Development of pH-responsive dynaplexes based on dynamic polymer for effective survivin siRNA delivery Yun Liu 1, 2 , Sangeun Lee 1, 2 , Brigitta Loretz 1 , Anna K. H. Hirsch 1,2 , Claus-Michael Lehr 1,2 1 Helmholtz Institute for Pharmaceutical Research Saarland (HIPS) – Helmholtz Centre for Infection Research (HZI), Campus E 8.1, 66123 Saarbrücken, Germany 2 Department of Pharmacy, Saarland University, 66123, Saarbrücken, Germany Gene therapies targeting “undruggable” genetic diseases have shown great promise and underscore the importance of nucleic acid delivery systems. However, existing nucleic acid delivery systems require further optimization to overcome certain drawbacks such as stability, off-target effects, etc 1 . To address these challenges, we have developed a series of biodynamic polymers (biodynamers, BDs) based on the reversible acylhydrazone bonds and imine bonds, which exhibit pH-dependent degradability and dynamic behavior under acidic environments 2 . The excellent biocompatibility, easy tunability, and dynamic polymerization under acidic environments of BDs make them effective siRNA transfection agents. In this study, we prepared dynamic nanocomplexes (dynaplexes, DPs, hydrodynamic diameter = 100 nm) between biodynamer and siRNA through electrostatic interactions. The optimized DPs showed stable colloidal stability in size in the presence of serum (10% FCS) after crosslinking (XL) and they performed significant pH-dependent size change (from 200 to 1200 nm for 6 h) and polymer degradability (50% degradation for 24 h at pH 5.0), as well as siRNA release (100% for 6 h at pH 5.0). The high cell viability (80%-100%, determined by MTT and LDH assay after 24 h incubation) and excellent cellular uptake (greater than 90% of total cells after 6 h incubation) of XL-DPs effectively supported the intracellular delivery of siRNA. Survivin siRNA-loaded XL-DPs showed potent knockdown of survivin mRNA and resulted in significant apoptosis of lung carcinoma epithelial cells (A549 cells) which is 2.2 times higher than Lipofectamine 2000 (a commercial transfection agent). In conclusion, XL-DPs showed promising potential for siRNA delivery and can be considered strong candidates for the next generation of transfection agents 3 . References 1. S. Lee, S. Nasr, S. Rasheed, Y. Liu, …, A. K. H. Hirsch, C.-M. Lehr. Proteoid biodynamers for safe mRNA transfection via pH-responsive nanorods enabling endosomal escape, J Control Release. 2023; 353: 915–29. 2. J. F. Folmer-Andersen, E. Buhler, S.-J.Candau, S. Joulie, M. Schmutz, J.-M Lehn. Cooperative, bottom-up generation of rigid-rod nanostructures through dynamic polymer chemistry. Polym. Int. 2010, 59 (11), 1477–1491. DOI: 10.1002/pi.2864. 3. Y. Liu, S. Ashmawy, L.Latta, A.-V. Weiss, A.F.Kiefer, B. Loretz, A. K. H. Hirsch, S. Lee, C.M. Lehr. pH-Responsive Dynaplexes as pontent Inductors of Apoptosis by Intracellular Delivery of Survivin-siRNA, Biomacromolecules. (In submission)
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