A photo-degradable gene delivery system for enhanced nuclear gene transcription

Abstract

There currently exists a significant gap in our understanding of how the detailed chemical characteristics of polycation gene carriers influence their delivery performances in overcoming an important cellular-level transport barrier, i.e., intranuclear gene transcription. In this study, a UV-degradable gene carrier material (ENE4-1) was synthesized by crosslinking low molecular weight branched polyethylenimine (bPEI-2k) molecules using UV-cleavable o-nitrobenzyl urethane (NBU) as the linker molecule. NBU degrades upon exposure to mild UV irradiation. Therefore, this UV-degradable carrier allows us to control the chemical characteristics of the polymer/DNA complex (polyplex) particles at desired locations within the intracellular environment. By using this photolytic DNA carrier, we found that the exact timing of the UV degradation significantly influences the gene transfection efficiencies of ENE4-1/DNA(pGL2) polyplexes in HeLa cells. Interestingly, even if the polyplexes were UV-degraded at different intracellular locations/times, their nuclear entry efficiency was not influenced by the location/timing of UV degradation. The UV treatment did not influence the size or binding strength of the polyplexes. However, we confirmed that the degradation of the carrier molecules impacts the chemical characteristics of the polyplexes (it produces carbamic acid and nitrosobenzyl aldehyde groups on ENE4-1). We believe that these anionic acid groups enhance the interaction of the polyplexes with nuclear transcription proteins and thus the final gene expression levels; this effect was found to occur, even though UV irradiation itself has a general effect of reducing transfection efficiencies. Excess (uncomplexed) ENE4-1 polymers appear to not play any role in the UV-enhanced gene transcription phenomenon.

Photo‐responsive amphiphilic poly(α‐hydroxy acids) with pendent o‐nitrobenzyl ester constructed via copper‐catalyzed azide‐alkyne cycloaddition reaction

“…[11] Thereafter, different strategies for the construction of photo-responsive polymers with o-NB esters in the main chain as well as in the side chain are developed. [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] However, there have been limited reports on the synthesis of biocompatible and biodegradable polymers with pendent o-NB esters group. Almutairi reported the synthesis of a polycaprolactone with pendent o-NB ester group, and demonstrated the light-controlled depolymerization of the polymers.…”

Catch and release: photocleavable cationic diblock copolymers as a potential platform for nucleic acid delivery

“…For example, two groups have complexed pDNA into polyplexes by using PEI modified with o -NB–containing crosslinkers. 41, 42 In one case, polyplexes were formed and pDNA was subsequently caged within the polyplexes by methacrylamide crosslinking, 41 whereas in the other case, PEI was first crosslinked with o -NB urethane linkers and then used to form polyplexes. 42 In these examples, the crosslinkers in the polyplexes could be degraded to yield low molecular weight PEI via irradiation with UV light.…”

“…41, 42 In one case, polyplexes were formed and pDNA was subsequently caged within the polyplexes by methacrylamide crosslinking, 41 whereas in the other case, PEI was first crosslinked with o -NB urethane linkers and then used to form polyplexes. 42 In these examples, the crosslinkers in the polyplexes could be degraded to yield low molecular weight PEI via irradiation with UV light. Transfection by the crosslinked polyplexes was limited in the absence of UV light but became detectable in a portion of cells at levels similar to those induced by standard PEI (e.g.…”

“…41, 42 These systems relied on o -NB-based crosslinkers, and retained relatively high molecular weight polycations (∼2 kDa) even after irradiation with UV light. In contrast, mPEG- b -P(APNBMA•HCl) 7.9 undergoes a charge reversal after irradiation with UV light, which could account for the release and migration of pDNA in our system.…”

Cervical Cancer Gene Therapy by Gene Loaded PEG-PLA Nanomedicine

“…Several general strategies have been developed to achieve this end, including liposomes (Chen et al, 2010;Buyens et al, 2011), polymers (Elzoghby 2013;Lee et al, 2014), and molecular conjugates (Elfinger et al, 2007;Geiger et al, 2010). As a research focus in recent years, polyethylene glycol-polylactic acid (PEG-PLA) block copolymer and its end-group derivative nanoparticles can enhance the drug loading of hydrophobic drugs, reduce the burst effect, avoid being engulfed by phagocytes, increase the circulation time of drugs in blood, and improve bioavailability (Xiao et al, 2010).…”