Study of Manipulative In Situ Pore-Formation upon Polymeric Coating on Cylindrical Substrate for Sustained Drug Delivery.

Herein, the micro-porous polylactic acid coating applied on the surface of the cylindrical substrate is fabricated by a novel in situ pore-formation strategy based on the combinational effect of breath figure (BF) and vapor-induced phase separation (VIPS) processes. Under the condition of high environmental humidity, solvent pair of chloroform and dimethylformamide is employed for post-treatment onto pre-formed PLA coating to induce the pore-formation following the mechanism of BF and VIPS, respectively. A composite porous structure with both cellular-like and bi-continuous network morphologies is obtained. By tunning the experimental factors including the ratio of the solvent pair, environmental humidity, and temperature, morphological manipulation upon the pore morphology can be facilely achieved based on the control of mechanism transition between BF and VIPS. Paclitaxel is used as a model drug and loaded into the porous coating by the wicking effect of post-immersion. Coatings with different morphological features show varying drug loading and release capacities. The 28-day release test reveals dynamic release profiles between different coating samples, with the total release rate ranging from 35.70% to 79.96%. Optimal loading capacity of 19.28 µg cm^-2 and 28-day release rate of 35.70% are achieved for the coating with composite BF-VIPS structure. This research established a cost-efficient strategy with high flexibility in the structural manipulation concerning the construction of drug-eluting coating with the feature of manipulative drug delivery.