Functional properties and biodistribution of poly(triethylenetetramine/cystamine bisacrylamide) and poly(triethylenetetramine/cystamine bisacrylamide)- poly(ethylene glycol) mixtures formed with nucleic acid

Abstract

The clinical success of non-viral gene delivery reagents is hampered by their inefficient cellular transgene delivery, which is largely influenced by carrier properties that are currently undefined and misunderstood. In an attempt to further define and understand the requirements for a safe and efficient non-viral gene delivery reagent, research labs often engineer and evaluate many putative products with subtle physiochemical differences in order to delineate requirements for improved in vitro and in vivo success. The synthesis of many putative reagents is often time-intensive, laborious and costly. In a previous manuscript published by our lab, different amounts of poly(triethylenetetramine/cystamine bisacrylamide) (p(TETA/CBA) and its pegylated counterpart, poly(triethylenetetramine/cystamine bisacrylamide)- poly(ethylene glycol) (p(TETA/CBA)-g-PEG) were mixed together to easily identify optimal reagent properties and candidates in vitro, while avoiding the synthesis of many putative candidates for study. This report uses the aforementioned facile approach to evaluate reagent properties of products that were obtained via one-pot synthesis, which improved synthetic ease. As such, synthesis time was reduced from 6 days to 3 days and had comparable or improved transfection and viability compared to previous works. Moreover, this synthesis resulted in higher molecular weight products than were used in the previous study and allow for lower polymer doses to be used for complexation, which is useful for systemic delivery that is used herein. The physiochemical properties of the formulations derived using these novel reagents was studied prior to investigating their in vivo biodistribution profiles in a murine colon adenocarcinoma model. Interestingly, negatively charged complexes exhibited greater passive tumor accumulation compared to positively charged complexes following their systemic administration. These studies warrant further investigation for the use of negatively charged drug and gene delivery reagents for passive tumor targeting, and they substantiate the use of polycation/PEG-polycation mixtures for facile product evaluation in order to elucidate design and formulation mandates for the clinical success of non-viral gene delivery formulations.

Bioreducible Polycations in Nucleic Acid Delivery: Past, Present, and Future Trends

“…These findings were also confirmed for disulfide‐crosslinked PEI polyplexes . Several recent biodistribution studies demonstrated the ability of bioreducible PAA to deliver nucleic acids to tumors . Improved transfection activity of bioreducible polyplexes was demonstrated by the Wagner lab.…”

Polymeric delivery of therapeutic RAE-1 plasmid to the pancreatic islets for the prevention of type 1 diabetes

“…Typically, once a bioreducible polymer is opsonized and removed from the bloodstream, it is sequestered and concentrated heavily in the liver and spleen. To increase the stability of the gene carrier, the addition of PEGylation can push biodistribution toward the spleen [28–30]. Results from this study show the biodistribution profile of targeting polymer Eph-PEG-p(CBA-DAH) with a high degree of pancreas accumulation compared to the other major organs, as can be seen in Fig.…”

Bioreducible polymers for therapeutic gene delivery

“…In a biodistribution study following systemic administration in a murine adenocarcinoma model, the 25% p(TETA/CBA/PEG)/p(TETA/CBA) complexes at the w/w of 3:1 with the lowest particle size and surface charge indicated predominantly higher liver deposition and lower spleen accumulation. This suggests relatively low interaction of these complexes with serum proteins, which results in evasion of the retiuloendothelial system (lower accumulation in spleen), and extravasation through liver endothelial fenestrae due to relatively small particle sizes [25]. …”