Can sonication increase the release from alginate capsules?

The objective is to investigate the influence of sonication on the mechanical and release properties of capsules made of a soft membrane in hydrogel. If high sonication may lead to the capsule rupture induced by a fatigue phenomenon, no influence of sonication is measured on the capsule mechanical properties below the breakup threshold. The release is studied by sonicating capsules filled with blue dextran suspended in an aqueous solution. The step in mass release that results from sonication is found to be proportional to the duration time and pressure pulse of sonication. The passive release subsequent to a low-intensity sonication is on average identical to the one measured on non-sonicated capsules. From these results, one can hypothesize that the high frequency ultrasonic stimulation leads to high pressure gradients on the capsule that drive out the encapsulated molecules. Sonication could also lead to a higher porosity of the capsule membrane; this phenomenon would be reversible, as the membrane overall recovers its physical and mechanical properties after sonication.