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Research Progress of Aptamer Screening-of Small Molecule Targets

Introduction to Aptamers

The production technology of monoclonal antibodies was developed in 1975. It can be used not only in basic science, but also in the fields of drugs and biosensors, and has great significance in medicine. The world's first therapeutic antibody was discovered in 1986 to prevent kidney transplant rejection. Since then, many antibody drugs have been found to be used to treat various diseases, such as asthma. However, monoclonal technology has certain limitations in treating diseases. For example, antibodies against lipids, carbohydrates and organic macromolecules have low affinity, and the affinity for drug coupling is affected to a certain extent. Therefore, artificial ligands-aptamers are gradually emerging.

Aptamers are single-stranded nucleic acid chains that can bind to various targets. They have unique advantages such as small size, low cost, uniform synthesis, custom modification, and nucleic acid template properties. They can expand the range of potential targets in the selection scheme. For example, small molecules and ion aptamers can supplement the use of antibodies and are emerging as a type of artificial ligand.

Nucleic acid aptamers are a type of specific single-stranded DNA or RNA, consisting of 20-110 nucleotides, with a sequence containing random sequences and fixed sequences. Through folding, they can form a small molecule group with a tertiary structure, high affinity, and specific binding to the target molecule. In recent years, the research and development of nucleic acid aptamers in the sensing analysis and detection applications of small molecules has been rapid, mainly used in food and environmental testing and biological analysis.

Classification of Small Molecule Targets

1. Toxins

Toxin molecules cannot produce antibodies, so detection is difficult. Using aptamers to screen out toxin molecules and construct sensor elements at the same time, toxins can be effectively and quickly detected. At present, aptamers for many toxin molecules have been produced, such as saxitoxin, ochratoxin, and rock sand anemone toxin.

2. Antibiotics

Antibiotics can effectively prevent and treat animal diseases and promote growth. They are widely used in animal husbandry. The abuse of antibiotics leads to the accumulation of antibiotics in animal-derived foods and the environment, which is harmful to human health and environmental safety.

At present, suitable nucleic acid aptamer sequences have been screened for antibiotics. These aptamers can be used to quickly detect antibiotics. For example, a rapid antibiotic test strip has been developed for kanamycin, with kanamycin-specific aptamers as probes and oligonucleotides complementary to the aptamers as signal amplification elements.

3. Hormones

Hormones can be used to treat a variety of diseases, mostly for anti-inflammatory, anti-toxic, anti-shock and immunosuppressive treatments at pharmacological doses. At present, aptamers have been obtained for various hormones (clenbuterol, 17β-estradiol, etc.) through SELEX in vitro screening technology, and their affinity has been determined by nanogold colorimetry.

4. Other small molecules

Biogenic amines/bases, peptides, natural products, dyes, pesticides, important monomeric small molecules and metal ions can all be used as targets for small molecule target nucleic acid aptamer screening.

Small Molecule Target Nucleic Acid Aptamer Screening

Small molecule target binding sites are few, and it is difficult to obtain small molecule target binding nucleic acid aptamers with high affinity and specificity. The following are the methods for screening small molecule target nucleic acid aptamers:

1) Screening technology based on target fixation

After development, the in vitro screening technology of aptamers based on target fixation has solved the problems of non-specific binding of aptamer libraries, exposure of target binding sites, poor affinity, chemical modification, etc.

2) Screening technology based on library fixation-Capture-SELEX

The screening technology based on library fixation-Capture SELEX overcomes the above technical problems. The aptamer library of this method consists of three parts: random sequence, docking sequence and primer sequence.

3) Homogeneous screening technology

Homogeneous screening technology improves the screening efficiency, and the screened nucleic acid aptamers can be converted into sensors.

4) GO-SELEX

GO has the advantages of strong hydrophilicity and good dispersibility, and is the new material with the best application effect in SELEX screening technology. The use of GO new materials can improve the screening efficiency of aptamers and increase the affinity of aptamers.

5) Quartz crystal microbalance-SELEX (QCM-SELEX)

Quartz crystal microbalance is extremely sensitive and can determine the strength of affinity by detecting the resonance frequency caused by mass change, and use this as a basis for screening.

6) Human genome-SELEX (Human-Genomic SELEX)

It has been reported that RNA aptamers that can bind to ATP are screened by using the human genome.

7) Computer-assisted-SELEX (In Silico SELEX)

① Use mFold software to predict the action sites of targets and aptamers, and optimize and shorten the effective sequences of aptamers.

② By computer simulation of specific points of aptamer sequences and point mutations, the nucleic acid sequences are modified and optimized to improve the affinity of aptamers.

Screening of Aptamers for Small Molecule Drugs

Small molecule drugs have contributed to medical progress and improved patients' lives, especially in improving treatment of specific indications. Using small molecule drug aptamer screening technology, high-affinity aptamers can be obtained and applied in the field of covalent drugs to overcome difficult-to-drug protein targets.

TekBiotech has successfully completed a number of nucleic acid aptamer projects and has rich experience and mature technology. In addition, TekBiotech also provides customized SELEX screening technology, antibody expression and purification, affinity determination, antibody sequencing, etc. to meet customer needs.

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