Microencapsulation of puerarin nanoparticles by poly(l-lactide) in a supercritical CO2 process

Puerarin nanoparticles were firstly prepared in the process of solution-enhanced dispersion by supercritical CO2 (SEDS) and then successfully microencapsulated by poly(l-lactide) (PLLA) in a modified SEDS process. By adding an organic non-solvent, an initial puerarin solution with a higher degree of saturation and lower concentration was obtained and applied in the SEDS process. The resulting puerarin nanoparticles were then suspended in PLLA solution and microencapsulated by PLLA in a modified SEDS process, where an ‘injector’ was employed in the particle suspension delivery system. The puerarin nanoparticles exhibited a good spherical shape, a smooth surface and a narrow particle size distribution with a mean particle size of 188 nm. After microencapsulation the puerarin–PLLA microparticles had a mean size of 675 nm, a drug load of 23.6% and an encapsulation efficiency of 39.4%; after a burst release at the first stage, the drug was released in a sustained process. Compared with the parallel study of a co-precipitation process, this microencapsulation process is a much more promising technique to prepare a drug–polymer carrier for a drug delivery system, especially for protein drugs.