Nanoantibodies: small molecules, big possibilities.

Camelids (camels, dromedaries, alpacas, llamas, and vicuñas) contain in their serum conventional heterodimeric antibodies as well as antibodies with no light chains (L) in their structure and composed of only heavy chains (H), called as HcAbs (heavy chain antibodies). Variable fragments derived from these antibodies, called as VHH or nanoantibodies (Nbs), have also been described. Since their discovery, Nbs have been widely used in the fields of research, diagnostics, and pharmacotherapy. Despite being approximately one-tenth the size of a conventional antibody, they retain similar specificity and affinity to conventional antibodies and are much easier to clone and manipulate. Their unique properties such as small size, high stability, strong antigen binding affinity, water solubility, and natural origin make them suitable for the development of biopharmaceuticals and nanoreagents. The present review aims to describe the main structural and biochemical characteristics of these antibodies and to provide an update on their applications in research, biotechnology, and medicine. For this purpose, an exhaustive search of the biomedical literature was performed in the following databases: Medline (PubMed), Google Scholar, and ScienceDirect. Meta-analyses, observational studies, review articles, and clinical guidelines were reviewed. Only original articles were considered to assess the quality of the evidence.