Sustainable production of porous chitosan microparticles by energy-efficient membrane emulsification

In drug delivery, it is common to use porous particles as carrier media, instead of dense particles, due to their high specific surface area and available entrapment volume, which allows a higher amount of drug to be encapsulated and then released. Chitosan microparticles are extensively used in drug delivery, but porous chitosan microparticles are scarcely reported. In this work, the preparation of porous chitosan microparticles using membrane emulsification is addressed, a technology that involves mild operating conditions and less energy consumption than traditional methods (such as ultrasound), and with higher control of the particle size. The dense structure is obtained by a water-in-oil emulsion. The porous structure is obtained by a gas-in-water-in-oil G/W/O double emulsion, where argon bubbles get entrapped in an aqueous chitosan solution that is further emulsified in a paraffin/petroleum ether mixture. Porous chitosan particles were obtained with sizes of 7.7±1.6 μm, which was comparable with dense chitosan particles (6.2±2.3 μm). The pore structure was optimised by varying the argon flow rate, being optimized at 0.24 L.h-1. The impact of drug loading by adsorption or encapsulation, and of the drug release behaviour when using porous and dense particles were assessed, using the protein bovine serum albumin (BSA) as a model drug. The results showed that by encapsulating BSA the loading efficiency was above 95% for both types of particles, with the release being slightly slower for the dense particles. As for the adsorbed BSA, the loading efficiency was significantly higher for porous particles – 70% - against the 40% for dense particles. Porous chitosan particles were successfully obtained using the membrane emulsification technology and showed that these carriers are advantageous regarding drug loading and release.