Purified silk fibroin‐<scp>L</scp>‐asparaginase bioconjugates show increased thermostability and resistance to trypsin digestion

Abstract

Abstract Bioconjugation protocols have been recently used to improve the therapeutic properties of the anti‐leukemic enzyme L ‐asparaginase. In this study, we study the variation of reaction factors, such as mass ratio, pH value, reaction temperature and time, and the concentration of cross‐linker, in the modification reaction of L ‐asparaginase with silk fibroins. The optimum reaction parameters were obtained as follows: pH 7.0, mass ratio of silk fibroin to L ‐asparaginase 5:1, reaction time 8 h, and temperature 4°C. The rate of ε‐amino group modification was 57.88% and the recovery of modified L ‐asparaginase was 66.58% under these reaction conditions. We isolated and purified the silk‐ L ‐asparaginase conjugates with two consecutive chromatography steps: anion‐exchange (XK 16×20, Q Sepharose FF) and gel filtration (Tricorn 10×600, Sephcryl S‐300 HR) chromatography. Finally, the stabilities of the enzymes were investigated. The results showed that modified L ‐asparaginase had a higher thermostability and higher resistance to trypsin digestion.