Dextran hydrogels by crosslinking with amino acid diamines and their viscoelastic properties

Amine functionalized polysaccharide hydrogels such as those based on chitosan are widely examined as biomaterials. Here we set out to develop a facile procedure for developing such hydrogels by crosslinking dextran with amino acid diamines. The dextran-amino acid gels were formed by the addition of the amino acid diamines to a dextran and epicholorohydrin solution once it became homogeneous. This was demonstrated with three amino acid diamines, lysine, lysine methyl ester, and cystine dimethyl ester. Hydrogel networks with albumin entrapped were also demonstrated. These hydrogels were characterized by FTIR, SEM, rotational rheometry, swelling studies and cell biocompatibility analysis. These hydrogels showed the unexpected pH-responsive behavior of greater swelling at more basic pH, similar to that of an anionic hydrogel. This is uncharacteristic for amine functionalized gels as they typically exhibit cationic hydrogel behavior. All hydrogels showed similar biocompatibility to that of dextran crosslinked without amino acids

Editorial on Special Issue “Hydrogels for Biomedical Applications: New Knowledge”

Hydrogels are a network of hydrophilic polymers or lower molecular weight gelators capable of retaining a large quantity of water within three-dimensional networks without dissolving [...

Quinoline-2-thiol Derivatives as Fluorescent Sensors for Metals, pH and HNO

A tautomeric equilibrium exists for quinoline-2-thiol and quinoline-2(1H)-thione. Quantum mechanical calculations predict the thione is the major tautomer and this is confirmed by the absorption spectra. The utility of quinolone-2-thiol/quinoline-2(1H)-thione as a chromophore for developing fluorescent sensors is explored. No fluorescence is observed when excited at absorption maxima, however a fluorescence increase is observed when exposed to HNO, a molecule of import as a cardiovascular therapeutic. Alkylated quinoline-2-thiol derivatives are found to be fluorescent and show a reduction in fluorescence when exposed to metals and changes in pH

Antibacterial Silver Nanoparticle Containing Polydopamine Hydrogels That Enhance Re-Epithelization

A polydopamine polyelectrolyte hydrogel was developed by ionic crosslinking dextran sulfate with a copolymer of polyethyleneimine and polydopamine. Gelation was promoted by the slow hydrolysis of glucono-δ-lactone. Within this hydrogel, silver nanoparticles were generated in situ, ranging from 25 nm to 200 nm in size. The antibacterial activity of the hydrogel was proportional to the quantity of silver nanoparticles produced, increasing as the nanoparticle count rose. The hydrogels demonstrated broad-spectrum antibacterial efficacy at concentrations up to 108 cells/mL for P. aeruginosa, K. pneumoniae, E. coli and S. aureus, the four most prevalent bacterial pathogens in chronic septic wounds. In ex vivo studies on human skin, biocompatibility was enhanced by the presence of polydopamine. Dextran sulfate is a known irritant, but formulations with polydopamine showed improved cell viability and reduced levels of the inflammatory biomarkers IL-8 and IL-1α. Silver nanoparticles can inhibit cell migration, but an ex vivo human skin study showed significant re-epithelialization in wounds treated with hydrogels containing silver nanoparticles