Selection of Optimal Chromatography Medium for Purification of Quantum Dots and Their Bioconjugates ACS Paragon Plus Environment Chemistry of Materials Selection of Optimal Chromatography Medium for Purification of Quantum Dots and Their Bioconjugates

Photoluminescent quantum dots (QDs) due to their unique optical properties and capacity for conjugation with biomolecules are widely used in biomedicine. However, numerous by-products of bioconjugation can seriously influence the interaction of these nanoprobes and their targets. The use of size exclusion chromatography (SEC) for the separation of QDs and by-products of bioconjugation is rather challenging because of the difference in chemical and physical nature of nanoparticles and biomolecules, which makes the choice of stationary phases for SEC a complicated task. Here we have investigated the efficiency of SEC purification of water-soluble CdSe/ZnS QDs and QD-based conjugates from polyethylene glycol derivatives serving as stabilizing ligands, as well as bis-netropsin and 4,5,9-trisubstituted acridine derivative serving as DNA ligands using Sephadex resins with different porosities. We have found that multiple SEC cycles using popular pre-packed Sephadex G25 columns does not provide efficient purification of QDs, whereas Sephadex G100 and G200 are much more efficient after a single SEC run because of the optimal peak resolution and allow preserving the colloidal stability of QDs. Our results show that the use of less common chromatographic media in the group of Sephadex resins allows efficient purification of QD bioconjugates from contaminants for their subsequent use in bioimaging or diagnostics.