Research On The Synthesis Of Environmental PH-responsive Polyurethane And The Fluorescence

Polyurethane has good biocompatibility and physical properties, the introduction of a variety of different functional groups, has been widely applied in the biomedical field. In recent years, the study of PU drug controlled release has attracted great interest. By selecting suitable isocyanate monomer and polymer polyol, combining stimulus responsive material, the preparation of polyurethane with stimulus responsive drug carrier, in the field of medicine and medical engineering provides a broad application prospect.At first, this paper using the condensation reaction principle synthesized a series of pH-responsive fluorescent MPEG-terminated polyurethane multi-block copolymers, and characterized by many methods. These polyurethane multi-block copolymers consisted of1,6-dissocyanate hexamethylene (HDI) and poly (ethylene glycol)(PEG),1,4-bis (hydroxyethyl) piperazine (HEP), fluorescein isothiocyanate (FITC), methoxypolyethylene glycols (MPEG) and dimethylol propionic acid (DMPA). Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (’H NMR) spectral analysis results indicate that the structure of the product was consistent with the expected. pH-sensitive capacity of pH-responsive was examined by acid-based titration. The fluorescent dye fluorescein isothiocyanate (FITC) was conjugated with polyurethane and the obtained polymer was measured by ultraviolet visible spectroscopy (UV-vis) and fluorescent spectroscopy. Also showed that the fluorescence intensity is different under different pH at the same time, the greater the pH and the stronger fluorescence intensity. The particle size analysis results show that with the increase of pH values the particle size increased gradually, and the distribution of particle size is monodispersity.Second, using N, N’-dicyclohexylcarbodiimide (DCC) and4-dimethyl amino pyridine (DMAP) activated the free carboxyl groups in the polyurethanes, make its successful grafting the MPEG, and their fluorescence and buffer in the self-assembly behavior were studied in this paper. The experimental results showed that the series of polyurethane graft copolymer had well fluorescence properties. The transmission electron microscopy (TEM) photographs can be seen that the polyurethanes could self-assembly in buffer solution at pH7.4to form micelles. The in vitro cytotoxicity test results showed that the two series of polyurethanes had low cytotoxicity. To sum up, the polymeric micelles can be used as a biological medical carriers.