Visualization of the Degradation of a Disulfide Polymer, Linear Poly(ethylenimine sulfide), for Gene Delivery

Abstract

Polyethylenimine (PEI) shows high transfection efficiency and cytoxicity due to its high amine density. The new disulfide cationic polymer, linear poly(ethylenimine sulfide) (l-PEIS), was synthesized for efficient and safe gene delivery. As the amine density of l-PEIS increased, the transfection efficiency also increased. l-PEIS-6 and l-PEIS-8 show transfection efficiencies that are similar to that of PEI. However, cytotoxicity of l-PEIS was not observed due to the biodegradable disulfide bond. The disulfide bonds are stable in the oxidative extracellular condition and can be degraded rapidly in the reductive intracellular condition. The degradation of l-PEIS in HeLa cells was visualized by fluorescence microscopy using the probe-probe dequenching effect of BODIPY-FL fluorescence dye. l-PEIS was degraded completely within 3 h.

Gene therapy progress and prospects: synthetic polymer-based systems

“…22 The different redox potential between the oxidizing extracellular and reducing intracellular environment has been exploited for polymer biodegradation. 17,[23][24][25][26] Disulfide bonds are stable in the circulation, but are cleaved upon entry into the reductive intracellular environment, thus allowing site specific degradation.…”

“…23 Intracellular degradation was demonstrated using fluorescence quenching of conjugated BODIPY-dye. Similarly, disulfide cross-linked low-molecular weight linear PEI displayed outstandingly high transfection efficacy.…”

“…Sequence-defined polymers allow detailed structure-activity relationship studies For better defined copolymer structures and libraries with defined molecular weight and topology, [21][22][23]28 meaningful structure-transfection correlations are Gene therapy progress and prospects D Schaffert and E Wagner possible. However, more detailed studies are not possible, even with such systems, due to the limited design space and/or their polydispersity.…”

Poly(ethylene glycol) with Observable Shedding

“…Further conjugation with SPDP leads to the formation of (4), which shows a distinct absorption peak at 280 nm, originating from the 2-pyridyldithio group of the SPDP molecule (see supporting materials). The final reaction between (4) and (9) forms product (10) through the replacement of 2-pyridyldithio by the thiol group in (9). The spectrum of (10) reveals an additional peak at 490 nm, which is consistent with the absorption wavelength of OG488.…”

“…However, if the PEG chain is shed due to disulfide cleavage, intramolecular quenching is abolished and increased fluorescence can be measured. [9] Notably, our design preserves a reactive amine group in the FRET-bearing PEG molecule, which allows for conjugation to different NP systems. In this study, we choose to conjugate the FRET-bearing PEG molecule with poly(lactic-co-glycolic acid) (PLGA) to form PLGA-(FRET)-PEG NPs as a model polymeric NP platform.…”