Biomedical Engineering Reference
In-Depth Information
redox state. h e magnitude and the strength of the dif erence in potential
were eventually related to the concentration of the receptor-target complex
which was formed. h e bio-sensor was applied for detecting hepatitis B
surface antigen, Digoxin, Troponin I and tumour necrosis factor in general.
h is technology and tools used was found to be ultrasensitive, rapid and
reproducible and had a wide dynamic range. Feng
et al.
[58], has reported a
potentiometric immune-sensor for detecting the immunoglobin G (IgG).
h e immune-sensor was commonly based on covalent immobilization of
specii c anti-immunoglobin G on the silver (Ag) electrode. Before and at er
the antigen-antibody reaction the change in electric potential was specii c
noticed which were said to be based on change in the detection. Immune-
sensor for detection α-2 interferon which was based on pH sensitive i eld
ef ect the transistor (pH FET) was fabricated by Sergeyeva
et al.
[59]. h e
immobilizing α-2 interferon on the gate of pH FET, fabricated the sens-
ing element. h e interaction of anti-interferon antibodies which has been
labelled with β-lactamase and with interferon- pH-FET (in the presence
of specii c enzyme substrate) leads to a local pH-change at the surface of
transducer and i nally produces an electrochemical signal which was pro-
portional to the conjugate concentration of the complex. h e conventional
ELISA assays, accounted for analytical data obtained.
Amperometric immune-sensors are designed to measure a current l ow
indigenously generated by an electrochemical reaction at constant voltage
every time. h ere are very less applications available for direct sensing as
such, most (protein) of analytes are not intrinsically and superi cially able
to act as redox couples in an electrochemical reaction at constant volt-
age. h erefore, electrochemically active labels which is directly acting as
products of an enzyme reaction) are always needed for the electrochemical
reaction of the analyte at the sensing electrode in assay.
An antiseptic and disposable amperometric immune-migration sensor
for the detecting the triazine pesticides in real samples and specimen using
the monoclonal antibodies against atrazine and tertbutylazine as bio-rec-
ognition element in the reaction was eventually fabricated by Bäumner
and Schmid [60]. Generation and amplii cation of the signal was greatly
achieved and enhanced by using hapten-tagged liposomes entrapping the
ascorbic acid as a marker molecule. An amperometric immune-sensor
used for the detection of red blood cells which was based on a non-compet-
itive sandwich assay and l ow injection analysis (FIA) was developed and
enhanced by Lu
et al.
[61]. Specii c IgM and non specii c IgM were chemi-
cally immobilised on two specii c electrodes to form the blank electrodes
and sensing electrodes, respectively. It has been employed and assisted for
the determination of the binding of specii c blood cells and non-specii c
