From cavitation to carrier: Ultrasound-assisted starch–hydrocolloid Pickering emulsions for potential drug delivery

Starch and Pickering emulsions consisting of the starch-hydrocolloid complex without surfactants have been found to be carriers for poorly water-soluble drugs and labile bioactive compounds. Acoustic cavitation caused by HIU may represent a possible sustainable technique for starch modification and formation of emulsions. Cavitation-induced mechanisms include the weakening of hydrogen bonds, chain breaking, decreased crystallinity, surface erosion, pore formation, the reduction of particle size and its surface charge, leading to improved interfacial activity of the starch stabilisers. Application of hydrocolloids such as chitosan, xanthan gum, pectin, and alginate may help to create interactions between molecules in ultrasonic fields. This review focuses on the recent advances in the field of ultrasound-assisted starch modification, starch-hydrocolloid interaction, Pickering emulsion formation and its application in pharmaceuticals. Structure and function relationship is demonstrated through the use of complex analysis techniques such as electron microscopy, dynamic light scattering and X-ray diffraction analysis. Ultrasound-activated optimised systems may generate small-sized droplets, high efficiency of encapsulation, high stability and favourable rheological characteristics. Despite all these advantages, its utilisation in the pharmaceutical sector encounters problems in terms of non-standardised and non-repeatable cavitation, scaling up, batch-to-batch variations and in vivo validation of ultrasound-activated Pickering delivery systems based on starches.