Abstract
Functional imaging has been a widely established method for the assessment of ion channel function in vitro. Conventional infrastructure used for in vitro functional analysis of ion channels is typically proprietary, non-customizable, expensive, and requires a high level of skill to use and maintain. 3D desktop printing, which is employed in the rapid prototyping field, allows for quick engineering of alternatives to conventional imaging infrastructure that are customizable, low cost, and user friendly. Here, we describe an ultra-low-cost microfluidic lab-on-a-chip (LOC) device manufactured using acrylonitrile butadiene styrene (ABS) for in vitro functional imaging of ion channels that can quickly and easily be reconstructed using three-dimensional (3D) desktop printing. The device is light weight (<5 g), small (20 mm × 49 mm), and extremely low cost (<EUR 1). We simulate fluidics within the printed channels and assess the suitability of the engineered chamber to generate homogeneous mixtures during solution exchange. We demonstrate the usability of the 3D printed microfluidic device in a case study using Fluo-4-loaded human embryonal kidney-derived (HEK293) cells, recombinantly expressing the capsaicin receptor, transient receptor potential vanilloid receptor type 1 (TRPV1), as a model system. In the case study, we confirm its applicability to solution exchange for chemical stimulation and parallel functional time-lapse fluorescence microscopy-based calcium imaging. We assess the suitability of ABS for culturing HEK293 cells inside the microfluidic LOC, based on qualitative analysis of microscopic transmission light images of ABS-exposed HEK293 cells and confirm the previously reported biocompatibility of ABS. To highlight the versatility of the 3D printed microfluidic device, we provide an example for multiplication of the shown concept within a 3D printed multichannel microfluidic LOC to be used, for example, in a higher throughput format for parallelized functional analysis of ion channels. While this work focusses on Ca2+ imaging with TRPV1 channels, the device may also be useful for application with other ion channel types and in vitro models.
Highlights
Ion channels are involved in a variety of key cellular functions and are considered very attractive targets for therapeutic intervention [1,2,3,4]
Available systems for solution exchange are characterized by high speed and high precision liquid handling
There are examples of cost-effective devices, for example, polydimethylsiloxane (PDMS)- or alginate-based microfluidic systems [14,15,16,17,18,19] which allow for automated liquid handling, as well as three-dimensional (3D) printed chambers for maintenance and microscopic observation of cultured cells [20,21], a platform for chemical stimulation and parallel analysis of ion channel function that is reproducible within a short time, scalable to higher throughput screening mode and at the same time an ultra-low-cost device, has not yet been reported
Summary
Ion channels are involved in a variety of key cellular functions and are considered very attractive targets for therapeutic intervention [1,2,3,4]. To overcome the aforementioned limitations of commercially available technology for functional analysis of ion channels, we aimed to develop a microfluidic platform based on a DIY approach that is reproducible and, at the same time, affordable to a broad range of research labs. To this end, we intended to employ 3D desktop printing and acrylonitrile butadiene styrene (ABS), a biocompatible thermoplastic, for additive manufacturing. To show that the described technology is scalable and customizable, we aimed to provide an example of a 3D printed multichannel microfluidic LOC to be used, for example, in higher throughput format for parallelized functional analysis of ion channels
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