Quantitative Differentiation of Cell Surface-Bound and Internalized Cationic Gold Nanoparticles Using Mass Spectrometry

Differentiation between cell surface-bound and internalized nanoparticles is challenging yet essential for accurately quantifying cellular uptake. Here, we describe a versatile mass spectrometry-based method that allows separate quantification of both cell surface-bound and internalized nanoparticles. This rapid method uses tuned laser fluencies to selectively desorb and ionize cell surface-bound cationic gold nanoparticles from intact cells, providing quantification of external particles. Overall nanoparticle quantities are obtained from the cell lysates, with subtraction of external particles from the total amount providing quantification of taken-up nanoparticles. The utility of this strategy was demonstrated through simultaneous quantitative determination of how cell-surface proteoglycans influence nanoparticle binding and uptake into cells.