Smart Peptide/Au Nano-carriers for Drug Delivery Systems: Synthesis and Characterization, Interactions with Calf Thymus DNA, and In Vitro Cytotoxicity Studies.

Peptides are reducing and capping agents that can be used for the synthesis of biocompatible metal nanoparticles under relatively mild conditions. However, the abundance of random and inactive amino acid sequences in peptides, the lack of peptide design rules have led to their studies being slow and make it difficult to use them. In this study, calcitonin-capped Au nanoparticles were synthesized by a simple and controlled method. The aim of this study was to determine the cytotoxicity of calcitonin-capped Au nanoparticles on the human breast cancer cells (MCF-7) and osteoblast cell lines (G292). The absorbance of calcitonin-capped Au nanoparticles is higher than bare AuNPs. FTIR analysis revealed that amino acides of present in calcitonin played dual roles as reducing and stabilizing agents during synthesis of AuNPs. TEM image analysis showed formation of predominantly spherical calcitonin-capped Au nanoparticles with mean particle diameter of about 2–20 nm. The interactions between the calcitonin-capped Au nanoparticles and calf thymus DNA in aqueous was studied by circular dichroism (CD), UV–Vis and fluorescence spectroscopy. The results indicated that the synthesized calcitonin-capped Au nanoparticles can successfully insert into calf thymus DNA. [L]_1/2, concentrations of calcitonin-capped Au nanoparticles in the midpoint of transition, 0.32085 mM and o.28744 mM and the apparent binding constant (K × 10⁴(M)⁻¹), 79.52 and 81.04 were obtained at 300 and 310 K, respectively. The cytotoxicity of the prepared calcitonin-capped Au nanoparticles was measured on the human breast cancer cells (MCF-7) and osteoblast cell lines (G292) by cell viability (MTT assay) and apoptosis (TUNEL assay: Terminal deoxynucleotidyl transferase dUTP nick end labeling). According to the MTT assay, the CC₅₀ values of calcitonin-capped Au nanoparticles and cisplatin are 12.7 μM and 8.3 μM, respectively in G292 which are very near to each other compared on MCF-7. Therefore, TUNEL assay was done on G292 cell lines. The results showed that apoptosis was obviously observable by 48% DNA fragmentation on G292 cell lines. Therefore, the calcitonin-capped Au nanoparticles are suitable drugs which have strong potential in DNA denaturation and apoptosis especially on osteoblast cell lines (G292). [ABSTRACT FROM AUTHOR]