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Integrating PDMS channels and chips containing pre-functionalized biosensors into microfluidic devices with irreversible sealing has been challenging because the integration process requires use of an O2 plasma treatment that usually destroys the biosensors. In this study, we examined the usefulness of introducing a shadow mask into the process as a method of protecting the pre-functionalized biosensors. Single nanowire sensors were pre-functionalized with fluorescently labeled biomolecules and then subjected to O2 plasma with and without the shadow mask. Results from the two groups were then compared. Those sensors without a shadow mask were destroyed, giving the sensor an infinite resistance and reduced fluorescence intensity. In contrast, the sensors with the shadow mask were protected and exhibited little changes in the resistance and fluorescence intensity. Then two different nanowires, aptamers incorporated polypyrrole nanowire (entrapment) and antibodies immobilized polyaniline nanowire (surface covalent binding), were used to investigate their detection performance before and after the plasma treatment in the presence of shadow mask. The protected samples showed a good sensitivity to the targets with a slight reduction in response compared with the as-prepared samples. After the O2 plasma treatment, the microfluidic channels were integrated with single nanowire biosensors. This microfluidic biosensor showed a high sensitivity with about ~0.5 % change in conductance at the lowest IgE protein concentration of 10 pM.

A highly sensitive, conductometric and label-free biosensor for the detection of immunoglobulin E (IgE) is developed based on the immobilzation of the IgE aptamer onto a single polyaniline nanowire electrochemically synthesized in a facile and controllable way., (This journal is © The Royal Society of Chemistry 2011)

Abstract: Single polypyrrole (PPy) nanowire-based microfluidic aptasensors were fabricated using a one-step electrochemical deposition method. The successful incorporation of the aptamers into the PPy nanowire was confirmed by fluorescence microscopy image. The microfluidic aptasensor showed responses to IgE protein solutions in the range from 0.01nM to 100nM, and demonstrated excellent specificity and sensitivity with faster response and rapid stabilization times (∼20s). At the lowest examined IgE concentration of 0.01nM, the microfluidic aptasensor still exhibited ∼0.32% change in the conductance. The functionality of this aptasensor was able to be regenerated using an acid treatment with no major change in sensitivity. In addition, the detection of cancer biomarker MUC1 was performed using another microfluidic aptasensor, which showed a very low detection limit of 2.66nM MUC1 compared to commercially available MUC1 diagnosis assay (800nM). [Copyright &y& Elsevier]

Abstract: Recognition and separation of chiral molecules is of great importance in the field of biotechnology, especially on pharmaceutics. Molecular imprinted polymers (MIP) have been proved as a powerful tool for the separation of target molecules. In this paper, polypyrrole (PPy) nanowires with an average diameter of ca. 100nm and few micrometers in length were successfully prepared by electrochemical polymerization, in which enantiomeric camphorsulfonic acid (d- or l-CSA) molecule acted as both the dopant and molecular imprinting pseudo-template. Both electrochemical impedance spectra (EIS) and circular dichroism (CD) spectra were employed to demonstrate the enantioselective interaction between de-doped PPy nanowires imprinted with CSA enantiomers (MIP-PPy) and chiral phenylalanine (d- or l-Phe). EIS leads to the characterization of interfacial electron resistance of the PPy coated electrode, while CD spectra provides spectral evidence for the enantioselective recognition event. Both methods proved that MIP-PPy nanowires have the capability for the recognition and separation of chiral phenylalanine. The sensitivity of the chiral recognition was further investigated by using various concentrations of chiral Phe and adsorption time. This approach provides a potential route for fabricating enantioselective recognition polypyrrole nanostructures that could be employed in enantiomeric sensoring or separating various chiral molecules. [Copyright &y& Elsevier]