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This paper presents a method to construct and operate a low-cost, multichannel perfusion cell culture system for measuring the dynamics of secretion and absorption rates of solutes in cellular processes. The system can also expose cells to dynamic stimulus profiles.
Certain cell and tissue functions operate within the dynamic time scale of minutes to hours that are poorly resolved by conventional culture systems. This work has developed a low-cost perfusion bioreactor system that allows culture medium to be continuously perfused into a cell culture module and fractionated in a downstream module to measure dynamics on this scale. The system is constructed almost entirely from commercially available parts and can be parallelized to conduct independent experiments in conventional multi-well cell culture plates simultaneously. This video article demonstrates how to assemble the base setup, which requires only a single multichannel syringe pump and a modified fraction collector to perfuse up to six cultures in parallel. Useful variants on the modular design are also presented that allow for controlled stimulation dynamics, such as solute pulses or pharmacokinetic-like profiles. Importantly, as solute signals travel through the system, they are distorted due to solute dispersion. Furthermore, a method for measuring the residence time distributions (RTDs) of the components of the perfusion setup with a tracer using MATLAB is described. RTDs are useful to calculate how solute signals are distorted by the flow in the multi-compartment system. This system is highly robust and reproducible, so basic researchers can easily adopt it without the need for specialized fabrication facilities.
Many important biological processes occur in cell and tissue cultures on the timescale of minutes to hours1,2,3. While some of these phenomena may be observed and recorded in an automated fashion using time-lapse microscopy4, bioluminescence1, or other methods, experiments involving the collection of culture supernatant samples for chemical analysis are often performed manually in static cell cultures. Manual sampling limits the feasibility of certain studies due to the inconvenience of frequent or after-hours sampling timepoints. Further shortcomings of static culture methods include experiments involving controlled, transient exposures to chemical stimuli. In static cultures, stimuli must be added and removed manually, and stimulus profiles are limited to step changes over time, while medium changes also add and remove other medium components, which can affect cells in an uncontrolled manner5. Fluidic systems can overcome these challenges, but existing devices pose other challenges. Microfluidic devices come with the prohibitive costs of specialized equipment and training to produce and use, require microanalytical methods to process samples, and cells are difficult to recover from the devices after perfusion6. Few macrofluidic systems have been created for the types of experiments described here7,8,9,10, and they are built of multiple custom parts made in-house and require multiple pumps or fraction collectors. Furthermore, the authors are not aware of any commercially available macrofluidic perfusion cell culture systems other than stirred tank bioreactors for suspension culture, which are useful for biomanufacturing, though are not designed for modeling and studying physiology.
The authors previously reported on the design of a low-cost perfusion bioreactor system composed almost entirely of commercially available parts11. The base version of the system enables multiple cultures in a well plate to be kept in a CO2 incubator and continuously perfused with medium from a syringe pump, while the effluent medium streams from the cultures are automatically fractionated into samples over time using a fraction collector with a custom modification. Thus, this system enables automated sampling of culture medium supernatant and continuous solute input to the cultures over time. The system is macrofluidic and modular and can be easily modified to meet the needs of novel experiment designs.
The overall goal of the method presented here is to construct, characterize, and use a perfusion cell culture system that enables experiments in which the secretion or absorption rates of substances by cells over time is measured, and/or cells are exposed to precise, transient solute signals. This video article explains how to assemble the base setup, which is capable of perfusing up to six cell cultures simultaneously using a single syringe pump and modified fraction collector. Two useful variants on the base system that make use of additional pumps and parts to allow for experiments that expose cells to transient solute concentration signals, including brief pulses and pharmacokinetic-like profiles12, are also presented, shown in Figure 1.
Figure 1: Three variations on the perfusion system design. (Top) The basic perfusion system. (Middle) The perfusion system with a stopcock for multiple medium sources. (Bottom) The perfusion system with a stirred tank to mimic a well-mixed volume of distribution. Please click here to view a larger version of this figure.
Due to dispersion and diffusion within the flow, the solute signals become distorted or "smeared" as they travel through the flow system. This distortion can be quantified through the use of residence time distributions (RTDs)13. This article explains how to perform tracer experiments on components of the perfusion system (Figure 2), and provides MATLAB scripts to generate RTDs from measured data. A detailed explanation of this analysis can be found in the authors' previous paper11. Additional MATLAB scripts fit appropriate functions to the RTDs and extract physical parameters, and perform signal convolution using RTDs to predict how solute signal input by the user will propagate and distort through the perfusion system14.
Figure 2: Residence time distributions. The RTDs of flow system components, such as this length of tubing, are measured by inputting a pulse of tracer to the system and measuring how it "smears" by the time it exits into the collected fractions. This figure has been modified from Erickson et al.11. Please click here to view a larger version of this figure.
1. Prepare parts for well plate perfusion
2. Laser-cut the multi-head dispenser and attach it to a fraction collector
3. Measure component RTDs and perform signal convolution
4. Set up the basic perfusion system with cells in a well plate
5. Set up the perfusion system with a stopcock for multiple medium sources
6. Set up the perfusion system with a stirred tank to mimic pharmacokinetics
Figure 3: The multi-head dispenser. Design for the laser-cut multi-head dispenser. This figure has been modified from Erickson et al.11. Please click here to view a larger version of this figure.
The perfusion system with multiple medium sources from section 5 of the protocol was used to measure the expression dynamics of a reporter gene driven by the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) transcription factor in human embryonic kidney 293 (HEK293) cells in response to a 1.5 h pulse of tumor necrosis factor alpha (TNF-α). HEK293 cells were stably transduced using lentiviral vectors with a gene construct containing Gaussia luciferase (GLuc), driven by a promoter called NFK...
This work describes the assembly and operation of a perfusion cell culture system with multiple medium sources demonstrated with a specific example in which the dynamics of NF-κB-driven gene expression in response to a transient pulse of TNF-α were measured. The RTDs of the perfusion system components were measured and modeled, and signal convolution was used to predict both the exposure of the cells to the TNF-α pulse and the TNF-α distribution in the collected effluent medium fractions. The cells we...
The authors declare no competing interests.
This research was conducted with support under Grant Nos. R01EB012521, R01EB028782, and T32 GM008339 from the National Institutes of Health.
Name | Company | Catalog Number | Comments |
18 Gauge 1 1/2- in Disposable Probe Needle For Use With Syringes and Dispensing Machines | Grainger | 5FVK2 | |
293T Cells | ATCC | CRL-3216 | HEK 293T cells used in the Representative Results experiment. |
96-Well Clear Bottom Plates, Corning | VWR | 89091-010 | Plates for measuring dye concentrations in RTD experiments and GLuc in representative results experiment. |
BD Disposable Syringes with Luer-Lok Tips, 5 mL | Fisher Scientific | 14-829-45 | |
BioFrac Fraction Collector | Bio-Rad | 7410002 | Fraction collector that can be used for a single stream, or modified using our method to enable collection from multiple streams. |
Clear High-Strength UV-Resistant Acrylic 12" x 12" x 1/8" | McMaster-Carr | 4615T93 | This sheet is cut using a laser cutter according to the DXF file in the supplemental materials to produce the multi-head dispenser that can be attached to the BioFrac fraction collector. |
Coelenterazine native | NanoLight Technology | 303 | Substrate used in Gaussia luciferase bioluminescence assay in representative results. |
Corning Costar TC-Treated Multiple Well Plates, size 48 wells, polystyrene plate, flat bottom wells | Millipore Sigma | CLS3548 | Used to grow and perfuse 293T cells in representative results. |
Corning Costar Flat Bottom Cell Culture Plates, size 12 wells | Fisher Scientific | 720081 | Can be plugged and used as a stirred tank to produce pharmacokinetic profiles in perfusion. Can also contain cells for perfusion. |
DMEM, high glucose | ThermoFisher Scientific | 11965126 | |
Epilog Zing 24 Laser | Cutting Edge Systems | Epilog Zing 24 | Laser cutter used to produce multi-head dispenser from acrylic sheet. Other laser cutters may be used. |
Fisherbrand Sterile Syringes for Single Use, Luer-Lock, 20 mL | Fisher Scientific | 14-955-460 | |
Fisherbrand Sterile Syringes for Single Use, Luer-Lock, 60 mL | Fisher Scientific | 14-955-461 | |
Fisherbrand Premium Microcentrifuge Tubes: 1.5mL | Fisher Scientific | 05-408-129 | Microcentrifuge tubes for collecting fractions. |
Fisherbrand Round Bottom Disposable Borosilicate Glass Tubes with Plain End | Fisher Scientific | 14-961-26 | Glass tubes for collecting fractions. |
Fisherbrand SureOne Micropoint Pipette Tips, Universal Fit, Non-Filtered | Fisher Scientific | 2707410 | 300 ul pipette tips that best fit the multi-head dispenser and tubing to act as dispensing tips. |
Gibco DPBS, powder, no calcium, no magnesium | Fisher Scientific | 21600010 | Phosphate buffered saline. |
Labline 4625 Titer Shaker | Marshall Scientific | Labline 4625 Titer Shaker | Orbital shaker used to keep stirred tanks mixed. |
Masterflex Fitting, Polycarbonate, Four-Way Stopcock, Male Luer Lock, Non-Sterile; 10/PK | Cole-Parmer | EW-30600-04 | Used to join multiple inlet streams for RTD experiments and cell culture experiments. |
Masterflex Fitting, Polycarbonate, Straight, Female Luer x Cap; 25/PK | Masterflex | UX-45501-28 | |
Masterflex Fitting, Polypropylene, Straight, Female Luer to Hosebarb Adapters, 1/16" | Cole-Parmer | EW-45508-00 | |
Masterflex Fitting, Polypropylene, Straight, Male Luer Lock to Hosebarb Adapter, 1/16" ID | Cole-Parmer | EW-45518-00 | |
Masterflex Fitting, Polypropylene, Straight, Male Luer Lock to Plug Adapter; 25/PK | Masterflex | EW-30800-30 | |
Masterflex L/S Precision Pump Tubing, Platinum-Cured Silicone, L/S 14; 25 ft | Masterflex | EW-96410-14 | |
MATLAB | MathWorks | R2019b | Version R2019b. Newer versions may also be used. Some older versions may work. |
NE-1600 Six Channel Programmable Syringe Pump | New Era Pump Systems | NE-1600 | |
Rack Set F1 | Bio-Rad | 7410010 | Racks to hold collecting tubes in the fraction collector. |
Recombinant Human TNF-alpha (HEK293-expressed) Protein, CF | Bio-Techne | 10291-TA-020 | Cytokine used to stimulate 293T cells in representative results. |
Saint Gobain Solid Stoppers, Versilic Silicone, Size: 00, Bottom 10.5mm | Saint Gobain | DX263015-50 | Fits 48-well plates. |
Saint Gobain Solid Stoppers, Versilic Silicone, Size: 4 Bottom 21mm | Saint Gobain | DX263027-10 | Fits 12-well plates. |
Sodium Hydroxide, 10.0 N Aqueous Solution APHA; 1 L | Spectrum Chemicals | S-395-1LT | |
SolidWorks | Dassault Systems | SolidWorks | CAD software used to create the multi-head dispenser DXF file. |
Varioskan LUX multimode microplate reader | ThermoFisher Scientific | VL0000D0 | Plate reader. |
Wilton Color Right Performance Color System Base Refill, Blue | Michaels | 10404779 | Blue food dye containing Brilliant Blue FCF, used as a tracer in RTD experiments. Absorbance spectrum peaks at 628 nm. |
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