Inorganic Nanoparticles Change Cancer-Cell-Derived Extracellular Vesicle Secretion Levels and Cargo Composition, Resulting in Secondary Biological Effects

Over the past decades, the medical exploitation of nanotechnology has been largely increasing and finding its way into translational research and clinical applications. Despite their biomedical potential, uncertainties persist regarding the intricate role that nanomaterials may play on altering physiology in healthy and diseased tissues. Extracellular vesicles (EVs) are recognized as an important pathway for intercellular communication and known to be mediators of cellular stress. EVs are currently explored for targeted delivery of therapeutic agents, including nanoformulations, to treat and diagnose cancer or other diseases. Here, we aimed to investigate whether nanomaterials could have a possible impact on EV functionality, their safety, and whether EVs can play a role in nanomaterial toxicity profiles. To evaluate this, the impact of inorganic nanomaterial administration on EVs derived from murine melanoma and human breast cancer cells was tested. Cells were incubated with subtoxic concentrations of 4 different biomedically relevant inorganic nanoparticles (NPs): gold, silver, silicon dioxide, or iron oxide. The results displayed a clear NP and cell-type-dependent effect on increasing or decreasing EV secretion. Furthermore, the expression pattern of several EV-derived miRNAs was significantly changed upon NP exposure, compared to nontreated cells. Detailed pathway analysis and additional studies confirmed that EVs obtained from NP-exposed cells could influence immunological responses and cellular physiology. Together, these data reveal that NPs can have wide-ranging effects which can result in toxicity concerns or enhanced therapeutic potential as a secondary enhanced effect mediated and enhanced by EVs.

Human Autosomal Recessive DNA Polymerase Delta 3 Deficiency Presenting as Omenn Syndrome

The DNA polymerase δ complex (PolD), comprising catalytic subunit POLD1 and accessory subunits POLD2, POLD3, and POLD4, is essential for DNA synthesis and is central to genome integrity. We identified, by whole exome sequencing, a homozygous missense mutation (c.1118A > C; p.K373T) in POLD3 in a patient with Omenn syndrome. The patient exhibited severely decreased numbers of naïve T cells associated with a restricted T-cell receptor repertoire and a defect in the early stages of TCR recombination. The patient received hematopoietic stem cell transplantation at age 6 months. He manifested progressive neurological regression and ultimately died at age 4 years. We performed molecular and functional analysis of the mutant POLD3 and assessed cell cycle progression as well as replication-associated DNA damage. Patient fibroblasts showed a marked defect in S-phase entry and an enhanced number of double-stranded DNA break-associated foci despite normal expression levels of PolD components. The cell cycle defect was rescued by transduction with WT POLD3. This study validates autosomal recessive POLD3 deficiency as a novel cause of profound T-cell deficiency and Omenn syndrome.

The Efficacy of Nanoparticle Delivery to Hypoxic Solid Tumors by ciRGD Co-Administration Depends on Neuropilin-1 and Neutrophil Levels

The ability to improve nanoparticle delivery to solid tumors is an actively studied domain, where various mechanisms are looked into. In previous work, the authors have looked into nanoparticle size, tumor vessel normalization, and disintegration, and here it is aimed to continue this work by performing an in-depth mechanistic study on the use of ciRGD peptide co-administration. Using a multiparametric approach, it is observed that ciRGD can improve nanoparticle delivery to the tumor itself, but also to tumor cells specifically better than vessel normalization strategies. The effect depends on the level of tumor perfusion, hypoxia, neutrophil levels, and vessel permeability. This work shows that upon characterizing tumors for these parameters, conditions can be selected that can optimally benefit from ciRGD co-administration as a means to improve NP delivery to solid tumors.

Modulation of engineered nanomaterial interactions with organ barriers for enhanced drug transport

The biomedical use of nanoparticles (NPs) has been the focus of intense research for over a decade. As most NPs are explored as carriers to alter the biodistribution, pharmacokinetics and bioavailability of associated drugs, the delivery of these NPs to the tissues of interest remains an important topic. To date, the majority of NP delivery studies have used tumor models as their tool of interest, and the limitations concerning tumor targeting of systemically administered NPs have been well studied. In recent years, the focus has also shifted to other organs, each presenting their own unique delivery challenges to overcome. In this review, we discuss the recent advances in leveraging NPs to overcome four major biological barriers including the lung mucus, the gastrointestinal mucus, the placental barrier, and the blood-brain barrier. We define the specific properties of these biological barriers, discuss the challenges related to NP transport across them, and provide an overview of recent advances in the field. We discuss the strengths and shortcomings of different strategies to facilitate NP transport across the barriers and highlight some key findings that can stimulate further advances in this field.

Non disseminative nano-strategy against in vivo Staphylococcus aureus biofilms

Staphylococcus aureus is considered a high priority pathogen by the World Health Organization due to its high prevalence and the potential to form biofilms. Currently, the available treatments for S. aureus biofilm-associated infections do not target the extracellular polymeric substances (EPS) matrix. This matrix is a physical barrier to bactericidal agents, contributing to the increase of antimicrobial tolerance. The present work proposes the development of lipid nanoparticles encapsulating caspofungin (CAS) as a matrix-disruptive nanosystem. The nanoparticles were functionalized with D-amino acids to target the matrix. In a multi-target nano-strategy against S. aureus biofilms, CAS-loaded nanoparticles were combined with a moxifloxacin-loaded nanosystem, as an adjuvant to promote the EPS matrix disruption. In vitro and in vivo studies showed biofilm reduction after combining the two nanosystems. Besides, the combinatory therapy showed no signs of bacterial dissemination into vital organs of mice, while dissemination was observed for the treatment with the free compounds. Additionally, the in vivo biodistribution of the two nanosystems revealed their potential to reach and accumulate in the biofilm region, after intraperitoneal administration. Thus, this nano-strategy based on the encapsulation of matrix-disruptive and antibacterial agents is a promising approach to fight S. aureus biofilms.

Cu-doped TiO2 nanoparticles improve local antitumor immune activation and optimize dendritic cell vaccine strategies

Nanoparticle-mediated cancer immunotherapy holds great promise, but more efforts are needed to obtain nanoformulations that result in a full scale activation of innate and adaptive immune components that specifically target the tumors. We generated a series of copper-doped TiO₂ nanoparticles in order to tune the kinetics and full extent of Cu²⁺ ion release from the remnant TiO₂ nanocrystals. Fine-tuning nanoparticle properties resulted in a formulation of 33% Cu-doped TiO₂ which enabled short-lived hyperactivation of dendritic cells and hereby promoted immunotherapy. The nanoparticles result in highly efficient activation of dendritic cells ex vivo, which upon transplantation in tumor bearing mice, exceeded the therapeutic outcomes obtained with classically stimulated dendritic cells. Efficacious but simple nanomaterials that can promote dendritic cancer cell vaccination strategies open up new avenues for improved immunotherapy and human health.

Gold nanoparticle delivery to solid tumors: a multiparametric study on particle size and the tumor microenvironment

Nanoparticle (NP) delivery to solid tumors remains an actively studied field, where several recent studies have shed new insights into the underlying mechanisms and the still overall poor efficacy. In the present study, Au NPs of different sizes were used as model systems to address this topic, where delivery of the systemically administered NPs to the tumor as a whole or to tumor cells specifically was examined in view of a broad range of tumor-associated parameters. Using non-invasive imaging combined with histology, immunohistochemistry, single-cell spatial RNA expression and image-based single cell cytometry revealed a size-dependent complex interaction of multiple parameters that promoted tumor and tumor-cell specific NP delivery. Interestingly, the data show that most NPs are sequestered by tumor-associated macrophages and cancer-associated fibroblasts, while only few NPs reach the actual tumor cells. While perfusion is important, leaky blood vessels were found not to promote NP delivery, but rather that delivery efficacy correlated with the maturity level of tumor-associated blood vessels. In line with recent studies, we found that the presence of specialized endothelial cells, expressing high levels of CD276 and Plvap promoted both tumor delivery and tumor cell-specific delivery of NPs. This study identifies several parameters that can be used to determine the suitability of NP delivery to the tumor region or to tumor cells specifically, and enables personalized approaches for maximal delivery of nanoformulations to the targeted tumor.

The Role of Optical Imaging in Translational Nanomedicine

Nanomedicines have been a major research focus in the past two decades and are increasingly emerging in a broad range of clinical applications. However, a proper understanding of their biodistribution is required to further progress the field of nanomedicine. For this, imaging methods to monitor the delivery and therapeutic efficacy of nanoparticles are urgently needed. At present, optical imaging is the most common method used to study the biodistribution of nanomaterials, where the unique properties of nanomaterials and advances in optical imaging can jointly result in novel methods for optimal monitoring of nanomaterials in preclinical animal models. This review article aims to give an introduction to nanomedicines and their translational impact to highlight the potential of optical imaging to study the biodistribution of nanoparticles and to monitor the delivery and therapeutic efficacy at the preclinical level. After introducing both domains, the review focuses on different techniques that can be used to overcome some intrinsic limitations of optical imaging and how this can specifically benefit nanoparticle studies. Finally, we point out some important key features of nanoparticles that currently hinder their full potential in the clinic and how the advances in optical imaging can help to provide us with the information needed to further boost the clinical translation and expand the field of nanomedicines.

Multicompartmental Microcapsules for Enzymatic Cascade Reactions Prepared through Gas Shearing and Surface Gelation

Inspired by the structure of eukaryotic cells, multicompartmental microcapsules have gained increasing attention. However, challenges remain in the fabrication of "all-aqueous" (i.e., oil-free) microcapsules composed of accurately adjustable hierarchical compartments. This study reports on multicompartmental microcapsules with an innovative architecture. While multicompartmental cores of the microcapsules were fabricated through gas shearing, a shell was applied on the cores through surface gelation of alginate. Different from traditional multicompartmental microcapsules, thus obtained microcapsules have well-segregated compartments while the universal nature of the surface-gelation method allows us to finely tune the shell thicknesses of the microcapsules. The microcapsules are highly stable and cytocompatible and allow repeated enzymatic cascade reactions, which might make them of interest for complex biocatalysis or for mimicking physiological processes.

Modularity of RBC hitchhiking with polymeric nanoparticles: testing the limits of non-covalent adsorption

Red blood cell (RBC) hitchhiking has great potential in enhancing drug therapy, by improving targeting and reducing rapid clearance of nanoparticles (NPs). However, to improve the potential for clinical translation of RBC hitchhiking, a more thorough understanding of the RBC-NP interface is needed. Here, we evaluate the effects of NP surface parameters on the success and biocompatibility of NP adsorption to extracted RBCs from various species. Major differences in RBC characteristics between rabbit, mouse and human were proven to significantly impact NP adsorption outcomes. Additionally, the effects of NP design parameters, including NP hydrophobicity, zeta potential, surfactant concentration and drug encapsulation, on RBC hitchhiking are investigated. Our studies demonstrate the importance of electrostatic interactions in balancing NP adsorption success and biocompatibility. We further investigated the effect of varying the anti-coagulant used for blood storage. The results presented here offer new insights into the parameters that impact NP adsorption on RBCs that will assist researchers in experimental design choices for using RBC hitchhiking as drug delivery strategy.

Gold nanostructures: synthesis, properties, and neurological applications

Recent advances in technology are expected to increase our current understanding of neuroscience. Nanotechnology and nanomaterials can alter and control neural functionality in both in vitro and in vivo experimental setups. The intersection between neuroscience and nanoscience may generate long-term neural interfaces adapted at the molecular level. Owing to their intrinsic physicochemical characteristics, gold nanostructures (GNSs) have received much attention in neuroscience, especially for combined diagnostic and therapeutic (theragnostic) purposes. GNSs have been successfully employed to stimulate and monitor neurophysiological signals. Hence, GNSs could provide a promising solution for the regeneration and recovery of neural tissue, novel neuroprotective strategies, and integrated implantable materials. This review covers the broad range of neurological applications of GNS-based materials to improve clinical diagnosis and therapy. Sub-topics include neurotoxicity, targeted delivery of therapeutics to the central nervous system (CNS), neurochemical sensing, neuromodulation, neuroimaging, neurotherapy, tissue engineering, and neural regeneration. It focuses on core concepts of GNSs in neurology, to circumvent the limitations and significant obstacles of innovative approaches in neurobiology and neurochemistry, including theragnostics. We will discuss recent advances in the use of GNSs to overcome current bottlenecks and tackle technical and conceptual challenges.

Core-shell microparticles: From rational engineering to diverse applications

Core-shell microparticles, composed of solid, liquid, or gas bubbles surrounded by a protective shell, are gaining considerable attention as intelligent and versatile carriers that show great potential in biomedical fields. In this review, an overview is given of recent developments in design and applications of biodegradable core-shell systems. Several emerging methodologies including self-assembly, gas-shearing, and coaxial electrospray are discussed and microfluidics technology is emphasized in detail. Furthermore, the characteristics of core-shell microparticles in artificial cells, drug release and cell culture applications are discussed and the superiority of these advanced multi-core microparticles for the generation of artificial cells is highlighted. Finally, the respective developing orientations and limitations inherent to these systems are addressed. It is hoped that this review can inspire researchers to propel the development of this field with new ideas.

The Use of Alternative Strategies for Enhanced Nanoparticle Delivery to Solid Tumors

Nanomaterial (NM) delivery to solid tumors has been the focus of intense research for over a decade. Classically, scientists have tried to improve NM delivery by employing passive or active targeting strategies, making use of the so-called enhanced permeability and retention (EPR) effect. This phenomenon is made possible due to the leaky tumor vasculature through which NMs can leave the bloodstream, traverse through the gaps in the endothelial lining of the vessels, and enter the tumor. Recent studies have shown that despite many efforts to employ the EPR effect, this process remains very poor. Furthermore, the role of the EPR effect has been called into question, where it has been suggested that NMs enter the tumor via active mechanisms and not through the endothelial gaps. In this review, we provide a short overview of the EPR and mechanisms to enhance it, after which we focus on alternative delivery strategies that do not solely rely on EPR in itself but can offer interesting pharmacological, physical, and biological solutions for enhanced delivery. We discuss the strengths and shortcomings of these different strategies and suggest combinatorial approaches as the ideal path forward.

Whither Magnetic Hyperthermia? A Tentative Roadmap

The scientific community has made great efforts in advancing magnetic hyperthermia for the last two decades after going through a sizeable research lapse from its establishment. All the progress made in various topics ranging from nanoparticle synthesis to biocompatibilization and in vivo testing have been seeking to push the forefront towards some new clinical trials. As many, they did not go at the expected pace. Today, fruitful international cooperation and the wisdom gain after a careful analysis of the lessons learned from seminal clinical trials allow us to have a future with better guarantees for a more definitive takeoff of this genuine nanotherapy against cancer. Deliberately giving prominence to a number of critical aspects, this opinion review offers a blend of state-of-the-art hints and glimpses into the future of the therapy, considering the expected evolution of science and technology behind magnetic hyperthermia.

Role of inorganic nanoparticle degradation in cancer therapy

Nanomaterials are currently widely exploited for their potential in the development of novel cancer therapies, and so far, mainly nanoparticles (NPs) consisting of liposomes and polymers have made their way into the clinic. However, major bottlenecks for the clinical translation of other types of NPs (i.e. inorganic) are the lack of knowledge concerning their long-term distribution in vivo and their potential toxicity. To counter this, various research groups have worked on soluble NPs, such as zinc oxide (ZnO), copper oxide (CuO), and silver (Ag), which tend to dissolve spontaneously into their ionic form, releasing toxic metal ions and leading to reactive oxygen species (ROS) generation when exposed to cellular environments. By fine-tuning the dissolution kinetics of these NPs, it is possible to control the level of ROS production and thus cytotoxicity to selectively destroy tumor tissue. Specifically, cancer cells tend to exhibit a higher basal level of oxidative stress compared to normal cells due to their higher metabolic rates, and therefore, by engineering NPs that generate sufficient ROS that barely exceed toxic thresholds in cancer cells, normal cells will only experience reversible transient damage. This review focuses on the use of these soluble inorganic NPs for selective cancer therapy and on the various in vitro and in vivo studies that have aimed to control the dissolution kinetics of these NPs, either through particle doping or surface modifications.

A Multiparametric Evaluation of Quantum Dot Size and Surface-Grafted Peptide Density on Cellular Uptake and Cytotoxicity

Despite the progress in nanotechnology for biomedical applications, great efforts are still being employed in optimizing nanoparticle (NP) design parameters to improve functionality and minimize bionanotoxicity. In this study, we developed CdSe/CdS/ZnS core/shell/shell quantum dots (QDs) that are compact ligand-coated and surface-functionalized with an HIV-1-derived TAT cell-penetrating peptide (CPP) analog to improve both biocompatibility and cellular uptake. Multiparametric studies were performed in different mammalian and murine cell lines to compare the effects of varying QD size and number of surface CPPs on cellular uptake, viability, generation of reactive oxygen species, mitochondrial health, cell area, and autophagy. Our results showed that the number of cell-associated NPs and their respective toxicity are higher for the larger QDs. Meanwhile, increasing the number of surface CPPs also enhanced cellular uptake and induced cytotoxicity through the generation of mitoROS and autophagy. Thus, here we report the optimal size and surface CPP combinations for improved QD cellular uptake.

Model-Based Nanoengineered Pharmacokinetics of Iron-Doped Copper Oxide for Nanomedical Applications

The progress in nanomedicine (NM) using nanoparticles (NPs) is mainly based on drug carriers for the delivery of classical chemotherapeutics. As low NM delivery rates limit therapeutic efficacy, an entirely different approach was investigated. A homologous series of engineered CuO NPs was designed for dual purposes (carrier and drug) with a direct chemical composition-biological functionality relationship. Model-based dissolution kinetics of CuO NPs in the cellular interior at post-exposure conditions were controlled through Fe-doping for intra/extra cellular Cu2+ and biological outcome. Through controlled ion release and reactions taking place in the cellular interior, tumors could be treated selectively, in vitro and in vivo. Locally administered NPs enabled tumor cells apoptosis and stimulated systemic anti-cancer immune responses. We clearly show therapeutic effects without tumor cells relapse post-treatment with 6 % Fe-doped CuO NPs combined with myeloid-derived suppressor cell silencing.

Longitudinal In Vivo Assessment of Host-Microbe Interactions in a Murine Model of Pulmonary Aspergillosis

The fungus Aspergillus fumigatus is ubiquitous in nature and the most common cause of invasive pulmonary aspergillosis (IPA) in patients with a compromised immune system. The development of IPA in patients under immunosuppressive treatment or in patients with primary immunodeficiency demonstrates the importance of the host immune response in controlling aspergillosis. However, study of the host-microbe interaction has been hampered by the lack of tools for their non-invasive assessment. We developed a methodology to study the response of the host's immune system against IPA longitudinally in vivo by using fluorine-19 magnetic resonance imaging (¹⁹F MRI). We showed the advantage of a perfluorocarbon-based contrast agent for the in vivo labeling of macrophages and dendritic cells, permitting quantification of pulmonary inflammation in different murine IPA models. Our findings reveal the potential of ¹⁹F MRI for the assessment of rapid kinetics of innate immune response against IPA and the permissive niche generated through immunosuppression.

Targeting tumor cells and neovascularization using RGD-functionalized magnetoliposomes

Purpose

Magnetoliposomes (MLs) have shown great potential as magnetic resonance imaging contrast agents and as delivery vehicles for cancer therapy. Targeting the MLs towards the tumor cells or neovascularization could ensure delivery of drugs at the tumor site. In this study, we evaluated the potential of MLs targeting the αvβ3 integrin overexpressed on tumor neovascularization and different tumor cell types, including glioma and ovarian cancer.

Methods

MLs functionalized with a Texas Red fluorophore (anionic MLs), and with the fluorophore and the cyclic Arginine-Glycine-Aspartate (cRGD; cRGD-MLs) targeting the αvβ3 integrin, were produced in-house. Swiss nude mice were subcutaneously injected with 10⁷ human ovarian cancer SKOV-3 cells. Tumors were allowed to grow for 3 weeks before injection of anionic or cRGD-MLs. Biodistribution of MLs was followed up with a 7T preclinical magnetic resonance imaging (MRI) scanner and fluorescence imaging (FLI) right after injection, 2h, 4h, 24h and 48h post injection. Ex vivo intratumoral ML uptake was confirmed using FLI, electron paramagnetic resonance spectroscopy (EPR) and histology at different time points post injection.

Results

In vivo, we visualized a higher uptake of cRGD-MLs in SKOV-3 xenografts compared to control, anionic MLs with both MRI and FLI. Highest ML uptake was seen after 4h using MRI, but only after 24h using FLI indicating the lower sensitivity of this technique. Furthermore, ex vivo EPR and FLI confirmed the highest tumoral ML uptake at 4 h. Last, a Perl’s stain supported the presence of our iron-based particles in SKOV-3 xenografts.

Conclusion

Uptake of cRGD-MLs can be visualized using both MRI and FLI, even though the latter was less sensitive due to lower depth penetration. Furthermore, our results indicate that cRGD-MLs can be used to target SKOV-3 xenograft in Swiss nude mice. Therefore, the further development of this particles into theranostics would be of interest.

Tri-modal In vivo Imaging of Pancreatic Islets Transplanted Subcutaneously in Mice

PURPOSE

Transplantation of pancreatic islets (PIs) is a promising therapeutic approach for type 1 diabetes. The main obstacle for this strategy is that the outcome of islet engraftment depends on the engraftment site. It was our aim to develop a strategy for using non-invasive imaging techniques to assess the location and fate of transplanted PIs longitudinally in vivo.

PROCEDURES

In order to overcome the limitations of individual imaging techniques and cross-validate findings by different modalities, we have combined fluorine magnetic resonance imaging (F-19 MRI), fluorescence imaging (FLI), and bioluminescent imaging (BLI) for studying subcutaneously transplanted PIs and beta cell-like cells (INS-1E cell line) in vivo. We optimized the transduction (using lentiviral vectors) and labeling procedures (using perfluoro crown ether nanoparticles with a fluorescence dye) for PIs and INS-1E cell imaging.

RESULTS

The feasibility of using the proposed imaging methods for PI assessment was demonstrated both in vitro and in vivo. Our data suggested that F-19 MRI is suitable for high-resolution localization of transplanted cells and PIs; FLI is essential for confirmation of contrast localization by histology; and BLI is a reliable method to assess cell viability and survival after transplantation. No significant side effects on cell viability and function have been observed.

CONCLUSIONS

The proposed tri-modal imaging platform is a valuable approach for the assessment of engrafted PIs in vivo. It is potentially suitable for comparing different transplantation sites and evaluating novel strategies for improving PI transplantation technique in the future.

Fe-Doped ZnO nanoparticle toxicity: assessment by a new generation of nanodescriptors

In the search for novel tools to combat cancer, nanoparticles (NPs) have attracted a lot of attention. Recently, the controlled release of cancer-cell-killing metal ions from doped NPs has shown promise, but fine tuning of dissolution kinetics is required to ensure specificity and minimize undesirable toxic side-effects. Theoretical tools to help in reaching a proper understanding and finally be able to control the dissolution kinetics by NP design have not been available until now. Here, we present a novel set of true nanodescriptors to analyze the charge distribution, the effect of doping and surface coating of whole metal oxide NP structures. The polarizable model of oxygen atoms enables light to be shed on the charge distribution on the NP surface, allowing the in detail study of the factors influencing the release of metal ions from NPs. The descriptors and their capabilities are demonstrated on a Fe-doped ZnO nanoparticle system, a system with practical outlook and available experimental data.

The impact of nanoparticle-driven lysosomal alkalinization on cellular functionality

BACKGROUND

The biomedical use of nanosized materials is rapidly gaining interest, which drives the quest to elucidate the behavior of nanoparticles (NPs) in a biological environment. Apart from causing direct cell death, NPs can affect cellular wellbeing through a wide range of more subtle processes that are often overlooked. Here, we aimed to study the effect of two biomedically interesting NP types on cellular wellbeing.

RESULTS

In the present work, gold and SiO₂ NPs of similar size and surface charge are used and their interactions with cultured cells is studied. Initial screening shows that at subcytotoxic conditions gold NPs induces cytoskeletal aberrations while SiO₂ NPs do not. However, these transformations are only transient. In-depth investigation reveals that Au NPs reduce lysosomal activity by alkalinization of the lysosomal lumen. This leads to an accumulation of autophagosomes, resulting in a reduced cellular degradative capacity and less efficient clearance of damaged mitochondria. The autophagosome accumulation induces Rac and Cdc42 activity, and at a later stage activates RhoA. These transient cellular changes also affect cell functionality, where Au NP-labelled cells display significantly impeded cell migration and invasion.

CONCLUSIONS

These data highlight the importance of in-depth understanding of bio-nano interactions to elucidate how one biological parameter (impact on cellular degradation) can induce a cascade of different effects that may have significant implications on the further use of labeled cells.

Magnetoliposomes as Contrast Agents for Longitudinal in vivo Assessment of Transplanted Pancreatic Islets in a Diabetic Rat Model

Magnetoliposomes (MLs) were synthesized and tested for longitudinal monitoring of transplanted pancreatic islets using magnetic resonance imaging (MRI) in rat models. The rat insulinoma cell line INS-1E and isolated pancreatic islets from outbred and inbred rats were used to optimize labeling conditions in vitro. Strong MRI contrast was generated by islets exposed to 50 µg Fe/ml for 24 hours without any increased cell death, loss of function or other signs of toxicity. In vivo experiments showed that pancreatic islets (50-1000 units) labeled with MLs were detectable for up to 6 weeks post-transplantation in the kidney subcapsular space. Islets were also monitored for two weeks following transplantation through the portal vein of the liver. Hereby, islets labeled with MLs and transplanted under the left kidney capsule were able to correct hyperglycemia and had stable MRI signals until nephrectomy. Interestingly, in vivo MRI of streptozotocin induced diabetic rats transplanted with allogeneic islets demonstrated loss of MRI contrast between 7-16 days, indicative of loss of islet structure. MLs used in this study were not only beneficial for monitoring the location of transplanted islets in vivo with high sensitivity but also reported on islet integrity and hereby indirectly on islet function and rejection.

A Magnetic Chameleon: Biocompatible Lanthanide Fluoride Nanoparticles with Magnetic Field Dependent Tunable Contrast Properties as a Versatile Contrast Agent for Low to Ultrahigh Field MRI and Optical Imaging in Biological Window

A novel type of multimodal, magnetic resonance imaging/optical imaging (MRI/OI) contrast agent was developed, based on core-shell lanthanide fluoride nanoparticles composed of a β-NaHoF4 core plus a β-NaGdF4:Yb³⁺ , Tm³⁺ shell with an average size of ∼24 nm. The biocompatibility of the particles was ensured by a surface modification with poly acrylic acid (PAA) and further functionalization with an affinity ligand, folic acid (FA). When excited using 980 nm near infrared (NIR) radiation, the contrast agent (CA) shows intense emission at 802 nm with lifetime of 791±3 μs, due to the transition ³ H₄ →³ H₆ of Tm³⁺ . Proton nuclear magnetic relaxation dispersion (¹ H-NMRD) studies and magnetic resonance (MR) phantom imaging showed that the newly synthesized nanoparticles, decorated with poly(acrylic acid) and folic acid on the surface (NP-PAA-FA), can act mainly as a T₁ -weighted contrast agent below 1.5 T, a T₁ /T₂ dual-weighted contrast agent at 3 T, and as highly efficient T₂ -weighted contrast agent at ultrahigh fields. In addition, NP-PAA-FA showed very low cytotoxicity and no detectable cellular damage up to a dose of 500 μg mL^-1 .

Nanoparticle-induced inflammation can increase tumor malignancy

Nanomaterials, such as aluminum oxide, have been regarded with high biomedical promise as potential immune adjuvants in favor of their bulk counterparts. For pathophysiological conditions where elevated immune activity already occurs, the contribution of nanoparticle-activated immune reactions remains unclear. Here, we investigated the effect of spherical and wire-shaped aluminum oxide nanoparticles on primary splenocytes and observed a clear pro-inflammatory effect of both nanoparticles, mainly for the high aspect ratio nanowires. The nanoparticles resulted in a clear activation of NLRP3 inflammasome, and also secreted transforming growth factor β. When cancer cells were exposed to these cytokines, this resulted in an increased level of epithelial-to-mesenchymal-transition, a hallmark for cancer metastasis, which did not occur when the cancer cells were directly exposed to the nanoparticles themselves. Using a syngeneic tumor model, the level of inflammation and degree of lung metastasis were significantly increased when the animals were exposed to the nanoparticles, particularly for the nanowires. This effect could be abrogated by treating the animals with inflammatory inhibitors. Collectively, these data indicate that the interaction of nanoparticles with immune cells can have secondary effects that may aggravate pathophysiological conditions, such as cancer malignancy, and conditions must be carefully selected to finely tune the induced aspecific inflammation into cancer-specific antitumor immunity.

STATEMENT OF SIGNIFICANCE

Many different types of nanoparticles have been shown to possess immunomodulatory properties, depending on their physicochemical parameters. This can potentially be harnessed as a possible antitumor therapy. However, in the current work we show that inflammation elicited by nanomaterials can have grave effects in pathophysiological conditions, where non-specific inflammation was found to increase cancer cell mobility and tumor malignancy. These data show that immunomodulatory properties of nanomaterials must be carefully controlled to avoid any undesired side-effects.

Green electrospun and crosslinked poly(vinyl alcohol)/poly(acrylic acid) composite membranes for antibacterial effective air filtration

Air pollution has become a major environmental concern given the ever increasing levels of particulate matter (PM) and the increased in treatment-resistant bacterial and viral strains. Major efforts are therefore required into the development of air filtration and purification technology as well as novel, alternative antiviral and antibacterial treatment modalities. Here, we report an environmentally friendly method for the generation of multifunctional poly(vinyl alcohol)/poly(acrylic acid) (PVA-PAA) composite membranes via green electrospinning and thermal crosslinking. Superhydrophobic silica nanoparticles were then incorporated into the fibers resulting in a rough surface, after which AgNO₃ was introduced, resulting in the formation of Ag nanoparticles through UV reduction. The PVA-PAA-SiO₂-Ag NPs membranes were found to possess high air filtration performance (with >98% filtration efficiency for PM_2.5) as well as potent antibacterial and antiviral activities. The green synthesis approach avoids the use of hazardous organic solvents, thereby bypassing any potential toxicity concerns caused by organic solvent residues. These newly designed PVA-PAA-SiO₂ NPs-Ag NPs nanofibrous membranes with many superior features (e.g. high filtration efficiency, high tensile strength, biological compatibility, and antibacterial properties) can be applied in eco-friendly air filtration materials, in particular for personal air filtration devices.

Assessing cell-nanoparticle interactions by high content imaging of biocompatible iron oxide nanoparticles as potential contrast agents for magnetic resonance imaging

Stem cell tracking in cellular therapy and regenerative medicine is an urgent need, superparamagnetic iron oxide nanoparticles (IONPs) could be used as contrast agents in magnetic resonance imaging (MRI) that allows visualization of the implanted cells ensuring they reach the desired sites in vivo. Herein, we report the study of the interaction of 3,4-dihydroxyhydrocinnamic acid (DHCA) functionalized IONPs that have desirable properties for T2 - weighted MRI, with bone marrow-derived primary human mesenchymal stem cells (hMSCs). Using the multiparametric high-content imaging method, we evaluate cell viability, formation of reactive oxygen species, mitochondrial health, as well as cell morphology and determine that the hMSCs are minimally affected after labelling with IONPs. Their cellular uptake is visualized by transmission electron microscopy (TEM) and Prussian Blue staining, and quantified using an iron specific colourimetric method. In vitro and in vivo studies demonstrate that these IONPs are biocompatible and can produce significant contrast enhancement in T2-weighted MRI. Iron oxide nanoparticles are detected in vivo as hypointense regions in the liver up to two weeks post injection using 9.4 T MRI. These DHCA functionalized IONPs are promising contrast agents for stem cell tracking by T2-weighted MRI as they are biocompatible and show no evidence of cytotoxic effects on hMSCs.

The role of intracellular trafficking of CdSe/ZnS QDs on their consequent toxicity profile

Background

Nanoparticle interactions with cellular membranes and the kinetics of their transport and localization are important determinants of their functionality and their biological consequences. Understanding these phenomena is fundamental for the translation of such NPs from in vitro to in vivo systems for bioimaging and medical applications. Two CdSe/ZnS quantum dots (QD) with differing surface functionality (NH₂ or COOH moieties) were used here for investigating the intracellular uptake and transport kinetics of these QDs.

Results

In water, the COOH- and NH₂-QDs were negatively and positively charged, respectively, while in serum-containing medium the NH₂-QDs were agglomerated, whereas the COOH-QDs remained dispersed. Though intracellular levels of NH₂- and COOH-QDs were very similar after 24 h exposure, COOH-QDs appeared to be continuously internalised and transported by endosomes and lysosomes, while NH₂-QDs mainly remained in the lysosomes. The results of (intra)cellular QD trafficking were correlated to their toxicity profiles investigating levels of reactive oxygen species (ROS), mitochondrial ROS, autophagy, changes to cellular morphology and alterations in genes involved in cellular stress, toxicity and cytoskeletal integrity. The continuous flux of COOH-QDs perhaps explains their higher toxicity compared to the NH₂-QDs, mainly resulting in mitochondrial ROS and cytoskeletal remodelling which are phenomena that occur early during cellular exposure.

Conclusions

Together, these data reveal that although cellular QD levels were similar after 24 h, differences in the nature and extent of their cellular trafficking resulted in differences in consequent gene alterations and toxicological effects.

Electronic supplementary material

The online version of this article (doi:10.1186/s12951-017-0279-0) contains supplementary material, which is available to authorized users.

Choose your cell model wisely: The in vitro nanoneurotoxicity of differentially coated iron oxide nanoparticles for neural cell labeling

Currently, there is a large interest in the labeling of neural stem cells (NSCs) with iron oxide nanoparticles (IONPs) to allow MRI-guided detection after transplantation in regenerative medicine. For such biomedical applications, excluding nanotoxicity is key. Nanosafety is primarily evaluated in vitro where an immortalized or cancer cell line of murine origin is often applied, which is not necessarily an ideal cell model. Previous work revealed clear neurotoxic effects of PMA-coated IONPs in distinct cell types that could potentially be applied for nanosafety studies regarding neural cell labeling. Here, we aimed to assess if DMSA-coated IONPs could be regarded as a safer alternative for this purpose and how the cell model impacted our nanosafety optimization study. Hereto, we evaluated cytotoxicity, ROS production, calcium levels, mitochondrial homeostasis and cell morphology in six related neural cell types, namely neural stem cells, an immortalized cell line and a cancer cell line from human and murine origin. The cell lines mostly showed similar responses to both IONPs, which were frequently more pronounced for the PMA-IONPs. Of note, ROS and calcium levels showed opposite trends in the human and murine NSCs, indicating the importance of the species. Indeed, the human cell models were overall more sensitive than their murine counterpart. Despite the clear cell type-specific nanotoxicity profiles, our multiparametric approach revealed that the DMSA-IONPs outperformed the PMA-IONPs in terms of biocompatibility in each cell type. However, major cell type-dependent variations in the observed effects additionally warrant the use of relevant human cell models.

STATEMENT OF SIGNIFICANCE

Inorganic nanoparticle (NP) optimization is chiefly performed in vitro. For the optimization of iron oxide (IO)NPs for neural stem cell labeling in the context of regenerative medicine human or rodent neural stem cells, immortalized or cancer cell lines are applied. However, the use of certain cell models can be questioned as they phenotypically differ from the target cell. The impact of the neural cell model on nanosafety remains relatively unexplored. Here we evaluated cell homeostasis upon exposure to PMA- and DMSA-coated IONPs. Of note, the DMSA-IONPs outperformed the PMA-IONPs in each cell type. However, distinct cell type-specific effects were witnessed, indicating that nanosafety should be evaluated in a human cell model that represents the target cell as closely as possible.

In Silico Design of Optimal Dissolution Kinetics of Fe-Doped ZnO Nanoparticles Results in Cancer-Specific Toxicity in a Preclinical Rodent Model

Cancer cells have unique but widely varying characteristics that have proven them difficult to be treated by classical therapeutics and calls for novel and selective treatment options. Nanomaterials (NMs) have been shown to display biological effects as a function of their chemical composition, and the extent and exact nature of these effects can vary between different biological environments. Here, ZnO NMs are doped with increasing levels of Fe, which allows to finely tune their dissolution rate resulting in significant differences in their biological behavior on cancer or normal cells. Based on in silico analysis, 2% Fe-doped ZnO NMs are found to be optimal to cause selective cancer cell death, which is confirmed in both cultured cells and syngeneic tumor models, where they also reduce metastasis formation. These results show that upon tuning NM chemical composition, NMs can be designed as a targeted selective anticancer therapy.

Coating of Quantum Dots strongly defines their effect on lysosomal health and autophagy

In the last decade the interest in autophagy got an incredible boost and the phenomenon quickly turned into an extensive research field. Interestingly, dysfunction of this cytoplasmic clearance system has been proposed to lie at the root of multiple diseases including cancer. We therefore consider it crucial from a toxicological point of view to investigate if nanomaterials that are developed for biomedical applications interfere with this cellular process. Here, we study the highly promising 'gradient alloyed' Quantum Dots (QDs) that differ from conventional ones by their gradient core composition which allows for better fluorescent properties. We carefully examined the toxicity of two identical gradient alloyed QDs, differing only in their surface coatings, namely 3-mercaptopropionic (MPA) acid and polyethylene glycol (PEG). Next to more conventional toxicological endpoints like cytotoxicity and oxidative stress, we examined the influence of these QDs on the autophagy pathway. Our study shows that the cellular effects induced by QDs on HeLa cells were strongly dictated by the surface coat of the otherwise identical particles. MPA-coated QDs proved to be highly biocompatible as a result of lysosomal activation and ROS reduction, two cellular responses that help the cell to cope with nanomaterial-induced stress. In contrast, PEGylated QDs were significantly more toxic due to increased ROS production and lysosomal impairment. This impairment next results in autophagy dysfunction which likely adds to their toxic effects. Taken together, our study shows that coating QDs with MPA is a better strategy than PEGylation for long term cell tracking with minimal cytotoxicity.

STATEMENT OF SIGNIFICANCE

Gradient alloyed Quantum Dots (GA-QDs) are highly promising nanomaterials for biomedical imaging seeing they exhibit supremely fluorescent properties over conventional QDs. The translation of these novel QDs to the clinic requires a detailed toxicological examination, though the data on this is very limited. We therefore applied a systematic approach to examine the toxicity of GA-QDs coated with two commonly applied surface ligands, this while focusing on the autophagy pathway. The impact of QDs on this pathway is of importance since it has been connected with various diseases, including cancer. Our data accentuates that the coating defines the impact on autophagy and therefore the toxicity induced by QDs on cells: while MPA coated QDs were highly biocompatible, PEGylated QDs were toxic.

Presence of an Immune System Increases Anti-Tumor Effect of Ag Nanoparticle Treated Mice

To date, most nanomedical studies rely on the use of immune-deficient mice in which the contribution of the immune system on the applied therapy is ignored. Here, the degradation of silver nanoparticles (Ag NPs) is exploited as a means to treat subcutaneous tumor models in mice. To investigate the impact of the immune system, the same tumor cell type (KLN 205 murine squamous cell carcinoma) is used in a xenograft model in NOD SCIDγ immune-deficient mice and as a syngeneic model in immune-competent DBA/2 mice. The Ag NPs are screened for their cytotoxicity on various cancer cell lines, indicating a concentration-dependent induction of oxidative stress, mitochondrial damage, and autophagy on all cell types tested. At subcytotoxic concentrations, prolonged cellular exposure to the Ag NPs results in toxicity due to NP degradation and the generation of toxic Ag⁺ ions. At subcytotoxic conditions, the NPs are found to cause inflammation in vitro. Similar results are obtained in the immune-competent mouse model, where clear inflammation is observed after treatment of the implanted tumors with Ag NPs. This inflammation leads to an ongoing antitumoral effect, which results in a significantly reduced tumor growth compared to Ag NP-treated tumors in an immune-deficient model.

Standard Cellular Testing Conditions Generate an Exaggerated Nanoparticle Cytotoxicity Profile

Cellular internalization of nanoparticles (NPs) is key to many biomedical applications and serves as a model to investigate the potential toxicity of NPs on entire organisms. Large discrepancies between in vitro and in vivo nanotoxicity data however exist, suggesting that cellular systems may not be optimal for predictive in vivo toxicology. Here, we use validated multiparametric high-content imaging protocols to evaluate the impact of common cell culture conditions on NP cytotoxicity studies. The data show that high NP to cell ratios, typical for cellular studies, stress the cells by high endocytosis levels that overstimulate mitochondria, resulting in oxidative stress-mediated mitochondrial damage, which induces autophagy. Using proliferation-restricted models, we show that lowering endocytosis levels overcomes most toxicity while resulting in higher final cellular NP numbers. The data suggest that many common NP cytotoxicity mechanisms may partially be an artifact caused by overstimulated endocytosis.

The impact of species and cell type on the nanosafety profile of iron oxide nanoparticles in neural cells

BACKGROUND

While nanotechnology is advancing rapidly, nanosafety tends to lag behind since general mechanistic insights into cell-nanoparticle (NP) interactions remain rare. To tackle this issue, standardization of nanosafety assessment is imperative. In this regard, we believe that the cell type selection should not be overlooked since the applicability of cell lines could be questioned given their altered phenotype. Hence, we evaluated the impact of the cell type on in vitro nanosafety evaluations in a human and murine neuroblastoma cell line, neural progenitor cell line and in neural stem cells. Acute toxicity was evaluated for gold, silver and iron oxide (IO)NPs, and the latter were additionally subjected to a multiparametric analysis to assess sublethal effects.

RESULTS

The stem cells and murine neuroblastoma cell line respectively showed most and least acute cytotoxicity. Using high content imaging, we observed cell type- and species-specific responses to the IONPs on the level of reactive oxygen species production, calcium homeostasis, mitochondrial integrity and cell morphology, indicating that cellular homeostasis is impaired in distinct ways.

CONCLUSIONS

Our data reveal cell type-specific toxicity profiles and demonstrate that a single cell line or toxicity end point will not provide sufficient information on in vitro nanosafety. We propose to identify a set of standard cell lines for screening purposes and to select cell types for detailed nanosafety studies based on the intended application and/or expected exposure.

High-Content Imaging and Gene Expression Approaches To Unravel the Effect of Surface Functionality on Cellular Interactions of Silver Nanoparticles

The toxic effects of Ag nanoparticles (NPs) remain an issue of debate, where the respective contribution of the NPs themselves and of free Ag(+) ions present in the NP stock suspensions and after intracellular NP corrosion are not fully understood. Here, we employ a recently set up methodology based on high-content (HC) imaging combined with high-content gene expression studies to examine the interaction of three types of Ag NPs with identical core sizes, but coated with either mercaptoundecanoic acid (MUA), dodecylamine-modified poly(isobutylene-alt-maleic anhydride) (PMA), or poly(ethylene glycol) (PEG)-conjugated PMA with two types of cultured cells (primary human umbilical vein endothelial cells (HUVEC) and murine C17.2 neural progenitor cells). As a control, cells were also exposed to free Ag(+) ions at the same concentration as present in the respective Ag NP stock suspensions. The data reveal clear effects of the NP surface properties on cellular interactions. PEGylation of the NPs significantly reduces their cellular uptake efficiency, whereas MUA-NPs are more prone to agglomeration in complex tissue culture media. PEG-NPs display the lowest levels of toxicity, which is in line with their reduced cell uptake. MUA-NPs display the highest levels of toxicity, caused by autophagy, cell membrane damage, mitochondrial damage, and cytoskeletal deformations. At similar intracellular NP levels, PEG-NPs induce the highest levels of reactive oxygen species (ROS), but do not affect the cell cytoskeleton, in contrast to MUA- and PMA-NPs. Gene expression studies support the findings above, defining autophagy and cell membrane damage-related necrosis as main toxicity pathways. Additionally, immunotoxicity, DNA damage responses, and hypoxia-like toxicity were observed for PMA- and especially MUA-NPs. Together, these data reveal that Ag(+) ions do contribute to Ag NP-associated toxicity, particularly upon intracellular degradation. The different surface properties of the NPs however result in distinct toxicity profiles for the three NPs, indicating clear NP-associated effects.

The Effect of Intracellular Degradation on Cytotoxicity and Cell Labeling Efficacy of Inorganic Ligand-Stabilized Colloidal CdSe/CdS Quantum Dots

Quantum dots (QDots) are explored in biomedicine as highly fluorescent, photostable nanomaterials, but their use is impeded by their hydrophobic nature. In the present work, we evaluate the potential biomedical use of QDots that have been transferred into the aqueous phase by means of inorganic ligands. CdSe/CdS QDots were prepared and transferred to water upon ligand exchange to S(2-) ions. However, a multiparametric evaluation of the effect of these QDots on multiple cell types revealed significant QDot cytotoxicity. Using optimized methods, the QDots were found to rapidly degrade under endosomal pH, resulting in leached Cd(2+). Together with the induction of oxidative stress, this significantly affected cell viability. Using proliferation-restricted cells, QDot degradation was found to augment cytotoxicity with time resulting in mitochondrial and DNA damage, effects on cell morphology and cell functionality. The final non-cytotoxic concentration was defined at 2 nM, enabling cells to be tracked up to 2 cell divisions. A direct comparison with other QDots and fluorescent particles studied resulted in similar concentrations; however, the functionality of previously analyzed particles was much higher. These data reveal that comparing NP toxicity based on particle concentrations is extremely difficult. A comparison of NPs is better obtained by evaluating NP functionality using a straightforward approach, such as follow-up of QDot fluorescence in dividing cells. These data highlight the importance of (1) considering QDot stability in the intracellular microenvironment, (2) the protective nature of the QDot-stabilizing coating, (3) the need for comparison of particle functionality to understand any observed effects.

Genotoxic capacity of Cd/Se semiconductor quantum dots with differing surface chemistries

Quantum dots (QD) have unique electronic and optical properties promoting biotechnological advances. However, our understanding of the toxicological structure–activity relationships remains limited. This study aimed to determine the biological impact of varying nanomaterial surface chemistry by assessing the interaction of QD with either a negative (carboxyl), neutral (hexadecylamine; HDA) or positive (amine) polymer coating with human lymphoblastoid TK6 cells. Following QD physico-chemical characterisation, cellular uptake was quantified by optical and electron microscopy. Cytotoxicity was evaluated and genotoxicity was characterised using the micronucleus assay (gross chromosomal damage) and the HPRT forward mutation assay (point mutagenicity). Cellular damage mechanisms were also explored, focusing on oxidative stress and mitochondrial damage. Cell uptake, cytotoxicity and genotoxicity were found to be dependent on QD surface chemistry. Carboxyl-QD demonstrated the smallest agglomerate size and greatest cellular uptake, which correlated with a dose dependent increase in cytotoxicity and genotoxicity. Amine-QD induced minimal cellular damage, while HDA-QD promoted substantial induction of cell death and genotoxicity. However, HDA-QD were not internalised by the cells and the damage they caused was most likely due to free cadmium release caused by QD dissolution. Oxidative stress and induced mitochondrial reactive oxygen species were only partially associated with cytotoxicity and genotoxicity induced by the QD, hence were not the only mechanisms of importance. Colloidal stability, nanoparticle (NP) surface chemistry, cellular uptake levels and the intrinsic characteristics of the NPs are therefore critical parameters impacting genotoxicity induced by QD.