Redox-Active Polymer Microcapsules for the Delivery of a Survivin-Specific siRNA in Prostate Cancer Cells

Abstract

In this report, we describe the delivery of small interfering RNA (siRNA) using LbL-assembled microcapsules. The microcapsules are based on negatively charged poly(methacrylic acid) nanometer thin films containing cross-linking disulfide bonds. One system is polycation-free and another contains polylysine for siRNA complexation in the microcapsule void. When microcapsules containing a siRNA targeting survivin were delivered to PC-3 prostate cancer cells, a significant inhibition of the expression of the antiapoptotic protein was observed. However, down-regulation of survivin was also observed in PC-3 cells exposed to microcapsules embedded with a scrambled siRNA as well as in cells treated with empty microcapsules. These findings indicate a capsule-dependent off-target effect, which is supported by a reduction in the expression of other survivin-unrelated proteins. The microcapsules and their polymeric constituents do not affect cell proliferation, as determined by a metabolic assay, even after 4 days of exposure. In addition, in PC-3 cells exposed to microcapsules, we observed a marked accumulation of LC3b, a marker related to autophagy (i.e., self-digestion), a degradation pathway involved in the maintenance of cell homeostasis in response to different stresses. This evidence suggests that empty microcapsules can induce a perturbation of the intracellular environment, which causes the activation of a cell safeguard mechanism that may limit the therapeutic effect of the microcapsules in tumor cells.

The effect of nanoparticle uptake on cellular behavior: disrupting or enabling functions?

“…On the other side, one can recall, independently of the presence of cargo, that a detrimental effect of some polymeric NPs on cancer cells favors their autophagy as stress cell response, thus remaining metabolically active. 102 Finally, one last consideration should be reserved for the importance of cooperation among several competencies to analyze the various aspects of NP-cell/tissue interaction, including material science, surface chemistry, physics, mathematical modeling, biochemistry, molecular biology, pharmacology, cellular physiology, and integrated function physiology.…”

Fluorescent Dyes Used in Polymer Carriers as Imaging Agents in Anticancer Therapy

“…Such capsules sensitive to external conditions e.g., magnetic field should contain magnetic particles [281] or they have special receptor molecules like antibodies (Ab) attached to the outer side of the shell [282]. The Ab can be adsorb by electrostatic interactions [283] or covalently liked to surfaces [284][285][286][287][288]. For uncharged materials like poly(ethylene glycol) (PEG) or poly(N-vinylpyrrolidone) (PVPON) covalent attachment of the Ab is required since electrostatic attachment is not effective for lowfouling materials because they inhibit nonspecific protein binding.…”

“…The pre-condensation of pDNA with peptides improves lipid-based delivery systems and transfection efficiencies [326]. At last, by using LbL method Caruso et al [284][285][286][287][288] synthesized redoxactive polymeric microcapsules with the cross-linked shell containing disulfide bonds for the delivery of a siRNA targeting to PC-3 prostate cancer cells. The polycation-polylysine (PLL) for a siRNA complexation was infiltrated into the pores of nanoporous silica particles prior to an assembly of layer from the negatively charged poly(methacrylic acid) with thiol-modified groups (PMASH).…”

“…The complexation of siRNA inside the cavity of microcapsules prevents it from leaking, thus the PLL/siRNA polyplex covered with the multilayer film was shielded from the direct effects of a milieu. The PLL-siRNA complexes can be released when disulfide bonds in the membrane are broken by pore-forming GSH, then the PLL can be enzymatically degraded within cells into the amino acid lysine [288]. According with the LbL method the similar redox capsules were prepared but aminefunctionalized silica particles as templates were used for coating by alternately assembled the PMASH layer and poly(vinylpyrrolidone) (PVPON).…”

“…The disulfide bridge was produced by oxidation thiols using chloramine T and after cores removal (with HF) the film was washed into a neutral pH solution, in which the PVPON was released. In this way microcapsules were filled with an uncomplexed siRNA [288]. In addition, Jin et al [327] reported magnetically vectored nanocapsules based on polystyrene seeds with incorporated Fe 3 O 4 surrounded by porous SiO 2 shells.…”