New Mechanism for Release of Endosomal Contents: Osmotic Lysis via Nigericin-Mediated K+/H+ Exchange

Selective targeting of chemically modified miR-34a to prostate cancer using a small molecule ligand and an endosomal escape agent

Use of tumor-suppressive microRNAs (miRNAs) as anti-cancer agents is hindered by the lack of effective delivery vehicles, entrapment of the miRNA within endocytic compartments, and rapid degradation of miRNA by nucleases. To address these issues, we developed a miRNA delivery strategy that includes (1) a targeting ligand, (2) an endosomal escape agent, nigericin and (3) a chemically modified miRNA. The delivery ligand, DUPA (2-[3-(1,3-dicarboxy propyl) ureido] pentanedioic acid), was selected based on its specificity for prostate-specific membrane antigen (PSMA), a receptor routinely upregulated in prostate cancer-one of the leading causes of cancer death among men. DUPA was conjugated to the tumor suppressive miRNA, miR-34a (DUPA-miR-34a) based on the ability of miR-34a to inhibit prostate cancer cell proliferation. To mediate endosomal escape, nigericin was incorporated into the complex, resulting in DUPA-nigericin-miR-34a. Both DUPA-miR-34a and DUPA-nigericin-miR-34a specifically bound to, and were taken up by, PSMA-expressing cells in vitro and in vivo. And while both DUPA-miR-34a and DUPA-nigericin-miR-34a downregulated miR-34a target genes, only DUPA-nigericin-miR-34a decreased cell proliferation in vitro and delayed tumor growth in vivo. Tumor growth was further reduced using a fully modified version of miR-34a that has significantly increased stability.

Escape sites from the endo-lysosomal trafficking route manipulate exocytosis of nanoparticles in polar epithelium

The endo-lysosomal pathway is a major barrier for the trans-epithelial transport of nanoparticles (NPs), but escape strategies could facilitate trans-epithelial delivery. Based on the polarization properties of the epithelium, different escape compartments may result in different exocytosis fates of NPs and further affect the delivery efficiency. Therefore, optimizing the escape sites is critical for trans-epithelial delivery. Here, commonly used PEG-coated-poly(lactic-co-glycolic acid) (PLGA)-based nanoparticles were fabricated as model nanoparticles (MNPs) and the intestinal epithelium was chosen as the polarized epithelium. The MNPs were incubated with different endosomolytic agents for early endosomal escape, late endosomal escape and lysosomal escape, respectively. According to in vitro and in vivo studies, MNPs escaping from early endosomes and late endosomes exhibited stronger capacity for trans-epithelial transport than those escaping from lysosomes. By further probing into the mechanism, we surprisingly found that although MNPs escaping from early endosomes quickly egressed from the apical side of epithelia, they were subsequently followed by "reuptake" via caveolae and trafficked through the endoplasmic reticulum-Golgi apparatus (ER/GA) secretory pathway, achieving efficient trans-epithelial transport; MNPs escaping from late endosomes, which were located near the nucleus, were prone to enter the ER/GA for efficient basolateral exocytosis. However, MNPs escaping from lysosomes were detained within cells by autophagosomes. Collectively, our research suggested that early endosomes and late endosomes were ideal escape sites for trans-epithelial delivery.

Preparing and Evaluating the Stability of Therapeutically Relevant Oligonucleotide Duplexes

The field of oligonucleotide therapeutics is rapidly advancing, particularly for combating orphan diseases and cancer. However, the intrinsic instability of oligonucleotides, especially RNA, poses a substantial challenge in the face of the harsh conditions encountered intracellularly and in circulation. Therefore, evaluating the stability of oligos in serum is of great significance when developing oligonucleotide therapeutics. This protocol outlines a dependable and reproducible method for preparing oligonucleotide duplexes, coupled with confirmation by gel electrophoresis. Subsequently, the protocol defines a mechanism to assess the stability of the oligo duplexes in serum. This protocol seeks to establish a standardized reference for researchers, enabling them to compare the impact of various modifications on oligo stability and assess the degradation kinetics effectively. Key features • Adaptable for use with small interfering RNA (siRNA), microRNA (miRNA), antisense oligonucleotides (ASOs), and other unmodified and modified oligonucleotides. • Does not necessitate any Biological Safety Level clearance and offers a rapid, cost-effective, and entirely in vitro procedure. • Allows researchers to evaluate multiple modification patterns that, when coupled with targeting activity, allow for selecting the best modification pattern prior to in vivo analysis.

The Parkinson's disease related mutant VPS35 (D620N) amplifies the LRRK2 response to endolysosomal stress

The identification of multiple genes linked to Parkinson's disease (PD) invites the question as to how they may co-operate. We have generated isogenic cell lines that inducibly express either wild-type or a mutant form of the retromer component VPS35 (D620N), which has been linked to PD. This has enabled us to test proposed effects of this mutation in a setting where the relative expression reflects the physiological occurrence. We confirm that this mutation compromises VPS35 association with the WASH complex, but find no defect in WASH recruitment to endosomes, nor in the distribution of lysosomal receptors, cation-independent mannose-6-phosphate receptor and Sortilin. We show VPS35 (D620N) enhances the activity of the Parkinson's associated kinase LRRK2 towards RAB12 under basal conditions. Furthermore, VPS35 (D620N) amplifies the LRRK2 response to endolysosomal stress resulting in enhanced phosphorylation of RABs 10 and 12. By comparing different types of endolysosomal stresses such as the ionophore nigericin and the membranolytic agent l-leucyl-l-leucine methyl ester, we are able to dissociate phospho-RAB accumulation from membrane rupture.

A first-in-class fully modified version of miR-34a with outstanding stability, activity, and anti-tumor efficacy

Altered by defects in p53, epigenetic silencing, and genomic loss, the microRNA miR-34a represents one of the most clinically relevant tumor-suppressive microRNAs. Without question, a striking number of patients with cancer would benefit from miR-34a replacement, if poor miR-34a stability, non-specific delivery, and delivery-associated toxicity could be overcome. Here, we highlight a fully modified version of miR-34a (FM-miR-34a) that overcomes these hurdles when conjugated to a synthetically simplistic ligand. FM-miR-34a is orders of magnitude more stable than a partially modified version, without compromising its activity, leading to stronger repression of a greater number of miR-34a targets. FM-miR-34a potently inhibited proliferation and invasion, and induced sustained downregulation of endogenous target genes for >120 h following in vivo delivery. In vivo targeting was achieved through conjugating FM-miR-34a to folate (FM-FolamiR-34a), which inhibited tumor growth leading to complete cures in some mice. These results have the ability to revitalize miR-34a as an anti-cancer agent, providing a strong rationale for clinical testing.

Could artificial intelligence revolutionize the development of nanovectors for gene therapy and mRNA vaccines?

Gene therapy enables the introduction of nucleic acids like DNA and RNA into host cells, and is expected to revolutionize the treatment of a wide range of diseases. This growth has been further accelerated by the discovery of CRISPR/Cas technology, which allows accurate genomic editing in a broad range of cells and organisms in vitro and in vivo. Despite many advances in gene delivery and the development of various viral and non-viral gene delivery vectors, the lack of highly efficient non-viral systems with low cellular toxicity remains a challenge. The application of cutting-edge technologies such as artificial intelligence (AI) has great potential to find new paradigms to solve this issue. Herein, we review AI and its major subfields including machine learning (ML), neural networks (NNs), expert systems, deep learning (DL), computer vision and robotics. We discuss the potential of AI-based models and algorithms in the design of targeted gene delivery vehicles capable of crossing extracellular and intracellular barriers by viral mimicry strategies. We finally discuss the role of AI in improving the function of CRISPR/Cas systems, developing novel nanobots, and mRNA vaccine carriers.

Delivery of RNA Therapeutics: The Great Endosomal Escape!

RNA therapeutics, including siRNAs, antisense oligonucleotides, and other oligonucleotides, have great potential to selectively treat a multitude of human diseases, from cancer to COVID to Parkinson's disease. RNA therapeutic activity is mechanistically driven by Watson-Crick base pairing to the target gene RNA without the requirement of prior knowledge of the protein structure, function, or cellular location. However, before widespread use of RNA therapeutics becomes a reality, we must overcome a billion years of evolutionary defenses designed to keep invading RNAs from entering cells. Unlike small-molecule therapeutics that are designed to passively diffuse across the cell membrane, macromolecular RNA therapeutics are too large, too charged, and/or too hydrophilic to passively diffuse across the cellular membrane and are instead taken up into cells by endocytosis. However, similar to the cell membrane, endosomes comprise a lipid bilayer that entraps 99% or more of RNA therapeutics, even in semipermissive tissues such as the liver, central nervous system, and muscle. Consequently, before RNA therapeutics can achieve their ultimate clinical potential to treat widespread human disease, the rate-limiting delivery problem of endosomal escape must be solved in a clinically acceptable manner.

Tracking the Endosomal Escape: A Closer Look at Calcein and Related Reporters

Crossing the cellular membrane and delivering active pharmaceuticals or biologicals into the cytosol of cells is an essential step in the development of nanomedicines. One of the most important intracellular processes regarding the cellular uptake of biologicals is the endolysosomal pathway. Sophisticated nanocarriers have been developed overcoming a major hurdle, the endosomal entrapment, and delivering their cargo to the required site of action. In parallel, in vitro assays have been established analyzing the performance of these nanocarriers. Among them, the release of the membrane-impermeable dye calcein has become a popular and straightforward method. It is accessible for most researchers worldwide, allows for rapid conclusions about the release potential, and enables the study of release mechanisms. This review is intended to provide an overview and guidance for scientists applying the calcein release assay. It comprises a survey of several applications in the study of endosomal escape, considerations of potential pitfalls, challenges and limitations of the assay, and a brief summary of complementary methods. Based on this review, we hope to encourage further research groups to take advantage of the calcein release assay for their own purposes and help to create a database for more efficient cross-correlations between nanocarriers. This article is protected by copyright. All rights reserved.

Modulating intracellular pathways to improve non-viral delivery of RNA therapeutics

RNA therapeutics (e.g. siRNA, oligonucleotides, mRNA, etc.) show great potential for the treatment of a myriad of diseases. However, to reach their site of action in the cytosol or nucleus of target cells, multiple intra- and extracellular barriers have to be surmounted. Several non-viral delivery systems, such as nanoparticles and conjugates, have been successfully developed to meet this requirement. Unfortunately, despite these clear advances, state-of-the-art delivery agents still suffer from relatively low intracellular delivery efficiencies. Notably, our current understanding of the intracellular delivery process is largely oversimplified. Gaining mechanistic insight into how RNA formulations are processed by cells will fuel rational design of the next generation of delivery carriers. In addition, identifying which intracellular pathways contribute to productive RNA delivery could provide opportunities to boost the delivery performance of existing nanoformulations. In this review, we discuss both established as well as emerging techniques that can be used to assess the impact of different intracellular barriers on RNA transfection performance. Next, we highlight how several modulators, including small molecules but also genetic perturbation technologies, can boost RNA delivery by intervening at differing stages of the intracellular delivery process, such as cellular uptake, intracellular trafficking, endosomal escape, autophagy and exocytosis.

Application of impedance measurement to investigate in vitro inhalation toxicity of bacteria

BACKGROUND

Workers of agriculture and intensive life stock farming are exposed to highly contaminated workplaces. Bioaerosol exposures are suspected to trigger respiratory health effects of the workers. So far, risk evaluation of bioaerosols has been assessed through the infectivity of comprising biological agents that is classified in Europe by four risk groups according to the criteria of Directive 2000/54EC of the European Parliament. However, this directive additionally requires the risk assessment of allergenic and toxigenic effects without further elaboration. The aim of our study was to establish an in vitro screening system that is able to measure inhalative toxic effects of bacteria and their metabolites.

METHODS

In this study, we analyzed three bacterial toxins and five culture supernatants of selected bacteria with known toxicity as model agents exposed to the lung epithelial cell line NuLi-1. We used electrical cell-substrate impedance sensing (ECIS) method to monitor real-time cell changes and the viability test Prestoblue™.

RESULTS

We confirmed concentration dependent cytotoxic effects of the selected toxins in NuLi-1 cells over a period of up to 48 h. Each toxin resulted in a different but specific impedance profile over time according to their mode of action, whereas viability assay showed the metabolic activity of the cells at a chosen time point without revealing any information on their mode of action. Furthermore, dose-response-relationships were monitored. Tested model bacteria (Streptoccous pneumoniae, Acinetobacter radioresistens, Aerococcus viridans, Aeromonas hydrophila) reacted according to their expected toxicity except one bacterium (Enterococcus faecalis). The established assays revealed the concentration dependent onset and intensity of bacterial cytotoxicity and the viability of the cells at 24 h and 48 h exposure.

CONCLUSION

Impedance measurement and the viability assay Prestoblue™ in combination are suitable as sensitive screening methods to analyze toxic potential of bacteria and can therefor support the risk assessment of workplaces in terms of the directive 2000/54/EC.

Ligand-mediated delivery of RNAi-based therapeutics for the treatment of oncological diseases

RNA interference (RNAi)-based therapeutics (miRNAs, siRNAs) have great potential for treating various human diseases through their ability to downregulate proteins associated with disease progression. However, the development of RNAi-based therapeutics is limited by lack of safe and specific delivery strategies. A great effort has been made to overcome some of these challenges resulting in development of N-acetylgalactosamine (GalNAc) ligands that are being used for delivery of siRNAs for the treatment of diseases that affect the liver. The successes achieved using GalNAc-siRNAs have paved the way for developing RNAi-based delivery strategies that can target extrahepatic diseases including cancer. This includes targeting survival signals directly in the cancer cells and indirectly through targeting cancer-associated immunosuppressive cells. To achieve targeting specificity, RNAi molecules are being directly conjugated to a targeting ligand or being packaged into a delivery vehicle engineered to overexpress a targeting ligand on its surface. In both cases, the ligand binds to a cell surface receptor that is highly upregulated by the target cells, while not expressed, or expressed at low levels on normal cells. In this review, we summarize the most recent RNAi delivery strategies, including extracellular vesicles, that use a ligand-mediated approach for targeting various oncological diseases.

Protein Delivery: If Your GFP (or Other Small Protein) Is in the Cytosol, It Will Also Be in the Nucleus

Intracellular protein delivery is a transformative tool for biologics research and medicine. Delivery into the cytosol allows proteins to diffuse throughout the cell and access subcellular organelles. Inefficient delivery caused by endosomal entrapment is often misidentified as cytosolic delivery. This inaccuracy muddles what should be a key checkpoint in assessing delivery efficiency. Green fluorescent protein (GFP) is a robust cargo small enough to passively diffuse from the cytosol into the nucleus. Fluorescence of GFP in the nucleus is a direct readout for cytosolic access and effective delivery. Here, we highlight recent examples from the literature for the accurate assessment of cytosolic protein delivery using GFP fluorescence in the cytosol and nucleus.

Exploiting the anticancer effects of a nitrogen bisphosphonate nanomedicine for glioblastoma multiforme

Glioblastoma multiforme (GBM) is an incurable aggressive brain cancer in which current treatment strategies have demonstrated limited survival benefit. In recent years, nitrogen-containing bisphosphonates (N-BPs) have demonstrated direct anticancer effects in a number of tumour types including GBM. In this study, a nano-formulation with the RALA peptide was used to complex the N-BP, alendronate (ALN) into nanoparticles (NPs) < 200 nm for optimal endocytic uptake. Fluorescently labelled AlexaFluor®647 Risedronate was used as a fluorescent analogue to visualise the intracellular delivery of N-BPs in both LN229 and T98G GBM cells. RALA NPs were effectively taken up by GBM where a dose-dependent response was evidenced with potentiation factors of 14.96 and 13.4 relative to ALN alone after 72 h in LN229 and T98G cells, respectively. Furthermore, RALA/ALN NPs at the IC_50, significantly decreased colony formation, induced apoptosis and slowed spheroid growth in vitro. In addition, H-Ras membrane localisation was significantly reduced in the RALA/ALN groups compared to ALN or controls, indicative of prenylation inhibition. The RALA/ALN NPs were lyophilised to enhance stability without compromising the physiochemical properties necessary for functionality, highlighting the suitability of the NPs for scale-up and in vivo application. Collectively, these data show the significant potential of RALA/ALN NPs as novel therapeutics in the treatment of GBM.

Engineering Targeting Materials for Therapeutic Cancer Vaccines

Therapeutic cancer vaccines constitute a valuable tool to educate the immune system to fight tumors and prevent cancer relapse. Nevertheless, the number of cancer vaccines in the clinic remains very limited to date, highlighting the need for further technology development. Recently, cancer vaccines have been improved by the use of materials, which can strongly enhance their intrinsic properties and biodistribution profile. Moreover, vaccine efficacy and safety can be substantially modulated through selection of the site at which they are delivered, which fosters the engineering of materials capable of targeting cancer vaccines to specific relevant sites, such as within the tumor or within lymphoid organs, to further optimize their immunotherapeutic effects. In this review, we aim to give the reader an overview of principles and current strategies to engineer therapeutic cancer vaccines, with a particular focus on the use of site-specific targeting materials. We will first recall the goal of therapeutic cancer vaccination and the type of immune responses sought upon vaccination, before detailing key components of cancer vaccines. We will then present how materials can be engineered to enhance the vaccine's pharmacokinetic and pharmacodynamic properties. Finally, we will discuss the rationale for site-specific targeting of cancer vaccines and provide examples of current targeting technologies.

Carriers Break Barriers in Drug Delivery: Endocytosis and Endosomal Escape of Gene Delivery Vectors

Over the past decades, major efforts were undertaken to develop devices on a nanoscale level for the efficient and nontoxic delivery of molecules to tissues and cells, for the purpose of either diagnosis or treatment of disease. The application of such devices in drug delivery has proven to be beneficial for matters as diverse as drug solubility, drug targeting, controlled drug release, and transport of drugs across cellular barriers. Multiple nanotherapeutics have been approved for clinical treatment, and more products are being evaluated in preclinical and clinical trials. However, many biological barriers hinder the medical application of nanocarriers. There are two main classes of barriers that need to be overcome by drug nanocarriers: extracellular and intracellular barriers, both of which may capture and/or destroy therapeutics before they reach their target site. This Account discusses major biological barriers that are confronted by nanotherapeutics, following their systemic administration, focusing on cellular entry and endosomal escape of gene delivery vectors. The use of pH-responsive materials to overcome the endosomal barrier is addressed. Historically, cell biologists have studied the interaction between cells and pathogens in order to unveil the mechanisms of endocytosis and cell signaling. Meanwhile, it is becoming clear that cells may respond in similar ways to artificial drug delivery systems and, consequently, that knowledge on the cellular response against both pathogens and nanoparticulate systems will aid in the design of improved nanomedicine. A close collaboration between bioengineers and cell biologists will promote this development. At the same time, we have come to realize that tools that we use to study fundamental cellular processes, including metabolic inhibitors of endocytosis and overexpression/downregulation of proteins, may cause changes in cellular physiology. This calls for the implementation of refined methods to study nanocarrier-cell interactions, as is discussed in this Account. Finally, recent papers on the dynamics of cargo release from endosomes by means of live cell imaging have significantly advanced our understanding of the transfection process. They have initiated discussion (among others) on the limited number of endosomal escape events in transfection, and on the endosomal stage at which genetic cargo is most efficiently released. Advancements in imaging techniques, including super-resolution microscopy, in concert with techniques to label endogenous proteins and/or label proteins with synthetic fluorophores, will contribute to a more detailed understanding of nanocarrier-cell dynamics, which is imperative for the development of safe and efficient nanomedicine.

Enhancing MicroRNA Activity through Increased Endosomal Release Mediated by Nigericin

The therapeutic promise of small-RNA therapeutics is limited, not only by the lack of delivery vehicles, but also by the inability of the small RNAs to reach intracellular compartments where they can be biologically active. We previously reported successful delivery of functionally active miRNAs via receptor-mediated endocytosis. This type of targeted therapy still faces a major challenge in the delivery field: endosomal sequestration. Here, a new method has been developed to promote endosomal escape of delivered miRNA. The strategy relies on the difference in solute contents between nascent endosomes and the cytoplasm; early endosomes are rich in sodium ions, whereas the intracellular fluid is rich is potassium ions. Exploiting this difference through favoring the influx of potassium into the endosomes without the exchange of osmotically active sodium, results in an osmotic differential leading to the endosomes swelling and bursting. One molecule that is able to exchange potassium for an osmotically inactive hydrogen ion is the ionophore nigericin. Through generating an intramolecular miRNA delivery vehicle, containing a ligand, in this case folate and nigericin, we enabled the escape of folate-RNA conjugates from their entrapping endosomes into the cytoplasm where they bound the RNA-induced silencing complex and activated the RNAi response.

A Revisit to the Pretargeting Concept-A Target Conversion

Pretargeting is often used as a tumor targeting strategy that provides much higher tumor to non-tumor ratios than direct-targeting using radiolabeled antibody. Due to the multiple injections, pretargeting is investigated less than direct targeting, but the high T/NT ratios have rendered it more useful for therapy. While the progress in using this strategy for tumor therapy has been regularly reviewed in the literature, this review focuses on the nature and quantitative understanding of the pretargeting concept. By doing so, it is the goal of this review to accelerate pretargeting development and translation to the clinic and to prepare the researchers who are not familiar with the pretargeting concept but are interested in applying it. The quantitative understanding is presented in a way understandable to the average researchers in the areas of drug development and clinical translation who have the basic concept of calculus and general chemistry.