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The transition from linear to highly branched poly(β-amino ester)s: Branching matters for gene delivery.

ABSTRACT: Nonviral gene therapy holds great promise but has not delivered treatments for clinical application to date. Lack of safe and efficient gene delivery vectors is the major hurdle. Among nonviral gene delivery vectors, poly(β-amino ester)s are one of the most versatile candidates because of their wide monomer availability, high polymer flexibility, and superior gene transfection performance both in vitro and in vivo. However, to date, all research has been focused on vectors with a linear structure. A well-accepted view is that dendritic or branched polymers have greater potential as gene delivery vectors because of their three-dimensional structure and multiple terminal groups. Nevertheless, to date, the synthesis of dendritic or branched polymers has been proven to be a well-known challenge. We report the design and synthesis of highly branched poly(β-amino ester)s (HPAEs) via a one-pot "A2 + B3 + C2"-type Michael addition approach and evaluate their potential as gene delivery vectors. We find that the branched structure can significantly enhance the transfection efficiency of poly(β-amino ester)s: Up to an 8521-fold enhancement in transfection efficiency was observed across 12 cell types ranging from cell lines, primary cells, to stem cells, over their corresponding linear poly(β-amino ester)s (LPAEs) and the commercial transfection reagents polyethyleneimine, SuperFect, and Lipofectamine 2000. Moreover, we further demonstrate that HPAEs can correct genetic defects in vivo using a recessive dystrophic epidermolysis bullosa graft mouse model. Our findings prove that the A2 + B3 + C2 approach is highly generalizable and flexible for the design and synthesis of HPAEs, which cannot be achieved by the conventional polymerization approach; HPAEs are more efficient vectors in gene transfection than the corresponding LPAEs. This provides valuable insight into the development and applications of nonviral gene delivery and demonstrates great prospect for their translation to a clinical environment.

SUBMITTER: Zhou D

PROVIDER: S-EPMC4928911 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Recently, biomaterials have been designed to contain redox-sensitive moieties, such as thiols and disulfides, to impart responsive degradation and/or controlled release. However, due to the high sensitivity of cellular redox-based systems which maintain free-radical homeostasis (e.g. glutathione/glutathione disulfide), if these biomaterials modify the cellular redox environment, they may inadvertently affect cellular compatibility and/or oxidative stress defenses. In this work, we hypothesize that the degradation products of a poly(β-amino ester) (PBAE) hydrogel formed with redox sensitive disulfide (cystamine) crosslinking could serve as a supplement to the environmental cellular antioxidant defenses. Upon introduction into a reducing environment, these disulfide-containing hydrogels cleave to present bound-thiol groups, yet remain in the bulk form at up to 66 mol% cystamine of the total amines. By controlling the molar fraction of cystamine, it was apparent that the thiol content varied human umbilical vein endothelial cell (HUVEC) viability IC50 values across an order of magnitude. Further, upon introduction of an enzymatic oxidative stress generator to the cell culture (HX/XO), pre-incubated thiolated hydrogel degradation products conferred cellular and mitochondrial protection from acute oxidative stress, whereas non-reduced disulfide-containing degradation products offered no protection. This polymer may be an advantageous implantable drug delivery system for use in acute oxidative stress prophylaxis and/or chronic oxidative stress cell therapies due to its solid/liquid reversibility in a redox environment, controlled thiolation, high loading capacity through covalent drug-addition, and simple post-synthesis modification which bound-thiols introduce. STATEMENT OF SIGNIFICANCE:In this work, we demonstrate a unique property of disulfide containing degradable biomaterials. By changing the redox state of the degradation products (from oxidized to reduced), it is possible to increase the IC50 of the material by an order of magnitude. This dramatic shift is linked directly to the oxidative stress response of the cells and suggests a possible mechanism by which one can tune the cellular response to degradable biomaterials.

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The transition from linear to highly branched poly(β-amino ester)s: Branching matters for gene delivery.

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