Study On The Size Control And Mechanism Of Gelatin Microencapsulation And Nanoencapsulation

Micro/nano-encapsulation technology is using a polymer film-forming material as the drug package to form a closed core-shell structure.Typically,the size distribution ranging from 1μm to 1000 μm is known as microcapsules;particle size distribution in 1-1000nm is called nanocapsules.With many advantages,Micro/nano-capsules have become a hot topic,and have broad application prospects in the chemistry and new drug system.With further research,preparation technology of micro/nano-capsules continuously enriched and improved,more and more functional film-forming materials appear.Gelatin is a natural polymer material degradation by the skin of animals bone collagen,which has high biocompatibility,wide variety of sources.Gelatin is the most common wall material of the microcapsules.Gelatin micro/nano-encapsulated technology is relatively mature,studies tend to focus on its application,so control of particle size and encapsulated mechanism so far is not clear,and lack of systematic research.Particle size is one of the important criteria for evaluating the micro/nano-capsules’ quality.It affects the distribution of drugs in the body.Some specific applications require the the precise particle size.This article aims at analysising factors affecting the the particle size in preparation by preparing target particle size of micro/nano-capsules,inquirying into mechanism of gelatin microencapsulation and nonaencapsulation.The details are as follows:1.To develop the self-healing coatings for cars,we use gelatin as wall material,linseed oil as core material,to prepare the linseed oil microcapsules at target particle size of about 20μm by single coacervation method.Exploration by small test,we take orthogonal test to optimize the preparation process and successfully get an average particle size of 19μm linseed oil microcapsules.Then we proved that the prepared microcapsules is core-shell structure by microscopic images and infrared spectroscopy,the core material linseed oil was wrapped in capsules.2.Enlarging the preparation on the basis of a small sample of the process,we divide the process of preparing microcapsules into three stages,which are linseed oil emulsification,coacervation and cured.We examined the impact to particle size of each stage of the preparation of linseed oil microcapsule,summed up the law of preparing linseed oil microcapsules,explored the mechanism of microencapsulation.The results are as follows,particle size of core material determine the size of the microcapsules.Best emulsification result is 4%gelatin solution,30min,460r/min,45℃.Gelatin concentration has a significant impact,it plays a decisive role in the optimal emulsifying conditions.The experiments intuitively display the microcapsules encapsulated mechanism.With flocculant intervention,gelatin phase began to separate,and gradually wrapped in core material,the optimum system concentration of Na2SO4 was 8.9%,and adjusting pH to gelatin isoelectric point will help the precipitation and deposition of wall material,the pH value of gelatin isoelectric point in this work is 4.44;In the process of forming,with the gelatin precipitation,core material aggregation,microcapsules goes from amorphous shapes to spherical shapes,coacervation speed should not be too high,coacervation time should not be too long,otherwise the microcapsules are prone to deformation and leakage;control the appropriate curing conditions will help to form a closed spherical microcapsules.3.In order to improve the bioavailability of Dragon’ Blood,we use Firstborn Microcrystallization Method to prepare nanocapsules and control the size of the nanocapsules to the demands of injection.Using gelatin as capsule material,water insoluble dragon’s blood as the core material,we optimized the stable process of nanocapsule preparation.Scanning electron microscopy and transmission electron microscopy were used to characterize the nanocapsules.Results showed shape of nanocapsules are spherical or elliptical,and the diameter is 100 ± 20nm.To analysis the particle size change and summarize the mechanism of nanocapsules,every step of the reaction liquid was taken to characterize particle size by the nano-particle tracking analysis technology,the results showed that Firstborn Microcrystallization grows up gradually,the wall material basically remain unchanged before intervention;With phase separation,the particle size changes,and gradually tightening after cross-linking reaction,it became stable finally;And it appears two peaks which including single capsules and adherent capsules,which is the result of cross-linking reaction taking place in each single capsules and among capsules;the finnal diameter depends on the timing of intervention and crosslinking degree.This experiment provides a certain theoretical basis for the mechanism and preparing procure for the Firstborn microcrystallization method in preparing nanocapsules.