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Sensing DNA-coatings of microparticles using micropipettes
L J Steinbock1, G Stober, U F Keyser
1Institute for Experimental Physics I, University of Leipzig, Linné Str. 5, 04103 Leipzig, Germany.
Biosensors & Bioelectronics
|January 28, 2009
Summary
This study shows that a Coulter counter can detect DNA molecules on particles. The technique uses pressure-driven flow through a microcapillary to sense surface charges on colloids.
Area of Science:
- Colloid and Surface Science
- Nanotechnology
- Biophysics
Background:
- Resistive pulse technique is a standard method for particle sizing.
- Detecting surface charges on micro- and nanoparticles is crucial for various applications.
- Optical detection combined with electrical sensing offers enhanced particle characterization.
Purpose of the Study:
- To demonstrate the detection of DNA molecules on colloidal particles using a microcapillary Coulter counter.
- To investigate the sensitivity of the Coulter counter to surface charge variations.
- To validate the experimental findings with a computational model.
Main Methods:
- Utilizing a custom-built microcapillary Coulter counter with optical access.
- Employing pressure-driven translocation of colloidal particles through capillaries (2-6 µm).
- Measuring changes in current amplitude due to DNA-coated colloids at low salt concentrations (2-40 mmol NaCl).
Main Results:
- Successfully distinguished between 1 µm and 2 µm colloids.
- Demonstrated detection of a few tens of DNA molecules bound to colloidal particles.
- Observed significant differences in current amplitudes between bare and DNA-coated colloids.
Conclusions:
- The microcapillary Coulter counter is effective for detecting surface charges on colloids.
- The technique offers a simple yet sensitive method for analyzing DNA-particle interactions.
- Experimental results align well with a dynamic computer model of particle translocation.
