Selection Guide for Chemiluminescence Imaging System

The development of scientific research is always inseparable from technological innovation. The invention of the microscope, the establishment of the slicing technology and the dyeing technology have allowed human beings to move from the macroscopic world into the microcosmic world that recognizes the human body itself. The creation of technologies such as immunochemistry, in situ hybridization, and nucleic acid amplification has enabled humans to further understand the changes in protein and nucleic acid levels in tissue cells, which has greatly improved human understanding of normal tissues, cells, and diseases.

The development of digital imaging technology has made Westernblot one of the most commonly used methods in protein research. Therefore, chemiluminescence imaging systems with higher sensitivity and data analysis functions have gradually replaced traditional film methods and become every laboratory involved in life science research. Necessary equipment. How to purchase a chemiluminescence imaging system has become a problem that many users are troubled by. This article will introduce the chemiluminescence imaging system in detail around this issue, and hope to help chemiluminescence users.

1. The basic principle of chemiluminescence imaging Chemiluminescense is the chemical reaction of two substances A and B to form substance C. The energy released by the reaction is absorbed by the molecules of substance C and transitions to the excited state. The excited C * is returning. In the process of reaching the ground state, optical radiation is generated. Due to the phenomenon of light radiation accompanying the chemical reaction, it is called chemiluminescence. It is often used to detect proteins and DNA in the field of biology. It does not require an excitation light source such as ultraviolet light during the reaction. It relies on specific enzymes such as HRP or AP to bind to the substrate to promote the reaction. The optical radiation usually generated is very weak, and the optical signal is not easy to collect. C *

2. Features

Compared with the traditional film method, the chemiluminescence method has:

1. High sensitivity, data results can be used for quantitative analysis;

2. No need for darkroom or tableting;

3. Automatically complete the exposure, the key band will not be lost due to underexposure or overexposure;

4. No consumables;

5. The picture result is an electronic file, which is convenient for data analysis, archiving and long-term preservation;

3. Technical parameter requirements

The imaging system generally takes CCD camera, darkroom and software as the main components. CCD is the abbreviation of Charge Coupled Device (Charge Coupled Device), is a photoelectric conversion device, and is the core component of the imaging system. The light signal generated by chemiluminescence is very weak, so the performance requirements of the CCD of the chemiluminescence imaging system are relatively high. The indicators to measure the quality of the CCD are resolution, CCD size, dynamic range, sensitivity, quantum efficiency, signal-to-noise ratio, etc., where the number of pixels and CCD size are important indicators. The larger the area of ​​the CCD photosensitive device, that is, the larger the CCD area, the more photons captured, the better the photosensitive performance, and the lower the signal-to-noise ratio. However, high pixels are not necessarily a good CCD. The reason is that the pixel size (Pixel Size), the denser the arrangement of the same number of pixels, the more susceptible to current interference between pixels, prone to "noise" and other phenomena that interfere with imaging quality appear. Facts have proved that the pixel size is most suitable in 7 ~ 10um2.

Chemiluminescence also needs to be accumulated for a period of time to obtain the best exposure results. When the exposure exceeds 5-10 seconds, the CCD chip will heat up. If there is no chip of the cooling device, the "hot" or white pixels will cover the image, and snowflakes can be seen everywhere in the image. CCD structure design, digital methods, etc. will affect the generation of noise. Of course, by improving the structure and optimizing the method, the noise can also be reduced. For example, SenSo View technology introduced by VILBER is a technology that eliminates background noise before imaging.

Table 1. Technical parameter list

Technical parameter requirements

Basic requirements

1. High-sensitivity cooled CCD: large CCD, the number of pixels is at least 2 million, and the pixel size is at least 7um × 7um; the absolute temperature of CCD cooling is at least -25 degrees, the dynamic range is 4.8OD, and the gray scale is 16bit

2. Automatic operation requirements: automatically adjust the lens and aperture, automatically calculate the exposure time, and automatically remind the function of overexposure;

3. Software: It has two sets of software for image acquisition and data analysis.

High-end requirements

1. High-sensitivity cooled CCD, the number of pixels is at least 4 million, and the pixel size is 10 um × 10um; the absolute temperature of the CCD cooling can reach -42 degrees, the dynamic range is 4.8OD, and the gray scale is 16bit;

2. Automatic operation requirements: automatically adjust the lens and aperture, automatically calculate the exposure time, and automatically remind the function of overexposure;

3. Software: It has two sets of software for image acquisition and data analysis.

4. Application Examples

The chemiluminescence imaging system can be used for the detection of samples after various chemiluminescence exposures such as ECL, ECL PLUS, Southern, CDP Star, CSPD, Northern and Western hybridization chemiluminescence. It can also be used for bioluminescence detection of cells or DNA labeled with luciferase gene. If equipped with ultraviolet, red, green, blue and other excitation light sources, it can also perform multi-color fluorescence to achieve simultaneous detection of more than two target proteins.