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Flexible nanoporous tunable electrical double layer biosensors for sweat diagnostics.

Munje RD, Muthukumar S, Panneer Selvam A, Prasad S - Sci Rep (2015)

Bottom Line: High sensitivity of detection of 1 pg/mL or 2.75 pmol cortisol in synthetic sweat and 1 ng/mL in human sweat is demonstrated with these novel biosensors.Specificity in synthetic sweat was demonstrated using a cytokine IL-1β.Cortisol detection in human sweat was demonstrated over a concentration range from 10-200 ng/mL.

View Article: PubMed Central - PubMed

Affiliation: Department of Bioengineering, University of Texas at Dallas, 800 W. Campbell Road, EC 39, Richardson, TX 75080.

ABSTRACT
An ultra-sensitive and highly specific electrical double layer (EDL) modulated biosensor, using nanoporous flexible substrates for wearable diagnostics is demonstrated with the detection of the stress biomarker cortisol in synthetic and human sweat. Zinc oxide thin film was used as active region in contact with the liquid i.e. synthetic and human sweat containing the biomolecules. Cortisol detection in sweat was accomplished by measuring and quantifying impedance changes due to modulation of the double layer capacitance within the electrical double layer through the application of a low orthogonally directed alternating current (AC) electric field. The EDL formed at the liquid-semiconductor interface was amplified in the presence of the nanoporous flexible substrate allowing for measuring the changes in the alternating current impedance signal due to the antibody-hormone interactions at diagnostically relevant concentrations. High sensitivity of detection of 1 pg/mL or 2.75 pmol cortisol in synthetic sweat and 1 ng/mL in human sweat is demonstrated with these novel biosensors. Specificity in synthetic sweat was demonstrated using a cytokine IL-1β. Cortisol detection in human sweat was demonstrated over a concentration range from 10-200 ng/mL.

No MeSH data available.


Sensor performance evaluation in synthetic sweat using AC modulation through EIS.(a) Change in imaginary impedance Zimag for varying cortisol concentration of 1 pg/mL to 100 ng/mL on nanoporous polyamide surface with ZnO. (b) Change in imaginary impedance Zimag for varying cortisol concentration of 1 pg/mL to 100 ng/mL on planar glass surface with ZnO. (c) Change in total impedance Zmod for varying cortisol concentration of 1 pg/mL to 100 ng/mL. In all cases inset represents percentage change in impedance with respect to baseline i.e. zero dose. (d) Comparison of sensor performance parameters obtained after analyzing EIS measurements for ZnO thin films on planar glass vs. nanoporous flexible substrate.
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f3: Sensor performance evaluation in synthetic sweat using AC modulation through EIS.(a) Change in imaginary impedance Zimag for varying cortisol concentration of 1 pg/mL to 100 ng/mL on nanoporous polyamide surface with ZnO. (b) Change in imaginary impedance Zimag for varying cortisol concentration of 1 pg/mL to 100 ng/mL on planar glass surface with ZnO. (c) Change in total impedance Zmod for varying cortisol concentration of 1 pg/mL to 100 ng/mL. In all cases inset represents percentage change in impedance with respect to baseline i.e. zero dose. (d) Comparison of sensor performance parameters obtained after analyzing EIS measurements for ZnO thin films on planar glass vs. nanoporous flexible substrate.

Mentions: The modulation in CEDL was captured using AC measurements in the form of EIS. Figure 3 shows the results of calibration of EIS measurements for cortisol concentrations of 1 pg/mL to 100 ng/mL along with the measurement at zero dose, which is considered to be baseline measurement. This baseline measurement was carried out for the synthetic sweat buffer of pH ~ 4–8, on nanoporous flexible substrate with ZnO. It was observed that the baseline measurement (in terms of Zmod) at 1 Hz varied from 312 kΩ to 340 kΩ and at 1 KHz from 1.6 kΩ to 2.4 kΩ within the pH range of 4–8 (see Supplementary Fig. S1 online) and thus did not vary substantially. Further measurements were carried out using synthetic sweat at pH 8. EIS measurements track the dynamics of changing Zreal i.e. resistive and Zimag i.e. imaginary (mainly capacitive) impedance of the sensor system. Hence EIS can be used to find out critical performance parameters of sensors such as limit of blank (LOB), limit of detection (LOD) and linear dynamic range (LDR).


Flexible nanoporous tunable electrical double layer biosensors for sweat diagnostics.

Munje RD, Muthukumar S, Panneer Selvam A, Prasad S - Sci Rep (2015)

Sensor performance evaluation in synthetic sweat using AC modulation through EIS.(a) Change in imaginary impedance Zimag for varying cortisol concentration of 1 pg/mL to 100 ng/mL on nanoporous polyamide surface with ZnO. (b) Change in imaginary impedance Zimag for varying cortisol concentration of 1 pg/mL to 100 ng/mL on planar glass surface with ZnO. (c) Change in total impedance Zmod for varying cortisol concentration of 1 pg/mL to 100 ng/mL. In all cases inset represents percentage change in impedance with respect to baseline i.e. zero dose. (d) Comparison of sensor performance parameters obtained after analyzing EIS measurements for ZnO thin films on planar glass vs. nanoporous flexible substrate.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4588585&req=5

f3: Sensor performance evaluation in synthetic sweat using AC modulation through EIS.(a) Change in imaginary impedance Zimag for varying cortisol concentration of 1 pg/mL to 100 ng/mL on nanoporous polyamide surface with ZnO. (b) Change in imaginary impedance Zimag for varying cortisol concentration of 1 pg/mL to 100 ng/mL on planar glass surface with ZnO. (c) Change in total impedance Zmod for varying cortisol concentration of 1 pg/mL to 100 ng/mL. In all cases inset represents percentage change in impedance with respect to baseline i.e. zero dose. (d) Comparison of sensor performance parameters obtained after analyzing EIS measurements for ZnO thin films on planar glass vs. nanoporous flexible substrate.
Mentions: The modulation in CEDL was captured using AC measurements in the form of EIS. Figure 3 shows the results of calibration of EIS measurements for cortisol concentrations of 1 pg/mL to 100 ng/mL along with the measurement at zero dose, which is considered to be baseline measurement. This baseline measurement was carried out for the synthetic sweat buffer of pH ~ 4–8, on nanoporous flexible substrate with ZnO. It was observed that the baseline measurement (in terms of Zmod) at 1 Hz varied from 312 kΩ to 340 kΩ and at 1 KHz from 1.6 kΩ to 2.4 kΩ within the pH range of 4–8 (see Supplementary Fig. S1 online) and thus did not vary substantially. Further measurements were carried out using synthetic sweat at pH 8. EIS measurements track the dynamics of changing Zreal i.e. resistive and Zimag i.e. imaginary (mainly capacitive) impedance of the sensor system. Hence EIS can be used to find out critical performance parameters of sensors such as limit of blank (LOB), limit of detection (LOD) and linear dynamic range (LDR).

Bottom Line: High sensitivity of detection of 1 pg/mL or 2.75 pmol cortisol in synthetic sweat and 1 ng/mL in human sweat is demonstrated with these novel biosensors.Specificity in synthetic sweat was demonstrated using a cytokine IL-1β.Cortisol detection in human sweat was demonstrated over a concentration range from 10-200 ng/mL.

View Article: PubMed Central - PubMed

Affiliation: Department of Bioengineering, University of Texas at Dallas, 800 W. Campbell Road, EC 39, Richardson, TX 75080.

ABSTRACT
An ultra-sensitive and highly specific electrical double layer (EDL) modulated biosensor, using nanoporous flexible substrates for wearable diagnostics is demonstrated with the detection of the stress biomarker cortisol in synthetic and human sweat. Zinc oxide thin film was used as active region in contact with the liquid i.e. synthetic and human sweat containing the biomolecules. Cortisol detection in sweat was accomplished by measuring and quantifying impedance changes due to modulation of the double layer capacitance within the electrical double layer through the application of a low orthogonally directed alternating current (AC) electric field. The EDL formed at the liquid-semiconductor interface was amplified in the presence of the nanoporous flexible substrate allowing for measuring the changes in the alternating current impedance signal due to the antibody-hormone interactions at diagnostically relevant concentrations. High sensitivity of detection of 1 pg/mL or 2.75 pmol cortisol in synthetic sweat and 1 ng/mL in human sweat is demonstrated with these novel biosensors. Specificity in synthetic sweat was demonstrated using a cytokine IL-1β. Cortisol detection in human sweat was demonstrated over a concentration range from 10-200 ng/mL.

No MeSH data available.