Electrostatically Self-assembled Quinazoline-based Anticancer Drugs on Negatively-charged Nanodiamonds for Overcoming the Chemoresistances in Lung Cancer Cells

The nanodiamond (ND) conjugates of gefitinib (GF) and erlotinib (EL) were assembled for in vitro lung cancer treatments. The carboxylate infrared bands along with the negative surface charge of -28.3 (+/- 2.1) mV were found efficient to conjugate the nitrogen-containing quinazoline ring drugs, due to the electrostatic interactions, resulting from the surface changes to -12.0 (+/- 1.2) mV and -9.1 (+/- 1.2) mV after adsorption of GF and EL on NDs, respectively. The physicochemical properties of NDs were characterized by transmission electron microcopy, X-ray diffraction, X-ray photoelectron, infrared and Raman spectroscopic tools. The size distributions of NDs after the self-assembly of GF and EL could be checked by dynamic light scattering measurements. The uptake of NDs in cancer cells was estimated by fluorescence microscopy. Cell viability appeared to decrease by 30-50% at 50 and 100 nM of GF and EL, respectively, after the treatment of PEG-assembled NDs compared to the cases using free drugs. Our ND conjugates may be potentially useful for overcoming the chemoresistances in lung cancer cells.