We presented an extensible multidimensional sensor with conjugated nonspecific dye-labeled DNA sequences absorbed onto gold nanoparticles (DNA-AuNPs) as receptors. At the presence of target protein, DNA was removed from the surface of AuNPs due to the competitive binding, which resulted in a red-to-blue color change along with salt-induced aggregation of AuNPs for colorimetric analysis and fluorescent "turn-on" signal of the labeled dye for fluorescence analysis. The orthogonal and complementary fluorescent and colorimetric signals obtained from each protein were applied to distinguish different proteins. By simply changing the DNA sequences, more dual-channel sensing elements could be easily obtained and added into this multidimensional sensor. This enhanced its discriminating power to the proteins. With three sensing elements, our extensible multidimensional sensing platform exhibited excellent discrimination ability. Eleven proteins at the concentration of 50 nM had been classified with accuracies of 100% by using linear discriminant analysis (LDA). Remarkably, two similar proteins [bovine serum albumin (BSA) and human serum albumin (HSA)] at various concentrations and the mixture of these two proteins with different molar ratios had been successfully discriminated in one LDA plot as well. Furthermore, in the presence of human urine sample, 10 proteins at 1.0 μM could also be well-discriminated. The accuracy of discrimination of unknown samples was all 100% for these experiments. This strategy is a complement of the multidimensional sensing system and traditional sensor platform, offering a new way to develop sensitive array sensing systems.

In vivo electrochemistry with a carbon-fiber electrode (CFE) is the most useful method for tracking neurochemicals in specific brain regions due to its high spatiotemporal resolution. However, CFE is inevitably subject to surface biofouling that leads to a decrease in sensitivity.Here, we develop a polytannic acid (PTA)-doped nanoporous conductive polyaniline (PANI) membrane-coated CFE to minimize biofouling-induced negative effects for in vivo analysis. The as-prepared PTA−PANI-coated CFE shows excellent antifouling property and enrichment capacity toward electrochemical measurement of dopamine (DA) in physiological pH. The PTA−PANI-coated CFE can in vivo monitor the release of DA induced by electrical stimulation and exhibits almost the same sensitivity in the postcalibration (S post ) and the precalibration (S pre ; S post /S pre = 0.90). We believe this conductive nanoporous membrane-coated CFE offers a new platform for in vivo measurement, which would help probe brain chemistry.

Single particle collision is emerging as a powerful and sensitive technique for analyzing small molecules, however, its application in biomacromolecules detection, for example, protein, in complex biological environments is still challenging. Here, we present the first demonstration on the single particle collision that can be developed for the detection of platelet-derived growth factor (PDGF), an important protein involved in the central nervous system in living rat brain. The system features Pt nanoparticles (PtNPs) conjugated with the PDGF recognition aptamer, suppressing the electrocatalytic collision of PtNPs toward the oxidation of hydrazine. In the presence of PDGF, the stronger binding between targeted protein and the aptamer disrupts the aptamer/PtNPs conjugates, recovering the electrocatalytic performance of PtNPs, and allowing quantitative, selective, and highly sensitive detection of PDGF in cerebrospinal fluid of rat brain.

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Optical cross-reactive sensor arrays have recently been demonstrated as a powerful tool for high-throughput protein analysis. Nevertheless, applying this technology to protein detection is complicated by many external factors, such as the interfering substances, the background noise, and sample environmental changes in the biological matrix. Herein we demonstrate that a ratiometric fluorescence sensor array based on quantum dots can be employed to circumvent these limitations. Several intrinsic dual-emitting Mn-doped quantum dots capped with different organic functional groups were designed as sensing elements. Distinct and reproducible response patterns against the ratiometric sensor array were obtained from ten proteins in a buffer of different pH (pH 5.7, 7.4, and 8.3) and spiked into human urine. Linear discrimination analysis of the response patterns showed successful differentiation of the analytes at concentrations as low as 50 nM with high identification accuracy. Furthermore, this sensor system also enables the detection of these eight proteins (at 500 nM) in human urine without any treatment. The ratiometric fluorescence change from quantum dots for analysis of proteins can eliminate effectively the signal interference from the pH value change and the fluorescent background in human urine. The present study will open a new avenue to improve the discrimination ability of sensor arrays.