurethane nanofibrous mats with different physicochemical properties influence the viability, morphology, orientation, and maturation of cardiac cells. For this purpose, the cells taken from different species were used. They were rat ventricular cardiomyoblasts (H9c2), mouse atrial cardiomyocytes (CMs) (HL-1), and human ventricular CMs. Based on the results, it can be concluded that cardiac cells cultured on nanofibers exhibit greater maturity in terms of orientation, morphology, and gene expression levels compared to cells cultured on polystyrene plates. Additionally, the physicochemical properties of nanofibers affecting the functionality of cardiac cells from different species and different parts of the heart were evaluated. These studies can support research on understanding and explaining mechanisms leading to cellular maturity present in the heart and the selection of nanofibers that will effectively help the maturation of CMs.

Chitosan scaffolds: Expanding horizons in biomedical applications

Chitosan, a natural polysaccharide from chitin, shows promise as a biomaterial for various biomedical applications due to its biocompatibility, biodegradability, antibacterial activity, and ease of modification. This review overviews "chitosan scaffolds" use in diverse biomedical applications. It emphasizes chitosan's structural and biological properties and explores fabrication methods like gelation, electrospinning, and 3D printing, which influence scaffold architecture and mechanical properties. The review focuses on chitosan scaffolds in tissue engineering and regenerative medicine, highlighting their role in bone, cartilage, skin, nerve, and vascular tissue regeneration, supporting cell adhesion, proliferation, and differentiation. Investigations into incorporating bioactive compounds, growth factors, and nanoparticles for improved therapeutic effects are discussed. The review also examines chitosan scaffolds in drug delivery systems, leveraging their prolonged release capabilities and ability to encapsulate medicines for targeted and controlled drug delivery. Moreover, it explores chitosan's antibacterial activity and potential for wound healing and infection management in biomedical contexts. Lastly, the review discusses challenges and future objectives, emphasizing the need for improved scaffold design, mechanical qualities, and understanding of interactions with host tissues. In summary, chitosan scaffolds hold significant potential in various biological applications, and this review underscores their promising role in advancing biomedical science.

Fabrication and Characterization of Electrospun Chitosan/Polylactic Acid (CH/PLA) Nanofiber Scaffolds for Biomedical Application

The present study demonstrates a strategy for preparing porous composite fibrous materials with superior biocompatibility and antibacterial performance. The findings reveal that the incorporation of PEG into the spinning solutions significantly influences the fiber diameters, morphology, and porous area fraction. The addition of a hydrophilic homopolymer, PEG, into the Ch/PLA spinning solution enhances the hydrophilicity of the resulting materials. The hybrid fibrous materials, comprising Ch modified with PLA and PEG as a co-solvent, along with post-treatment to improve water stability, exhibit a slower rate of degradation (stable, moderate weight loss over 16 weeks) and reduced hydrophobicity (lower contact angle, reaching 21.95 ± 2.17°), rendering them promising for biomedical applications. The antibacterial activity of the membranes is evaluated against Staphylococcus aureus and Escherichia coli, with PEG-containing samples showing a twofold increase in bacterial reduction rate. In vitro cell culture studies demonstrated that PEG-containing materials promote uniform cell attachment, comparable to PEG-free nanofibers. The comprehensive evaluation of these novel materials, which exhibit improved physical, chemical, and biological properties, highlights their potential for biomedical applications in tissue engineering and regenerative medicine.

Carboxymethyl cellulose-agarose-gelatin: A thermoresponsive triad bioink composition to fabricate volumetric soft tissue constructs

Polysaccharide based hydrogels have been predominantly utilized as ink materials for 3D bioprinting due to biocompatibility and cell responsive features. However, most hydrogels require extensive crosslinking due to poor mechanical properties leading to limited printability. To improve printability without using cytotoxic crosslinkers, thermoresponsive bioinks could be developed. Agarose is a thermoresponsive polysaccharide with upper critical solution temperature (UCST) for sol-gel transition at 35-37 °C. Therefore, we hypothesized that a triad of carboxymethyl cellulose(C)-agarose(A)-gelatin(G) could be a suitable thermoresponsive ink for printing since they undergo instantaneous gelation without any addition of crosslinkers after bioprinting. The blend of agarose-carboxymethyl cellulose was mixed with 1% w/v, 3% w/v and 5% w/v gelatin to optimize the triad ratio for hydrogel formation. It was observed that a blend (C2-A0.5-G1 and C2-A1-G1) containing 2% w/v carboxymethyl cellulose, 0.5% or 1% w/v agarose and 1% w/v gelatin formed better hydrogels with higher stability for up to 21 days in DPBS at 37 °C. Further, C2-A0.5-G1 and C2-A1-G1hydrogels showed higher storage modulus 762 ± 182 Pa & 2452 ± 430 Pa, higher porosity of 96.98 ± 2% & 98.2 ± 0.8% and swellability of 1518 ± 68% & 1587 ± 25% respectively. To evaluate the in vitro potential of these bioink formulations, indirect and direct cytotoxicity were determined using NCTC clone 929 (mouse fibroblast cells) and HADF (primary human adult dermal fibroblast) cells as per the ISO 10993-5 standards. Importantly, the printability of these bioinks was confirmed using extrusion bioprinting by successfully printing different complex 3D patterns.

Zinc Oxide-Incorporated Chitosan-Poly(methacrylic Acid) Polyelectrolyte Complex as a Wound Healing Material

A novel type of porous films based on the ZnO-incorporated chitosan-poly(methacrylic acid) polyelectrolyte complex was developed as a wound healing material. The structure of porous films was established by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and energy dispersive X-ray (EDX) analysis. Scanning electron microscope (SEM) and porosity studies revealed that the pore size and porosity of the developed films increased with the increase in zinc oxide (ZnO) concentration. The porous films with maximum ZnO content exhibited improved water swelling degree (1400%), controlled biodegradation (12%) for 28 days, a porosity of 64%, and a tensile strength of 0.47 MPa. Moreover, these films presented antibacterial activity toward Staphylococcus aureus and Micrococcus sp. due to the existence of ZnO particles. Cytotoxicity studies demonstrated that the developed films had no cytotoxicity against the mouse mesenchymal stem (C3H10T1/2) cell line. These results reveal that ZnO-incorporated chitosan-poly(methacrylic acid) films could be used as an ideal material for wound healing application.

PCL-based 3D nanofibrous structure with well-designed morphology and enhanced specific surface area for tissue engineering application

Tissue engineering opens a new horizon for biological tissue replacement applications. Scaffolds, appropriate cells, and signaling induction are the main three determinant parameters in any tissue engineering applications. Designing a suitable scaffold which can mimic the cellular inherent and natural habitation is of great importance for cellular growth and proliferation. Just like a natural extracellular matrix (ECM), scaffolds provide the cells with an environment for performing biological functions. Accordingly, vast surface area and three-dimensional nanofibrous structures are among the pivotal characteristics of functional scaffolds in tissue engineering, and enhancement of their properties is the main purpose of the present research. In our previous study, a patterned structure composed of continuous nanofibers and microparticles was introduced. In this work, a new modification is applied for adjustment of the surface area of an electrospun/electrosprayed scaffold. For this purpose, at predetermined stages during electrospinning/electrospraying, the nitrogen gas is flushed through the mesh holes of the collector in the opposite direction of the jet movement. This method has led to the formation of very thin nanofibrous layers at nitrogen flush intervals by providing a cooling effect of the sweeping nitrogen. As a consequence, a straticulated structure has been fabricated which possesses extremely high surface/volume ratio. The porosity, water absorption, and morphological analysis were conducted on the obtained scaffold. In vitro cytocompatibility assessments as well as histological analysis demonstrated that the fabricated scaffold provides a proper substrate for cellular attachment, proliferation and infiltration. These findings can be advantageous in three-dimensional tissue engineering such as bone tissue engineering applications. Furthermore, according to the advanced microstructure and vast surface area of the fabricated samples, they can be applied in many other applications, such as membrane, filtration, etc.

Recombinant and genetic code expanded collagen-like protein as a tailorable biomaterial

Collagen occurs in nature with a dedicated triple helix structure and is the most preferred biomaterial in commercialized medical products. However, concerns on purity, disease transmission, and the reproducibility of animal derived collagen restrict its applications and warrants alternate recombinant sources. The expression of recombinant collagen in different prokaryotic and eukaryotic hosts has been reported with varying degrees of success, however, it is vital to elucidate the structural and biological characteristics of natural collagen. The recombinant production of biologically functional collagen is restricted by its high molecular weight and post-translational modification (PTM), especially the hydroxylation of proline to hydroxyproline. Hydroxyproline plays a key role in the structural stability and higher order self-assembly to form fibrillar matrices. Advancements in synthetic biology and recombinant technology are being explored for improving the yield and biomimicry of recombinant collagen. It emerges as reliable, sustainable source of collagen, promises tailorable properties and thereby custom-made protein biomaterials. Remarkably, the evolutionary existence of collagen-like proteins (CLPs) has been identified in single-cell organisms. Interestingly, CLPs exhibit remarkable ability to form stable triple helical structures similar to animal collagen and have gained increasing attention. Strategies to expand the genetic code of CLPs through the incorporation of unnatural amino acids promise the synthesis of highly tunable next-generation triple helical proteins required for the fabrication of smart biomaterials. The review outlines the importance of collagen, sources and diversification, and animal and recombinant collagen-based biomaterials and highlights the limitations of the existing collagen sources. The emphasis on genetic code expanded tailorable CLPs as the most sought alternate for the production of functional collagen and its advantages as translatable biomaterials has been highlighted.

Establishing a novel 3D printing bioinks system with recombinant human collagen

Bioinks are one of the key elements in realizing three-dimensional (3D) bioprinting. However, bioinks prepared from conventional collagen are hindered to their further applications due to concerns of collagen purity, unstable mechanical properties, and low solubility under neutralized conditions. This study aimed to develop a reliable UV-curable bioink system from a novel water-soluble recombinant human collagen (RHC). RHC was modified by methacrylic anhydride (MAA) and later crosslinked by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC)/N-hydroxysuccinimide (NHS) to obtain Pro-RHCMA. ¹H nuclear magnetic resonance (¹H NMR) confirmed the methacryloyl grafts, Fourier transform-infrared spectroscopy (FT-IR) illustrated the chemical crosslinking in producing the Pro-RHCMA. Internal morphology, mechanical properties and degradation of UV cured boinks were MAA and EDC/NHS modification-dependent. Photorheological properties and printability of the bioinks were determined. Cellular bioactivities were sustained within the printed bioinks, validating the bioinks biocompatibility in vitro. Finally, qRT-PCR revealed that the Pro-RHCMA bioinks provided a cell-friendly microenvironment for human umbilical vein endothelial cells (HUVECs) and human foreskin fibroblasts (HFFs), by supporting the expression of extracellular matrix (ECM) and angiogenesis-associated proteins, respectively. Taken together, this novel RHC-based bioink system shows great potential in tissue engineering and regenerative medicine.

Preparation of Chitosan/Recombinant Human Collagen-Based Photo-Responsive Bioinks for 3D Bioprinting

Collagen and chitosan are frequently used natural biomaterials in tissue engineering. However, most collagen is derived from animal tissue, with inconsistent quality and pathogen transmittance risks. In this context, we aimed to use a reliable Type-III recombinant human collagen (RHC) as an alternative biomaterial together with chitosan to develop novel photo-responsive bioinks for three-dimensional (3D) bioprinting. RHC was modified with methacrylic anhydride to obtain the RHC methacryloyl (RHCMA) and mixed with acidified chitosan (CS) to form composites CS-RHCMA. The characterizations demonstrated that the mechanical properties and the degradation of the bioinks were tunable by introducing the CS. The printabilities improved by adding CS to RHCMA, and various structures were constructed via extrusion-based 3D printing successfully. Moreover, in vitro tests confirmed that these CS-RHCMA bioinks were biocompatible as human umbilical vein endothelial cells (HUVECs) were sustained within the constructs post-printing. The results from the current study illustrated a well-established bioinks system with the potential to construct different tissues through 3D bioprinting.

Biocompatible pectin-based hybrid hydrogels for tissue engineering applications

Hybrid hydrogels made of chemically modified pectin, gelatin and xanthan gum have been formulated and processed through a double crosslinking step, aimed at wound healing applications.