Research On Release Properities Of Halloysite Nanotubes And Preparation And Properityes Of Its Nanocomposite Gel With Gelatin

Gelatin, originated from collagen treated with acid or alkali, is a biocompatible and biodegradable product which is generally recognized as a safe material. Halloysite nanotube (HNTs) is a kind of natural micro-tubular nanomaterials composed of aluminosilicate. It has the advantage of wide sources and low price, and there are a lot of hydroxyl groups on the edges or surface. Its special structure determines HNTs with excellent performance in many applications. The nanocomposite gels with dispersed nano-materials not only maintain the functional properties of nanomaterials, but also mix the rigidity, dimensional stability and thermal stability properties with the wet gel, which can significantly improved the mechanical properties, optical properties, thermal stability or other relative properties of gel. The nanocomposite gel is considered as a kind of promising new materials.HNTs were used as a drug carrier and the drug release properties of HNTs were researched in this paper. HNTs were used as a precursor and chitosan (CTS) was used as a surface modification agent to prepare non-covalent modified HNTs (CTS-HNTs), and then the CTS-HNTs were mixed with the gelatin solution to obtaine gelatin-HNTs nanocomposite gel. The factors affecting the preparation of nanocomposite gel were investigated, and the swelling properties, textural properties, rheological properties were studied. The nano structure of the composite gels was characterized too. The results showed that:The drug release properties of HNTs discoveried that HNTs had a blocking effect on drug release and the capacity for the time release of drugs. Release profiles of drugs from drug loaded HNTs in buffer pH1.7and7.4simulated in the physiological environment founded that the drug release rate of drug loaded HNTs in the buffer pH1.7was faster than that of in the buffer pH7.4in initial release. The loading solvent influenced the drug release too, the study showed that compared to the release profiles of drugs from drug loaded HNTs with saturated chlorhexidine solution of deionized water,10%and50%ethanol/aqueous solvent as a drug loading solvent, drug loading was higher at higher ethanol to water ratios and the release profiles became more linear, but the cumulative release rate didn’t increased with higher ethanol to water ratios. And10%ethanol/aqueous solvent as a drug loading solvent can obtained more ideal effection. Further, the solubility of the drug also affected the release, the lower solubility of drug released faster in initial release time. In order to reduce the burst, the drug loaded HNTs were coated with chitosan to prepare CTS-drug loaded HNTs. The cumulative release rate of CTS-drug loaded HNTs reached minimum when mHNTs:mCTS=1:0.2; appropriate amount of crosslinking agent can reduce the cumulative release rate because crosslinking made CTS film wrapped up in HNTs dense which can reduce drug molecular infiltrate in the tube.The gelatin-HNTs nanocomposite gel was prepared by solution blending method. The study found that under the process conditions of mHNTs:mCTS:mgelatin=0.2:0.3:10, pH=6and the heating temperature is65℃, can obtain nanocomposite gel with good swelling and mechanical properties, wherein the swelling rate (SR) was7.63g/g, hardness was902g, springiness and cohesiveness were13.35and0.51. HNTs were dispersed in the gelatin by SEM analysis; the rheological analysis was found that storage modulus (G’) was always greater than the loss modulus (G") within the range of0.1-20Hz, showing the typical characteristics of the gel with a three-dimensional network structure. After adding HNTs, the storage modulus and loss modulus of the system rapidly increased and increased with the contents of HNTs. It may be due to the interaction between HNTs and the gelatin matrix, playing a role similar to the physical crosslinking which enhanced three-dimensional network structure of the system, improved the mechanical properties of the gel. FT-IR characterization was further proved that the interaction between HNTs and gelatin matrix was hydrogen bonding, establishing a secondary three-dimensional network structure; SEM characterization was proved that HNTs can be evently dispersed in the gelatin matrix but gathered to some extent.