Gold nanoparticles functionalization study by density functional theory

Abstract

Besides various applications of metallic nanoparticles, DNA sensors are devices that combine the selectivity of DNA with the nanoparticles' sensitivity. This technology development is required whereas similar symptoms are caused by different organisms contaminations. This is the case of the fungus Paracoccidoides brasiliensis that can be breath in and installed in the lungs. The symptoms manifested by these contamination are initially similar to tuberculosis, therefore, are usually wrongly diagnosed. In these cases, the treatment and prescription are not adequate resulting in a disease progression and high procedure expenditure. The use of DNA functionalized nanoparticles sensors are based on colorimetric technique that is quick, accurate and easy to be manipulated. The test result is also very simple to be interpreted: red means positive and blue means negative to the disease investigation. Although this diagnosis technique has already succeeded in our laboratory (with FAPESP project 2009/09559-5), we verified the necessity of standardizing concentration of colloids constituents. In order to reduce the number tests of laboratory associating the quickness and the confiability that are characteristics of Density Functional Theory (DFT), we developed another project with the goal of optimizing nanosensors (FAPESP 2011/13250-0). In this context, this project has the aim to study the single strands of DNA concentrations adsorbed on the nanoparticles surfaces (grafting) and its dependence with the pH and saline environment by DFT. In this project, we study the electronic properties of DNA strands on the gold surface. The plane surfaces and curved modeling are compared to evaluated the influence of the coordination atoms number in the nanoparticle modeling. In this study, we'll be able to estimate the density of DNA strands on the nanoparticle, considering the influence of the environment. Then, we can suggest a optimum molarity of colloid constituents. (AU)