Synthesis, Characterization And Evaluation of Skin Tissue Engineering Potential of Poly(Lactic Acid)-Nanoclay Composite Scaffolds Doped with Various Boron Components

Abstract

This study aims to investigate the characteristic features of boron (B) and nanoclay containing micro/nanocomposites and their effect on the normal human dermal fibroblast (NHDF) cells as a potential material to be used as a wound dressing. In the first part of this study, hybrid composites were fabricated by solvent-casting and electrospinning, and the impact of fabrication methods on resulting scaffolds was investigated. In this regard, montmorillonite (MMT) was modified with trimethyl octadecyl ammonium bromide (TMOD) as a quaternary ammonium salt. Then, B compounds, boron nitride (BN), zinc borate (ZB), or phenylboronic acid (PBA) were adsorbed on organomodified MMT (OMMT), and poly(lactic acid) (PLA) based PLA-OMMT/B hybrid composites were fabricated by solvent-casting and electrospinning. Modification of MMT nanoparticles with TMOD occurred through an ion-exchange reaction, leading to a series of critical changes in characteristic properties of the resulting composite: better distribution, enhanced mechanical and thermal properties, faster biodegradation, and higher crystallinity. Although the modification of MMT improved the overall properties of hybrid composites produced by both fabrication methods, electrospun scaffolds demonstrated superior characteristics to solvent-cast membranes. Consequently, fibrous scaffolds were chosen for antibacterial tests and cell culture studies. Scaffolds containing OMMT in their structure exhibited dramatic inhibition against gram-positive bacteria. Moreover, hybrid composites with ZB and PBA demonstrated both bacteriostatic and bactericidal effects for gram-positive Staphylococcus aureus (S. aureus) and gram-negative Escherichia coli (E. coli). The 100%, 50%, and 25% (v/v) extracts of the PLA-OMMT scaffolds showed a modest cytotoxic effect on the NHDFs at the second-day culture that probably originated from TMOD. These results were evaluated as PLA-OMMT/B scaffolds, thanks to their antibacterial, morphological, and chemical properties can be used as a wound dressing that supports the early stages of wound healing, where it will show limited interaction with cells.

In the second part of this study, BN, ZB, and PBA were adsorbed on neat MMT, and PLA-based MMT/B micro composites were fabricated by electrospinning. The incorporation of neat MMT into the polymer matrix not only enhanced thermal properties and water uptake capacity but also led to the generation of porous nanofibers with antibacterial effects against S. aureus. The composites with BN, ZB, and PBA demonstrated bacteriostatic effects against both E. coli and S. aureus. In-vitro cell culture studies performed with NHDF indicated the non-toxic effect of utilized B compounds. The scanning electron microscope (SEM) and live/dead staining of cell-containing scaffolds showed that the incorporation of MMT supported cell adhesion and proliferation, and the further addition of B compounds, especially PBA, increased cell viability for 14 days. The cells retained their healthy morphology and viability in all groups, meaning that functionalized fibrous scaffolds were suitable for skin tissue engineering applications.