Construction and characterisation of a modular microfluidic system: coupling magnetic capture and electrochemical detection

Abstract

This work presents the fabrication and characterisation of a versatile lab-on-a-chip system that combines magnetic capture and electrochemical detection. The system comprises a silicon chip featuring a series of microband electrodes, a PDMS gasket that incorporates the microfluidic channels, and a polycarbonate base where 5 permanent magnets are hosted; these parts are designed to fit so that wire bonding and encapsulation are avoided.This system can perform bioassays over the surface of magnetic beads and uses only 50 µL of bead suspension per assay. Following detection, captured beads are released simply by sliding a thin iron plate between the magnets and the chip. 10 Particles are captured upstream from the detector and we demonstrate how to take further advantage of the system fluidics to determine enzyme activities or concentrations, as flow velocity can be adjusted to the rate of the reactions under study. We used magnetic particles containing β-galactosidase and monitored the enzyme activity amperometrically by the oxidation of 4-aminophenol enzymatically 15 produced from 4-aminophenyl-β-D-galactopyraniside. The system is able to detect presence of enzyme down to approximately 50 ng mL -1 . 20

Improved bacteria detection by coupling magneto-immunocapture and amperometry at flow-channel microband electrodes

“…The study of peaks generated as a result of enzyme product accumulation during the transition between flow rates reportedly provided increased sensitivity for ␤-galactosidase detection (Godino et al, 2010). In the HRP-HQ system, however, wider peaks and lower initial currents (t = 0) were registered for the highest concentrations of HRP tested, which indicated that part of the BQ produced diffused towards the electrodes during the incubation step.…”

“…MPs are then analysed using a flow cell ( Fig. 1), which encloses an incubation microchamber, a microfluidic channel, and a silicon chip containing a set of electrodes (Godino et al, 2010). While MPs are magnetically retained in the microchamber, the enzyme product flows and is chronoamperometrically detected at the gold microband electrode located downstream.…”

Dual chronoamperometric detection of enzymatic biomarkers using magnetic beads and a low-cost flow cell

“…Four permanent magnets (S-04-02-N supermagnete, DE) were located in the holder base, which allows the confinement of MBs inside the microchannels, but upstream from the reference and working electrodes. Following electrochemical detection, the beads were released by blocking the magnetic field using a soft iron slab (Laczka et al, 2011b;Godino et al, 2009). The holder cover contains both the fluidic connections (male mini luer plugs, Ref.…”

“…The flow cell consists of a microfluidic cartridge made of a series of cyclo-olefin polymer (COP) and pressure sensitive adhesive (PSA) layers, featuring four independent channels and their corresponding sets of gold microband electrodes. The cartridge is inserted into a holder that provides microfluidic and electrical connections, and presents a row of switchable magnets (Godino et al, 2009). Except for the microelectrodes, which are microfabricated in the clean room (ICTS-IMB-CNM), the system has been produced using rapid prototyping techniques outside a clean room environment.…”

Flow-Enhanced Nonlinear Magnetophoresis for High-Resolution Bioseparation

“…Superparamagnetic beads have proven to be well suited for lab-on-a-chip separation of rare cell types 7,8 and highly sensitive bioanalytical measurements [9][10][11][12][13] . Current limitation of this technique are that separation is limited to a small number of analytes and can lead to aggregation of the magnetic beads on the cells, which complicates the recovery of viable rare cell types.…”