Preparation And Properties Of Hydroxyapatite/Silk Sericin Hybrid Microcapsules

The concept of microcarrier has got a great development once it was presented. Microcapsule which used for drug delivery shows a good potential in the filed of target and control release of antineoplastic drugs. Based on the real situation of the application, researchers put forward a series of methods to solve the problems that we facing at this moment, such as the stability of the structure, the biocompatibility of the material, and so on. The microcapsules with different forms have attracted more and more attention, the concept of hybrid microcapsules was introduced. It is known that there are many limits in the current method for preparing the hybrid microcapsules, so it is necessary to propose a simple and mild method to fabricate the hybrid microcapsules.In the present work, we use the nature silk sericin protein as the basic material, introducing the calcium ions to induce the self-assembly of the silk sericin. Then put the sericin microcapsules into the mineralized solution containing citric acid and incubated for different time. We analyzed the structure of the hybrid microcapsules by using SEM, TEM, FTIR and XRD. The release behavior of amylum from the microcapsules is investigated under different external environment, we can compare the release behavior to analyze the stability of the hybrid microcapsules. We also employed the DOX as the model of the antineoplastic drugs to investigate the encapsulation and release ability of the hybrid microcapsules, in addition, we can also evaluate the inhibiting effect of the system by cell culture. The research content and results as follow:1. The preparation of the hybrid microcapsules and the characterizationWe fabricated the hybrid microcapsules by putting the microcapsules into the mineralized solution with a pH of 7.4 at 37℃. The thickness of the mineralized shell of the hybrid microcapsules was regulated by controlling the time of the mineralized process. Afterword, the content of the mineralized shell was confirmed by XRD, it was hydroxyapatite. We use the CLSM to observe the hollow property of the hybrid microcapsules after dying the hybrid microcapsule with FITC and TTCH, it shows a basic property for the further use in the drug delivery system.2. The formation mechanism of the hybrid microcapsules and the propertyThe mineralized process was slow when the mineralized solution without citric acid, so we can infer that the citric acid play an important role in the process. The –COOH of the citric acid can chelae with calcium ions, and the –OH of the citric acid can combine the silk sericin protein to form nucleation sites. Along with the mineralized time, the crystal grows and reaches a stable structure. The amylun was introduced to investigate the ability of the hybrid microcapsules under pH and ionic strength, we analyze the release amount and the release rate of the amlyum, the results show that the mineralized shell of the hybrid microcapsules provide the protection of the structure. The hybrid microcapsules also show a good biocompatibility by cell culture, it promotes the growth and proliferation of the cells.3. We find the suitable experimental conditions to encapsulate the DOX, the encapsulate rate is 28%, it shows a similar release trend with the amylum under pH 7. We can find that the release amount of the DOX in the hybrid microcapsules is less than the situation of sericin microcapsules, it is good to perform the long-term release for the special propose.