Quantum Dot-Fluorescence-Based Biosensing - Quantum Dots for DNA Biosensing - page 33

[ 20 ]. The size-tunable photoluminescence and the broad absorption spectra of
QDs enable their great promise in multiplex DNA biosensing. In 2010, they suc-
cessfully applied this similar proposal for multiplex DNA detection [ 21 ].
Recently, they further improved their design and described a liposome/QD-
based single-particle detection technique for multiple DNA targets with attomolar
sensitivity even without the involvement of any amplification step. As shown in
Fig. 3.8 , the carboxyl-functionalized liposome/QD (L/QD) complex and carboxyl-
modified magnetic beads were covalently conjugated with the amino-terminated
oligonucleotides, producing the reporter probe and the capture probe, respectively.
The presence of target DNA leads to the generation of a sandwich hybrid contain-
ing L/QD complexes and results in the release of QDs, which can be sensitively
counted by single-particle detection. They designed two sets of probes for the
simultaneously determination of HIV-1 and HIV-2 [ 22 ].
QD barcodes are another popular approach for multiplexed DNA sensing. Chan
et al. used the continuous flow focusing technique to create over 100 different
Fig. 3.8 Design principle of liposome/QD complex-based single-particle detection technique.
a L/QD complexes, L/QD complex-tagged reporter probes and magnetic bead-modified capture
probes were prepared first. b Formation of sandwich hybrids in the presence of target DNA and
further purification by magnet. c Release of QDs from L/QD complex and subsequent measure-
ment by single-particle detection. Reproduced with permission from Ref. [ 22 ]. Copyright 2013,
American Chemical Society