Preparation And Characteration Of Composite Microspheres With Multi-sensitive Properties

Multi-sensitive composite microspheres were fabricated via emulsion polymerization of Fe₃O₄, chitosan and N-isopropylacrylamide (NIPAm), then the adsorption of Bovine Serum Albumin (BSA) was studied.(1) The Fe₃O₄ nanoparticles were prepared by co-precipitation method and modified by oleic acid. Chitosan magnetic microspheres were then prepared by precipitation polymerization method. The results demonstrate that the concentration of the precipitant, the type of emulsifier and the modification of the iron oxide are the most effective parameters for the preparation of the microspheres. The SEM, FTIR and DLS results indicate that the microspheres are uniformly distributed and the diameter is about 150 nm. The magnetic test shows the microspheres are magnetic sensitive.(2) The chitosan magnetic microspheres then were embedded in NIPAm to prepare the multi-sensitive composite microspheres via emulsion polymerization. The magnetic, thermo and pH sensitive properties of the composite microspheres were investigated. From the magnetometer measurements data, the composite microspheres also have superparamagnetic property as well as fast magnetic response. The electromagnetically induced heating showsthat the composite microspheres could be heated up to 45℃in an alternating electromagnetic field. The size of the composite microspheres showed sensitive to pH and temperature. It is found that the lower critical solution temperature (LCST) of the composite microspheres is 29℃in water, and the LCST changes from 28℃to 32℃in pH range from 4.7 to 7.4.(3) The composite microspheres were loaded with Brovine serum albumin (BSA) as model drug by adsorption.The adsorption conditions such as pH, temperature, concentration of BSA were investigated by orthogonal experiment, and the adsorption kinetics was discussed. The orthogonal experiments show that the adsoption is pH and thermo sensitive. The results show that the quantity of immobilization is over 622 mg·g^-1. It confirms the potential applications of these microspheres for the targeted delivery of drugs.