Esterification Of Starch Nanocrystals And The Research Of Its Application

China is a big country of rice production, the annual output of rice is about200million tons. With the increasing of people’s living standard, people demand more and more for excellent quality. Due to poor taste, indica rice have been accumulated and lead to a waste of resources. In the bio-pharmaceutical industry, most researchers choose polymer nanomaterials as drug delivery, drug carriers avoid vivo enzymatic degradation by physical adsorption, chemical bonding or embedding, to extend the release time of the drug in the body and to improve drug effects. Starch is a natural polysaccharide polymer materials, which is renewable, abundant and low price, in particular, it has good biocompatibility and biodegradability. Modifying starch to form a kind of potential drug carrier, in this way it not only solves the problem of the accumulation of indica rice, but also provides a promising drug carrier for the bio-pharmaceutical.In this paper, adopts the sulphuric acid hydrolysis to prepare starch nanocrystals, then acetylated starch nanocrystals are prepared by adopting esterification techniques based on native rice starch nanocrytals as raw material under different acetic anhydride, starch nanocrystals before and after modification are characterized by infrared spectrum, X-ray diffraction, dispersion test; Esterification modified starch nanocrystals serve as drug carrier to prepare adriamycin(DOX)drug-loading particles. Testing the adsorption ability and the release of performance measurement of drug-loading particles to examines the feasibility of esterification modified starch nanocrystals used as drug carrier.Specifically,research contents and conclusions are as follows:1. Using3.16mol/L sulfuric acid to treat starch, with different handling time preparing the starch granules of different sizes. The results show that with extension of handling time, starch particle size gradually decreases. When starch are treated six days, starch granules of an average particle diameter of225nm are obtained, which may be called nanoscale starch particles; evenmore, the yield of starch after six days acid hydrolysis up to27.1%; with the starch particle size reducing, the specific furface area increases froml.10m2/g to8.78m2/g remarkably; with acid hydrolysis time prolonging, the solubility is increased from8.3%to82.8%, and the swelling power is decreased from11.6g/g to0.85g/g significantly, hydrolyzed starch granules are susceptible to enzymatic attack. Meanwhile, the rice starch granules after acid hydrolysis for2d substantially have no gelatinization viscosity.2. Under the action of sulfuric acid, amorphous region of indica rice starch is first eroded rapidly, followed by destruction of the crystalline regions of starch, at the initial stages the acid hydrolysis occurs in the surface of the starch particles, amylose and amylopectin on starch particle surface are simultaneously acidolysis. Acid hydrolysis under the gelatinization temperature,crystal structure of the starch granules does not change. Starch nanoparticles is still typical A-type. Amorphous and crystalline zone area is hydrolyzed so that the degree of crystallinity increased. The crystallinity native rice starch was25.78%, crystallinity of the starch granules with acid hydrolysis six days was58.82%, which improve by56%compared with the original rice starch;3. Below the gelatinization temperature of the starch nanocrystals, acetic anhydride is added with an amount of4%,8%,12%of the starch dry basis to prepare the esterified low-substituted (0.05,0.09,0.15) starch nanocrystals. Acetyl groups are introduced into starch nanocrystals, with amount of acetic anhydride increasing, hydroxyl on starch nanocrystal surface is substituted, the more hydrophilic acetyl groups are introduced, the stronger steric hindrance form, resulting in increase of solubility and swelling power of modified starch nanocrystals, the solubility is increased from78.1%to83.4%, and the swelling power is decreased from0.89g/g to1.58g/g and the rate of hydrolysis of starch decreases from46.44%to31.85%, which exhibit resistance to enzyme hydrolysis. X-ray diffraction showed that the part of crystal structure of esterification modified starch nanocrystals retain with new crystalline structure forming; infrared spectra of starch nanocrystals further prove that the esterification reaction of acetic anhydride take place. With the increase of the amount of esterifying agent, the more hydroxyl groups of starch nanocrystal surface are substituted, the stronger intermolecular forces;4. After the esterification modification, the polarity of starch nanocrystals is reducing, which can be uniformly dispersed in water and carbon tetrachloride; higher degree of acetyl substitution, the easier starch nanocrystals dispersed in an organic solvent. Particularly, the reunion phenomenon of starch nanocrystals is suppressed;5. Experiment condition:the medicine ball ratio is1:20, the adsorption time is1h, adsorption temperature is37℃, to prepare modified starch nanocrystals drug carriers. Doxorubicin drug loading of esterification modified starch nanocrystals up to6.03%, much higher than the original starch drug loading of3.08%. The study of vitro drug release properties of starch granules shows that the esterified modified starch nanocrystals of degree of substitution of0.15has released only39%after10h, and its drug release time to reach equilibrium is much larger than the original blank drugs and drug-loaded starch nanocrystal, which indicates that with the degree of substitution improving. Esterified modified starch nanocrystals can well control drug release. The results show that the acetylated modified starch nanoparticles is a potential anticancer drug carrier.