Macro-to-micro interfacing to microfluidic channels using 3D-printed templates: application to time-resolved secretion sampling of endocrine tissue

Abstract

Employing 3D-printed templates for macro-to-micro interfacing, a passively operated polydimethysiloxane (PDMS) microfluidic device was designed for time-resolved secretion sampling from primary murine islets and epidiymal white adipose tissue explants. Interfacing in similar devices is typically accomplished through manually punched or drilled fluidic reservoirs. We previously introduced the concept of using hand fabricated polymer inserts to template cell culture and sampling reservoirs into PDMS devices, allowing rapid stimulation and sampling of endocrine tissue. However, fabrication of the fluidic reservoirs was time consuming, tedious, and was prone to errors during device curing. Here, we have implemented computer-aided design and 3D printing to circumvent these fabrication obstacles. In addition to rapid prototyping and design iteration advantages, the ability to match these 3D-printed interface templates with channel patterns is highly beneficial. By digitizing the template fabrication process, more robust components can be produced with reduced fabrication variability. Herein, 3D-printed templates were used for sculpting millimetre-scale reservoirs into the above-channel, bulk PDMS in passively-operated, eight-channel devices designed for time-resolved secretion sampling of murine tissue. Devices were proven functional by temporally assaying glucose-stimulated insulin secretion from <10 pancreatic islets and glycerol secretion from 2-mm adipose tissue explants, suggesting that 3D-printed interface templates could be applicable to a variety of cells and tissue types. More generally, this work validates desktop 3D printers as versatile interfacing tools in microfluidic laboratories.

Automated Microfluidic Droplet-Based Sample Chopper for Detection of Small Fluorescence Differences Using Lock-In Analysis

“…Such information should contribute to gaining a better understanding of factors that lead to obesity 29–33 and type 2 diabetes. 34,35 Although our prior studies of adipose tissue on microdevices were quantitative in nature, 19,36–38 single cell resolution was not achieved.…”

3D-templated, fully automated microfluidic input/output multiplexer for endocrine tissue culture and secretion sampling

“…Two layer, valved microfluidic devices (Figure 1) were fabricated using standard multilayer soft lithography methods 32–34 with 3D-printed templating 11, 22 . Detailed procedures are described in ESI.…”

“…This potential is exemplified by the recent outpouring of organs-on-chips that nicely simulate physiology at the tissue level or even the organ level; such devices recapitulate biological functions in a manner unmatched by standard culture methods 8 . Our group 9–11 and others 12–21 have shown the utility of microsystems to study biological function of pancreatic islets, and we have begun applying these systems to studying primary adipose tissue function 11, 22 . Although some studies have leveraged microfluidics to assay secretion from adipocyte cell lines 23–25 , less has been accomplished toward studying dynamics of intact, primary adipose tissue on-chip 26 .…”

“…Although some studies have leveraged microfluidics to assay secretion from adipocyte cell lines 23–25 , less has been accomplished toward studying dynamics of intact, primary adipose tissue on-chip 26 . In terms of fluid handling, although passively controlled microdevices provide simplicity of use 10, 11, 22, 27 , the precision in fluidic control provided by actively valved devices is virtually unmatched in gleaning complex functions from biological systems 28–31 . As such, a precisely valved, customized microdevice should be a fitting analytical solution to help decipher endocrine tissue dynamics.…”

“…This system essentially serves as a mimic of the circulatory system and of upstream endocrine signals. The device is automated through feedback sensing of solution levels, and 3D-printed templates 11 are used to interface both islets and adipose tissue. High device flexibility is shown by varying from multiple fluidic outputs to primarily inputs, by operation in sampling and imaging modes, and by studying multiple murine tissues.…”