Wen Sang - Microfluidic Biosensor

Microfluidic Biosensor

Microfluidic Biosensor for Detecting Trace Amount of TNT

Simple and sensitive colorimetric detection of a trace amount of 2,4,6-trinitrotoluene (TNT) with QD multilayer-modified microchannel assays

Multilayer quantum dots (red and green) deposited in microfluidic channels
Rapid and selective detection of trace levels of TNT molecules
With fluorescence assay, the sensor has a broad linear range of 10 ppt to 10^7 ppt and low detection limit (5.24 ppt) for TNT molecules
This technique was successfully applied to detect TNT concentration in different water samples

Schemefor fabrication of QD multilayers-coated film for visual determination of TNT and the detection mechanism. Green QDs and red QDs were sequentially deposited on glass slides using a layer-by-layer (LbL) assembly technique. Due to the Förster resonance energy transfer (FRET) that occurs between the red and green QDs, the fluorescence intensity of the red QDs was markedly enhanced.

Fluorescence emission spectra of quantum dots multilayers deposited on glass substrates in the presence of different concentrations of TNT at 365 nm excitation

(a) FL spectra of (PEI/PSS)3(PAH/green QDs)10(PAH/PSS)3(PAH/red QDs)5 multilayers before and after the addition of different concentrations of TNT: 0 (black curve), 10 (red curve), 10^2 (blue curve) and 10^4 ppt (dark cyan curve) and pure TNT solution (magenta curve).

(b) Photo images of (PEI/PSS)3(PAH/green QDs)10(PAH/PSS)3(PAH/red QDs)5 multilayers before and after the addition of different concentrations of TNT

(c) Dependence of the fluorescence emission intensity ratio (I520/I620) of QD multilayers on the logarithm of TNT concentration

Scheme for detection process

(a) Assembly process of (PEI/PSS)3(PAH/green QDs)10(PAH/PSS)3(PAH/red QDs)5 multilayers-based microchannel assays. The diameter of microchannels is 100 mm.

Results of fluorescence assay

(b) Photographs of microchannel assays before and after exposure to TNT of difference concentration. The photo was taken under a 365 nm UV lamp.

(c) Response toward different TNT analogs. The concentration of TNT analogs is 10^5 ppt.

(d) Visual determination of TNT in real samples. It is noteworthy that the color change of the assays for TNT solution and different TNT analogs of the same concentration is identical.

Microfluidic Biosensor for Detecting Tumor Biomarkers

Graphene aerogel (GA) microfluidic biosensor for electrochemical detection of trace amount of tumor biomarkers

Multilayer graphene aerogel modified with antibody molecules
ITO coated microfluidic channel
Three-electrode electrochemical model
For selective detection of tumor biomarkers (antigens and exosomes) with a high sensitivity, low limit of detection

Nanofabrication

The channel is 80 µm in height made through laser etching
Graphene aerogel was synthesized in situ through L-ascorbic acid reduction reaction and freeze-drying
ITO pattern was obtained by laser etching
The graphene aerogel was activated with sulfo-NHS and EDC, followed by chemical conjunction of antibody molecules

Three-electrode electrochemical detection

With two ITO coatings as working and counter electrodes and a Ag/AgCl wire in the outlet reservoir as the reference electrode

Detection of exosomes

The graphene aerogel on the ITO electrode was modified with anti-EpCAM
The EIS signal of selected exosomes A549 was much higher than that of normal cell derived exosomes (NC)
SEM images showed a massive amount of exosomes captureed on the surface of the graphene aerogel, while only scattered exosomes were found on the modified ITO surface

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