Computational study of the effect of size and surface functionalization on Au nanoparticles on their stability to study biological descriptors.

The effects of varying nanoparticle size; polyethylene glycol (PEG) molecule length, type, and density; and functional groups for drug delivery systems are investigated computationally. A molecular dynamics (MD) study in the framework of a Monte Carlo simulated annealing scheme is done on gold nanoparticles (Au NPs) for sizes of 2.6 nm, 3.4 nm and 6.8 nm. The bonding of PEG molecules is investigated, and the binding energy (BE) is analysed as a reference to chemisorption and physisorption of the molecules. To investigate the frontier molecular orbitals and molecular electrostatic potentials, density functional theory (DFT) simulations are also performed for various PEG lengths and functional groups (FGs). The study reports on three conclusions: firstly, reducing the Au NP size leads to coordination number (CN) loss as the number of lowly coordinated atoms increases with decreasing particle size. Secondly, the stability of the Au-PEG system is independent of length beyond [Formula: see text]. And due to PEG high steric repulsion, the number of these molecules that can be physically adsorbed to the surface is limited. And thirdly, the FGs can be grouped into electron-withdrawing group (-NTA, Biotin, COOH) and electron-donating group (-NH