Analytical methods to assess nanoparticle toxicity

Investigation of a broad diversity of nanoparticles, including their processes, as well as toxicity testing in diverse organs and systems

Nanotechnology arising in wide-ranging areas, covers extensively different ranges of approaches attained from fields such as biology, chemistry, physics, and medicine engineering. Nanoparticles are a necessary part of nanotechnology effectually applied in the cure of a number of diseases. Nanoparticles have gained significant importance due to their unique properties, which differ from their bulk counterparts. These distinct properties of nanoparticles are primarily influenced by their morphology, size, and size distribution. At the nanoscale, nanoparticles exhibit behaviours that can enhance therapeutic efficacy and reduce drug toxicity. Their small size and large surface area make them promising candidates for applications such as targeted drug delivery, where they can improve treatment outcomes while minimizing adverse effects. The harmful effects of nanoparticles on the environment were critically investigated to obtain appropriate results and reduce the risk by incorporating the materials. Nanoparticles tend to penetrate the human body, clear the biological barriers to reach sensitive organs and are easily incorporated into human tissue, as well as dispersing to the hepatic tissues, heart tissues, encephalum, and GI tract. This study aims to examine a wide variety of nanoparticles, focusing on their manufacturing methods, functional characteristics, and interactions within biological systems. Particular attention will be directed towards assessing the toxicity of nanoparticles in different organs and physiological systems, yielding a thorough comprehension of their potential health hazards and the processes that drive nanoparticle-induced toxicity. This analysis will also emphasize recent developments in nanoparticle applications and safety assessment methodologies.

Precise tracking of nanoparticles in plant roots

One of the foremost challenges in nanobiotechnology is obtaining direct evidence of nanoparticles' absorption and internalization in plants. Although confocal laser scanning microscopy (CLSM) or transmission electron microscopy (TEM) are currently the most commonly used tools to characterize nanoparticles in plants, subjectivity of researchers, incorrect sample handling, inevitable fluorescence leakage and limitations of imaging instruments lead to false positives and non-reproducibility of experimental results. This protocol provides an easy-to-operate dual-step method, combining CLSM for macroscopic tissue examination and TEM for cellular-level analysis, to effectively trace single particles in plant roots with accuracy and precision. In addition, we also provide detailed methods for processing plant materials before imaging, including cleaning, and staining, to maximize the accuracy and reliability of imaging. This protocol involves currently commonly used nanomaterial types, such as metal-based and doped carbon-based materials, and enables accurate localization of nanoparticles with different sizes at the cell level in Arabidopsis thaliana root samples either through contrast or element mapping analysis. It serves as a valuable reference and benchmark for scholars in plant science, chemistry and environmental studies to understand the interaction between plant roots and nanomaterials and to detect the distribution of nanomaterials in plants. Excluding plant culture time, the protocol can be completed in 4-5 d.

Effects of Zinc Oxide Nanoparticle Exposure on Human Glial Cells and Zebrafish Embryos

Zinc oxide nanoparticles (ZnO NPs) are among the most widely used nanomaterials. They have multiple applications in cosmetics, textiles, paints, electronics and, recently, also in biomedicine. This extensive use of ZnO NPs notably increases the probability that both humans and wildlife are subjected to undesirable effects. Despite being among the most studied NPs from a toxicological point of view, much remains unknown about their ecotoxicological effects or how they may affect specific cell types, such as cells of the central nervous system. The main objective of this work was to investigate the effects of ZnO NPs on human glial cells and zebrafish embryo development and to explore the role of the released Zn2+ ions in these effects. The effects on cell viability on human A172 glial cells were assessed with an MTT assay and morphological analysis. The potential acute and developmental toxicity was assessed employing zebrafish (Danio rerio) embryos. To determine the role of Zn2+ ions in the in vitro and in vivo observed effects, we measured their release from ZnO NPs with flame atomic absorption spectrometry. Then, cells and zebrafish embryos were treated with a water-soluble salt (zinc sulfate) at concentrations that equal the number of Zn2+ ions released by the tested concentrations of ZnO NPs. Exposure to ZnO NPs induced morphological alterations and a significant decrease in cell viability depending on the concentration and duration of treatment, even after removing the overestimation due to NP interference. Although there were no signs of acute toxicity in zebrafish embryos, a decrease in hatching was detected after exposure to the highest ZnO NP concentrations tested. The ability of ZnO NPs to release Zn2+ ions into the medium in a concentration-dependent manner was confirmed. Zn2+ ions did not seem entirely responsible for the effects observed in the glial cells, but they were likely responsible for the decrease in zebrafish hatching rate. The results obtained in this work contribute to the knowledge of the toxicological potential of ZnO NPs.

Determination of mRNA copy number in degradable lipid nanoparticles via density contrast analytical ultracentrifugation

Lipid nanoparticles as delivery system for mRNA have recently attracted attention to a broader audience as COVID-19 mRNA vaccines. Their low immunogenicity and capability to deliver a variety of nucleic acids renders them an interesting and complementary alternative to gene therapy vectors like AAVs. An important quality attribute of LNPs is the copy number of the encapsulated cargo molecule. This work describes how density and molecular weight distributions obtained by density contrast sedimentation velocity can be used to calculate the mRNA copy number of a degradable lipid nanoparticle formulation. The determined average copy number of 5 mRNA molecules per LNP is consistent with the previous studies using other biophysical techniques, such as single particle imaging microscopy and multi-laser cylindrical illumination confocal spectroscopy (CICS).

Gold cluster encapsulated liposomes: theranostic agent with stimulus triggered release capability

Cancer is a major cause of death worldwide. Cancer-resistant to chemo or radiotherapy treatment is a challenge that could be overcome by a nanotechnology approach. Providing a theranostic nano-platform for different cancer treatment strategies could be revolutionary. Here we introduce a multifunctional theranostic nanostructure which has the capacity for improving cancer diagnosis and treatment through better chemo and radiotherapy and current x-ray imaging systems through co-encapsulation of a small gold cluster and anticancer drug doxorubicin. 2 nm gold clusters represent good heating under radio frequency electric field (RF-EF) exposure and have been used for in vitro hyperthermia treatment of cancerous cells. Liposomal doxorubicin (169 ± 19.8 nm) with gold clusters encapsulation efficiency of 13.2 ± 3.0% and doxorubicin encapsulation efficiency of 64.7 ± 0.7% were prepared and studied as a theranostic agent with a high potential in different cancer treatment modalities. Exposure to a radiofrequency electric field on prepared formulation caused 20.2 ± 2.1% drug release and twice decreasing of IC50 on colorectal carcinoma cells. X-ray attenuation efficiency of the liposomal gold cluster was better than commercial iohexol and free gold clusters in different concentrations. Finally, treatment of gold clusters on cancerous cells results in a significant decrease in the viability of irradiated cells to cobalt-60 beam. Based on these experiments, we concluded that the conventional liposomal formulation of doxorubicin that has been co-encapsulated with small gold clusters could be a suitable theranostic nanostructure for cancer treatment and merits further investigation.

2D MoS2 and BN Nanosheets Damage Mitochondria through Membrane Penetration

With the progression of nanotechnology, a growing number of nanomaterials have been created and incorporated into organisms and ecosystems, which raises significant concern about potential hazards of these materials on human health, wildlife, and the environment. Two-dimensional (2D) nanomaterials are one type of nanomaterials with thicknesses ranging from that of a single atom or of several atoms and have been proposed for a variety of biomedical applications such as drug delivery and gene therapy, but the toxicity thereof on subcellular organelles remains to be studied. In this work, we studied the impact of two typical 2D nanomaterials, MoS₂ and BN nanosheets, on mitochondria, which are a type of membranous subcellular organelle that provides energy to cells. While 2D nanomaterials at a low dose exhibited a negligible cell mortality rate, significant mitochondrial fragmentation and partially reduced mitochondrial functions occurred; cells initiate mitophagy in response to mitochondrial damages, which cleans damaged mitochondria to avoid damage accumulation. Moreover, the molecular dynamics simulation results revealed that both MoS₂ and BN nanosheets can spontaneously penetrate the mitochondrial lipid membrane through the hydrophobic interaction. The membrane penetration induced heterogeneous lipid packing resulting in damages. Our results demonstrate that even at a low dose 2D nanomaterials can physically damage mitochondria by penetrating the membrane, which draws attention to carefully evaluating the cytotoxicity of 2D nanomaterials for the potential biomedical application.

In Vitro Photodynamic Treatment Modality for A375 Melanoma Cell Line Using a Sulphonated Aluminum Phthalocyanine Chloride-Photosensitizer-Gold Nanoparticle Conjugate

Metastatic melanoma cancer stem cells are subpopulations that have been identified and linked to tumor progression, immunoevasive behavior, drug resistance, and metastasis, leading to a poor prognosis. Photodynamic therapy (PDT) is an approach to eradicate cancer through a photochemical process which directly generates reactive oxygen species (ROS). This study investigated the impact of PDT using an aluminum phthalocyanine gold nanoparticle (AlPcS₄Cl-AuNP) conjugate for targeting melanoma stem cells. The isolated stem cells were irradiated at 673.2 nm with a radiant exposure of 5 J/cm². Post-irradiation signs of cell death were determined using microscopy and biochemical assays. A possible enhanced effect of ROS in inducing cell death could be seen when AlPcS₄Cl was conjugated to AuNPs. Nanoparticles as carriers promote the efficient cellular uptake of photosensitizers, enhancing organelle accumulation and the targeted therapy of cancerous cells. A biochemical assay revealed significant post-irradiation signs of cell death. The measurement of adenosine triphosphate (ATP) content revealed a decrease in cell proliferation. The study suggested an approach directed at expanding the knowledge on PDT to improve cancer treatment. Understanding the cell death mechanism through which ROS influence cancer stem cells (CSCs) is, therefore, useful for improving PDT efficiency and preventing tumor recurrence and metastasis.

Carbonaceous Nanoparticle Air Pollution: Toxicity and Detection in Biological Samples

Among the different air pollutants, particulate matter (PM) is of great concern due to its abundant presence in the atmosphere, which results in adverse effects on the environment and human health. The different components of PM can be classified based on their physicochemical properties. Carbonaceous particles (CPs) constitute a major fraction of ultrafine PM and have the most harmful effects. Herein, we present a detailed overview of the main components of CPs, e.g., carbon black (CB), black carbon (BC), and brown carbon (BrC), from natural and anthropogenic sources. The emission sources and the adverse effects of CPs on the environment and human health are discussed. Particularly, we provide a detailed overview of the reported toxic effects of CPs in the human body, such as respiratory effects, cardiovascular effects, neurodegenerative effects, carcinogenic effects, etc. In addition, we also discuss the challenges faced by and limitations of the available analytical techniques for the qualitative and quantitative detection of CPs in atmospheric and biological samples. Considering the heterogeneous nature of CPs and biological samples, a detailed overview of different analytical techniques for the detection of CPs in (real-exposure) biological samples is also provided. This review provides useful insights into the classification, toxicity, and detection of CPs in biological samples.

Carbon nanomaterials for the detection of pesticide residues in food: A review

In agricultural fields, pesticides are widely used, but their residual presence in the environment poses a threat to humans, animals, insects, and ecosystems. The overuse of pesticides for pest control, enhancement of crop yield, etc. leaves behind a significant residual amount in the environment. Various robust, reliable, and reusable methods using a wide class of composites have been developed for the monitoring and controlling of pesticides. Researchers have discovered that carbon nanomaterials have a wide range of characteristics such as high porosity, conductivity and easy electron transfer that can be successfully used to detect pesticide residues from food. This review emphasizes the role of carbon nanomaterials in the field of pesticide residue analysis in different food matrices. The carbon nanomaterials including carbon nanotubes, carbon dots, carbon nanofibers, graphene/graphene oxides, and activated carbon fibres are discussed in the review. In addition, the review examines future prospects in this research area to help improve detection techniques for pesticides analysis.

Carbon nanostructures: a comprehensive review of potential applications and toxic effects

There is no doubt that nanotechnology has revolutionized our life since the 1970s when it was first introduced. Nanomaterials have helped us to improve the current products and services we use. Among the different types of nanomaterials, the application of carbon-based nanomaterials in every aspect of our lives has rapidly grown over recent decades. This review discusses recent advances of those applications in distinct categories, including medical, industrial, and environmental applications. The first main section introduces nanomaterials, especially carbon-based nanomaterials. In the first section, we discussed medical applications, including medical biosensors, drug and gene delivery, cell and tissue labeling and imaging, tissue engineering, and the fight against bacterial and fungal infections. The next section discusses industrial applications, including agriculture, plastic, electronic, energy, and food industries. In addition, the environmental applications, including detection of air and water pollutions and removal of environmental pollutants, were vastly reviewed in the last section. In the conclusion section, we discussed challenges and future perspectives.

Validation of a Standard Luminescence Method for the Fast Determination of the Antimicrobial Activity of Nanoparticles in Escherichia coli

The use of nanoparticles in multiple industries has raised concerned voices about the assessment of their toxicity/antimicrobial activity and the development of standardized handling protocols. Issues emerge during the antimicrobial assaying of multiple cargo, colorimetric, colloidal nanoformulations, as standard protocols often rely on visual evaluations, or optical density (OD) measurements, leading to high variance inhibitory concentrations (MIC). Thus, a fast, luminescence-based assay for the effective assessment of the antimicrobial activity of nanoparticles is herein reported, using the bioluminescence of an in-house E. coli ATCC® 8739TM construct with the pMV306G13 + Lux plasmid (E. coli Lux). The new strain's sensitivity to ofloxacin as a standard antibiotic was confirmed, and the methodology robustness verified against multiple nanoparticles and colorimetric drugs. The reduction of incubation from 24 to only 8 h, and the sole use of luminescence (LUX490) to accurately determine and distinguish MIC50 and MIC90, are two main advantages of the method. By discarding OD measurements, one can avoid turbidity and color interferences when calculating bacterial growth. This approach is an important tool that contributes to the standardization of methods, reducing samples' background interference and focusing on luminescence as a direct probe for bacterial metabolic activity, growth and, most importantly, the correct assessment of nanomaterials' antimicrobial activity.

Modes of adhesion of spherocylindrical nanoparticles to tensionless lipid bilayers

The adhesion modes and endocytosis pathway of spherocylindrical nanoparticles (NPs) are investigated numerically using molecular dynamics simulations of a coarse-grained implicit-solvent model. The investigation is performed systematically with respect to the adhesion energy density ξ, NP's diameter D, and NP's aspect ratio α. At weak ξ, the NP adheres to the membrane through a parallel mode, i.e., its principal axis is parallel to the membrane. However, for relatively large ξ, the NP adheres through a perpendicular mode, i.e., the NP is invaginated, such as its principal axis is nearly perpendicular to the membrane. The value of ξ at the transition from the parallel to the perpendicular mode decreases with increasing the D or α, in agreement with theoretical arguments based on the Helfrich Hamiltonian. As ξ is further increased, the NP undergoes endocytosis, with the value of ξ at the endocytosis threshold that is independent of the aspect ratio but decreases with increasing D. The kinetics of endocytosis depends strongly on ξ and D. While for low values of D, the NP first rotates to a parallel orientation then to a perpendicular orientation. At high values of ξ or D, the NP is endocytosed while in the parallel orientation.

Systematic and mechanistic analysis of AuNP-induced nanotoxicity for risk assessment of nanomedicine

For decades, nanoparticles (NPs) have been widely implemented in various biomedical fields due to their unique optical, thermal, and tunable properties. Particularly, gold nanoparticles (AuNPs) have opened new frontiers in sensing, targeted drug delivery, imaging, and photodynamic therapy, showing promising results for the treatment of various intractable diseases that affect quality of life and longevity. Despite the tremendous achievements of AuNPs-based approaches in biomedical applications, few AuNP-based nanomedicines have been evaluated in clinical trials, which is likely due to a shortage of understanding of the biological and pathological effects of AuNPs. The biological fate of AuNPs is tightly related to a variety of physicochemical parameters including size, shape, chemical structure of ligands, charge, and protein corona, and therefore evaluating the effects of these parameters on specific biological interactions is a major ongoing challenge. Therefore, this review focuses on ongoing nanotoxicology studies that aim to characterize the effect of various AuNP characteristics on AuNP-induced toxicity. Specifically, we focus on understanding how each parameter alters the specific biological interactions of AuNPs via mechanistic analysis of nano-bio interactions. We also discuss different cellular functions affected by AuNP treatment (e.g., cell motility, ROS generation, interaction with DNA, and immune response) to understand their potential human health risks. The information discussed herein could contribute to the safe usage of nanomedicine by providing a basis for appropriate risk assessment and for the development of nano-QSAR models.

Specific Tumor Cell Detection by a Metabolically Targeted Aggregation-Induced Emission-Based Gold Nanoprobe

Detection of circulating tumor cells (CTCs) could be widely used for early diagnosis and real-time monitoring of tumor progression in liquid biopsy samples. Compared with normal cells, tumor cells exhibit relatively strong negative surface charges due to the high rate of glycolysis. In this study, a cationic fluorescence "turn-on" aggregation-induced emission (AIE) nanoprobe based on gold nanorods (GNRs) was designed and tested to detect tumor cells specifically. In brief, tetraphenylethene (TPE), an AIE dye, was conjugated to the cationic polymer polyethylenimine (PEI) yielding TPEI. TPEI-PEG-SH was obtained by further functionalizing TPEI with a thiol group. TPEI-PEG-SH was grafted to the surface of GNRs, yielding the cationic AIE nanoprobe, named as GNRs-PEG-TPEI. The nanoprobe was characterized to have a uniform particle size of 172 nm, a strong positive surface charge (+54.87 mV), and a surface modification load of ∼40%. The in vitro stability of GNRs-PEG-TPEI was verified. The cellular imaging results demonstrated that the nanoprobe could efficiently recognize several types of tumor cells including MCF-7, HepG2, and Caco-2 while exhibiting specific fluorescence signals only after interacting with tumor cells and minimal background interference. In addition, the study investigated the toxicity of the nanoprobe to the captured cells and proved the safety of the nanoprobe. In conclusion, a specific and efficient nanoprobe was developed for capture and detection of different types of tumor cells based on their unique metabolic characteristics. It holds great promise for achieving early diagnosis and monitoring the tumor progression by detecting the CTCs in clinical liquid biopsy samples.

Developing a Solution for Nasal and Olfactory Transport of Nanomaterials

With advances in nanotechnology, engineered nanomaterial applications are a rapidly growing sector of the economy. Some nanomaterials can reach the brain through nose-to-brain transport. This transport creates concern for potential neurotoxicity of insoluble nanomaterials and a need for toxicity screening tests that detect nose-to-brain transport. Such tests can involve intranasal instillation of aqueous suspensions of nanomaterials in dispersion media that limit particle agglomeration. Unfortunately, protein and some elements in existing dispersion media are suboptimal for potential nose-to-brain transport of nanomaterials because olfactory transport has size- and ion-composition requirements. Therefore, we designed a protein-free dispersion media containing phospholipids and amino acids in an isotonic balanced electrolyte solution, a solution for nasal and olfactory transport (SNOT). SNOT disperses hexagonal boron nitride nanomaterials with a peak particle diameter below 100 nm. In addition, multiwalled carbon nanotubes (MWCNTs) in an established dispersion medium, when diluted with SNOT, maintain dispersion with reduced albumin concentration. Using stereomicroscopy and microscopic examination of plastic sections, dextran dyes dispersed in SNOT are demonstrated in the neuroepithelium of the nose and olfactory bulb of B6;129P2-Omp^tm3Mom/MomJ mice after intranasal instillation in SNOT. These findings support the potential for SNOT to disperse nanomaterials in a manner permitting nose-to-brain transport for neurotoxicity studies.

Immune responses, DNA damage and ultrastructural alterations of gills in the marine mussel Lithophaga lithophaga exposed to CuO nanoparticles

Nanoparticle (NP) pollution is a worldwide problem. Copper oxide nanoparticles (CuO NPs) are one of the most used NPs in a variety of applications, which results in their increased release into the marine environment. In the present work, the marine mussel Lithophaga lithophaga was used as a model organism to evaluate the toxic effects of CuO NPs following 28 days of exposure to sub-lethal concentrations (5 and 20 μg/L). The time points were 1 day of exposure to assess the cell viability, phagocytosis in mussel haemocytes and genotoxicity (DNA damage in gills), 1, 14 and 28 days of exposure to evaluate copper concentrations in water and gills, as well as metallothionein concentration in gills, while gill histology and SEM examination were done after 28 days of exposure. The results indicated that the accumulation of CuO NPs in gills increased with concentration and time. Mussel exposure to CuO NPs increased neutral red uptake. However, the phagocytic abilities decreased in haemocytes with increased concentration. CuO NPs caused DNA damage in the gills even at low concentrations (5 µg/L). CuO NPs caused histopathological alterations in gills, such as brown cell accumulation, necrosis, dwarfism of filaments and ciliary erosion. In conclusion, exposure of the mussel L. lithophaga to CuO NPs led to concentration- and time-dependent responses for all the examined biomarkers. Thus, L. lithophaga may be used as a bioindicator organism in the assessment of CuO NP toxicity.

In Situ Detection of Nanotoxicity in Living Cells Based on Multiple miRNAs Probed by a Peptide Functionalized Nanoprobe

The potential toxicity of nanoparticles, especially for clinically applicable ones, has become a critical concern. Technologies that can in situ-evaluate the toxicity of nanoparticles with high sensitivity are urgently needed. In this study, a facile strategy was developed for sensitive detection on the nanotoxicity of nanoparticles with low toxicity or a low dose. A functional nanoprobe loaded with molecular beacons was constructed to realize in situ evaluation of the nanotoxicity through probing multiple miRNAs in nanoparticle-exposed living cells. Being composed of protamine complexed with molecular beacons for miRNA detection and decorated by TAT and KALA peptides, the dual-peptide functionalized nanoprobe can efficiently deliver molecular beacons into living cells to realize the real-time monitoring of early biomarkers (miR-21 and miR-221) to evaluate nanotoxicity. Using mesoporous silica nanoparticles (MSNs) with different surface modifications as typical representatives of low toxic nanoparticles, we demonstrate that our nanoprobe can sensitively detect miRNA changes in cells under diverse exposure conditions, that is, MSN-NH₂ exhibits the strongest capability to upregulate miR-21 and miR-221, and the upregulation is exposure dose- and time-dependent. Our approach is much more sensitive as compared with conventional methods to study cytotoxicity such as 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, cell morphology observation, and reactive oxygen species (ROS) assay. This study paves a path for effective and facile nanotoxicity evaluation and provides insights into the biological impacts of MSNs.

Tuning the Spin-Crossover Behaviour in Fe(II) Polymeric Composites for Food Packaging Applications

Although the spin-crossover (SCO) phenomenon is well documented, tuning the SCO behaviour remains a challenging task. This could be mainly attributed to the ‘delicate’ nature of the phenomenon; cooperativity expressed through differences in particle size and morphologies, and electrostatic interactions could significantly affect the process. The goal of the present effort is dual bearing both scientific and technological interest. Firstly, to examine the technological potential of SCO complexes by incorporating them into polymers, and secondly—and most importantly—to investigate if polymer-SCO complex interactions could occur and could affect the SCO behaviour, depending on the structural properties of both the polymer matrix and the SCO complex. In this context, two different polymers, polylactic acid (PLA) and polysulphone (PSF), which are capable of developing different interactions with the inclusions, and the SCO complexes [Fe(abpt)2{N(CN)2}2] and [Fe(abpt)2(SCN)2] were examined; abpt is the N,N’-bidentate chelating ligand 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole. The composites were characterised through scanning electron microscopy (SEM), attenuated total reflectance infrared (ATR/FTIR), and Raman spectroscopy. In addition, the potential migration release of the SCO compounds from the polymeric matrices and their toxicity evaluation were also studied. In addition, the potential migration release of the SCO compounds from the polymeric matrices was evaluated, and their insignificant toxicity was also verified. Temperature-dependent Raman spectra were collected in situ for the monitoring of the SCO behaviour after the incorporation of the Fe(II) complexes into the polymers; an upshift of the T1/2 transition and a hysteretic behaviour was detected for PSF-SCO composites, compared with the non-hysteretic behaviour of the pristine SCO complexes.

Investigating the in vitro photothermal effect of green synthesized apigenin-coated gold nanoparticle on colorectal carcinoma

Applying toxic chemical to the synthesis of stable gold nanoparticles is one of the limitations of gold nanoparticles for therapeutic applications such as photothermal therapy. Plant compounds such as apigenin (API) with therapeutic potential can be applied in the synthesis of gold nanoparticles. API‐coated gold nanoparticles (Api@AuNPs) with an average size of 19.1 nm and a surface charge of −4.3 mV have been synthesized by a simple and efficient technique. The stability of Api@AuNPs in the biological environment was verified through UV‐Vis spectroscopy. Based on Raman and FTIR spectroscopy analysis, chemical binding of API on the surface of Api@AuNPs through hydroxyl and carbonyl functional groups was found to be the main reason for the stability of the Api@AuNPs in comparison with citrate‐coated gold nanoparticles (Cit@AuNPs). The synthesized Api@AuNPs do not cause major toxic effects up to 128 ppm. Api@AuNP‐mediated photothermal therapy leads to the indiscriminate eradication of almost half of both mouse fibroblastic (L929) and colorectal cancer (CT26) cells. Flow‐cytometry analysis revealed that the cell death mechanism is mainly apoptosis. In the apoptosis triggered cell death in photothermal treatment, Api@AuNPs are preferred over commonly used gold nanoparticles in photothermal treatments which mostly trigger the necrosis cell death pathway.

Safety Evaluation of Nanotechnology Products

Nanomaterials are now being used in a wide variety of biomedical applications. Medical and health-related issues, however, have raised major concerns, in view of the potential risks of these materials against tissue, cells, and/or organs and these are still poorly understood. These particles are able to interact with the body in countless ways, and they can cause unexpected and hazardous toxicities, especially at cellular levels. Therefore, undertaking in vitro and in vivo experiments is vital to establish their toxicity with natural tissues. In this review, we discuss the underlying mechanisms of nanotoxicity and provide an overview on in vitro characterizations and cytotoxicity assays, as well as in vivo studies that emphasize blood circulation and the in vivo fate of nanomaterials. Our focus is on understanding the role that the physicochemical properties of nanomaterials play in determining their toxicity.

Design and Development of Antibody Functionalized Gold Nanoparticles for Biomedical Applications

Antibody-functionalized gold nanoparticle constitutes a powerful interface biosystem for biomedical applications where the properties of gold nanoparticles and the specificity of antibody-antigen interactions are combined. This study provides insight into the key factors for the development of antibody functionalized gold nanoparticles focusing on the immobilization of the antibody. Here, we address an oriented antibody immobilization procedure on gold nanoparticles. It comprises chelatemodified gold nanoparticles that are designed for oriented immobilization of IgG antibodies (end on spatial orientation) through the metal-chelation to histidine-rich metal binding site in the heavy chain (Fc) of the antibody.

The pharmacology of plant virus nanoparticles

The application of nanoparticles for medical purposes has made enormous strides in providing new solutions to health problems. The observation that plant virus-based nanoparticles (VNPs) can be repurposed and engineered as smart bio-vehicles for targeted drug delivery and imaging has launched extensive research for improving the therapeutic and diagnostic management of various diseases. There is evidence that VNPs are promising high value nanocarriers with potential for translational development. This is mainly due to their unique features, encompassing structural uniformity, ease of manufacture and functionalization by means of expression, chemical biology and self-assembly. While the development pipeline is moving rapidly, with many reports focusing on engineering and manufacturing aspects to tailor the properties and efficacy of VNPs, fewer studies have focused on gaining insights into the nanotoxicity of this novel platform nanotechnology. Herein, we discuss the pharmacology of VNPs as a function of formulation and route of administration. VNPs are reviewed in the context of their application as therapeutic adjuvants or nanocarrier excipients to initiate, enhance, attenuate or impede the formulation's toxicity. The summary of the data however also underlines the need for meticulous VNP structure-nanotoxicity studies to improve our understanding of their in vivo fates and pharmacological profiles to pave the way for translation of VNP-based formulations into the clinical setting.

3D Tumor Spheroid Models for In Vitro Therapeutic Screening of Nanoparticles

The anticancer activity of compounds and nanoparticles is most often determined in the cell monolayer. However, three-dimensional (3D) systems, such as tumor spheroids, are more representing the natural tumor microenvironment. They have been shown to have higher invasiveness and resistance to cytotoxic agents and radiotherapy compared to cells growing in 2D monolayer. Furthermore, to improve the prediction of clinical efficacy of drugs, in the past decades, even more sophisticated systems, such as multicellular 3D cultures, closely representing natural tumor microenvironment have been developed. Those cultures are formed from either cell lines or patient-derived tumor cells. Such models are very attractive and could improve the selection of tested materials for clinical trials avoiding unnecessary expensive tests in vivo. The microenvironment in tumor spheroids is different, and those differences or the interaction between several cell populations may contribute to different tumor response to the treatment. Also, different types of nanoparticles may have different behavior in 3D models, depending on their nature, physicochemical properties, the presence of targeting ligands on the surface, etc. Therefore, it is very important to understand in which cases which type of tumor spheroid is more suitable for testing specific types of nanoparticles, which conditions should be used, and which analytical method should be applied.

Self-Nano-Emulsifying Drug-Delivery Systems: From the Development to the Current Applications and Challenges in Oral Drug Delivery

Approximately one third of newly discovered drug molecules show insufficient water solubility and therefore low oral bio-availability. Self-nano-emulsifying drug-delivery systems (SNEDDSs) are one of the emerging strategies developed to tackle the issues associated with their oral delivery. SNEDDSs are composed of an oil phase, surfactant, and cosurfactant or cosolvent. SNEDDSs characteristics, their ability to dissolve a drug, and in vivo considerations are determinant factors in the choice of SNEDDSs excipients. A SNEDDS formulation can be optimized through phase diagram approach or statistical design of experiments. The characterization of SNEDDSs includes multiple orthogonal methods required to fully control SNEDDS manufacture, stability, and biological fate. Encapsulating a drug in SNEDDSs can lead to increased solubilization, stability in the gastro-intestinal tract, and absorption, resulting in enhanced bio-availability. The transformation of liquid SNEDDSs into solid dosage forms has been shown to increase the stability and patient compliance. Supersaturated, mucus-permeating, and targeted SNEDDSs can be developed to increase efficacy and patient compliance. Self-emulsification approach has been successful in oral drug delivery. The present review gives an insight of SNEDDSs for the oral administration of both lipophilic and hydrophilic compounds from the experimental bench to marketed products.

The Chorioallantoic Membrane Assay in Nanotoxicological Research-An Alternative for In Vivo Experimentation

Nanomaterials unveil many applicational possibilities for technical and medical purposes, which range from imaging techniques to the use as drug carriers. Prior to any human application, analysis of undesired effects and characterization of their toxicological profile is mandatory. To address this topic, animal models, and rodent models in particular, are most frequently used. However, as the reproducibility and transferability to the human organism of animal experimental data is increasingly questioned and the awareness of animal welfare in society increases at the same time, methodological alternatives are urgently required. The chorioallantoic membrane (CAM) assay is an increasingly popular in ovo experimental organism suitable for replacement of rodent experimentation. In this review, we outline several application fields for the CAM assay in the field of nanotoxicology. Furthermore, analytical methods applicable with this model were evaluated in detail. We further discuss ethical, financial, and bureaucratic aspects and benchmark the assay with other established in vivo models such as rodents.

Effects of Dextran-Coated Superparamagnetic Iron Oxide Nanoparticles on Mouse Embryo Development, Antioxidant Enzymes and Apoptosis Genes Expression, and Ultrastructure of Sperm, Oocytes and Granulosa Cells

Background

Although application of superparamagnetic iron oxide nanoparticles (SPIONs) in industry and medicine has increased, their potential toxicity in reproductive cells remains a controversial issue. This study was undertaken to address the response of sperm, oocyte, and resultant blastocyst to dextran-coated SPIONs (D-SPIONs) treatment during murine in vitro fertilization (IVF).

Materials and Methods

In this experimental study, murine mature oocytes were randomly divided into three groups: control, and low- and high-dose groups in which fertilization medium was mixed with 0, 50 and 250 μg/ml of DSPIONs, respectively. Sperm and/or cumulus oocyte complexes (COCs) were cultured for 4 h in this medium for electron microscopic analysis of sperm and COCs, and assessment of developmental competence and genes expression of Gpx1, Sod1, catalase, Bcl2l1 and Bax in the resultant blastocysts.

Results

Ultrastructural study of sperm, oocyte, and granulosa showed destructed mitochondria and membranes in spermatozoa, vacuolated mitochondria and distorted cristae in oocytes, and disrupted nuclei and disorganized cell membranes in granulosa in a dose-dependent manner. Data showed that cleavage and blastocyst rates in the 250 μg/ml of D-SPIONs were significantly lower than in the control group (P<0.05). Gene expression of GPx1, Sod1, catalase, Bcl2l1 and Bax in resultant blastocysts of the high-dose group and catalase and Bax in resultant blastocysts of the low-dose group, was higher than the controls.

Conclusion

There is considerable concern regarding D-SPIONs toxic effects on IVF, and mitochondrial and cell membrane damage in mouse spermatozoa and oocytes, which may be related to oxidative stress and apoptotic events.

Toxicity assessment and comparison of the land snail's Cornu aspersum responses against CuO nanoparticles and ZnO nanoparticles

The goal of the present study was to examine the effects of ZnO NPs and CuO NPs on Cornu aspersum land snail, enlightening their cytotoxic profile. ZnO NPs and CuO NPs were synthesized and thoroughly characterized. Α series of concentrations of either ZnO NPs or CuO NPs were administered in the feed of snails for 20 days. Thereafter, neutral red retention assay was conducted, in order to estimate NRRT50 values. Subsequently, snails were fed with NPs concentrations slightly lower than the concentrations that were corresponding to the NRRT50 values, i.e. 3 mg·L^-1 ZnO NPs and 6 mg·L^-1 CuO NPs, for 1, 5, 10 and 20 days. Both NPs agglomerates were detected in hemocytes by Transmission Electron Microscopy. Moreover, both effectors resulted to toxicity in the snails' hemocytes. The latter was shown by changes in the NRRT50 values, increased reactive oxygen species (ROS) production, lipid peroxidation, DNA integrity loss, protein carbonyl content, ubiquitin conjugates and cleaved caspases conjugates levels compared to the untreated animals. Although ZnO NPs exhibited higher toxicity, as indicated by the NRRT50 values, both NPs affected similarly a wide range of the cellular parameters mentioned above. The latter parameters could constitute sensitive biomarkers in biomonitoring studies of terrestrial environment against nanoparticles.

Fluorescence-Based and Fluorescent Label-Free Characterization of Polymer Nanoparticle Decorated T Cells

Cells are attractive carriers for the transport and delivery of nanoparticulate cargo. The use of cell-based carriers allows one to enhance control over the biodistribution of drug-loaded polymers and polymer nanoparticles. One key element in the development of cell-based delivery systems is the loading of the cell-based carrier with the nanoparticle cargo, which can be achieved either by internalization of the payload or by immobilization on the cell surface. The surface modification of cells with nanoparticles or the internalization of nanoparticles by cells is usually monitored with fluorescence-based techniques, such as flow cytometry and confocal microscopy. In spite of the widespread use of these techniques, the use of fluorescent labels also poses some risks and has several drawbacks. Fluorescent dyes may bleach, or leach from, the nanoparticles or alter the physicochemical properties of nanoparticles and their interactions with and uptake by cells. Using poly(d,l-lactic acid) nanoparticles that are loaded with Coumarin 6, BODIPY 493/503, or DiO dyes as a model system, this paper demonstrates that the use of physically entrapped fluorescent labels can lead to false negative or erroneous results. The use of nanoparticles that contain covalently tethered fluorescent dyes instead was found to provide a robust approach to monitor cell surface conjugation reactions and to quantitatively analyze nanoparticle-decorated cells. Finally, it is shown that optical diffraction tomography is an attractive, alternative technique for the characterization of nanoparticle-decorated cells, which obviates the need for fluorescent labels.

Retrospective Quantitative Genetic Analysis and Genomic Prediction of Global Wheat Yields

Breeding for grain yield (GY) in bread wheat at the International Maize and Wheat Improvement Center (CIMMYT) involves three-stage testing at Obregon, Mexico in different selection environments (SEs). To understand the efficiency of selection in the SEs, we performed a large retrospective quantitative genetics study using CIMMYT's yield trials evaluated in the SEs (2013-2014 to 2017-2018), the South Asia Bread Wheat Genomic Prediction Yield Trials (SABWGPYTs) evaluated in India, Pakistan, and Bangladesh (2014-2015 to 2017-2018), and the Elite Spring Wheat Yield Trials (ESWYTs) evaluated in several sites globally (2003-2004 to 2016-2017). First, we compared the narrow-sense heritabilities in the Obregon SEs and target sites and observed that the mean heritability in the SEs was 44.2 and 92.3% higher than the mean heritabilities in the SABWGPYT and ESWYT sites, respectively. Second, we observed significant genetic correlations between a SE in Obregon and all the five SABWGPYT sites and 65.1% of the ESWYT sites. Third, we observed high ratios of response to indirect selection in the SEs of Obregon with a mean of 0.80 ± 0.21 and 2.6 ± 5.4 in the SABWGPYT and ESWYT sites, respectively. Furthermore, our results also indicated that for all the SABWGPYT sites and 82% of the ESWYT sites, a response greater than 0.5 can be achieved by indirect selection for GY in Obregon. We also performed genomic prediction for GY in the target sites using the performance of the same lines in the SEs of Obregon and observed moderate mean prediction accuracies of 0.24 ± 0.08 and 0.28 ± 0.08 in the SABWGPYT and ESWYT sites, respectively using the genotype x environment (GxE) model. However, we observed similar accuracies using the baseline model with environment and line effects and no advantage of modeling GxE interactions. Overall, this study provides important insights into the suitability of the Obregon SEs in breeding for GY, while the variable genomic predictabilities of GY and the high year-to-year GY fluctuations reported, highlight the importance of multi-environment testing across time and space to stave off GxE induced uncertainties in varietal yields.

Multifunctional Gold Nanoparticles: A Novel Nanomaterial for Various Medical Applications and Biological Activities

Nanotechnology has become a trending area in science and has made great advances with the development of functional, engineered nanoparticles. Various metal nanoparticles have been widely exploited for a wide range of medical applications. Among them, gold nanoparticles (AuNPs) are widely reported to guide an impressive resurgence and are highly remarkable. AuNPs, with their multiple, unique functional properties, and easy of synthesis, have attracted extensive attention. Their intrinsic features (optics, electronics, and physicochemical characteristics) can be altered by changing the characterization of the nanoparticles, such as shape, size and aspect ratio. They can be applied to a wide range of medical applications, including drug and gene delivery, photothermal therapy (PTT), photodynamic therapy (PDT) and radiation therapy (RT), diagnosis, X-ray imaging, computed tomography (CT) and other biological activities. However, to the best of our knowledge, there is no comprehensive review that summarized the applications of AuNPs in the medical field. Therefore, in this article we systematically review the methods of synthesis, the modification and characterization techniques of AuNPs, medical applications, and some biological activities of AuNPs, to provide a reference for future studies.

Interference: A Much-Neglected Aspect in High-Throughput Screening of Nanoparticles

Despite several studies addressing nanoparticle (NP) interference with conventional toxicity assay systems, it appears that researchers still rely heavily on these assays, particularly for high-throughput screening (HTS) applications in order to generate "big" data for predictive toxicity approaches. Moreover, researchers often overlook investigating the different types of interference mechanisms as the type is evidently dependent on the type of assay system implemented. The approaches implemented in the literature appear to be not adequate as it often addresses only one type of interference mechanism with the exclusion of others. For example, interference of NPs that have entered cells would require intracellular assessment of their interference with fluorescent dyes, which has so far been neglected. The present study investigated the mechanisms of interference of gold NPs and silver NPs in assay systems implemented in HTS including optical interference as well as adsorption or catalysis. The conventional assays selected cover all optical read-out systems, that is, absorbance (XTT toxicity assay), fluorescence (CytoTox-ONE Homogeneous membrane integrity assay), and luminescence (CellTiter Glo luminescent assay). Furthermore, this study demonstrated NP quenching of fluorescent dyes also used in HTS (2',7'-dichlorofluorescein, propidium iodide, and 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethyl-benzamidazolocarbocyanin iodide). To conclude, NP interference is, as such, not a novel concept, however, ignoring this aspect in HTS may jeopardize attempts in predictive toxicology. It should be mandatory to report the assessment of all mechanisms of interference within HTS, as well as to confirm results with label-free methodologies to ensure reliable big data generation for predictive toxicology.

Probing Nanoparticle-Cell Interaction Using Micro-Raman Spectroscopy: Silver and Gold Nanoparticle-Induced Stress Effects on Optically Trapped Live Red Blood Cells

Advancements in the field of nanotechnology have resulted in the emergence of a large variety of engineered nanomaterials for innumerable applications. Despite the ubiquitous use of nanomaterials in daily life, concerns regarding the potential toxicity and safety of these materials have also been raised. There is a high demand for assessing the unwanted effects of both gold and silver nanoparticles, which is increasingly being used in biomedical applications. This paper deals with the study of stress due to silver and gold nanoparticles of varying size on red blood cells (RBCs) using Raman tweezers spectroscopy. RBCs were incubated with nanoparticles of size in the 10-100 nm range with the same concentrations, and micro-Raman spectra were recorded by optically trapping the nanoparticle-treated live RBCs. Spectral modifications implicating hemoglobin deoxygenation were observed in all nanoparticle-treated RBCs. One of the probable reason for the deoxygenation trend can be the adhesion of nanoparticles onto the cell surface causing imbalance in cell functioning. Moreover, the higher spectral variations observed for silver nanoparticles indicate that oxidative stress is involved in cell damage. These mechanisms lead to the modification in the hemoglobin structure because of changes in the pH of cytoplasm, which can be detected using Raman spectroscopy.

Toxicity and safety study of silver and gold nanoparticles functionalized with cysteine and glutathione

This study was designed to evaluate the nano-bio interactions between endogenous biothiols (cysteine and glutathione) with biomedically relevant, metallic nanoparticles (silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs)), in order to assess the biocompatibility and fate of nanoparticles in biological systems. A systematic and comprehensive analysis revealed that the preparation of AgNPs and AuNPs in the presence of biothiols leads to nanoparticles stabilized with oxidized forms of biothiols. Their safety was tested by evaluation of cell viability, reactive oxygen species (ROS) production, apoptosis induction and DNA damage in murine fibroblast cells (L929), while ecotoxicity was tested using the aquatic model organism Daphnia magna. The toxicity of these nanoparticles was considerably lower compared to their ionic metal forms (i.e., Ag+ and Au3+). The comparison with data published on polymer-coated nanoparticles evidenced that surface modification with biothiols made them safer for the biological environment. In vitro evaluation on human cells demonstrated that the toxicity of AgNPs and AuNPs prepared in the presence of cysteine was similar to the polymer-based nanoparticles with the same core material, while the use of glutathione for nanoparticle stabilization was considerably less toxic. These results represent a significant contribution to understanding the role of biothiols on the fate and behavior of metal-based nanomaterials.

Multifunctionality of gold nanoparticles: Plausible and convincing properties

In a couple of decades, nanotechnology has become a trending area in science due to it covers all subject that combines diverse range of fields including but not limited to chemistry, physics and medicine. Various metal and metal oxide nanomaterials have been developed for wide range applications. However, the application of gold nanostructures and nanoparticles has been received more attention in various biomedical applications. The unique property of gold nanoparticles (AuNPs) is surface plasmon resonance (SPR) that determine the size, shape and stability. The wide surface area of AuNPs eases the proteins, peptides, oligonucleotides, and many other compounds to tether and enhance the biological activity of AuNPs. AuNPs have multifunctionality including antimicrobial, anticancer, drug and gene delivery, sensing applications and imaging. This state-of-the-art review is focused on the role of unique properties of AuNPs in multifunctionality and its various applications.

In vivo clearable inorganic nanophotonic materials: designs, materials and applications

Inorganic nanophotonic materials (INPMs) are considered to be promising diagnosis and therapeutic agents for in vivo applications, such as bio-imaging, photoacoustic imaging and photothermal therapy. However, some concerns remain regarding these materials, such as undesirable long-term in vivo accumulation and associated toxicity. The inability to be degraded or cleared has decreased their likelihood to be used for potential clinical translations. To this end, new strategies have recently emerged to develop systematically clearable INPMs. Thus, this review provides an overview of these strategies used to expedite the clearance of INPMs, as well as the relevant design and functionalized modifications which are available to engineer the above materials. Along with their important applications in the fields of in vivo diagnoses and therapies, the challenges and outlook for in vivo clearable INPMs are also discussed. This attempt to explore in vivo clearable INPMs to inhibit their accumulation toxicity may represent the solution to a ubiquitous physiological issue, thus paving a new avenue for the development of novel optical nanomaterials for biophotonic applications.

Toxicopathological and immunological studies on different concentrations of chitosan-coated silver nanoparticles in rats

Background

Much consideration has been paid to the toxicological assessment of nanoparticles prior to clinical and biological applications. While in vitro studies have been expanding continually, in vivo investigations of nanoparticles have not developed a cohesive structure. This study aimed to assess the acute toxicity of different concentrations of chitosan-coated silver nanoparticles (Ch-AgNPs) in main organs, including liver, kidneys, and spleen.

Materials and methods

Twenty-eight male albino rats were used and divided into 4 groups (n=7). Group 1 was kept as a negative control group. Groups 2, 3, and 4 were treated intraperitoneally with Ch-AgNPs each day for 14 days at doses of 50, 25, and 10 mg/kg body weight (bwt) respectively. Histopathological, morphometric and immunohistochemical studies were performed as well as oxidative stress evaluations, and specific functional examinations for each organ were elucidated.

Results

It was revealed that Ch-AgNPs induced dose-dependent toxicity, and the repeated dosing of rats with 50 mg/kg Ch-AgNPs induced severe toxicities. Histopathological examination showed congestion, hemorrhage, cellular degeneration, apoptosis and necrosis in hepatic and renal tissue as well as lymphocytic depletion with increasing tangible macrophages in the spleen. The highest levels of malondialdehyde, alanine aminotransferase, aspartate aminotransferase (MDA, ALT, AST) and the lowest levels of reduced glutathione, immunoglobulin G, M and total protein (GSH, IgG, IgM, TP) were observed in this group. On the other hand, repeated dosing with 25 mg/kg induced mild to moderate disturbance in the previous parameters, while there was no significant difference in results of pathological examination and biochemical tests between the control group and those treated with 10 mg/kg bwt Ch-AgNPs.

Conclusion

Chitosan-coated silver nanoparticles induce dose-dependent adverse effects on rats.

Toxicity of carbon-based nanomaterials: Reviewing recent reports in medical and biological systems

Application of nanomaterials in our daily life is increasing, day in day out and concerns have raised about their toxicity for human and other organisms. In this manner, carbon-based nanomaterials have been applied to different products due to their unique physicochemical, electrical, mechanical properties, and biological compatibility. But, there are several reports about the negative effects of these materials on biological systems and cellular compartments. This review article describes the various types of carbon-based nanomaterials and methods that use for determining these toxic effects that are reported recently in the papers. Then, extensively discussed the toxic effects of these materials on the human and other living organisms and also their toxicity routs including Neurotoxicity, Hepatotoxicity, Nephrotoxicity, Immunotoxicity, Cardiotoxicity, Genotoxicity and epigenetic toxicity, Dermatotoxicity, and Carcinogenicity.

Engineered nanoparticle exposure and cardiovascular effects: the role of a neuronal-regulated pathway

Human and animal studies have confirmed that inhalation of particles from ambient air or occupational settings not only causes pathophysiological changes in the respiratory system, but causes cardiovascular effects as well. At an equal mass lung burden, nanoparticles are more potent in causing systemic microvascular dysfunction than fine particles of similar composition. Thus, accumulated evidence from animal studies has led to heightened concerns about the potential short- and long-term deleterious effects of inhalation of engineered nanoparticles on the cardiovascular system. This review highlights the new observations from animal studies, which document the adverse effects of pulmonary exposure to engineered nanoparticles on the cardiovascular system and elucidate the potential mechanisms involved in regulation of cardiovascular function, in particular, how the neuronal system plays a role and reacts to pulmonary nanoparticle exposure based on both in vivo and in vitro studies. In addition, this review also discusses the possible influence of altered autonomic nervous activity on preexisting cardiovascular conditions. Whether engineered nanoparticle exposure serves as a risk factor in the development of cardiovascular diseases warrants further investigation.

Monitoring the death of single BaF3 cells under plasmonic photothermal heating induced by ultrasmall gold nanorods

Morphological changes and trypan-blue staining are temporally tracked in single cells via optical microscopy after plasmonic photothermal heating.

Real-time local oxygen measurements for high resolution cellular imaging

Single-cell metabolic investigations are hampered by the absence of flexible tools to measure local partial pressure of O₂ (pO₂) at high spatial-temporal resolution. To this end, we developed an optical sensor capable of measuring local pericellular pO₂ for subcellular resolution measurements with confocal imaging while simultaneously carrying out electrophysiological and/or chemo-mechanical single cell experiments. Here we present the OxySplot optrode, a ratiometric fluorescent O₂-micro-sensor created by adsorbing O₂-sensitive and O₂-insensitive fluorophores onto micro-particles of silica. To protect the OxySplot optrode from the components and reactants of liquid environment without compromising access to O₂, the micro-particles are coated with an optically clear silicone polymer (PDMS, polydimethylsiloxane). The PDMS coated OxySplot micro-particles are used alone or in a thin (~50 μm) PDMS layer of arbitrary shape referred to as the OxyMat. Additional top coatings on the OxyMat (e.g., fibronectin, laminin, polylysine, special photoactivatable surfaces etc.) facilitate adherence of cells. The OxySplots report the cellular pO₂ and micro-gradients of pO₂ without disrupting the flow of extracellular solutions or interfering with patch-clamp pipettes, mechanical attachments, and micro-superfusion. Since OxySplots and a cell can be imaged and spatially resolved, calibrated changes of pO₂ and intracellular events can be imaged simultaneously. In addition, the response-time (t_0.5 = 0.7 s, 0-160 mmHg) of OxySplots is ~100 times faster than amperometric Clark-type polarization microelectrodes. Two usage example of OxySplots with cardiomyocytes show (1) OxySplots measuring pericellular pO₂ while tetramethylrhodamine methyl-ester (TMRM) was used to measure mitochondrial membrane potential (ΔΨ_m); and (2) OxySplots measuring pO₂ during ischemia and reperfusion while rhod-2 was used to measure cytosolic [Ca²⁺]_i levels simultaneously. The OxySplot/OxyMat optrode system provides an affordable and highly adaptable optical sensor system for monitoring pO₂ with a diverse array of imaging systems, including high-speed, high-resolution confocal microscopes while physiological features are measured simultaneously.

Gas-Generating Nanoplatforms: Material Chemistry, Multifunctionality, and Gas Therapy

The fast advances of theranostic nanomedicine enable the rational design and construction of diverse functional nanoplatforms for versatile biomedical applications, among which gas-generating nanoplatforms (GGNs) have emerged very recently as unique theranostic nanoplatforms for broad gas therapies. Here, the recent developments of the rational design and chemical construction of versatile GGNs for efficient gas therapies by either exogenous physical triggers or endogenous disease-environment responsiveness are reviewed. These gases involve some therapeutic gases that can directly change disease status, such as oxygen (O₂ ), nitric oxide (NO), carbon monoxide (CO), hydrogen (H₂ ), hydrogen sulfide (H₂ S) and sulfur dioxide (SO₂ ), and other gases such as carbon dioxide (CO₂ ), dl-menthol (DLM), and gaseous perfluorocarbon (PFC) for supplementary assistance of the theranostic process. Abundant nanocarriers have been adopted for gas delivery into lesions, including poly(d,l-lactic-co-glycolic acid), micelles, silica/mesoporous silica, organosilica, MnO₂ , graphene, Bi₂ Se₃ , upconversion nanoparticles, CaCO₃ , etc. Especially, these GGNs have been successfully developed for versatile biomedical applications, including diagnostic imaging and therapeutic use. The biosafety issue, challenges faced, and future developments on the rational construction of GGNs are also discussed for further promotion of their clinical translation to benefit patients.