A highly basic glycoprotein tetramer, each AVIDIN protein is an assembly of four identical subunits composed of 128 amino acids. Each of these subunits binds to Biotin (Vitamin H, Co-enzyme R, Vitamin B7) with extreme affinity, in the order of 10,000 to 10,000,000 times the strength at which an antibody binds to its antigen 1.
This biotin-binding by AVIDIN is not only strong, specific, and rapid, but resilient too, withstanding proteolytic enzymes and extremes of temperature and pH. These properties, it being one of the strongest natural non-covalent bonds identified, has made the AVIDIN-biotin system extensively employed across the biotech industry.
AVIDIN’s discovery came from the observation of ‘egg-white injury’ in animals fed a diet rich in raw egg-white. Symptoms resembling Biotin deficiency, despite the dietary sufficiency led to the identification of AVIDIN as the component that was rendering Biotin unavailable. For the egg, the source of AVIDIN, this function is a key line of defence in its nutritional immunity, similar to the iron-sequestering role of OVOTRANSFERRIN.
Most organisms other than plants and a few micro-organisms are unable to synthesise Biotin for themselves, so are heavily reliant upon these sources for their continued supply. This relative rarity in nature makes it precious, as Biotin is a key co-factor of enzymes critical for central cellular metabolic processes. By making the egg-white a ‘biotin-free zone’, AVIDIN starves invading organisms of this co-factor, binding all free Biotin to render them incapable of proliferating. This capability is potent, despite AVIDIN comprising a mere 0.05% of the total protein of the egg-white (a trace 1.8g per egg).
The strength with which AVIDIN binds to Biotin has been leveraged across biotechnology, nanotechnology, and biomedical fields where it used in medical device development, pharmaceuticals, research, and diagnostics. The 1:4 binding ratio makes this bond amenable to amplification of weak signals, improving signal-to-noise ratios, and aiding in detecting otherwise indiscernible biological phenomena. Biotin is relatively straight-forward to attach to binders, and probes in a process termed biotinylation, making the AVIDIN-biotin system highly versatile for a staggering number of applications.
Biotinylated fluorescent probes, ligands, and other imaging agents are readily available, and routinely generated in-house by chemical or enzymatic means2. This makes the AVIDIN-biotin system relied upon as the go-to technology for affinity purification, immuno-assays, diagnostics, and non-radioactive labelling among others. In nanotechnology the AVIDIN-biotin system has been effectively applied for the delivery of nucleic acids, proteins, peptides, and monoclonal antibodies (MAbs) 3. The strength and specificity of the bond overcomes the aggregation, short-systemic half-life, and low cellular uptake challenges faced when delivering siRNAs, and peptides.
Beyond this, AVIDIN promotes cellular internalisation and improves target specificity, making it an effective delivery carrier.
Another property of AVIDIN and biotin is that of their accumulation and targeting of cancerous cells. These tend to express biotin to a higher level on their surface than surrounding tissues, making the AVIDIN-biotin system tuneable for pretargeting and other anticancer therapeutics 4. This has been utilised particularly effectively in radioimmunoguided surgeries using radiolabelled MAbs5.
The potential, and existing use-cases for the AVIDIN-biotin system are vast given its workhorse reliability, versatility, sensitivity, and ease of application. These are of course too extensive for us to fully outline here, so we direct readers wishing to know more to excellent reviews by Jain A & Cheng K. 2 , and Sakahara H & Saga T6.
- Molecular signal amplification to improve bioassay sensitivity
- Flow cytometry, blotting, microarrays, ELISAs
- Delivery of nucleic acids, peptides, proteins, and MAbs
- Increasing cellular uptake of attached moieties
- Genetic probe for gene mapping
- Secondary histochemical detection reagent
- Detection of fluorescent biocytins in neuroanatomical tracing
- Unlabelled detection of mast cells in human tissues
- Capture/release of biotinylated targets
Benefits of Bioseutica®’s Avidin
Bioseutica® produces ultra-high purity AVIDIN, making it particularly attractive for maximising the efficacy of probes and derivatives which rely on minimising background. We provide a full range of services, technical and application support to help our customers meet their unique product requirements. Our Quality Control Systems ensure reliable performance and quality. Customers are encouraged to request and review our analytical results prior to shipment for pre-approval as required.
Contact us today to learn more about our first choice AVIDIN.
Non-Warranty : The information contained herein is provided in good faith and, to the best of our knowledge, is true and correct. However, no warranty or guarantee is implied or inferred, and the information may be subject to change without further notice. Bioseutica®’s products are sold with the understanding that the purchaser will conduct tests to determine the suitability of these products for their particular use.
- Diamandis EP & Christopoulos TK.: The biotin(strept)avidin system: principles and applications in biotechnology, Clinical Chemistry 1991
- Jain A & Cheng K.: The principles and applications of avidin-based nanoparticles in drug delivery and diagnosis, J Controlled Release 2016
- Pardridge WM.: Blood–brain barrier drug delivery of IgG fusion proteins with a transferrin receptor monoclonal antibody, Expert Opinion on Drug Delivery 2015
- Lesch H et al.: Avidin-biotin technology in targeted therapy. Expert Opin. Drug Deliv. 2010
- Stella M et al.: Avidin-Biotin System in Radioimmunoguided Surgery for Colorectal Cancer. Dis. Colon Rectum 1994
- Sakahara H & Safa T.: Avidin–biotin system for delivery of diagnostic agents, Advanced Drug Delivery Reviews, 1999.