Design and Characterization of a Bioinspired Polyvinyl Alcohol Matrix with Structural Foam-Wall Microarchitectures for Potential Tissue Engineering Applications

Electrospun Nanofibrous Mesh Based on PVA, Chitosan, and Usnic Acid for Applications in Wound Healing

Injuries and diseases of the skin require accurate treatment using nontoxic and noninvasive biomaterials, which aim to mimic the natural structures of the body. There is a strong need to develop biodevices capable of accommodating nutrients and bioactive molecules and generating the process of vascularization. Electrospinning is a robust technique, as it can form fibrous structures for tissue engineering and wound dressings. The best way of forming such meshes for wound healing is to choose two polymers that complement each other regarding their properties. On the one hand, PVA is a water-soluble synthetic polymer widely used for the preparation of hydrogels in the field of biomedicine owing to its biocompatibility, water solubility, nontoxicity, and considerable mechanical properties. PVA is easy to subject to electrospinning and can offer strong mechanical stability of the mesh, but it is necessary to improve its biological properties. On the other hand, CS has good biological properties, including biodegradability, nontoxicity, biocompatibility, and antimicrobial properties. Still, it is harder to electrospin and does not possess as good mechanical properties as PVA. As these structures also allow the incorporation of bioactive agents due to their high surface-area-to-volume ratio, the interesting point was to incorporate usnic acid into the structure as it is a natural and suitable alternative agent for burn wounds treatment which avoids an improper or overuse of antibiotics and other invasive biomolecules. Thus, we report the fabrication of an electrospun nanofibrous mesh based on PVA, chitosan, and usnic acid with applications in wound healing. The obtained nanofibers mesh was physicochemically characterized by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). In vitro biological assays were performed to evaluate the antimicrobial properties of the samples using the MIC (minimum inhibitory concentration) assay and evaluating the influence of fabricated meshes on the Staphylococcus aureus biofilm development, as well as their biocompatibility (demonstrated by fluorescence microscopy results, an XTT assay, and a glutathione (GSH) assay).

Fabrication and Determination of the Sun Protection Factor and Ultraviolet Protection Factor for Piscean Collagen/Bischalcone Derivative (B1) Composite Films with Wide-Range UV Shielding

The present study investigates the development of distinct UV-A and UV-B radiation filtering materials through the introduction of a heterocyclic bischalcone derivative [(3,5-bis{[4-(methylsulfanyl)phenyl]methylidene}piperidin-4-one] (B1) into the matrix of PVA/Piscean collagen blend films (1:1) prepared through the solution casting method and characterized. The dopant concentration varied from 0.25 to 4%. The scanning electron microscopy images showed the rough surface due to the uniform dispersion of dopant B1. The addition of different concentrations of B1 altered the mechanical strength with a proportional increase in Young's modulus (146-317 MPa), tensile strength (23.3-39.21 MPa), and decrease in its elongation at break (158.8-105.2%). As the dopant B1 belongs to the bischalcone class of compounds which absorb in the UV-vis region (370 nm λ_max) due to the α, β unsaturated keto group, it was selected for doping. Dopant concentration-dependent increase in density was observed in films (31-162 mg/cm³). The bathochromic shift in UV absorption from 370 to 390 nm for λ_max as well as hyperchromism was evidenced with proportional increase in the concentration of B1, indicating its capacity to block UV rays. On determining the UV filtering ability for all the prepared films, the one with 4% dopant showed a higher sun protection factor (SPF) with a value of 27.53 and ultraviolet protection factor (UPF) with a value of 58.23. In addition, the degradation of supercoiled PBR322 DNA on UV irradiation was effectively inhibited by these films with a dopant concentration of 0.5-4.0%, which might cause less harm to the skin. The inferences of the experiments would indicate the use of these water-insoluble films as UV blocking potential materials with a merit of SPF and UPF characteristics.

Highly Organized Porous Gelatin-Based Scaffold by Microfluidic 3D-Foaming Technology and Dynamic Culture for Cartilage Tissue Engineering

A gelatin-based hydrogel scaffold with highly uniform pore size and biocompatibility was fabricated for cartilage tissue engineering using microfluidic 3D-foaming technology. Mainly, bubbles with different diameters, such as 100 μm and 160 μm, were produced by introducing an optimized nitrogen gas and gelatin solution at an optimized flow rate, and N₂/gelatin bubbles were formed. Furthermore, a cross-linking agent (1-ethyl-3-(3-dimethyl aminopropyl)-carbodiimide, EDC) was employed for the cross-linking reaction of the gelatin-based hydrogel scaffold with uniform bubbles, and then the interface between the close cells were broken by degassing. The pore uniformity of the gelatin-based hydrogel scaffolds was confirmed by use of a bright field microscope, conjugate focus microscope and scanning electron microscope. The in vitro degradation rate, mechanical properties, and swelling rate of gelatin-based hydrogel scaffolds with highly uniform pore size were studied. Rabbit knee cartilage was cultured, and its extracellular matrix content was analyzed. Histological analysis and immunofluorescence staining were employed to confirm the activity of the rabbit knee chondrocytes. The chondrocytes were seeded into the resulting 3D porous gelatin-based hydrogel scaffolds. The growth conditions of the chondrocyte culture on the resulting 3D porous gelatin-based hydrogel scaffolds were evaluated by MTT analysis, live/dead cell activity analysis, and extracellular matrix content analysis. Additionally, a dynamic culture of cartilage tissue was performed, and the expression of cartilage-specific proteins within the culture time was studied by immunofluorescence staining analysis. The gelatin-based hydrogel scaffold encouraged chondrocyte proliferation, promoting the expression of collagen type II, aggrecan, and sox9 while retaining the structural stability and durability of the cartilage after dynamic compression and promoting cartilage repair.