Retentive device for intravesical drug delivery based on water-induced shape memory response of poly(vinyl alcohol): design concept and 4D printing feasibility

The use of shape memory polymers exhibiting water-induced shape recovery at body temperature and water solubility was proposed for the development of indwelling devices for intravesical drug delivery. These could be administered via catheter in a suitable temporary shape, retained in the bladder for a programmed period of time by recovery of the original shape and eliminated with urine following dissolution/erosion. Hot melt extrusion and fused deposition modeling 3D printing were employed as the manufacturing techniques, the latter resulting in 4D printing because of the shape modifications undergone by the printed item over time. Pharmaceutical-grade poly(vinyl alcohol) was selected based on its hot-processability, availability in different molecular weights and on preliminary data showing water-induced shape memory behavior. Specimens having various original and temporary geometries as well as compositions, successfully obtained, were characterized by differential scanning calorimetry and dynamic-mechanical thermal analysis as well as for fluid uptake, mass loss, shape recovery and release behavior. The samples exhibited the desired ability to recover the original shape, consistent in kinetics with the relevant thermo-mechanical properties, and concomitant prolonged release of a tracer. Although preliminary in scope, this study indicated the viability of the proposed approach to the design of retentive intravesical delivery systems.