Misinterpretation in Nanotoxicology: A Personal Perspective

Holotomography and atomic force microscopy: a powerful combination to enhance cancer, microbiology and nanotoxicology research

Modern imaging strategies are paramount to studying living systems such as cells, bacteria, and fungi and their response to pathogens, toxicants, and nanomaterials (NMs) as modulated by exposure and environmental factors. The need to understand the processes and mechanisms of damage, healing, and cell survivability of living systems continues to motivate the development of alternative imaging strategies. Of particular interest is the use of label-free techniques (microscopy procedures that do not require sample staining) that minimize interference of biological processes by foreign marking substances and reduce intense light exposure and potential photo-toxicity effects. This review focuses on the synergic capabilities of atomic force microscopy (AFM) as a well-developed and robust imaging strategy with demonstrated applications to unravel intimate details in biomedical applications, with the label-free, fast, and enduring Holotomographic Microscopy (HTM) strategy. HTM is a technique that combines holography and tomography using a low intensity continuous illumination laser to investigate (quantitatively and non-invasively) cells, microorganisms, and thin tissue by generating three-dimensional (3D) images and monitoring in real-time inner morphological changes. We first review the operating principles that form the basis for the complementary details provided by these techniques regarding the surface and internal information provided by HTM and AFM, which are essential and complimentary for the development of several biomedical areas studying the interaction mechanisms of NMs with living organisms. First, AFM can provide superb resolution on surface morphology and biomechanical characterization. Second, the quantitative phase capabilities of HTM enable superb modeling and quantification of the volume, surface area, protein content, and mass density of the main components of cells and microorganisms, including the morphology of cells in microbiological systems. These capabilities result from directly quantifying refractive index changes without requiring fluorescent markers or chemicals. As such, HTM is ideal for long-term monitoring of living organisms in conditions close to their natural settings. We present a case-based review of the principal uses of both techniques and their essential contributions to nanomedicine and nanotoxicology (study of the harmful effects of NMs in living organisms), emphasizing cancer and infectious disease control. The synergic impact of the sequential use of these complementary strategies provides a clear drive for adopting these techniques as interdependent fundamental tools.

Exploring the Effects of Various Capping Agents on Zinc Sulfide Quantum Dot Characteristics and In-vitro Fate

The choice of capping agents used during the synthesis process of quantum dots (QDs) can significantly influence their fate and fundamental properties. Hence, choosing an appropriate capping agent is a critical step in both synthesis and biomedical application of QDs. In this research, ZnS QDs were synthesized via chemical precipitation process and three commonly employed capping agents, namely mercaptoethanol (ME), mercaptoacetic acid (MAA), and cysteamine (CA), were used to stabilize the QDs. This study was aimed to examine how these capping agents impact the physicochemical and optical characteristics of ZnS QDs, as well as their interactions with biological systems. The findings revealed that the capping agents had considerable effects on the behavior and properties of ZnS QDs. MAA-QD exhibited superior crystal lattice, smaller size, and significant quantum yield (QY). In contrast, CA-QDs demonstrated the lowest QY and the highest tendency for aggregation. ME-QDs exhibited intermediate characteristics, along with an acceptable level of cytotoxicity, rapid uptake by cells, and efficient escape from lysosomes. Consequently, it is advisable to select capping agents in accordance with the specific objectives of the research.

Novel Gadolinium-Free Ultrasmall Nanostructured Positive Contrast for Magnetic Resonance Angiography and Imaging

Nanostructured contrast agents are promising alternatives to Gd3+-based chelates in magnetic resonance (MR) imaging techniques. A novel ultrasmall paramagnetic nanoparticle (UPN) was strategically designed to maximize the number of exposed paramagnetic sites and r1 while minimizing r2, by decorating 3 nm titanium dioxide nanoparticles with suitable amounts of iron oxide. Its relaxometric parameters are comparable to those of gadoteric acid (GA) in agar phantoms, and the r2/r1 ratio of 1.38 at 3 T is close to the ideal unitary value. The strong and prolonged contrast enhancement of UPN before renal excretion was confirmed by T1-weighted MR images of Wistar rats after intravenous bolus injection. Those results associated with good biocompatibility indicate its high potential as an alternative blood-pool contrast agent to the GA gold standard for MR angiography, especially for patients with severe renal impairment.

Quick and Mild Isolation of Intact Lysosomes Using Magnetic-Plasmonic Hybrid Nanoparticles

Rapid and efficient isolation of intact lysosomes is necessary to study their functions and metabolites by proteomic analysis. We developed a swift and robust nanoparticle-based magnetic separation method in which magnetic-plasmonic hybrid nanoparticles (MPNPs) conjugated with amino dextran (aDxt) were targeted to the lumen of lysosomes via the endocytosis pathway. For well-directed magnetic separation of the lysosomes, it is important to trace the intracellular trafficking of the aDxt-conjugated MPNPs (aDxt-MPNPs) in the endocytosis pathway. Therefore, we analyzed the intracellular transport process of the aDxt-MPNPs by investigating the time-dependent colocalization of plasmonic scattering of aDxt-MPNPs and immunostained marker proteins of organelles using the threshold Manders' colocalization coefficient (R_t). Detailed analysis of time variations of R_t for early and late endosomes and lysosomes allowed us to derive the transport kinetics of aDxt-MPNPs in a cell. After confirming the incubation time required for sufficient accumulation of aDxt-MPNPs in lysosomes, the lysosomes were magnetically isolated as intact as possible. By varying the elapsed time from homogenization to complete isolation of lysosomes (t_delay) and temperature (T), the influences of t_delay and T on the protein composition of the lysosomes were investigated by polyacrylamide gel electrophoresis and amino acid analysis. We found that the intactness of lysosomes could become impaired quite quickly, and to isolate lysosomes as intact as possible with high purity, t_delay = 30 min and T = 4 °C were optimal settings.

Titanium and Iron Oxide Nanoparticles for Cancer Therapy: Surface Chemistry and Biological Implications

Currently, cancer is among the most challenging diseases due to its ability to continuously evolve into a more complex muldimentional system, in addition to its high capability to spread to other organs and tissues. In this context, the relevance of nanobiomaterials (NBMs) for the development of new more effective and less harmful treatments is increasing. NBMs provide the possibility of combining several functionalities on a single system, expectedly in a synergic way, to better perform the treatment and cure. However, the control of properties such as colloidal stability, circulation time, pharmacokinetics, and biodistribution, assuring the concentration in specific target tissues and organs, while keeping all desired properties, tends to be dependent on subtle changes in surface chemistry. Hence, the behavior of such materials in different media/environments is of uttermost relevance and concern since it can compromise their efficiency and safety on application. Given the bright perspectives, many efforts have been focused on the development of nanomaterials fulfilling the requirements for real application. These include robust and reproducible preparation methods to avoid aggregation while preserving the interaction properties. The possible impact of nanomaterials in different forms of diagnosis and therapy has been demonstrated in the past few years, given the perspectives on how revolutionary they can be in medicine and health. Considering the high biocompatibility and suitability, this review is focused on titanium dioxide– and iron oxide–based nanoagents highlighting the current trends and main advancements in the research for cancer therapies. The effects of phenomena, such as aggregation and agglomeration, the formation of the corona layer, and how they can compromise relevant properties of nanomaterials and their potential applicability, are also addressed. In short, this review summarizes the current understanding and perspectives on such smart nanobiomaterials for diagnostics, treatment, and theranostics of diseases.

Biocompatible DNA/5-Fluorouracil-Gemini Surfactant-Functionalized Gold Nanoparticles as Promising Vectors in Lung Cancer Therapy

The design and preparation of novel nanocarriers to transport cancer drugs for chemotherapy purposes is an important line of research in the medical field. A new 5-fluorouracil (5-Fu) transporter was designed based on the use of two new biocompatible gold nanosystems: (i) a gold nanoparticle precursor, Au@16-Ph-16, stabilized with the positively charged gemini surfactant 16-Ph-16, and (ii) the compacted nanocomplexes formed by the precursor and DNA/5-Fu complexes, Au@16-Ph-16/DNA-5-Fu. The physicochemical properties of the obtained nanosystems were studied by using UV-visible spectroscopy, TEM, dynamic light scattering, and zeta potential techniques. Method tuning also requires the use of circular dichroism, atomic force microscopy, and fluorescence spectroscopy techniques for the prior selection of the optimal relative Au@16-Ph-16 and DNA concentrations (R = CAu@16-Ph-16/CDNA), biopolymer compaction/decompaction, and 5-Fu release from the DNA/5-Fu complex. TEM experiments revealed the effective internalization of the both precursor and Au@16-Ph-16/DNA-5-Fu-compacted nanosystems into the cells. Moreover, cytotoxicity assays and internalization experiments using TEM and confocal microscopy showed that the new strategy for 5-Fu administration enhanced efficacy, biocompatibility and selectivity against lung cancer cells. The differential uptake among different formulations is discussed in terms of the physicochemical properties of the nanosystems.

Evaluation of the environmental impact of magnetic nanostructured materials at different trophic levels

Safety on the use of magnetic nanomaterials (MNMs) has become an active topic of research given all the recent applications of these materials in various fields. It is known that the toxicity of MNMs depends on size, shape, and surface functionalization. In this study, we evaluate the biocompatibility with different aquatic organisms of engineered MNMs-CIT with excellent aqueous dispersion and long-term colloidal stability. Primary producers (the alga Pseudokirchneriella subcapitata), primary consumers (the rotifer Lecane papuana), and predators (the fish, Danio rerio) interacted with these materials in acute and sub-chronic toxicity tests. Our results indicate that P. subcaptita was the most sensitive taxon to MNMs-CIT. Inhibition of their population growth (IC₅₀ = 22.84 mg L^-1) elicited cell malformations and increased the content of photosynthetic pigments, likely due to inhibition of cell division (as demonstrated in AFM analysis). For L. papuana, the acute exposure to MNMs shows no significant mortality. However, adverse effects such as decreased rate of population and altered swimming patterns arise after chronic interaction with MNMs. For D. rerio organisms on early life stages, their exposure to MNMs results in delayed hatching of eggs, diminished survival of larvae, altered energy resources allocation (measured as the content of total carbohydrates, lipids, and protein), and increased glucose demand. As to our knowledge, this is the first study that includes three different trophic levels to assess the effect of MNMs in aquatic organisms; furthermore, we demonstrated that these MNMs pose hazards on aquatic food webs at low concentrations (few mgL^-1).

A meta-analysis framework to assess the role of units in describing nanoparticle toxicity

Despite ample research on nanoparticles, their environmental toxicity is still debatable. The lack of consensus is due in part to the challenge of comparing studies because of variability in parameters like test organism, test medium, and duration of experiment. However, the unit used to compare the toxicology of nanoparticles is one variable that experimentalists can control. Traditionally, mass per volume is the most common unit used to make comparisons, but there is growing evidence that alternative units such as surface area per volume or particles per volume may provide a better and more mechanistic measure of toxicity. Herein, we propose and test a meta-analytic framework to study the effect of units on nanotoxicology using data from the NanoE-Tox database, a freely available database containing 1518 toxicology values from 224 published articles of which 42 records met our basic inclusion criteria. These data were augmented with more recent data published over the past five years as archived by the Web of Science citation index. An additional 27 records from 1676 papers met the inclusion criteria and were also included in the analysis. The meta-analysis framework measures the degree of heterogeneity for each of three units (grams/L, particles/L, surface area/L) grouped by the type of test organism, particle chemistry, and manner in which a nanoparticle's size was measured (e.g., nominal particle size reported by the manufacturer vs. measurement of size for particles suspended in the liquid medium used in a subsequent toxicity experiment). The result of the meta-analysis reveals that surface area per volume reduces the heterogeneity in the Ag crustacean subgroup when nanoparticle size was measured in the test medium, and the ZnO crustacean subgroup when nanoparticle size was measured out the test medium and may therefore be a more appropriate estimate of the toxicity of soluble nanoparticles. No subgroups in our analysis showed a reduction in heterogeneity for particles per volume in either soluble or insoluble nanoparticles. The lack of conclusion on insoluble nanoparticles was not due to a limitation of our meta-analysis but rather highlights a critical deficiency in the primary literature. The majority of published studies fail to report common measures of error that are essential for further analysis (i.e. error of the measured nanoparticle size and/or interoperable error of the measured half-maximal concentration of the toxic endpoint). If future nanotoxicity studies report such error, as they should, then the framework of our meta-analysis could be used more broadly to provide a simple, statistically rigorous way to assess the role of units on the toxicity of nanoparticles.

Surface-Engineered Cancer Nanomedicine: Rational Design and Recent Progress

Cancer is highly heterogeneous in nature and characterized by abnormal, uncontrolled cells' growth. It is responsible for the second leading cause of death in the world. Nanotechnology is explored profoundly for sitespecific delivery of cancer chemotherapeutics as well as overcome multidrug-resistance (MDR) challenges in cancer. The progress in the design of various smart biocompatible materials (such as polymers, lipids and inorganic materials) has now revolutionized the area of cancer research for the rational design of nanomedicine by surface engineering with targeting ligands. The small tunable size and surface properties of nanomedicines provide the opportunity of multiple payloads and multivalent-ligand targeting to achieve drug efficacy even in MDR cancer. Furthermore, efforts are being carried out for the development of novel nano-pharmaceutical design, focusing on the delivery of therapeutic and diagnostic agents simultaneously which is called theranostics to assess the progress of therapy in cancer. This review aimed to discuss the physicochemical manipulation of cancer nanomedicine for rational design and recent progress in the area of surface engineering of nanomedicines to improve the efficacy of cancer chemotherapeutics in MDR cancer as well. Moreover, the problem of toxicity of the advanced functional materials that are used in nanomedicines and are exploited to achieve drug targeting in cancer is also addressed.

Natural TiO2-Nanoparticles in Soils: A Review on Current and Potential Extraction Methods

The monitoring of anthropogenic TiO2-nanoparticles in soils is challenged by the knowledge gap on their characteristics of the large natural TiO2-nanoparticle pool. Currently, no efficient method is available for characterizing natural TiO2-nanoparticles in soils without an extraction procedure. Considering the reported diversity of extraction methods, the following article reviews and discusses their potential for TiO2 from soils, focusing on the selectivity and the applicability to complex samples. It is imperative to develop a preparative step reducing analytical interferences and producing a stable colloidal dispersion. It is suggested that an oxidative treatment, followed by alkaline conditioning and the application of dispersive agents, achieve such task. This enables the further separation and characterization through size or surface-based separation (i.e., hydrodynamic fractionation methods, filtration or sequential centrifugation). Meanwhile, cloud point extraction, gel electrophoresis, and electrophoretic deposition have been studied on various nanoparticles but not on TiO2-nanoparticles. Furthermore, industrially applied methods in, for example, kaolin processing (flotation and flocculation) are interesting but require further improvements on terms of selectivity and applicability to soil samples. Overall, none of the current extraction methods is sufficient toward TiO2; however, further optimization or combination of orthogonal techniques could help reaching a fair selectivity toward TiO2.

Toxicologic Evaluation for Amorphous Silica Nanoparticles: Genotoxic and Non-Genotoxic Tumor-Promoting Potential

Amorphous silica nanoparticles (SiO₂NPs) have been widely used in medicine including targeted drug/DNA delivery, cancer therapy, and enzyme immobilization. Nevertheless, SiO₂NPs should be used with caution due to safety concerns associated with unique physical and chemical characteristics. The objective of this study was to determine the effects of SiO₂NPs on genotoxic and non-genotoxic mechanisms associated with abnormal gap junctional intercellular communication (GJIC) in multistage carcinogenesis. The SiO₂NPs exhibited negative responses in standard genotoxicity tests including the Ames test, chromosome aberration assay, and micronucleus assay. In contrast, the SiO₂NPs significantly induced DNA breakage in comet assay. Meanwhile, SiO₂NPs inhibited GJIC based on the results of scrape/loading dye transfer assay for the identification of non-genotoxic tumor-promoting potential. The reduction in expression and plasma membrane localization of Cx43 was detected following SiO₂NP treatment. Particularly, SiO₂NP treatment increased Cx43 phosphorylation state, which was significantly attenuated by inhibitors of extracellular signal-regulated kinases 1/2 (ERK1/2) and threonine and tyrosine kinase (MEK), but not by protein kinase C (PKC) inhibitor. Taken together, in addition to a significant increase in DNA breakage, SiO₂NP treatment resulted in GJIC dysregulation involved in Cx43 phosphorylation through the activation of mitogen-activated protein kinase (MAPK) signaling. Overall findings of the genotoxic and non-genotoxic carcinogenic potential of SiO₂NPs provide useful toxicological information for clinical application at an appropriate dose.

Stable, concentrated, biocompatible, and defect-free graphene dispersions with positive charge

The outstanding properties of graphene offer high potential for biomedical applications. In this framework, positively charged nanomaterials show better interactions with the biological environment, hence there is strong interest in the production of positively charged graphene nanosheets. Currently, production of cationic graphene is either time consuming or producing dispersions with poor stability, which strongly limit their use in the biomedical field. In this study, we made a family of new cationic pyrenes, and have used them to successfully produce water-based, highly concentrated, stable, and defect-free graphene dispersions with positive charge. The use of different pyrene derivatives as well as molecular dynamics simulations allowed us to get insights on the nanoscale interactions required to achieve efficient exfoliation and stabilisation. The cationic graphene dispersions show outstanding biocompatibility and cellular uptake as well as exceptional colloidal stability in the biological medium, making this material extremely attractive for biomedical applications.

Understanding the relevance of protein corona in nanoparticle-based therapeutics and diagnostics

Over the past few decades, nanoparticle-based therapeutic and diagnostic systems have gained immense recognition. A relative improvement in the status of the global cancer burden has been successful due to the advent of nanoparticle-based formulations. However, exposure of nanoparticles (NPs) to a real-time biological media alters its native identity due to the formation of the biomolecular corona. Such biological interactions hinder the efficiency of the NPs system. The parameters that govern such intricate interaction are generally overlooked while designing nano drugs and delivery systems (nano-DDS). Fabricating nano-DDS with prolonged circulation time, enhanced drug-loading, and release capacity along with efficient clearance, remain the primary concerns associated with cancer therapeutics. This present review firstly aims to summarize the critical aspects that influence protein coronation on therapeutic nanoparticles designed for anti-cancer therapy. The role of protein corona in modifying the overall pharmacodynamics of the nanoparticle-based DDS has been discussed. Further, the studies and patents that extend the concept of protein corona into diagnostics have been elaborated. An understanding of the pros and cons associated with protein coronation would not only help us gain better insights into the fabrication of effective anti-cancer drug-delivery systems but also improve the shortcomings related to the clinical translation of these nanotherapeutics.

Protein corona and its applications.

Development and Assessment of Nano-Technologies for Cancer Treatment: Cytotoxicity and Hyperthermia Laboratory Studies

Cancer treatment by magnetic hyperthermia offers numerous advantages, but for practical applications many variables still need to be adjusted before developing a controlled and reproducible cancer treatment that is bio-compatible (non-damaging) to healthy cells. In this work, Fe₃O₄ and CoFe₂O₄ were synthesized and systematically studied for the development of efficient therapeutic agents for applications in hyperthermia. The biocompatibility of the materials was further evaluated using HepG2 cells as biological model. Colorimetric and microscopic techniques were used to evaluate the interaction of magnetic nano-materials (MNMs) and HepG2 cells. Finally, the behavior of MNMs was evaluated under the influence of an alternating magnetic field (AMF), observing a more efficient temperature increment for CoFe₂O₄, a desirable behavior for biomedical applications since lower doses and shorter expositions to alternating magnetic field might be required.

Intracellular ROS Induction by Ag@ZnO Core-Shell Nanoparticles: Frontiers of Permanent Optically Active Holes in Breast Cancer Theranostic

In this study, we investigated whether ZnO coating on Ag nanoparticles (NPs) tunes electron flux and hole figuration at the metal-semiconductor interface under UV radiation. This effect triggers the photoactivity and generation of reactive oxygen species from Ag@ZnO NPs, which results in enhanced cytotoxic effects and apoptotic cell death in human breast cancer cells (MDA-MB231). In this context, upregulation of apoptotic cascade proteins (i.e., Bax/Bcl2 association, p53, cytochrome c, and caspase-3) along with activation of oxidative stress proteins suggested the occurrence of apoptosis by Ag@ZnO NPs in cancer cells through the mitochondrial pathway. Also, preincubation of breast cancer cells with Ag@ZnO NPs in dark conditions muted NP-related toxic effects and consequent apoptotic fate, highlighting biocompatible properties of unexcited Ag@ZnO NPs. Furthermore, the diagnostic efficacy of Ag@ZnO NPs as computed tomography (CT)/optical nanoprobes was investigated. Results confirmed the efficacy of the photoactivated system in obtaining desirable outcomes from CT/optical imaging, which represents novel theranostic NPs for simultaneous imaging and treatment of cancer.

Biomolecular Corona Dictates Aβ Fibrillation Process

Amyloid beta (Aβ), which forms toxic oligomers and fibrils in brain tissues of patients with Alzheimer's disease, is broadly used as a model protein to probe the effect of nanoparticles (NPs) on oligomerization and fibrillation processes. However, the majority of the reports in the field have ignored the effect of the biomolecular corona on the fibrillogenesis of the Aβ proteins. The biomolecular corona, which is a layer composed of various types of biomolecules that covers the surface of NPs upon their interaction with biological fluids, determines the biological fates of NPs. Therefore, during in vivo interaction of NPs with Aβ protein, what the Aβ actually "sees" is the human plasma and/or cerebrospinal fluid (CSF) biomolecular-coated NPs rather than the pristine surface of NPs. Here, to mimic the in vivo effects of therapeutic NPs as antifibrillation agents, we probed the effects of a biomolecular corona derived from human CSF and/or plasma on Aβ fibrillation. The results demonstrated that the type of biomolecular corona can dictate the inhibitory or acceleratory effect of NPs on Aβ_1-42 and Aβ_25-35 fibrillation processes. More specifically, we found that the plasma biomolecular-corona-coated gold NPs, with sphere and rod shapes, has less inhibitory effect on Aβ_1-42 fibrillation kinetics compared with CSF biomolecular-corona-coated and pristine NPs. Opposite results were obtained for Aβ_25-35 peptide, where the pristine NPs accelerated the Aβ_25-35 fibrillation process, whereas corona-coated ones demonstrated an inhibitory effect. In addition, the CSF biomolecular corona had less inhibitory effect than those obtained from plasma.

Disease-related metabolites affect protein-nanoparticle interactions

Once in biological fluids, the surface of nanoparticles (NPs) is rapidly covered with a layer of biomolecules (i.e., the "protein corona") whose composition strongly determines their biological identity, regulates interactions with biological entities including cells and the immune system, and consequently directs the biological fate and pharmacokinetics of nanoparticles. We recently introduced the concept of a "personalized protein corona" which refers to the formation of different biological identities of the exact same type of NP after being exposed to extract plasmas from individuals who have various types of diseases. As different diseases have distinct metabolomic profiles and metabolites can interact with proteins, it is legitimate to hypothesize that metabolomic profiles in plasma may have the capacity to, at least partially, drive the formation of a personalized protein corona. To test this hypothesis, we employed a multi-scale approach composed of coarse-grained (CG) and all atom (AA) molecular dynamics (MD) simulations to probe the role of glucose and cholesterol (model metabolites in diabetes and hypercholesterolemia patients) in the interaction of fibrinogen protein and polystyrene NPs. Our results revealed that glucose and cholesterol had the capacity to induce substantial changes in the binding site of fibrinogen to the surface of NPs. More specifically, the simulation results demonstrated that increasing the metabolite amount could change the profiles of fibrinogen adsorption and replacement, what is known as the Vroman effect, on the NP surface. In addition, we also found out that metabolites can substantially determine the immune triggering potency of the fibrinogen-NP complex. Our proof-of-concept outcomes further emphasize the need for the development of patient-specific NPs in a disease type-specific manner for high yielding and safe clinical applications.

Effect of Cell Sex on Uptake of Nanoparticles: The Overlooked Factor at the Nanobio Interface

Cellular uptake of nanoparticles (NPs) depends on the nature of the nanobio system including the solid nanocomponents ( e. g., physicochemical properties of NPs), nanobio interfaces ( e. g., protein corona composition), and the cellular characteristics ( e. g., cell type). In this study, we document the role of sex in cellular uptake of NPs as an "overlooked" factor in nanobio interface investigations. We demonstrate that cell sex leads to differences in NP uptake between male and female human amniotic stem cells (hAMSCs), with greater uptake by female cells. hAMSCs are one of the earliest sources of somatic stem cells. The experiments were replicated with primary fibroblasts isolated from the salivary gland of adult male and female donors of similar ages, and again the extent of NP uptake was altered by cell sex. However, in contrast to hAMSCs, uptake was greater in male cells. We also found out that female versus male amniotic stem cells exhibited different responses to reprogramming into induced pluripotent stem cells (iPSCs) by the Yamanaka factors. Thus, future studies should consider the effect of sex on the nanobio interactions to optimize clinical translation of NPs and iPSC biology and to help researchers to better design and produce safe and efficient therapeutic sex-specific NPs.

Debugging Nano-Bio Interfaces: Systematic Strategies to Accelerate Clinical Translation of Nanotechnologies

Despite considerable efforts in the field of nanomedicine that have been made by researchers, funding agencies, entrepreneurs, and the media, fewer nanoparticle (NP) technologies than expected have made it to clinical trials. The wide gap between the efforts and effective clinical translation is, at least in part, due to multiple overlooked factors in both in vitro and in vivo environments, a poor understanding of the nano-bio interface, and misinterpretation of the data collected in vitro, all of which reduce the accuracy of predictions regarding the NPs' fate and safety in humans. To minimize this bench-to-clinic gap, which may accelerate successful clinical translation of NPs, this opinion paper aims to introduce strategies for systematic debugging of nano-bio interfaces in the current literature.

Entry of nanoparticles into cells: the importance of nanoparticle properties

Knowledge of the interactions between nanoparticles (NPs) and cell membranes is of great importance for the design of safe and efficient nanomedicines.

Silver nanoparticles or free silver ions work? An enantioselective phytotoxicity study with a chiral tool

Nowadays, silver nanoparticles (AgNP) have been widely used and there are raising concerns about their potential adverse effects on organism. As for the exact toxicity mechanism of AgNP, opinions still vary and whether the released silver ions (Ag⁺) or AgNP themselves are responsible for the toxicity remains debatable. In the present study, we have designed two exposure systems where Ag⁺ and AgNP coexisted but differed in quantification by using photo-reduced method with cysteine enantiomers, and their toxicities to freshwater microalgae Scenedesmus obliquus and model plant Arabidopsis thaliana were determined. In the results, Ag⁺ was in suit photo-reduced by cysteine enantiomers, and the UV-Vis and circular dichroism spectrum evidence confirmed the quantification difference between Ag-l-cysteine (Ag-l-Cys) and Ag-d-cysteine (Ag-d-Cys), where there was more AgNP and less Ag⁺ in Ag-l-Cys. Furthermore, the toxicity assay data revealed that Ag-d-Cys was more toxic to S. obliquus but A. thaliana was more susceptible to Ag-l-Cys. The metal element distribution in Arabidopsis leaves was also influenced in an enantioselective manner, which was related to the oxidative stress. Considering the quantification difference between Ag-l-Cys and Ag-d-Cys, it can be concluded that AgNP exhibited their toxicity to S. obliquus by the action of Ag⁺, but toxicity brought to A. thaliana was attributed to AgNP themselves rather than Ag⁺. The results of the present study help to better clarify the role of Ag⁺ in AgNP toxicity and offer a chiral tool and a new sight to investigate the toxicity mechanism of AgNP.

Characterizing Nanoparticles in Biological Matrices: Tipping Points in Agglomeration State and Cellular Delivery In Vitro

Understanding the delivered cellular dose of nanoparticles is imperative in nanomedicine and nanosafety, yet is known to be extremely complex because of multiple interactions between nanoparticles, their environment, and the cells. Here, we use 3-D reconstruction of agglomerates preserved by cryogenic snapshot sampling and imaged by electron microscopy to quantify the "bioavailable dose" that is presented at the cell surface and formed by the process of individual nanoparticle sequestration into agglomerates in the exposure media. Critically, using 20 and 40 nm carboxylated polystyrene-latex and 16 and 85 nm silicon dioxide nanoparticles, we show that abrupt, dose-dependent "tipping points" in agglomeration state can arise, subsequently affecting cellular delivery and increasing toxicity. These changes are triggered by shifts in the ratio of the total nanoparticle surface area to biomolecule abundance, with the switch to a highly agglomerated state effectively changing the test article midassay, challenging the dose-response paradigm for nanosafety experiments. By characterizing nanoparticle numbers per agglomerate, we show these tipping points can lead to the formation of extreme agglomeration states whereby 90% of an administered dose is contained and delivered to the cells by just the top 2% of the largest agglomerates. We thus demonstrate precise definition, description, and comparison of the nanoparticle dose formed in different experimental environments and show that this description is critical to understanding cellular delivery and toxicity. We further empirically "stress-test" the commonly used dynamic light scattering approach, establishing its limitations to present an analysis strategy that significantly improves the usefulness of this popular nanoparticle characterization technique.

Cellular uptake of nanoparticles: journey inside the cell

Nanoscale materials are increasingly found in consumer goods, electronics, and pharmaceuticals. While these particles interact with the body in myriad ways, their beneficial and/or deleterious effects ultimately arise from interactions at the cellular and subcellular level. Nanoparticles (NPs) can modulate cell fate, induce or prevent mutations, initiate cell-cell communication, and modulate cell structure in a manner dictated largely by phenomena at the nano-bio interface. Recent advances in chemical synthesis have yielded new nanoscale materials with precisely defined biochemical features, and emerging analytical techniques have shed light on nuanced and context-dependent nano-bio interactions within cells. In this review, we provide an objective and comprehensive account of our current understanding of the cellular uptake of NPs and the underlying parameters controlling the nano-cellular interactions, along with the available analytical techniques to follow and track these processes.

Exposure to Engineered Nanomaterials: Impact on DNA Repair Pathways

Some engineered nanomaterials (ENMs) may have the potential to cause damage to the genetic material in living systems. The mechanistic machinery functioning at the cellular/molecular level, in the form of DNA repair processes, has evolved to help circumvent DNA damage caused by exposure to a variety of foreign substances. Recent studies have contributed to our understanding of the various DNA damage repair pathways involved in the processing of DNA damage. However, the vast array of ENMs may present a relatively new challenge to the integrity of the human genome; therefore, the potential hazard posed by some ENMs necessitates the evaluation and understanding of ENM-induced DNA damage repair pathways. This review focuses on recent studies highlighting the differential regulation of DNA repair pathways, in response to a variety of ENMs, and discusses the various factors that dictate aberrant repair processes, including intracellular signalling, spatial interactions and ENM-specific responses.

Advances in Alzheimer's Diagnosis and Therapy: The Implications of Nanotechnology

Alzheimer's disease (AD) is a type of dementia that causes major issues for patients' memory, thinking, and behavior. Despite efforts to advance AD diagnostic and therapeutic tools, AD remains incurable due to its complex and multifactorial nature and lack of effective diagnostics/therapeutics. Nanoparticles (NPs) have demonstrated the potential to overcome the challenges and limitations associated with traditional diagnostics/therapeutics. Nanotechnology is now offering new tools and insights to advance our understanding of AD and eventually may offer new hope to AD patients. Here, we review the key roles of nanotechnologies in the recent literature, in both diagnostic and therapeutic aspects of AD, and discuss how these achievements may improve patient prognosis and quality of life.

Personalized protein corona on nanoparticles and its clinical implications

It is now well understood that once in contact with biological fluids, nanoscale objects lose their original identity and acquire a new biological character, referred to as a protein corona. The protein corona changes many of the physicochemical properties of nanoparticles, including size, surface charge, and aggregation state. These changes, in turn, affect the biological fate of nanoparticles, including their pharmacokinetics, biodistribution, and therapeutic efficacy. It is progressively being accepted that even slight variations in the composition of a protein source (e.g., plasma and serum) can substantially change the composition of the corona formed on the surface of the exact same nanoparticles. Recently it has been shown that the protein corona is strongly affected by the patient's specific disease. Therefore, the same nanomaterial incubated with plasma proteins of patients with different pathologies adsorb protein coronas with different compositions, giving rise to the concept of personalized protein corona. Herein, we review this concept along with recent advances on the topic, with a particular focus on clinical relevance.