Salt-Induced Stability and Serum-Resistance of Polyglutamate Polyelectrolyte Brushes/Nuclear Factor-κB p65 siRNA Polyplex Enhance the Apoptosis and Efficacy of Doxorubicin

Abstract

Short interfering RNAs (siRNAs) as chemotherapeutic RNAi agents hold great promise for a significant improvement in cancer therapy. Despite the promise, effective transport of siRNA with minimal side effects remains a challenge. The common problem associated with the low delivery efficiencies of current polycation-based gene delivery systems is their low stability in the presence of salt and serum. In the present study we developed the polyglutamate derivatives (PGS) polyelectrolyte brushes for NF-κB p65 siRNA delivery. The PGS polyelectrolyte brushes/siRNA polyplex was colloidally stable (150 nm diameter) in physiological saline (150 mM NaCl), likely due to the osmotic brushes of PGS. The size-controlled siRNA/PGS polyplex also showed the serum resistance resulting in their efficient cellular uptake was not negatively influenced by the presence of serum. The endothermic profile of ITC, their low values of Gibbs free energy and binding constants Kb under salt conditions provided the direct evidence that PGS polyelectrolyte brushes had a much lower binding affinity for serum proteins, compared with PEI 25KDa. PGS polyelectrolyte brushes delivering NF-κB p65 siRNA achieved efficient down-regulation of NF-κB p65 protein in HeLa cells. The NF-κB p65 down-regulation mediated by PGS polyelectrolyte brushes was more significant than PEI 25KDa and comparable to Lipofectamine 2000. Furthermore, the combination treatment with PGS polyelectrolyte brushes/NF-κB p65 siRNA polyplex and doxorubicin demonstrated synergistic apoptotic and cytotoxic effects on HeLa cancer cells. The high stability in physiological saline and salt-induced serum resistance of PGS polyelectrolyte brushes/siRNA polyplex has potential applications together with standard chemotherapies such as doxorubicin to be a viable method to improve the clinical outcomes in cancer therapies.

The polyion complex nano-prodrug of doxorubicin (DOX) with poly(lactic acid-co-malic acid)-block-polyethylene glycol: preparation and drug controlled release

“…Polyelectrolyte complex (PEC) nanoparticles have attracted more attentions due to their wide merits as drug carriers, and they are suitable for loading some charged drug molecules such as DNA and proteins with high loading efficiencies. The drug releases can be controlled by pH and ionic strength (Li et al, 2011;Zhao et al, 2013;Tang et al, 2003;Teng et al, 2013;Rajkumar et al, 2013).…”

Light‐Mediated Activation of siRNA Release in Diblock Copolymer Assemblies for Controlled Gene Silencing

“…In contrast, Zhao et al reported siRNA/PEI (25 kDa) polyplexes greater than 1 µm in diameter following a 1 h incubation in physiological saline (150 mM NaCl). [25] In the presented studies, all polyplexes retained small sizes that were below the 200 nm threshold for endocytic uptake. [26] Based on the relative stability of the polyplex structures and the minimal increase in D H , these studies suggested that the PEG block formed a protective corona following polyplex formation to resist both salt-induced aggregation and protein adsorption.…”

“…mPEG-b-P(APNBMA) 23.6 provided enhanced siRNA binding, to form salt-stable copolymer-based polyplexes that resisted aggregation following incubation in PBS, as compared to substantial growth for siRNA/PEI polyplexes (to > 1 µm in diameter). [25] Serum exposure of siRNA/mPEG-b-P(APNBMA) 23.6 polyplexes indicated tight association, in contrast to poly(L-lysine)-based polyplexes that showed > 90% siRNA dissociation following 1 h of serum incubation. [5b] Delivery of mPEG-b-P(APNBMA) 23.6 polyplexes to NIH/3T3 cells facilitated > 80% cellular uptake compared to 40% for Lipofectamine lipoplexes, and cytoplasmic release of siRNAcontaining polyplexes within 3 h of polyplex exposure.…”

Nanocarriers with tunable surface properties to unblock bottlenecks in systemic drug and gene delivery

“…Once taken up by the cells, cationic nanocarriers are able to destabilize and escape from the endosomal membrane by the proton-sponge and umbrella effects, and then they can release nucleic acids into the cytoplasm [36]. Although cationic nanocarriers promote cellular uptake in intracellular environments, the experience accumulated over the last years has revealed some important limitations, especially regarding instability due to interactions with extracellular matrix proteins and complement proteins in blood plasma [37], that exacerbate, soothe, or mask the effects of the delivered nucleic acids [38,39].…”