Biomedical Engineering Reference
In-Depth Information
polyclonal antibodies then binds the captured virus. The sandwich complexes are meas-
ured using a multiparameter flow cytometer. The assay can distinguish between Influenza
types A and B in a single reaction with good reproducibility and high sensitivity [83].
21.2.6
Optical Biosensors
A report of the specific detection of a few hundred molecules of genetic material using a
fluorescent polythiophene biosensor. Such recognition is based on simple electrostatic
interactions between a cationic polymeric optical transducer and the negatively charged
nucleic acid target and can be done in less than 1 h, simply and affordably, and without
any chemical reaction. This simple system is versatile enough to detect nucleic acids of
various lengths, including a segment from the RNA genome of the influenza virus [84].
Light-Addressable Potentiometric Sensor
: A genetically biotinylated single-chain fragment
variable antibody (scFv) against Venezuelan equine encephalitis virus (VEE) was applied
in a system consisting of an immunofiltration enzyme assay (IFA) with a LAPS for the
rapid identification of VEE. The IFA involved formation of an immunocomplex sandwich
consisting of VEE, biotinylated antibody, fluoresceinated antibody and streptavidin,
capture of the sandwich by filtration on biotinylated membrane, and labeling of the sand-
wich by antifluorescein urease conjugate [85].
21.2.7
Piezoelectric-Based Acoustic Wave Devices
Faradaic Impedance Measurements and Quartz Crystal Microbalance Assay
: A drug composi-
tion consisting of nucleoside reverse transcriptase inhibitors (NRTIs), nonnucleoside
reverse transcriptase inhibitors (NNRTIs), and protease inhibitors (PIs) is commonly used
in AIDS therapy. A major difficulty encountered with the therapeutic composite involves
the emergence of drug-resistant virus, especially to the PIs, regarded as the most effective
drugs in the composition. The study presents a novel bioelectronic means to detect the
appearance of mutated HIV-1 exhibiting drug resistance to the PI saquinavir. The method
is based on the translation of viral RNA, the association of cleaved or uncleaved Gag
polyproteins at an electrode surface functionalized with the respective antibodies, and the
bioelectronic detection of the Gag polyproteins associated with the surface [86].
Piezoelectric-quartz-crystal resonators modified with oligonucleotide probes were used
for detection of HCV in serum. The gold electrodes on either rough or smooth surface
crystals were modified with a self-assembled monolayer of cystamine. After activation with
glutaraldehyde, either avidin or streptavidin was immobilized and used for attachment of
biotinylated DNA probes (four different sequences). Piezoelectric biosensors were used in a
flow-through setup for direct monitoring of DNA resulting from the reverse transcriptase-
linked polymerase chain reaction (RT-PCR) amplification of the original viral RNA [87].
Single Virus Particle Mass Detection Using Microresonators with Nanoscale Thickness
: This
study involves the microfabrication and application of arrays of silicon cantilever beams
as microresonator sensors with nanoscale thickness to detect the mass of individual virus
particles. The dimensions of the fabricated cantilever beams were in the range of 4-5
m
in length, 1-2
m in width, and 20-30 nm in thickness. The virus particles we used in the
study were vaccinia virus, which is a member of the Poxviridae family and forms the basis
of the smallpox vaccine. The frequency spectra of the cantilever beams, due to thermal and
ambient noise, were measured using a laser Doppler vibrometer under ambient condi-
tions. The change in resonant frequency as a function of the virus-particle mass binding
on the cantilever-beam surface forms the basis of the detection scheme [88].
