NP-Ab conjugate characterization. (a) TEM image of the NPs synthesized, scale bar = 20 nm. (b) Optical absorption spectra of the NPs (black), NP-Ab conjugates (red). (c) DLS spectra of the NPs (black), NP-Ab conjugates (red). (d) Zeta potential measurements of bare NPs, NP-Abs. (e) Gel electrophoresis of Lane 1, NPs as synthesized; Lane 2, NPs-Abs; and Lane 3, NP-Abs with PEG-thiol backfill.