Chitosan, which is derived from chitin, is the only known natural alkaline cationic polymer. Chitosan is a biological material that can significantly improve the living standard of the country. It has excellent properties such as good biodegradability, biocompatibility, and cell affinity, and has excellent biological activities such as antibacterial, antioxidant, and hemostasis. In recent years, the demand has increased significantly in many fields and has huge application potential. Due to the poor water solubility of chitosan, its wide application is limited. However, chemical modification of the chitosan matrix structure can improve its solubility and biological activity, thereby expanding its application range. The review covers the period from 1996 to 2022 and was elaborated by searching Google Scholar, PubMed, Elsevier, ACS publications, MDPI, Web of Science, Springer, and other databases. The various chemical modification methods of chitosan and its main activities and application research progress were reviewed. In general, the modification of chitosan and the application of its derivatives have had great progress, such as various reactions, optimization of conditions, new synthetic routes, and synthesis of various novel multifunctional chitosan derivatives. The chemical properties of modified chitosan are usually better than those of unmodified chitosan, so chitosan derivatives have been widely used and have more promising prospects. This paper aims to explore the latest progress in chitosan chemical modification technologies and analyze the application of chitosan and its derivatives in various fields, including pharmaceuticals and textiles, thus providing a basis for further development and utilization of chitosan.

Skin photoaging is premature skin aging damage that occurs after repeated exposure to ultraviolet (UV) radiation. Although isothiocyanates extracted from the moringa tree (Moringa oleifera Lam.) (MITC) exhibit excellent effects against skin photoaging, its application is restricted because of its characteristics, such as extremely low water solubility, bioavailability, and easy degradation. Currently, flexible nanoliposomes have gained increasing interest as a biocompatible polymer for applications such as transdermal drug delivery. We prepare amphiphilic hyaluronic acid (HA) conjugated with ceramide (CE) to modify nanoliposomes for MITC (HACE/MITC NPs) delivery. The HACE/MITC nanoparticles (NPs) are prepared and characterized for entrapment efficiency, particle size, polydispersity index, zeta potential, in vitro release, in vivo skin permeation, and in vitro protective effect of photoaging. The zeta potential of MITC NPs and HACE/MITC NPs is −24.46 mV and −24.93 mV, respectively. After modification of HACE, the entrapment efficient of MITC liposome increased from 62.54% to 70.67%, and the particle size decreased from 266.1 nm to 192.8 nm. In vivo skin permeation, permeated drug increased from 49.42 to 71.40%. Moreover, the results showed that the entrapment of MITC in nanoliposomes improves its stability, efficacy, and skin permeation. Further, HACE/MITC NPs are favorable for uptake by HaCaT cells without requiring changes in cell morphology, which significantly improves the activities of antioxidant enzymes, scavenges UVB-induced reactive oxygen species, protects skin from damage, and reduces MMP-1, MMP-3, and MMP-9 expression caused by radiation-induced photoaging. Our results strongly suggest that flexible nanoliposomes successfully improved the cell membrane permeation of MITC, and that anti-photoaging and HACE/MITC NPs can potentially be used as candidates for photoaging therapy.

Although amphiphilic chitosan has been widely studied as a drug carrier for drug delivery, fewer studies have been conducted on the antimicrobial activity of amphiphilic chitosan. In this study, we successfully synthesized deoxycholic acid-modified chitosan (CS-DA) by grafting deoxycholic acid (DA) onto chitosan C₂-NH₂, followed by grafting succinic anhydride, to prepare a novel amphiphilic chitosan (CS-DA-SA). The substitution degree was 23.93% for deoxycholic acid and 29.25% for succinic anhydride. Both CS-DA and CS-DA-SA showed good blood compatibility. Notably, the synthesized CS-DA-SA can self-assemble to form nanomicelles at low concentrations in an aqueous environment. The results of CS, CS-DA, and CS-DA-SA against Escherichia coli and Staphylococcus aureus showed that CS-DA and CS-DA-SA exhibited stronger antimicrobial effects than CS. CS-DA-SA may exert its antimicrobial effect by disrupting cell membranes or forming a membrane on the cell surface. Overall, the novel CS-DA-SA biomaterials have a promising future in antibacterial therapy.

Creation of bio-multifunctional wound dressings with potent hemostatic, antibacterial, anti-inflammatory, and angiogenesis features for bolstering the healing of full-thickness wounds is sought after for clinical applications. We created bio-multifunctional composite sponges by coupling alginate and chitosan with Sargassum pallidum polysaccharides through electrostatic interactions, calcium ion (Ca²⁺) crosslinking, and lyophilization. Alginate/chitosan (AC) sponges with different concentrations of Sargassum pallidum polysaccharides were obtained and termed AC, ACS—1%, ACS—2.5%, and ACS—5%. ACS—1% and ACS—2.5% sponges exhibited uniform porosity, high water vapor transmission rate, high water absorption, as well as good hemostatic and antibacterial abilities. ACS—2.5% sponges facilitated wound closure and promoted angiogenesis and re-epithelialization in the dermis. These data suggest that ACS sponges containing a certain amount of Sargassum pallidum polysaccharides could be employed for treatment of full-thickness skin wounds.

Curcumin (Cur) is a phytochemical with various beneficial properties, including antioxidant, anti-inflammatory, and anticancer activities. However, its hydrophobicity, poor bioavailability, and stability limit its application in many biological approaches. In this study, a novel amphiphilic chitosan wall material was synthesized. The process was carried out via grafting chitosan with succinic anhydride (SA) as a hydrophilic group and deoxycholic acid (DA) as a hydrophobic group; ¹H-NMR, FTIR, and XRD were employed to characterize the amphiphilic chitosan (CS—SA—DA). Using a low-cost, inorganic solvent-based procedure, CS—SA—DA was self-assembled to load Cur nanomicelles. This amphiphilic polymer formed self-assembled micelles with a core–shell structure and a critical micelle concentration (CMC) of 0.093 mg·mL⁻¹. Cur-loaded nanomicelles were prepared by self-assembly and characterized by the Nano Particle Size Potential Analyzer and transmission electron microscopy (TEM). The mean particle size of the spherical Cur-loaded micelles was 770 nm. The drug entrapment efficiency and loading capacities were up to 80.80 ± 0.99% and 19.02 ± 0.46%, respectively. The in vitro release profiles of curcumin from micelles showed a constant release of the active drug molecule. Cytotoxicity studies and toxicity tests for zebrafish exhibited the comparable efficacy and safety of this delivery system. Moreover, the results showed that the entrapment of curcumin in micelles improves its stability, antioxidant, and anti-inflammatory activity.