BACKGROUNDIn some disease therapy, it is necessary to release multiple drugs continuously and orderly. This paper describes a technique for preparing a microparticle that can load two kinds of substances and release them at two different rates. RESULTSA core-shell structural microparticle was designed using liposome as core and hyaluronan/poly(N-isopropylacrylamide) (HA/PNIPAM) gel as shell. The core liposome keeps its vesicle structure after undergoing the whole crosslinking process. The microparticles are injectable at room temperature and become sticky when heated. The fluorescent loaded in the shell released 80% in 1h, while that in the core kept releasing for 35h. CONCLUSIONThe stability and function of liposomes are improved after being coated with a gel shell. Two kinds of fluorophores were successfully loaded into microparticles and released at two different rates. The main factors controlling the tracer diffusion are the microparticle properties, e.g. crosslink density and shell thickness. These microparticles can be used as injectable or implantable drug carriers by minimally invasive techniques. (c) 2012 Society of Chemical Industry