Development of a fluorescence microplate reader using an organic photodiode array with a large light receiving area.

Area of Science:

• Biophotonics
• Analytical Chemistry
• Biomedical Engineering

Background:

• Microplate readers are essential for biological and chemical analysis.
• Existing readers face limitations in sensitivity and detection limits.
• Organic photodiode (OPD) technology offers potential for enhanced optical detection.

Purpose of the Study:

• To develop a compact fluorescence microplate reader utilizing an organic photodiode (OPD) array.
• To evaluate the analytical performance and sensitivity of the developed reader.
• To demonstrate the reader's utility in quantifying biomarkers like immunoglobulin A (IgA).

Main Methods:

• Fabrication of a microplate reader incorporating a nine-element organic photodiode (OPD) array with large light-receiving areas (9.62 mm² per OPD).
• Positioning the OPD array directly beneath microwells for efficient fluorescence capture.
• Analytical validation using resorufin solutions to determine the limit of detection (LOD).
• Quantification of immunoglobulin A (IgA) in human saliva samples.

Main Results:

• The developed reader achieved a significantly lower limit of detection (LOD) for resorufin (0.01–0.05 μM) compared to previous inorganic photodiode readers (0.30 μM) and commercial readers (0.16 μM).
• The large light-receiving area of the OPD array was identified as the key factor for improved detection performance.
• The reader successfully quantified immunoglobulin A (IgA) in human saliva with an LOD of 1.2 ng/mL.

Conclusions:

• The developed small fluorescence microplate reader with an organic photodiode (OPD) array demonstrates superior analytical performance.
• The system's enhanced sensitivity, attributed to the large light-receiving area of the OPDs, is suitable for sensitive biomarker quantification.
• This technology holds promise for objective human stress evaluation via saliva IgA measurement.