Simultaneous quantification in biosensing In food and clinical biosensors, which device can be used to determine inosine and hypoxanthine simultaneously from the same sample?

Introduction / Context:
Inosine and hypoxanthine are key freshness and purine catabolism markers in foods (for example, fish muscle) and clinical samples. A biosensor that measures both simultaneously improves speed and reduces sample handling errors.

Given Data / Assumptions:

• The goal is simultaneous (same device, same run) measurement.
• Biosensors require biochemical recognition (enzymes) specific to each analyte.
• Generic physicochemical sensors without immobilized biorecognition elements lack selectivity.

Concept / Approach:
Dual-analyte biosensors co-immobilize enzymes such as nucleoside phosphorylase/xanthine oxidase cascades, or use spatially resolved microarrays on one transducer. The combined design generates a measurable signal for both inosine and hypoxanthine, enabling concurrent quantification.

Step-by-Step Solution:

Verification / Alternative check:
Analytical chemistry literature describes screen-printed electrodes or amperometric probes with co-immobilized enzyme systems for concurrent inosine/hypoxanthine sensing in fish quality testing.

Why Other Options Are Wrong:

• Inosine sensor: single target; does not quantify hypoxanthine simultaneously.
• Amorphous-silicon ISFET without enzymes: lacks specificity to these purines.
• Urea sensor: selective for urea via urease; irrelevant here.
• Na⁺ electrode: measures sodium ions, not purines.

Common Pitfalls:
Assuming any ISFET or electrode can detect specific metabolites without biorecognition; specificity requires enzymes or aptamers.

Final Answer:
Dual inosine–hypoxanthine sensor (combined bi-enzymatic design)