Controllable fabrication of biodegradable Janus and multi-layered particles with hierarchically porous structure.

We introduce a facile strategy to synthesize both Janus and multi-layered microparticles with hierarchically porous structure by adopting a simple oil-in-water emulsion technique. Incorporation of a minute quantity of non volatile poor solvent such as mustard oil into the emulsion comprising of biodegradable polymers such as Poly(lactic-co-glycolic acid)(PLGA) and Poly(l-lactic acid)(PLLA), led to a precisely controlled phase separation. This resulted in the formation of Janus or multi-layered particles with hierarchically porous structure depending on the amount of mustard oil and viscosity/crystallinity of the polymers employed. No additional toxic porogen needs to be added to induce the porosity. The mechanism of formation of various architectures was explored with the supportive evidences primarily from in situ optical microscopy along with interfacial tension measurements. Moreover, we also show the potential application of these unique particles in delivering multiple actives by encapsulating and releasing the dual actives (antibacterial and antioxidant) in controlled fashion for prolonged period of time (60 days). The release profiles of the dual actives were found to be influenced by the porosity as well as architecture of the particles.