The application of colloidal gold in the medical field

1. Immunoblotting

Western blotting is to transfer the protein bands separated by polypropylene phthalamide gel electrophoresis to nitrocellulose membrane, and then use enzyme immunoassay (or immunofluorescence, RIA) for quantitative analysis. Similarly, gold labeled cartridge immunocolloidal gold can also be used for immunoblotting. After the transferred nitrocellulose membrane is warmed with specific antibodies, it reacts with staphylococcal or kammel white sensitized colloidal gold to wash away excess colloidal gold. The amount of specific antigen in the sample is estimated based on the color of the colloidal gold particles on the membrane. Gold labeled cartridge colloidal gold immunoblotting is a simple, rapid, and highly sensitive technique that has great potential for clinical immunodiagnosis.

2. Immunogold electron microscope

The application of immunogold electron microscopy has gone further through the study of tissue and cell localization to the level of gene transcription, gene expression detection, chromosome gene localization, spatial distribution analysis of specific nucleic acid sequences within the cell, and qualitative or quantitative analysis during nucleic acid replication. The non isotope nucleic acid probe technology of colloidal gold labeled anti digoxin antibodies is very useful in nucleic acid assay, PCR product analysis, and in situ hybridization. In recent years, streptavidin colloidal gold probes have emerged in the field of in situ hybridization and immunocytochemistry. They not only can localize DNA sequences at the ultrastructural level on chromatin and chromosomes, but also can be used for laboratory diagnosis of mammalian tissue growth, related diseases, virus genotypes, and phenotypes. They have become a new type of cytochemistry testing reagent with broad application prospects.

3. Flow cytometry

Using fluorescein labeled antibodies to count and analyze cell surface antigens by flow cytometry is one of the important techniques in immunological research. Boehmer et al. found that colloidal gold can change the scattering angle of red laser light. They applied colloidal gold labeled sheep anti mouse IgG bodies to flow cytometry to analyze surface antigens of different cells. The results showed that mouse spleen cells could be labeled with antibodies that bind to both fluorescein and colloidal gold without interfering with each other. Therefore, colloidal gold can be used as an effective marker for multi-parameter cell analysis and sorting, analyzing various cell surface markers, roll surface receptors, and surface antigen gamma cell inclusions.

4. Rapid diagnosis

New technologies such as adsorption test, latex agglutination test, monoclonal antibody technology, immune colloidal gold technology, and new material technology have been rapidly popularized in the field of diagnosis and have become increasingly mature due to their convenient, sensitive, and low-cost characteristics. In 1980, Leuvering earlier reported an agglutination test using colloidal gold to detect human chorionic gonadotropin (hCG). After that, in 1985, the commercial kit was successfully developed, and since then, colloidal gold has become a new hotspot in the research and development of immunological assay methods. New methods and kits have emerged in an endless stream, mainly applied to the detection of hormones and drug residues, as well as the detection of disease related proteins, antigens, or antibodies. This technology, combined with a signal amplification system, can quantitatively detect trace substances and simultaneously detect multiple objects, which has great application value for substances with joint detection significance.

5. Biosensor

In recent years, the application of gold labeling in biosensors has been increasing. Kim detected the immune agglutination of gold labels on the interdigital electrode by alternating current conductance method, thereby realizing the electrochemical detection method of colloidal gold immunochromatography test. Moreover, by coating conductive polyaniline on the colloidal gold, the sensitivity of conductance method for determining the immune reaction of gold labels was improved. Based on colloidal gold labeled protein A, Brainina has developed an electrochemical immunosensor for the diagnosis of forest encephalitis, which is used for the determination of forest encephalitis antibodies and their concentrations in serum.

6. Other aspects

① As an immunogenic substance. In 2004, Dykman conducted an experimental study on the immunogenicity of colloidal gold particles, using colloidal gold as a hapten carrier to immunize experimental animals. It was found that colloidal gold has direct immune adjuvant activity, which can enhance non specific immune responses, improve the concentration of lysozyme in the blood, complement activity, phagocytosis, and bactericidal effect. In addition, using colloidal gold hapten as an immunogen can induce the formation of highly active antibodies without the need for Freund's complete adjuvant, and the amount of antigen used is less than using Freund's complete adjuvant As an immune enhancing adjuvant. In 2003, Zhao mixed various colloidal gold particles and plasmids encoding the PrM-E protein of Japanese encephalitis virus into mice, which could enhance the production of antiviral proteins and protective immune responses. This method can be used to develop new DNA vaccines against Japanese encephalitis virus. In the same year, Zhang et al. discovered that gold particles as adjuvants have an immune enhancing effect on the electroporation expansion of DNA vaccines As a drug carrier. Paciott et al. studied the role of gold particles in drug delivery in vivo and found that colloidal gold particles can guide tumor necrosis factor (TNF) to solid tumors in mice. Compared with natural TNF, the PT (thiolated PEG) - Au recombinant TNF complex is less toxic and can reduce tumors effectively, and obtain a large anti-tumor effect with a small dose of drugs.