Abstract
Microfluidics is becoming a technology of growing interest for building microphysiological systems with integrated read-out functionalities. Here we present the integration of enzyme-based multi-analyte biosensors into a multi-tissue culture platform for ‘body-on-a-chip’ applications. The microfluidic platform is based on the technology of hanging-drop networks, which is designed for the formation, cultivation, and analysis of fluidically interconnected organotypic spherical three-dimensional (3D) microtissues of multiple cell types. The sensor modules were designed as small glass plug-ins featuring four platinum working electrodes, a platinum counter electrode, and an Ag/AgCl reference electrode. They were placed directly into the ceiling substrate from which the hanging drops that host the spheroid cultures are suspended. The electrodes were functionalized with oxidase enzymes to enable continuous monitoring of lactate and glucose through amperometry. The biosensors featured high sensitivities of 322±41 nA mM−1 mm−2 for glucose and 443±37 nA mM−1 mm−2 for lactate; the corresponding limits of detection were below 10 μM. The proposed technology enabled tissue-size-dependent, real-time detection of lactate secretion from single human colon cancer microtissues cultured in the hanging drops. Furthermore, glucose consumption and lactate secretion were monitored in parallel, and the impact of different culture conditions on the metabolism of cancer microtissues was recorded in real-time.
Highlights
Microsystems technology offers a variety of new approaches to culturing and analyzing human cells and functional tissue structures[1,2]
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]
We demonstrated the detection of lactate secreted by single-microtissue spheroids, the amount of which depends on the tissue size
Summary
Microsystems technology offers a variety of new approaches to culturing and analyzing human cells and functional tissue structures[1,2]. Microsensor technologies have been developed over the past several decades for a variety of applications Their miniature size and versatile features as well as their high sensitivity and low-detection limits enable monitoring of various analytes in cell and tissue culture set-ups at high temporal and spatial resolution. 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]. A sputtering process was networks consist of arrays of interconnected hanging drops that are designed for 3D microtissue aggregation and culture[56] They allow precise control of microtissue culture conditions and enable on-chip intertissue communication, which is of fundamental importance for realizing 3D microtissue bodyon-a-chip configurations. The individual glass plug-ins were glued onto a printed circuit board (PCB, 8 mm × 91 mm × 1.5 mm), wire bonded and packaged
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