Abstract:

Objective To prepare the oxaliplatin （OXA）-loaded elastin-like polypeptides （ELPs） hydrogels， and to investigate its in vitro drug release and the killing effect in the CT26 colon cancer cells. Methods The prokaryotic proteins ELPs were produced in Escherichia coli （E.coli） system and purified via the inverse transition cycling （ITC）.The ELPs hydrogel was prepared by mixing the ELPs protein solution with the cross-linking agent tetrakis hydroxymethyl phosphonium chloride（THPC）.The microstructures of hydrogels were observed by scanning electron microscope （SEM）； CCK-8 assay was used to determine the survival rates of the CT26 cells and NIH3T3 cells after hydrogel treatment and Live/Dead cell staining was used to observe the survival of the CT26 cells after treated with 30 and 40 g?L^－1 hyrogels for 48 h. The OXA-loaded ELPs hydrogels were prepared， and the drug release of OXA-loaded hydrogels was detected at different pH values （pH 6.5 and pH 7.4） in the sustained release liquid. The survival rates of CT26 cells after added with the ELPs hydrogels soak solution loading different concentrations （0.25， 1.00， 4.00， 16.00， and 64.00 mg?L^－1） of OXA were detected and the survival rates of CT26 cells after treated for different time in various groups were detected by CCK-8 assay. Results The gel electrophoresis analysis showed that an obvious bold protein band was observed in the region with expected molecular weight 38 000. After protein purification using ITC， almost no other protein was found. The ELPs protein solution was transited from transparent solution into an opaque white hydrogel after the addition of THPC. The hydrogel showed uniformed pores and three-dimensional structure under SEM.The CCK-8 assay results indicated that the survival rates of CT26 cells and NIH3T3 cells were close to 100%. The Live/Dead cell staining results showed the green fluorescence in the CT26 cells under fluorescence microscope. The OXA-loaded hydrogels showed sustained drug release profile in vitro，and a slightly faster drug release in pH 6.5 was found than that in pH 7.4.The CCK-8 assay results showed that the OXA-loaded hydrogels could significantly inhibit the proliferation of CT26 cells in a dose-dependent manner. With the prolongation of the incubation time， the survival rates of CT26 cells treated with drug-loaded hydrogel were decreased gradually. Conclusion The OXA-loaded ELPs hydrogels have sustained release profile in vitro and can kill efficiently and consistenly the colon cancer CT26 cells of the mice. ELPs hydrogels may be used as the safe and effective drug delivery system for cancer therapy.

Key words: Elastin-like polypeptides, Hydrogels, Oxaliplatin, Colon neoplasms, Drug delivery