Aptamers are short, single-stranded DNA or RNA molecules that bind to specific target molecules. They are highly versatile and can bind to targets with high selectivity and specificity. Their targets can include small molecules, heavy metal ions, large proteins, and even whole cells. The specific binding capability of aptamers relies not on their primary structure, but on the tertiary structure formed from the primary sequence. They assume a variety of shapes due to their tendency to form helices and single-stranded loops. Their applications include therapeutics, targeted drug delivery, diagnostics, treatment monitoring, pre-clinical distribution & dosing studies, etc.
They are classified as the “chemical antibody” since they can be used in many similar applications. However, the two types of molecules differ in many aspects as well (see comparison in Table 1).
| Aptamers | Antibodies | |
| Size | 20-100nt, ~1/10 size of antibody | ~5nm |
| Building Block | Nucleotides | Peptides |
| Technology Maturity | New | A couple of decades on market, very mature in production |
| Reproducibility | High | Low |
| Cost of Production | Low | High |
| Production Time | Short | Long (cell culturing from cryovial to production size bioreactor takes a long time) |
| Synthesis Method | Chemical Synthesis | Produced from cell lines |
| Purification Methods | TFF, sterile filtration IEX chromatography, etc. | TFF, depth filtration, sterile filtration Affinity chrom, IEX chrom, etc. |
| Immunogenicity | Low | Higher compared with Aptamers |
| Stability | Stable at varying pH and temperature | Very sensitive to pH and temperature, etc. |