Effect of molecular weights of polyethyleneimine on the polyplex formation with calf thymus DNA

Glatiramer acetate enhances tumor retention and innate activation of immunostimulants

Cancer immunotherapy aims to stimulate immune cells to recognize and attack tumor tissue. The immunostimulatory polyanions polyI:C and CpG induce potent pro-inflammatory immune responses as TLR3 and TLR9 agonists, respectively. Clinical trials of TLR agonists, however, have been fraught with immune-related adverse events, even when injecting intratumorally in an effort to minimize systemic exposure. We identified Glatiramer Acetate (GA), a positively-charged polypeptide approved for multiple sclerosis, as a delivery agent capable of complexing with polyI:C or CpG and reducing the mobility of these actives. Small nanoparticles termed polyplexes form when mixing positively-charged GA and negatively-charged immunostimulant (polyI:C or CpG). The ratio of GA to immunostimulant directly affected the potency of TLR activation and the mobility of these actives in simulated tumor tissue. Polyplexes of GA and CpG were injected intratumorally in a tumor model of head and neck cancer (HNC) and significantly mitigated tumor growth as compared to the vehicle controls. Intratumoral injections of CpG showed the slowest tumor growth but exhibited dramatically higher systemic proinflammatory cytokine levels compared to polyplexes of GA with CpG. Sequencing of RNA from resected tumors revealed a similar pattern of upregulated proinflammatory cytokines for CpG and polyplexes, a finding supported by histological tumor staining showing similar infiltration of immune cells induced by these treatments. Intratumoral administration of polyplexes of GA with immunostimulant represents a translational approach to enhance local immune responses while mitigating systemic immune-related adverse events.

Properties of polyplexes formed through interaction between hydrophobically-modified poly(ethylene imine)s and calf thymus DNA in aqueous solution

Polycationic polymers and DNA form soluble complexes in aqueous solution, which allows the transfer of genetic material into cells. Therefore, these chemically-modified polymers are of interest for use in studies aimed at better transfection efficiency and gene expression along with reduced cytotoxicity. In this study, branched poly(ethylene imine) (PEI) was modified by alkylation with n-alkyl groups (n = 4, 6, 8 and 12 carbons). The polyplexes formed through interaction of the modified PEIs and calf thymus DNA (ctDNA) were investigated using UV-Vis spectrophotometry, ethidium bromide fluorescence emission, circular dichroism spectroscopy, dynamic light scattering, and small-angle X-ray scattering techniques along with the determination of the zeta potential and viscosity. According to the results obtained, the formation of ctDNA-PEI polyplexes occurs in three steps. Firstly, when a small amount of polyelectrolyte is present the ctDNA chains are partially compacted. Subsequently, with the addition of more polyelectrolyte, the complexes have a null charge density and micrometric size. Lastly, with a higher concentration of PEI, the ctDNA is fully compacted by the PEI chains, leading to positively charged complexes with R_h values in the range of 52.0-86.0 nm. The viscosity and SAXS analysis suggested that the unmodified PEI exhibits the strongest interaction and promotes the best ctDNA condensation.

Fluorescent active ruthenium(ii) complex units containing bpy or phen or dmp ligands anchored on branched poly(ethylenimine): DNA binding and in vitro biological assessment

UV light irradiation visible responses of polymer ruthenium complexes.