Origin and nutritional immunity

AVIDIN was originally identified through “egg-white injury” experiments, in which animals fed raw egg whites developed symptoms resembling Biotin deficiency despite adequate dietary intake. AVIDIN was found to be responsible for sequestering Biotin and rendering it unavailable. In the egg, its natural source, AVIDIN plays a key role in nutritional immunity, analogous to the iron-sequestering function of OVOTRANSFERRIN. By creating a “biotin-free zone” in egg white, AVIDIN deprives invading microorganisms of an essential cofactor, limiting their ability to grow and proliferate.

Most organisms, with the exception of plants and a few microorganisms, cannot synthesize Biotin de novo and depend on exogenous sources. Biotin is a critical cofactor for several carboxylases involved in central metabolic pathways, including fatty acid synthesis, gluconeogenesis, and anaplerotic reactions. By binding essentially all free Biotin, AVIDIN can profoundly influence metabolic flexibility, a concept that is increasingly explored in areas such as cancer metabolism, glutamine addiction, and vitamin-dependent metabolic stress in experimental systems.

Key features

• Ultra-high affinity AVIDIN-biotin interaction (Kd ~10^-15) for highly sensitive assays.
• Exceptional stability against proteolysis, temperature extremes, and broad pH ranges.
• Defined 1:4 Biotin:AVIDIN binding stoichiometry, enabling robust signal amplification.
• Straightforward biotinylation of antibodies, ligands, nucleic acids, peptides, proteins, nanoparticles, and other biomolecules.
• Proven performance in in vitro diagnostics, immunoassays, imaging, and advanced research workflows.

Diagnostic applications (IVD / laboratory)

Signal amplification in bioassays

• Increased sensitivity in ELISA, CLIA, western blotting, and protein/DNA microarrays through AVIDIN-biotin amplification schemes.
• Improved signal-to-noise ratio and lower limits of detection in clinical laboratory and research assays, when used as a biotin-binding reagent.
• Broad compatibility with colorimetric, chemiluminescent, and fluorescent detection systems.

Flow cytometry, immunohistochemistry, imaging

• Use as a secondary detection reagent for biotinylated probes in flow cytometry and cell phenotyping.
• Signal amplification in immunohistochemistry (IHC) and immunofluorescence on paraffin-embedded and frozen sections.
• Support for multiplex staining and spatial biology workflows where AVIDIN-biotin chemistry enhances sensitivity and dynamic range.

Genetic probes, neuroanatomical tracing, histology

• Detection of biotinylated nucleic acid probes in gene mapping, FISH, in situ hybridization, and spatial transcriptomics.
• Visualization of fluorescent biocytins and related tracers in neuroanatomical studies.
• Use as a histochemical secondary reagent, including unlabelled detection of mast cells and other cell populations with high content of biotin-binding components.

Capture and release of biotinylated targets

• AVIDIN immobilized on beads, columns, plates, or surfaces for affinity purification of biotinylated proteins, antibodies, nucleic acids, and complexes.
• Pull-down, co-immunoprecipitation, and interactomics workflows in proteomics and functional genomics.
• Capture and controlled release of biotinylated targets for high-purity preparation and downstream analysis.

Advanced research applications (RUO)

Research use only / preclinical / in vitro-ex vivo.

Nanoplatforms and targeted delivery (RUO)

• Surface functionalization of nanoparticles, liposomes, micelles, and virus-like particles with AVIDIN to enable modular loading of biotinylated ligands (antibodies, peptides, aptamers, small-molecule targeting moieties) in experimental systems.
• Enhanced cellular uptake and targeting of nucleic acids (siRNA, miRNA, mRNA, plasmids) and proteins in in vitro and ex vivo models through multivalent AVIDIN-biotin interactions.
• Flexible design of targeted delivery concepts for oncology, gene- and immune-modulation research, where payload and targeting components can be combined or exchanged via biotinylation in preclinical studies.
• AVIDIN’s ability to promote cellular internalization and improve target specificity makes it an effective carrier for molecular payloads in experimental platforms, not for direct therapeutic use.

Metabolic and oncology research (RUO)

• Creation of Biotin-depleted microenvironments in 2D/3D cell culture (including spheroids and organoids) to study Biotin-dependent enzymes such as pyruvate carboxylase (PC), acetyl-CoA carboxylase (ACC), and propionyl-CoA carboxylase (PCC).
• Biomimetic models of nutritional immunity, where AVIDIN reproduces the egg-white “Biotin-free zone” in vitro to investigate microbial and tumor-cell responses to vitamin B7 deprivation.
• Use of AVIDIN to functionally deplete Biotin in tumor cell models exposed to glutamine-targeting agents, enabling dissection of escape mechanisms and identification of synergistic combinations at research stage.

Immunometabolism and tumor microenvironment (RUO)

These applications are intended for research use only and are particularly relevant for groups working in metabolic oncology, immunometabolism, and nutrient-based therapeutic strategies in preclinical models.

• Co-culture models of tumor and immune cells where AVIDIN modulates Biotin availability to study effects on macrophage polarization, T-cell activation, angiogenesis, and checkpoint responses.
• Exploration of vitamin-dependent metabolic checkpoints in the tumor microenvironment to understand interactions between nutrient availability, immune function, and tumor progression.

Pretargeting and oncologic imaging (preclinical / RUO)

• Cancer cells can display elevated Biotin uptake or can be targeted with biotinylated ligands, making the AVIDIN-biotin system a powerful platform to study pretargeting strategies in oncology at the preclinical level.
• Multi-step AVIDIN-biotin pretargeting schemes combining biotinylated targeting vectors and radiolabelled Biotin or AVIDIN are widely investigated in animal models and ex vivo settings to improve tumor-to-background ratios in experimental imaging.
• AVIDIN-based probes can also be used ex vivo on tumor specimens to explore Biotin-related markers and support biomarker discovery and patient-stratification concepts in early-stage research.

Use cases

• Molecular signal amplification to improve bioassay sensitivity in clinical laboratory and research diagnostics.
• Flow cytometry, western blotting, microarrays, and high-sensitivity ELISAs.
• Capture and release of biotinylated proteins, nucleic acids, and complexes for affinity purification and proteomics.
• Targeted delivery of nucleic acids, peptides, and proteins in in vitro and ex vivo experimental systems.
• Genetic probes for gene mapping, FISH, in situ hybridization, and spatial transcriptomics.
• Secondary histochemical detection reagent in IHC, immunofluorescence, and histopathology.
• Detection of fluorescent biocytins in neuroanatomical tracing.
• Creation of Biotin-depleted environments to study vitamin B7-dependent enzymes, cancer metabolism, glutamine addiction, and nutritional immunity (RUO).
• Investigation of pretargeting concepts for oncologic imaging and experimental radionuclide strategies in preclinical research.

The AVIDIN-biotin system has also been investigated in the literature as a platform for pretargeted radioimmunoimaging and experimental radionuclide therapy in animal models and early clinical studies; these approaches are described here as background on the technology and do not represent approved indications for Bioseutica AVIDIN.

References

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• Balzer AHA, Whitehurst CB. An Analysis of the Biotin-(Strept)avidin System in Immunoassays. 2023. Publisher Site