Nanoparticle entry into cells; the cell biology weak link

Zinc oxide nanoparticles promote migrasomes formation

The rising pollution from zinc oxide nanoparticles (ZnO-NPs) poses significant global concerns due to their widespread environmental presence and potential negative effects on human health. This study explores how ZnO-NPs impact migrasomes formation, a crucial process for cellular migration and communication. Our findings indicate that 28 nm ZnO-NPs enhance migrasomes formation, correlating with increased levels of phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] and GTP-RhoA-essential molecules in migrasomes biogenesis. Additionally, ZnO-NPs help alleviate mitochondrial damage caused by carbonyl cyanide 3-chlorophenylhydrazone (CCCP) through mitocytosis, which removes dysfunctional mitochondria, thereby preserving cellular integrity. The migrasomes induced by ZnO-NPs were found to contain various cellular components, including mitochondria, lysosomes, lipid droplets, and the ZnO-NPs themselves. These results underscore the role of ZnO-NPs in promoting migrasomes formation and protecting mitochondrial function, revealing significant implications for cellular behavior, therapeutic applications, and environmental and health safety.

Cellular internalization pathways of environmentally exposed microplastic particles: Phagocytosis or macropinocytosis?

Microplastic particles (MP) ubiquitously occur in all environmental compartments where they interact with biomolecules, forming an eco-corona on their surfaces. The eco-corona affects the surface properties of MP and consequently how they interact with cells. Proteins, an integral component within the eco-corona, may serve as a ligand driving the interaction of MP with membrane receptors. To date, it is not known, whether eco-coronae originating from different environmental media differ in their proteinaceous compositions and whether these particles interact differently with cells. We show that the protein composition of the eco-coronae formed in freshwater (FW) and salt water (SW) are distinct from each other. We did not observe different adhesion strengths between MP coated with different eco-coronae and cells. However, the internalization efficiency and the underlying internalization mechanisms significantly differed between FW- and SW eco-coronae. By inhibiting actin-driven and receptor-mediated internalization processes using Cytochalasin-D, Amiloride, and Amantadine, we show that FW microplastic particles predominantly become internalized via phagocytosis, while macropinocytosis is more important for SW microplastic particles. Overall, our findings show that the origin of eco-coronae coatings are important factors for the cellular internalization of microplastic particles. This highlights the relevance of eco-coronae for adverse effects of environmentally relevant microplastic particles on cells and organisms.

Mechanisms of receptor-mediated transcytosis at the blood-brain barrier

In receptor-mediated transcytosis (RMT) of large therapeutics across the blood-brain barrier (BBB), the construct - a macromolecule or a larger carrier with therapeutic payload - binds a protein on brain capillary endothelial cells (BCEC), with internalization and release into the brain parenchyma. The construct's internalization into, trafficking across and release from, but also possible entrapment within BCEC are affected by its engineered properties whose optimization has helped derive insights into transport mechanisms at BCEC. Furthermore, advances in multi-omics, as well as large-scale screening and directed evolution campaigns have helped identify new targets for RMT at BCEC. In this perspective, I raise and reflect on some fundamental questions one can arrive at by comparing the engineered properties of BBB-targeted constructs and the properties of different target proteins. These questions concern the underlying, transcytosis-promoting factors that the optimization of constructs' engineered properties appears to converge on, the precise role of target proteins in RMT, the different mechanisms through which these targets may mediate construct trafficking, and the tentative criteria for target selection on BCEC. Based on these considerations I propose several scenarios and strategies to interfere with the construct's trafficking for more efficient internalization, transport through the endosomal network toward the abluminal membrane, and release from BCEC, both for smaller macromolecules and for larger carriers.

Hurdles to healing: Overcoming cellular barriers for viral and nonviral gene therapy

Gene delivery offers great potential for treating various diseases, yet its success requires overcoming several biological barriers. These hurdles span from extracellular degradation, reaching the target cells, and inefficient cellular uptake to endosomal entrapment, cytoplasmic transport, nuclear entry, and transcription limitations. Viruses and non-viral vectors deal with these barriers via different mechanisms. Viral vectors, such as adenoviruses, adeno-associated viruses, and lentiviruses use natural mechanisms to efficiently deliver genetic material but face limitations including immunogenicity, cargo capacity, and production complexity. Nonviral vectors, including lipid nanoparticles, polymers, and protein-based systems, offer scalable and safer alternatives but often fall short in overcoming intracellular barriers and achieving high transfection efficiencies. Recent advancements in vector engineering have partially overcome several of these challenges. Ionizable lipids improve endosomal escape while minimizing toxicity. Biodegradable polymers balance efficacy with safety, and engineered protein systems, inspired by viral or bacterial entry mechanisms, integrate multifunctionality for enhanced delivery. Despite these advances, challenges, particularly in achieving robust in vivo translatability, scalability, and reduced immunogenicity, remain. This review synthesizes current knowledge of cellular barriers and the approaches to overcome them, providing a roadmap for designing more efficient gene delivery systems. By addressing these barriers, the field can advance toward safer, and more effective therapies.

Rod and spherical selenium nanoparticles: Physicochemical properties and effects on red blood cells and neutrophils

The influence of selenium (Se) nanoparticles in the form of rods (SeNrs) and spheres (SeSps), synthesized by laser ablation, on the structural and functional properties of human blood erythrocytes and neutrophils was studied for anticancer activity in vitro. SeNrs and SeSps do not have cytotoxicity towards neutrophils and do not cause hemolysis. The elastic modulus and resistance of erythrocytes to HOCl-induced hemolysis increased after binding of Se nanoparticles to the plasma membrane. The interaction of Se nanoparticles with neutrophils is accompanied by their actin-dependent macropinocytosis, triggering intracellular signaling processes leading to the assembly and activation of NADPH oxidase. Comparative analysis of the effects of SeNrs and SeSps on cells showed that they have similar effects. This may be due to the fact that SeNrs interact with the cell surface with their end faces, and, therefore, have the same initial contact with the plasma membrane as SeSps. However, SeSps and SeNrs showed chronic cytotoxicity after 48 h incubation, indicating the need to find ways to reduce their toxicity further. Further use of Se nanoparticles in anisotropic form in biomedical research for the development of therapeutic agents seems promising.

Endocytic highways: Navigating macropinocytosis and other endocytic routes for precision drug delivery

Drug molecules can reach intracellular targets by different mechanisms, such as passive diffusion, active transport, and endocytosis. Endocytosis is the process by which cells engulf extracellular material by forming a vesicle and transporting it into the cells. In addition to its biological functions, endocytosis plays a vital role in the internalization of the therapeutic molecules. Clathrin-mediated endocytosis, caveolar endocytosis, and macropinocytosis are the most researched routes in the field of drug delivery. In addition to conventional small therapeutic molecules, the use of nanoformulations and large molecules, such as nucleic acids, peptides, and antibodies, have broadened the field of drug delivery. Although the majority of small therapeutic molecules can enter cells via passive diffusion, large molecules, and advanced targeted delivery systems, such as nanoparticles, are internalized by the endocytic route. Therefore, it is imperative to understand the characteristics of the endocytic routes in greater detail to design therapeutic molecules or formulations for successful delivery to the intracellular targets. This review highlights the prospects and limitations of the major endocytic routes for drug delivery, with a major emphasis on macropinocytosis. Since macropinocytosis is a non-selective uptake of extracellular matrix, the selective induction of macropinocytosis, using compounds that induce macropinocytosis and modulate macropinosome trafficking pathways, could be a potential approach for the intracellular delivery of diverse therapeutic modalities. Furthermore, we have summarized the characteristics associated with the formulations or drug carriers that can affect the endocytic routes for cellular internalization. The techniques that are used to study the intracellular uptake processes of therapeutic molecules are briefly discussed. Finally, the major limitations for intracellular targeting, endo-lysosomal degradation, and different approaches that have been used in overcoming these limitations, are highlighted in this review.

Oxygen/sulfate radicals-generating CaS2O8 nanosonosensitizers induce PANoptosis and calcium overload for enhanced peritoneal metastasis immunotherapy

Peritoneal metastasis (PM) is typically intractable by immunotherapy due to an immunosuppressive microenvironment and the peritoneal-plasma barrier. Sonodynamic therapy (SDT) presents unique advantages of noninvasive in situ treatment and the potential for antitumor immune activation. Building upon SDT technology, the study reports on a novel biodegradable sonosensitizer, CaS2O8, characterized by a narrow bandgap, abundant oxygen vacancies and a rapid ultrasound (US) response for abdominal SDT. Such sonosensitizer only produces lethal reactive oxygen species (ROS) after US irradiation, which is nontoxic in a physiological environment. After US irradiation, CaS2O8 yields a large amount of sulfate radical (SO4-), as well as sonodynamic related ROS (OH, and 1O2), which exerts a synergistic effect with Ca2+ overload to induce Z-conformation nucleic acid by augmenting oxidative damage. As a result, the PANoptosis is initiated through the ZBP1/RIPK3 pathway in tumor cells. This inflammatory cell death leads to a multi-faceted release of tumor cell contents which serve as an in situ tumor antigen to induce a robust antitumor immune response. Notably, the precision sono-immunotherapy enhances the infiltration of T cells into tumors by transforming an immunosuppressive phenotype into an immunostimulatory one. Therefore, targeting PANoptosis by CaS2O8-induced SDT can provide an alternative or additional clinical treatment and prolonged survival outcome for patients with PM.

Engineering a Self-Delivery Nanoplatform for Chemo-Photodynamic-Immune Synergistic Therapies against Aggressive Melanoma

The effectiveness of immunotherapy in killing melanoma is hindered by a T-cell deficiency and the lack of tumor immunogenicity. Consequently, there is an urgent need for a platform that can further activate the immune system and boost the immune response of the host to tumors. Compared with monotherapy, combination therapy shows promise in improving treatment efficacy and response rates. This study introduces the pioneering use of a rationally designed active targeting nanoplatform to bind axitinib, paclitaxel, and verteporfin to human serum albumin (APV@HSA NPs). APV@HSA NPs have demonstrated the capability to induce dual-induced apoptosis in tumor cells through chemo- and photodynamic effects, while also enhancing immunogenic cell death and promoting dendritic cell maturation. Additionally, the platform promoted the production of CD8+ T cells and memory T cells and inhibited vascular endothelial growth factor via axitinib, facilitating the infiltration of immune effector cells and optimizing chemo-photodynamic immunotherapy. Hence, amplified chemo-photodynamic-immunological nanomedicines with excellent biocompatibility have been redesigned to inhibit the tumor microenvironment and combat the growth of primary tumor and lung metastasis. This approach initiates a series of immune responses, presenting a promising therapeutic strategy for melanoma.

Cell-penetrating Peptides as Keys to Endosomal Escape and Intracellular Trafficking in Nanomedicine Delivery

This review article discusses the challenges of delivering cargoes to the cytoplasm, for example, proteins, peptides, and nucleic acids, and the mechanisms involved in endosomal escape. Endocytosis, endosomal maturation, and exocytosis pose significant barriers to effective cytoplasmic delivery. The article explores various endosomal escape mechanisms, such as the proton sponge effect, osmotic lysis, membrane fusion, pore formation, membrane destabilization/ disruption, and vesicle budding and collapse. Additionally, it discusses the role of lysosomes, glycocalyx, and molecular crowding in the cytoplasmic delivery process. Despite the recent advances in nonviral delivery systems, there is still a need to improve cytoplasmic delivery. Strategies such as fusogenic peptides, endosomolytic polymers, and cell-penetrating peptides have shown promise in improving endosomal escape and cytoplasmic delivery. More research is needed to refine these strategies and make them safer and more effective. In conclusion, the article highlights the challenges associated with cytoplasmic delivery and the importance of understanding the mechanisms involved in endosomal escape. A better understanding of these processes could result in the creation of greater effectiveness and safe delivery systems for various cargoes, including proteins, peptides, and nucleic acids.

A Purely Biomanufactured System for Delivering Nanoparticles and STING Agonists

Nanovaccines have significantly contributed in the prevention and treatment of diseases. However, most of these technologies rely on chemical or hybrid semibiological synthesis methods, which limit the manufacturing performance advantages and improved inoculation outcomes compared with traditional vaccines. Herein, a universal and purely biological nanovaccine system is reported. This system integrates three modules: (1) self-assembling nanoparticles, (2) self-catalyzed synthesis of small-molecule stimulator of interferon gene (STING) agonists, and (3) delivery vectors that target the cytosolic surveillance system. Various nanoparticles are efficiently self-assembled using this system. After confirming the excellent immunostimulatory and lymph node targeting of this system, its broad-spectrum antiviral efficacy is further demonstrated. By leveraging the comprehensive biosynthetic capabilities of bacterial cells, this system can efficiently combine various adjuvant-active modular components and antigenic cargo, thereby providing a highly diversified and potent vaccine platform.

Polyoxazolines with Cholesterol Lipid Anchor for Fast Intracellular Delivery

Due to the increasing challenges posed by the growing immunity to poly(ethylene glycol) (PEG), there is growing interest in innovative polymer-based materials as viable alternatives. In this study, the advantages of lipids and polymers are combined to allow efficient and rapid cytoplasmic drug delivery. Specifically, poly(2-methyl-2-oxazoline) is modified with a cholesteryl hemisuccinate group as a lipid anchor (CHEMSPOx). The CHEMSPOx is additionally functionalized with a coumarin group (CHEMSPOx-coumarin). Both polymers self-assembled in water into vesicles of ≈100 nm and are successfully loaded with a hydrophobic model drug. The loaded vesicles reveal high cellular internalization across variant cell lines within 1 h at 37 °C as well as 4 °C, albeit to a lesser extent. A kinetic study confirms the fast internalization within 5 min after the sample's addition. Therefore, different internalization pathways are involved, e.g., active uptake but also nonenergy dependent mechanisms. CHEMSPOx and CHEMSPOx-coumarin further demonstrate excellent cyto-, hemo-, and membrane compatibility, as well as a membrane-protecting effect, which underlines their good safety profile for potential biological intravenous application. Overall, CHEMSPOx, as a lipopolyoxazoline, holds great potential for versatile biological applications such as fast and direct intracellular delivery or cellular lysis protection.

Intestinal nanoparticle delivery and cellular response: a review of the bidirectional nanoparticle-cell interplay in mucosa based on physiochemical properties

Orally administered nanocarriers play an important role in improving druggability, promoting intestinal absorption, and enhancing therapeutic applications for the treatment of local and systemic diseases. However, the delivering efficiency and cell response in mucosa to orally administered nanocarriers is affected by the physiological environment and barriers in the gastrointestinal tract, the physicochemical properties of the nanocarriers, and their bidirectional interactions. Goblet cells secrete and form extracellular mucus, which hinders the movement of nanoparticles. Meanwhile, intestinal epithelial cells may absorb the NPs, allowing for their transcytosis or degradation. Conversely, nanoparticle-induced toxicity may occur as a biological response to the nanoparticle exposure. Additionally, immune response and cell functions in secretions such as mucin, peptide, and cytokines may also be altered. In this review, we discuss the bidirectional interactions between nanoparticles and cells focusing on enterocytes and goblet cells, M cells, and immune cells in the mucosa according to the essential role of intestinal epithelial cells and their crosstalk with immune cells. Furthermore, we discuss the recent advances of how the physiochemical properties of nanoparticles influence their interplay, delivery, and fate in intestinal mucosa. Understanding the fate of nanoparticles with different physiochemical properties from the perspective of their interaction with cells in mucosa provides essential support for the development, rational design, potency maximation, and application of advanced oral nanocarrier delivery systems.

New Cellular Models to Support Preclinical Studies on ICAM-1-Targeted Drug Delivery

Intercellular adhesion molecule 1 (ICAM-1) is a cell-surface protein actively explored for targeted drug delivery. Anti-ICAM-1 nanocarriers (NCs) target ICAM-1-positive sites after intravenous injection in animal models, but quantitative mechanistic examination of cellular-level transport in vivo is not possible. Prior studies in human cell cultures indicated efficient uptake of these formulations via cell adhesion molecule-(CAM)-mediated endocytosis. However, ICAM-1 sequence differs among species; thus, whether anti-ICAM-1 NCs induce similar behavior in animal cells, key for intracellular drug delivery, is unknown. To begin bridging this gap, we first qualitatively verified intracellular transport of anti-ICAM-1 NCs in vivo and then developed new cellular models expressing ICAM-1 from mouse, dog, pig, and monkey, species relevant to pharmaceutical translation and veterinary medicine. ICAM-1 expression was verified by flow cytometry and confocal microscopy. These cells showed specific targeting compared to IgG NCs or cells treated with anti-ICAM-1 blocker. Anti-ICAM-1 NCs entered cells in a time- and temperature-dependent manner, with kinetics and pathway compatible with CAM-mediated endocytosis. All parameters tested were strikingly similar to those from human cells expressing ICAM-1 endogenously. Therefore, this new cellular platform represents a valuable tool that can be used in parallel to support in vivo studies on ICAM-1-targeted NCs during pharmaceutical translation.

Expanding the field of view - a simple approach for interactive visualisation of electron microscopy data

The unparalleled resolving power of electron microscopy is both a blessing and a curse. At 30,000× magnification, 1 µm corresponds to 3 cm in the image and the field of view is only a few micrometres or less, resulting in an inevitable reduction in the spatial data available in an image. Consequently, the gain in resolution is at the cost of loss of the contextual 'reference space', which is crucial for understanding the embedded structures of interest. This problem is particularly pronounced in immunoelectron microscopy, where the detection of a gold particle is crucial for the localisation of specific molecules. The common solution of presenting high-magnification and overview images side by side often insufficiently represents the cellular environment. To address these limitations, we propose here an interactive visualization strategy inspired by digital maps and GPS modules which enables seamless transitions between different magnifications by dynamically linking virtual low magnification overview images with primary high-resolution data. By enabling dynamic browsing, it offers the potential for a deeper understanding of cellular landscapes leading to more comprehensive analysis of the primary ultrastructural data.

Endocytosis: the match point of nanoparticle-based cancer therapy

Nanomedicine has inspired a ground-breaking strategy for cancer therapy. By intelligently assembling diverse moieties to form nanoparticles, numerous functionalities such as controlled release, synergistic efficiency, and in situ killing can be achieved. The emerging nanoparticles have been designed with elevated targeting efficiency as targeting cancer cells is the primary requirement for nanoparticles. However, effective targeting does not guarantee therapeutic effects as endocytosis is a prerequisite for nanoparticles to exert effects. The recent decade has witnessed the rapid development of endocytosis-oriented nanoparticles, and this review subtly analyzes, categorizes, and exemplifies these nanoparticles according to their biological internalization patterns, and the correlation between the endocytosis mechanism and the property of nanoparticles is bridged. Based on the interdisciplinary vision, the present challenges and future perspectives of nanoparticle design for successful endocytosis are discussed, highlighting the potential strategies for the future development of endocytosis-oriented nanoparticles, thus facilitating the endocytosis-oriented strategy from bench to bedside. The undeniable fact is that endocytosis-oriented nanoparticles will definitely bring new blood to the next generation of advanced cancer therapies.

Entry of nanoparticles into cells and tissues: status and challenges

In this article we discuss how nanoparticles (NPs) of different compositions may interact with and be internalized by cells, and the consequences of that for cellular functions. A large number of NPs are made with the intention to improve cancer treatment, the goal being to increase the fraction of injected drug delivered to the tumor and thereby improve the therapeutic effect and decrease side effects. Thus, we discuss how NPs are delivered to tumors and some challenges related to investigations of biodistribution, pharmacokinetics, and excretion. Finally, we discuss requirements for bringing NPs into clinical use and aspects when it comes to usage of complex and slowly degraded or nondegradable NPs.

Difference in Endocytosis Pathways Used by Differentiated Versus Nondifferentiated Epithelial Caco-2 Cells to Internalize Nanosized Particles

Understanding the internalization of nanosized particles by mucosal epithelial cells is essential in a number of areas including viral entry at mucosal surfaces, nanoplastic pollution, as well as design and development of nanotechnology-type medicines. Here, we report our comparative study on pathways of cellular internalization in epithelial Caco-2 cells cultured in vitro as either a polarized, differentiated cell layer or as nonpolarized, nondifferentiated cells. The study reveals a number of differences in the extent that endocytic processes are used by cells, depending on their differentiation status and the nature of applied nanoparticles. In polarized cells, actin-driven and dynamin-independent macropinocytosis plays a prominent role in the internalization of both positively and negatively charged nanoparticles, contrary to its modest contribution in nonpolarized cells. Clathrin-mediated cellular entry plays a prominent role in the endocytosis of positive nanoparticles and cholesterol inhibition in negative nanoparticles. However, in nonpolarized cells, dynamin-dependent endocytosis is a major pathway in the internalization of both positive and negative nanoparticles. Cholesterol depletion affects both nonpolarized and polarized cells' internalization of positive and negative nanoparticles, which, in addition to the effect of cholesterol-binding inhibitors on the internalization of negative nanoparticles, indicates the importance of membrane cholesterol in endocytosis. The data collectively provide a new contribution to understanding endocytic pathways in epithelial cells, particularly pointing to the importance of the cell differentiation stage and the nature of the cargo.

PM2.5-induced DNA oxidative stress in A549 cells and regulating mechanisms by GST DNA methylation and Keap1/Nrf2 pathway

Fine particulate matter (PM2.5) increases the risks of lung cancer. Epigenetics provides a new toxicology mechanism for the adverse health effects of PM2.5. However, the regulating mechanisms of PM2.5 exposure on candidate gene DNA methylation changes in the development of lung cancer remain unclear. Abnormal expression of the glutathione S transferase (GST) gene is associated with cancer. However, the relationship between PM2.5 and DNA methylation-mediated GST gene expression is not well understood. In this study, we performed GST DNA methylation analysis and GST-related gene expression in human A549 cells exposed to PM2.5 (0, 50, 100 µg/mL, from Taiyuan, China) for 24 h (n = 4). We found that PM2.5 may cause DNA oxidative damage to cells and the elevation of GSTP1 promotes cell resistance to reactive oxygen species (ROS). The Kelch-1ike ECH-associated protein l (Keap1)/nuclear factor NF-E2-related factor 2 (Nrf2) pathway activates the GSTP1. The decrease in the DNA methylation level of the GSTP1 gene enhances GSTP1 expression. GST DNA methylation is associated with reduced levels of 5-methylcytosine (5mC), DNA methyltransferase 1 (DNMT1), and histone deacetylases 3 (HDAC3). The GSTM1 was not sensitive to PM2.5 stimulation. Our findings suggest that PM2.5 activates GSTP1 to defend PM2.5-induced ROS and 8-hydroxy-deoxyguanosine (8-OHdG) formation through the Keap1/Nrf2 signaling pathway and GSTP1 DNA methylation.

Bridging Smart Nanosystems with Clinically Relevant Models and Advanced Imaging for Precision Drug Delivery

Intracellular delivery of nano-drug-carriers (NDC) to specific cells, diseased regions, or solid tumors has entered the era of precision medicine that requires systematic knowledge of nano-biological interactions from multidisciplinary perspectives. To this end, this review first provides an overview of membrane-disruption methods such as electroporation, sonoporation, photoporation, microfluidic delivery, and microinjection with the merits of high-throughput and enhanced efficiency for in vitro NDC delivery. The impact of NDC characteristics including particle size, shape, charge, hydrophobicity, and elasticity on cellular uptake are elaborated and several types of NDC systems aiming for hierarchical targeting and delivery in vivo are reviewed. Emerging in vitro or ex vivo human/animal-derived pathophysiological models are further explored and highly recommended for use in NDC studies since they might mimic in vivo delivery features and fill the translational gaps from animals to humans. The exploration of modern microscopy techniques for precise nanoparticle (NP) tracking at the cellular, organ, and organismal levels informs the tailored development of NDCs for in vivo application and clinical translation. Overall, the review integrates the latest insights into smart nanosystem engineering, physiological models, imaging-based validation tools, all directed towards enhancing the precise and efficient intracellular delivery of NDCs.

Lipid Nanoparticle-Based Delivery System-A Competing Place for mRNA Vaccines

mRNA, as one of the foci of biomedical research in the past decade, has become a candidate vaccine solution for various infectious diseases and tumors and for regenerative medicine and immunotherapy due to its high efficiency, safety, and effectiveness. A stable and effective delivery system is needed to protect mRNAs from nuclease degradation while also enhancing immunogenicity. The success of mRNA lipid nanoparticles in treating COVID-19, to a certain extent, marks a milestone for mRNA vaccines and also promotes further research on mRNA delivery systems. Here, we explore mRNA vaccine delivery systems, especially lipid nanoparticles (LNPs), considering the current research status, prospects, and challenges of lipid nanoparticles, and explore other mRNA delivery systems.

Delivery of mRNA Vaccine with 1, 2-Diesters-Derived Lipids Elicits Fast Liver Clearance for Safe and Effective Cancer Immunotherapy

Messenger RNA (mRNA) vaccine is explored as a promising strategy for cancer immunotherapy, but the side effects, especially the liver-related damage caused by LNP, raise concerns about its safety. In this study, a novel library of 248 ionizable lipids comprising 1,2-diesters is designed via a two-step process involving the epoxide ring-opening reaction with carboxyl group-containing alkyl chains followed by an esterification reaction with the tertiary amines. Owing to the special chemical structure of 1,2-diesters, the top-performing lipids and formulations exhibit a faster clearance rate in the liver, contributing to increased stability and higher safety compared with DLin-MC3-DMA. Moreover, the LNP shows superior intramuscular mRNA delivery and elicits robust antigen-specific immune activation. The vaccinations delivered by the LNP system suppress tumor growth and prolong survival in both model human papillomavirus E7 and ovalbumin antigen-expressing tumor models. Finally, the structure of lipids which enhances the protein expression in the spleen and draining lymph nodes compared with ALC-0315 lipid in Comirnaty is further optimized. In conclusion, the 1, 2-diester-derived lipids exhibit rapid liver clearance and effective anticancer efficiency to different types of antigens-expressing tumor models, which may be a safe and universal platform for mRNA vaccines.

PEGylated nanoparticles interact with macrophages independently of immune response factors and trigger a non-phagocytic, low-inflammatory response

Poly-ethylene-glycol (PEG)-based nanoparticles (NPs) - including cylindrical micelles (CNPs), spherical micelles (SNPs), and PEGylated liposomes (PLs) - are hypothesized to be cleared in vivo by opsonization followed by liver macrophage phagocytosis. This hypothesis has been used to explain the rapid and significant localization of NPs to the liver after administration into the mammalian vasculature. Here, we show that the opsonization-phagocytosis nexus is not the major factor driving PEG-NP - macrophage interactions. First, mouse and human blood proteins had insignificant affinity for PEG-NPs. Second, PEG-NPs bound macrophages in the absence of serum proteins. Third, lipoproteins blocked PEG-NP binding to macrophages. Because of these findings, we tested the postulate that PEG-NPs bind (apo)lipoprotein receptors. Indeed, PEG-NPs triggered an in vitro macrophage transcription program that was similar to that triggered by lipoproteins and different from that triggered by lipopolysaccharide (LPS) and group A Streptococcus. Unlike LPS and pathogens, PLs did not increase transcripts involved in phagocytosis or inflammation. High-density lipoprotein (HDL) and SNPs triggered remarkably similar mouse bone-marrow-derived macrophage transcription programs. Unlike opsonized pathogens, CNPs, SNPs, and PLs lowered macrophage autophagosome levels and either reduced or did not increase the secretion of key macrophage pro-inflammatory cytokines and chemokines. Thus, the sequential opsonization and phagocytosis process is likely a minor aspect of PEG-NP - macrophage interactions. Instead, PEG-NP interactions with (apo)lipoprotein and scavenger receptors appear to be a strong driving force for PEG-NP - macrophage binding, entry, and downstream effects. We hypothesize that the high presence of these receptors on liver macrophages and on liver sinusoidal endothelial cells is the reason PEG-NPs localize rapidly and strongly to the liver.

The role and application of vesicles in triple-negative breast cancer: Opportunities and challenges

Extracellular vesicles (EVs) carry DNA, RNA, protein, and other substances involved in intercellular crosstalk and can be used for the targeted delivery of drugs. Triple-negative breast cancer (TNBC) is rich in recurrent and metastatic disease and lacks therapeutic targets. Studies have proved the role of EVs in the different stages of the genesis and development of TNBC. Cancer cells actively secrete various biomolecules, which play a significant part establishing the tumor microenvironment via EVs. In this article, we describe the roles of EVs in the tumor immune microenvironment, metabolic microenvironment, and vascular remodeling, and summarize the application of EVs for objective delivery of chemotherapeutic drugs, immune antigens, and cancer vaccine adjuvants. EVs-based therapy may represent the next-generation tool for targeted drug delivery for the cure of a variety of diseases lacking effective drug treatment.

Non-Pore Dependent and MMP-9 Responsive Gelatin/Silk Fibroin Composite Microparticles as Universal Delivery Platform for Inhaled Treatment of Lung Cancer

Developing a drug delivery platform that possesses universal drug loading capacity to meet various requirements of cancer treatment is a challenging yet interesting task. Herein, a self-assembled gelatin/silk fibroin composite (GSC) particle based drug delivery system is developed via microphase separation followed by desolvation process. Thanks to its preassembled microphase stage, this GSC system is suitable for varying types of drugs. The desolvation process fix drugs inside GSC rapidly and densify the GSC structure, thereby achieving efficient drug loading and providing comprehensive protection for loaded drugs. Actually, the size of this brand-new non-pore dependent drug delivery system can be easily adjusted from 100 nm to 20 µm to fit different scenarios. This work selects GSC with 3 µm diameter as the universal inhaled drug delivery platform, which shows an excellent transmucosal penetration and lung retention ability. Additionally, the MMP-9 sensitive degradation property of GSC enhances the targeted efficiency of drugs and reduces side effects. Intestinally, GSC can self-amplify the regulation of innate immunity to reverse the cancerous microenvironment into an antitumor niche, significantly improving the therapeutic effect of drugs. This study of GSC universal drug platform provides a new direction to develop the next-generation of drug delivery system for lung cancer.

Lipid-based nanocarriers challenging the ocular biological barriers: Current paradigm and future perspectives

Eye is the most specialized and sensory body organ and treating eye diseases efficiently is necessary. Despite various attempts, the design of a consummate ophthalmic drug delivery system remains unsolved because of anatomical and physiological barriers that hinder drug transport into the desired ocular tissues. It is important to advance new platforms to manage ocular disorders, whether they exist in the anterior or posterior cavities. Nanotechnology has piqued the interest of formulation scientists because of its capability to augment ocular bioavailability, control drug release, and minimize inefficacious drug absorption, with special attention to lipid-based nanocarriers (LBNs) because of their cellular safety profiles. LBNs have greatly improved medication availability at the targeted ocular site in the required concentration while causing minimal adverse effects on the eye tissues. Nevertheless, the exact mechanisms by which lipid-based nanocarriers can bypass different ocular barriers are still unclear and have not been discussed. Thus, to bridge this gap, the current work aims to highlight the applications of LBNs in the ocular drug delivery exploring the different ocular barriers and the mechanisms viz. adhesion, fusion, endocytosis, and lipid exchange, through which these platforms can overcome the barrier characteristics challenges.

Tumor Abnormality-Oriented Nanomedicine Design

Anticancer nanomedicines have been proven effective in mitigating the side effects of chemotherapeutic drugs. However, challenges remain in augmenting their therapeutic efficacy. Nanomedicines responsive to the pathological abnormalities in the tumor microenvironment (TME) are expected to overcome the biological limitations of conventional nanomedicines, enhance the therapeutic efficacies, and further reduce the side effects. This Review aims to quantitate the various pathological abnormalities in the TME, which may serve as unique endogenous stimuli for the design of stimuli-responsive nanomedicines, and to provide a broad and objective perspective on the current understanding of stimuli-responsive nanomedicines for cancer treatment. We dissect the typical transport process and barriers of cancer drug delivery, highlight the key design principles of stimuli-responsive nanomedicines designed to tackle the series of barriers in the typical drug delivery process, and discuss the "all-into-one" and "one-for-all" strategies for integrating the needed properties for nanomedicines. Ultimately, we provide insight into the challenges and future perspectives toward the clinical translation of stimuli-responsive nanomedicines.

Fabrication of phosphatidylcholine-EGCG nanoparticles with sustained release in simulated gastrointestinal digestion and their transcellular permeability in a Caco-2 monolayer model

In this study, we prepared phosphatidylcholine (PC)-EGCG complex nanoparticles (P-E NPs) by solvent reflux method. The physicochemical properties, in vitro digestion, uptake in Caco-2 cells, and bidirectional permeability of P-E NPs were systematically investigated. The constructed P-E1.5:1 NPs had an average particle size of 118 nm, a ζ-potential of -37.8 mV, and a polymerization dispersion index (PDI) of 0.16. The encapsulation efficiency (EE) of EGCG was 85.0% and the loading capacity (LC) was 24.4%. UV spectra, FTIR, XRD and intermolecular force results indicated that hydrophobic, electrostatic and hydrogen bonding interactions contributed to formate P-E1.5:1 NPs. P-E1.5:1 NPs exhibited first-order kinetics sustained release properties in simulated gastrointestinal digestion. Furthermore, P-E1.5:1 NPs were able to enhance absorptive transport and inhibit efflux transport mediated by MRP2 and P-gp compared to EGCG. These results indicated that P-E1.5:1 NPs may be a potential strategy to ameliorate EGCG bioavailability.

mRNA nanodelivery systems: targeting strategies and administration routes

With the great success of coronavirus disease (COVID-19) messenger ribonucleic acid (mRNA) vaccines, mRNA therapeutics have gained significant momentum for the prevention and treatment of various refractory diseases. To function efficiently in vivo and overcome clinical limitations, mRNA demands safe and stable vectors and a reasonable administration route, bypassing multiple biological barriers and achieving organ-specific targeted delivery of mRNA. Nanoparticle (NP)-based delivery systems representing leading vector approaches ensure the successful intracellular delivery of mRNA to the target organ. In this review, chemical modifications of mRNA and various types of advanced mRNA NPs, including lipid NPs and polymers are summarized. The importance of passive targeting, especially endogenous targeting, and active targeting in mRNA nano-delivery is emphasized, and different cellular endocytic mechanisms are discussed. Most importantly, based on the above content and the physiological structure characteristics of various organs in vivo, the design strategies of mRNA NPs targeting different organs and cells are classified and discussed. Furthermore, the influence of administration routes on targeting design is highlighted. Finally, an outlook on the remaining challenges and future development toward mRNA targeted therapies and precision medicine is provided.

Nanomaterial genotoxicity evaluation using the high-throughput p53-binding protein 1 (53BP1) assay

Toxicity evaluation of engineered nanomaterials is challenging due to the ever increasing number of materials and because nanomaterials (NMs) frequently interfere with commonly used assays. Hence, there is a need for robust, high-throughput assays with which to assess their hazard potential. The present study aimed at evaluating the applicability of a genotoxicity assay based on the immunostaining and foci counting of the DNA repair protein 53BP1 (p53-binding protein 1), in a high-throughput format, for NM genotoxicity assessment. For benchmarking purposes, we first applied the assay to a set of eight known genotoxic agents, as well as X-ray irradiation (1 Gy). Then, a panel of NMs and nanobiomaterials (NBMs) was evaluated with respect to their impact on cell viability and genotoxicity, and to their potential to induce reactive oxygen species (ROS) production. The genotoxicity recorded using the 53BP1 assay was confirmed using the micronucleus assay, also scored via automated (high-throughput) microscopy. The 53BP1 assay successfully identified genotoxic compounds on the HCT116 human intestinal cell line. None of the tested NMs showed any genotoxicity using the 53BP1 assay, except the positive control consisting in (CoO)(NiO) NMs, while only TiO2 NMs showed positive outcome in the micronucleus assay. Only Fe3O4 NMs caused significant elevation of ROS, not correlated to DNA damage. Therefore, owing to its adequate predictivity of the genotoxicity of most of the tested benchmark substance and its ease of implementation in a high throughput format, the 53BP1 assay could be proposed as a complementary high-throughput screening genotoxicity assay, in the context of the development of New Approach Methodologies.

Targeting endothelial permeability in the EPR effect

The characteristics of the primary tumor blood vessels and the tumor microenvironment drive the enhanced permeability and retention (EPR) effect, which confers an advantage towards enhanced delivery of anti-cancer nanomedicine and has shown beneficial effects in preclinical models. Increased vascular permeability is a landmark feature of the tumor vessels and an important driver of the EPR. The main focus of this review is the endothelial regulation of vascular permeability. We discuss current challenges of targeting vascular permeability towards clinical translation and summarize the structural components and mechanisms of endothelial permeability, the principal mediators and signaling players, the targeted approaches that have been used and their outcomes to date. We also critically discuss the effects of the tumor-infiltrating immune cells, their interplay with the tumor vessels and the impact of immune responses on nanomedicine delivery, the impact of anti-angiogenic and tumor-stroma targeting approaches, and desirable nanoparticle design approaches for greater translational benefit.

Smart Nanocarriers for the Targeted Delivery of Therapeutic Nucleic Acid for Cancer Immunotherapy

A wide variety of therapeutic approaches and technologies for delivering therapeutic agents have been investigated for treating cancer. Recently, immunotherapy has achieved success in cancer treatment. Successful clinical results of immunotherapeutic approaches for cancer treatment were led by antibodies targeting immune checkpoints, and many have advanced through clinical trials and obtained FDA approval. A major opportunity remains for the development of nucleic acid technology for cancer immunotherapy in the form of cancer vaccines, adoptive T-cell therapies, and gene regulation. However, these therapeutic approaches face many challenges related to their delivery to target cells, including their in vivo decay, the limited uptake by target cells, the requirements for nuclear penetration (in some cases), and the damage caused to healthy cells. These barriers can be avoided and resolved by utilizing advanced smart nanocarriers (e.g., lipids, polymers, spherical nucleic acids, metallic nanoparticles) that enable the efficient and selective delivery of nucleic acids to the target cells and/or tissues. Here, we review studies that have developed nanoparticle-mediated cancer immunotherapy as a technology for cancer patients. Moreover, we also investigate the crosstalk between the function of nucleic acid therapeutics in cancer immunotherapy, and we discuss how nanoparticles can be functionalized and designed to target the delivery and thus improve the efficacy, toxicity, and stability of these therapeutics.

Polymer-based drug delivery systems under investigation for enzyme replacement and other therapies of lysosomal storage disorders

Lysosomes play a central role in cellular homeostasis and alterations in this compartment associate with many diseases. The most studied example is that of lysosomal storage disorders (LSDs), a group of 60 + maladies due to genetic mutations affecting lysosomal components, mostly enzymes. This leads to aberrant intracellular storage of macromolecules, altering normal cell function and causing multiorgan syndromes, often fatal within the first years of life. Several treatment modalities are available for a dozen LSDs, mostly consisting of enzyme replacement therapy (ERT) strategies. Yet, poor biodistribution to main targets such as the central nervous system, musculoskeletal tissue, and others, as well as generation of blocking antibodies and adverse effects hinder effective LSD treatment. Drug delivery systems are being studied to surmount these obstacles, including polymeric constructs and nanoparticles that constitute the focus of this article. We provide an overview of the formulations being tested, the diseases they aim to treat, and the results observed from respective in vitro and in vivo studies. We also discuss the advantages and disadvantages of these strategies, the remaining gaps of knowledge regarding their performance, and important items to consider for their clinical translation. Overall, polymeric nanoconstructs hold considerable promise to advance treatment for LSDs.

Stealth and pseudo-stealth nanocarriers

The stealth effect plays a central role on capacitating nanomaterials for drug delivery applications through improving the pharmacokinetics such as blood circulation, biodistribution, and tissue targeting. Here based on a practical analysis of stealth efficiency and a theoretical discussion of relevant factors, we provide an integrated material and biological perspective in terms of engineering stealth nanomaterials. The analysis surprisingly shows that more than 85% of the reported stealth nanomaterials encounter a rapid drop of blood concentration to half of the administered dose within 1 h post administration although a relatively long β-phase is observed. A term, pseudo-stealth effect, is used to delineate this common pharmacokinetics behavior of nanomaterials, that is, dose-dependent nonlinear pharmacokinetics because of saturating or depressing bio-clearance of RES. We further propose structural holism can be a watershed to improve the stealth effect; that is, the whole surface structure and geometry play important roles, rather than solely relying on a single factor such as maximizing repulsion force through polymer-based steric stabilization (e.g., PEGylation) or inhibiting immune attack through a bio-inspired component. Consequently, engineering delicate structural hierarchies to minimize attractive binding sites, that is, minimal charges/dipole and hydrophobic domain, becomes crucial. In parallel, the pragmatic implementation of the pseudo-stealth effect and dynamic modulation of the stealth effect are discussed for future development.

CYRI proteins: controllers of actin dynamics in the cellular 'eat vs walk' decision

Cells use actin-based protrusions not only to migrate, but also to sample their environment and take up liquids and particles, including nutrients, antigens and pathogens. Lamellipodia are sheet-like actin-based protrusions involved in sensing the substratum and directing cell migration. Related structures, macropinocytic cups, arise from lamellipodia ruffles and can take in large gulps of the surrounding medium. How cells regulate the balance between using lamellipodia for migration and macropinocytosis is not yet well understood. We recently identified CYRI proteins as RAC1-binding regulators of the dynamics of lamellipodia and macropinocytic events. This review discusses recent advances in our understanding of how cells regulate the balance between eating and walking by repurposing their actin cytoskeletons in response to environmental cues.

Small interfering RNA-based nanotherapeutics for treating skin-related diseases

INTRODUCTION

RNA interference (RNAi) has demonstrated great potential in treating skin-related diseases, as small interfering RNA (siRNA) can efficiently silence specific genes. The design of skin delivery systems for siRNA is important to protect the nucleic acid while facilitating both skin targeting and cellular ingestion. Entrapment of siRNA into nanocarriers can accomplish these aims, contributing to improved targeting, controlled release, and increased transfection.

AREAS COVERED

The siRNA-based nanotherapeutics for treating skin disorders are summarized. First, the mechanisms of RNAi are presented, followed by the introduction of challenges for skin therapy. Then, the different nanoparticle types used for siRNA skin delivery are described. Subsequently, we introduce the mechanisms of how nanoparticles enhance siRNA skin penetration. Finally, the current investigations associated with nanoparticulate siRNA application in skin disease management are reviewed.

EXPERT OPINION

The potential application of nanotherapeutic RNAi allows for a novel skin application strategy. Further clinical studies are required to confirm the findings in the cell-based or animal experiments. The capability of large-scale production and reproducibility of nanoparticle products are also critical for translation to commercialization. siRNA delivery by nanocarriers should be optimized to attain cutaneous targeting without the risk of toxicity.

Self-delivery photodynamic-hypoxia alleviating nanomedicine synergizes with anti-PD-L1 for cancer immunotherapy

The low level of T-lymphocyte infiltration in tumor is a key issue in cancer immunotherapy. Stimulating anti-tumor immune responses and improving the tumor microenvironment are essential for enhancing anti-PD-L1 immunotherapy. Herein, atovaquone (ATO), protoporphyrin IX (PpIX), and stabilizer (ATO/PpIX NPs) were constructed to self-assemble with hydrophobic interaction and passively targeted to tumor for the first time. The studies have indicated that PpIX-mediated photodynamic induction of immunogenic cell death combined with relieving tumor hypoxia by ATO, leading to maturation of dendritic cells, polarization of M2-type tumor-associated macrophages (TAMs) towards M1-type TAMs, infiltration of cytotoxic T lymphocytes, reduction of regulatory T cells, release of pro-inflammatory cytokines, resulting in an effective anti-tumor immune response synergized with anti-PD-L1 against primary tumor and pulmonary metastasis. Taken together, the combined nanoplatform may be a promising strategy to enhance cancer immunotherapy.

The steep road to nonviral nanomedicines: Frequent challenges and culprits in designing nanoparticles for gene therapy

The potential of therapeutically loaded nanoparticles (NPs) has been successfully demonstrated during the last decade, with NP-mediated nonviral gene delivery gathering significant attention as highlighted by the broad clinical acceptance of mRNA-based COVID-19 vaccines. A significant barrier to progress in this emerging area is the wild variability of approaches reported in published literature regarding nanoparticle characterizations. Here, we provide a brief overview of the current status and outline important concerns regarding the need for standardized protocols to evaluate NP uptake, NP transfection efficacy, drug dose determination, and variability of nonviral gene delivery systems. Based on these concerns, we propose wide adherence to multimodal, multiparameter, and multistudy analysis of NP systems. Adoption of these proposed approaches will ensure improved transparency, provide a better basis for interlaboratory comparisons, and will simplify judging the significance of new findings in a broader context, all critical requirements for advancing the field of nonviral gene delivery.

Endocytosis-mediated redistribution of antibiotics targets intracellular bacteria

The increasing emergence and dissemination of antibiotic resistance pose a severe threat to overwhelming healthcare practices worldwide. The lack of new antibacterial drugs urgently calls for alternative therapeutic strategies to combat multidrug-resistant (MDR) bacterial pathogens, especially those that survive and replicate in host cells, causing relapse and recurrence of infections. Intracellular drug delivery is a direct efficient strategy to combat invasive pathogens by increasing the accumulation of antibiotics. However, the increased accumulation of antibiotics in the infected host cells does not mean high efficacy. The difficulty of treatment lies in the efficient intracellular delivery of antibiotics to the pathogen-containing compartments. Here, we first briefly review the survival mechanisms of intracellular bacteria to facilitate the exploration of potential antibacterial targets for precise delivery. Furthermore, we provide an overview of endocytosis-mediated drug delivery systems, including the biomedical and physicochemical properties modulating the endocytosis and intracellular redistribution of antibiotics. Lastly, we summarize the targets and payloads of recently described intracellular delivery systems and their modes of action against diverse pathogenic bacteria-associated infections. This overview of endocytosis-mediated redistribution of antibiotics sheds light on the development of novel delivery platforms and alternative strategies to combat intracellular bacterial pathogens.

Influence of Folate-Targeted Gold Nanoparticles on Subcellular Localization and Distribution into Lysosomes

The cell interaction, mechanism of cell entry and intracellular fate of surface decorated nanoparticles are known to be affected by the surface density of targeting agents. However, the correlation between nanoparticles multivalency and kinetics of the cell uptake process and disposition of intracellular compartments is complicated and dependent on a number of physicochemical and biological parameters, including the ligand, nanoparticle composition and colloidal properties, features of targeted cells, etc. Here, we have carried out an in-depth investigation on the impact of increasing folic acid density on the kinetic uptake process and endocytic route of folate (FA)-targeted fluorescently labelled gold nanoparticles (AuNPs). A set of AuNPs (15 nm mean size) produced by the Turkevich method was decorated with 0–100 FA-PEG3.5kDa-SH molecules/particle, and the surface was saturated with about 500 rhodamine-PEG2kDa-SH fluorescent probes. In vitro studies carried out using folate receptor overexpressing KB cells (KBFR-high) showed that the cell internalization progressively increased with the ligand surface density, reaching a plateau at 50:1 FA-PEG3.5kDa-SH/particle ratio. Pulse-chase experiments showed that higher FA density (50 FA-PEG3.5kDa-SH molecules/particle) induces more efficient particle internalization and trafficking to lysosomes, reaching the maximum concentration in lysosomes at 2 h, than the lower FA density of 10 FA-PEG3.5kDa-SH molecules/particle. Pharmacological inhibition of endocytic pathways and TEM analysis showed that particles with high folate density are internalized predominantly by a clathrin-independent process.

Dual Immunostimulatory Pathway Agonism through a Synthetic Nanocarrier Triggers Robust Anti-Tumor Immunity in Murine Glioblastoma

Myeloid cells are abundant, create a highly immunosuppressive environment in glioblastoma (GBM), and thus contribute to poor immunotherapy responses. Based on the hypothesis that small molecules can be used to stimulate myeloid cells to elicit anti-tumor effector functions, a synthetic nanoparticle approach is developed to deliver dual NF-kB pathway-inducing agents into these cells via systemic administration. Synthetic, cyclodextrin-adjuvant nanoconstructs (CANDI) with high affinity for tumor-associated myeloid cells are dually loaded with a TLR7 and 8 (Toll-like receptor, 7 and 8) agonist (R848) and a cIAP (cellular inhibitor of apoptosis protein) inhibitor (LCL-161) to dually activate these myeloid cells. Here CANDI is shown to: i) readily enter the GBM tumor microenvironment (TME) and accumulate at high concentrations, ii) is taken up by tumor-associated myeloid cells, iii) potently synergize payloads compared to monotherapy, iv) activate myeloid cells, v) fosters a "hot" TME with high levels of T effector cells, and vi) controls the growth of murine GBM as mono- and combination therapies with anti-PD1. Multi-pathway targeted myeloid stimulation via the CANDI platform can efficiently drive anti-tumor immunity in GBM.

A noncanonical endocytic pathway is involved in the internalization of 3 μm polystyrene beads into HeLa cells

Extracellular fine particles of various sizes and origins can be taken up by cells, affecting their function. Understanding the cellular uptake processes is crucial for understanding the cellular effects of these particles and the development of means to control their internalization. Although macropinocytosis is a possible pathway for the cellular uptake of particles larger than 0.2 μm, its contribution to cellular uptake in non-phagocytic cells is controversial. Using 3 μm polystyrene beads as a model particle, we aimed to assess the detailed modes of their cellular uptake by non-phagocytic HeLa cells. Cellular uptake was assessed using confocal, scanning electron, and scanning ion conductance microscopy analyses, together with inhibitor studies. Our results revealed that 3 μm beads were taken up by HeLa cells by an actin-, cholesterol-, and membrane protrusions-dependent noncanonical endocytic pathway, different from the canonical macropinocytic and phagocytic pathways. Our work provides a framework for studying the cellular uptake of extracellular fine particles.

The engineering challenges and opportunities when designing potent ionizable materials for the delivery of ribonucleic acids

INTRODUCTION

Ionizable lipids are critical components in lipid nanoparticles. These molecules sequester nucleic acids for delivery to cells. However, to build more efficacious delivery molecules, the field must continue to broaden structure-function studies for greater insight. While nucleic acid-binding efficiency, degradability and nanoparticle stability are vitally important, this review offers perspective on additional factors that must be addressed to improve delivery efficiency.

AREAS COVERED

We discuss how administration route, cellular heterogeneity, uptake pathway, endosomal escape timing, age, sex, and threshold effects can change depending on the type of LNP ionizable lipid.

EXPERT OPINION

Ionizable lipid structure-function studies often focus on the efficiency of RNA utilization and biodistribution. While these focus areas are critical, they remain high-level observations. As our tools for observation and system interrogation improve, we believe that the field should begin collecting additional data. At the cellular level, this data should include age (dividing or senescent cells), sex and phenotype, cell entry pathway, and endosome type. Additionally, administration route and dose are essential to track. This additional data will allow us to identify and understand heterogeneity in LNP efficacy across patient populations, which will help us provide better ionizable lipid options for different groups.

Lack of mutagenicity of TiO2 nanoparticles in vitro despite cellular and nuclear uptake

The potential genotoxicity of titanium dioxide (TiO₂) nanoparticles (NPs) is a conflictive topic because both positive and negative findings have been reported. To add clarity, we have carried out a study with two cell lines (V79-4 and A549) to evaluate the effects of TiO₂ NPs (NM-101), with a diameter ranging from 15 to 60 nm, at concentrations 1-75 μg/cm². Using two different dispersion procedures, cell uptake was determined by Transmission Electron Microscopy (TEM). Mutagenicity was evaluated using the Hprt gene mutation test, while genotoxicity was determined with the comet assay, detecting both DNA breaks and oxidized DNA bases (with formamidopyrimidine glycosylase - Fpg). Cell internalization, as determined by TEM, shows TiO₂ NM-101 in cytoplasmic vesicles, as well as close to and inside the nucleus. Such internalization did not depend on the state of agglomeration, nor the dispersion used. In spite of such internalization, no cytotoxicity was detected in V79-4 cells (relative growth activity and plating efficiency assays) or in A549 cells (AlamarBlue assay) after exposure lasting for 24 h. However, a significant decrease in the relative growth activity was detected at longer exposure times (48 and 72 h) and at the highest concentration 75 µg/cm². When the modified enzyme-linked alkaline comet assay was performed on A549 cells, although no significant induction of DNA damage was detected, a positive concentration-effects relationship was observed (Spearman's correlation = 0.9, p 0.0001). Furthermore, no significant increase of DNA oxidized purine bases was observed. When the frequency of Hprt gene mutants was determined in V79-4 cells, no increase was observed in the exposed cells, relative to the unexposed cultures. Our general conclusion is that, under our experimental conditions, TiO₂ NM-101 exposure does not exert mutagenic effects despite the evidence of NP uptake by V79-4 cells.