Abstract
In previous work, the novel heat-transfer method (HTM) for the detection of small molecules with Molecularly Imprinted Polymers (MIP)-type receptors was presented. In this study we focus on optimization of this sensor performance, with as final aim to lower the detection limit by reducing the noise level. It was determined that the noise originates foremost from the power supply, which can be controlled by varying the PID parameters. Therefore, the effect of the individual parameters was evaluated by tuning P, I and D separately at a temperature of 37 °C, giving a first indication of the optimal configuration. Next, a temperature profile was programmed and the standard deviation of the heat-transfer resistance over the entire regime was studied for a set of parameters. The optimal configuration, P1-I6-D0, reduced the noise level with nearly a factor of three compared to the original parameters of P10-I5-D0. With the optimized settings, the detection of L-nicotine in buffer solutions was studied and the detection limit improved significantly from 100 nM to 35 nM. Summarizing, optimization of the PID parameters and thereby improving the detection limit is a key parameter for first applications of the HTM-method for MIP receptors in analytical research.
Highlights
Imprinted Polymers (MIPs) are synthetic materials which mimic the recognition and binding behavior of natural antibodies [1,2,3]
The measurements to study the PID settings are performed on a blank aluminum substrate with an area of 1 cm2 and a flow cell filled with 1× phosphate buffered saline (PBS) of pH 7.4
Molecularly Imprinted Polymers (MIP) and non-imprinted polymer (NIP) particles are applied to the surface with a polydimethylsiloxane (PDMS) stamp
Summary
Imprinted Polymers (MIPs) are synthetic materials which mimic the recognition and binding behavior of natural antibodies [1,2,3]. For proof-of-principle purposes, the response of a MIP to increasing L-nicotine concentrations in buffer solutions was studied and a detection limit of 100 nM in buffer solutions was achieved This is comparable to electrochemical impedance spectroscopy which was used as reference technique. The observed noise in the experiments is mainly due to changes in the voltage, necessary to keep the temperature of the copper constant In this manuscript other PID parameters are tested systematically and evaluated if they allow a better tradeoff in temperature and power control, resulting in a lower noise ratio of the overall heat-transfer resistance. Using the optimized PID parameters, the noise level is shown to reduce nearly threefold, lowering the detection limit to 35 nM This is well within the physiologically relevant range of L-nicotine, since salivary and urinary concentrations nicotine are in the micromolar regime, 0.2–1,000 μM in saliva and. Summarizing, the HTM method enables fast and low-cost measurements and optimizing the sensor performance is an important step for real analytical applications
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