The BEST Centre at the School of Pharmacy, QUB has extensively researched the physical and chemical properties of moisture-activated, bioadhesive polymers and their potential medical applications. A moisture-activated bioadhesive can be described as a potential material that, in the presence of aqueous fluid, forms adhesive interactions with biological substrates. Consequently, such systems are retained at the site of application for a prolonged period. These materials are physicochemically distinct from conventional pressure-sensitive adhesives as in the latter category of materials, adhesive bond failure occurs in the presence of aqueous fluid or very humid conditions. Moisture-activated bioadhesives may be readily fabricated as essential components of medical devices, medical sensors and drug delivery systems and will readily attach (and conform) to accessible sites of the body. Therefore, these materials have several applications in both medical and, in some instances, environmental sensor development.

Bioadhesive polymers may be derived from natural sources e.g. alginates, although much stronger bioadhesion is observed with synthetic polyvalent materials e.g. polyacrylic acid derivatives are currently under investigation as components of sensor systems and electrically –modulated drug delivery devices within the BEST Centre at QUB. Carbopols are commercially available as powders of varying viscosity grades, and are readily soluble in water. At relatively low aqueous concentrations (<2% w/w) a clear gel is formed after neutralisation of the carboxylic acid functional groups of polyacrylic acid. These gels possess moderate bioadhesive properties, however, if dried, hydrogel polyacrylic acid films may be formed that are strongly bioadhesive (in the presence of aqueous fluids). The bioadhesive properties of the film are dependent on a variety of factors including film hydration: surface hydration, pH and polymer rheology (viscoelasticity).

A bioadhesive polyacrylic acid hydrogel film formulation has been successfully employed in a novel planar sodium-selective electrode, designed for the rapid diagnosis of cystic fibrosis. The bioadhesive properties of the hydrogel formulation have ensured optimal adhesion of the electrode to the skin, and also self-adhesion of the multiple components (layers)of the design. In addition, the rheological and dielectric properties of the hydrogel component ensured good electrical conductivity throughout the electrode. These combined factors have ensured enhanced product performance in comparison to designs devoid of such hydrogel components. Current research is ongoing to further develop bioadhesive, electrically conductive drug delivery systems for controlled pulsatile drug release.