PEGylated biomolecules

Characterization and control of biological macromolecules requires a variety of analytical tools for detection of chemical and structural modifications. Attachment of a PEG moiety to the biomolecule results in an additional layer of complexity and often requires a unique set of analytical tools to ensure quality and control. In developing PEGylated biomolecules, three key attributes must be controlled to achieve the desired product PEG reagent quality, PEGylation chemistry and stability of the PEG moiety post conjugation. Each of these is described in detail in the following sections. 

Bass, L., Strategy for Evaluation of Analytical Comparability of PEGylated Biomolecules, presented at International Association for Biologicals State of the Art Analytical Methods for the Characterization of Biological Products and Assessment of Comparability, NIH, Bethesda, Maryland, June 2006. 

PEGylation chemistry deals primarily with the chemical reactivity and specificity of the activated functional group on the PEG molecule in relationship with the targeted site(s) on the biomolecules of interest. Additionally, the size (molecular weight) and configuration (linear, branched, etc.) of the polymer as well as of the biomolecule will also affect the PEGylation reaction. 

The term bioconjugate covers combinations of biomolecules, for example, antibody-enzyme conjugates, and biomolecules linked to synthetic molecules like PEGylated proteins. 

In the first generation of PEGylated drugs, the attachment of PEG was usually achieved with a functional group that is reactive toward the hydroxyl end groups of PEG, which were typically anhydrides, acid chlorides, chlorofor-mates, or carbonates [38]. In the second generation, more efficient groups like aldehydes, esters, and amides are reacted with the biomolecule to achieve... 

The intranasal route delivery is an easy non-invasive approach to deliver biomolecules via the olfactory and trigeminal neuronal pathways to the brain, bypassing the BBB. It is considered to be the fastest and most effective way to cross the BBB to reach the CNS. Malhotra et al. developed TAT- and MGF-tagged PEGylated chitosan nanoparticles to deliver siRNA to the brain via an intranasal route. The results demonstrated maximum siRNA delivery to the brain compared with other tissues, with no cellular toxic effects. 

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