01
Dry Chemical Analysis Technology
Dry chemical technology is compared to traditional wet chemical technology, where the liquid present in the sample serves as the reaction medium. The components to be measured react directly with dry reagents fixed on a carrier, allowing for qualitative observation or instrument detection (semi-quantitative) for chemical analysis.
Single-layer Test Paper Technology: This includes single-item test strips and multi-item test strips. Single-item test strips can only measure one item at a time, such as the widely used blood glucose test strips, blood ammonia test strips, and urine glucose test strips. Multi-item test strips can detect several items simultaneously on one strip, which requires relatively more complex technology.
Multi-layer Coating Technology: This involves sequentially coating various reaction reagents onto a substrate to create dry plates, a technique adapted from photographic film production. Dry plates made using multi-layer coating technology can be accurately quantified using instruments. Currently, dry plate chemical analysis systems used clinically can analyze most blood chemical components, such as proteins, carbohydrates, lipids, enzymes, electrolytes, non-protein nitrogen, and some drug concentrations, covering dozens of commonly used clinical biochemical test items. The dry plates made using multi-layer coating technology mainly consist of three layers: diffusion layer, reagent layer, and support layer.
Principles of Dry Chemical Technology
02
Immunochromatography Technology
Immunochromatography (ICA) is a new type of immunoassay method that emerged in the early 1980s, based on immunofiltration (IFA). It is a simple and rapid immunoassay method.The principle of immunochromatography is to fix specific antibodies to a certain area of a nitrocellulose membrane. When one end of the dry nitrocellulose is immersed in a sample (urine or serum), the sample moves along the membrane due to capillary action. When it reaches the area where antibodies are fixed, the corresponding antigens in the sample specifically bind to the antibodies. If immunocolloidal gold or immunoenzymes are used, this area will display a certain color.If immunogold or immunoenzymes are used for staining, colored bands can be displayed, achieving specific immunodiagnosis.
Colloidal gold is formed by the reduction of chloroauric acid (HAuCl4) in the presence of reducing agents such as white phosphorus, ascorbic acid, sodium citrate, and tannic acid, resulting in gold particles of a certain size that become a stable colloidal state due to electrostatic forces, forming a negatively charged hydrophobic colloidal solution. The immunogold labeling technology is similar to enzyme immunoassay technology, using colloidal gold as a marker.
Dot immunofiltration tests were initially developed from dot ELISA, using enzyme-labeled conjugates, known as dot enzyme immunofiltration tests. In the early 1990s, dot immunofiltration tests using colloidal gold as a marker (DIGFA), also known as drop gold immunoassay (referred to as drop gold method), were developed. In the drop gold method, there is no need for enzyme-substrate reactions, making it simpler and faster, and it is increasingly used in clinical testing.
Principles of Immunochromatography Technology
03
Chemiluminescence Technology
Chemiluminescence immunoassay (CLIA) is a rapidly developing non-radioactive immunoassay method worldwide in the past decade, following enzyme-linked immunoassay (EIA), radioimmunoassay (RIA), and fluorescent immunoassay (FIR), and is a highly sensitive trace measurement technology.Chemiluminescence immunoassay combines high-sensitivity chemiluminescence measurement technology with highly specific immune reactions for the detection and analysis of various antigens, haptens, antibodies, hormones, enzymes, fatty acids, vitamins, and drugs.
The immunoassay method that directly labels antibodies or antigens with chemiluminescent agents is called chemiluminescence immunoassay. Currently, common direct chemiluminescent labels mainly include acridinium esters. When acridinium esters are directly labeled onto antibodies and react immunologically with the corresponding antigens in the sample, a solid-phase coated antibody-sample antigen-acridinium ester labeled antibody complex is formed. At this point, adding an oxidizing agent (H2O2) and NaOH to create an alkaline environment allows the acridinium ester to decompose and emit light without the need for a catalyst. The light produced is received and recorded by a photomultiplier tube, and the integral of this light is proportional to the amount of the antigen being measured, which can be calculated from the standard curve.
Principle of Direct Chemiluminescence
Enzyme-Linked Chemiluminescence Immunoassay (CLELA) uses enzyme-labeled antigens or antibodies for immunoreactions, where the enzyme on the immunoreaction complex acts on the luminescent substrate, emitting light under the action of signal reagents. The intensity of the chemiluminescence is determined by the concentration of the enzyme. Horseradish peroxidase (HRP) and alkaline phosphatase (ALP) are commonly used labeling enzymes in chemiluminescence immunoassays, with luminescent substrates represented by luminol and AMPPD.
Enzyme-Linked Chemiluminescence Based on Luminol + HRP Luminescent System
Electrochemical luminescence (ECLI) occurs when a certain voltage or current is applied to an electrode, resulting in a chemical reaction between the products of the electrochemical reaction or between the electrochemical reaction products and a component in the solution, producing an excited state. When the excited state transitions back to the ground state, energy is released. Electrochemical luminescence immunoassay (ECLIA) uses electrochemical luminescent agents such as tris(bipyridyl)ruthenium to label antibodies, with tripropylamine (TPA) as the electron donor, resulting in a specific chemiluminescent reaction due to electron transfer in an electric field, encompassing both electrochemical and chemiluminescent processes.
Principle of Electrochemical Luminescence
04
Biosensor Technology
A biosensor utilizes the molecular recognition capabilities of active substances such as proteins, enzymes, and nucleic acids to convert the conformational changes and concentration variations of the detected substances into quantifiable and visible physical and chemical signals, such as electrical signals and fluorescence signals, thereby achieving the detection of molecules like proteins and nucleic acids.
It generally consists of two parts: one is the biological or biochemical molecular recognition element (or receptor), composed of sensitive materials capable of recognizing biological or chemical molecules (such as chemical sensitive membranes made of electroactive substances, semiconductor materials, and biological sensitive membranes formed by enzymes, microorganisms, DNA, etc.); the other is the signal transducer (transducer), mainly composed of electrochemical or optical detection elements (such as current, potential measuring electrodes, ion-sensitive field-effect transistors, piezoelectric crystals, etc.).
Biosensor Schematic Diagram
Biosensor Materials and Applications
05
Biochip Technology
Biochip technology refers to the fixation of a large number of probe molecules onto a support, which then hybridizes with fluorescently labeled DNA or other sample molecules (such as proteins, factors, or small molecules) to detect the hybridization signal intensity of each probe molecule, thereby obtaining the quantity and sequence information of the sample molecules. Since glass slides/silicon wafers are commonly used as solid-phase supports, and the preparation process simulates the manufacturing technology of computer chips, it is referred to as biochip technology.
Currently, biochips can be divided into gene chips (Gene chip or DNA chip), protein chips (protein chip), cell chips (cell chip), and lab-on-a-chip (LOC). They have advantages such as high sensitivity, short analysis time, and the ability to analyze multiple items simultaneously, integrating many analytical steps involved in life science research using microelectronics, micromechanics, physical technology, sensor technology, and computer technology, making the sample detection and analysis process continuous, integrated, and miniaturized, and promoting the construction of micro-laboratories.
Principles of Biochip Technology
Typical Products of Gene Chips
06
Microfluidic Technology
Microfluidics is a science and technology characterized by the precise control and manipulation of micro-scale fluids, integrating basic operations such as sample preparation, reaction, separation, and detection into a chip of a few square centimeters, automatically completing the entire analysis process with precise control over the quantity and flow rate of samples and reagents. Its fundamental feature and greatest advantage is the flexible combination and large-scale integration of various unit technologies on an overall controllable micro platform.
Microfluidics can be implemented through various methods, including pressure-driven, centrifugal-driven, droplet microfluidics, digital microfluidics, and paper-based microfluidics. Currently, the first two methods are the most widely used.
Pressure-driven microfluidics primarily uses air pressure to drive fluids in the chip, appearing most frequently in the industrialization of microfluidics, such as bioMérieux’s FilmArray, Roche Diagnostics’ cobas Liat PCR System, Atlas Genetics’ io System, BGI Innovation’s HPV molecular diagnostic fully automated analyzer, and Huamaixingwei’s M2 miniaturized chemiluminescence analysis system. Centrifugal-driven microfluidics uses centrifugal force to drive fluids in microfluidic chips, also occupying an important position in the microfluidics industry, such as the Piccolo Xpress instant biochemical analyzer from Abaxis in the USA and Pointcare M from Tianjin Micro-Nano Chip Technology.
Microfluidic Technology/Microfluidic Chip Technology
07
Other Technologies
1. Infrared and Far-Infrared Spectrophotometry Technology
Commonly used for making transdermal detection instruments, which can detect various components in blood such as hemoglobin, bilirubin, glucose, etc. These detection instruments can continuously monitor the target components in the patient’s blood without the need for blood draws, avoiding cross-infection and contamination of blood samples, reducing the cost of each test and shortening report times. However, the accuracy of these transdermal detection results needs improvement.
2. Selective Electrode Technology
Using ion-selective electrodes combined with sensors, including biosensors and chemical sensor technologies, portable instruments for rapid detection of blood gases (pH, PCO2, PO2, etc.) and electrolytes (K+, Na+, Cl-, etc.) have been widely used in clinical settings.
3. Automatic Identification Technology
① Barcode Recognition Technology
To successfully implement barcodes, POCT requires the ability to recognize all items that need to be identified in the system, including patients, operators, test strips, and quality control (QC) materials. The barcodes on test strips and QC materials simplify the process of inputting critical data into the system. Currently, the POCT industry has adopted barcodes, and many POCT devices are equipped with built-in barcode scanners to improve data input.
② Radio Frequency Identification Technology
Radio frequency identification (RFID) technology is not limited by the shortcomings of barcodes and is a new technology still under development. RFID systems use a small electronic tag, which consists of a small integrated circuit connected to a micro-antenna, read by RFID scanners, similar to how barcode readers read printed barcodes. Data about the tagged object is stored in the memory of the integrated circuit, and information is wirelessly transmitted from the RFID tag to the reader via radio frequency signals.
By fully utilizing RFID technology, the POCT process can be greatly simplified. POCT devices with built-in RFID readers can collect information from all tagged objects within their reading range, quickly recording each data element to create error-free, medically valid test results.
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