Recent progress in the bioconjugation of quantum dots

Bioconjugation of quantum dots: Review & impact on future application

“…gel electrophoresis). When the average conjugate valence exceeds 4 biomolecules per QD the effect of the Poisson distribution is minimized and can be neglected [42,43].…”

“…SA is not a glycoprotein and the lack of high carbohydrate content, combined with a much lower pI of 5-6, which makes SA neutral at physiological pH also results in a lower non-specific binding. There are now a number of genetically engineered avidin and SA derivatives commercially available [29,43]. Biotin is a relatively simple water-soluble organic compound, also known as vitamin B7 or vitamin H. There are a variety of biotin derivatives that make biotinylation of QDs and biological molecules rather straightforward.…”

“…In the case of Ig (or antigen) this can result in non-epitaxial conjugation which will lead to a decrease of sensitivity and specificity of the bio-detection [29]. Biotinylation of biomolecules usually involves chemical preparation with an amine-, thiol-or carboxyl-reactive biotin reagent or, alternatively, the molecule can be recombinantly modified to display biotin acceptor peptide sequences [43]. An important issue to consider when conjugating biotin to groups such as the amines distributed around a protein, is that control over the labeling site and ratio is hard, given the abundance of targets.…”

“…Since each (strept)avidin protein is an obligate tetramer it can bind up to four biotin moieties, so care must be taken not to over biotinylate the biomolecule of interest, since this can induce crosslinking of the QDs and formation of undesired conjugates [43]. Overall, the detailed fundamental understanding of the (strept)avidinbiotin interaction, its wide utility, and the extensive library and ongoing evolution of reagents are responsible for the continued use of (strept)avidin-biotin chemistry for QD bioconjugation in the foreseeable future [29].…”

“…Bioconjugation of QDs via biotin-avidin chemistry is ubiquitous but is less popular as EDC-based covalent conjugation chemistry because it often produces large size bioconjugates, which can limit their utility in targeted applications such as fluorescence resonance energy transfer (FRET) and cellular research. Other approaches can utilize Ig affinity for a ligand attached to the QD or vice versa, along with other enzyme-substrate or receptor-ligand interactions [29,43,52].…”