As a leading drug conjugation service provider, BOC Sciences is committed to offering hapten small molecule conjugation services. With advanced equipment and professional expertise, we provide comprehensive solutions for hapten-carrier conjugates.
Haptens are small molecular compounds with a molecular weight below 1000 Da that cannot be effectively recognized by the immune system to induce an antibody response, such as toxins, hormones, pharmaceuticals, and pesticides. However, haptens can be chemically modified at specific sites by attaching active group-bearing linkers, and then they can be combined with carriers to create hapten-carrier conjugates, also known as artificial antigens. These conjugates can indirectly induce the proliferation and differentiation of B cells, resulting in the production of specific antibodies by utilizing T cell epitopes.
The preparation of hapten-carrier conjugates with good immunogenicity is the most critical step in establishing immunoassay methods for small molecular compounds. Immunoassays are sensitive analytical methods based on the specific recognition and reversible binding reactions between antigens and antibodies and have found extensive applications in biological analysis. Immunoassays for detecting small molecules mainly refer to indirect competitive enzyme-linked immunosorbent assay (IC-ELISA). For instance, in the case of small molecular toxin haptens, they are conjugated to carrier proteins, inducing an immune response in animals, and then tested using IC-ELISA.
Fig. 1 Hapten protein conjugate used for IC-ELISA1
BOC Sciences provides one-stop services for hapten-carrier conjugates, including synthesis, characterization, and commercial production. We offer comprehensive support to various clients in the field of drug development.
Proteins are commonly used carriers to induce a strong immune response. Hydrophilic carriers like bovine serum albumin, with its large reactive groups, stable properties, and solubility in aqueous or some organic solvents, are often used.
When small molecule targeted drugs are not effective treatment options, immunotherapy can be used as an alternative strategy. Since small molecules are not inherently immunogenic, hapten conjugate vaccines are used to produce antibodies against these small molecule haptens, such as several abused drugs like morphine haptens and cocaine haptens.
Hapten-labeled nucleotides can be used to prepare DNA probes, such as fluorescence in situ hybridization (FISH) probe.
Commonly used hapten- carrier conjugates are:
Hapten coupling can be achieved through various reactions, utilizing either an existing functional group or an added reactive group. Among the available coupling methods, a commonly employed procedure is the induction of amide bond formation using carbodiimides, which were initially applied to peptide synthesis. Water-soluble carbodiimides facilitate the formation of protein-hapten conjugate formation in aqueous solvents and have been extensively used for synthesizing immunogenic conjugates and to a limited extent, enzyme conjugates. The effectiveness of water-soluble carbodiimides is constrained due to the limited solubility of some haptens in aqueous solutions. Additionally, the formation of the intermediate products like O-acylisourea derivative and N-acylurea side products, which are typically less soluble than the parent molecule. Similarly, the mixed anhydride method, using an alkylchlorocarbonate reagent, can also result in conjugation of the alkylcarbonate component, that like stable acylisourea derivatives, may act as unintended haptens. Isocyanides were developed as promising reagents for the immobilization of biological molecules without compromising their activity. Researchers have adapted and modified these reactions to provide an alternative to carbodiimides in peptide synthesis. Isocyanides with tertiary amino groups, such as 2-morpholinoethylisocyanide (MEI), in the presence of a suitable additive such as N-hydroxysuccinimide (NHS), promoted peptide synthesis in high yield. Scientists previously adapted the MEI peptide synthesis procedures to prepare hapten conjugates including those associated with zeatin and benzimidazole derivatives.
Fig. 2 Haptens conjugated to proteins using 2-morpholinoethylisocyanide
Haptens have multiple potential modification sites. Different hapten modifications result in differences in antibody affinity, specificity, and efficacy. We synthesize various modified haptens based on different sites and choose the one that maintains the most complete hapten structure when connecting to the carrier for high affinity and strong specificity antibody production. Alternatively, we can select modifications that do not preserve the complete structure of the hapten molecule for establishing highly sensitive IC-ELISA.
The linker should avoid attaching near functional groups of the target hapten and its length should be appropriate, allowing the immune system to recognize the characteristic structure of the hapten.
It involve using coupling agents to link haptens to carriers at functional groups like -COOH, -NH2, or -SH. We select appropriate conjugation methods based on the specific hapten being used. Additionally, we have the capability to control the molar ratio of hapten to carrier.
Carrier systems allow haptens to activate the immune system and generate antibodies. BOC Sciences can provide custom hapten-carrier conjugation services, selecting appropriate carrier systems to meet your needs.
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