Cyclic on-chip bacteria separation and preconcentration

Vitaly V Ryzhkov,Igor A Budashov,Mikhail Andronic,Ilya A Rodionov,Ilya N Kurochkin,Alexander V Zverev,Vladimir V Echeistov,Ilya A Ryzhikov,Arkadiy V Eremenko

doi:10.1038/s41598-020-78298-y

Abstract

Nanoparticles and biological molecules high throughput robust separation is of significant interest in many healthcare and nanoscience industrial applications. In this work, we report an on-chip automatic efficient separation and preconcentration method of dissimilar sized particles within a microfluidic platform using integrated membrane valves controlled microfiltration. Micro-sized E. coli bacteria are sorted from nanoparticles and preconcentrated on a microfluidic chip with six integrated pneumatic valves (sub-100 nL dead volume) using hydrophilic PVDF filter with 0.45 μm pore diameter. The proposed on-chip automatic sorting sequence includes a sample filtration, dead volume washout and retentate backflush in reverse flow. We showed that pulse backflush mode and volume control can dramatically increase microparticles sorting and preconcentration efficiency. We demonstrate that at the optimal pulse backflush regime a separation efficiency of E. coli cells up to 81.33% at a separation throughput of 120.45 μL/min can be achieved. A trimmed mode when the backflush volume is twice smaller than the initial sample results in a preconcentration efficiency of E. coli cells up to 121.96% at a throughput of 80.93 μL/min. Finally, we propose a cyclic on-chip preconcentration method which demonstrates E. coli cells preconcentration efficiency of 536% at a throughput of 1.98 μL/min and 294% preconcentration efficiency at a 10.9 μL/min throughput.

Highlights

It means that the bulk of E. coli cells was separated from the filter media during the minimal amount of pulses, which is good, because it allows us to carry out 2.94-fold or 3.49-fold preconcentration with 10.9 or 5.45 μL/min throughput for 4-drop cutoff (3-6 drops) and 2-drop cutoff (5-6 drops)
We operated with 1 mL portions of E. coli suspension in all experiments and carefully studied how such parameters as filtration pressure, backflush volume and pulse backflush regime affect the separation and preconcentration efficiency
The proposed pulse backflush mode allowed us to raise the separation throughput without significantly increasing the filtration pressure, which is important for bacteria viability in applications linked to cell cultures can release factors that influence the proliferation and survival of neighbour cells

Summary

Introduction

It means that the bulk of E. coli cells was separated from the filter media during the minimal amount of pulses, which is good, because it allows us to carry out 2.94-fold or 3.49-fold preconcentration with 10.9 or 5.45 μL/min throughput for 4-drop cutoff (3-6 drops) and 2-drop cutoff (5-6 drops). The proposed method can be significantly improved by reducing the internal volume of the liquid system using a syringe filter with a smaller diameter with more accurate control and sampling. A thin filter membrane can be built into the chip48, which even further lower the internal volume of the microfluidic chip and introduce such highly useful effect as bubble removal.

Results

Conclusion