Exploring modified chitosan-based gene delivery technologies for therapeutic advancements

One of the critical steps in gene therapy is the successful delivery of the genes. Immunogenicity and toxicity are major issues for viral gene delivery systems. Thus, non-viral vectors are explored. A cationic polysaccharide like chitosan could be used as a nonviral gene delivery vector owing to its significant interaction with negatively charged nucleic acid and biomembrane, providing effective cellular uptake. However, the native chitosan has issues of targetability, unpacking ability, and solubility along with poor buffer capability, hence requiring modifications for effective use in gene delivery. Modified chitosan has shown that the "proton sponge effect" involved in buffering the endosomal pH results in osmotic swelling owing to the accumulation of a greater amount of proton and chloride along with water. The major challenges include limited exploration of chitosan as a gene carrier, the availability of high-purity chitosan for toxicity reduction, and its immunogenicity. The genetic drugs are in their infancy phase and require further exploration for effective delivery of nucleic acid molecules as FDA-approved marketed formulations soon.

Synthesis and characterization of n-phosphonium chitosan and its virucidal activity evaluation against coronavirus

Despite the worldwide vaccination effort against COVID-19, the demand for biocidal materials has increased. One promising solution is the chemical modification of polysaccharides, such as chitosan, which can provide antiviral activity through the insertion of cationic terminals. In this study, chitosan was modified with (4-carboxybutyl) triphenylphosphonium bromide to create N-phosphonium chitosan (NPCS), a quaternized derivative. The resulting NPCS samples with three degrees of substitution (15.6 %, 19.8 % and 24.2 %) were characterized and found to have improved solubility in water and alkaline solutions but reduced thermal stability. The particles zeta potential exhibits positive charges and is directly correlated with the degree of substitution of the derivative. In virucidal assays, all NPCS samples were able to inhibit 99.999 % of the MHV-3 coronavirus within 5 min at low concentrations of 0.1 mg/mL, while maintaining low cytotoxicity to L929 cells. In addition to its potential application against current coronavirus strains, NPCS could also be valuable in combating future pandemics caused by other viral pathogens. The antiviral properties of NPCS make it a promising material for use in coating surface and personal protective equipment to limit the spread of disease-causing viruses.

Biomedical Applications of Quaternized Chitosan

The natural polymer chitosan is the second most abundant biopolymer on earth after chitin and has been extensively explored for preparation of versatile drug delivery systems. The presence of two distinct reactive functional groups (an amino group at C2, and a primary and secondary hydroxyl group at C3 and C6) of chitosan are involved in the transformation of expedient derivatives such as acylated, alkylated, carboxylated, quaternized and esterified chitosan. Amongst these, quaternized chitosan is preferred in pharmaceutical industries owing to its prominent features including superior water solubility, augmented antimicrobial actions, modified wound healing, pH-sensitive targeting, biocompatibility, and biodegradability. It has been explored in a large realm of pharmaceuticals, cosmeceuticals, and the biomedical arena. Immense classy drug delivery systems containing quaternized chitosan have been intended for tissue engineering, wound healing, gene, and vaccine delivery. This review article outlines synthetic techniques, basic characteristics, inherent properties, biomedical applications, and ubiquitous challenges associated to quaternized chitosan.

An Overview of Current Knowledge on the Properties, Synthesis and Applications of Quaternary Chitosan Derivatives

Chitosan, a chitin-derivative polysaccharide, known for its non-toxicity, biocompatibility and biodegradability, presents limited applications due to its low solubility in neutral or basic pH medium. Quaternization stands out as an alternative to modify this natural polymer, aiming to improve its solubility over a wide pH range and, consequently, expand its range of applications. Quaternization occurs by introducing a quaternary ammonium moiety onto or outside the chitosan backbone, via chemical reactions with primary amino and hydroxyl groups, under vast experimental conditions. The oldest and most common forms of quaternized chitosan involve N,N,N-trimethyl chitosan (TMC) and N-[(2-hydroxy-3-trimethyl ammonium) propyl] chitosan (HTCC) and, more recently, quaternized chitosan by insertion of pyridinium or phosphonium salts. By modifying chitosan through the insertion of a quaternary moiety, permanent cationic charges on the polysaccharide backbone are achieved and properties such as water solubility, antimicrobial activity, mucoadhesiveness and permeability are significantly improved, enabling the application mainly in the biomedical and pharmaceutical areas. In this review, the main quaternized chitosan compounds are addressed in terms of their structure, properties, synthesis routes and applications. In addition, other less explored compounds are also presented, involving the main findings and future prospects regarding the field of quaternized chitosans.

Enantioselective cytotoxicity of chiral polymer vesicles with linear and hyperbranched structures

Herein, we study the enantioselective cytotoxicity of vesicles self-assembled by optically active linear polymers (LNPs) and hyperbranched polymers (HBPs). Compared to HBP vesicles, LNP vesicles exhibit properties such as a higher surface charge density and more violent interaction with simulated biomembranes which results in larger cytotoxicity against HeLa cells. Specifically, racemic-LNP vesicles exhibit the largest cytotoxicity of all. More interestingly, there is no significant enantioselective dependence of HBP vesicles on the abovementioned properties. Overall, we proved that the cytotoxicity of vesicles is deeply related to chirality and topological-structures. This research is of great fundamental value for the design of novel bio-interface materials.

Lipophilic polyelectrolyte gel derived from phosphonium borate can absorb a wide range of organic solvents

Herein, we demonstrate a polyelectrolyte gel which can absorb a wide range of organic solvents from dimethylsulfoxide (DMSO, permittivity: ε = 47.0) to tetrahydrofuran (ε = 5.6). The gel consists of polystyrene chains with small amounts (∼5 mol%) of lipophilic electrolytes derived from triphenylphosphonium tetraaryl borate. The swelling ability of the polyelectrolyte gel was higher than that of the alkyl ammonium tetraaryl borate previously reported by us, and this is attributed to the higher compatibility with organic solvents, as well as the higher dissociating ability, of the triphenyl phosphonium salt. The role of the ionic moieties was additionally confirmed by post modification of the polyelectrolyte gel via a conventional Wittig reaction, resulting in a nonionic gel. Our findings introduced here will lead to a clear-cut molecular design for polyelectrolyte gels which absorb all solvents.