Continuous-flow multi-analyte biosensor cartridge with controllable linear response range

Abstract

This article presents the design and fabrication of a microfluidic biosensor cartridge for the continuous and simultaneous measurement of biologically relevant analytes in a sample solution. The biosensor principle is based on the amperometric detection of hydrogen peroxide using enzyme-modified electrodes. The low-integrated and disposable cartridge is fabricated in PDMS and SU-8 by rapid prototyping. The device is designed in such a way that it addresses two major challenges of biosensors using microfluidics approaches. Firstly, the enzymatic membrane is deposited on top of the platinum electrodes via a microfluidic deposition channel from outside the cartridge. This decouples the membrane deposition from the cartridge fabrication and enables the user to decide when and with what mixture he wants to modify the electrode. Secondly, by using laminar sheath-flow of the sample and a buffer solution, a dynamic diffusion layer is created. The analyte has to diffuse through the buffer solution layer before it can reach the immobilized enzyme membrane on the electrode. Controlling of the thickness of the diffusion layer by variation of the flow-rate of the two layers enables the user to adjust the sensitivity and the linear region of the sensor. The point where the buffer and sample stream join proved critical in creating the laminar sheath-flow. Results of computational simulations considering fluid dynamics and diffusion are presented. The consistency of the device was investigated through detection of glucose and lactate and are in accordance with the CFD simulations. A sensitivity of 157+/-28 nA/mM for the glucose sensor and 79+/-12 nA/mM for the lactate sensor was obtained. The linear response range of these biosensors could be increased from initially 2 mM up to 15 mM with a limit of detection of 0.2 mM.

Multi-analyte biosensor interface for real-time monitoring of 3D microtissue spheroids in hanging-drop networks

“…The catalase membrane solution contained 1 mg catalase (Sigma-Aldrich), 30 mg BSA, 500 μl DI water, 10 μl Triton X-100 (3 g l − 1 ), and 20 μl GA. GA was added at the end, after all other compounds had been thoroughly mixed for 15 min. The final solution was mixed for an additional 5 min using a magnetic stirrer 48 . Sub-microlitre volumes of these solutions were manually transferred onto the electrodes by touching the small rim structure surrounding the electrodes with a 2-μl pipette using appropriate tips.…”

“…Miniaturized versions have been used as scanning probes to monitor the glucose and lactate metabolism of single cells 42,43 . Flow-through-type sensor systems have been devised to analyze cell culture conditions and metabolites in liquid samples downstream of cell cultures [44][45][46][47][48][49][50][51] . Silicon-based sensor chips for multi-parameter online monitoring have been mounted in a perfused cell culture unit 52 , and multiple sensing electrodes have been directly incorporated into transparent microfluidic systems to measure the glucose consumption of single cardiac cells 53 or the lactate production of cells of various types 54 and, combined with optical read-out, for monitoring cancer cell metabolism 55 .…”

Microfluidic enzymatic biosensing systems: A review

“…In this case, equal splitting of the stream of solution is of great importance since the flow rate can have significant influence on the measurement (Hashimoto et al, 2006;Lamberti et al, 2012). Alternatively, multiple electrodes can be placed in the same channel (Frey et al, 2010;Parra-Cabrera et al, 2012). In order to avoid cross-talk, the electrodes can be placed parallel to each other along the direction of flow and functionalized individually (Fig.…”

“…Since flow in microfluidic channels is laminar (Whitesides, 2006), products of the enzymatic reactions are transported away from the electrodes without influencing the other measurements. In order to selectively functionalize the electrodes, systems with a dedicated functionalization channel for each electrode (Frey et al, 2010) and those utilizing laminar co-flow have been proposed (Parra-Cabrera et al, 2012). While these approaches obviate the problem of different flow rates in the channels, they complicate the microfluidic design.…”

Staggered-electromagnetophoresis with a Split-flow System for the Separation of Microparticles by a Hollow Fiber-embedded PDMS Microchip

“…[1][2] Moreover, it should be also possible to increase the sensitivity, shorten the analytical time and miniaturize the device. This approach is effective not only for liquid-liquid extraction and reaction of sample molecules as a typical microchip analysis, but also for the separation and characterization of microparticles, such as biological cells, inorganic and polymer particles, which have gained increasing importance in many research fields, including for industrial, biological, medical, and environmental applications.…”