Quercetin-Crosslinked Chitosan Films for Controlled Release of Antimicrobial Drugs.

Natural polymer-based films, due to their favorable biological and mechanical properties, have demonstrated great potential as coatings for biomedical applications. Among them, chitosan films have been widely studied both as coating materials and as controlled drug release systems. Crosslinkers are often used to tune chitosan's crosslinking degree and thus to control the drug release kinetics. For this purpose, quercetin, a plant-derived natural polyphenol, has gained attention as a crosslinker, mainly for its intrinsic anti-inflammatory, antioxidant, and antibacterial features. In this study, chitosan films crosslinked with three different concentrations of quercetin (10, 20, and 30% w/w) have been used as controlled release systems for the delivery of the antibacterial drug trimethoprim (TMP, 10% w/w). Physicochemical and antimicrobial properties were investigated. Surface wettability and composition of the films were assessed by contact angle measurements, X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy (FTIR), respectively. The release kinetic of TMP in phosphate-buffered saline (PBS) and 2-(N-morpholino) ethanesulfonic acid (MES) was studied over time. Finally, antibacterial properties were assessed on E. coli and S. aureus through Kirby-Bauer disc diffusion and micro-dilution broth assays. Results show that quercetin, at the tested concentrations, clearly increases the crosslinking degree in a dose-dependent manner, thus influencing the release kinetic of the loaded TMP while maintaining its bactericidal effects. In conclusion, this work demonstrates that quercetin-crosslinked chitosan films represent a promising strategy for the design of antibiotic-releasing coatings for biomedical applications.

Characterization and in vitro evaluation of chitosan/konjac glucomannan bilayer film as a wound dressing.

A novel bilayer film of chitosan and konjac glucomannan were prepared by the two-step casting technique. Blend films were also prepared to investigate the interactions between the two polymers in the interfacial region of the bilayer structure. Scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction analysis showed that, unlike in the blends, the physicochemical properties of each biopolymer were preserved in the bilayer film. Differential scanning calorimetry and thermogravimetric analysis also indicated a good thermostability and miscibility for both polymers, probably due to strong hydrogen bonds between their polymer chains. Biological, mechanical and water vapor transmission tests showed a high biocompatibility, low cytotoxicity, and suitable mechanical and barrier properties of the bilayer films for wound dressing applications.

Freezing influence on physical properties of glucomannan hydrogels.

Freezing is an interesting technique to modify the mechanical properties and morphology of hydrogels. Konjac glucomannan (KGM) is a polysaccharide that has potential use in cutting-edge areas as biomaterials and tissue engineering. In this work, we deeply investigated the influence of freezing on KGM. For that, KGM hydrogels were frozen at several freezing rates and temperatures. Results show that the freezing rate was the most important factor in the final physical properties of the KGM hydrogels. Slow freezing rate produced structures with isotropic and large pores, while fast freezing resulted in hydrogels with small and aligned pores. In addition, hydrogels frozen at high temperature (-8 °C) exhibited higher penetration modulus than hydrogels frozen at low temperature (-28 °C), since dense polymer regions are formed due to higher molecules dehydration caused by slow freezing. KGM hydrogels that underwent freezing can be explored as scaffolds for tissue engineering, with improved structural and mechanical properties.