Determination of the intracellular stability of gold nanoparticle monolayers using mass spectrometry

Monolayer stability of core-shell nanoparticles is a key determinant of their utility in biological studies such as imaging and drug delivery. Intracellular thiols (e.g., cysteine, cysteamine, and glutathione) can trigger the release of thiolate-bound monolayers from nanoparticles, a favorable outcome for controllable drug release applications but an unfavorable outcome for imaging agents. Here, we describe a method to quantify the monolayer release of gold nanoparticles (AuNPs) in living cells using parallel measurements by laser desorption/ionization (LDI) and inductively coupled plasma (ICP) mass spectrometry. This combination of methods is tested using AuNPs with structural features known to influence monolayer stability and on cells types with varying concentrations of glutathione. On the basis of our results, we predict that this approach should help efforts to engineer nanoparticle surface monolayers with tunable stability, providing stable platforms for imaging agents and controlled release of therapeutic monolayer payloads.