Gold Nanomaterials: Preparation,Chemical Modification,Biomedical Applications and Potential Risk Assessment

Gold nanomaterials (Au NMs) have attracted increasing attention in biomedicine due to their facile preparation, multifunctional modifications, unique optical and electrical properties, and good biocompatibility. The physicochemical properties of Au NMs at nanoscale, like size, shape, surface chemistry, and near field effects, are rendering Au NMs potent candidates in biomedicine. Thus, risk assessment of negative effects of Au NMs on biological systems is becoming urgent and necessary for future applications. In this review, we summarize up-to-date progresses on the preparation and modification of Au NMs and their biomedical applications, including biosensor, bioimaging and phototherapy, gene/drug delivery. Finally, we discuss the potential risk of Au NMs to biological systems, which is instructive for rationally designing and preparing nanomaterials for safe applications in nanomedicine.     

Neuroinflammatory Markers: Key Indicators in the Pathology of Neurodegenerative Diseases

Neuroinflammation, a protective response of the central nervous system (CNS), is associated with the pathogenesis of neurodegenerative diseases. The CNS is composed of neurons and glial cells consisting of microglia, oligodendrocytes, and astrocytes. Entry of any foreign pathogen activates the glial cells (astrocytes and microglia) and overactivation of these cells triggers the release of various neuroinflammatory markers (NMs), such as the tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-1β (IL-10), nitric oxide (NO), and cyclooxygenase-2 (COX-2), among others. Various studies have shown the role of neuroinflammatory markers in the occurrence, diagnosis, and treatment of neurodegenerative diseases. These markers also trigger the formation of various other factors responsible for causing several neuronal diseases including Alzheimer’s disease (AD), Parkinson’s disease (PD), Huntington’s disease (HD), multiple sclerosis (MS), ischemia, and several others. This comprehensive review aims to reveal the mechanism of neuroinflammatory markers (NMs), which could cause different neurodegenerative disorders. Important NMs may represent pathophysiologic processes leading to the generation of neurodegenerative diseases. In addition, various molecular alterations related to neurodegenerative diseases are discussed. Identifying these NMs may assist in the early diagnosis and detection of therapeutic targets for treating various neurodegenerative diseases.     

Immobilized Nanomaterials for Environmental Applications

Nanomaterials (NMs) have been extensively used in several environmental applications; however, their widespread dissemination at full scale is hindered by difficulties keeping them active in engineered systems. Thus, several strategies to immobilize NMs for their environmental utilization have been established and are described in the present review, emphasizing their role in the production of renewable energies, the removal of priority pollutants, as well as greenhouse gases, from industrial streams, by both biological and physicochemical processes. The challenges to optimize the application of immobilized NMs and the relevant research topics to consider in future research are also presented to encourage the scientific community to respond to current needs.     

Novel approach for electrochemical preparation of sulfur nanoparticles

An electrochemical method is presented for the preparation of sulfur nanoparticles (S-NPs) from thiosulfate ion. The particle size of the S-NPs can be adjusted between 35 and 65 nm by varying parameters such as the initial concentration of thiosulfate. The solvent/non-solvent precipitation method was also applied to the preparation of S-NPs for comparison. In this case, the use of hot alcohol and cold water as solvent/non-solvent system along with 100 ml·min^?1 flow rate for co-mixing of non-solvent resulted in the formation of S-NPs in a typical size of 250 nm that are fairly homogeneous in shape and have a narrow particle size distribution. The results revealed that, in comparison to the precipitation process, the electro-synthetic method offers simplicity, higher efficiency, improved size control, and less environmental contamination.

Trends in nanomaterial-based solid-phase microextraction with a focus on environmental applications - A review

Effective solid-phase microextraction (SPME) in environmental field represents a crucial step for the adequate extraction of several analytes. Several materials have been traditionally developed for SPME of several analytes from environmental samples, even though their several restrictions such as post-treatment required, elevate costs and limited efficiency. Recently, nanomaterials (NMs) have emerged as a promising substitute for SPME in environmental applications of traditional techniques, due to their small size and their high specific surface-area which enhances their high reactivity. In this present review different NMs which have recently been utilized as SPME sorbent for environmental applications are classified into eleven main groups, namely nanoparticles, nanofibers, nanoflakes, nanocomposites, nanorods, nanotubes, nanohorns, nanosheets, nanocubes, nanospheres and polymer-based NMs. Application of these NMs in SPME modes and configurations for environmental analysis has been reviewed. The study discusses not only the advantages but also the major limitations of using such NMs.     

Trends in the sample preparation and analysis of nanomaterials as environmental contaminants

Much research on the use of nanomaterials in different applications is being conducted in areas such as water treatment, catalysis, oil processing, medicine, food, sensors, energy storage, building materials, constructions, and others. Nanoparticles are ultra-small particles with exceptional properties, but some nanoparticles and nanomaterials may exhibit harmful properties when leaked into the environment. Due to the lack of analytical methods for the detection and analysis of nanoparticles in complex matrices, not much is known about the potential risks associated with nanomaterials. Therefore, more knowledge is needed of the sampling and analysis of nanomaterials (NMs) as environmental contaminants. This review is undertaken to identify and assess key characteristics in potential sampling and analysis methods for identifying and quantifying the occurrence of NMs in numerous types of environmental media. To select suitable sampling and analysis methods, information on NM sources and transformation in environmental media is essential and thus is also discussed. This provides more information about the negative impacts of NMs on the environment. Challenges and future perspectives on the determination of NMs are also discussed.     

Nanosorbents as Materials for Extraction Processes of Environmental Contaminants and Others

The aim of this work focuses on the application of nanomaterials (NMs) in different sorptive extraction techniques for the analysis of organic contaminants from environmental samples of distinct matrix compositions. Without any doubt, the integration of specific NMs such as carbonaceous nanomaterials, magnetic nanoparticles (MNPs), metal–organic frameworks (MOFs), silica nanoparticles, and ion-imprinted NPs with solid-phase extraction techniques counting d-SPE, solid-phase microextraction (SPME), and stir bar sorptive extraction (SBSE) impact on the improvements in analytical performance. The application of NMs as sorbents in the extraction of organic pollutants in environmental samples allows for providing better sensitivity, repeatability, reproducibility, and reusability.     

Preparation of Photocatalytic Au–Ag2Te Nanomaterials

A facile approach has been developed for the preparation of various morphologies of Au–Ag₂Te nanomaterials (NMs) that exhibit strong photocatalytic activity. Te NMs (nanowires, nanopencils, and nanorice) were prepared from TeO₂ in the presence of various concentrations (16, 8, and 4 M ) of a reducing agent (N₂H₄) at different temperatures (25 and 60 °C). These three Te NMs were then used to prepare Au–Ag₂Te NMs by spontaneous redox reactions with Au³⁺ and Ag⁺ ions sequentially. The Au–Ag₂Te nanopencils exhibit the highest activity toward degradation of methylene blue and formation of active hydroxyl radicals on solar irradiation, mainly because they absorb light in the visible region most strongly. All three differently shaped Au–Ag₂Te NMs (10 μg mL^?1) provide a death rate of Escherichia coli greater than 80 % within 60 min, which is higher than that of 51 % for commercial TiO₂ nanoparticles (100 μg mL^?1). Under light irradiation, the Au NPs in Au–Ag₂Te NMs enhance the overall photo‐oxidation ability of Ag₂Te NMs through faster charge separation because of good contact between Ag₂Te and Au segments. With high antibacterial activity and low toxicity toward normal cells, the Au–Ag₂Te NMs hold great potential for use as efficient antibacterial agents.     

Health impact and safety of engineered nanomaterials

Many engineered nanomaterials (NMs) are being synthesized and explored for potential use in consumer and medical products. Already, nanoparticles (NPs) of titanium dioxide (TiO(2)), zinc oxide (ZnO), silver (Ag) and other metals or their oxides are present in commercial products such as sunscreens, cosmetics, wound dressings, surgical tools, detergents, automotive paints and tires. More recent and advanced FDA-approved use of NMs includes quantum dots (QDs) in live cell imaging, zirconium oxides in bone replacement and prosthetic devices and nanocarriers in drug delivery. The benefits from nanotechnology are aplenty, comprising antimicrobial activities, scratch- and water-resistance, long-lasting shine, improved processor speeds and better display resolution, to name a few. While developers of these products often focus on the exciting beneficial aspects of their products, safety and toxicity issues are often not discussed in detail. Long-term effects such as chronic exposure and environmental pollution are even less documented. Along with widespread manufacture and use of NMs, concerns for occupational hazards, proper handling, disposal, storage, shipping and clean up are expected to rise. This review focus on the possible biological impact of engineered NPs, serving as a reminder that nanomaterials can become a double-edged sword if not properly handled.     

Nanomaterials and lab-on-a-chip technologies

Lab-on-a-chip (LOC) platforms have become important tools for sample analysis and treatment with interest for DNA, protein and cells studies or diagnostics due to benefits such as the reduced sample volume, low cost, portability and the possibility to build new analytical devices or be integrated into conventional ones. These platforms have advantages of a wide set of nanomaterials (NM) (i.e. nanoparticles, quantum dots, nanowires, graphene etc.) and offer excellent improvement in properties for many applications (i.e. detectors sensitivity enhancement, biolabelling capability along with other in-chip applications related to the specificities of the variety of nanomaterials with optical, electrical and/or mechanical properties). This review covers the last trends in the use of nanomaterials in microfluidic systems and the related advantages in analytical and bioanalytical applications. In addition to the applications of nanomaterials in LOCs, we also discuss the employment of such devices for the production and characterization of nanomaterials. Both framed platforms, NMs based LOCs and LOCs for NMs production and characterization, represent promising alternatives to generate new nanotechnology tools for point-of-care diagnostics, drug delivery and nanotoxicology applications.     

Quantifying the dissolution of nanomaterials at the nano-bio interface

With the rapid development of nanoscience and nanotechnology, more engineered nanomaterials(NMs) are being released into the environment. Such releases might lead to unwanted exposure. The dissolution of NMs at nano-bio interfaces is one of the most noteworthy causes of the toxicity of dissolvable NMs. A growing number of studies are focusing assessing NMs dissolution during exposure tests. This mini review considers recent developments in the quantitative tools for the assessment of NMs dissolution, and highlights the critical points in the evaluation of the toxicity of dissolvable NMs.     

Benchmarking the ACEnano Toolbox for Characterisation of Nanoparticle Size and Concentration by Interlaboratory Comparisons

ACEnano is an EU-funded project which aims at developing, optimising and validating methods for the detection and characterisation of nanomaterials (NMs) in increasingly complex matrices to improve confidence in the results and support their use in regulation. Within this project, several interlaboratory comparisons (ILCs) for the determination of particle size and concentration have been organised to benchmark existing analytical methods. In this paper the results of a number of these ILCs for the characterisation of NMs are presented and discussed. The results of the analyses of pristine well-defined particles such as 60 nm Au NMs in a simple aqueous suspension showed that laboratories are well capable of determining the sizes of these particles. The analysis of particles in complex matrices or formulations such as consumer products resulted in larger variations in particle sizes within technologies and clear differences in capability between techniques. Sunscreen lotion sample analysis by laboratories using spICP-MS and TEM/SEM identified and confirmed the TiO₂ particles as being nanoscale and compliant with the EU definition of an NM for regulatory purposes. In a toothpaste sample orthogonal results by PTA, spICP-MS and TEM/SEM agreed and stated the TiO₂ particles as not fitting the EU definition of an NM. In general, from the results of these ILCs we conclude that laboratories are well capable of determining particle sizes of NM, even in fairly complex formulations.     

Emerging nanomedicine and prodrug delivery strategies for the treatment of inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic and recurrent disease of the gastrointestinal tract, mainly including Crohn's disease (CD) and ulcerative colitis (UC). However, current approaches against IBD do not precisely deliver drugs to the inflammatory site, which leads to life-long medication and serious side effects that can adversely impact patients’ adherence. It is necessary to construct optimal drug delivery systems (DDSs) that can target drugs to the region of inflammation, thereby improve therapeutic efficacy and reduce side effects. With the burgeoning development of nanotechnology-based nanomedicines (NMs) and prodrug strategy, remarkable progresses in the treatment of IBD have been made in recent years. Herein, the latest advances are outlined at the intersection of IBD treatment and nanotherapeutics as well as prodrug therapy. First, the pathophysiological microenvironment of inflammatory sites of IBD is introduced in order to rationally design potential NMs and prodrugs. Second, the necessity of NMs for the IBD therapy is elaborated, and the representative nanotherapeutics via passive targeted and active targeted NMs developed to treat the IBD are overviewed. Furthermore, the emerging prodrug-based therapeutics are summarized, including 5-aminosalicylic acid-, amino acid-, and carbohydrate-conjugated prodrugs. Finally, the design considerations and perspectives of these NMs and prodrugs-driven IBD therapeutics in the clinical translation are spotlighted.     

Antibacterial Activities of Tellurium Nanomaterials

We prepared four differently shaped Te nanomaterials (NMs) as antibacterial reagents against Escherichia coli. By controlling the concentrations of hydrazine (N₂H₄) as reducing agent, NaCl, and temperature, we prepared Te nanowires, nanopencils, nanorices, and nanocubes. These four Te NMs resulted in a live/dead ratio of E. coli cells of less than 0.1, which is smaller than that of Ag nanoparticles. The order of antibacterial activity against E. coli is nanocubes ≈ nanorices > nanopencils ≈ nanowires. This is in good agreement with the concentration order of tellurite (TeO₃²⁻) ions released from Te NMs in E. coli cells, revealing that TeO₃²⁻ ions account for the antibacterial activity of the four Te NMs. We found that spherical Te nanoparticles (32 nm in diameter) with TeO₃²⁻ ions were formed in the E. coli cells. Compared to Ag nanoparticles that are commonly used as antibacterial reagents, Te NMs have higher antibacterial activity and lower toxicity. Thus, Te NMs hold great practical potential as a new and efficient antibacterial agent.     

In-situ thermal crosslinked PA66/β-cyclodextrin/PA66 nanofibrous membranes with high mechanical strength for removal of heavy metal ions by flow through adsorption

β-cyclodextrin (β-CD) based materials have been studied widely as adsorbents and filter membranes for removing pollutants in air or water applications. The present study aimed to develop a sandwich structure of eletrospun nanofibrous membrane based on β-cyclodextrin and PA66 to achieve the high mechanical strength and flow-through adsorption of heavy metal ions in water. The surface and cross section morphology of PA66/β-cyclodextrin/PA66 nanofibrous membranes (PA66/β-CD/PA66 NMs) were examined using scanning electron microscopy (SEM). The physicochemical and mechanical properties of PA66/β-CD/PA66 NMs were analyzed by differential scanning calorimetry (DSC), thermogravimetric (TG) analysis and universal testing machine. The diameter of β-CD and PA66 electrospun fibers are 300–400 nm and 20–40 nm respectively. PA66/β-CD/PA66 NMs show a loosely arranged fibers and layer by layer structure. The tensile strength increases remarkably for PA66/β-CD/PA66 NMs, from 1.33 MPa of β-CD NMs to 23.17 MPa and the Young's modulus increases from 34.8 MPa to 253.3 MPa. The mechanical behavior of PA66/β-CD/PA66 NMs is a typical brittle fracture, and its microcosmic fracture diagrams are also involved. TGA/DSC results confirm the thermal crosslinking reaction is effective and complete. On the basis of SEM, DSC, TG and mechanical behavior analysis results, the molecular mechanism of in situ thermal crosslinking reaction is discussed. Fe³⁺、Ni²⁺ were used to confirm the ability to absorb heavy metal ions of PA66/β-CD/PA66 NMs. In conclusion, PA66/β-CD/PA66 NMs could be a promising solution for removal of metal ions by flow-through adsorption.     

Determining nanomaterials in food

Nanotechnology has emerged as one of the most innovative technologies and has the potential to improve food quality and safety. However, there are a few studies demonstrating that nanomaterials (NMs) are not inherently benign.This review highlights some current applications of NMs in food, food additives and food-contact materials, and reviews analytical approaches suitable to address food-safety issues related to nanotechnology.We start with a preliminary discussion on the current regulatory situation with respect to nanotechnology in relation to foods. We cover sample preparation, imaging techniques (e.g., electron microscopy, scanning electron microscopy and X-ray microscopy), separation methods (e.g., field-flow fractionation and chromatographic techniques) and detection or characterization techniques (e.g., light scattering, Raman spectroscopy and mass spectrometry). We also show the first applications of the analysis of NMs in food matrices.     

Probing the interaction at nano-bio interface using synchrotron radiation-based analytical techniques

Understanding the interactions of nanomaterials(NMs) with biomolecules, organelles, cells, and organic tissues at the nano-bio interface can offer important information for their uptake, distribution, translocation, metabolism and degradation in vitro and in vivo, which can help to precisely tune and design "smart" NMs for biomedical applications. However, probing the interactions at the nano-bio interface, which generally requires dedicated analytical methods and tools, is remarkably complicated due to the dynamically changed nature of the nano-bio interface. Because of the advantages of high spatial resolution, high sensitivity, excellent accuracy, low matrix effects and non-destructiveness, synchrotron radiation(SR)-based analytical techniques have become extremely valuable tools. Herein, we present a comprehensive overview of SR-based techniques for the visualized study of NMs at cellular and subcellular interfaces and their transformation in vitro; the exploration of biodistribution, translocation, metabolism and degradation of NMs in vivo; and clarification of the molecular mechanisms of NMs' reactions with biomolecules. Rapid development of advanced light source means that in situ, real-time analysis of NMs at the nano-bio interface will be achieved.     

Nanomaterials in Protein Sample Preparation

Protein sample preparation is the most critical step in protein analysis of complex samples and is constituted by tedious, time-consuming, and difficult-to-automate steps that usually involve the use of high volumes of solvents. In recent years, novel extraction or digestion nanomaterials (NMs) have been developed aiming to overcome these drawbacks. In this review, we have grouped the recent works related to the development of new NMs and their applications to the extraction, enrichment/purification, and digestion of proteins. This paper evaluates the role of different kinds of NMs in each step of protein sample preparation focusing on the type of established interaction between the protein and the nanomaterial, their sensitivity and selectivity, their adsorption capacity, and the advantages that they bring in relation to time, efficiency, or reusability.     

Antimonene Quantum Dots: Synthesis and Application as Near‐Infrared Photothermal Agents for Effective Cancer Therapy

Photothermal therapy (PTT) has shown significant potential for cancer therapy. However, developing nanomaterials (NMs)‐based photothermal agents (PTAs) with satisfactory photothermal conversion efficacy (PTCE) and biocompatibility remains a key challenge. Herein, a new generation of PTAs based on two‐dimensional (2D) antimonene quantum dots (AMQDs) was developed by a novel liquid exfoliation method. Surface modification of AMQDs with polyethylene glycol (PEG) significantly enhanced both biocompatibility and stability in physiological medium. The PEG‐coated AMQDs showed a PTCE of 45.5 %, which is higher than many other NMs‐based PTAs such as graphene, Au, MoS₂, and black phosphorus (BP). The AMQDs‐based PTAs also exhibited a unique feature of NIR‐induced rapid degradability. Through both in vitro and in vivo studies, the PEG‐coated AMQDs demonstrated notable NIR‐induced tumor ablation ability. This work is expected to expand the utility of 2D antimonene (AM) to biomedical applications through the development of an entirely novel PTA platform.