Design and Development of an Automated System for Isolating Rare Cells Using LabVIEW

Challenge: Design, develop, and manufacture a tool that can detect and isolate circulating tumor cells (CTCs) or fetal cells in maternal blood for personalized therapy in oncology or non-invasive prenatal diagnosis.

Solution: Developed a patented technology called "lab-on-a-chip" that uses the microelectronic properties of active silicon substrates to create miniature biological laboratories that can operate suspended cells individually with the help of NI embedded controllers.

Silicon Biosystems' technology is based on the ability of electric fields to exert forces on neutral polarizable particles (such as cells) suspended in a liquid. According to this electrokinetic principle, called dielectrophoresis (DEP), neutral particles in an inhomogeneous electric field experience a force with the electric field strength increasing in a spatial direction (positive) dielectrophoresis (pDEP) or decreasing (negative) dielectrophoresis (nDEP). More specifically, the particle experiences either a positive or negative dielectrophoretic force due to its own electrical properties, which depend on the frequency and the properties of the medium in which the particle is suspended (Figure 1).

Figure 1. Cell capture by dielectric cages

In the DEPArray system, an electric field is generated on the surface of a silicon chip (Figure 2a) that is directly connected to a microfluidic chamber in which cells are suspended. The microfluidic chamber is enclosed by the chip surface and a transparent cover tens of micrometers away from the chip surface. The surface of the active chip realizes a two-dimensional array of microcells, each of which consists of a planar electrode and an integrated logic circuit (Figure 2b). When placed in the area corresponding to the electrode, each electrode can be programmed to generate a potential well or dielectric cage. In each dielectric cage, the particles can be kept in a stable suspension state, allowing for individual analysis. Because each cell is analyzed individually, the system can perform complex fluorescence-based analysis to identify the unique characteristics that distinguish the target cell from the thousands of other contaminating cells. The target cells can be moved independently but simultaneously to a certain area of ​​the chip, where microfluidic control automatically recovers them.

Figure 2. Layout of DEPArray chip

DEPArray System

Our patented platform, DEPArray, is a flexible and easy-to-use advanced technology system (Figure 4). The core of the system is a microchip that integrates an array of 300,000 electrodes in a microfluidic circuit.

The DEPArray system uses NI hardware and software to manage high-precision mechanics, microfluidics, off-the-shelf electronics and custom tools, as well as vision and image processing. The workflow that the system allows users to perform can be summarized as follows:

Sample loading via microfluidics control

Acquire images in bright field and fluorescence

Analyze the image

Identify and select target cells via a graphical user interface

Automatic classification of identified target cells

Retrieval of target cells through microfluidics control

Sample loading

Sample loading is a very delicate process. We use NI LabVIEW software to control the pump device to generate the required pressure gradient, so that the sample flows from the inlet slot to the chip inside the microfluidic chamber. The system uses algorithms developed with the vision library of the NI Vision Development Module to automatically monitor and control the loading process.

Capture and analysis

Once the sample is loaded onto the chip, LabVIEW controls all I/O lines, configures the electrode array, cages the cells, and keeps them suspended during all stages of the process, ensuring robust and reliable system control.

Sample analysis is achieved by optically scanning the chip surface through multiple filters in fluorescence and bright field. LabVIEW controls the chip-mounted processing system and captures, images, and visualizes high-precision digital images obtained from the microscope with micron-level accuracy.

Select target cells

In this step, the DEPArray system provides users with a powerful human-machine interface (HMI), which was developed by LabVIEW combined with the Microsoft .NET framework, to classify and select target cells (Figure 3). Cells can be analyzed using different methods to verify their properties. The HMI displays scatter plots or histograms of the analysis measurement results and provides a list display of all the measurements on the image. For each cell selected, the image captured during the analysis is also displayed, allowing the user to combine the results of the computer measurements with the morphological evaluation.

Automatic classification

In this step, based on the cell map and obstacles, LabVIEW dynamically configures the chip electrode array to move each cell of interest from its initial position to the recycling point individually and simultaneously. Digitally controlling the movement of each cell of interest enables the system to achieve high classification purity and unparalleled performance.

Recycle

In this step, LabVIEW interacts with the peristaltic pump device to generate the required pressure gradient to make the buffer portion containing the selected cells flow downward in the recovery medium (such as a well in a microfluidic chamber or a glass slide). The sorting and recovery process can be repeated to collect multiple cells or multiple groups of purified cells separately for genetic analysis using traditional molecular biology techniques.

in conclusion

The technology developed by Silicon Biosystems leverages NI hardware and software with technology from Sky Technology to provide the means for a range of research activities, including isolating circulating tumor cells (CTCs) to study personalized treatment in oncology and identifying fetal cells in maternal blood for noninvasive prenatal diagnosis.