Biomedical Engineering Reference
In-Depth Information
FIGURE 4.7
Breast cancer cell line SK-BR3 (under white light, left) exposed to QD emitting at
620 nm that are covalently attached to antibodies against surface proteins, EpCAM, appeared red
with greenish nucleus that was stained with DAPI ( 4',6-diamidino-2-phenylindole) under UV light
(right).
Courtesy of Ocean NanoTech.
(For color version of this figure, the reader is referred to the
online version of this topic)
using semiconductor NMs shows great promise for application in clinical diagno-
sis, environmental monitoring, food analysis, and other biological applications.
Total internal reflection fluorescence microscopy (TIRFM) was combined
with fluorescent QD labeling into an ultrasensitive single-molecule detection
(SMD) method for quantification of DNA.
50
In this method, the capture DNA that
was immobilized on silanized coverslip was used to detect the tDNA after the QD-
labeled DNA probe was hybridized to the tDNA. The images of the QD-labeled
hybridized DNA were recorded with a highly sensitive CCD. The captured tDNA
was quantified by counting the bright spots on the images and later compared
against a with a calibration curve that gave a limit of detection (LOD) of 10 pM.
Parameters that affected the signal included image acquisition, fluorescence probe,
substrate preparation, noise elimination from solutions and glass coverslips, and
nonspecific adsorption/binding of solution-phase detection probes. Lia's method
is also applicable for quantifying messenger RNA (mRNA) in cells.
The group of Wu et al.
101
developed an optical glucose nanobiosensor with
high sensitivity and selectivity at physiological pH.
101
To construct the glucose
nanobiosensor, fluorescent CdS QDs, serving as the optical code, were incor-
porated into the glucose-sensitive poly(
N
-isopropylacrylamide-acrylamide-2-
acrylamidomethyl-5-fluorophenylboronic acid) copolymer microgels, through
in situ growth method and “breathing in” method. The hybrid microgels with
quantum dots showed selectivity to glucose over the potential primary inter-
ferents, lactate, and human serum albumin in the physiologically important
glucose concentration range. The nanobiosensors adapted to glucose concen-
trations and regulated the fluorescence of the embedded QDs which converted
the biochemical signals into optical signals. The gradual swelling of the gel led
to quenching of the fluorescence from the QDs at elevated glucose concentra-
tions. The nanobiosensors are well tunable to the hybrid microgels through a
change in the cross-linking degree of the microgels. This system is exceptional
because of the easy functionalization and the potential for the combination
