Ultrasonic welding method to fabricate polymer microstructure encapsulating protein with minimum damage

Abstract

Ultrasonic welding can be used with micromolding to fabricate polymeric microstructures. We investigated whether these techniques are useful in fabricating polymeric microstructures from polymeric microparticles that encapsulate thermally sensitive compounds. We used a spray-drying method to prepare biodegradable polymer microparticles encapsulating the thermally sensitive compound, BSA and Vitamin B. The resulting polymeric structures were less than 7 μm in diameter. Morphological changes after increasing periods of application of ultrasonic energy could be categorized into four phases: loose connecting, dense connecting, porous packing, and solid structures. The stability of polymer structures encapsulating BSA was tested after increasing periods of applied energy. Few changes were seen after typical periods (under 1 min), but 10 % of BSA was denatured after 80 s (considered to be harsh conditions). More work is needed to optimize this novel method of microfabrication for delivery of other heat-sensitive protein and growth factors and the biological function of protein also need to be investigated in next experiment. However, it appears to a promising means of fabricating polymer microstructures for cell chips, tissue engineering, and drug delivery, in which protein must be encapsulated with minimal denaturation.