Development of a programmable magnetic agitation device to maintain colloidal suspension of cells during microfluidic syringe pump perfusion

PLOS ONE RESEARCH ARTICLE Development of a programmable magnetic agitation device to maintain colloidal suspension of cells during microfluidic syringe pump perfusion Tommy Puttrich1☯, Steven O’Donnell1☯, Sing-Wan Wong1,2, Miiri Kotche1, Anthony E. Felder1*, Jae-Won Shin ID1,2* a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 1 The Richard and Loan Hill Department of Biomedical Engineering, University of Illinois at Chicago, Chicago, Illinois, United States of America, 2 Department of Pharmacology and Regenerative Medicine, University of Illinois at Chicago, Chicago, Illinois, United States of America ☯ These authors contributed equally to this work. * (JWS); (AEF) Abstract OPEN ACCESS Citation: Puttrich T, O’Donnell S, Wong S-W, Kotche M, Felder AE, Shin J-W (2023) Development of a programmable magnetic agitation device to maintain colloidal suspension of cells during microfluidic syringe pump perfusion. PLoS ONE 18(3): e0282563. https://doi.org/ 10.1371/journal.pone.0282563 Editor: Jeffrey Chalmers, The Ohio State University, UNITED STATES Droplet-based microfluidic devices have been used to achieve homogeneous cell encapsulation, but cells sediment in a solution, leading to heterogeneous products. In this technical note, we describe automated and programmable agitation device to maintain colloidal suspensions of cells. We demonstrate that the agitation device can be interfaced with a syringe pump for microfluidic applications. Agitation profiles of the device were predictable and corresponded to device settings. The device maintains the concentration of cells in an alginate solution over time without implicating cell viability. This device replaces manual agitation, and hence is suitable for applications that require slow perfusion for a longer period of time in a scalable manner. Received: September 16, 2022 Accepted: February 20, 2023 Published: March 8, 2023 Copyright: © 2023 Puttrich et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the paper and its Supporting information files. Funding: This work was supported by federal grants, including National Institutes of Health Grants R01-GM141147 and R01-HL141255, and National Science Foundation CAREER Grant 2143857 (J.-W.S.). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Introduction Tissue engineering is a multidisciplinary area of research applying principles of biomaterial design and medicine to generate tissues and organs that better replicate their original functions and structures [1–5]. One technique used in tissue regeneration is the microscale encapsulation of single cells in a hydrogel for precision niche modeling and delivery via the use of droplet-based microfluidic devices [6–9]. To encapsulate cells, a colloid must be prepared consisting of the living cells and the aqueous phase of the material the cells will be encapsulated within. This colloid must be slowly perfused through a microfluidic device to create small capsules of cells in a monodisperse manner [10]. However, due to the high density of the cells, they sediment from the colloid over time. Current methods to resuspend cells involve manual agitation using a small stir bar placed within the colloid, which is then manipulated externally using a neodymium magnet. Although effective at preventing premature cell aggregation, the task is manual, time-intensive, and may produce inconsistent homogeneity. To address this shortcoming, different types of PLOS ONE | https://doi.org/10.1371/journal.pone.0282563 March 8, 2023 1 / 10 PLOS ONE Competing interests: The authors have declared that no competing interests exist. A programmable agitation device to maintain colloidal suspensions of cells automated stirring devices have been developed. In dispersive liquid–liquid microextraction applications, a rotating magnetic stir bar is used to induce a vortex in the syringe solution [11, 12], although this approach has not been demonstrated with live cell culturing. Lack of translation of the magnetic stir bar longitudinally along the syringe is an additional shortcoming. The commercially available Cetoni NemixTM system agitates a syringe solution by both translating and rotating a magnetic stir bar along the syringe axis [13]. However, this system is proprietary and integrated, which precludes use with additional third-party equipment and software. Another commercially available solution from GPD Global utilizes a screw drive to agitate a syringe solution [14]. This technique is intended for industrial manufacturing purposes with higher volumes and has also not been demonstrated with live cell culturing applications. Here, we design, fabricate, and evaluate an automated agitation device to maintain colloidal suspension of cells during syringe pump perfusion. This device is low-cost, modular, and adjustable to accommodate existing syringe pumps. Materials and methods Design of the programmable agitation device The programmable agitation device was designed in Solidworks (version 2021, Dassault Systèmes) and 3D printed in polylactic acid using a fused deposition modeling printer (Ender 3 Pro, Creality). The device is modular and adjustable to accommodate horizontally-oriented syringe pumps commonly used in scientific research labs. As shown in Fig 1, the device is elevated using telescoping legs to accommodate a syringe pump (Harvard 33, Harvard Apparatus). The operational principle of the device is to linearly translate an external magnet along the length of a syringe barrel, which in turn translates a micro stir bar placed in the syringe. Motion of the micro stir bar agitates the fluid within the syringe and maintains suspension. Neodymium magnets (N35, 10x5x3 mm) external to the syringe barrel are mounted to the lead screw assembly (Fig 1, component b) via independent vertically-adjustable hooked attachments (Fig 1, component a). The hooked attachments and external magnets are oriented to straddle the syringe barrel (Fig 1, component g). The external magnets define longitudinal positioning of the magnetic stir bar (Fig 1, component j, 2x5 mm, No. 58948–377, VWR) within the syringe. Linear translation of the lead screw assembly is provided via rotation of the lead screw (Fig 1, component c, 400 mm length, 8 mm diameter, 2 mm pitch, Uxcell). Rotation of the lead screw is provided by a brushed motor (200 RPM 12 VDC, Uxcell) with a flexible coupler joint located within a controller housing (Fig 1, component e). Rotation of the DC motor is controlled by a programmable microcontroller (Arduino Uno) and DC motor controller (DROK L298). A customized control software was written for the microcontroller using the Ardui (...truncated)