Single-domain antibodies allow a broad range of applications in biotechnical as well as therapeutic use due to their small size, simple production and high affinity. The coupling of an anti-
GFP Nanobody to a monovalent matrix, called GFP-nanotrap, allows the isolation of GFP-fusion proteins and their interacting partners for further biochemical analyses. Single molecule localization with super-resolution imaging techniques requires the specific delivery of
fluorophores into close proximity with a target protein. Due to their large size the use of antibodies coupled to organic dyes can often lead to a misleading signal owing to the distance between the fluorophore and the target protein. The fusion of organic dyes to anti-GFP nanobodies targeting GFP-tagged proteins allows nanometer spatial resolution and minimal linkage error because of the small size and high affinity. The size dividend of nanobodies also benefits the
correlative light-electron microscopy study. Without any permeabilization agent, the cytoplasm of the chemically fixed cells are readily accessible to the fluorophore tagged nanobodies. Their small size also allows them to penetrate deeper into volumetric samples than regular antibodies. High ultrastructural quality is preserved in the tissue that is imaged by fluorescence microscope and then electron microscope. This is especially useful for the neuroscience research that requires both molecular labeling and electron microscopic imaging. In diagnostic
biosensor applications nanobodies may be used prospectively as a tool. Due to their small size, they can be coupled more densely on biosensor surfaces. In addition to their advantage in targeting less accessible epitopes, their conformational stability also leads to higher resistance to surface regeneration conditions. After immobilizing single-domain antibodies on sensor surfaces sensing human
prostate-specific antigen (hPSA) were tested. The nanobodies outperformed the classical antibodies in detecting clinical significant concentrations of hPSA. To increase the
crystallization probability of a target molecule, nanobodies can be used as crystallization
chaperones. As auxiliary proteins, they can reduce the conformational heterogeneity by binding and stabilizing just a subset of conformational states. They also can mask surfaces interfering with the crystallization while extending regions that form crystal contacts. nanobodies targeting the cell receptor binding domain of the
virulence factors toxin A and toxin B of
Clostridioides difficile were shown to neutralize cytopathic effects in
fibroblasts in vitro. Nanobody conjugates recognizing antigen presenting cells have been successfully used for tumor detection or targeted antigen delivery to generate strong immune response. Orally available single-domain antibodies against
E. coli-induced diarrhoea in piglets have been developed and successfully tested. Detergent-stable species targeting a surface protein of
Malassezia furfur have been engineered for use in anti-
dandruff shampoos.
Caplacizumab, a single-domain antibody targeting
von Willebrand factor is in
clinical trials for the prevention of
thrombosis in patients with acute coronary syndrome. A
Phase II study examining ALX-0081 in high risk
percutaneous coronary intervention has started in September 2009.
Ablynx expects that their nanobodies might cross the
blood–brain barrier and permeate into large solid tumours more easily than whole antibodies, which would allow for the development of drugs against
brain cancers. One of the most common causes of
nagana –
Trypanosoma brucei brucei – can be targeted by sdAbs. Stijlemans et al. 2004 succeeded in inducing effective sdAbs from
rabbit and
Camelus dromedarius by displaying a
variable surface glycoprotein antigen to the vertebrates' immune systems using a phage. In the future, these therapies will surpass natural antibodies by reaching locations currently unreachable due to natural antibodies' larger size. == References ==