Biomedical Engineering Reference
In-Depth Information
sensitive detection among relevant environmental and clinical samples. Whilst the
predominant use for these types of functionalized nanomaterials relates to biosen-
sors in the clinical setting, much attention has also been paid to the benefi ts of
using nanomaterial-enhanced biosensor-type systems (i.e., those which use bio-
molecules as affi nity reagents or recognition elements) for the detection of envi-
ronmentally relevant analytes such as bacteria, pesticides, and viruses [12]. These
types of material provide the means to separate analytes from a complex sample
and, in cases where a trace sensing of the contaminants is desired, they may also
serve as a preconcentration material for sensor enhancement.
A fundamental approach for improving any analytical method is to selectively
separate the analyte(s) from the sample matrix and to concentrate them into a
smaller volume prior to measurement. The preconcentration of analytes before
assay allows improvements to be made to the sensitivity, selectivity, and speed of
the analytical process. One approach to improving any analytical method is to
separate the analyte(s) from the sample matrix and to concentrate them into a
smaller volume prior to measurement. Figure 9.5 illustrates the general analytical
process of sample preconcentration (steps 1-3) and detection (step 4) using sorbent
materials in a generic sense.
Preconcentration
represents an ideal application for functionalized magnetic
nanoparticles. Once dispersed in solution, the nanoparticles can rapidly contact
high volumes of solution (Stage 1), selectively capture target analytes (Stage 2), and
then be magnetically recovered and manipulated by the application of a relatively
strong (often
1 T), but easy to generate, magnetic fi eld (Stage 3). The functional-
ized magnetic nanoparticles may also provide a magnetically controllable sorbent
material for solid-phase extraction (SPE). Previously, it has been shown that the
>
Figure 9.5
Schematic showing the general
analytical process used to preconcentrate and
detect low levels of analytes in environmental
samples. In steps 1-3, the sorbent material
(i.e., functionalized magnetic nanoparticles)
are used to fi rst bind a target analyte and
then, through the application of an external
magnetic fi eld, separate it from other
constituents of complex samples. In step 4
and beyond, the analyte is measured using
the desired analytical method, prior to
sending data output that signifi es the
presence of the intended target in the sample.
As can be seen from this schematic, magnetic
nanoparticles can play a variety of roles in
going from sample to answer using solid-
phase extraction and/or preconcentration.
