A systematic study of cationic polymer brush-nucleic acid complexes Carlos Eduardo Neri-Cruz 1 , Franciane Teixeira 1,2 , Lan Chang 1 , Shoghik Hakobyan 1 , Julien E. Gautrot 1 1 School of Engineering and Materials Science, Queen Mary University of London, UK, 2 Department of Immunology, Institute of Biomedical Sciences, University of Sao Paulo, Brazil Upon administration of therapeutic nucleic acids (NA), normally associated with delivery vectors, enzymes and a vast pool of molecules, along with the hostile conditions prevailing at physiological barriers contribute to the destabilisation of vector-NA complexes, leading to loss of therapeutic functionality and clearance from the body 1 . Such interactions are collectively known as the vector interactome and are influenced by the physicochemical properties of the vector 2 . From a design point-of-view, strategies to modulate the vector interactome include the use of chemistries and architectures with unique affinity to the NA of interest, enabling robust and enduring binding, as well as sort of physical shielding and non-fouling capacity to limit destabilisation by competitive binding and molecular crowding 2,3 . Cationic polymer brushes generated by SI-RDRP approaches represent attractive tools for systematically designing vectors and studying their interactome, owing to their narrow MW and ability to exquisitely control their architecture (thickness, grafting density, and hierarchical structure) 4 . In this work, the kinetics for the binding of short and large RNA/DNA molecules to PDMAEMA and PMETAI brushes was systematically studied via SPR. Our data reveals that absorption of NA relies on the interplay between brush-NA chemical affinity, accessibility of binding sites defined by the brush architecture, and steric hindrance imposed by size-type of NA. Short RNAs were better absorbed by highly dense polymer brushes compared to large mRNA/pDNA of inherent restricted bulk-volume 5 . Low mass absorption of short-dsDNA was not only found for PDMAEMA 5 but for PMETAI. In both cases, the affinity was surprisingly equivalent, providing evidence of non-favoured DNA structural conformation. Despite strongest polyelectrolyte profile of PMETAI, mass absorption of short-NA was significantly higher for PDMAEMA. However,for instance dsRNA-PDMAEMA complex was chemically weaker compared to complexation with PMETAI, suggesting that while permanent- charged PMETAI chains led to stronger binding, only a limited number of molecules were captured due to the more constrained chain-conformation, thus, hampering absorption. Indeed, hampering in the absorption of ssRNA (oflower molecular weight) was decreased. Hydrogen bonding capacity could have contributed to enhanced absorption inPDMAEMA. No difference on mass absorption and affinity ofmRNA/pDNA within both systems was observed, implying that chain accessibility guides absorption of large NA. References 1. R. Kumar, C. F. Santa Chalarca, M. R. Bockman, C. V. Bruggen, C. J. Grimme, R. J. Dalal, M. G. Hanson, J. K. Hexum and T. M. Reineke, Chem Rev , 2021, 121 , 11527-11652. 2. A. A. M. Raynold, D. Li, L. Chang and J. E. Gautrot, Nat Commun , 2021, 12 , 6445.J. E. Gautrot, L. Chang, C. Alexis, P. Gutfreund and A. Zarbakhsh, Advanced Materials Interfaces , 2022, 9 D. Li, A. S. Sharili, J. Connelly and J. E. Gautrot, Biomacromolecules , 2018, 19 , 606-615. 3. F. Qu, D. Li, X. Ma, F. Chen and J. E. Gautrot, Biomacromolecules , 2019, 20 , 2218-2229.
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