Responsive hybrid block co-polymer conjugates of proteins–controlled architecture to modulate substrate specificity and solution behaviour

Abstract

Responsive co-polymers based on polyethyleneglycol methacrylate (PEGMA) monomers have been grown by aqueous phase ATRP from a model protein, trypsin, to generate hybrid polymer-protein block conjugates. The conjugates (Hybrids I and II) both contained the same segment of grafted responsive co-polymer to afford a phase transition at 37 °C, Hybrid II however differed from Hybrid I by having a second block of hydrophilic pPEGMA monomer grown from the end of the responsive block. The resultant ‘diblock’ and ‘triblock’ hybrids were characterised in terms of their temperature-dependent behaviour in solution by dynamic light scattering, small-angle neutron scattering and pulsed-gradient spin-echo NMR, and their structures at surfaces examined by aqueous phase atomic force microscopy and cryo transmission electron microscopy. These data showed that Hybrids I and II differed in their solution behaviour with temperature, dependent on the arrangement of their grafted polymer blocks. Hybrid I self-assembled into higher-order structures above 37 °C before precipitating reversibly, whereas Hybrid II remained essentially constant in size across a similar temperature range even when its attached intermediate polymer block underwent a phase transition. The differences in polymer-protein hybrid behaviour were also manifest in enzyme activity assays with temperature-dependent hydrolysis of both peptide and protein substrates varying with hybrid architecture. Overall the data show that it is possible to grow responsive polymer-protein block co-polymers of varied structures, architectures and solution behaviour and that these can be used to control bioconjugate activity

Direct Peptide Bioconjugation/PEGylation at Tyrosine with Linear and Branched Polymeric Diazonium Salts

“…Conjugating polymers with this structure have emerged in recent years as key macromolecular intermediates for the preparation of polymer-(poly)peptide conjugates [20][21][22][23][24] and others. [25][26][27][28] In this study a relatively low molecular weight comb polymer was prepared, in order to facilitate the purification and characterization of the peptide conjugates. Conjugation to Tyrosine-containing peptides.…”

Polymer Directed Protein Assemblies

“…One of the earlier approaches was performed on Bovine Serum Albumin (BSA), which was reduced to have more reactive cysteine-groups exposed and was subsequently functionalized with a radical initiator used in ATRP-reactions and polymers were grown in a controlled fashion [11]. This led to many sequential studies on how to design other protein-multiple polymer systems as well as investigating their behavior with respect to remaining catalytic activity and also directed self-assembly [58]. One such directed assembly is towards interfaces, which is facilitated by the polymer that surrounds the protein structure.…”

Stimuli-Responsive Polymers and Their Applications in Nanomedicine

“…When the temperature increased above the PNiPAAm lower critical solution temperature (LCST), the PNiPAAm-BSA bioconjugates formed stable nanoparticles composed of dehydrated polymer and hydrophilic protein. As an alternative to this systems, protein-polymer conjugates are based on biocompatible polyethyleneglycol methacrylate (PEGMA) [160]. Hybrid polymer-protein (PEGMA-trypsin) conjugates are promising candidates for biomedical applications.…”