Introduction to Peptide Aptamers

Monoclonal antibody production technology 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 and used 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 of drug coupling is affected to a certain extent. Therefore, artificial ligands-aptamers have gradually emerged.

Aptamers are a class of small molecules composed of single-stranded nucleic acids (DNA or RNA) that can specifically recognize and bind to various targets, such as proteins, peptides, small molecules, metal ions, viruses and cell surface receptors. Compared with traditional antibodies, aptamers have many unique advantages, which make them show great application potential in biomedicine, diagnosis and treatment. First, aptamers are relatively small in size, usually only a few hundred to a few thousand base pairs, so they can more easily penetrate biological barriers in drug delivery and targeted therapy, and have strong tissue permeability. Secondly, the synthesis cost of aptamers is low, and the synthesis process is relatively simple, which can quickly generate a large number of uniform molecules in the laboratory. This makes the research and application of aptamers more economical and efficient. In addition, aptamers can be chemically modified to enhance their stability, affinity, specificity and biological activity to meet the needs of different research and treatment. Aptamers have a wide range of applications, especially in small molecules and ion aptamers, which can supplement the deficiencies of antibodies in some specific fields. For example, small molecule aptamers can recognize and bind small molecules or low molecular weight compounds that are difficult to recognize by antibodies, which is of great significance in drug screening, toxicology research, environmental monitoring and other aspects. Metal ion aptamers have application potential in water treatment, metal detection and monitoring of heavy metal pollution.

Peptide aptamers are a class of short peptide chain molecules with high affinity and specificity, which are screened from synthetic peptide libraries through in vitro screening techniques (such as SELEX technology). These peptide chains can precisely bind and interact with specific target molecules, such as proteins, small molecules, cell surface receptors or viruses. The synthesis of peptide aptamers is usually carried out by solid-phase peptide synthesis, and can be chemically modified as needed to enhance their stability, affinity and selectivity. Compared with traditional antibodies, peptide aptamers have unique advantages in terms of small molecular weight, simple synthesis and low immunogenicity.

Advantages of peptide aptamers: ① It has the characteristics of high stability, low immunogenicity, high affinity and high tissue permeability; ② It has the characteristics of simple structure and no difference between different synthesis batches; ③ It has low cost and low dependence on animal immunity; ④ It can preferentially remove hydrophobic amino acids to maintain higher hydrophilicity.

Peptide Aptamer Screening

The selection of peptide aptamer screening methods depends on the subsequent experimental use of the peptide aptamer, which can be divided into in vivo non-display systems, in vitro display systems, and emerging molecular docking simulation methods based on bioinformatics.

① Yeast two-hybrid technology

The yeast two-hybrid technology is used to study protein interactions in vivo. The principle is to fuse protein X with the DNA binding domain (BD) of the transcription factor and the candidate peptide with the transcription activation domain (AD) of the transcription factor. BD and AD alone cannot activate transcription, and only when the two are combined can transcription be activated. If the X protein binds to the candidate peptide, transcription is activated, and gene expression can be monitored by colorimetric enzyme assay or growth selection method.

This technology is simple to operate and has a wide range of applicability. It can be used for large-scale short peptide screening. However, this technology has certain limitations: it is only applicable to targets with larger molecular weight (membrane proteins cannot be studied), it is prone to false positives, and the screening time is long.

With the development of technology, the Y2H system has been integrated with next-generation sequencing (NGS) to create the Y2H-seq assay method, which only requires one-step PCR to comprehensively identify interacting proteins, significantly improving experimental efficiency.

② Phage display technology

The principle of phage display technology is to fuse the exogenous DNA fragment encoding the peptide with the protein encoding gene on the surface of the phage.

This technology can preserve the activity of the peptide aptamer throughout the screening process, and the competitive environment promotes the improvement of the affinity of the screened peptide aptamer. However, when dealing with small molecule targets on the solid phase, time-consuming reverse screening is required.

③ Molecular docking technology

Molecular docking is a computer simulation technology that aims to predict the binding mode between receptors and ligands, including docking position, docking size, and binding affinity. Through this technology, researchers can simulate the interaction between different molecules to infer their binding mode and stability. With the help of bioinformatics, molecular docking can be widely used in the design and screening of peptide aptamers. By analyzing the surface of the receptor molecule and combining the peptide sequence in the peptide library, molecular docking can efficiently predict the optimal peptide-receptor binding site and binding mode. This technology can not only accelerate the discovery process of peptide aptamers, but also provide a theoretical basis for the optimization and functional modification of peptide aptamers, and improve the effect of targeted drug delivery and precision treatment. With the advancement of computing technology, the application of molecular docking in peptide aptamer research will become more accurate and efficient.

Application of Peptide Aptamers

Peptide aptamers are increasingly widely used in the medical field, especially in disease treatment, targeted drug delivery and early diagnosis, showing great potential. As a molecule with high specificity and affinity, peptide aptamers can accurately identify and bind to disease-related target molecules, especially in cancer treatment, showing unique advantages.

In the field of cancer treatment, peptide aptamers can be used as biological probes to target cancer cells. Through in vitro screening techniques (such as SELEX), researchers can screen out peptide aptamers with high affinity from a large number of peptide libraries. These aptamers can specifically recognize specific receptors or antigens on the surface of cancer cells, thereby achieving precise positioning of tumors. This targeting ability makes peptide aptamers an important tool for tumor diagnosis and targeted therapy, which can deliver drugs or therapeutic molecules directly to cancer cells, greatly improving the treatment effect and reducing side effects on healthy tissues.

In the treatment of livestock and poultry diseases, combined with computer bioinformatics methods, researchers have successfully designed a new peptide aptamer for precise targeting of specific pathogens or infected cells. By recognizing and binding to antigens on the surface of pathogens, peptide aptamers can effectively inhibit the spread of viruses or bacteria, improve the immune efficacy of vaccines, and even be used as antibody substitutes to treat infectious diseases. In this application, the advantages of peptide aptamers are that they are simple to synthesize, have a short production cycle, and are low in cost, so they can quickly respond to different pathogen challenges and provide more efficient treatment options.

In breast cancer research, the conjugation of peptide aptamers with chemotherapy drugs has gradually become a promising treatment strategy. As a targeted chemotherapy sensitizer, peptide aptamer-drug conjugates (ADCs) can accurately deliver chemotherapy drugs to cancer cells, causing the drugs to accumulate at the tumor site, and increase the local concentration of drugs through peptide aptamers that specifically bind to cancer cell surface receptors. This targeted chemotherapy strategy not only enhances the efficacy of chemotherapy drugs, but also reduces the toxicity of drugs in normal cells, significantly improving patients' survival rate and quality of life.

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