Aptamer

Pegaptanib induced fit binding

Breast cancer spheroids with aptamers

Jack wiki photo

Anti-VEGF 165 and anti-IFNy aptamer secondary structure prediction

Aptamer gel mobility shift assay

Aptamers are short, single-stranded DNA or RNA molecules that can bind to specific targets with high affinity and specificity. They are selected from a large pool of random sequences through a process known as Systematic Evolution of Ligands by Exponential Enrichment (SELEX). Due to their unique properties, aptamers are used in a wide range of applications, including therapeutic agents, diagnostic tools, and biosensors.

Overview

Aptamers are often referred to as chemical antibodies because of their ability to specifically bind to a target molecule, similar to how antibodies bind to their antigens. However, unlike antibodies, aptamers are synthesized chemically, which allows for easier production and modification. This synthetic nature also means that aptamers do not induce immunogenic responses, making them suitable for therapeutic and diagnostic applications.

Selection Process

The SELEX process is the cornerstone for aptamer selection. It involves several rounds of binding, separation, and amplification steps to enrich aptamers with the highest affinity for the target molecule. The process starts with a large library of random sequence oligonucleotides. These sequences are exposed to the target, and sequences that bind to the target are separated from those that do not. The bound sequences are then amplified using Polymerase Chain Reaction (PCR) for DNA aptamers or reverse transcription PCR for RNA aptamers. This cycle is repeated multiple times, each time enriching the pool with sequences that have a higher affinity for the target.

Applications

Aptamers have found applications across various fields of science and medicine. In therapeutics, aptamers can be used as drugs due to their ability to specifically bind and inhibit the function of target molecules. An example is Pegaptanib, an aptamer used in the treatment of age-related macular degeneration, which targets vascular endothelial growth factor (VEGF).

In diagnostics, aptamers are used in biosensors and diagnostic assays due to their specificity and ease of modification. They can be engineered to carry reporter molecules, such as fluorophores, which emit a signal upon binding to the target, allowing for the detection of various biomolecules.

Aptamers are also used in research as tools for molecular recognition, purification, and analysis. They can be used to isolate specific proteins from complex mixtures or to study the interaction between molecules.

Advantages over Antibodies

Aptamers offer several advantages over antibodies, including:

• Easier and more cost-effective production
• Higher stability, allowing for long-term storage without loss of activity
• Lack of immunogenicity, making them safer for therapeutic use
• Ability to be easily modified with functional groups, increasing their versatility

Challenges and Future Directions

Despite their potential, the use of aptamers is still limited by challenges such as their rapid degradation in biological fluids and the need for efficient delivery methods in therapeutic applications. Ongoing research is focused on chemical modifications to increase their stability and the development of novel delivery systems.

Aptamers represent a promising class of molecules with the potential to impact various areas of medicine and biotechnology. As research progresses, it is likely that their applications will expand, offering new solutions to current challenges in diagnostics, therapeutics, and beyond.

Aptamer Resources
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