Preparation and properties of sodium polyphosphate/polyethylene glycol-modified chitosan–sodium alginate bilayer microspheres

Microspheres have a small specific surface area, so they can improve the drug encapsulation rate, achieve sustained release of drugs and provide a reference for the treatment of long-term wound healing. Ion cross-linking and curing method were used to prepare a core sphere with sodium alginate (SA) core spheres, the outer layer was coated with chitosan shell, and the inner and outer layers were modified by different concentrations of polyethylene glycol (PEG) and sodium polyphosphate (TPP). We characterized core spheres and bilayer microspheres by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), swelling experiments, drug sustained release, pH sensitive, etc. SEM showed that both the core spheres and the bilayer microspheres were dispersed spheres with a more uniform particle size distribution. The FTIR showed that PEG and TPP successfully introduced modified bilayer microspheres. Swelling experiments showed that the addition of PEG would reduce the swelling performance of core spheres, and the addition of TPP would improve the swelling properties of bilayer microspheres. Drug sustained-release experiments showed that the addition of PEG can improve the drug sustained-release performance of core spheres, and the addition of TPP can improve the drug sustained-release performance of bilayer microspheres. pH sensitivity experiments showed that the swelling degree of the bilayer microspheres increased with the increase in pH, and the shell of the bilayer microspheres had a good drug sustained-release effect at pH = 7.4 and 8.5.