It’s what’s on the inside that counts: Techniques for investigating the uptake and recycling of nanoparticles and proteins in cells

Critical evaluation of the potential of ICP-MS-based systems in toxicological studies of metallic nanoparticles

The extensive application of metallic nanoparticles (NPs) in several fields has significantly impacted our daily lives. Nonetheless, uncertainties persist regarding the toxicity and potential risks associated with the vast number of NPs entering the environment and human bodies, so the performance of toxicological studies are highly demanded. While traditional assays focus primarily on the effects, the comprehension of the underlying processes requires innovative analytical approaches that can detect, characterize, and quantify NPs in complex biological matrices. Among the available alternatives to achieve this information, mass spectrometry, and more concretely, inductively coupled plasma mass spectrometry (ICP-MS), has emerged as an appealing option. This work critically reviews the valuable contribution of ICP-MS-based techniques to investigate NP toxicity and their transformations during in vitro and in vivo toxicological assays. Various ICP-MS modalities, such as total elemental analysis, single particle or single-cell modes, and coupling with separation techniques, as well as the potential of laser ablation as a spatially resolved sample introduction approach, are explored and discussed. Moreover, this review addresses limitations, novel trends, and perspectives in the field of nanotoxicology, particularly concerning NP internalization and pathways. These processes encompass cellular uptake and quantification, localization, translocation to other cell compartments, and biological transformations. By leveraging the capabilities of ICP-MS, researchers can gain deeper insights into the behaviour and effects of NPs, which can pave the way for safer and more responsible use of these materials.

Alveolar-capillary endocytosis and trafficking in acute lung injury and acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is associated with high morbidity and mortality but lacks specific therapeutic options. Diverse endocytic processes play a key role in all phases of acute lung injury (ALI), including the initial insult, development of respiratory failure due to alveolar flooding, as a consequence of altered alveolar-capillary barrier function, as well as in the resolution or deleterious remodeling after injury. In particular, clathrin-, caveolae-, endophilin- and glycosylphosphatidyl inositol-anchored protein-mediated endocytosis, as well as, macropinocytosis and phagocytosis have been implicated in the setting of acute lung damage. This manuscript reviews our current understanding of these endocytic pathways and subsequent intracellular trafficking in various phases of ALI, and also aims to identify potential therapeutic targets for patients with ARDS.

Effects of Drug Conjugation on the Biological Activity of Single-Chain Nanoparticles

The field of single-chain nanoparticles (SCNPs) continues to mature, and an increasing range of reports have emerged that explore the application of these small nanoparticles. A key application for SCNPs is in the field of drug delivery, and recent work suggests that SCNPs can be readily internalized by cells. However, limited attention has been directed to the delivery of small-molecule drugs using SCNPs. Moreover, studies on the physicochemical effects of drug loading on SCNP performance is so far missing, despite the accepted view that such small nanoparticles should be significantly affected by the drug loading content. To address this gap, we prepared a library of SCNPs bearing different amounts of a covalently conjugated therapeutic drug-sulfasalazine (SSZ). We evaluated the impact of the conjugated drug loading on both the synthesis and biological activity of SCNPs on pancreatic cancer cells (AsPC-1). Our results reveal that covalent drug conjugation to the side chains of the SCNP polymer precursor interferes with chain collapse and cross-linking, which demands optimization of reaction conditions to reach high degrees of cross-linking efficiencies. Small-angle neutron scattering and diffusion-ordered spectroscopy nuclear magnetic resonance (DOSY NMR) analyses reveal that SCNPs with a higher drug loading display larger sizes and looser structures, as well as increased hydrophobicity associated with a higher SSZ content. Increased SSZ loading led to reduced cellular uptake when assessed in vitro, whereby SCNP aggregation on the surface of AsPC-1 cells led to reduced toxicity. This work highlights the effects of drug loading on the drug delivery efficiency and biological behavior of SCNPs.

Antibodies internalization mechanisms by dendritic cells and their role in therapeutic antibody immunogenicity

Internalization and processing by antigen-presenting cells such as dendritic cells (DCs) are critical steps for initiating a T-cell response to therapeutic antibodies. Consequences are the production of neutralizing antidrug antibodies altering the clinical response, the presence of immune complexes, and, in some rare cases, hypersensitivity reactions. In recent years, significant progress has been made in the knowledge of cellular uptake mechanisms of antibodies in DCs. The uptake of antibodies could be directly related to their immunogenicity by regulating the quantity of materials entering the DCs in relation to antibody structure. Here, we summarize the latest insights into cellular uptake mechanisms and pathways in DCs. We highlight the approaches to study endocytosis, the impact of endocytosis routes on T-cell response, and discuss the link between how DCs internalize therapeutic antibodies and the potential mechanisms that could give rise to immunogenicity. Understanding these processes could help in developing assays to evaluate the immunogenicity potential of biotherapeutics.

Accurate Quantification and Imaging of Cellular Uptake Using Single-Particle Surface-Enhanced Raman Scattering

Understanding the uptake, distribution, and stability of gold nanoparticles (NPs) in cells is of fundamental importance in nanoparticle sensors and therapeutic development. Single nanoparticle imaging with surface-enhanced Raman spectroscopy (SERS) measurements in cells is complicated by aggregation-dependent SERS signals, particle inhomogeneity, and limited single-particle brightness. In this work, we assess the single-particle SERS signals of various gold nanoparticle shapes and the role of silica encapsulation on SERS signals to develop a quantitative probe for single-particle level Raman imaging in living cells. We observe that silica-encapsulated gap-enhanced Raman tags (GERTs) provide an optimized probe that can be quantifiable per voxel in SERS maps of cells. This approach is validated by single-particle inductively coupled mass spectrometry (spICP-MS) measurements of NPs in cell lysate post-imaging. spICP-MS also provides a means of measuring the tag stability. This analytical approach can be used not only to quantitatively assess nanoparticle uptake on the cellular level (as in previous digital SERS methods) but also to reliably image the subcellular distribution and to assess the stability of NPs in cells.

Timing of Phagosome Maturation Depends on Their Transport Switching from Actin to Microtubule Tracks

Phagosomes, specialized membrane compartments responsible for digesting internalized pathogens, undergo sequential dynamic and biochemical changes as they mature from nascent phagosomes to degradative phagolysosomes. Maturation of phagosomes depends on their transport along actin filaments and microtubules. However, the specific quantitative relationship between the biochemical transformation and transport dynamics remains poorly characterized. The autonomous nature of phagosomes, moving and maturing at different rates, makes understanding this relationship challenging. Addressing this challenge, in this study we engineered particle sensors to image and quantify single phagosomes' maturation. We found that as phagosomes move from the actin cortex to microtubule tracks, the timing of their actin-to-microtubule transition governs the duration of the early phagosome stage before acquiring degradative capacities. Prolonged entrapment of phagosomes in the actin cortex extends the early phagosome stage by delaying the dissociation of early endosome markers and phagosome acidification. Conversely, a shortened transition from actin- to microtubule-based movements causes the opposite effect on phagosome maturation. These results suggest that the actin- and microtubule-based transport of phagosomes functions like a "clock" to coordinate the timing of biochemical events during phagosome maturation, which is crucial for effective pathogen degradation.

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.

Cellular uptake of biotransformed graphene oxide into lung cells

Due to its high surface area and convenient functionalization, graphene oxide has many potential applications in biomedicine, especially as a drug carrier. However, knowledge about its internalization inside mammalian cells is still limited. Graphene oxide cellular uptake is a complex phenomenon affected by factors such as the size of the particle and modifications of its surface. Moreover, nanomaterials introduced into living organisms interact with biological fluids' components. It may further alter its biological properties. All these factors must be considered when the cellular uptake of potential drug carriers is considered. In this study, the effect of graphene oxide particle sizes on internalization efficiency into normal (LL-24) and cancerous (A549) human lung cells was investigated. Moreover, one set of samples was incubated with human serum to determine how the interaction of graphene oxide with serum components affects its structure, surface, and interaction with cells. Our findings indicate that samples incubated with serum enhance cell proliferation but enter the cells with lesser efficiency than their counterparts not incubated with human serum. What is more affinity towards the cells was higher for larger particles.

Investigating nanoplastics toxicity using advanced stem cell-based intestinal and lung in vitro models

Plastic particles in the nanometer range-called nanoplastics-are environmental contaminants with growing public health concern. As plastic particles are present in water, soil, air and food, human exposure via intestine and lung is unavoidable, but possible health effects are still to be elucidated. To better understand the Mode of Action of plastic particles, it is key to use experimental models that best reflect human physiology. Novel assessment methods like advanced cell models and several alternative approaches are currently used and developed in the scientific community. So far, the use of cancer cell line-based models is the standard approach regarding in vitro nanotoxicology. However, among the many advantages of the use of cancer cell lines, there are also disadvantages that might favor other approaches. In this review, we compare cell line-based models with stem cell-based in vitro models of the human intestine and lung. In the context of nanoplastics research, we highlight the advantages that come with the use of stem cells. Further, the specific challenges of testing nanoplastics in vitro are discussed. Although the use of stem cell-based models can be demanding, we conclude that, depending on the research question, stem cells in combination with advanced exposure strategies might be a more suitable approach than cancer cell lines when it comes to toxicological investigation of nanoplastics.

Deep Learning-Based Artificial Intelligence to Investigate Targeted Nanoparticles' Uptake in TNBC Cells

Triple negative breast cancer (TNBC) is the most aggressive subtype of breast cancer in women. It has the poorest prognosis along with limited therapeutic options. Smart nano-based carriers are emerging as promising approaches in treating TNBC due to their favourable characteristics such as specifically delivering different cargos to cancer cells. However, nanoparticles' tumour cell uptake, and subsequent drug release, are essential factors considered during the drug development process. Contemporary qualitative analyses based on imaging are cumbersome and prone to human biases. Deep learning-based algorithms have been well-established in various healthcare settings with promising scope in drug discovery and development. In this study, the performance of five different convolutional neural network models was evaluated. In this research, we investigated two sequential models from scratch and three pre-trained models, VGG16, ResNet50, and Inception V3. These models were trained using confocal images of nanoparticle-treated cells loaded with a fluorescent anticancer agent. Comparative and cross-validation analyses were further conducted across all models to obtain more meaningful results. Our models showed high accuracy in predicting either high or low drug uptake and release into TNBC cells, indicating great translational potential into practice to aid in determining cellular uptake at the early stages of drug development in any area of research.

On predicting heterogeneity in nanoparticle dosage

Nanoparticles are increasingly employed as a vehicle for the targeted delivery of therapeutics to specific cell types. However, much remains to be discovered about the fundamental biology that dictates the interactions between nanoparticles and cells. Accordingly, few nanoparticle-based targeted therapeutics have succeeded in clinical trials. One element that hinders our understanding of nanoparticle-cell interactions is the presence of heterogeneity in nanoparticle dosage data obtained from standard experiments. It is difficult to distinguish between heterogeneity that arises from stochasticity in nanoparticle-cell interactions, and that which arises from heterogeneity in the cell population. Mathematical investigations have revealed that both sources of heterogeneity contribute meaningfully to the heterogeneity in nanoparticle dosage. However, these investigations have relied on simplified models of nanoparticle internalisation. Here we present a stochastic mathematical model of nanoparticle internalisation that incorporates a suite of relevant biological phenomena such as multistage internalisation, cell division, asymmetric nanoparticle inheritance and nanoparticle saturation. Critically, our model provides information about nanoparticle dosage at an individual cell level. We perform model simulations to examine the influence of specific biological phenomena on the heterogeneity in nanoparticle dosage in the absence of heterogeneity in the cell population. Under certain modelling assumptions, we derive analytic approximations of the nanoparticle dosage distribution. We demonstrate that the analytic approximations are accurate, and show that nanoparticle dosage can be described by a Poisson mixture distribution with rate parameters that are a function of Beta-distributed random variables. We discuss the implications of the analytic results with respect to parameter estimation and model identifiability from standard experimental data. Finally, we highlight extensions and directions for future research.

Equation learning to identify nano-engineered particle-cell interactions: an interpretable machine learning approach

Designing nano-engineered particles capable of the delivery of therapeutic and diagnostic agents to a specific target remains a significant challenge. Understanding how interactions between particles and cells are impacted by the physicochemical properties of the particle will help inform rational design choices. Mathematical and computational techniques allow for details regarding particle-cell interactions to be isolated from the interwoven set of biological, chemical, and physical phenomena involved in the particle delivery process. Here we present a machine learning framework capable of elucidating particle-cell interactions from experimental data. This framework employs a data-driven modelling approach, augmented by established biological knowledge. Crucially, the model of particle-cell interactions learned by the framework can be interpreted and analysed, in contrast to the 'black box' models inherent to other machine learning approaches. We apply the framework to association data for thirty different particle-cell pairs. This library of data contains both adherent and suspension cell lines, as well as a diverse collection of particles. We consider hyperbranched polymer and poly(methacrylic acid) particles, from 6 nm to 1032 nm in diameter, with small molecule, monoclonal antibody, and peptide surface functionalisations. Despite the diverse nature of the experiments, the learned models of particle-cell interactions for each particle-cell pair are remarkably consistent: out of 2048 potential models, only four unique models are learned. The models reveal that nonlinear saturation effects are a key feature governing particle-cell interactions. Further, the framework provides robust estimates of particle performance, which facilitates quantitative evaluation of particle design choices.

Kinetics of phagosome maturation is coupled to their intracellular motility

Immune cells degrade internalized pathogens in phagosomes through sequential biochemical changes. The degradation must be fast enough for effective infection control. The presumption is that each phagosome degrades cargos autonomously with a distinct but stochastic kinetic rate. However, here we show that the degradation kinetics of individual phagosomes is not stochastic but coupled to their intracellular motility. By engineering RotSensors that are optically anisotropic, magnetic responsive, and fluorogenic in response to degradation activities in phagosomes, we monitored cargo degradation kinetics in single phagosomes simultaneously with their translational and rotational dynamics. We show that phagosomes that move faster centripetally are more likely to encounter and fuse with lysosomes, thereby acidifying faster and degrading cargos more efficiently. The degradation rates increase nearly linearly with the translational and rotational velocities of phagosomes. Our results indicate that the centripetal motion of phagosomes functions as a clock for controlling the progression of cargo degradation.

A pH-stable, mucin based nanoparticle system for the co-delivery of hydrophobic and hydrophilic drugs

Biopolymer-based drug carriers are commonly used for the development of safe delivery systems. However, biopolymer-based systems are often highly sensitive to the acidic pH levels in the stomach and release most of their cargo before they have reached their point of destination. Such premature drug release combined with the resulting high dose requirements is not cost-efficient and comes with the risk of unwanted side effects on non-target tissues/organs. This problem can be mitigated by the mucin-based drug carriers developed here, which exhibit good stability at acidic pH levels as proven by dynamic light scattering and enzymatic degradation tests with pepsin. In addition, the mucin-based particles can deliver hydrophobic and hydrophilic drugs simultaneously, which is demonstrated both with experiments performed under in vitro sink conditions and with drug transport tests involving eukaryotic cells as targets. As photo-induced cross-links covalently stabilize those particles, they can release their payload over time in a sustained manner. The drug carrier system introduced here combines good stability with high drug encapsulation efficiency and very good biocompatibility and thus may be valuable for a broad spectrum of applications in biological settings.

Identifying cell-to-cell variability in internalization using flow cytometry

Biological heterogeneity is a primary contributor to the variation observed in experiments that probe dynamical processes, such as the internalization of material by cells. Given that internalization is a critical process by which many therapeutics and viruses reach their intracellular site of action, quantifying cell-to-cell variability in internalization is of high biological interest. Yet, it is common for studies of internalization to neglect cell-to-cell variability. We develop a simple mathematical model of internalization that captures the dynamical behaviour, cell-to-cell variation, and extrinsic noise introduced by flow cytometry. We calibrate our model through a novel distribution-matching approximate Bayesian computation algorithm to flow cytometry data of internalization of anti-transferrin receptor antibody in a human B-cell lymphoblastoid cell line. This approach provides information relating to the region of the parameter space, and consequentially the nature of cell-to-cell variability, that produces model realizations consistent with the experimental data. Given that our approach is agnostic to sample size and signal-to-noise ratio, our modelling framework is broadly applicable to identify biological variability in single-cell data from internalization assays and similar experiments that probe cellular dynamical processes.

Photosensitizer Encryption with Aggregation Enhanced Singlet Oxygen Production

Chromophores that generate singlet oxygen (¹O₂) in water are essential to developing noninvasive disease treatments using photodynamic therapy (PDT). A facile approach for formation of stable colloidal nanoparticles of ¹O₂ photosensitizers, which exhibit aggregation enhanced ¹O₂ generation in water toward applications as PDT agents, is reported. Chromophore encryption within a fuchsonarene macrocyclic scaffold insulates the photosensitizer from aggregation induced deactivation pathways, enabling a higher chromophore density than typical ¹O₂ generating nanoparticles. Aggregation enhanced ¹O₂ generation in water is observed, and variation in molecular structure allows for regulation of the physical properties of the nanoparticles which ultimately affects the ¹O₂ generation. In vitro activity and the ability of the particles to pass through the cell membrane into the cytoplasm is demonstrated using confocal fluorescence microscopy with HeLa cells. Photosensitizer encryption in rigid macrocycles, such as fuchsonarenes, offers new prospects for the production of biocompatible nanoarchitectures for applications involving ¹O₂ generation.

Quantification of silver nanoparticle interactions with yeast Saccharomyces cerevisiae studied using single-cell ICP-MS

Silver nanoparticles (AgNPs) have been used in many fields due to their anticancer, antimicrobial, and antiviral potential. Single-cell ICP-MS (SC-ICP-MS) is an emerging technology that allows for the rapid characterization and quantification of a metal analyte across a cell population in a single analysis. In this study, a new rapid and sensitive SC-ICP-MS method was developed to quantitatively study the interactions of AgNPs with yeast Saccharomyces cerevisiae. The method can quantify the cell concentration, silver concentration per cell, and profile the nanoparticle distribution in a yeast cell population. AgNP dosing time, concentration, and AgNP size were quantitatively evaluated for their effects on AgNP-yeast cell interactions. The results showed that the initial uptake of AgNPs was rapid and primarily driven by the mass of Ag per cell. The optimal dosing particle concentrations for highest uptake were approximately 1820, 1000, and 300 AgNPs/cell for 10, 20, and 40 nm AgNPs, respectively. Furthermore, this study also validated a washing method for the application to a microorganism for the first time and was used to quantitatively determine the amount of cell surface-adsorbed AgNPs and intracellular AgNPs. These results indicated that the mass (Ag in ag/cell) ratios of intracelluar vs cell surface-adsorbed AgNPs were similar for different AgNP sizes. This high throughput and ultrasensitive SC-ICP-MS method is expected to have many potential applications, such as optimization of methods for green synthesis of AgNPs, nanotoxicity studies, and drug delivery. This is the first quantification study on the interactions of AgNPs and S. cerevisiae using SC-ICP-MS.

Approaches to Visualising Endocytosis of LDL-Related Lipoproteins

Endocytosis is the process by which molecules are actively transported into cells. It can take on a variety of forms depending on the cellular machinery involved ranging from specific receptor-mediated endocytosis to the less selective and actin-driven macropinocytosis. The plasma lipoproteins, which deliver lipids and other cargo to cells, have been intensely studied with respect to their endocytic uptake. One of the first molecules to be visualised undergoing endocytosis via a receptor-mediated, clathrin-dependent pathway was low-density lipoprotein (LDL). The LDL molecule has subsequently been shown to be internalised through multiple endocytic pathways. Dissecting the pathways of lipoprotein endocytosis has been crucial to understanding the regulation of plasma lipid levels and how lipids enter cells in the arterial wall to promote atherosclerosis. It has also aided understanding of the dysregulation that occurs in plasma lipid levels when molecules involved in uptake are defective, as is the case in familial hypercholesterolemia (FH). The aim of this review is to outline the many endocytic pathways utilised for lipoprotein uptake. It explores the various experimental approaches that have been applied to visualise lipoprotein endocytosis with an emphasis on LDL and its more complex counterpart, lipoprotein(a) [Lp(a)]. Finally, we look at new developments in lipoprotein visualisation that hold promise for scrutinising endocytic pathways to finer detail in the future.

Transmission Electron Microscopy as a Powerful Tool to Investigate the Interaction of Nanoparticles with Subcellular Structures

Nanomedical research necessarily involves the study of the interactions between nanoparticulates and the biological environment. Transmission electron microscopy has proven to be a powerful tool in providing information about nanoparticle uptake, biodistribution and relationships with cell and tissue components, thanks to its high resolution. This article aims to overview the transmission electron microscopy techniques used to explore the impact of nanoconstructs on biological systems, highlighting the functional value of ultrastructural morphology, histochemistry and microanalysis as well as their fundamental contribution to the advancement of nanomedicine.

Do Lipid-based Nanoparticles Hold Promise for Advancing the Clinical Translation of Anticancer Alkaloids?

Since the commercialization of morphine in 1826, numerous alkaloids have been isolated and exploited effectively for the betterment of mankind, including cancer treatment. However, the commercialization of alkaloids as anticancer agents has generally been limited by serious side effects due to their lack of specificity to cancer cells, indiscriminate tissue distribution and toxic formulation excipients. Lipid-based nanoparticles represent the most effective drug delivery system concerning clinical translation owing to their unique, appealing characteristics for drug delivery. To the extent of our knowledge, this is the first review to compile in vitro and in vivo evidence of encapsulating anticancer alkaloids in lipid-based nanoparticles. Alkaloids encapsulated in lipid-based nanoparticles have generally displayed enhanced in vitro cytotoxicity and an improved in vivo efficacy and toxicity profile than free alkaloids in various cancers. Encapsulated alkaloids also demonstrated the ability to overcome multidrug resistance in vitro and in vivo. These findings support the broad application of lipid-based nanoparticles to encapsulate anticancer alkaloids and facilitate their clinical translation. The review then discusses several limitations of the studies analyzed, particularly the discrepancies in reporting the pharmacokinetics, biodistribution and toxicity data. Finally, we conclude with examples of clinically successful encapsulated alkaloids that have received regulatory approval and are undergoing clinical evaluation.

Development and characterization of inhalable transferrin functionalized amodiaquine nanoparticles - Efficacy in Non-Small Cell Lung Cancer (NSCLC) treatment

New drug discovery and development processes encounter significant challenges including requirement of huge investments and lengthy time frames especially in cancer research field. Repurposing of old drugs against cancer provides a possible alternative while associated scale-up complexities with production of nanoparticles at industrial scale could be overcome by using a scalable nanoparticle technique. We previously described use of polymeric nanoparticles for inhaled delivery of amodiaquine (AQ) for non-small cell lung cancer (NSCLC) treatment. In this study, targeting potential of transferrin ligand conjugated inhalable AQ-loaded nanoparticles (Tf-AMQ NPs) was investigated against NSCLC. Tf-AMQ NP (liquid formulation) demonstrated an aerodynamic diameter of 4.4 ± 0.1 µm and fine particle fraction of 83.2 ± 3.0%, representing AQ deposition in the respirable region of airways. Cytotoxicity studies in NSCLC cell line with overexpressed transferrin receptors shown significant reduction in IC₅₀ values with Tf-decorated AQ-loaded nanoparticles compared to AQ or non-targeted NPs, along with significant apoptosis induction (caspase assay) and reduced % colony growth in A549 and H1299 cells with Tf-AMQ NP. Furthermore, 3D spheroid studies (~7-fold reduction in spheroid volume compared to AMQ NPs) explained efficiency of conjugated nanoparticles in penetrating tumor core, and growth inhibition. AQ's autophagy inhibition ability significantly increased with nanoparticle encapsulation and transferrin conjugation. In conclusion, amodiaquine can be an assuring candidate for repurposing to consider for NSCLC treatment while delivering inhalable transferrin conjugated nanoparticles developed using a scalable HPH process to the target site, thus reducing the dose, side effects.

VEGF aptamer/i-motif-grafted multi-functional SPION nanocarrier for chemotherapeutic/phototherapeutic synergistic research

Chemotherapeutic agents and photosensitizers often suffer from poor tumor selectivity, high side toxicity, or low water solubility. To address these problems, various drug delivery systems (DDS) have been explored but most of them are toxic, difficult to synthesize, or of single function. In order to design a highly biocompatible, conveniently prepared, multi-functional drug delivery system, herein, an aptamer of vascular endothelial growth factor (VEGF) and a cytosine (C)-DNA fragment were grafted on the surface of superparamagnetic iron oxide nanoparticles (SPION), and then a chemotherapeutic agent daunomycin (DNM) and a photosensitizer 5, 10, 15, 20-tetra (phenyl-4-N-methyl-4-pyridyl) porphyrin (TMPyP) were self-assembled with the hybridized VEGF-based DNA structure. By loading DNM and TMPyP, the DDS displayed strong chemotherapeutic/phototherapeutic capability against cancer cells via mechanisms such as mitochondrial dysfunction and ROS elevation, which triggered the apoptosis of the tumor cells. The dual delivery of chemotherapeutical agents and photosensitizers with aptamer/C-rich DNA successfully integrated the functions of pH stimuli-responsive drug release and chemotherapeutic/phototherapeutic modalities into one single system and thus could be considered as an ideal drug delivery vehicle with great potential in clinic.

Endocytosis of abiotic nanomaterials and nanobiovectors: Inhibition of membrane trafficking

Humans are exposed to nanoscopical nanobiovectors (e.g. coronavirus SARS-CoV-2) as well as abiotic metal/carbon-based nanomaterials that enter cells serendipitously or intentionally. Understanding the interactions of cell membranes with these abiotic and biotic nanostructures will facilitate scientists to design better functional nanomaterials for biomedical applications. Such knowledge will also provide important clues for the control of viral infections and the treatment of virus-induced infectious diseases. In the present review, the mechanisms of endocytosis are reviewed in the context of how nanomaterials are uptaken into cells. This is followed by a detailed discussion of the attributes of man-made nanomaterials (e.g. size, shape, surface functional groups and elasticity) that affect endocytosis, as well as the different human cell types that participate in the endocytosis of nanomaterials. Readers are then introduced to the concept of viruses as nature-derived nanoparticles. The mechanisms in which different classes of viruses interact with various cell types to gain entry into the human body are reviewed with examples published over the last five years. These basic tenets will enable the avid reader to design advanced drug delivery and gene transfer nanoplatforms that harness the knowledge acquired from endocytosis to improve their biomedical efficacy. The review winds up with a discussion on the hurdles to be addressed in mimicking the natural mechanisms of endocytosis in nanomaterials design.

VEGF aptamer/i-motif-based drug co-delivery system for combined chemotherapy and photodynamic therapy

BACKGROUND

Nucleic acids used as drug delivery systems (DDS) have gained attention because of their biosafety and effortless synthesis. G-quadruplex (G4) structured aptamer such as AS1411 was frequently employed to deliver photosensitizers or chemotherapeutic agents while other aptamers were seldomly reported in this field.

METHODS

Herein, a chemical anticancer drug daunomycin (DNM), and a photosensitizer 5, 10, 15, 20-tetra (phenyl-4-N-methyl-4-pyridyl) porphyrin (TMPyP) were physically assembled with a novel DNA structure composed of an aptamer of vascular endothelial growth factor (VEGF) and a cytosine (C)-rich DNA fragment (gc-34). Spectral and molecular mimicking methods were employed to research the drug loading/releasing process. The in vitro cytotoxicity was studied by MTT, ROS, cell cycle, and cell apoptotic assays and the in vivo anticancer efficiency was evaluated by the inhibitive effect on the cancerous growth of MCF-7 tumor-bearing nude mice.

RESULTS

The G4-structured VEGF aptamer delivered TMPyP successfully for the first time. The designed DDS displayed sensitive VEGF/pH controlled drug release. The co-delivery of DNM and TMPyP exhibited high ROS production, significant cell cycle arresting and evident cell apoptosis, and displayed superior cytotoxicity against tumor cells compared with individual agents in vitro. In vivo studies showed that the dual-drug loaded system can greatly inhibit tumor growth with chemotherapeutic/photodynamic synergistic effects.

CONCLUSION

The co-delivery of DNM and TMPyP with aptamer/C-rich DNA successfully integrates the functions of VEGF/pH stimuli-responsive drug release and chemotherapeutic/phototherapeutic modalities into one single system, and may have great potential in cancer treatment.

Pitfalls and opportunities in quantitative fluorescence-based nanomedicine studies - A commentary

Fluorescence-based techniques are prevalent in studies of nanomedicine-targeting to cells and tissues. However, fluorescence-based studies are rarely quantitative, thus prohibiting direct comparisons of nanomedicine-performance across studies. With this Commentary, we aim to provoke critical thinking about experimental design by treating some often-overlooked pitfalls in 'quantitative' fluorescence-based experimentation. Focusing on fluorescence-labeled nanoparticles, we cover mechanisms like solvent-interactions and fluorophore-dissociation, which disqualify the assumption that 'a higher fluorescence readout' translates directly to 'a better targeting efficacy'. With departure in recent literature, we propose guidelines for circumventing these pitfalls in studies of tissue-accumulation and cell-uptake, thus covering fluorescence-based techniques like bulk solution fluorescence measurements, fluorescence microscopy, flow cytometry, and infrared fluorescence imaging. With this, we hope to lay a foundation for more 'quantitative thinking' during experimental design, enabling (for example) the estimation and reporting of actual numbers of fluorescent nanoparticles accumulated in cells and organs.

Key principles and methods for studying the endocytosis of biological and nanoparticle therapeutics

Endocytosis is a critical step in the process by which many therapeutic nanomedicines reach their intracellular targets. Our understanding of cellular uptake mechanisms has developed substantially in the past five years. However, these advances in cell biology have not fully translated to the nanoscience and therapeutics literature. Misconceptions surrounding the role of different endocytic pathways and how to study these pathways are hindering progress in developing improved nanoparticle therapies. Here, we summarize the latest insights into cellular uptake mechanisms and pathways. We highlight limitations of current systems to study endocytosis, particularly problems with non-specific inhibitors. We also summarize alternative genetic approaches to robustly probe these pathways and discuss the need to understand how cells endocytose particles in vivo. We hope that this critical assessment of the current methods used in studying nanoparticle uptake will guide future studies at the interface of cell biology and nanomedicine.