A biochip or microarray chip is a microscope slide for the laboratory, usually made of silicon chip, glass, nylon film. It is usually a 2D array (sometimes 3D) with thousands of microwells at defined locations on the chip surface. The microarray chip analysis technology was discovered almost 20 years ago. The technology is mainly used in cancer research and drug treatment of other diseases, such as oral lesions. It helps researchers investigate and analyze the expression of thousands of genes in a single reaction and solve a variety of questions.
The working principle of microarray technology is the binding of DNA complementary sequences to each other. There are different classifications of microarrays based on how they are prepared and the types of probes used.
Ⅰ. Based on the classification of preparation methods, microarray chips can be divided into three categories
1. In situ synthesis array: The in situ synthesis array is made by chemical synthesis on a solid phase substrate. During chemical synthesis, photolabile protecting groups are combined with photolithography to perform manipulations. In situ synthesized arrays are mainly used for expression analysis, genotyping and sequencing.
2. Dot array on glass: The dot array is made of polylysine-coated glass slides. High density DNA binding is provided through the use of grooved pins. It allows fluorescent labeling of samples.
3. Self-assembled array: This is a fiber optic array made by deposition of synthetic DNA on polystyrene microbeads. These beads are deposited on the etched end of the array. Different DNAs can be synthesized on different microbeads, and a mixture of microbeads can be coated on the optical fiber to form a random self-assembled array.
Ⅱ. Classification based on the type of probe used, microarray chips can be divided into 12 different types
1. Tissue microarray: Tissue chip. Tissue microarray paraffin blocks are formed by isolating cylindrical tissue cores from various donor tissues and embedding them into individual microarrays. It is mainly used in pathological research.
2. Protein microarray: that is, protein chip. As a platform, it can characterize hundreds of thousands of proteins in a highly parallel fashion. There are three types of protein microarrays, namely analytical protein microarrays, functional protein microarrays and reversed-phase protein microarrays.
3. DNA microarray: DNA microarray is also called gene chip, DNA chip or biochip. It can both measure DNA and use DNA as part of its detection system. DNA microarrays can be subdivided into four categories: cDNA microarrays, oligonucleotide DNA microarrays, BAC microarrays and SNP microarrays.
4. MMChips: Mmchips allow comprehensive analysis of data across platforms and between laboratories. It is mainly used to study the interaction between DNA and protein. ChIP-chip (chromatin immunoprecipitation followed by array hybridization) and ChIP-seq (chromatin immunoprecipitation followed by massively parallel sequencing) are the two main techniques used.
5. Peptide microarray: This type of array is mainly used for specific analysis or optimization of protein-protein interactions. It aids in antibody identification by screening the proteome.
6. Reverse-phase protein microarray: They are microarrays made of lysate or serum. Mainly used in clinical trials, especially in the field of cancer, but also in the pharmaceutical industry. In some special cases, they can also be used for biomarker research.
7. Antibody microarrays: They are also called antibody arrays or antibody microarray chip. Antibody microarrays are protein-specific microarrays that contain collections of capture antibodies within a microscope slide, primarily for the detection of antigens.
8. Interferometric reflectance imaging sensor (IRIS): IRIS is a biosensor that can be used to analyze protein-protein, protein-DNA, and DNA-DNA interactions. It does not use fluorescent labels, but is machine-spotted and made of Si/SiO2 substrates.
9. Cell microarray: the cell chip. Also known as transfection microarrays or live cell microarrays, they can be used to screen large compound and genomic libraries and systematically study the microenvironment of localized cells.
10. Glycan array: also known as sugar chip. Glycan arrays are primarily used to screen carbohydrate-bound proteomes. They can also be used to calculate protein affinity and automate solid-phase supported synthesis of glycans.
11. Phenotypic Microarrays: Phenotypic microarrays or PMs are mainly used in drug development. They can quantitatively measure thousands of cellular phenotypes at a time. It is also used in functional genomics research and toxicology testing.
12. Compound microarray: mainly used for drug screening and drug discovery. The ability of compound microarrays to identify and evaluate small molecules makes it more useful than other techniques in the pharmaceutical industry.
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