A study on chitosan coated polycaprolactone (Ch-pcl) microspheres prepared via double smulsion solvent evaporation method

Abstract

Polycaprolactone coated with chitosan microspheres have the potential to be used as delivery systems and biosensors. Polycaprolactone (PCL) is, however hydrophobic, to improve the biofunctional and potential immobilization of PCL polymer, chitosan-coated PCL microspheres (MSs) were prepared using a double emulsion solvent evaporation method. Different particle sizes were prepared by altering five parameters. When the MSs were prepared using oil to water phase ratio or oil fraction (ϕo) of ϕo = 0.95 to ϕo = 0.38, the MSs average diameter (Dv) reduced from 3.86 to 3.53 µm along with its coefficient of variation (CV), reduced from 18.1 to 12.3 respectively. The MSs prepared with higher polymer concentration of 6 wt.% shows higher Dv (4.51 µm) and CV (25.2) compared to 1.2 wt.% of PCL, which Dv = 3.86 µm with CV of 18.1. The first homogenizer speed (H1) was increased in order to prepare smaller MSs. When H1 increased from 6000 to 10000 rpm, MSs Dv reduced from 3.86 to 3.45 µm along with its CV reduce from 18.1 to 16.6 for ϕo = 0.95. It is also the same case for ϕo = 0.52, where the Dv reduced from 3.70 to 3.19 µm and its CV reduce from 25.8 to 25.2. The effect of NaCl concentration on MSs preparation shows, higher NaCl concentration (1.8 wt.%) produced smaller Dv (Dv = 3.86 µm) compared to lower concentration of 0.9 wt.%, produced Dv = 4.51 µm for ϕo = 0.95. The trend also follows when the MSs were prepared for ϕo = 0.52. The delay in adding the NaCl shows distinct effect on Dv. For both 0.9 and 1.8 wt.% of NaCl, the Dv increase from 4.51 to 6.40 µm and 4.31 to 6.17 µm respectively. Therefore, the targeted Dv for certain application could be achieved by altering the parameters above. Finally, to study the Ch-PCL potential as enzyme immobilizer, horseradish peroxidase (HRP) was used to be immobilized on to the Ch-PCL MSs. After 7 days, the HRP enzyme still show 51% activity under robust storage condition.