Biomedical Engineering Reference
In-Depth Information
Consider the receptor−analyte pairs, DNP−anti-DNP, and
HSA−anti-HSA, that have K a and analyte size in a similar level,
the detection limits are similar although HSA has a much larger
molecular weight (MW) than DNP. For the receptor−analyte pairs,
biotin−anti-biotin and anti-HSA−HSA, that have K a in a similar level,
the DL by immobilized biotin to detect anti-biotin is better than
that by immobilized anti-HSA to detect HSA, suggesting that the
size of the analyte is an important factor for determining the DL.
Interestingly, with anti-HSA is immobilized as receptor to detect
HSA, the K a decreases by two orders of magnitude as compared to
that with HSA as immobilized receptor to detect anti-HSA. Such a
decrease in K a may be attributed to a loss of activity of the coupled
antibody, since antibody is an asymmetrical macromolecule which
often has a disorder orientation after immobilization on a surface.
The study illustrates how important an immobilization step can
affect the biosensor performance, whereas the binding afinity can
actually be revealed by a FO-PPR biosensor.
The FO-PPR sensors have been applied to detect staphylococcal
enterotoxin B (SEB), 24 organophosphorous pesticides, 65 lead
ion, 66 cadmium ion, 67 antinuclear antibodies (ANA), 25 orchid
Odontoglossum ringspot virus (ORSV) 60 , guanosine 3 ,5 -cyclic
monophosphate (cCMP), 68 and interleukin-1β (IL-1β). 69 In the
determination of staphylococcal enterotoxin B (SEB), 24 the DL of the
FO-PPR sensor is 0.04 ng/mL (1.4 × 10 −12 M), which is the lowest as
compared to enzyme-linked immunosorbent assay (ELISA) (3.9 ng/
mL) 70 and competing biosensor technologies such as SPR sensors
(0.5~10 ng/mL), 71,72 piezoelectric crystal biosensors (0.1 μ g/mL), 73
and iber optic luorescence biosensor (0.5 ng/mL). 74
In the determination of organophosphorous pesticides, 65 the
gold nanoparticle (GNP) surface was covalently coupled with
acetylcholinesterase (AChE) to detect paraoxon. The underlying
mechanism is that paraoxon prevents acetylchloline chloride (Ach)
reacting with AChE by destroying the OH bond of serine in AChE.
The deactivated AChE can be reactivated with dephosphorylation by
2-pyridine-aldoxime methoiodide. The DL of the sensor is 0.23 ppb,
which is slightly lower than the DL of 0.3 by an amperometric
biosensor. 75 The sensor gave reproducible results after storage in
dry state at 4 ° C for 60 days and remained 94% of its original activity
after six cycles of inhibition and reactivation.
 
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