| Polyethylene glycol (PEG) is amphipathic polymer which is soluble in water and most of organic solvent, with the properties of good biocompatibility, innocuity, nonimmunogenicity and no accumulation in body. As the most frequently used substance in tissue engineering, PEG enjoys the bright application prospect in biomedical field, such as drug controlled release system, bond repair, carrier of cell growth factor and biosensor.In this paper, copolymer hydrogel microspheres were prepared by dispersion polymerization without organic solvent, with polyethylene glycol diacrylate(PEG-DA, approved by Food and USA's Drug Administration) and 2-hydroxyethyl methacrylate(HEMA) as comonomer, chitosan(CS) as reaction medium and costabilizer, polyvinylpyrrolidone (PVP) as steric stabilizer and benzoy peroxide(BPO) as initiator. The composition of copolymer hydrogel microspheres was characterized by fourier transform infrared spectrometer(FT-IR), morphology and size of freeze-dried hydrogel microshpheres were examined by using scanning electron micrographs(SEM),and particle size distribution was obtained using dynamic light scattering particle size analyzer. The effects of polymerization parameter on morphology,partilcle size and polydispersity index (PDI) of microspheres were investigated, listed as reaction time, reaction temperature, molecular weight of PEG-DA, mass ratios of monomers, stabilizer concentration, initiator concentration and chitosan concentration. The optimum technological condition (recommended recipe) was determined as 1% of CS concentration (in first solution),60/40 in mass ratio of PEG-DA/HEMA,200(PEG) of PEG-DA molecular weight,2% of BPO concentration(relative to mass of monomer),2% of PVP concentration(relative to mass of monomer),80℃of reaction temperature and 24h of reaction time, hydrogel microshpheres were obtained with 3.26μm in size and 1.03 in PDI.Bovine serum albumin (BSA) as protein-drug model, the effects of several factors on amount of loaded BSA in hydrogel microspheres were investigated, such as loading time, and environmental temperature, BSA initial concentration, ionic concentration, pH value of buffer solution, composition of hydrogel microspheres, size and size distribution. Moreover, the preliminary study on BSA adsorption kinetics for hydrogel microspheres was made. At last, the effects of release time, pH value of buffer solution, environmental temperature, composition of hydrogel microspheres, size and size distribution on released ratio of BSA were studied. The optimum loading conditions were 60/40 in mass ratio of PEG-DA/HEMA, 1.2mg/ml of BSA initial concentration, 10h of loading time,30℃of environmental temperature,4.9 of environmental pH value, O.Olmol/L of ionic concentration, and 124.6mg/g of amount of loaded BSA was obtained. The optimum release conditions were 60/40 in mass ratio of PEG-DA/HEMA,7h of release time,37℃of environmental temperature,7.4 of environmental pH value, and 59.1% of release ratio was obtained.The study, on preparation technology for PEG-DA/HEMA copolymer hydrogel microspheres and BSA release Properties, shown that PEG-DA/HEMA copolymer hydrogel microspheres have certain potential for application in embedding cartilage cell and loading bone morphogenetic protein(BMP, grown factor), and provided a scientific basis for PEG-based microhydrogel moving into specific clinical application. |
