Nanobodies
The year 1989 marked a mind-boggling breakthrough in the scientific realm with the discovery of nanobodies. These peculiar antibodies, derived from camelid animals, lack light chains. Nanobodies boasted a molecular weight of a mere 15 ku, a fraction of the weight of their conventional counterparts. The crystal structure of nanobodies measures just 4 nm in length and 2.5 nm in diameter, earning them the title of the tiniest antibodies known to mankind. Unlike traditional antibodies, nanobodies possess an elongated active binding region, with a plenitude of amino acids ranging from 16 to 18. Furthermore, the wide range of pH levels nanobodies can tolerate a wider range of pH levels (traditional antibodies can only tolerate pH 6-9, while nanobodies can tolerate pH 2-11).
Fig. 1 General nanobody structure and types of nanobodies (Yang, E.Y., Shah, K. 2020).
Advantages of Nanobodies
- Nanobodies have a lower relative molecular weight but stronger antigen-binding activity.
- Nanobodies have better water solubility and usually have higher expression levels.
- The disulfide bonds in nanobodies are less prone to breakage, resulting in higher stability.
- Due to their smaller molecular weight and size, nanobodies can easily penetrate cells and efficiently capture relevant pathogens within the cells.
Nanobodies in Disease Diagnosis and Treatment
Nanobodies have shown excellent application value and prospects in central nervous system diseases, circulatory system diseases, infectious diseases, tumors, and inflammatory diseases. Relevant research has mainly focused on tumor treatment and has achieved remarkable results. Although monoclonal antibodies are also used in the field of tumor imaging, due to their weak tumor penetration ability and long serum half-life, it is difficult to form high-contrast images during tumor imaging, thus limiting it to a certain extent. Nanobodies have a small molecular weight and are more likely to penetrate into tumor tissues. Therefore, nanobodies can detect more target distributions when used in tumor imaging. Meanwhile, nanobodies have a shorter residence time in the human body due to their short half-life, which avoids their systematic distributions in tumor imaging, and thus nanobodies can produce high tumor/background ratios shortly after administration. In addition, nanobodies can be used as an ideal tool for treating viral infections in animals and plants, providing timely intervention and control of the spread of pathogens.
Nanobodies in Food Safety Testing
In the field of food safety testing, nanobodies mainly play a role in several aspects such as pesticide and veterinary drug residues, food additives, biological toxins, pathogenic microorganisms, and environmental pollution. Currently, specific nanobodies for detecting various pesticides and their metabolites, and toxins in crops or food have been developed through genetic engineering and protein engineering, such as nanobodies for detecting fenitrothion in fruits and vegetables, procymidone in leeks, pesticide metabolite 3-phenoxy benzoic acid. The stability of these nanobodies has also been characterized. Multiple methods, such as conventional enzyme-linked immunosorbent assay, immunochromatographic test strips, biotin labeling, and fluorescence immunodetection technology, have been established to validate their high sensitivity, in order to better and wider applications in food safety.
In short, nanobodies have a small molecular weight, high water solubility, strong stability, and strong penetrating power. It is a new generation of "biotech missiles" following monoclonal antibodies.
Reference
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Yang, E.Y.; Shah, K. Nanobodies: next generation of cancer diagnostics and therapeutics. Frontiers in Oncology. 2020, 10: 1182.
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