Biotin, also known as vitamin H and coenzyme R, belongs to the vitamin B family (B7) and is a water-soluble vitamin. As a coenzyme of carboxylase, biotin participates in the production of fatty acids, valine, isoleucine, and gluconeogenesis. It also participates in many major metabolic activities of the body to promote cell regeneration and health. Its molecular structure is shown in Figure 1. It is a combination of a lipophilic heterocyclic ring and a hydrophilic carboxylic acid chain. Studies have shown that the esterophilic heterocycle of biotin can specifically bind to avidin, and the carboxyl group on the hydrophilic carboxylic acid chain can react with many groups with very strong binding ability. Based on the above principles, it can label nucleotides, chemicals, proteins, monoclonal antibodies, and peptides, and can also be used as a targeting ligand to couple with other materials.
Biotin labeled compound
In 2010, Guochun Zhou’s research group synthesized a biotin-labeled derivative of fumagillin as shown in Figure 2. It was formed by connecting fumagillin derivatives and biotin through amide bond and carbamate bond with octanediamine as the linking arm. The biotin marker can selectively inhibit the proliferation of human umbilical vein endothelial cells (HUVEC). In vitro receptor binding experiments proved that its possible target is human methionine aminopeptidase-2 (MetAP2). Yin Hang’s team also used biotin-labeled compounds to study the pharmacological activity of the opioid drug morphine, and the results showed that it can target TLR4 to mediate a series of immune responses
Biotin-labeled protein
In order to evaluate the potency of the reaction between biotin and the human immunoglobulin lgG heavy chain to be labeled, Wang et al. reacted biotin with human immunoglobulin lgG heavy chain in various ratios, and then reacted with microsphere particles connected with anti-human immunoglobulin IgG heavy chain antibody, and then the relevant instrument was used to determine the reaction result. In the solution of human immunoglobulin lgG heavy chain, slowly added 100 μL of the prepared biotin DMSO solution, and reacted the human immunoglobulin IgG heavy chain with biotin at room temperature for 1 h, and then used Sephadex G column for purification. When the ratio of biotin to human immunoglobulin IgG heavy chain was 1:4, the average fluorescence intensity (MFI value) on the microsphere particles was the strongest.
Biotin-labeled the monoclonal antibody
Pang Qiuxia and others used a monoclonal antibody to cross-link with biotin to prepare a biotinylated monoclonal antibody Biotin-1A2E1. The biological activity of Biotin-1A2E1 was detected by competitive inhibition ELISA and immunocytochemistry. The prepared biotinylated antibody had high activity, good sensitivity for detecting AIB1 protein in breast cancer cells, and provided a powerful means for detecting AIBI protein in tumor-assisted diagnosis.
Biotin-labeled the peptide
Yan Hong et al. used biotin labeling to verify the interaction between the two binding peptides and the full-length MD-2. The sulfo-SBED complex had the following four characteristics: can react with specific amino acid sequences, non-specific photoreactivity, disulfide bonds that can be cleaved by thiols, and can bind to biotin. The biotin labeling transfer method was to use the characteristics of Sulfo-SBED. The researchers used NHS activated esters to first bind a protein to Sulfo-SBED, making it a “bait protein”, and incubated the “bait” protein with the “prey” protein to be analyzed under dark conditions. After the two were combined, they were irradiated with 300-350nm ultraviolet light to activate the azidobenzene of Sulfo-SBED to form a covalent connection between the “bait” protein and the “prey” protein. At this time, after the disulfide bond was cleaved by thiol, the biotin label can be transferred from the “bait” protein to the “prey” protein, and finally the two are separated by the Western Blot method. By detecting the streptavidin-coupled horseradish peroxidase on the protein, it can be determined whether the “bait” protein had captured the “prey” protein to be analyzed. The results confirmed that there are two binding polypeptides that bind to the full-length MD-2 protein.
Research on Biotin as a Targeting Ligand
As a kind of targeting ligand, biotin has many advantages. First, biotin has a simple chemical structure and low molecular weight. Moreover, in many tumor cells, the overexpression of biotin receptor is often higher than that of other receptors, such as folate receptor. Therefore, biotin also has a higher tumor specificity. In recent years, the research on biotin as a targeting ligand has received more and more attention. Ji Hyun Kim et al. grafted biotin to cholesteric methoxy polyethylene glycol-graft-poly(β-amino acid ester) to prepare Biotin-PAE-g-PEG-ch, which was loaded with the anti-cancer drug doxorubicin (DOX) to prepare DOX-Biotin-PAE-g-PEG-ch nanomicelles. After co-incubation with MCF-7 cells, the fluorescence density tracking experiment found that the prepared drug carrier has a higher affinity for tumor cells.
Through a lot of research, it can be found that biotin is used as a targeting ligand to modify the surface of polysaccharide molecules, and the obtained product material used to load anti-cancer drugs not only can accurately deliver the anti-cancer drugs to the tumor site, but also had a good inhibitory effect on tumor cells. However, studies have found that after biotin is modified on the surface of the carrier, some properties of the product carrier will be partially changed due to the presence of biotin, such as hydrophilic and hydrophobic properties, particle size, surface charge, etc. Therefore, after the carrier material is modified with biotin, sufficient testing and research should be conducted on the synthesized product to investigate the partial performance changes of the product, so as to provide theoretical basis and guidance for the subsequent product to load anti-cancer drugs.
References
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