Surface Modification Of Gold Nanoparticles With Self-assembled Monolayer And Its Biological Effects

The emergence of nanotechnology is considered to be the biggest innovation withtechnology and engineering since the Industrial Revolution. The nanotechnology hasrapid development and broad application prospects in industrial production, medicalimaging, disease diagnostics, drug delivery, cancer treatment, gene therapy and otherareas. Due to the wide range of applications of nanotechnology, human has exposed to avariety of nanomaterials environment in an unprecedented way. Nanomaterials wasconfirmed that affected the health of the organism at the level of organs, tissues, cells,proteins more or less.In this study, we selected two thiols (SH-（CH₂）₁₁CH₃and SH-（CH₂）₁₁OH) withdifferent end groups. Then modified gold nanoparticles with self-assembled monolayer（SAM） mixed with the SH-（CH₂）₁₁CH₃and SH-（CH₂）₁₁OH in different ratios（100%:0%,75%:25%,50%:50%,25%:75%,0%:100%）. So the modified goldnanoparticles （AuNPs） have a series of gradient surfaces with hydrophilic andhydrophobic groups. After that, we study the biological effects of surface chemicalgroups and doses with AuNPs.After the full reaction of AuNPs and thiol solution, the results showed that the sizeof nanoparticles （NPs） increased significantly compared with the control by thenanoparticle size analysis. It indicated that some substances binded to the surface of theAuNPs so that the size of NPs increased. Further more, the infrared spectroscopyshowed that the combination of substances were the thiol molecules, and the ratios ofthiols SH-（CH₂）₁₁CH₃to SH-（CH₂）₁₁OH changed gradiently. So it was proved that thesurface modification of AuNPs with SAMs was successful. HUVECs were co-culturedwith unmodified and modified AuNPs. The results of NO test showed that all SAMsmodified AuNPs （SAM-AuNPs） were able to improve the content of NO，and then lesstoxic to endothelial cells. The results of MTT assay showed that it had the lowestcytotoxicity when the ratio of SH-（CH₂）₁₁CH₃to SH-（CH₂）₁₁OH is50%:50%. However,when the ratio of SH-（CH₂）₁₁CH₃to SH-（CH₂）₁₁OH is0%:100%or100%:0%, thecytotoxicity is higher. In addition, the cytotoxicity increased significantly when theconcentration of AuNPs exceeded50μg/mL. The results of T-AOC test showed that thetotal antioxidant capacity was strongest when the ratio of SH-（CH₂）₁₁CH₃toSH-（CH₂）₁₁OH is50%:50%. In the study of the cellular uptake of AuNPs, with the concentration of AuNPs increasing, the amount of AuNPs by the way of cellular uptakeincreased. And the amount of cellular uptake for hydrophilic group modified AuNPs ismore higher compared to hydrophobic group modified AuNPs. We also studied thedevelopmental toxicity of AuNPs in zebrafish. The experimental results showed that thehydrophilic AuNPs have a higher toxicity in zebrafish compared with other groups, cancause a higher mortality rate and lower hatching rate. But hydrophobicity NPs showed alower toxicity.The results of this study have important guiding significance for understanding therelationship between the suface chemical properties, dose of NPs and its biologicaleffects. It provides important theoretical data for the biological effects of nanomaterials,and also can promote better application of nanomaterials in the biomedical field.