Despite
a large number of publications describing biosensors based
on electrochemical impedance spectroscopy (EIS), little attention
has been paid to the stability and reproducibility issues of the sensor
interfaces. In this work, the stability and reproducibility of faradaic
EIS analyses on the aptamer/mercaptohexanol (MCH) self-assembled monolayer
(SAM)-functionalized gold surfaces in ferri- and ferrocyanide solution
were systematically evaluated prior to and after the aptamer-probe
DNA hybridization. It is shown that the EIS data exhibited significant
drift, and this significantly affected the reproducibility of the
EIS signal of the hybridization. As a result, no significant difference
between the charge transfer resistance (R
CT) changes induced by the aptamer-target DNA hybridization and that
caused by the drift could be identified. A conditioning of the electrode
in the measurement solution for more than 12 h was required to reach
a stable R
CT baseline prior to the aptamer-probe
DNA hybridization. The monitored drift in R
CT and double layer capacitance during the conditioning suggests that the MCH SAM on the gold surface
reorganized to a thinner but more closely packed layer. We also observed
that the hot binding buffer used in the following aptamer-probe DNA
hybridization process could induce additional MCH and aptamer reorganization,
and thus further drift in R
CT. As a result,
the R
CT change caused by the aptamer-probe
DNA hybridization was less than that caused by the hot binding buffer
(blank control experiment). Therefore, it is suggested that the use
of high temperature in the EIS measurement should be carefully evaluated
or avoided. This work provides practical guidelines for the EIS measurements.
Moreover, because SAM-functionalized gold electrodes are widely used
in biosensors, for example, DNA sensors, an improved understanding
of the origin of the observed drift is very important for the development
of well-functioning and reproducible biosensors.
A single compartment biofuel cell (BFC) based on an anode and a cathode powered by the same fuel glucose is reported. Glucose oxidase (GOx) from Aspergillus niger was applied as a glucose consuming biocatalyst for both anode and cathode of the BFC. The 5‐amino‐1,10‐phenanthroline modified graphite rod electrode (GRE) with cross‐linked GOx was used as the bioanode, and the GRE with co‐immobilised horseradish peroxidase and GOx was exploited as the biocathode of the BFC. The open‐circuit voltage of the designed BFC exceeded 450 mV and a maximal power density of 3.5 µW/cm2 was registered at a cell voltage of 300 mV.
Half-antibody fragments are a promising reagent for biosensing, drug-delivery and labeling applications, since exposure of the free thiol group in the Fc hinge region allows oriented Preferential reduction of rabbit anti-myoglobin IgG antibodies was optimized and the highest half-antibody yield was obtained with 35 mM TCEP. Finally, it has been demonstrated that produced anti-myoglobin half-IgG fragments retained their binding activity.
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