Colorimetric nano-biosensor for low-resource settings: insulin as a model biomarker.

Area of Science:

• Biomedical Engineering
• Analytical Chemistry
• Biosensing Technology

Background:

• Biomarker detection at ultra-low concentrations is crucial for disease diagnosis but challenging in resource-limited settings.
• Existing methods often require sophisticated instrumentation, hindering point-of-need applications.
• Insulin is a key biomarker for glucose metabolism and diabetes management.

Purpose of the Study:

• To develop an equipment-free, colorimetric immunosensor for ultra-sensitive insulin detection.
• To evaluate the sensor's performance in various biological matrices like buffer, serum, and saliva.
• To demonstrate the potential application of the sensor for diabetes diagnostics.

Main Methods:

• A two-antibody sandwich immunoassay format was employed.
• Citrate-functionalized magnetic nanoparticles were used for target capture and isolation.
• Horseradish peroxidase (HRP) labeling enabled colorimetric detection of insulin.
• Comparative analysis was performed in buffer, diluted serum, and diluted artificial saliva samples.

Main Results:

• The developed immunosensor achieved a detection limit of 10 picomolar (pM) for insulin.
• Dynamic ranges varied across matrices: 10 pM–1 nM (buffer), 10 pM–10 nM (serum), and 50 pM–1 nM (saliva).
• Successful application was demonstrated in type 1 diabetes and healthy human serum samples.

Conclusions:

• The study successfully developed a sensitive, equipment-free colorimetric immunosensor for insulin detection.
• This technology enhances biomarker analysis in biofluids, suitable for point-of-need applications.
• Further optimization is needed to improve detection limits for human saliva analysis.