A single-domain antibody (sdAb), also known as a Nanobody, is an antibody fragment consisting of a single monomeric variable antibody domain. Like a whole antibody, it is able to bind selectively to a specific antigen.

A nanobody is a small, powerful fragment of an antibody that comes from animals like camels, alpacas, and llamas. Unlike conventional antibodies (which are Y-shaped proteins with two heavy and two light chains), nanobodies are just a single domain the smallest functional part of an antibody that still binds to its target.

Nanobodies are naturally produced by camelids (like llamas and alpacas). These animals have unique antibodies that lack light chains. Scientists extract blood samples, isolate the antibody genes, and use genetic engineering to produce nanobodies in bacteria or yeast.

Steps:

1. Immunize a camelid with a target protein.
2. Collect blood and isolate B cells that produce heavy-chain-only antibodies.
3. Extract and clone the gene for the variable domain (VHH).
4. Express the VHH gene in microbial systems.
5. Purify and test the nanobody.

Because they are small (about 15 kDa) and stable, nanobodies can be produced easily and cheaply in large quantities.

Because nanobodies have special features that make them better than regular antibodies in some cases, researchers are actively exploring their use in diagnostics. Figure 2 shows the different ways nanobodies can be used, the types of tests they work with, and where they might be applied.

Nanobodies are not only useful in research and diagnostics they also show great potential in therapeutic applications. Thanks to their small size, high stability, and strong binding to specific targets, nanobodies can be used in various ways to help treat diseases at the research and development level.

1.Targeting Disease Proteins

Nanobodies can block or bind to specific proteins involved in diseases, such as inflammatory molecules or tumor markers.

2.Drug Delivery

Because they can reach places regular antibodies can't, nanobodies are being tested to carry drugs directly to specific cells, such as cancer cells.

3.Crossing the Blood-Brain Barrier

Some nanobodies are small enough to pass into the brain, making them candidates for treating brain-related conditions in preclinical studies.

4.Neutralizing Toxins or Viruses

Nanobodies have been designed in labs to bind and block harmful viruses or bacterial toxins.

5.Immune System Modulation

Researchers are exploring nanobodies that can adjust the immune response—for example, turning it off in autoimmune conditions or boosting it to fight infections.

Although many nanobody-based therapies are still in development or testing, their unique advantages make them a promising tool for the future of targeted treatment.