DESIGN OF AN APPARATUS INCORPORATING A LINEAR VARIABLE DIFFERENTIAL TRANSFORMER FOR THE MEASUREMENT OF TYPE-III BIOADHESION TO CERVICAL TISSUE

The design and initial evaluation of a bioadhesive strength testing apparatus are reported. Measurement of adhesive strength is mediated via a linear variable differential transformer (LVDT). The apparatus, constructed from Perspex, consists of a movable platform with a pedestal to which the bioadhesive formulation is attached. Tissue is secured to a second, upper pedestal linked to the LVDT via a sensor. During the test procedure the platform is moved downwards at a predetermined rate controlled by the motor drive logic board. As movement occurs to the upper pedestal this can be detected by the output from the LVDT which is recorded potentiometrically. The force generated is measured by a previously calibrated spring contained within the sensor housing. Different calibrated springs can be used to increase OT decrease the sensitivity of the apparatus. Initial evaluation of the testing device was performed on a range of candidate bioadhesive film formulations. The effects on bioadhesion of varying the initial applied weight, mucus surface density, film thickness and film hydration were investigated. Excellent bioadhesion was achieved with the application of a dry sodium carboxymethylcellulose/ sodium carbopol film to cervical tissue with a surface mucus layer.