In Vitro Evaluation of Anti-Aggregation and Degradation Behavior of PEGylated Polymeric Nanogels under In Vivo Like Conditions

The in vivo stability and biodegradability of nanocarriers crucially determine therapeutic efficacy as well as safety when used for drug delivery. This study aims to evaluate optimized in vitro techniques predictive for in vivo nanocarrier behavior. Polymeric biodegradable nanogels based on hydroxyethyl methacrylamide-oligoglycolates-derivatized poly(hydroxyethyl methacrylamide-co-N-(2-azidoethyl)methacrylamide) and with various degrees of PEGylation and crosslinking densities are prepared. Three techniques are chosen and refined for specific in vitro evaluation of the nanocarrier performance: (1) fluorescence single particle tracking (fSPT) to study the stability of nanogels in human plasma, (2) tangential flow filtration (TFF) to study the degradation and filtration of nanogel degradation products, and (3) fluorescence fluctuation spectroscopy (FFS) to evaluate and compare the degradation behavior of nanogels in buffer and plasma. fSPT results demonstrate that nanogels with highest PEGylation content show the least aggregation. The TFF results reveal that nanogels with higher crosslink density have slower degradation and removal by filtration. FFS results indicate a similar degradation behavior in human plasma as compared to that in phosphate buffered saline. In conclusion, three methods can be used to compare and select the optimal nanogel composition, and these methods hold potential to predict the in vivo performance of nanocarriers

Post-PEGylated and crosslinked polymeric ssRNA nanocomplexes as adjuvants targeting lymph nodes with increased cytolytic T cell inducing properties

Potent adjuvants are highly demanded for most protein and peptides based vaccine candidates in clinical development. Recognition of viral single stranded (ss)RNA by innate toll-like receptors 7/8 in dendritic cells results in a cytokine environment supportive to the establishment of long lasting antibody responses and Th1 oriented T cell immunity. To fully exploit the immunestimulatory properties of ssRNA, it needs to be adequately formulated to ensure its optimal delivery to dendritic cells in the vaccine draining lymph nodes. In the present paper, we report on the design of ssRNA nanocomplexes formed by complexation of the cationic poly(carbonic acid 2-dimethylamino-ethyl ester 1-methyl-2-(2-methacryloylamino)-ethyl ester) (pHPMA-DMAE) based polymeric carrier and ssRNA. The resulting ssRNA nanocomplexes were subsequently PEGylated through copper-free click chemistry using PEG-bicyclo[6.1.0]nonyne (PEG-BCN) and cross-linked via disulfide bonds to increase their stability. The obtained near-neutral charged PEGylated ssRNA nanocomplexes (~150 nm) combined ssRNA protection with highly efficient delivery of ssRNA to DCs in the vaccine draining lymph nodes after subcutanuously administration. When co-administrated with a model antigen (soluble ovalbumin (OVA)), ssRNA nanocomplexes were far more efficient at inducing CD8 cytolytic T cells when compared to OVA co-adminstarted with naked ssRNA. Furthermore, IgG2c antibody titers, indicative of Th1 skewed T cell responses, were >10 times increased by complexing ssRNA into the PEGylated nanocomplexes. This study highlights the potential of post-functionalizing ssRNA nanocomplexes by copper-free click chemistry and these findings indcate that this potent ssRNA adjuvant may profoundly improve the efficacy of a variety of vaccines requiring Th1-type immunity

Targeted decationized polyplexes for siRNA delivery

The applicability of small interfering RNA (siRNA) in future therapies depends on the availability of safe and efficient carrier systems. Ideally, siRNA delivery requires a system that is stable in the circulation but upon specific uptake into target cells can rapidly release its cargo into the cytoplasm. Previously, we evaluated a novel generation of carrier systems ("decationized" polyplexes) for DNA delivery, and it was shown that folate targeted decationized polyplexes had an excellent safety profile and showed intracellular triggered release upon cell specific uptake. Targeted decationized polyplexes consist of a core of disulfide cross-linked poly(hydroxypropyl methacrylamide) (pHPMA) stably entrapping nucleic acids and a shell of poly(ethylene glycol) (PEG) decorated with folate molecules. In the present study, the applicability of folate targeted decationized polyplexes for siRNA delivery was investigated. This required optimization of the carrier system particularly regarding the cross-linking density of the core of the polyplexes. Stable and nanosized siRNA decationized polyplexes were successfully prepared by optimizing the cross-link density of their core. Upon incubation in human plasma, a significant portion of siRNA remained entrapped in the decationized polyplexes as determined by fluorescence correlation spectroscopy (FCS). When tested in a folate receptor overexpressing cell line stably expressing luciferase, Skov3-luc, sequence specific gene silencing was observed. As expected, neither interference on the intrinsic luciferase expression nor on the cell metabolic activity (determined by XTT) was induced by the free-polymer or the siRNA polyplexes. In conclusion, targeted decationized polyplexes are safe and stable carriers that interact with the targeted cells and rapidly disassemble upon cell entry making them promising siRNA delivery systems

PEGylated and functionalized aliphatic polycarbonate polyplex nanoparticles for intravenous administration of HDAC5 siRNA in cancer therapy

Guanidine and morpholine functionalized aliphatic polycarbonate polymers are able to efficiently deliver histone deacetylase 5 (HDAC5) siRNA into the cytoplasm of cancer cells in vitro leading to a decrease of cell proliferation were previously developed. To allow these biodegradable and biocompatible polyplex nanoparticles to overcome the extracellular barriers and be effective in vivo after an intravenous injection, polyethylene glycol chains (PEG750 or PEG2000) were grafted on the polymer structure. These nanoparticles, showed an average size of about 150 nm and a slightly positive zeta potential with complete siRNA complexation. Behavior of PEGylated and non-PEGylated polyplexes were investigated in the presence of serum, in terms of siRNA complexation (Fluorescence Correlation Spectroscopy), size (Dynamic Light Scattering and Single-Particle Tracking), interaction with proteins (Isothermal Titration Calorimetry) and cellular uptake. Surprisingly, both PEGylated and non-PEGylated formulations presented relatively good behavior in the presence of fetal bovine serum (FBS). Hemocompatibility tests showed no effect of these polyplexes on hemolysis and coagulation. In vivo biodistribution in mice was performed and showed a better siRNA accumulation at the tumor site for PEGylated polyplexes. However, cellular uptake in protein-rich conditions showed that PEGylated polyplex lost their ability to interact with biological membranes and enter into cells, showing the importance to perform in vitro investigations in physiological conditions closed to in vivo situation. In vitro, the efficiency of PEGylated nanoparticles decreases compared to non-PEGylated particles, leading to the loss of the antiproliferative effect on cancer cells

Targeted Decationized Polyplexes for siRNA Delivery

The applicability of small interfering RNA (siRNA) in future therapies depends on the availability of safe and efficient carrier systems. Ideally, siRNA delivery requires a system that is stable in the circulation but upon specific uptake into target cells can rapidly release its cargo into the cytoplasm. Previously, we evaluated a novel generation of carrier systems (“decationized” polyplexes) for DNA delivery, and it was shown that folate targeted decationized polyplexes had an excellent safety profile and showed intracellular triggered release upon cell specific uptake. Targeted decationized polyplexes consist of a core of disulfide cross-linked poly­(hydroxypropyl methacrylamide) (pHPMA) stably entrapping nucleic acids and a shell of poly­(ethylene glycol) (PEG) decorated with folate molecules. In the present study, the applicability of folate targeted decationized polyplexes for siRNA delivery was investigated. This required optimization of the carrier system particularly regarding the cross-linking density of the core of the polyplexes. Stable and nanosized siRNA decationized polyplexes were successfully prepared by optimizing the cross-link density of their core. Upon incubation in human plasma, a significant portion of siRNA remained entrapped in the decationized polyplexes as determined by fluorescence correlation spectroscopy (FCS). When tested in a folate receptor overexpressing cell line stably expressing luciferase, Skov3-luc, sequence specific gene silencing was observed. As expected, neither interference on the intrinsic luciferase expression nor on the cell metabolic activity (determined by XTT) was induced by the free-polymer or the siRNA polyplexes. In conclusion, targeted decationized polyplexes are safe and stable carriers that interact with the targeted cells and rapidly disassemble upon cell entry making them promising siRNA delivery systems