Systematic investigation of cellular response to nanoparticle surface chemistry

The interface between nanoparticles (NPs) and living systems is one of the most important determinants of cellular responses. The well-understanding of the interaction between the NP surface chemistry and living systems makes possible to design safer NPs to be used in medical and technological areas. In this study, it was aimed to systematically investigate the cellular response of living cells to subtle surface chemistry changes on AuNPs conjugated with specially designed carbohydrates and peptides. In order to create small differences on AuNP surfaces, spherical AuNPs of 13 nm diameter size were modified with four carbohydrates, D-Glucose, D-Mannose, Lactose and Mannose, and fourteen peptides different in charge, length, isoelectric point, sequence with or without RGD and free end terminus -NH2 or -COOH. The cellular responses of A549, BEAS-2b and MDA-MB-231 cells were investigated by considering cellular uptake, cytotoxicity and cell cycle arrest. Before modification of AuNP surfaces, carbohydrates were thiolated using Lawesson reagent. Then, AuNPs with an average size of 13 nm were conjugated with carbohydrates and peptides in appropriate conditions. The naked AuNPs and AuNP conjugates were characterized with UV/Vis spectroscopy, DLS, agarose gel electrophoresis, FTIR and SERS to understand the nature of the interactions of the used biomacromolecules on the AuNPs surfaces. The peptides designed by placing cysteine to -NH2 or -COOH end showed significantly different binding affinity to AuNPs surfaces. Then, the cellular response of the conjugates were investigated using several molecular techniques including WST-1 cell proliferation assay, Apoptosis/Necrosis assay, Clonogenic assay and cell cycle evaluation assay. It was found that small changes on the surfaces of AuNPs caused varying significant cellular responses depending on surface chemistry, NP concentration and cell line type.