A linear concentration gradient generator based on multi-layered centrifugal microfluidics and its application in antimicrobial susceptibility testing

Abstract

In almost any branch of chemistry or life sciences, it is often necessary to study the interaction between different components in a system by varying their respective concentrations in a systematic manner. Currently, many procedures for generating a series of samples of different solute concentration levels are still done manually by dilution. To address this issue, we present herein a highly automated linear concentration gradient generator based on centrifugal microfluidics. The operation of this device is based on the use of multi-layered microfluidics in which individual fluidic samples to be mixed together are stored and metered in their respective layers before finally being transferred to a mixing chamber. To demonstrate the operation of this scheme, we have used the device to conduct antimicrobial susceptibility testing (AST). Firstly, DI water, ampicillin solution and E. coli suspension were loaded into the chambers in different layers. As the device went through several rounds of spinning at different speeds, a series of metered dosages of ampicillin along a linear concentration gradient were introduced to the mixing chamber and mixed with E. coli automatically. By monitoring the spectral absorbance of the suspensions, we were able to establish the minimum inhibitory concentration (MIC) value of ampicillin against E. coli. The process took about 3 hours to complete, and the experimental results showed a strong correlation with those obtained with the standard CLSI broth dilution method. Clearly, the platform is useful for a wide range of applications such as drug discovery and personalised medicine, where concentration gradients are of concern.

Micro- and Nanoscale Approaches in Antifungal Drug Discovery

“…An automated linear gradient generator based on centrifugal microfluidics. [148] E. coli, Nitrosomas europaea Optical imaging of single cell growth (number of cells).…”

3D microfluidic gradient generator for combination antimicrobial susceptibility testing

“…Various microfluidic-based AST platforms 23,31 have demonstrated miniaturized and multiplexed fluid handing 32,33 to increase the throughput of AST analysis 29,34,35 and decrease the mortality rate and healthcare costs 36,37 associated with treating clinical AMR-related infections 38,39 , for novel drug development 40,41 , and for pointof-care clinical dosage recommendations [42][43][44][45] . Microfluidic concentration gradient generators (µ-CGGs), the most widely adopted class of microfluidic AST technologies 46 for MIC and CDS studies, employ branching microchannel networks comprised of nodal units to produce diluted concentrations representing a gradient between input species.…”

A Microfluidic Concentration Gradient Maker with Tunable Concentration Profiles by Changing Feed Flow Rate Ratios

“…Generally speaking, a linear concentration gradient generator can be easily set up by classic Christmas-tree microfluidic channel networks [8], convection-driven flow [18], or novel designs such as centrifugal microfluidics [19][20][21] or 3D-printing stereo networks [22]. To address a nonlinear concentration gradient profile, a range of different microfluidic mixing technologies have been developed.…”