Sensitive, smartphone-based SARS-CoV-2 detection from clinical saline gargle samples.

Area of Science:

• Biomedical Engineering
• Infectious Disease Diagnostics
• Microfluidics

Background:

• Saliva is a promising specimen for respiratory virus diagnosis due to ease of collection and reduced healthcare provider risk.
• Current immunoassays struggle with saliva's viscosity and low viral loads, limiting their sensitivity and speed.
• Accurate and rapid diagnostics are crucial for managing respiratory viral infections like COVID-19.

Purpose of the Study:

• To develop a highly sensitive and low-cost immunofluorescence assay for SARS-CoV-2 detection in saliva.
• To utilize paper microfluidic chips and smartphone-based fluorescence microscopy for improved diagnostics.
• To evaluate the clinical performance of the developed assay using saline gargle samples.

Main Methods:

• Development of a paper microfluidic chip for sample processing.
• Implementation of a smartphone-based fluorescence microscope for signal detection.
• Design of an immunofluorescence particulometric assay targeting SARS-CoV-2.
• Validation using clinical saline gargle samples from human subjects.

Main Results:

• The assay demonstrated a limit of detection of 10 ag/μL.
• Clinical evaluation showed 100% sensitivity, 86% specificity, and 93% accuracy.
• The assay successfully detected SARS-CoV-2 in easy-to-collect saline gargle samples.

Conclusions:

• The developed paper microfluidic and smartphone-based assay is a sensitive, low-cost tool for SARS-CoV-2 detection in saliva.
• This diagnostic approach offers high clinical performance and potential for widespread use in respiratory viral infection diagnosis.
• The method overcomes challenges associated with saliva viscosity and low viral loads, enhancing diagnostic accessibility.