In vivo anti-tumor effect of dual release of cisplatin and adriamycin from biodegradable gelatin hydrogel

The objective of this paper is to investigate the in vivo anti-tumor effect by dual release of cisplatin (CDDP) and adriamycin (ADM) from a biodegradable hydrogel. Hydrogels with different water contents were prepared through the chemical crosslinking of gelatin by various concentrations of glutaraldehyde. Aqueous solution of CDDP, ADM or their mixture (CDDP+ADM) was impregnated into the freeze-dried hydrogel, followed by air-drying to obtain the dried hydrogel incorporating the corresponding drug. Irrespective of the hydrogel water content, 8-20% of CDDP incorporated and 60-80% of ADM was released from the hydrogel in the phosphate-buffered saline solution (PBS) at 37 °C within the initial 6 h and thereafter little release was observed. When intratumorally applied into mice carrying a mass of Meth-AR-1 tumor cells, the hydrogel incorporating CDDP+ADM showed significant higher anti-tumor effect on the tumor growth suppression and on survival period than other drug applications. Combination effect assay revealed that the hydrogel incorporating CDDP+ADM showed a synergistic effect between the CDDP and ADM, while the solution form showed antagonistic. The concentration of CDDP and ADM in the tumor tissue maintained at higher levels over 14 days after application. The time course of in vivo CDDP retention was in a good accordance with that of hydrogel remaining, whereas ADM was released faster, followed by the sustained release for 14 days. No practically problematic change in the mouse body and blood biochemical parameters was observed by application of the hydrogel incorporating CDDP+ADM. We conclude that dual sustained release of CDDP and ADM attached to the tumor synergistically enhanced their in vivo anti-tumor effect through the trans-tissue delivery.