Study On Drug Delivery System Of Gelatin Microspheres For Animal

Using the emulsification method, microspheres containing metamizole sodium,ciprofloxacin lactate and norfloxacin lactate were prepared, with gelatin as polymer coatingmaterials. The drug content and release characteristic of gelatin-ciprofloxacin lactatemicrospheres were analyzed, which were crosslinked with different cross-linker, cross-linkerconcentration and crosslink time. The optimum procedure of microspheres preparation was established by single factor test.The morphology of the unloaded microspheres was examined by optical microscopy. Atregular intervals, the swelling properties of gelatin microspheres were investigated bymensurating the diameter of microspheres immersed in PBS. Drug trapping efficiency and drug release rate were influenced by cross-linker, cross-linkerconcentration and crosslink time. Three kinds of cross-linker: oxidized starch, formaldehydeand glutharaldehyde were used. The results indicated that oxidized starch affected themorphology of the microspheres, and augmented the burst release. In contrast, formaldehydeand glutharaldehyde gave smooth and uniform surface of microspheres, while the amount ofdrug loaded in the microspheres were decreased. Regardless of the conditions of gelatinmicrospheres crosslinking, there was an initial period of rapid drug release in all cases. Theamount of drug released in the initial hours increased with the cross-linker concentration, butdecreased in the following time. Finally, formaldehyde was chosen as cross-linker (at2ml/200mg uncrosslinked microspheres crosslinking for 4 hours) in our experiments. The drug content in the microspheres was determined by crush-sonicate method to be 2.97% for metamizole sodium, 10.34% for ciprofloxacin lactate and 11.29% for norfloxacinlactate. In this paper, we found out the factors induced lower drug content and pointed outthat oil phase alteration could overcome the problem. In the simulated environment of thein vivo deposition of the microspheres, drug was released from formaldehyde treated gelatinmicrospheres more than 90% of the total amount of the encapsulated drug during 48 h.