ABSTRACT
Photochemical processes offer the possibility of preparing functional hydrogels under green conditions that are compatible with both synthetic and natural polymers. In this study, chitosan-based poly(ethylene) glycol (PEG) were successfully synthesized under light irradiation in aqueous medium. Kinetic studies under irradiation showed that less than 2 min were necessary to obtain fully cross-linked networks. Thermomechanical analyses and swelling experiments indicated that introduction of chitosan overall weakens the hydrogel network but can create domains of higher thermal stability than the PEG-alone structure. The resulting chitosan-PEG hydrogels demonstrated a tremendous inhibition (100%) of bacterial growth (Escherichia coli and Staphylococcus aureus). After 6 months' ageing, one of the hydrogels preserved a high antifouling activity against Escherichia coli. This interesting result, which could be correlated with the network features, demonstrates the strong potential of these photochemical methods to obtain robust bio-functional materials.
Subject(s)
Anti-Bacterial Agents/pharmacology , Chitosan/pharmacology , Hydrogels/pharmacology , Polyethylene Glycols/pharmacology , Anti-Bacterial Agents/chemical synthesis , Anti-Bacterial Agents/radiation effects , Bacterial Adhesion/drug effects , Biofouling/prevention & control , Chitosan/analogs & derivatives , Chitosan/radiation effects , Escherichia coli/drug effects , Hydrogels/chemical synthesis , Hydrogels/radiation effects , Kinetics , Microbial Sensitivity Tests , Polyethylene Glycols/chemical synthesis , Polyethylene Glycols/radiation effects , Polymerization/radiation effects , Staphylococcus aureus/drug effects , Transition Temperature , Ultraviolet Rays , Viscoelastic Substances/chemical synthesis , Viscoelastic Substances/pharmacology , Viscoelastic Substances/radiation effectsABSTRACT
Herein, we report on the preparation of ultra-low sized (<100â¯nm in diameter) biodegradable polymeric capsules for potential applications as nanocontainers in antibiotic therapy. Hollow nanospheres based on the chitosan/poly(acrylic acid) pair are elaborated via (i) the layer-by-layer technique using gold nanoparticles (20 and 60â¯nm in size) as sacrificial templates, (ii) loading with amoxicillin, a betalactam antibiotic, and (iii) removal of the gold core via cyanide-assisted hydrolysis. Size, dispersity and concentration of the resulting nanocapsules are easily tuned by the nanoparticle templates, while wall thickness is controlled by the number of polyelectrolyte bilayers. Electrostatic interactions between the protonated amine groups of chitosan and the carboxyl groups of poly(acrylic acid) act as the driving attraction force allowing easy and fast design of robust and well-ordered multilayer films. Successful hydrolysis of the gold core is evidenced by time-dependent monitoring of the gold spectroscopic signature (absorbance at 519â¯nm and 539â¯nm for the gold nanoparticles with 20 and 60â¯nm, respectively). Crosslinked capsules are also prepared through crosslinking of the chitosan chains with glutaraldehyde. Chitosan-based nanocapsules are finally evidenced to be promising drug delivery vehicles of amoxicillin trihydrate with tuneable properties such as entrapment efficiency in the range of 62-75% and 3.5-5.5% concerning the drug loading.