Fabrication of gelatin-based antibacterial bilayer wound dressing using direct writing and electrospinning methods.

Fabricating a fibrous well-ordered wound dressing for accelerating full-thickness wounds is a desirable treatment vector. Here, through modifications in the material extrusion device and adding a pneumatic-based injection, a material extrusion method for gelatin was introduced with the ability to fabricate 3D structure with repeat layers to support cell activity for the under layer. Furthermore, in the upper layer, the co-electrospinning of PU with gelatin was designed to simultaneously exploit the oxygen permeability and mechanical stability of PU with regenerative properties and collagen-like structure of gelatin. Moreover, zinc oxide nanoparticles (ZnO) was added into the 3D-printed under layer to synergistically benefit from the antibacterial properties of ZnO and the excellent biocompatibility of gelatin. The controllable porosity of the under layer, enabled through the additive manufacturing method, was adjusted to mimic the extracellular matrix of natural tissue with around (127.28 ± 20.70) µm pore size after swelling with smooth fibers. S. aureus, E. coli, Bacillus subtilis, and Pseudomonas with inhibition zone diameters at âˆ¼ 2.14 cm and âˆ¼ 1.96 cm, ∼ 4.01 cm, and âˆ¼ 2.24 cm, respectively. Moreover, the scaffold showed great biocompatibility toward fibroblast cells after 7 days of cell culture with âˆ¼ 89 % cell viability.

In vitro and in vivo investigation of chitosan/silk fibroin injectable interpenetrating network hydrogel with microspheres for cartilage regeneration.

Articular cartilage is an avascular and almost acellular tissue with limited self-regenerating capabilities. Although injectable hydrogels have garnered a lot of attention as a promising treatment, a biocompatible hydrogel with adequate mechanical properties is yet to be created. In this study, an interpenetrating network hydrogel comprised of chitosan and silk fibroin was created through electrostatic and hydrophobic bonds, respectively. The polymeric network of the scaffold combined an effective microenvironment for cell activity with enhanced mechanical properties to address the current issues in cartilage scaffolds. Furthermore, microspheres (MS) were utilized for a controlled release of methylprednisolone acetate (MPA), around ~75 % after 35 days. The proposed scaffolds demonstrated great mechanical stability with ~0.047 MPa compressive moduli and ~145 kPa compressive strength. Moreover, the degradation rate of the samples (~45 % after 35 days) was optimized to match neo-cartilage formation. Furthermore, the use of natural biomaterials yielded good biocompatibility with ~76 % chondrocyte viability after 7 days. According to gross observation after 12 weeks the defect site of the treated groups was filled with minimally discernible boundary. These results were confirmed by histopathology assays were the treated groups showed higher chondrocyte count and collagen type II expression.

Fabrication of heparinized bi-layered vascular graft with PCL/PU/gelatin co-electrospun and chitosan/silk fibroin/gelatin freeze-dried hydrogel for improved endothelialization and enhanced mechanical properties.

Fabricating a biocompatible small-diameter vascular graft (< 6 mm) with mechanical properties similar to the natural vein and adding good anti-thrombogenic, endothelialization, and hyperplasia properties remains a challenge. To this end, we fabricated a heparinized bilayer graft to address this problem. The proposed bilayer sample consisted of a heparinized polycaprolactone (PCL), polyurethane (PU), and gelatin (G) co-electrospun inner layer and chitosan, gelatin, and silk fibroin freeze-dried hydrogel crosslinked with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS) outer layer. The samples exhibited great ultimate stress, Young's module, and suture retention of 4.16±0.25MPa, 8.24±2.59MPa and 4.83±0.31N, respectively. The heparin release assay indicated a sustained release profile of around 70% after 4weeks, which can be attributed to the excellent control via emulsion. Furthermore, the heparinized samples demonstrated good anti-thrombogenic properties investigated in the platelet adhesion assay. For the outer layer, the hydrogel crosslinked with non-toxic materials was prepared through the freeze-drying method to achieve high porosity (64.63%), suitable for smooth muscle cell activity. Moreover, inner and outer layers showed high cell viability toward endothelial (78.96%) and smooth muscle cells (57.77%), respectively. Overall, the proposed heparinized graft exhibited excellent potential for vascular graft regeneration.

A novel multifunctional chitosan-gelatin/carboxymethyl cellulose-alginate bilayer hydrogel containing human placenta extract for accelerating full-thickness wound healing.

The replication of skin's dermal and epidermal morphology within a full-thickness wound using a bi-layer hydrogel to cater to their distinct needs is a compelling pursuit. Moreover, human placenta extract (HPE), containing a diverse array of bioactive agents, has proven to be effective in promoting the wound healing process and enhancing epidermal keratinocytes. This study presents a multifunctional bi-layer hydrogel incorporating HPE for accelerating full-thickness wound healing through sustained HPE release, inhibition of bacteria invasion, and promotion of cell proliferation. The upper layer of the scaffold, known as the dressing layer, is composed of carboxymethyl cellulose and sodium alginate, serving as a supportive layer for cell proliferation. The under layer, referred to as the regenerative layer, is composed of chitosan and gelatin, providing an extracellular matrix-like, porous, moist, and antibacterial environment for cell growth. The scaffold was optimized to replicate the morphology of the dermal and epidermal layers, with suitable fibroblast infiltration and a pore size of approximately 283µm. Furthermore, the degradation rate of the samples matched the wound healing rate and persisted throughout this period. The sustained HPE release rate, facilitated by the degradation rate, was optimized to reach ~98% after 28 days, covering the entire healing period. The samples demonstrated robust antibacterial capabilities, with bacterial inhibition zone diameters of and 2.63±0.12cm for S. aureus and E. coli, respectively. The biocompatibility of the samples remained at approximately 68.33±4.5% after 21 days of fibroblast cell culture. The in vivo experiment indicated that the HPE@Bilayer hydrogel promotes the formation of new blood vessels and fibroblasts during the early stages of healing, leading to the appropriate formation of granulation tissue and a wound contraction rate of (79.31±3.1)%. Additionally, it resulted in the formation of a thick epidermal layer (keratinization) that effectively covered all the impaired areas, achieving a wound contraction rate of 95.83±6.3% at the late stage of wound healing. Furthermore, immunohistochemistry staining for CD31 and TGF-ß revealed that the HPE@Bilayer group had 22 blood vessels/field and 34%-66% immunoactive cells, respectively, after 14 days of healing. However, by day 21, angiogenesis and TGF-ß expression had declined, demonstrating that the wounds had been successfully treated with minimal scarring.

Investigating the correlation between the protein adhesion simulation and the biocompatibility of polymeric substrate for skin-tissue-engineering applications.

Investigating the protein adhesion properties of polymeric scaffolds through computational simulations can predict the biocompatibility of scaffolds before an experimental assay is carried out. This prediction can be highly beneficial since it can cut costs and the time it takes for experimental assays. The current study aims to test the hypothesis that there is a correlation between the biocompatibility of a composite scaffold and the molecular dynamics simulations of protein adhesion. To this end, chitosan and gelatin were selected for fabricating a composite skin-tissue wound scaffold with five different polymer ratios. This polymeric blend has not been simulated for protein adhesion. The cell proliferation and viability of the samples were quantified via MTT assay using fibroblast cells. Then a series of molecular dynamics simulations were performed to measure the adhesion energy of two prominent extracellular matrix proteins - fibronectin, and collagen type I. Besides, a higher gelatin percentage in the scaffold leads to a decrease in the porosity. The results demonstrated a strong correlation between the experimental data and molecular dynamics simulations. The sample with equal amounts of chitosan and gelatin had the highest cell viability and the strongest adhesion energy, of 239 kcal mol-1 for collagen type I, and 149 kcal mol-1 for fibronectin. This correlation was also evident in other samples: samples with gelatin-to-chitosan ratios of 3 : 1 and 1 : 3 had the lowest cell viability and the weakest adhesion energy, respectively.

Novel bilayer coating on gentamicin-loaded titanium nanotube for orthopedic implants applications.

Fabricating a multifunctional orthopedic implant which prevents post-surgery infection is highly desirable in advanced materials applications. However, designing an antimicrobial implant, which simultaneously promotes a sustained drug release and satisfactory cell proliferation, remains a challenge. The current study presents a drug-loaded surface-modified titanium nanotube (TNT) implant with different surface chemistry which was developed to investigate the effect of surface coating on drug release, antimicrobial activity, and cell proliferation. Accordingly, sodium alginate and chitosan were coated on the surface of TNT implants with different coating orders through layer-by-layer assembly. The coatings' swelling ratio and degradation rate were around 613% and 75%, respectively. The drug release results showed that surface-coatings prolonged the releasing profile for about 4 weeks. Chitosan coated TNTs demonstrated greater inhibition zone at 16.33mm compared with the other samples where no inhibition zone was observed. However, chitosan and alginate coated TNTs exhibited smaller inhibition zones at 48.56mm and 43.28mm, respectively, compared to bare TNT, which can be attributed to the coatings preventing the antibiotic burst release. Higher viability of cultured osteoblast cells was observed for chitosan-coated TNT as the top layer compared to the bare TNT at 12.18%, indicating improved bioactivity of TNT implants when the chitosan has the most contact with cells. Coupled with the cell viability assay, molecular dynamics (MD) simulations were carried out by placing collagen and fibronectin near the considered substrates. In agreement with cell viability results, MD simulations also indicated that chitosan had the highest adsorption energy approximately 60Kcal/mol. In summary, the proposed bilayer chitosan-coated drug-loaded TNT implant with chitosan and sodium alginate coating as the top and the bottom layers, respectively, can be a potential candidate for orthopedic applications in the light of its bacterial biofilm prevention, better osteoconductivity, and providing an adequate drug release profile.