Biomedical Engineering Reference
In-Depth Information
by using other functionalized nanomaterials such as DNA-Au NPs.
Cetyltrimethylammonium bromide-capped Ag NPs as the RLS
probe has been shown to be useful in the detection of DNA and
RNA.
70
The interactions among Ag NPs, cetyltrimethylammonium
bromide, and DNA through electrostatic attraction and/or chemical
afinity occur, leading to aggregation of Ag NPs and thus, increases
in RLS signals. Under optimum conditions (1.0 μg/mL Ag NPs,
8.0 μM cetyltrimethylammonium bromide, 5.0 mM Tris-HCl at pH
7.6), there are linear relationships between the quenching extent of
RLS and the analytes over the concentrations ranges of 4.0 × 10
-9
to
2.0 × 10
-6
g/mL for ish sperm DNA, 7.0 × 10
-9
to 1.8 × 10
-6
g/mL for
calf thymus DNA, and 6.0 × 10
-9
to 1.0 × 10
-6
g/mL for yeast RNA.
This RLS method provides LODs of 2.7 × 10
-10
g/mL, 4.8 × 10
-10
g/
mL, and 7.2 × 10
-10
g/mL for ish sperm DNA, calf thymus DNA, and
yeast RNA, respectively.
8.4
Conclusions and Outlook
The RLS signal of a scattered particle depends on its absorption
feature, size, shape, concentration, and refractive index relative to
the surrounding medium. In addition, the intensity and frequency
of a light source are likewise important. Thus, control of these
parameters is important for developing sensitive RLS techniques.
Although Ag NPs are more eficient at light scattering than Au NPs, the
latter have been used in most of the RLS techniques, mainly because
of its stability and ease in preparation. It is thus possible to enhance
RLS sensitivity by using more stable Ag-based nanomaterials such
as Ag-Au NPs.
Having advantages of high sensitivity, rapidity, and simplicity,
RLS techniques have been applied to the determinations of the
concentrations of a number of analytes, including proteins, nucleic
acids, pharmaceutical drugs, and carbohydrates in artiicial and
real samples. Successful examples have demonstrated the great
potential of RLS techniques for diagnosis of disease, food quality
control, cell imaging, and so on. Although RLS techniques are not as
popular as colorimetric assays using Au NPs, they are more sensitive.
Theoretically, most developed colorimetric assays using Au and Ag
NPs can be readily applied to RLS techniques. Thus, it is expected
that RLS techniques will soon gain popularity as the techniques
become well recognized.
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