Therefore, only the cellulose membrane was replaced by the gold-coated
micropillar array substrate in our design strategy. This strategy has several advantages as follows: First of all, it economizes the consumption of gold-coated substrate and facilitates the homogeneous batch processing. Second, it is a mature technique in practice to process the sample pad, conjugate pad, and absorbent pad, which works well and does not need further optimization. Third, wide center-to-center distance guarantees a good passing ability, avoiding the blocking of possible residual coarse materials passing through sample pad in samples. Last but not the least, this design, which decreased the width of flow path in conventional LF test strips from 4 to 1 mm, facilitates the enriching of analytes on the surface of the capture zone, improving the sensitivity under the condition of high flow rate. In other words, this strategy reduced not only the complication Selleck LB-100 of fabrication, but also the overall cost. Figure 4 Characterization of capillary-driven SERS microfluidic chip. Analysis of abrin-spiked sample Figure 5 shows the SERS spectra of the abrin-spiked sample at various concentrations. The intensity of the peak at approximate 1,330 cm-1 was proportional to the concentration of abrin in the PBS solution. The concentration of abrin Selleck NU7026 ranged from 0.1 ng/mL to 1 μg/mL. The characteristic peak under 0.1 ng/mL
became difficult to distinguish from that of the blank sample, indicating the limit of detection (LOD). Because of the Roflumilast absence of the washing step, some SERS probes remained on the gold-coated substrate, resulting in a weak nonspecific binding peak at approximate
1,330 cm-1. Figure 6 shows the dose-response curve calculated by averaging the readout at three different locations of each concentration from 0.1 to 100 ng/mL. The linear regression equation was y =1,430.7x – 2,312.5 and the correlation coefficient (R 2) was 0.9902. The LOD of this capillary-driven SERS-based microfluidic chip was 0.1 ng/mL. Figure 5 SERS spectra of the abrin-spiked sample at different concentrations. Figure 6 Dose–response curve for the abrin-spiked sample at different concentrations. As previously mentioned, SERS-based techniques showed many potential advantages including high sensitivity, narrow bandwidths, and photobleaching resistance. It still remains a challenge to develop a SERS-based immunodiagnostic technique of both low cost and good operability. Some pioneering researchers have published their works focusing on the buy Z-VAD-FMK ultrasensitivity from the level of picograms per milliliter to femtograms per milliliter [6, 8, 9, 11, 14, 23–28]. Compared with their work, our design strategy emphasized the operability of SERS-based technique. In other words, this strategy is aimed at not just a comparative LOD, but a balanced solution between the complication of new techniques and the universality of traditional ones.