In Situ Gelling Liquid Crystalline System as Local siRNA Delivery System.

An effective short interfering RNA (siRNA) delivery system protects the siRNA from degradation, facilitates its cellular uptake, and promotes its release into the cytoplasm. Local administration of siRNA presents advantages over systemic administration, such as the possibility to use lower doses and allow local and sustained release. In this context, in situ solidifying organogels based on monoglycerides (MO), polyethylenimine (PEI), propylene glycol (PG) and tris buffer are an attractive strategy for intratumoral delivery of siRNA. In this study, precursor fluid formulation (PFF) composed of MO/PEI/PG/tris buffer at 7.85:0.65:76.5:15 (w/w/w/w) was used to deliver siRNA to tumor cells. The internal structure of the gel obtained from PFF was characterized using small angle X-ray scattering (SAXS). In addition, its ability to complex siRNA, protect it from degradation, and functionally deliver it to tumor cells was investigated. Moreover, in vivo gel formation following intratumoral injection was evaluated. The gel formed in excess water from PFF was found to comprise a mixture of hexagonal and cubic phases. The system was able to complex high amounts of siRNA, protect it from degradation, promote siRNA internalization, and induce gene silencing in vitro in a variety of tumor cell lines. Moreover, a gel formed in situ following intratumoral injection in a murine xenograft model. In conclusion, PFF is a potential delivery system for local and sustained delivery of siRNA to tumor tissue after intratumoral administration.

Delivery of modified mRNA to damaged myocardium by systemic administration of lipid nanoparticles.

Lipid Nanoparticles (LNPs) are a promising drug delivery vehicle for clinical siRNA delivery. Modified mRNA (modRNA) has recently gained great attention as a therapeutic molecule in cardiac regeneration. However, for mRNA to be functional, it must first reach the diseased myocardium, enter the target cell, escape from the endosomal compartment into the cytosol and be translated into a functional protein. However, it is unknown if LNPs can effectively deliver mRNA, which is much larger than siRNA, to the ischemic myocardium. Here, we evaluated the ability of LNPs to deliver mRNA to the myocardium upon ischemia-reperfusion injury functionally. By exploring the bio-distribution of fluorescently labeled LNPs, we observed that, upon reperfusion, LNPs accumulated in the infarct area of the heart. Subsequently, the functional delivery of modRNA was evaluated by the administration of firefly luciferase encoding modRNA. Concomitantly, a significant increase in firefly luciferase expression was observed in the heart upon myocardial reperfusion when compared to sham-operated animals. To characterize the targeted cells within the myocardium, we injected LNPs loaded with Cre modRNA into Cre-reporter mice. Upon LNP infusion, Tdtomato+ cells, derived from Cre mediated recombination, were observed in the infarct region as well as the epicardial layer upon LNP infusion. Within the infarct area, most targeted cells were cardiac fibroblasts but also some cardiomyocytes and macrophages were found. Although the expression levels were low compared to LNP-modRNA delivery into the liver, our data show the ability of LNPs to functionally deliver modRNA therapeutics to the damaged myocardium, which holds great promise for modRNA-based cardiac therapies.

Extracellular vesicles derived from Plasmodium-infected and non-infected red blood cells as targeted drug delivery vehicles.

Among several factors behind drug resistance evolution in malaria is the challenge of administering overall doses that are not toxic for the patient but that, locally, are sufficiently high to rapidly kill the parasites. Thus, a crucial antimalarial strategy is the development of drug delivery systems capable of targeting antimalarial compounds to Plasmodium with high specificity. In the present study, extracellular vesicles (EVs) have been evaluated as a drug delivery system for the treatment of malaria. EVs derived from naive red blood cells (RBCs) and from Plasmodium falciparum-infected RBCs (pRBCs) were isolated by ultrafiltration followed by size exclusion chromatography. Lipidomic characterization showed that there were no significant qualitative differences between the lipidomic profiles of pRBC-derived EVs (pRBC-EVs) and RBC-derived EVs (RBC-EVs). Both EVs were taken up by RBCs and pRBCs, although pRBC-EVs were more efficiently internalized than RBC-EVs, which suggested their potential use as drug delivery vehicles for these cells. When loaded into pRBC-EVs, the antimalarial drugs atovaquone and tafenoquine inhibited in vitro P. falciparum growth more efficiently than their free drug counterparts, indicating that pRBC-EVs can potentially increase the efficacy of several small hydrophobic drugs used for the treatment of malaria.

Dendritic Cell Targeting mRNA Lipopolyplexes Combine Strong Antitumor T-Cell Immunity with Improved Inflammatory Safety.

In vitro transcribed mRNA constitutes a versatile platform to encode antigens and to evoke CD8 T-cell responses. Systemic delivery of mRNA packaged into cationic liposomes (lipoplexes) has proven particularly powerful in achieving effective antitumor immunity in animal models. Yet, T-cell responses to mRNA lipoplexes critically depend on the induction of type I interferons (IFN), potent pro-inflammatory cytokines, which inflict dose-limiting toxicities. Here, we explored an advanced hybrid lipid polymer shell mRNA nanoparticle (lipopolyplex) endowed with a trimannose sugar tree as an alternative delivery vehicle for systemic mRNA vaccination. Like mRNA lipoplexes, mRNA lipopolyplexes were extremely effective in conferring antitumor T-cell immunity upon systemic administration. Conversely to mRNA lipoplexes, mRNA lipopolyplexes did not rely on type I IFN for effective T-cell immunity. This differential mode of action of mRNA lipopolyplexes enabled the incorporation of N1 methyl pseudouridine nucleoside modified mRNA to reduce inflammatory responses without hampering T-cell immunity. This feature was attributed to mRNA lipopolyplexes, as the incorporation of thus modified mRNA into lipoplexes resulted in strongly weakened T-cell immunity. Taken together, we have identified lipopolyplexes containing N1 methyl pseudouridine nucleoside modified mRNA as potent yet low-inflammatory alternatives to the mRNA lipoplexes currently explored in early phase clinical trials.

Liposomal prednisolone inhibits tumor growth in a spontaneous mouse mammary carcinoma model.

Cancers are abundantly infiltrated by inflammatory cells that are modulated by tumor cells to secrete mediators fostering tumor cell survival and proliferation. Therefore, agents that interfere with inflammatory signaling molecules or specific immune cell populations have been investigated as anticancer drugs. Corticosteroids are highly potent anti-inflammatory drugs, whose activity is intensified when targeted by nanocarrier systems. Liposome-targeted corticosteroids have been shown to inhibit tumor growth in different syngeneic murine tumor models as well as human xenograft mouse models, which is attributed to a switch in the tumor microenvironment from a pro-inflammatory to an anti-inflammatory state. Despite the recognized value of implantation tumor models in preclinical research, the "acute" inflammation induced by inoculation of tumor cells together with the exponential tumor growth in a relatively short period of time does not resemble slow progressive human disease that develops in situ. Therefore, in this study, the antitumor effect of liposomal corticosteroids was investigated in a clinically more relevant setting of transgenic mice developing spontaneous breast carcinomas. Here we show that liposomal prednisolone phosphate inhibits the growth of spontaneous breast carcinoma. Interestingly, the liposomal prednisolone was significantly more active than free drug. At 72h after injection of the liposomal formulation, 3µg prednisolone per gram of tumor tissue was recovered whereas no drug could be recovered after injection of the free agent. This indicates that, despite etiological and morphological differences between implanted and spontaneous tumor models, EPR-mediated accumulation of drug occurs to similar extent in this spontaneous mammary carcinoma model as in the syngeneic tumor models. Finally, we analyzed miRNA profiles in the MMTV/neu model and showed that the top 10 of miRNAs in the MMTV/neu tumor consisted of miRNAs with a known involvement in breast carcinoma proliferation and metastasis. The only exception was the appearance of miR-146b, a known inflammation-regulating miRNA species, after liposomal prednisolone treatment.

An in situ gelling liquid crystalline system based on monoglycerides and polyethylenimine for local delivery of siRNAs.

The development of delivery systems able to complex and release siRNA into the cytosol is essential for therapeutic use of siRNA. Among the delivery systems, local delivery has advantages over systemic administration. In this study, we developed and characterized non-viral carriers to deliver siRNA locally, based on polyethylenimine (PEI) as gene carrier, and a self-assembling drug delivery system that forms a gel in situ. Liquid crystalline formulations composed of monoglycerides (MO), PEI, propylene glycol (PG) and 0.1M Tris buffer pH 6.5 were developed and characterized by polarized light microscopy, Small Angle X-ray Scattering (SAXS), for their ability to form inverted type liquid crystalline phases (LC2) in contact with excess water, water absorption capacity, ability to complex with siRNA and siRNA release. In addition, gel formation in vivo was determined by subcutaneous injection of the formulations in mice. In water excess, precursor fluid formulations rapidly transformed into a viscous liquid crystalline phase. The presence of PEI influences the liquid crystalline structure of the LC2 formed and was crucial for complexing siRNA. The siRNA was released from the crystalline phase complexed with PEI. The release rate was dependent on the rate of water uptake. The formulation containing MO/PEI/PG/Tris buffer at 7.85:0.65:76.5:15 (w/w/w/w) complexed with 10 µM of siRNA, characterized as a mixture of cubic phase (diamond-type) and inverted hexagonal phase (after contact with excess water), showed sustained release for 7 days in vitro. In mice, in situ gel formation occurred after subcutaneous injection of the formulations, and the gels were degraded in 30 days. Initially a mild inflammatory process occurred in the tissue surrounding the gel; but after 14 days the tissue appeared normal. Taken together, this work demonstrates the rational development of an in situ gelling formulation for local release of siRNA.

Exosome mimetics: a novel class of drug delivery systems.

The identification of extracellular phospholipid vesicles as conveyors of cellular information has created excitement in the field of drug delivery. Biological therapeutics, including short interfering RNA and recombinant proteins, are prone to degradation, have limited ability to cross biological membranes, and may elicit immune responses. Therefore, delivery systems for such drugs are under intensive investigation. Exploiting extracellular vesicles as carriers for biological therapeutics is a promising strategy to overcome these issues and to achieve efficient delivery to the cytosol of target cells. Exosomes are a well studied class of extracellular vesicles known to carry proteins and nucleic acids, making them especially suitable for such strategies. However, the considerable complexity and the related high chance of off-target effects of these carriers are major barriers for translation to the clinic. Given that it is well possible that not all components of exosomes are required for their proper functioning, an alternative strategy would be to mimic these vesicles synthetically. By assembly of liposomes harboring only crucial components of natural exosomes, functional exosome mimetics may be created. The low complexity and use of well characterized components strongly increase the pharmaceutical acceptability of such systems. However, exosomal components that would be required for the assembly of functional exosome mimetics remain to be identified. This review provides insights into the composition and functional properties of exosomes, and focuses on components which could be used to enhance the drug delivery properties of exosome mimetics.

Biodistribution of polymer hydrogel capsules for the delivery of therapeutics.

A key phase in the development of intelligently designed nanoparticle delivery vehicles for new therapeutic agents is to gain an understanding of their interaction with tissues and cells. We report a series of in vitro and in vivo experiments aimed at tracking a potential delivery vehicle for therapeutic agents, including vaccine peptides and drugs derived from poly(methacrylic acid) hydrogel capsules in certain organs and cell types. For the in vitro studies, two immortal liver-derived cell lines (Huh7 and Hepa1-6) and primary cultures of mouse hepatocytes were incubated with Alexa 647 labelled fluorescent capsules to track their internalization and intracellular distribution by confocal microscopy. Capsules, 500nm in diameter, were taken up into the cells in a time-dependent manner in all three cell lines. Capsules were observed in plasma membrane-derived vesicles within the cells. After 24h a significant proportion of the capsules was observed in lysosomes. To understand the behaviour of the capsules in vivo, Alexa 488 labelled fluorescent capsules were intravenously injected into Sprague-Dawley rats and after 24h the fate of the capsules in a number of organs was determined by flow cytometry and confocal microscopy. By flow cytometry, the majority of the capsules were detected in the spleen whilst similar numbers were found in the lung and liver. By confocal microscopy, the majority of the capsules were found in the liver and spleen with significantly less capsules in the lung, heart and kidney. Colocalization of capsules with cell-type specific markers indicated that in lung, heart and kidney, the majority of the capsules were located in endothelial cells. In the spleen ~50% of the capsules were found in CD163-positive cells, whereas in the liver, almost all capsules were located in CD163-positive cells, indicating uptake by Kupffer cells. Electron microscopy confirmed the presence of capsules within Kupffer cells.