Comparison of direct and indirect conjugation methods to produce a targeting nanodrug with more biocompatibility, high cellular uptake and binding for photothermal therapy of breast cancer

These nanomaterials are currently under investigation and developing for applications related to cancer therapy. To improve efficiency for targeted treatment of malignant tumors, we compare the two conjugation methods (direct and indirect) for production of bombesin-gold nanorods conjugate against gasterin release peptide receptor as a targeted photothermal therapy agent for breast tumor. Bombesin conjugated with gold nanorods using the direct and indirect methods was used. The attachment of bombesin to gold nanorods and in vitro stability of two conjugates in mouse blood was studied by UV/vis spectroscopy. Cell toxicity for both of conjugate was investigated by MTT test. Selective binding and cellular uptake studies were performed with the T47D cell line. Results obtained of two conjugates compared to introduce best conjugation method. UV-vis spectroscopy confirmed the conjugation of bombesin with gold nanorods in two methods. The stability assessment proved same and high stability of two conjugates in mouse blood up to 4 h. Cytotoxicity study showed higher biocompatibility of indirect conjugate of bombesin and gold nanorods in comparison with its direct conjugate. In vitro studies showed that indirect conjugate of bombesin and gold nanorods have four-fold binding and cellular uptake in comparison with its direct conjugate. These results show that the indirect conjugation was better than the direct conjugation to produce targeted nanodrug with low cytotoxicity, high binding and cellular uptake for photothermal therapy of breast cancer.