A Brief Introduction to Peptide Conjugation

Although peptides are viewed as highly selective ligands with high-affinity for a wide range of disease targets, it’s still a fairly challenging task to suitably derivatize and apply them for both diagnostic and therapeutic purposes. Bioconjugation, a chemical strategy to form a stable covalent link between two molecules (of which at least one is a biomolecule), is often used in the hope of achieving the best results in not only academic research but also clinical diagnostics as well as the production of therapeutics. In fact, peptides are an important type of molecules for to be derived by bioconjugation. So far, tremendous efforts have been invested to find suitable locations for modification and facile peptide conjugation chemistries so that binding affinity can be maintained or enhanced.

In bioconjugate chemistry, the molecules to be conjugated have been the subject of intensive studies over the years. Except for diversified peptide-protein conjugates, there are many other types of conjugation, such as:

• Fluorophore Conjugation
• Biotinylation
• Horseradish Peroxidase (HRP) Conjugation
• Gold/Silver Nanoparticles Conjugation
• Magnetic Beads Conjugation

In this article, we are going to explore two kinds of conjugates, namely, peptide drug bioconjugations and silver nanoparticles conjugation, to see how they are applied and what their therapeutic effects are.

Peptide Drug Bioconjugations

Over the last few decades, targeted therapy has gained unprecedented focus from the research circle as the drawbacks of traditional treatment techniques such as chemotherapy or radiotherapy began to manifest. Scientists start to search for new therapies that have stronger efficacy yet with fewer side effects. Against this backdrop, peptide drug conjugate made its debut and swiftly holds a promising stance in the arena of targeted cancer therapy. Its distinct advantage lies in the improvement of therapeutic potential of drugs and the enabling of direct delivery of therapeutic agents, without bring harms to the surrounding cells.

In brief, the peptide-protein bioconjugation is a useful tool to improve the performance of biotech drugs and some drugs using this technique have turned out to be great success. To cite an example here, the covalent conjugation of poly(ethylene glycol) (PEG) chains to proteins, also known as PEGylation, has been successfully developed as a means of varying the in vivo properties of protein drugs. With this technique, great benefits such as less frequent administration to patients, improved efficacy and greater convenience are all achieved. As a hydrophilic, biocompatible polymer, PEG has been approved by FDA, the main regulatory agencies for parenteral administration. This is definitely a great news.

However, despite the remarkable success talked above, there are still some drawbacks with protein drugs with regard to their manipulation, storage and delivery. Probably the biggest reason is that proteins are highly structured and fragile macromolecules, which can easily undergo physical, chemical and enzymatic denaturation, degradation and inactivation. This presents a major challenge as to how to preserve their structural conformations so as to achieve the ultimate goal of maintaining their activity.

Silver Nanoparticles Conjugation

Except for the peptide-protein conjugation, peptides can also be conjugated to silver nanoparticles.

With the prevalence and advance of nanotechnology, nanoparticles have found wider and potential applications in the fields of medicine, cosmetics, energy, biomedicine and environment.

Significantly different from the larger matter, nanoparticles are particles between 1 and 100 nanometres (nm) in diameters with a surrounding interfacial layer contains 20-15000 atoms. Because of their exceptional characteristics, nanoparticles have gained increasing attention during the last decade. And among all the nanoparticles, silver nanoparticles (AgNPs) have gained particular interest from technologists and scientists due to their unique biological and physico-chemical properties.

In a century where peptides have seen a renaissance, it is a great idea to take advantage of both AgNPs and peptides and conjugate these two entities. This powerful technique-Silver Nanoparticles Conjugation

• has opened the doors for a new revolution. Nanoparticles through various scientific research also find potential applications in other areas like physics, optics, and electronics. For instance, nanoparticles can be used to deliver a cargo, such as an anticancer drug, or a cohort of radionuclide atoms to a targeted region of the body, such as a tumor.

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