Smart chitosan-based microgels for enhanced photothermal-assisted antibacterial activity

Nanofiber-reinforced chitosan/gelatine hydrogel with photothermal, antioxidant and conductive capabilities promotes healing of infected wounds

The wound healing process was often accompanied by bacterial infection and inflammation. The combination of electrically conductive nanomaterials and wound dressings could accelerate cell proliferation through endogenous electrical signaling, effectively promoting wound healing. In this study, polypyrrole was modified with dopamine hydrochloride by an in situ polymerization to form dopamine-polypyrrole (DA-Ppy) conductive nanofibers which successfully enhanced the water dispersibility and biocompatibility of polypyrrole. The DA-Ppy nanofibers were dispersed in an aqueous solution for >48 h and still maintained good stability. In addition, the DA-Ppy nanofibers showed good photothermal properties, and the temperature could reach 59.7 °C by 1.5 W/cm2 near-infrared light irradiation (NIR) for 10 min. DA-Ppy conductive nanofibres could be well dispersed in 3,4-dihydroxyphenylpropionic acid modified chitosan-carboxymethylated β-cyclodextrin modified gelatin (CG) hydrogel due to the presence of DA, which endowed CG/DA-Ppy hydrogel with good adhesion properties, and the hydrogel adhered to the pigskin would not be dislodged by washing with running water. Under NIR, the CG/DA-Ppy hydrogel showed significant antimicrobial properties. Moreover, the CG/DA-Ppy hydrogel had excellent biocompatibility. In addition, CG/DA-Ppy hydrogel was effective in scavenging ROS, inducing macrophage polarization towards the M2 phenotype, and modulating the level of wound inflammation in vitro. Finally, it was confirmed in rat-infected wounds that the tissue regeneration effect and collagen deposition in the CG/DA-Ppy + NIR group were significantly better than the other groups in the repair of infected wounds, indicating better repair of infected wounds. The results suggested that the photothermal, antioxidant DA-Ppy conductive nanofiber had great potential for application in infected wound healing.

The regulation of CuSNPs' interface for further enhancing mechanical and photothermal conversion properties of chitosan/@CuSNPs hybrid fibers

Our previous study has demonstrated that the microstructure of copper sulfide nanoparticles (CuSNPs) can be controlled to enhance mechanical and photothermal conversion properties of chitosan (CS)/CuSNPs hybrid fibers. However, achieving optimal dispersion and compatibility of CuSNPs within a CS matrix remains a challenge, this study aims to improve dispersion and compatibility by modifying the CuSNPs' interface, thereby enhancing mechanical and photothermal conversion properties of hybrid fibers. The interfaces of @CuSNPs (CuS@Xylan NPs, CuS@SA NPs, and CuS@PEG NPs) contain hydroxyl groups, facilitating the hydrogen bonds formation with the CS matrix. The dispersibility is further enhanced by the synergistic effect of xylan and SA's anionic charges with cationic chitosan. Notably, the viscosity of the CS/@CuSNPs hybrid spinning solution is significantly enhanced, resulting in improved breaking strength for initial hybrid fibers. Specifically, the breaking strength of CS/CuS@Xylan NPs hybrid fibers reaches 1.4 cN/dtex, exhibiting a 42.86 % and 20.6 % increase over CS and CS/CuSNPs hybrid fibers. Simultaneously, the CS/CuS@Xylan NPs hybrid fibers exhibit exceptional photothermal conversion performance, surpassing that of CS fibers by 5.2 times and CS/CuSNPs hybrid fibers by 1.4 times. The regulation of interface modification is an efficient approach to enhance the tensile strength and photothermal conversion properties of CS/CuSNPs hybrid fibers.

Recent developments in chitosan based microgels and their hybrids

Chitosan based microgels have gained great attention because of their chemical stability, biocompatibility, easy functionalization and potential uses in numerous fields. Production, properties, characterization and applications of chitosan based microgels have been systematically reviewed in this article. Some of these systems exhibit responsive behavior towards external stimuli like pH, light, temperature, glucose, etc. in terms of swelling/deswelling in an aqueous medium depending upon the functionalities present in the network which makes them a potential candidate for various applications in the fields of biomedicine, agriculture, catalysis, sensing and nanotechnology. Current research development and critical overview in this field accompanying by future possibilities is presented. The discussion is concluded with recommended possible future works for further progress in this field.

Enhanced anticancer activity of piperine: Structural optimization and chitosan-based microgels with boosted drug delivery

As a plant-derived drug, piperine possesses therapeutic efficacy for many diseases, but its inherent low solubility and bioavailability have greatly limited its clinical use. Herein, we extracted piperine from black pepper, optimized the structure of piperine to prepare various derivatives, and then explored the anticancer activity of these derivatives. Piperine and its derivatives have high anticancer selectivity against 4T1 cells, exhibiting obvious anticancer properties even at a low concentration of 100 μg/mL. Furthermore, the physicochemical properties of piperine and its derivatives were investigated using density functional theory, demonstrating their considerable biological activity. Moreover, the chitosan-based microgels were prepared to encapsulate the hydrophobic piperine derivative with a high loading efficiency of 81.7 % to overcome the low water solubility of the piperine derivative. It is worth noting that excessive glutathione in tumor cells triggers the degradation of microgels and realizes controllable drug release of up to 72.3 %. Due to its excellent properties, chitosan-based microgels loaded with the piperine derivative can obtain good anticancer behavior of approximately 13.14 % cell viability against 4T1 cells. Therefore, the chitosan-based microgels overcome the low water solubility of the piperine derivative through encapsulation and thus further augment their delivery efficiency and cell internalization capability to realize excellent anticancer activity. This work demonstrates the enhanced anticancer efficacy of the hydrophobic plant-derived drug by means of structural optimization of piperine and chitosan-based microgels with boosted drug delivery.