Fabrication Of OSA Starch Grafted With Folic Acid And Loading Study Of Doxorubicin Hydrochloride

Starch has the advantages of inexpensive,biocompatible and non-toxic.It is often used as the carriers for functional factors or drugs.The poor resistance of natural starch to enzymatic digestion and its difficulty in passing through the human upper digestive tract limit its application in oral delivery carriers.It is necessary to modify the natural starch to improve its digestive resistance.Octenyl succinic anhydrate(OSA)starch is a chemically modified starch with amphiphilic properties which effectively loads hydrophobic or hydrophilic drugs.OSA starch is resistant to enzymatic and acid digestion in the upper gastrointestinal tract and widely used in the design of oral delivery carriers.Based on the specific binding of folic acid(FA)to overexpressed FA receptors on the surface of cancer cells,modification of FA can further confer targeting properties to starch-based carriers.In this paper,OSA starch grafted with FA was successfully prepared.Doxorubicin hydrochloride(DOX)was used as the model drug,the loading potential of OSA starch grafted with FA for DOX and loading mechanism were investigated.The in vitro drug release performance of the drug-loaded complexes and the inhibition effect on colon cancer cells(Caco-2 cells)were further studied.The main studies were as follows:First,OSA starch with different FA grafting time were prepared.The structure and properties of OSA starch grafted with FA were investigated.The results of FTIR and X-ray photoelectron spectroscopy showed that FA was successfully introduced onto OSA starch granules.With the extension of FA grafting time from 0 h to 2 h,4 h and 6 h,the FA grafting rate of OSA starch increased from 0 to 0.020,0.034 and 0.037.The absolute value of zeta potential of OSA starch increased from 26.71 m V to 33.61 m V,38.7 m V and 39.3 m V.The result of XRD showed that the crystallinity of OSA starch gradually decreased and the crystalline form gradually changed from type A to a hybrid of type A and type V.The result of in vitro digestion showed that the grafting of FA effectively improved the anti-digestibility of OSA starch.The content of resistant starch(RS)increased from 79.4%to 94.5%,97.0%and98.0%.Next,the loading content of OSA starch with different FA grafting time for DOX was investigated and the loading mechanism was further studied.The results of loading capacity showed that FA-OSA-4h starch had the highest loading content of 79.7μg/mg for DOX.The result of fluorescence spectroscopy showed that the maximum fluorescence emission wavelength of DOX shifted from 555 nm to 588 nm after the formation of the complex,which indicated the existence of hydrophobic interaction between the carriers and DOX due to the CH-πandπ-πstacking effects.The zeta-potential showed that the absolute value of zeta potential of carriers decreased after the formation of the complexes,indicating the existence of electrostatic interaction between the carriers and DOX.In conclusion,the loading of OSA starch grafted with FA for DOX mainly relied on the electrostatic interaction and hydrophobic interaction.Finally,in vitro simulated digestion experiments and cellular experiments were designed to investigate the release performance of the drug-loaded complexes and inhibitory effect on Caco-2 cells.The results of in vitro simulated digestion experiments showed that the drug-loaded complex could significantly delay the release of DOX in the upper gastrointestinal tract compared with free DOX.The cumulative release rate of drug-loaded complexes in the upper gastrointestinal tract was only 20.3%.The cellular experiments showed that the survival rate of Caco-2 cells was only 20.9%when the concentration of drug-loaded complex reached 10~4μg/m L,which indicated that the drug-loaded complexes could effectively inhibit the growth of Caco-2 cells.The expression level of FA receptor in Caco-2 cells increased from 23.08 pg/m L to 41.74 pg/m L after treated with FA-modified drug-loaded complexes for 24 h.The red fluorescence of DOX appeared inside Caco-2 cells after treatment by the drug-loaded complexes and the cellular uptake of DOX showed a time-dependent.The drug-loaded complexes exerted the inhibitory effect by specific adhesion on the surface of Caco-2 cells.DOX was gradually released from the drug-loaded complexes and absorbed by Caco-2 cells,which affected the proliferation of Caco-2 cells.