GNeosomes: Highly Lysosomotropic Nanoassemblies for Lysosomal Delivery

Liposomal formulations for treating lysosomal storage disorders

Lysosomal storage disorders (LSD) are a group of rare life-threatening diseases caused by a lysosomal dysfunction, usually due to the lack of a single enzyme required for the metabolism of macromolecules, which leads to a lysosomal accumulation of specific substrates, resulting in severe disease manifestations and early death. There is currently no definitive cure for LSD, and despite the approval of certain therapies, their effectiveness is limited. Therefore, an appropriate nanocarrier could help improve the efficacy of some of these therapies. Liposomes show excellent properties as drug carriers, because they can entrap active therapeutic compounds offering protection, biocompatibility, and selectivity. Here, we discuss the potential of liposomes for LSD treatment and conduct a detailed analysis of promising liposomal formulations still in the preclinical development stage from various perspectives, including treatment strategy, manufacturing, characterization, and future directions for implementing liposomal formulations for LSD.

Calixarene-decorated liposomes for intracellular cargo delivery

Amphiphilic calix[4]arenes, functionalized with guanidinium groups, are used to decorate the outer surface of liposomes and significantly improve the cellular uptake of a cargo compared to plain liposomes. The improved uptake is elicited and mediated by the interaction between the cationic polar heads of the macrocycle units embedded in the liposome bilayer and anionic heparan-sulfate proteoglycans surrounding the exterior of cells.

Guanidinoneomycin-maleimide molecular transporter: synthesis, chemistry and cellular uptake

Guanidinoglycosides are a class of non-cytotoxic molecular transporters capable of delivering high molecular weight bioactive cargos into cells at low nanomolar concentrations. Efficient bioconjugation with guanidinoglycosides has been previously demonstrated by utilizing a guanidinoneomycin decorated with a reactive but also unstable N-hydroxysuccinimmide ester-containing linker. Herein we report the synthesis, chemistry, and application of a new, stable guanidinoneomycin derivative armed with a highly specific maleimide moiety which allows for thiol-maleimide click chemistry, a highly popular bioconjugation strategy, widening the field of application of these intriguing and useful delivery vehicles.

Aminoglycosides: From Antibiotics to Building Blocks for the Synthesis and Development of Gene Delivery Vehicles

Aminoglycosides are a class of naturally occurring and semi synthetic antibiotics that have been used for a long time in fighting bacterial infections. Due to acquired antibiotic resistance and inherent toxicity, aminoglycosides have experienced a decrease in interest over time. However, in the last decade, we are seeing a renaissance of aminoglycosides thanks to a better understanding of their chemistry and mode of action, which had led to new trends of application. The purpose of this comprehensive review is to highlight one of these new fields of application: the use of aminoglycosides as building blocks for the development of liposomal and polymeric vectors for gene delivery. The design, synthetic strategies, ability to condensate the genetic material, the efficiency in transfection, and cytotoxicity as well as when available, the antibacterial activity of aminoglycoside-based cationic lipids and polymers are covered and critically analyzed.

Self-assembled DNA nanocentipedes as multivalent vehicles for enhanced delivery of CpG oligonucleotides

We report self-assembled nanocentipedes as multivalent vehicles for the delivery of immunostimulatory CpG ODNs. The multivalent vehicles could be internalized by RAW264.7 cells and stimulate the secretion of large amounts of cytokines, successively inducing effective apoptosis of cancer cells.

Guanidinylated Neomycin Conjugation Enhances Intranasal Enzyme Replacement in the Brain

Iduronidase (IDUA)-deficient mice accumulate glycosaminoglycans in cells and tissues and exhibit many of the same neuropathological symptoms of patients suffering from Mucopolysaccharidosis I. Intravenous enzyme-replacement therapy for Mucopolysaccharidosis I ameliorates glycosaminoglycan storage and many of the somatic aspects of the disease but fails to treat neurological symptoms due to poor transport across the blood-brain barrier. In this study, we examined the delivery of IDUA conjugated to guanidinoneomycin (GNeo), a molecular transporter. GNeo-IDUA and IDUA injected intravenously resulted in reduced hepatic glycosaminoglycan accumulation but had no effect in the brain due to fast clearance from the circulation. In contrast, intranasally administered GNeo-IDUA entered the brain rapidly. Repetitive intranasal treatment with GNeo-IDUA reduced glycosaminoglycan storage, lysosome size and number, and neurodegenerative astrogliosis in the olfactory bulb and primary somatosensory cortex, whereas IDUA was less effective. The enhanced efficacy of GNeo-IDUA was not the result of increased nose-to-brain delivery or enzyme stability, but rather due to more efficient uptake into neurons and astrocytes. GNeo conjugation also enhanced glycosaminoglycan clearance by intranasally delivered sulfamidase to the brain of sulfamidase-deficient mice, a model of Mucopolysaccharidosis IIIA. These findings suggest the general utility of the guanidinoglycoside-based delivery system for restoring missing lysosomal enzymes in the brain.

Cellular uptake of modified aminoglycosides

The uptake of modified amino- and guanidino-glycosides derived from kanamycin, tobramycin and neomycin in native and mutant CHO cells is examined using confocal microscopy and flow cytometry, illustrating the significance of multivalency for mammalian cell internalization of carriers that specifically interact with cell surface heparan sulfate proteoglycans.The Journal of Antibiotics advance online publication, 1 November 2017; doi:10.1038/ja.2017.131.

Delivery of Cargo to Lysosomes Using GNeosomes

Liposomes have been used to improve the intracellular delivery of a variety of cargos. Encapsulation of cargos in liposomes leads to improved plasma half-lives and minimized degradation. Here, we present a method for improving the selective delivery of liposomes to the lysosomes using a guanidinylated neomycin (GNeo) transporter. The method for synthesizing GNeo-lipids, incorporating them into liposomes, and the enhanced lysosomal delivery of encapsulated cargo are presented. GNeo-liposomes, termed GNeosomes, are capable of delivering a fluorescent dye to the lysosomes of Chinese hamster ovary cells as shown using confocal microscopy. GNeosomes can also be used to deliver therapeutic quantities of lysosomal enzymes to fibroblasts isolated from patients with a lysosomal storage disorder.

Spontaneous Vesiculation and pH-Induced Disassembly of a Lysosomotropic Detergent: Impacts on Lysosomotropism and Lysosomal Delivery

Lysosomotropic detergents (LDs) selectively rupture lysosomal membranes through mechanisms that have yet to be characterized. A consensus view, currently, holds that LDs, which are weakly basic, diffuse across cellular membranes as monomers in an uncharged state, and via protonation in the acidic lysosomal compartment, they become trapped, accumulate, and subsequently solubilize the membrane and induce lysosomal membrane permeabilization. Here we demonstrate that the lysosomotropic detergent O-methyl-serine dodecylamide hydrochloride (MSDH) spontaneously assembles into vesicles at, and above, cytosolic pH, and that the vesicles disassemble as the pH reaches 6.4 or lower. The aggregation commences at concentrations below the range of those used in cell studies. Assembly and disassembly of the vesicles was studied via dynamic light scattering, zeta potential measurements, cryo-TEM, and fluorescence correlation spectroscopy and was found to be reversible via control of the pH. Aggregation of MSDH into closed vesicles under cytosolic conditions is at variance with the commonly held view of LD behavior, and we propose that endocytotic pathways should be considered as possible routes of LD entry into lysosomes. We further demonstrate that MSDH vesicles can be loaded with fluorophores via a solution transition from low to high pH, for subsequent release when the pH is lowered again. The ability to encapsulate molecular cargo into MSDH vesicles together with its ability to disaggregate at low pH and to permeabilize the lysosomal membrane presents an intriguing possibility to use MSDH as a delivery system.

Highly Versatile Polyelectrolyte Complexes for Improving the Enzyme Replacement Therapy of Lysosomal Storage Disorders

Lysosomal storage disorders are currently treated by enzyme replacement therapy (ERT) through the direct administration of the unprotected recombinant protein to the patients. Herein we present an ionically cross-linked polyelectrolyte complex (PEC) composed of trimethyl chitosan (TMC) and α-galactosidase A (GLA), the defective enzyme in Fabry disease, with the capability of directly targeting endothelial cells by incorporating peptide ligands containing the RGD sequence. We assessed the physicochemical properties, cytotoxicity, and hemocompatibility of RGD-targeted and untargeted PECs, the uptake by endothelial cells and the intracellular activity of PECs in cell culture models of Fabry disease. Moreover, we also explored the effect of different freeze-drying procedures in the overall activity of the PECs. Our results indicate that the use of integrin-binding RGD moiety within the PEC increases their uptake and the efficacy of the GLA enzyme, while the freeze-drying allows the activity of the therapeutic protein to remain intact. Overall, these results highlight the potential of TMC-based PECs as a highly versatile and feasible drug delivery system for improving the ERT of lysosomal storage disorders.

Isothiouronium modification empowers pyrimidine-substituted curcumin analogs potent cytotoxicity and Golgi localization

Most of protein post-translational modifications occur in the Golgi and many human diseases are associated with abnormal Golgi function or improper post translational modifications of proteins in the Golgi. In this study, we designed and synthesized 4 × 6 series of novel isothiouronium-modified (E,E)-4,6-bis(styryl)-pyrimidine analogs and found that they localized at the Golgi as visualized by the intrinsic fluorescence of the analogs. The isothiouronium-modified analogs had potent cytotoxicity in both normal (Chinese Hamster Ovary or CHO) and cancer cells. Furthermore, permethylated isothiouronium-modified analogs showed cancer cell-selective cytotoxicity. The molecular mechanisms underlying Golgi localization of isothiouronium-modified compounds were investigated using 7 CHO and 4 human cancer cell lines and the results indicated that the compounds had binding partners in the Golgi. Thus, isothiouronium-modified analogs might be promising anticancer agents, novel Golgi staining reagents, and useful research tools for studying Golgi functions in normal or cancer cells and in Golgi-related human diseases.

Nonspecific Organelle-Targeting Strategy with Core-Shell Nanoparticles of Varied Lipid Components/Ratios

We report a nonspecific organelle-targeting strategy through one-step microfluidic fabrication and screening of a library of surface charge- and lipid components/ratios-varied lipid shell-polymer core nanoparticles. Different from the common strategy relying on the use of organelle-targeted moieties conjugated onto the surface of nanoparticles, here, we program the distribution of hybrid nanoparticles in lysosomes or mitochondria by tuning the lipid components/ratios in shell. Hybrid nanoparticles with 60% 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) and 20% 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) can intracellularly target mitochondria in both in vitro and in vivo models. While replacing DOPE with the same amount of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), the nanoparticles do not show mitochondrial targeting, indicating an incremental effect of cationic and fusogenic lipids on lysosomal escape which is further studied by molecular dynamics simulations. This work unveils the lipid-regulated subcellular distribution of hybrid nanoparticles in which target moieties and complex synthetic steps are avoided.

Polymyxins Facilitate Entry into Mammalian Cells

Polymyxin and guanidinylated polymyxin effectively deliver large biomolecules and liposomal assemblies into mammalian cells.

Polymyxin B is an antibiotic used against multi-resistant Gram negative infections, despite observed nephrotoxicity. Here we report the synthesis of functionalized derivatives of polymyxin B and its per-guanidinylated derivative in order to further explore the structural requirements necessary to facilitate uptake of the antibiotic into mammalian cells. We also investigate the possibility of using these novel scaffolds as molecular transporters. At nanomolar concentrations, both are capable of delivering large cargo (>300 kDa) into living cells. Their uptake depends exclusively on cell surface heparan sulfate. Mechanistic studies indicate these novel transporters are internalized through caveolae-mediated pathways and confocal microscopy show colocalization with lysosomes. The polymyxin-based transporters demonstrate cytosolic delivery through the delivery of a ribosome-inactivating protein. Furthermore, the natural polymyxin scaffold can be incorporated into liposomes and enhance their intracellular uptake. In addition to demonstrating the ability of the polymyxin scaffold to facilitate internalization into mammalian cells, these observations suggest the potential use of polymyxin and guanidinopolymyxin for intracellular delivery.

Delivery of an active lysosomal enzyme using GNeosomes

Guanidinoneomycin derivatives incorporated into liposomes were shown to improve delivery of a fluorescent dye and deliver therapeutic amounts of a lysosomal enzyme.