Substantial Expansion of Detectable Size Range in Ionic Current Sensing through Pores by Using a Microfluidic Bridge...

Area of Science:

• Biophysics
• Nanotechnology
• Analytical Chemistry

Background:

• Ionic current measurements through nano- and micropores are used for biomolecule detection.
• Conventional methods have a limited detectable particle volume (1% of pore volume), restricting analysis of complex mixtures.
• This limitation hinders the application of pore-based sensing to diverse biomolecule samples.

Purpose of the Study:

• To develop a novel methodology for detecting samples with a significantly reduced detectable particle volume (0.01% of pore volume).
• To overcome the limitations of conventional ionic current measurements for analyzing samples with a wide size range of suspended particles.

Main Methods:

• Utilized a microfluidic bridge circuit to measure transient currents generated from potential differences.
• Developed a rational methodology to suppress background ionic current from the microampere (μA) to the picoampere (pA) level.
• Employed a microscale long pore structure (volume: 5.6 × 10^4 aL) for enhanced detection.

Main Results:

• Successfully detected various samples including polystyrene nanoparticles (4 aL), bacteria, cancer cells, and DNA molecules.
• Achieved a substantial suppression of background ionic current, lowering the detectable particle volume limit.
• Demonstrated the capability to detect particles at 0.01% of the pore volume.

Conclusions:

• The proposed method significantly expands the applicability of ionic current sensing systems.
• This technique is suitable for analyzing complex biomolecule samples with a wide range of particle sizes.
• Overcomes previous technological barriers in pore-based sensing for diverse biological samples.