Anisotropic Gold Nanoparticles: Synthesis, Properties, Applications, and Toxicity

Research on photocatalytic CO2 conversion to renewable synthetic fuels based on localized surface plasmon resonance: current progress and future perspectives

Due to its desirable optoelectronic properties, localized surface plasmon resonance (LSPR) can hopefully play a promising role in photocatalytic CO2 reduction reaction (CO2RR). In this review, mechanisms and applications of LSPR effect in this field are introduced in detail.

Chiral Seeded Growth of Gold Nanorods Into Fourfold Twisted Nanoparticles with Plasmonic Optical Activity

A robust and reproducible methodology to prepare stable inorganic nanoparticles with chiral morphology may hold the key to the practical utilization of these materials. An optimized chiral growth method to prepare fourfold twisted gold nanorods is described herein, where the amino acid cysteine is used as a dissymmetry inducer. Four tilted ridges are found to develop on the surface of single-crystal nanorods upon repeated reduction of HAuCl4 , in the presence of cysteine as the chiral inducer and ascorbic acid as a reducing agent. From detailed electron microscopy analysis of the crystallographic structures, it is proposed that the dissymmetry results from the development of chiral facets in the form of protrusions (tilted ridges) on the initial nanorods, eventually leading to a twisted shape. The role of cysteine is attributed to assisting enantioselective facet evolution, which is supported by density functional theory simulations of the surface energies, modified upon adsorption of the chiral molecule. The development of R-type and S-type chiral structures (small facets, terraces, or kinks) would thus be non-equal, removing the mirror symmetry of the Au NR and in turn resulting in a markedly chiral morphology with high plasmonic optical activity.

Surfactant assisted reactive crystallization of cobalt oxide nanoparticles in a tubular microreactor: effects of precursor concentrations and type of surfactants

The particle size distributions in CTAB and Tween-80 assisted reactive crystallization of CoO nanoparticles using CoCl2·6H2O and NaBH4 at two molar ratios in a tubular microreactor were investigated for establishing suitability of surfactants.

Electrically controllable self-assembly of gold nanorods into a plasmonic nanostructure for highly efficiency SERS

In this Letter, a method for the rapid and efficient preparation of ultrasensitive detection substrates by assembling gold nanorod suspensions with the application of an alternating current (AC) field is proposed, and it is found that frequency and voltage are the effective means of regulation. A sandwich structure (parallel SiO₂ plate) not only effectively slows down the evaporation rate, but also visually reveals the changes in the assembly process. Under the optimal assembly conditions, the sensitivity and uniformity of the substrate to different probe molecules are tested. The Raman detection results experimentally show that the detection limits of Rhodamine 6G (Rh6G), crystal violet (CV), and Aspartame (APM) molecular solutions are 10^-14 M, 10^-10 M, and 62.5 mg/L, respectively, and the mixed dye molecular solutions can also be effectively distinguished. Furthermore, Rh6G and CV characteristic peaks at 1647 cm^-1 and 1619 cm^-1 were measured at randomly selected positions, and their relative standard deviations (RSDs) were 5.63% and 8.45%, respectively, indicating that the substrate has good uniformity. The effective regulation of the self-assembly results of nanoparticles will further enhance the practical application effect of surface-enhanced Raman technology and expand the application prospects of this technology.

Triple Enhancement for Sensitive Immunochromatographic Assay: A Case Study for Human Fatty Acid-Binding Protein Detection

The work considers a combination of three enhancing approaches for immunochromatographic assay (ICA) and the integration of their impacts into changes of the limit of detection (LOD). Human fatty acid binding protein (FABP), an early biomarker of acute myocardial infarction, was the target analyte. Starting from the common ICA protocol with an LOD equal to 11.2 ng/mL, three approaches were realized: (1) replacement of spherical gold nanoparticles with gold nanoflowers having a branched surface (20-fold lowering the LOD); (2) enhanced labeling of immune complexes via nanoparticle aggregates (15-fold lowering); (3) in-situ growth of bound nanoparticles by reduction of gold salts (3-fold lowering). Single and combined implementations of these approaches have been studied. It has been shown that the LOD decrease for combined approaches is close to the multiplied contribution of each of them. The final LOD for FABP was 0.05 ng/mL, which is 220 times lower than the LOD for the common ICA protocol. The efficiency of the enhanced ICA with three combined approaches was confirmed by testing human serum samples for FABP presence and content. The development presents a new efficient technique for rapid sensitive detection of FABP for medical diagnostics. Moreover, the demonstrated multiple enhancements could be applied for various demanded analytes.

A Review on Gold Nanotriangles: Synthesis, Self-Assembly and Their Applications

Gold nanoparticles (AuNPs) with interesting optical properties have attracted much attention in recent years. The synthesis and plasmonic properties of AuNPs with a controllable size and shape have been extensively investigated. Among these AuNPs, gold nanotriangles (AuNTs) exhibited unique optical and plasmonic properties due to their special triangular anisotropy. Indeed, AuNTs showed promising applications in optoelectronics, optical sensing, imaging and other fields. However, only few reviews about these applications have been reported. Herein, we comprehensively reviewed the synthesis and self-assembly of AuNTs and their applications in recent years. The preparation protocols of AuNTs are mainly categorized into chemical synthesis, biosynthesis and physical-stimulus-induced synthesis. The comparison between the advantages and disadvantages of various synthetic strategies are discussed. Furthermore, the specific surface modification of AuNTs and their self-assembly into different dimensional nano- or microstructures by various interparticle interactions are introduced. Based on the unique physical properties of AuNTs and their assemblies, the applications towards chemical biology and sensing were developed. Finally, the future development of AuNTs is prospected.

Synthesis of novel carbon-supported iron oxide sorbents for adsorption of dye from aqueous solutions: equilibrium and flow-through studies

Textile effluents contain dyes that negatively affect water bodies and inhibit photosynthesis by reducing sunlight penetration. This study investigated the adsorption capacity of an iron oxide sorbent immobilised on naturally derived carbon foam for the removal of organic methylene blue dye from water. In this study, the carbon precursor and iron oxide precursor were mixed and carbonised in a single vessel. Baking and carbonization of the natural grain combination produce a porous structure that can act as an effective support for the iron oxide particles. The carbon foam prepared had a self-assembled structure with flour as a basic element. Sorbents of 6 weight (wt)%, 15 wt% iron, and a 0 wt% iron control sample were prepared. Transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET) techniques were used to examine the synthesised carbon foam physical properties and surface morphology. The adsorption capabilities were investigated in batch tests by determining the effects of an increase in iron content, sorbent dosage, contact time, and dye concentration. Breakthrough curves were obtained by varying the height of the sorbent bed and varying the flowrate of the dye solution. A higher bed height corresponds to a greater amount of adsorbent. The breakthrough and equilibrium adsorption capacities were found to increase with increasing bed height. When the flow rate is high, the dye solution leaves the column before equilibrium, resulting in shorter breakthrough and saturation times. Higher bed heights and lower flow rates resulted in optimal dye removal in the flow through the system. Breakthrough time increases with increasing iron content. The 15 wt% iron sample displayed superior adsorption capabilities than the 6 wt% sample, while the 0 wt% iron control sample displayed minimal adsorptive capabilities. The pseudo-first order kinetic model was the best fit model for this study (R² > 0.96), and the adsorption equilibrium is best described by the Freundlich isotherm (R² > 0.99). The results showed that an iron oxide sorbent immobilised on carbon foam made from natural sources is a good adsorbent for removing methylene dye.

Rapid Synthesis of Metal Nanoparticles Using Low-Temperature, Low-Pressure Argon Plasma Chemistry and Self-Assembly

The synthesis of metal nanoparticles has become a priority for the advancement of nanotechnology. In attempts to create these nanoparticles, several different methods: chemistry, physics, and biology, have all been used. In this study, we report the reduction of cations using argon plasma chemistry to produce nanoparticles of gold (AuNPs), silver (AgNPs), and copper (CuNPs). Although other groups have used plasma-reduction methods to synthesize metal nanoparticles from their cation counterparts, these approaches often require plasma|liquid state interactions, high temperature, specific combinations of gases, and extended treatment times (>10 minutes), for which only specific cations (noble or non-noble) may be reduced. As a result, we have developed a non-thermal, low-pressure argon-plasma|solid state approach for the reduction of both noble and non-noble cations. More specifically, when 50-μL droplets of 2-mM solutions of gold(III) chloride, silver nitrate, or copper(II) sulfate are exposed to vacuum, they undergo an evaporation process. As the pressure in the chamber decreases to 220 mtorr, the droplets become completely evaporated, leaving behind a metal precursor. Nucleation and growth studies reveal that when the metal precursors of gold(III) chloride, silver nitrate, and copper(II) sulfate are treated with 80 watts of argon plasma for 5, 60, and 150 seconds, respectively, nanoparticles could be synthesized with efficiency rates of upwards of 98%. The size of nanoparticles synthesized in this work was studied using Scanning Electron Microscopy, and the scattering properties of the nanoparticles was studied using UV/Vis spectroscopy. Transmission Electron Microscopy with corresponding elemental analysis was also very useful in confirming the identity of the synthesized nanoparticles. The results from this study reveal that we have synthesized metal nanoparticles with distinct chemical and physical properties. Scanning Electron Microscopy depicts AgNPs with a round-shape and diameters from 40 - 80 nm, while AuNPs were hexagonal, with sizes from 40 - 80 nm, and CuNPs were rod-shaped, with dimensions 40 by 160 nm. Our findings demonstrate that the argon plasma approach used in this study is a rapid, green, and versatile reduction method for the synthesis of both noble and non-noble metal nanoparticles.

Materials Perspectives of Integrated Plasmonic Biosensors

With the growing need for portable, compact, low-cost, and efficient biosensors, plasmonic materials hold the promise to meet this need owing to their label-free sensitivity and deep light-matter interaction that can go beyond the diffraction limit of light. In this review, we shed light on the main physical aspects of plasmonic interactions, highlight mainstream and future plasmonic materials including their merits and shortcomings, describe the backbone substrates for building plasmonic biosensors, and conclude with a brief discussion of the factors affecting plasmonic biosensing mechanisms. To do so, we first observe that 2D materials such as graphene and transition metal dichalcogenides play a major role in enhancing the sensitivity of nanoparticle-based plasmonic biosensors. Then, we identify that titanium nitride is a promising candidate for integrated applications with performance comparable to that of gold. Our study highlights the emerging role of polymer substrates in the design of future wearable and point-of-care devices. Finally, we summarize some technical and economic challenges that should be addressed for the mass adoption of plasmonic biosensors. We believe this review will be a guide in advancing the implementation of plasmonics-based integrated biosensors.

Gold nanoparticles: current and upcoming biomedical applications in sensing, drug, and gene delivery

Gold nanoparticles (AuNPs) present unique physicochemical characteristics, low cytotoxicity, chemical stability, size/morphology tunability, surface functionalization capability, and optical properties which can be exploited for detection applications (colorimetry, surface-enhanced Raman scattering, and photoluminescence). The current challenge for AuNPs is incorporating these properties in developing more sensible and selective sensing methods and multifunctional platforms capable of controlled and precise drug or gene delivery. This review briefly highlights the recent progress of AuNPs in biomedicine as bio-sensors and targeted nano vehicles.

In Vivo Kidney Allograft Endothelial Specific Scavengers for On-Site Inflammation Reduction under Antibody-Mediated Rejection

Kidney transplantation is the most effective therapy for patients with end-stage renal disease. However, antibody-mediated rejection (ABMR) threatens long-term survival of renal grafts. Although ABMR can be controlled by donor-specific antibody clearance and B- or (and) plasma-cells inhibition, the treatment often causes severe side effects in patients. Therefore, there is need to explore site-specific scavengers. In this study, a nanovehicle carrying an anti-inflammatory drug is developed with complement component 4d targeting, a specific biomarker expressed on allograft endothelium under ABMR. Moreover, the nanovehicle is endowed with photothermal properties to control drug release. Analysis through systematic in vitro and in vivo toxicity, non-invasive targeted imaging, and in situ remote controlled drug release show the nanovehicle specifically targets allograft kidney endothelium, releases an anti-inflammatory drug, methylprednisolone, locally upon laser irradiation, and promotes recovery of injured endothelium, without affecting systemic inflammation or innate immune responses. This strategy has the potential for future clinical application in ABMR treatment.

The emergence of nanotechnology and a revolution in diagnostic methods of biological threat agents

Nanotechnology is applied in wide-ranging fields including energy, information technology, consumables, medicine, etc. Nanomedicine includes the medical applications of nanomaterials in the fields of diagnosis and treatment. This paper focuses on the application of nanotechnology in medical diagnostics for which the main applications of nanomedicine include the detection and discovery of specific biomarkers and rapid identification of biological agents. The introduction of nanotechnology into the medical field before a serious increase in disease symptoms makes early diagnosis possible, thereby preventing more damage to the patient. With the manufacture of nanomaterials and novel entities, reduced size of sensing instruments, as well as biochips and bionanosensors, nanotechnology has revolutionized diagnostic methods. Gold nanoparticles (NPs), quantum dots (QDs), nanotubes, polymeric NPs, and liposomes are among NPs used in medical diagnostics. The importance of these diagnostic methods is redoubled whenever there is a need for the rapid and accurate diagnosis of biological threat agents

Gold Nanoparticles Contact with Cancer Cell: A Brief Update

The fine-tuning of the physicochemical properties of gold nanoparticles has facilitated the rapid development of multifunctional gold-based nanomaterials with diagnostic, therapeutic, and therapeutic applications. Work on gold nanoparticles is increasingly focusing on their cancer application. This review provides a summary of the main biological effects exerted by gold nanoparticles on cancer cells and highlights some critical factors involved in the interaction process (protein corona, tumor microenvironment, surface functionalization). The review also contains a brief discussion of the application of gold nanoparticles in target discovery.

Growing Gold Nanostars on SiO2 Nanoparticles: Easily Accessible, NIR Active Core–Shell Nanostructures from PVP/DMF Reduction

A new synthesis strategy towards gold-coated silica nanoparticles is presented. The method provides an efficient, reliable and facile-coating process of well-defined star-shaped shell structures, characterized by UV-Vis, TEM, PXRD, DLS and zeta-potential measurements. A marked red shift of the Au-based plasmonic band to the region of the first biological window is observed offering great potential for future research of biological applications.

Nanotechnology-Based Diagnostic and Therapeutic Strategies for Neuroblastoma

Neuroblastoma (NB), as the most common extracranial solid tumor in childhood, is one of the critical culprits affecting children's health. Given the heterogeneity and invisibility of NB tumors, the existing diagnostic and therapeutic approaches are inadequate and ineffective in early screening and prognostic improvement. With the rapid innovation and development of nanotechnology, nanomedicines have attracted widespread attention in the field of oncology research for their excellent physiological and chemical properties. In this review, we first explored the current common obstacles in the diagnosis and treatment of NB. Then we comprehensively summarized the advancements in nanotechnology-based multimodal synergistic diagnosis and treatment of NB and elucidate the underlying mechanisms. In addition, a discussion of the pending challenges in biocompatibility and toxicity of nanomedicine was conducted. Finally, we described the development and application status of nanomaterials against some of the recognized targets in the field of NB research, and pointed out prospects for nanomedicine-based precision diagnosis and therapy of NB.

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.

Overview of the Influence of Silver, Gold, and Titanium Nanoparticles on the Physical Properties of PEDOT:PSS-Coated Cotton Fabrics

Metallic nanoparticles have been of interest to scientists, and they are now widely used in biomedical and engineering applications. The importance, categorization, and characterization of silver nanoparticles, gold nanoparticles, and titanium nanoparticles have been discussed. Poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) is the most practical and reliable conductive polymer used in the manufacturing of conductive textiles. The effects of metallic nanoparticles on the performance of PEDOT:PSS thin films are discussed. The results indicated that the properties of PEDOT:PSS significantly depended on the synthesis technique, doping, post-treatment, and composite material. Further, electronic textiles known as smart textiles have recently gained popularity, and they offer a wide range of applications. This review provides an overview of the effects of nanoparticles on the physical properties of PEDOT:PSS-coated cotton fabrics.

A New Strategy to Fabricate Nanoporous Gold and Its Application in Photodetector

Nanoporous gold (NPG) plays an important role in high-performance electronic devices, including sensors, electrocatalysis, and energy storage systems. However, the traditional fabricating methods of NPG, dealloying technique or electrochemical reduction technique, usually require complex experimental procedures and sophisticated equipment. In this work, we reported a unique and simple method to prepare the NPG through a low-temperature solution process. More importantly, the structure of the NPG-based electrode can be further controlled by using the post-treatment process, such as thermal treatment and plasma treatment. Additionally, we also demonstrate the application of the resulting NPG electrodes in flexible photodetectors, which performs a higher sensitivity than common planar photodetectors. We believe that our work opens a possibility for the nanoporous metal in future electronics that is flexible, large scale, with facile fabrication, and low cost.

Anisotropic Particle Fabrication Using Thermal Scanning Probe Lithography

Size, shape, and chemical properties of nanoparticles are powerful tools to modulate the optical and physicochemical properties of a particle suspension. Despite having many methods to synthesize anisotropic nanoparticles, often there are challenges in terms of controlling the polydispersity, shape, size, or composition of anisotropic nanoparticles. This work has been inspired by the potential for developing a unique pathway to make different shaped monodispersed anisotropic nano- and microparticles with large flexibility in material choice. Compared to existing methods, this state-of-the-art nanolithographic method is fast, easy to prototype, and much simple in terms of its mechanical requirement. We show that this technique has been efficiently used to make a variety of anisotropic nano- and microparticles of different shapes, such as triangular prisms, ovals, disks, flowers, and stairs following the same pathway, at the same time showing the potential of being flexible with respect to the composition of the particles. The thermal scanning probe lithographic method in combination with dry reactive ion etching was used to make two-dimensional and three-dimensional templates for the fabrication of anisotropic nano- and microparticles. Deposition of different metal/metal oxides by the electron-beam evaporation method onto these templates allowed us to fabricate a range of nanomaterials according to the required functionality in potential applications. The particles were characterized by atomic force microscopy, He-ion microscopy, scanning electron microscopy, and dynamic light scattering to ensure that the developed method is reproducible, flexible, and robust in choosing the shapes for making monodispersed anisotropic nanoparticles with great control over shape and size.

Deep Tumor Penetrating Gold Nano-Adjuvant for NIR-II-Triggered In Situ Tumor Vaccination

Local tumor photothermal treatment with the near-infrared light at the second window (NIR-II) is a promising strategy in triggering the in situ tumor vaccination (ISTV) for cancer therapy. However, limited penetration of photothermal agents within tumors seriously limits their spatial effect in generating sufficient tumor-associated antigens, a key factor to the success of ISTV. In this study, a nano-adjuvant system is fabricated based on the NIR-II-absorbable gold nanostars decorated with hyaluronidases and immunostimulatory oligodeoxynucleotides CpG for ISTV. The nano-adjuvant displays a deep tumor penetration capacity via loosening the dense extracellular matrix of tumors. Upon NIR-II light irradiation, the nano-adjuvant significantly inhibits the tumor growth, induces a cascade of immune responses, generates an obvious adaptive immunity against the re-challenged cancers, boosts the abscopal effect, and completely inhibits the pulmonary metastases. The study highlights an advanced nano-adjuvant formulation featuring deep tumor penetration for NIR-II-triggered ISTV.

Hysteresis in the Thermo-Responsive Assembly of Hexa(ethylene glycol) Derivative-Modified Gold Nanodiscs as an Effect of Shape

Anisotropic gold nanodiscs (AuNDs) possess unique properties, such as large flat surfaces and dipolar plasmon modes, which are ideal constituents for the fabrication of plasmonic assemblies for novel and emergent functions. In this report, we present the thermo-responsive assembly and thermo-dynamic behavior of AuNDs functionalized with methyl-hexa(ethylene glycol) undecane-thiol as a thermo-responsive ligand. Upon heating, the temperature stimulus caused a blue shift of the plasmon peak to form a face-to-face assembly of AuNDs due to the strong hydrophobic and van der Waals interactions between their large flat surfaces. Importantly, AuNDs allowed for the incorporation of the carboxylic acid-terminated ligand while maintaining their thermo-responsive assembly ability. With regard to their reversible assembly/disassembly behavior in the thermal cycling process, significant rate-independent hysteresis, which is related to their thermo-dynamics, was observed and was shown to be dependent on the carboxylic acid content of the surface ligands. As AuNDs have not only unique plasmonic properties but also high potential for attachment due to the fact of their flat surfaces, this study paves the way for the exploitation of AuNDs in the development of novel functional materials with a wide range of applications.

Carbon Dots in Biomedicine: A Review

Despite the rapid development of science and technology, the effective treatment of cancer still threatens human life and health. However, the success of cancer treatment is closely related to early diagnosis, identification, and effective treatment. In recent years, with the strengthening of the development and research of nanomaterials for cancer diagnosis and treatment, researchers have found that carbon dots (CDs) have the advantages of wide absorption, excellent biocompatibility, diverse imaging characteristics, and photostability and are widely used in various fields, such as sensing, imaging, and drug/gene transportation. Recently, researchers also discovered that CDs could be used as an effective photosensitizer to generate active oxygen or convert light energy into heat under the stimulation of the external lasers, making them have the effects of photothermal and photodynamic therapy for cancer. In this review, we first outline the single-modal and multimodal imaging analysis of CDs in cancer cells. After introducing diversified imaging functions, we focused on the design and the latest research progress of CDs in phototherapy and introduced in detail the strategies of CDs in phototherapy treatment and the challenges faced by clinical applications. We hope that this overview can provide important insights for researchers and accelerate the pace of research on CDs in imaging-guided phototherapy treatment.

Preclinical safety and hepatotoxicity evaluation of biomineralized copper sulfide nanoagents

Albumin-biomineralized copper sulfide nanoparticles (Cu_2-xS NPs) have attracted much attention as an emerging phototheranostic agent due to their advantages of facile preparation method and high biocompatibility. However, comprehensive preclinical safety evaluation is the only way to meet its further clinical translation. We herein evaluate detailedly the safety and hepatotoxicity of bovine serum albumin-biomineralized Cu_2-xS (BSA@Cu_2-xS) NPs with two different sizes in rats. Large-sized (LNPs, 17.8 nm) and small-sized (SNPs, 2.8 nm) BSA@Cu_2-xS NPs with great near-infrared absorption and photothermal conversion efficiency are firstly obtained. Seven days after a single-dose intravenous administration, SNPs distributed throughout the body are cleared primarily through the feces, while a large amount of LNPs remained in the liver. A 14-day subacute toxicity study with a 28-day recovery period are conducted, showing long-term hepatotoxicity without recovery for LNPs but reversible toxicity for SNPs. Cellular uptake studies indicate that LNPs prefer to reside in Kupffer cells, leading to prolonged and delayed hepatotoxicity even after the cessation of NPs administration, while SNPs have much less Kupffer cell uptake. RNA-sequencing analysis for gene expression indicates that the inflammatory pathway, lipid metabolism pathway, drug metabolism-cytochrome P450 pathway, cholesterol/bile acid metabolism pathway, and copper ion transport/metabolism pathway are compromised in the liver by two sizes of BSA@Cu_2-xS NPs, while only SNPs show a complete recovery of altered gene expression after NPs discontinuation. This study demonstrates that the translational feasibility of small-sized BSA@Cu_2-xS NPs as excellent nanoagents with manageable hepatotoxicity.

Liposome-Tethered Gold Nanoparticles Triggered by Pulsed NIR Light for Rapid Liposome Contents Release and Endosome Escape

Remote triggering of contents release with micron spatial and sub-second temporal resolution has been a long-time goal of medical and technical applications of liposomes. Liposomes can sequester a variety of bioactive water-soluble ions, ligands and enzymes, and oligonucleotides. The bilayer that separates the liposome interior from the exterior solution provides a physical barrier to contents release and degradation. Tethering plasmon-resonant, hollow gold nanoshells to the liposomes, or growing gold nanoparticles directly on the liposome exterior, allows liposome contents to be released by nanosecond or shorter pulses of near-infrared light (NIR). Gold nanoshells or nanoparticles strongly adsorb NIR light; cells, tissues, and physiological media are transparent to NIR, allowing penetration depths of millimeters to centimeters. Nano to picosecond pulses of NIR light rapidly heat the gold nanoshells, inducing the formation of vapor nanobubbles, similar to cavitation bubbles. The collapse of the nanobubbles generates mechanical forces that rupture bilayer membranes to rapidly release liposome contents at the preferred location and time. Here, we review the syntheses, characterization, and applications of liposomes coupled to plasmon-resonant gold nanostructures for delivering a variety of biologically important contents in vitro and in vivo with sub-micron spatial control and sub-second temporal control.

Synthesis and Photocatalytic Activity of Hexagonal Plate-like Shaped Au Nanoparticles/ZnO Composite Particles under Visible-light Irradiation

We synthesized Au nanoparticle (AuNP)/ZnO composite particles in presence of an anionic surfactant and evaluated their photocatalytic activity under visible-light irradiation. AuNPs synthesized from HAuCl₄ in the presence of amylase and the precursor solutions of ZnO were mixed, followed by a hydrothermal process, to synthesize crystal face-controlled AuNP/ZnO composite particles. X-ray diffraction (XRD) patterns and ultraviolet-visible (UV-Vis) spectra confirmed the formation of AuNP/ZnO composite particles. Furthermore, different Au to Zn concentration ratios in the precursor solutions resulted in different amounts of AuNPs in the composite particles. In addition, the average size of the AuNP/ZnO composite particles decreased with increasing Au to Zn concentration ratio. We believe AuNPs act as the nuclei for ZnO particle formation. The photocatalytic activity of the AuNP/ZnO composite particles was evaluated by the photodegradation of methylene blue (MB) under visible-light irradiation. The photodegradation rate of MB was higher with AuNP/ZnO composite particles compared to that with the ZnO particles synthesized in the absence of AuNPs. The AuNP/ZnO composite particles exhibit photocatalytic activity under visible-light irradiation owing to the enhanced charge separation efficiency and the localized surface plasmon resonance effect.

Recent Development of MOF-Based Photothermal Agent for Tumor Ablation

Metal-organic frameworks (MOFs) are 3D-architecture compounds of metal ions and organic molecules with sufficient and permanent porosity, showing great potential as a versatile platform to load various functional moieties to endow the hybrid materials with specific applications. Currently, a variety of photothermal nanometals have been embedded into organic ligands for integrating the unique photothermal effects with the merits of MOFs to improve their performances for cancer therapy. In this review, we have summarized a series of novel MOF-based photothermal materials for this unique therapeutic modality against tumors from three main aspects according to their chemical compositions and structures, i) metal-doped MOF, ii) organic-doped MOF, and iii) polymer-coated MOF. In addition, we have summarized the latest developments and characteristics of MOF-based photothermal agents, such as good biocompatibility, low toxicity, and responsive photothermal conversion without destroying the structure of hybrid photothermal agent. At last, we addressed the future perspectives of MOF-based photothermal agent in the field of phototherapy.

Gold Nanomaterials-Based Electrochemical Sensors and Biosensors for Phenolic Antioxidants Detection: Recent Advances

Antioxidants play a central role in the development and production of food, cosmetics, and pharmaceuticals, to reduce oxidative processes in the human body. Among them, phenolic antioxidants are considered even more efficient than other antioxidants. They are divided into natural and synthetic. The natural antioxidants are generally found in plants and their synthetic counterparts are generally added as preventing agents of lipid oxidation during the processing and storage of fats, oils, and lipid-containing foods: All of them can exhibit different effects on human health, which are not always beneficial. Because of their relevant bioactivity and importance in several sectors, such as agro-food, pharmaceutical, and cosmetic, it is crucial to have fast and reliable analysis Rmethods available. In this review, different examples of gold nanomaterial-based electrochemical (bio)sensors used for the rapid and selective detection of phenolic compounds are analyzed and discussed, evidencing the important role of gold nanomaterials, and including systems with or without specific recognition elements, such as biomolecules, enzymes, etc. Moreover, a selection of gold nanomaterials involved in the designing of this kind of (bio)sensor is reported and critically analyzed. Finally, advantages, limitations, and potentialities for practical applications of gold nanomaterial-based electrochemical (bio)sensors for detecting phenolic antioxidants are discussed.

Recent progress in the applications of gold-based nanoparticles towards tumor-targeted imaging and therapy

Cancer death rate remains high all over the world, scientists are paying increasing attention to meet the requirements for precise diagnosis and therapy. Therefore, early diagnosis and active treatment can effectively improve the five-year survival rate of patients. In recent years, gold-based nanomaterials have received increasing attention in medical fields due to their excellent biocompatibility, low toxicity and unique properties. In addition, because of the inherent nature of gold nanomaterials including for computed tomography (CT), fluorescence/optical imaging (FI/OI), surface enhanced Raman spectroscopy imaging (SERS), photoacoustic imaging (PAI) and photothermal therapy (PTT), various gold nanomaterials were developed as theranostic nanoplatforms. In this review, we summarized the latest developments of nanomaterials in imaging and combined therapy, and the prospects for the future application of gold-based theranostic nanoplatforms were also proposed.

Gold nanostructures: synthesis, properties, and neurological applications

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

Near infrared triggered chemo-PTT-PDT effect mediated by glioma directed twin functional-chimeric peptide-decorated gold nanoroses

The successful application of nanomedicine against glioma is basically hooked on to the fabrication of specific and efficient glioma targeted multifunctional theranostics. Herein, through an easy synthetic methodology, we fabricated a type of novel multifunctional theranostic nanoplatform comprising of anisotropic gold nanoroses (AuNs) co-loaded with doxorubicin (DOX) and the near-infrared (NIR) active/responsive dye, indocyanine green (ICG). The tailored nanotheranostics upon being exposed to NIR laser helped in achieving combinatorial chemo-phototherapy along with optical cell imaging. BBB/glioma-targeting ability was realized by amalgamating the AuNs with a naive peptide drug with BBB-glioma targeting and anti-glioma twin functionality. Efficacy studies carried out in C6 cells and spheroids demonstrated heightened synergistic glioma chemo-PDT-PTT effect (~85% ablation in C6 cells and ~88% in C6 spheroids) by the AuNDIPs as compared to the individual therapeutic entities. Here, the AuNs derived nanophototheranostics with in force targeting and on-demand drug release nature will further aid in abolishing chemotherapy associated adverse events by adopting a combinatorial approach for synergistic glioma eradication.

Novel Green Approaches for the Preparation of Gold Nanoparticles and Their Promising Potential in Oncology

The difficulty of achieving targeted drug delivery following administration of currently marketed anticancer therapeutics is a still a concern. Metallic nanoparticles (NPs) developed through nanotechnology breakthroughs appear to be promising in this regard. Research studies pertaining to gold NPs have indicated their promising applicability in cancer diagnosis, drug delivery and therapy. These NPs have also recently paved the path for precise drug delivery and site-specific targeting. Our review paper thus highlights the scope and impact of biogenetically generated gold nanoparticles (NPs) in cancer therapy. In a critical, constructive, and methodical manner, we compare the advantages offered by gold NPs over other metal NPs. Moreover, we also focus on novel ‘greener’ strategies that have been recently explored for the preparation of gold NPs and shed light on the disadvantages of conventional NP synthesis routes. Future prospects pertaining to the use of gold NPs in oncotherapy and domains that require further investigation are also addressed.

Mid- and far-infrared localized surface plasmon resonances in chalcogen-hyperdoped silicon

Plasmonic sensing in the infrared region employs the direct interaction of the vibrational fingerprints of molecules with the plasmonic resonances, creating surface-enhanced sensing platforms that are superior to traditional spectroscopy. However, the standard noble metals used for plasmonic resonances suffer from high radiative losses as well as fabrication challenges, such as tuning the spectral resonance positions into mid- to far-infrared regions, and the compatibility issue with the existing complementary metal-oxide-semiconductor (CMOS) manufacturing platform. Here, we demonstrate the occurrence of mid-infrared localized surface plasmon resonances (LSPR) in thin Si films hyperdoped with the known deep-level impurity tellurium. We show that the mid-infrared LSPR can be further enhanced and spectrally extended to the far-infrared range by fabricating two-dimensional arrays of micrometer-sized antennas in a Te-hyperdoped Si chip. Since Te-hyperdoped Si can also work as an infrared photodetector, we believe that our results will unlock the route toward the direct integration of plasmonic sensors with the on-chip CMOS platform, greatly advancing the possibility of mass manufacturing of high-performance plasmonic sensing systems.

Recent Advances in the Development of Noble Metal NPs for Cancer Therapy

With the development of nanotechnology, noble metal nanoparticles are widely used in the treatment of cancer due to their unique optical properties, excellent biocompatibility, surface effects, and small size effects. In recent years, researchers have designed and synthesized a large number of nanomedicines that can be used for cancer treatment based on the morphology, physical and chemical properties, mechanism of action, and toxicological studies of noble metal nanoparticles. Furthermore, the integration of diagnosis and treatment, hyperthermia, cytotoxicity research, and drug delivery system based on the study of noble metal nanoparticles can be used as effective means for cancer treatment. This article focuses on the analysis of noble metal nanoparticles that are widely used in the treatment of cancer, such as gold nanoparticles, silver nanoparticles, platinum nanoparticles, and palladium nanoparticles. The various methods and mechanisms of action of noble metal nanoparticles in the treatment of cancer are objectively summarized in detail. Based on the research on the therapeutic safety and toxicity of noble metal nanoparticles, the development prospect of noble metal nanoparticles in the future clinical application is prospected.

Photochemical Synthesis of Silver Hydrosol Stabilized by Carbonate Ions and Study of Its Bactericidal Impact on Escherichia coli: Direct and Indirect Effects

The great attention paid to silver nanoparticles is largely related to their antibacterial and antiviral effects and their possible use as efficient biocidal agents. Silver nanoparticles are being widely introduced into various areas of life, including industry, medicine, and agriculture. This leads to their spreading and entering the environment, which generates the potential risk of toxic effect on humans and other biological organisms. Proposed paper describes the preparation of silver hydrosols containing spherical metal nanoparticles by photochemical reduction of Ag+ ions with oxalate ions. In deaerated solutions, this gives ~10 nm particles, while in aerated solutions, ~20 nm particles with inclusion of the oxide Ag2O are obtained. Nanoparticles inhibit the bacterium Escherichia coli and suppress the cell growth at concentrations of ~1 × 10-6-1 × 10-4 mol L-1. Silver particles cause the loss of pili and deformation and destruction of cell membranes. A mechanism of antibacterial action was proposed, taking into account indirect suppressing action of Ag+ ions released upon the oxidative metal dissolution and direct (contact) action of nanoparticles on bacterial cells, resulting in a change in the shape and destruction of the bacteria.

Recent Advances in Nanozymes for Bacteria-Infected Wound Therapy

Bacterial-infected wounds are a serious threat to public health. Bacterial invasion can easily delay the wound healing process and even cause more serious damage. Therefore, effective new methods or drugs are needed to treat wounds. Nanozyme is an artificial enzyme that mimics the activity of a natural enzyme, and a substitute for natural enzymes by mimicking the coordination environment of the catalytic site. Due to the numerous excellent properties of nanozymes, the generation of drug-resistant bacteria can be avoided while treating bacterial infection wounds by catalyzing the sterilization mechanism of generating reactive oxygen species (ROS). Notably, there are still some defects in the nanozyme antibacterial agents, and the design direction is to realize the multifunctionalization and intelligence of a single system. In this review, we first discuss the pathophysiology of bacteria infected wound healing, the formation of bacterial infection wounds, and the strategies for treating bacterially infected wounds. In addition, the antibacterial advantages and mechanism of nanozymes for bacteria-infected wounds are also described. Importantly, a series of nanomaterials based on nanozyme synthesis for the treatment of infected wounds are emphasized. Finally, the challenges and prospects of nanozymes for treating bacterial infection wounds are proposed for future research in this field.

Magnetic Nanoparticles: Synthesis, Anisotropy, and Applications

Anisotropy is an important and widely present characteristic of materials that provides desired direction-dependent properties. In particular, the introduction of anisotropy into magnetic nanoparticles (MNPs) has become an effective method to obtain new characteristics and functions that are critical for many applications. In this review, we first discuss anisotropy-dependent ferromagnetic properties, ranging from intrinsic magnetocrystalline anisotropy to extrinsic shape and surface anisotropy, and their effects on the magnetic properties. We further summarize the syntheses of monodisperse MNPs with the desired control over the NP dimensions, shapes, compositions, and structures. These controlled syntheses of MNPs allow their magnetism to be finely tuned for many applications. We discuss the potential applications of these MNPs in biomedicine, magnetic recording, magnetotransport, permanent magnets, and catalysis.

Green synthesis and characterization of gold-based anisotropic nanostructures using bimetallic nanoparticles as seeds

Nanostructured noble metals are of great interest because of their tunable optical and electronic properties. However, the green synthesis of anisotropic nanostructures with a defined geometry by the systematic nanoassembly of particles into specific shape, size, and crystallographic facets still faces major challenges. The present work aimed to establish an environmentally friendly methodology for synthesizing gold-based anisotropic nanostructures using starch-capped bimetallic silver/gold nanoparticles as seeds and hydrogen peroxide as a reducing agent.

Tunable plasmonic gallium nano liquid metal from facile and controllable synthesis

Liquid metal (LM) gallium (Ga) is famous for its metallic properties with unique fluidity and has been extensively utilized in modern technologies. However, chemical strategies towards nanostructured Ga are extremely challenging, which severely limits further advanced applications of Ga. This work reports a facile method, the classical galvanic replacement reaction (GRR), to readily realize the synthesis of uniform Ga nano LM through sacrificial seeds (zinc) and gallium ions (Ga³⁺). Different from the previous tedious Ga nanoparticle synthesis, the GRR can be achieved under mild conditions without involving any highly active reagents or special equipment. Surprisingly, the temperature heavily influences the results of GRR due to the unique solid-liquid phase transition of Ga LM. This work figures out the critical issues of temperature, oxygen and solvent in the GRR to successfully prepare Ga nanodroplets. Interestingly, the GRR provides a convenient strategy to control the size of Ga nano LM to mediate localized surface plasmon resonance (LSPR) in the ultraviolet region, which is hardly observed in noble metals. Besides, the nano Ga from GRR exhibits remarkable SERS detection capability with an extremely low limit of detection (10^-6 M), which ranks as the highest enhancement factor with an average value exceeding 10⁵ among Ga materials. Moreover, the SERS activity of the nano Ga shows no obvious decrease within 60 days, verifying its excellent storage stability. This work demonstrates a facile "bottom-up" chemistry for Ga LM, which could greatly benefit its potential applications in the future.

Nanomaterials: Synthesis and Applications in Theranostics

Nanomaterials are endowed with unique features and essential properties suitable for employing in the field of nanomedicine. The nanomaterials can be classified as 0D, 1D, 2D, and 3D based on their dimensions. The nanomaterials can be malleable and ductile and they can be drawn into wires and sheets. Examples of nanomaterials are quantum dots (0D), nanorods, nanowires (1D), nanosheets (2D), and nanocubes (3D). These nanomaterials can be synthesized using top-down and bottom-up approaches. The achievements of 0D and 1D nanomaterials are used to detect trace heavy metal (e.g., Pb2+) and have higher sensitivity with the order of five as compared to conventional sensors. The achievements of 2D and 3D nanomaterials are used as diagnostic and therapeutic agents with multifunctional ability in imaging systems such as PET, SPECT, etc. These imaging modalities can be used to track the drug in living tissues. This review comprises the state-of-the-art of the different dimensions of the nanomaterials employed in theranostics. The nanomaterials with different dimensions have unique physicochemical properties that can be utilized for therapy and diagnosis. The multifunctional ability of the nanomaterials can have a distinct advantage that is used in the field of theranostics. Different dimensions of the nanomaterials would have more scope in the field of nanomedicine.

Size Distributions of Gold Nanoparticles in Solution Measured by Single-Particle Mass Photometry

Specialized applications of nanoparticles often call for particular, well-characterized particle size distributions in solution, but this property can prove difficult to measure. High-throughput methods, such as dynamic light scattering, detect nanoparticles in solution with an efficiency that scales with diameter to the sixth power. This diminishes the accuracy of any determination that must span a range of particle sizes. The accurate classification of broadly distributed systems thus requires very large numbers of measurements. Mass-filtered particle-sensing techniques offer a better dynamic range but are labor-intensive and so have low throughput. Progress in many areas of nanotechnology requires a faster, lower-cost, and more accurate measure of particle size distributions, particularly for diameters smaller than 20 nm. Here, we present a tailored interferometric microscope system, combined with a high-speed image-processing strategy, optimized for real-time particle tracking that determines accurate size distributions in nominal 5, 10, and 15 nm colloidal gold nanoparticle systems by automatically sensing and classifying thousands of single particles sampled from solution at rates as high as 4000 particles per minute. We demonstrate this method by sensing the irreversible binding of gold nanoparticles to poly-d-lysine functionalized coverslips. Variations in the single-particle signal as a function of time and mass, calibrated by TEM, show clear evidence for the presence of diffusion-limited transport that most affects larger particles in solution.

Lethal effects and ultrastructure of cellular uptake of ingested gold nanoparticles in the freshwater rotifer Brachionus calyciflorus (Monogononta: Brachionidae)

Much of the recent literature concerning the threat posed by anthropogenic microscopic pollution has focussed on marine organisms although freshwater environments face the same degree of pollution and therefore risk. Although several studies have documented the ingestion of nanoparticles (NPs) in species of the pelagic freshwater rotifer genus Brachionus, unambiguous evidence for its cellular uptake in this group remains lacking. We therefore used transmission electron microscopy (TEM) of ultrathin sections through the digestive tract of individuals of Brachionus calyciflorus exposed in vitro to citrate stabilized gold nanoparticles (AuCit NPs) in their culture medium to provide the first concrete evidence for the cellular uptake of NPs in rotifers, a group of organisms that comprise an important part of the zooplankton community. Using this method, AuCit NPs with average diameters of 8.5 ± 1.4 nm and 12.5 ± 1.5 nm could be localized clearly within large vacuoles within the stomach cells. Moreover, the occasional presence of pits containing AuCit NPs in the outer membranes of these cells hints that the particles are taken up by some form of endocytosis. In all cases, the ingestion of AuCit NPs showed lethal effects after only one day with virtually no individuals surviving more than two days of exposure. Combined with the TEM evidence above, we hypothesize that death might derive from some form of lysosomal overload. In total, our results document the potential threat that microscopic pollution also poses for freshwater organisms. Through this, we hope that additional emphasis in this context will be directed toward freshwater environments and the potential for such pollution both to enter as well as to move up the food chain via trophic transfer events.

Gold Nanorods: The Most Versatile Plasmonic Nanoparticles

Gold nanorods (NRs), pseudo-one-dimensional rod-shaped nanoparticles (NPs), have become one of the burgeoning materials in the recent years due to their anisotropic shape and adjustable plasmonic properties. With the continuous improvement in synthetic methods, a variety of materials have been attached around Au NRs to achieve unexpected or improved plasmonic properties and explore state-of-the-art technologies. In this review, we comprehensively summarize the latest progress on Au NRs, the most versatile anisotropic plasmonic NPs. We present a representative overview of the advances in the synthetic strategies and outline an extensive catalogue of Au-NR-based heterostructures with tailored architectures and special functionalities. The bottom-up assembly of Au NRs into preprogrammed metastructures is then discussed, as well as the design principles. We also provide a systematic elucidation of the different plasmonic properties associated with the Au-NR-based structures, followed by a discussion of the promising applications of Au NRs in various fields. We finally discuss the future research directions and challenges of Au NRs.