Low affinity binding of plasma proteins to lipid-coated quantum dots as observed by in situ fluorescence correlation spectroscopy

Abstract

Protein binding to lipid-coated nanoparticles has been pursued quantitatively by using fluorescence correlation spectroscopy. The binding of three important plasma proteins to lipid-enwrapped quantum dots (QDs) shows very low affinity, with an apparent dissociation coefficient in the range of several hundred micromolar. Thus, the tendency to adsorb is orders of magnitude weaker than for QDs coated with dihydrolipoic acid.

The Nature of a Hard Protein Corona Forming on Quantum Dots Exposed to Human Blood Serum

“…DHLA and DPA ligands were covalently bound to the QD surfaces via ligand exchange; the PEG polymer was adsorbed onto the QD surfaces via hydrophobic interactions. Hydrodynamic radii, determined by FCS and dynamic light scattering (DLS) in phosphate buffered saline (PBS), pH 7.4 (Table ), were significantly greater than the size of the CdSe/ZnS core, R c , measured by transmission electron microscopy (TEM), with PEG‐QDs exhibiting the largest increase due to the bulky PEG chains. All QDs were negatively charged at physiological pH; their ζ‐potentials followed the sequence DHLA‐QDs < DPA‐QDs < PEG‐QDs, as expected from the charge on their functional groups.…”

“…HSA is the most abundant protein in serum and has been widely adopted as a model protein for studying NP‐protein interactions . Therefore, we also measured the adsorption of HSA onto the three QD types for comparison.…”

“…The hydrodynamic radius, R H , of QDs in the absence and presence of proteins can be calculated according to the Stokes–Einstein equationwith Boltzmann constant k B , temperature T , and solvent viscosity η. At high protein concentration, the viscosity increases and needs to be corrected, as previously reported for HSA . For serum, the viscosity was linearly interpolated between the viscosities of water, η 0 , and the serum stock solution, η s …”

“…It allows precise measurement of NP diffusivity, and minute changes of the hydrodynamic radius upon protein adsorption can be determined with subnanometer precision. By studying NP‐protein interactions for a variety of NPs with systematically varied surface properties and a range of important serum proteins, we have previously obtained a clear picture of the structure of the protein corona and the stabilizing interactions …”

Dissociation coefficients of protein adsorption to nanoparticles as quantitative metrics for description of the protein corona: A comparison of experimental techniques and methodological relevance

“…The resulting data set d h (c(P)) of hydrodynamic diameters determined at different protein concentrations c(P) can be fitted with the Hill model, yielding the protein concentration in which half of the NP surface is saturated with protein K' D , the maximum number N max of proteins which can be bound per NP, and the Hill coefficient n [11]. The group of Nienhaus et al has used such FCS measurements to determine protein adsorption of several proteins to different NP surfaces [21,24,26,[40][41][42][43][44][45]. Notably FCS measurements can be performed in situ, i.e.…”