A microtensiometer for the analysis of bioadhesive microspheres

Bioadhesive polymer microspheres are potential vehicles for the delivery of bioactive agents to mucosal tissues. Bioadhesive delivery devices could improve drug absorption, enhance bioavailability, and increase patient compliance by minimizing dosing regimens. Identification of bioadhesive materials is the first phase in developing bioadhesive drug delivery systems. Additionally, quantification and analysis of the bioadhesive event are essential to successful development of a new generation of adhesive delivery systems. A unique, microbalance-based instrument was developed to analyze bioadhesive forces between polymer microspheres and mucosal tissue segments. A contact angle analyzer, with a custom-made physiologic tissue chamber, was linked to a computer via the serial port. Software was used to modify the microbalance operation to behave as a microtensiometer with a sensitivity of 0.1 microN. After mounting a microsphere and tissue segment in the balance and adjusting the experimental settings, the instrument performs a tensile experiment and automatically determines the following parameters: compressive deformation, peak compressive load, compressive work, yield point, deformation to yield, returned work, peak tensile load, deformation to peak tensile load, fracture strength, deformation to failure, and tensile work. Using this device the authors identified several bioadhesive materials ideally suited for orally-delivered, controlled-release systems. GI-transit studies in rats showed strong correlation between increased GI-residence time and strong bioadhesive interactions.