Developing an Experimental Automated Bioreactor for 2D Endothelial Structures

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"NI LabVIEW with NI LabVIEW FPGA Module and NI PCI-7831R provides excellent platform for creating modular experimental bioreactor for dynamic endothelial cell cultivation."

- Roman Matejka, Faculty of Biomedical Engineering, Czech Technical University in Prague

The Challenge:
Developing a modular, dynamic bioreactor to ensure stable physiological conditions during the cultivation of endothelial cells in a planar 2D structure and enable further experiments in 3D structures, especially for artificial arterial prosthesis development.

The Solution:
By basing the system on the NI FPGA hardware platform and NI LabVIEW system design software, we developed a modular system for dynamic cultivation that ensures stable physiological conditions for long-term experiments. The flexible structure allows us to modify the system based on the needs of specified cultivation experiments. The measured results from the 2D cultivation experiments help us establish new tests with the cultivation of artificial arterial prosthesis.

Author(s):
Roman Matejka - Faculty of Biomedical Engineering, Czech Technical University in Prague
Jozef Rosina - Faculty of Biomedical Engineering, Czech Technical University in Prague; Faculty of Medicine, Charles University in Prague
Jana Stepanovska - Faculty of Biomedical Engineering, Czech Technical University in Prague
Elena Filova - Institute of Physiology, Czech Academy of Sciences of Czech Republic
Jana Havlikova - Institute of Physiology, Czech Academy of Sciences of Czech Republic
Jaroslav Chlupac - Institute of Physiology, Czech Academy of Sciences of Czech Republic

Atherosclerosis is a disease in which an artery wall thickens due to the accumulation of fatty materials. In the worst cases, it may lead to a complete obstruction of the artery. It causes nearly half of all deaths in Europe. The obstructed part of the artery may be surgically replaced or bypassed by a vascular prosthesis made of an artificial material or by a patent’s autologous graft. The best results can be achieved by autologous grafts, but there is problem with obtaining them, especially for calibers less than 6 mm.

An artificial vascular prosthesis should mimic the native artery without causing an undesirable biological response. The frame for the prosthesis (scaffold) is a mechanical tubular structure, which must withstand repeated cycles of blood pulses for many years. Lining the luminal graft surface of artificial vascular prostheses with a confluent, phenotypically mature endothelial cell layer is a prerequisite for its long-term patency. This can be best achieved by a procedure that involves harvesting autologous endothelial cells, which is the thin layer of cells that lines the interior surface of blood vessels and lymphatic vessels, prior to a planned surgery, and then expanding the cells in cell culture conditions. The process of covering the vascular graft surface with mature endothelium was typically performed under static conditions, but the best results can be achieved if it is done under the conditions of laminar flow of the culture medium and shear stress similar to physiological values in the organism. To ensure these conditions, it is necessary to control and monitor the whole cultivation process and create standardized schemes for endothelium cultivation. These conditions can be achieved in active bioreactors to maintain these conditions.

Figure 1.Comparison of static and dynamic cultivation of human saphenous vein endothelial cells cells on different surfaces. The dynamic conditions provide for better development of cytoskeleton, which is important to the endothelial layer.

Construction of an Automated Experimental Bioreactor

The designed bioreactor consists of several parts—cultivation chambers, fluidics, and monitoring and control system software. This system needs to be stable to ensure physiological conditions for long-term experiments up to four to five weeks. The PCI-7831R installed in IPC (Industrial PC) was used as main platform. This card has many universal I/O lines, combined with analog I/Os provides an excellent platform to create modular system. Process monitoring transducers like a temperature, flow, pressure, electrochemical parameters are conditioned and using difference line driver connected directly to analog inputs. Main peristaltic pumps are controlled over analog outputs and some digital lines. Maximum stability and safety is maintained by redundant power supply (UPS and diesel generator).

Figure 2. Cultivation chambers and fluidics part installed into CO2 thermal box, peristaltic pump, IPC with NI PCI-7831R card and signal conditioning circuits for transducers.

Bioreactor Software

Special software was made to monitor and control the process of cultivation. This software was developed using LabVIEW (with NI LabVIEW FPGA Module and NI Vision Acquisition Software). Critical code, like a regulation of pump based on measured flow and safety routines are implemented into FPGA target. This provides excellent stability and further extensibility. Rest of code, such a main GUI, data logging, is running directly on IPC. Also web access is implemented to provide remote inspection/control over the long term experiments. Apart from main controlling software also bunch of analysis tools was created. These tools were used to analyze image data during and after experiments from optical, fluorescence and confocal microscopy.

Figure 3. Software for controlling bioreactor and image analysis.

Further Plans

Based on experimental results from 2D endothelium experiments we are starting to cultivate 3D tubular structures that will form into biocompatible artificial arterial prostheses. This structure will consist of tubular scaffold that will be seeded with endothelium and smooth muscle cells. Designed bioreactor is able to ensure stable conditions to such a complex experiments. According to modular construction there is easy way to modify or extend system based on need of experiments. Also there is plan to integrate system into embedded target such as NI Single-Board RIO to create stand-alone fully controlled bioreactor.

Author Information:
Roman Matejka
Faculty of Biomedical Engineering, Czech Technical University in Prague
Sitna sq. 3105
Kladno 272 01
Czech Republic
roman.matejka@fbmi.cvut.cz

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