pH Quantification in Human Dermal Interstitial Fluid Using Ultra-Thin SOI Silicon Nanowire ISFETs and a...

Area of Science:

• Nanotechnology
• Biosensors
• Analytical Chemistry

Background:

• Accurate pH monitoring is crucial for diagnosing various physiological conditions.
• Existing pH sensors face challenges in sensitivity and real-time application in complex biological matrices.
• Silicon nanowire Ion Sensitive Field Effect Transistors (ISFETs) offer potential for enhanced sensing capabilities.

Purpose of the Study:

• To introduce and validate a novel constant current method for silicon nanowire ISFET-based pH sensing.
• To demonstrate the suitability of this method for high-sensitivity, real-time pH measurements in human biofluids.
• To compare the performance of the constant current method against the conventional top-gate approach.

Main Methods:

• Utilizing silicon nanowires as ISFETs with a fixed current bias, monitoring drain voltage for pH sensing.
• Optimizing sensing by fine-tuning injected current levels for different sensor requirements.
• Validating the method using real human sera samples and direct interstitial fluid (ISF) samples.

Main Results:

• Achieved high accuracy pH sensing (6.5-8 range) in human sera, with a maximum error of 0.92% (0.07 pH unit) using the constant current method.
• Demonstrated that varying protein content in sera does not affect sensor performance.
• Obtained outstanding accuracy in real ISF samples, with errors as low as 0.015 pH unit (constant current) vs. 0.178 pH unit (top-gate).

Conclusions:

• The proposed constant current method significantly enhances the accuracy and reliability of silicon nanowire pH sensors.
• This approach is highly suitable for continuous and real-time monitoring of physiological pH in complex biological samples.
• The developed sensor technology holds promise for advanced diagnostic tools in healthcare.