Welcome To Cell Analysis Ltd

CELL-DEP is an easy to use system that will allow the user to exploit the phenomenon of dielectrophoresis in varied applications involving biological particles including cells and viruses. Unlike electrophoresis, in which the net intrinsic electrical charge on the particle influences the movement in an electrical field, movement in a dielectric field is determined by the magnitude and polarity of the charges induced in a particle by the applied field. Technically one of the main differences is that dielectrophoresis requires an alternating current (AC) with a wide range of frequencies.

The types of biological particles that can be collected and separated by dielectrophoresis

Including bacteria, fungi, protozoa, mammalian cells in addition to sub-micron particles such as viruses and bacteriophage. Dielectrophoresis systems often include microelectrodes arranged within containment chambers. The electrodes are manufactured using photolithographic techniques developed for the microelectronics industry. This allows the design and construction of electrode structures with µm proportions. These small dimensions are required in order to generate the high field strengths necessary to influence the movement of cells.

The System

CELL-DEP is an embedded computer platform and peripheral hardware that is designed to exploit the phenomenon of dielectrophoresis as a technique for collecting and concentrating biological particles of interest within a microelectrode structure. Combined with electronic impedance measurement, dielectrophoretic collection of biological particles can be quickly monitored and quantified.

The system is centred on an integrated controller unit which can interface with:

	micro-electrodes either single or in an array
	peristaltic pumps
	micro-fluidic valves
	microscope based imaging systems

System management within the computer platform is based on Intel Pentium IV processor technology combined with programmable modular software to control internal and external hardware including:

arbitrary waveform generator

data acquisition module

opto-digital isolators

peristaltic pumps

solenoid pinch valves

System controller and software allows the user to control and customise all aspects of their experimental protocols. This includes:

semi-automated control of sample flow through the electrode chamber by interfacing with high precision peristaltic pump(s) with up to 12 fluidic channels per pump and electronically activated solenoid pinch valves to modify or combine fluid flow

Frequency and voltage of the waveform generation to allow optimisation of biological particle collection by dielectrophoresis

acquisition of permittivity and conductivity data for impedance measurement

Transfer and storage of data into spreadsheets

Electrodes

At the heart of the system is the electrode embedded within a micro-fluidic chamber to allow simple connection to the computer platform for electronic signalling and measurement and to the peristaltic pump for fluidic movement. The electrodes are manufactured by standard photolithography process on a variety of substrates including glass, polycarbonate or silicon. The electrodes can be deposited in either gold or aluminium and with a variety of electrode gap widths to suite the size of the cell type to be collected. Various designs are available including a simple two bar electrode for impedance measurement, multi-bar electrode column arrays for collection of large number of cells or combination electrodes for dielectrophoretic collection of particles and impedance measurement. More than one electrode can be connected and operated simultaneously.

Examples of Electrodes

This picture shows an array of eight column electrodes with accompanying two-bar impendence electrode. It is a gold/titanium electrodes on glass.

	This picture shows a similar electrode array constructed with a glass lid in place containing holes for microfluidic port connections. The channel walls in this example are made form polyamide.
This picture shows how the complex electrode array can be mounted into the electrode carrier for secure microfluidic and electronic connections.

System Controller Software (Piero)

The system controller and its software have the capacity to collect impedance measurements from up to 12 electrodes in a single cycle. The system controller software is simple and intuitive to use without the user requiring any knowledge of programming. The software is broken down into a series of modules each of which controls the functions of one electronic or fluidic component that make up the system. These are the arbitrary function wave generator, the data acquisition interface, optical relay systems, external pumps and any solenoid pinch valves incorporated into the fluidic system.

Piero is a modular object-orientated controlling software that allows the user, through a powerful scripting tool, to command all components of the system. Modules control all parameters of the arbitrary function waveform generator, pump speeds, and timing, and data acquisition. No prior knowledge of protocols is required. Complex programming scripts can be written to allow automatic processing of samples and data collection. Examples of the functions that can be scripted include sample recycling for spectral analysis, variable fluid flow rates, chamber flushing and cell collection and release. Choice of operating systems is available- Windows 2000 / NT4 / XP.

An example of a Piero window is shown below.

The upper left hand window contains a list of previously constructed and saved scripts. These can be recalled for future applications allowing consistent software and hardware management between experiments. The main script dialogue box is shown in the upper right hand window. Here, each hardware component is given a different colour code to ease identification during script construction. Descriptive lines can be inserted into the script to allow non-familiar users a detailed explanation of what each line in the script is doing. The resources window provides a list of the hardware components built into the system.