Surface coatings for minimizing nonspecific binding of quantum dots and other nanoparticles.
Coating method generated a 140-fold reduction in nonspecific binding relative to that of carboxylated quantum dots and 10-20-fold reduction relative to that of PEG- and protein-coated quantum dots.
Quantum-dot (QD) nanocrystals are promising fluorescent probes for multiplexed staining assays in biological applications. However, nonspecific QD binding to cellular membranes and proteins remains a limiting factor in detection sensitivity and specificity. Drs. Shuming Nie and Brad Kairdolf have developed a new class of hydroxyl (-OH)-coated QDs for minimizing nonspecific cellular binding and for overcoming the bulky size problems encountered with previous surface coatings. The hydroxylated QDs are prepared from carboxylated (-COOH) dots via a hydroxylation and cross-linking process. With a compact hydrodynamic size of 13-14 nm (diameter), the quantum dots are highly fluorescent (>60% quantum yields) and stable under both basic and acidic conditions. By using human cancer cells, the researchers compared the nonspecific binding properties against that of the industry standards: carboxylated, protein-coated, and poly(ethylene glycol) (PEG)-coated QDs. Quantitative cellular staining data indicate that the hydroxylated QDs result in a dramatic 140-fold reduction in nonspecific binding relative to that of carboxylated dots and a significant 10-20-fold reduction relative to that of PEG- and protein-coated dots.
With minimized nonspecific binding and background interference, QD probes are especially well-suited for analyzing cancer biomarkers that are present at low concentrations or in small numbers of cells. The cancer biomarker market comprises 55% of the entire biomarker market with revenues in excess of $3 billion annually.
Publication: Anal Chem. 2008 Apr 15;80(8):3029-34.