Biomedical Engineering Reference
In-Depth Information
Figure 9.6
Schematic diagram representing
the concept of high-fi eld magnetic separation
and sorting of analytes. The sample
containing the target analyte (left) is exposed
to the specifi cally functionalized magnetic
nanoparticle containing an affi nity ligand such
as a protein, small molecule, or nucleic acid
(middle). Then, after a period of incubation,
an external magnetic fi eld is applied to
separate the nanoparticle/analyte complexes
from the sample (right). This effectively
enables the selective removal of a target
analyte from the sample background, allowing
for sensitive detection.
surface-bound sensor systems by attaching to an analyte; this makes the resultant
analyte-nanoparticle complex responsive to an applied magnetic fi eld. By using
functionalized magnetic nanoparticles and a relatively high-strength magnetic
fi eld, it is possible to rapidly pull the bound analytes from solution, independent
of any of the other background constituents that might potentially interfere with
their processing (e.g., induction and growth of cells) or detection, using a range
of techniques.
Studies based on the high-gradient preconcentration and separation methods
discussed above have been conducted to target a wide range of analytes that have
relevance in both environmental and clinical settings. These include: the separa-
tion and sorting of bacteria [102, 105, 107], viruses [104, 108], single cells [96, 97,
99-101, 103, 106], proteins [106, 109, 110], and nucleic acids [111-113]. In most
of these cases, the target analytes are bound to the nanoparticles solely for removal
from solution, and in order to separate them from background interferents (e.g.,
proteins, cells, and nucleic acids) common in biological samples. In addition to
these examples, a number of studies have shown that magnetic nanoparticles also
have potential as analyte preconcentrators for environmental remediation and
trace detection sensor systems [20].
In their ongoing studies, the present authors have shown that functionalized
superparamagnetic nanoparticles can be effectively dispersed in aqueous environ-
mental samples and sequester a wide variety of analytes, including heavy metals
