| Objective:Thermosensitive hydrogel is a kind of intelligent hydrogel, witch undergo a sol-to-gel transition in response to temperature changes. At low temperature, It is a solution state, but the hydrogel can gradually transform into solid or semi-solid gel when the temperature is increased. There are a part of hydrogels which the low critical solution temperature is close to the temperature of perple and those can be used as drug carriers in biomedical.There are still many shortcomings when the temperature-hydrogel used as drug carriers, For example:gel time is relatively long; Drug incorporated difficulty; The protein drug is easy to inactivate; Release time is short and poor degradation performance. In this study,we developed the thermosensitive chitosan(CS)/ genipin(GP)/genlatin(G)/β-glycerophosphate(β-GP) hydrogel which was applied physical crosslinking method, and confirmed the physicochemical properties of chitosan. We also explored drug release in vitro using bovine serum albumin(BSA) as a model protein and 5-fluorouracil as small molecule model drug, which provided a theoretical basis for the controlled-release carrier of drug.Methods:The physics crosslinking method was applied to prepared six different ratios of CS/GP/G/β-GP temperature sensitive hydrogels. Observed the process of the sol-to-gel under the room temperature and 37℃; Determined the gel time at 37℃ by inversion; Studied the structure of the samples used fourier transform infrared spectroscopy(FT-IR); Obsreved the microscopic structure of the sample by the transmission electron microscopy(SEM); Determined the degradation of the samples by Lysozyme experiment; Finally, we studied the release rule in vitro used bovine serum albumin(BSA) and 5-fluorouracil as a model drug.Resultes:1. The hydrogel we obtained was translucent flowable state at room temperature, as the content of chitosan increase,its liquidity weakened; As the content of β-glycerophosphate increase, its liquidity enhanced. After at 37℃ for a period of time, hydrogel changed into a dark green solid gel, and uniformly mixed.2. Determination of the gel time by inversion method showed that with the content of chitosan and β-glycerophosphate increase, the gel time gradually shortened. When the content of chitosan was 1.6% and the content of β- glycerophosphate was 12%,the gel time was longest(126s); When the content of chitosan was 2.4% and the content of β- glycerophosphate was 16%,the gel time was Shortest(50s)3. Studied the internal structure of the hydrogel by transmission electron microscopy showed that chitosan hydrogel was a porous three-dimensional network structure interworking. With the content of chitosan increase, the internal structure of hydrogel became more compact, the mesh structure reduced, the penetrating of mesh was poor. With the content of β-glycerophosphate increases, the mesh diameter significantly reduced, the mesh number was increase, the penetration of mesh was increase.4. By comparing the infrared spectra of chitosan、chitosan/β-glycerophosphate/ gelatin and chitosan/β-glycerophosphate/gelatin/genipin showed that the four substances inside the hydrogel had crosslinked copolymer.5. The lysozyme experiment results showed that the hydrogel have some degradation performance and the rate was moderate; The degradation rate of the hydrogel will significantily accelerate under the action of lysozyme. Because of the presence of hydrogel skeletal structure, the quality of the final remaining was essentially same.6. The release results of BSA showed that he release of BSA had two stages in PBS solution at 37℃, In the period between 0-25h was quick release stage. With time, the release rate of the drug tended to constant the total release time was 170h. Increase the content of both of chitosan and β-glycerophosphate could slow down the rate of release of BSA. The content of chitosan was more significan for the drug release rate. Meanwhile, invrease the content of chitosan and β-glycerophosphate also could reduce the final total release ratio. When the content of chitosan was 1.6%, β-glycerophosphate was 12%,the total emissions was highest(89.56±0.98%); When the content of chitosan was 2.4%, β-glycerophosphate was 16%,the total emissions was highest(93.31±0.67%), the total emissions was lowest(76.02±1.1%). the results of curve fitting used Ritger-Peppas eqution showed that the release mechanism in vitro followed Fickian transport.7. The release results of 5-fluorouracil showed that the release of 5-fluorouracil had two stages in PBS solution at 37℃. In the period between 0-16h was quick release stage,with time,the release rate of the drug tended to constant, the total release time was 72h. Increase the content of chitosan could slow down the release rate of 5-fluorouracil; But intreased the content of β-glycerophosphate had a smaller impact on the rate of drug release. When the content of chitosan was 1.6%, β-glycerophosphate was 12%, the total emissions was highest(93.31±0.67%); When the content of chitosan was 2.4%,β-glycerophosphate was 16%, the total emissions was highest(93.31±0.67%), the total emissions was lowest(87.54±0.20). the results of curve fitting used Ritger-Peppas eqution showed that the release mechanism in vitro followed Fickian transport.Conclusion:1..The six different proportions of CS/GP/G/β-GP hydrogels prepared applied physics crosslinking echnology had good performance. It could present as a liquid sol state at room temperature or low temperature, but when temperature reaches 37℃, It will present as the solid sol. the gel time of chitosan thermosensitive hydrogel was short.and the hydrogel can meet the application as a drug carrier.2. The hydrogel was the product of four substances cross-linked; the internal structure is compact and homogeneous, and the surface was relatively smooth.3 The hydrogels had better performance on biodegradable,;The rate of degradation will speed up under the action of enzymes.4. In summary,when the content of chitosan was 2.0%, β-glycerophosphate was 16%, hydrogel had better mobility, Cumulative release rate was high, the release rate is more gradual, the time of release BSA was longer. So It is the best ratio for released protern drugs. This study has provided a suitable carrier for protein drug to safety incorporation and controlled release.5. In summary,when the content of chitosan was 2.4%,β-glycerophosphate was 16%, the gel time of the hydrogel was short, he release rate is more gradual, the time of release 5-Fluorouracil was longer. So It is the best ratio for released Small molecule drug. |
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