Hydrogels for Mucosal Drug Delivery

Mucosal tissues are often a desirable site of drug action to treat disease and engage the immune system. However, systemically administered drugs suffer from limited bioavailability in mucosal tissues where technologies to enable direct, local delivery to these sites would prove useful. In this Spotlight on Applications article, we discuss hydrogels as an attractive means for local delivery of therapeutics to address a range of conditions affecting the eye, nose, oral cavity, gastrointestinal, urinary bladder, and vaginal tracts. Considering the barriers to effective mucosal delivery, we provide an overview of the key parameters in the use of hydrogels for these applications. Finally, we highlight recent work demonstrating their use for inflammatory and infectious diseases affecting these tissues.

Tuning the strength and swelling of an injectable polysaccharide hydrogel and the subsequent release of a broad spectrum bacteriocin, nisin A

Bacteriocins, which are antimicrobial peptides, are a potential alternative to current ineffective antimicrobial therapies. They can inhibit the growth of clinically relevant pathogens but their proteinaceous nature renders them susceptible to degradation and deactivation in vivo. We have designed injectable polysaccharide hydrogels for the controlled release of an incorporated bacteriocin, nisin. Nisin was encapsulated into these hydrogels which were composed of varying percentages of oxidised dextran, alginate functionalised with hydrazine groups and glycol chitosan. The nisin gels exhibited antimicrobial activity against Staphylococcus aureus up to 10 days. The incorporation of a deacetylated chitosan and the reduction of alginate-hydrazine could be used to tune the gel's swelling behaviour, strength and the subsequent release profile of nisin. Glycol chitosan also shows synergistic inhibition of S. aureus with nisin.

Biosorption equilibrium, kinetic and thermodynamic modelling of naphthalene removal from aqueous solution onto modified spent tea leaves

The object of this study was to investigate the feasibility of using modified spent tea leaves to remove naphthalene from its aqueous solution under batch mode. The effects on the removal process of physical factors, such as initial naphthalene concentration, contact time, biosorbent dosage, pH and temperature, have been evaluated. The equilibrium biosorption data were analyzed by the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R) adsorption isotherm models. These models provided a good fit to the experimental data, but the Langmuir isotherm model provided the best correlation (R2 = 0.993) to the experimental data. The biosorption kinetic data of naphthalene were analyzed by pseudo-first-order, pseudo-second-order and intra-particle diffusion and surface mass transfer kinetic models. These four kinetic models fitted the biosorption kinetic data well, but the pseudo-first-order kinetic model gave the best fit. The activation energy (E(a)) was found to be 15.89 kJ per mole and the thermodynamic properties of the biosorption process, such as the Gibbs free energy, enthalpy and the entropic change of biosorption, were also evaluated. It was established that the biosorption process was spontaneous, feasible and endothermic in nature.

Calcium alginate/dextran methacrylate IPN beads as protecting carriers for protein delivery

In the present study, mechanical and protein delivery properties of a system based on the interpenetration of calcium-alginate (Ca-Alg) and dextran-methacrylate (Dex-MA) networks are shown. Interpenetrated hydrogels beads were prepared by means of the alginate chains crosslinking with calcium ions, followed by the exposure to UV light that allows the Dex-MA network formation. Optical microscope analysis showed an average diameter of the IPN beads (Ca-Alg/Dex-MA) of 2 mm. This dimension was smaller than that of Ca-Alg beads because of the Dex-MA presence. Moreover, the strength of the IPN beads, and of their corresponding hydrogels, was influenced by the Dex-MA concentration and the crosslinking time. Model proteins (BSA and HRP) were successfully entrapped into the beads and released at a controlled rate, modulated by changing the Dex-MA concentration. The enzymatic activity of HRP released from the beads was maintained. These novel IPN beads have great potential as protein delivery system.