Related Experiment Video
Updated: Aug 6, 2026
08:37
Development of a Quantitative Recombinase Polymerase Amplification Assay with an Internal Positive Control
Published on: March 30, 2015
PEG-mediated viscous crowding controls dynamics and quantitative range in recombinase polymerase amplification
Coleman D Martin1, Nandini S Gummalla2, Kelli N Shimazu2
1Department of Chemical Engineering, University of Washington Seattle Washington USA.
Sensors & Diagnostics
|July 23, 2026
Summary
This study introduces a novel digital isothermal nucleic acid amplification test (NAAT) on a microfluidic chip. It achieves precise, low-cost HIV viral load quantification for point-of-need diagnostics.
Area of Science:
- Biotechnology
- Molecular Diagnostics
- Microfluidics
Background:
- Quantitative nucleic acid amplification tests (NAATs) are crucial for diagnostics but often require complex laboratory equipment.
- Existing point-of-need isothermal amplification assays lack quantitative precision and a broad dynamic range.
- Developing rapid, accurate, and cost-effective nucleic acid quantification methods for field use is a significant challenge.
Purpose of the Study:
- To develop a digital isothermal NAAT on a membrane-free microfluidic chip for precise quantification.
- To optimize recombinase polymerase amplification (RPA) chemistry using polyethylene glycol (PEG) for improved nucleation site control.
- To enable rapid, calibration-free HIV viral load measurements at the point-of-need.
Main Methods:
- Investigated digital isothermal NAAT on a microfluidic chip using recombinase polymerase amplification (RPA) and polyethylene glycol (PEG).
- Employed amplification nucleation site analysis (ANSA) with real-time epifluorescence imaging to study nucleation dynamics.
- Systematically tuned PEG concentration to control amplification site formation and separation.
Main Results:
- Nucleation sites exhibited Gaussian spatial intensity profiles with predictable temporal evolution.
- Increasing PEG concentration reduced site diameter, enabling better discrimination of amplification events (8% PEG optimal).
- Achieved quantitative detection of HIV DNA from 10^2 to 10^6 copies/reaction over a 4-log dynamic range (R^2 = 0.94).
Conclusions:
- The developed microfluidic chip offers a low-cost, simple alternative to digital PCR for nucleic acid quantification.
- PEG-tuned ANSA on a membrane-free chip enables rapid, calibration-free HIV viral load measurement within the clinical range.
- This technology holds promise for point-of-need diagnostics in resource-limited settings.
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