Principle and design of chemiluminescence quantitative immunoassay analyzer

Overview

For a long time, people mostly use photometers as the main detection instruments of optical signals. The principle is to convert optical signals into voltage or current signals through photoelectric conversion devices, and then amplify them. Its main features are: simple structure, stable performance, but low sensitivity and narrow linear range. At present, common optical detection instruments, such as infrared, visible, ultraviolet spectrophotometer, fluorescence spectrophotometer, microplate reader, illuminometer, etc., all adopt similar principles [1]. These technologies mainly use photodiodes, photosensitive cells, and optoelectronics. A coupler, or a conventional photomultiplier tube operating in a photocurrent amplification mode, is used as the detecting device.

Chemiluminescence quantitative immunoassay analyzer is a new generation of high precision and high stability detection instrument. This product is combined with the production of luminescent immunoassay kit and dedicated data analysis management software, which constitutes the only chemiluminescence immunoassay system in China [2], which can fully meet the high sensitivity in various clinical and basic medical fields. Requirements for quantitative and qualitative immunoassays.

The system uses 32-bit ARM7.0 as the control center, and communicates with the PC through standard RS-232 serial port connection and signal transmission commands. This machine has the characteristics of simple operation, high sensitivity, accurate counting and good stability.

1, the main performance indicators of the system

Power supply voltage: 220V±22V, 50Hz±1Hz; maximum input power: 220 VA±10VA noise floor: 0 RLU/S～100RLU/S; linear range: 500 RLU/S～1.8&TImes; 106RLU/S stability: CV ≤3% repeatability: CV≤3% sensitivity: (minimum detection limit)≤3&TImes;10-14W

2, instrument composition and working principle

The chemiluminescence immunoassay analyzer is mainly composed of five parts: single photon counter, mechanical transmission mechanism, central control unit, upper computer management analysis software, and printer. The number of photon pulses is processed by the control center RAM7.0 signal. On the one hand, the single-chip microcomputer controls the stepping motor in the X and Y directions to change the standard reagent and the sample sample of the patient; on the other hand, the RS-232 serial port communicates with the upper computer, The patient's information, analysis results, quality control maps, etc. are queried in real time, and the results of the analysis can be printed by the printer. The block diagram of the whole machine structure and the connection relationship with peripheral devices are shown in Figure 1:

Figure 1 Schematic diagram of the instrument system and working principle

2.1 The working principle of single photon counter

The instrument's light-detecting component uses a single-photon counter, the core of which is a special type of photomultiplier tube, which is an ultra-high vacuum cylindrical glass container in which a layer of light (called a window) is coated with a special layer. A rare metal with a photoelectric effect, called a photocathode; and a plurality of electrodes arranged in a special manner, called a dynode or an accelerating electrode; a further electrode at the rear is called an anode, and each electrode There is a DC high voltage [3, 4]. The structure of the single photon counter and its working principle are shown in Figure 2:

Figure 2 shows the structure of a single photon counter and its working principle

When a photon hits the photocathode, due to the photoelectric effect, the surface can generate weak electrons with weak energy, called photoelectrons; the electrons leave the photocathode and hit the first dynode again due to the action of DC high voltage. The energy provided by the DC high voltage creates an electron with a higher energy and a higher order of magnitude on the first dynode [5, 6]. This is repeated amplification of multiple dynodes, and finally the anode is produced. An energy pulse is much higher than the electrical pulse signal that the original sample emits. The signal is amplified by the preamplifier, and then the noise signal is removed by the comparator. Finally, the number of photon pulses is converted by the frequency divider, which is usually the relative illumination unit, that is, RLU (RelaTIve Luminescence Unit). In general, an RLU is equivalent to 10 photons.

2.2 The design of the lower position machine

The system uses MC68322 (128K Flash, 32K Ram) as the control center, with FPGA as the counting unit. The sample sample of the patient passes through the microplate and enters the photomultiplier tube PMT in the form of single photon, which is made by the high-precision cascade amplifier NE5205. Preamplification, and then through the FPGA to do the signal comparison (mainly to interfere with the signal), frequency division (get the appropriate frequency) and finally enter the microcontroller to do signal processing; the result of the processing can be displayed by the single-chip computer through the LCD, or through the RS-232 serial port Communicate with computer to realize human-computer interaction; use 4 photoelectric sensors to control the state of the stepper motor and change the position of the microplate. Its hardware structure block diagram is shown in Figure 3:

Figure 3 hardware structure block diagram

2.3 Design of upper computer management analysis software

The development tools of the upper IPC software use object-oriented Visual Basic.NET programming. Visual Basic.NET is a visual, object-oriented, and event-driven, structured, high-level programming language. It not only has simple programming, but also has easy interface design. At the same time, the visual data manager VisData, which is built-in, makes the development of database applications extremely convenient [7, 8]. Communication with PC through RS-232 serial port makes the operator very easy. Through the chemiluminescence analyzer, the results of the test, the print test list, the test batch number, the hospital name maintenance, the patient information management, the patient information query, the test process detection and the perfect help system can be clearly and accurately read on the display. The management system is user-friendly, easy to operate, intuitive, and has a wide range of information. The chemical luminaire analysis management interface is shown in Figure 4:

Figure 4 Chemiluminescence Analyzer Management Software Interface

3, the conclusion

With the development of modern quantum physics and the deepening of people's understanding of the microscopic characteristics of light, the development of optoelectronic technology and related components has been promoted. A new type of high sensitivity photodetector called single photon counter has been Recently introduced, its sensitivity and linear range have greatly exceeded other conventional technologies. Therefore, it has been rapidly applied to various fields such as aviation, aerospace, military, public security, scientific research, medical care, environmental protection, agriculture, and industry, and has become an important part of the modern high-tech field.

Due to its excellent performance, the single photon counter has become one of the most important parts of modern optical instruments and one of the future developments of clinical testing instruments [9]. In fact, it is because of its invention and application. Modern immune and genetic analysis technologies can be freed from the shackles of radioisotopes and truly enter a new era of safety and non-isotopes.

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