A fast and simple label-free immunoassay based on a smartphone

Area of Science:

• Biomedical Engineering
• Analytical Chemistry
• Point-of-Care Diagnostics

Background:

• Developing portable, high-performance diagnostic devices faces challenges in balancing sensitivity, cost, and operational simplicity.
• Existing bio-molecular detection and fluidic systems require integration for practical diagnostic applications.

Purpose of the Study:

• To develop a compact, smartphone-based biosensing device for rapid and robust multi-target diagnostics.
• To leverage the Reflective Phantom Interface for sensitive detection of disease biomarkers.

Main Methods:

• A smartphone paired with a custom cradle containing a disposable sensing cartridge, magnetic stirrer, and passive optical components.
• Utilizing the Reflective Phantom Interface principle to measure light reflectivity changes on an antibody-functionalized substrate.
• Employing the smartphone camera and LED flash for real-time monitoring of spot reflectivity.

Main Results:

• The device successfully detected heterologous immunoglobulins and antigens, markers for hepatitis B and HIV.
• Achieved rapid and robust determination of target concentrations as low as a few ng/ml.
• Demonstrated a method for quantifying targets by comparing signal increase rates with standard solutions.

Conclusions:

• The proposed smartphone-based biosensor offers a novel, handheld solution for rapid, multi-target detection.
• Suitable for applications requiring diagnostics without trained personnel, enhancing accessibility.
• Addresses the need for sensitive, low-cost, and user-friendly diagnostic tools.