Characteristics of vitamin C encapsulated tripolyphosphate-chitosan microspheres as affected by chitosan molecular weight

摘要

In this paper,the effect of chitosan molecular weight on the characteristics (size,encapsulation efficiency,zeta potential,surface morphology and release rate)of vitamin C encapsulated tripolypho-sphate cross-linked chitosan (TPP-chitosan)microspheres.The molecular weight of chitosan had a noticeable influence on the size,encapsulation efficiency,zeta potential,surface morphology and controlled release behaviour of the vitamin C encapsulated TPP-chitosan microspheres.The mean particle size and encapsulation efficiencies of TPP-chitosan microspheres were 3.1,4.9 and 6.7 mu rn and 67.25,60.43 and 52.74% for the microspheres prepared using low,medium and high molecular weight chitosan,respectively.All the TPP-chitosan microspheres (low,medium and high molecular weight)had positive charge on their surface.The zeta potential of the TPP-chitosan microspheres prepared using low,medium and high molecular weight chitosan was 41.25,40.84 and 39.13 mV,respectively.The particle sizes of TPP-chitosan microspheres increased with increases in chitosan molecular weight.Molecular weight of chitosan did not affect significantly the % yield of TPP-chitosan microspheres prepared by spray-drying.The influence of chitosan molecular weight on the surface morphology of vitamin C encapsulated TPP-chitosan microspheres was examined by scanning electron microscopy (SEM)and transmission electron microscopy (TEM).It was observed that,as the molecular weight of chitosan increases,TPP-chitosan microspheres with uniform spherical shape could be obtained.The physical state of vitamin C (amorphous or crystalline)in TPP-chitosan matrix was studied by X-ray diffraction (XRD)and it was found that vitamin C is dispersed at the molecular level (amorphous)in the TPP-chitosan matrix.Release rate of the vitamin C from TPP-chitosan microspheres was significantly affected by the chitosan molecular weight.The release rate decreased with increase in the chitosan molecular weight.The release of vitamin C from TPP-chitosan microspheres followed Fick's law of diffusion.