3.7. Stability and selectivity of the biosensor
We also evaluated the stability of the proposed biosensor by
employing one prepared biosensor incubated with 10 ng mL1 β-
lactamase for consecutive cyclic potential scans. As we can see
from Fig. 4A, under continuous cyclic potential scans for 14 cycles
at a scan rate of 100 mV s1
, the relative standard deviation (RSD)
of ECL was 0.89%. The result suggested that the proposed biosensor
had acceptable stability. The repeatability of the biosensor
was tested by using five proposed biosensors incubated with
10 ng mL1 β-lactamase. The prepared electrodes exhibited closely
ECL responses and the RSD of 1.75%, which was acceptable for
detection of β-lactamase. The storage stability of the prepared
biosensor was also tested by monitoring of its ECL response. It was
found that the ECL response of the biosensor decreased 1.4% one
week later. Thus, the proposed biosensor was sensitive and stable
for the detection of β-lactamase.
To investigate the selectivity and specificity of the present
biosensor, it was incubated with different interfering substances
such as ALP and TB. As shown in Fig. 4B, the control experiments
were performed by using ALP (100 ng mL1
) and TB (100 nM) to
replace β-lactamase (1 ng mL1
), respectively. We can see that the
ECL signal of ALP and TB exhibited a small decrease compared
with the blank. The biosensor was also incubated with 1 ng mL1
β-lactamase containing ALP (100 ng mL1
) and TB (100 nM),
compared with the ECL response obtained from the 1 ng mL1 β-
lactamase only, no remarkable difference was found. The result
suggested that the ECL intensity response to β-lactamase was
much higher than those of the others, which meant that ALP and
TB had no obvious influence on the ECL response to β-lactamase.
Fig. 2