The Preparation Of Poly (N-Isopropylacrylamide) Hydrogel Based On Gelatin And Their Application In Drug Delivery

Researchers were attracted by intelligent hydrogels for its environment responsibilities. Benefited from the lower critical solution temperature (LCST) similar with body temperature, poly (N-isopropylacrylamide) (PNIPAAm) hydrogel had wide application prospects in the fields of biology and medicine. N-maleyl gelatin (N-MAGEL) was prepared by acylation reaction between gelatin and maleic anhydride (MA) in this article. N-MAGEL-co-PNIPAAm hydrogel were prepared by free radical polymerization with N-MAGEL and NIPAAm as main ingredients. What’s more, N-MAGEL-co-PNIPAAm hydrogel crosslinked with Bis-acrylamide (N-MAGEL-Bis-PNIPAAm) were prepared by the same methods. The effects of the N-MAGEL/NIPAAm weighting ratios on the biology-chemical characteristics (thermo-responsive behaviors, water contents and drug release efficiency et al) of both hydrogels are analyzed.1. The 1H NMR spectrogram indicated that N-MAGEL was prepared by acylation reaction between gelatin and maleic anhydride. The isoelectric point of N-MAGEL had decreased significantly from 5.6 to 4.2 compared with gelatin. The degree of substitution (DS) of N-MAGEL reached maximum (96%) as the weighting ratios of MA and gelatin were 0.06:1.2. As the weighting ratios of N-MAGEL/NIPAAm ranged from 40:60 to 60:40, the prepared N-MAGEL-co-PNIPAAm hydrogels were solid and had certain mechanical strength at room temperature. Hydrogel with 45% percentage of N-MAGEL has highest equilibrium swelling ratio in deionized water at 25 ℃. The phase transition processes become slowly as adding N-MAGEL in N-MAGEL-co-PNIPAAm hydrogels.3. N-MAGEL-co-PNIPAAm hydrogel had good encapsulation efficiency (98%) and controlled release for bovine serum albumin (BSA) and 5-fluorouracil. The cumulative-release ratios of BSA entrapped in the hydrogels had an inverse relationship with weight percentage of N-maleyl gelatin at 25 ℃ and 37 ℃. The 5-fluorouracil released to PBS-in 2 h at 25 ℃ and it has no relationship with the weight percentage of N-maleyl gelatin in hydrogels.4. The thermosensitivity, responsiveness and control-release behaviors of hydrogels significantly increased by adding Bis to prepare N-MAGEL-Bis-PNIPAAm hydrogel. The thermosensitivity and responsiveness of N-MAGEL-Bis-PNIPAAm hydrogels kept well in spite of the weight ratios of N-MAGEL/NIPAAm reached 30:70.5. The encapsulation efficiency of N-MAGEL-Bis-PNIPAAm hydrogels for BSA and 5-fluorouracil were 82% and 90%, respectively. The encapsulation efficiency for BSA decreased with N-MAGEL increasing but it had no significantly influence on 5-fluorouracil. Increasing the weighting ratios of N-MAGEL and NIPAAm in hydrogel could increase the release rate and ratios of BSA, but it had no significantly influence on release of 5-fluorouracil.6. N-MAGEL-Bis-PNIPAAm hydrogels with higher weight ratios of N-MAGEL/NIPAAm degraded rapidly in PBS containing papain at 37 ℃.