Bimetallic nanoparticles: Preparation, properties, and biomedical applications

Theoretical study of PdNi and PdCu clusters embedded on graphene modified by monovacancy and nitrogen doping

The stability and reactivity of Pd4Ni4 and Pd4Cu4 clusters embedded on graphene modified by monovacancy and nitrogen doping were investigated using auxiliary density functional theory (ADFT) calculations. The most stable structure of the Pd4Ni4 cluster is found in high spin multiplicity, whereas the lowest stable energy structure of the Pd4Cu4 cluster is a close shell system. The interaction energies between the bimetallic clusters and the defective graphene systems are significantly higher than those reported in the literature for the Pd-based clusters deposited on pristine graphene. It is observed that the composites studied present a HOMO-LUMO gap less than 1 eV, which suggests that they may present a good chemical reactivity. Therefore, from the results obtained in this work it can be inferred that the single vacancy graphene and pyridinic N-doped graphene are potentially good support materials for Pd-based clusters.

Lipid nanoparticle mediated small interfering RNA delivery as a potential therapy for Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative condition that exhibits a gradual decline in cognitive function and is prevalent among a significant number of individuals globally. The use of small interfering RNA (siRNA) molecules in RNA interference (RNAi) presents a promising therapeutic strategy for AD. Lipid nanoparticles (LNPs) have been developed as a delivery vehicle for siRNA, which can selectively suppress target genes, by enhancing cellular uptake and safeguarding siRNA from degradation. Numerous research studies have exhibited the effectiveness of LNP-mediated siRNA delivery in reducing amyloid beta (Aβ) levels and enhancing cognitive function in animal models of AD. The feasibility of employing LNP-mediated siRNA delivery as a therapeutic approach for AD is emphasized by the encouraging outcomes reported in clinical studies for other medical conditions. The use of LNP-mediated siRNA delivery has emerged as a promising strategy to slow down or even reverse the progression of AD by targeting the synthesis of tau phosphorylation and other genes linked to the condition. Improvement of the delivery mechanism and determination of the most suitable siRNA targets are crucial for the efficacious management of AD. This review focuses on the delivery of siRNA through LNPs as a promising therapeutic strategy for AD, based on the available literature.

Metal nanoparticles and carbohydrate polymers team up to improve biomedical outcomes

The convergence of carbohydrate polymers and metal nanoparticles (MNPs) holds great promise for biomedical applications. Researchers aim to exploit the capability of carbohydrate matrices to modulate the physicochemical properties of MNPs, promote their therapeutic efficiency, improve targeted drug delivery, and enhance their biocompatibility. Therefore, understanding various attributes of both carbohydrates and MNPs is the key to harnessing them for biomedical applications. The many distinct types of carbohydrate-MNP systems confer unique capabilities for drug delivery, wound healing, tissue engineering, cancer treatment, and even food packaging. Here, we introduce distinct physicochemical/biological properties of carbohydrates and MNPs, and discuss their potentials and shortcomings (alone and in combination) for biomedical applications. We then offer an overview on carbohydrate-MNP systems and how they can be utilized to improve biomedical outcomes. Last but not least, future perspectives toward the application of such systems are highlighted.

Silver-Gold Alloy Nanoparticles (AgAu NPs): Photochemical Synthesis of Novel Biocompatible, Bimetallic Alloy Nanoparticles and Study of Their In Vitro Peroxidase Nanozyme Activity

Facile synthesis of metal nanoparticles with controlled physicochemical properties using environment-friendly reagents can open new avenues in biomedical applications. Nanomaterials with controlled physicochemical properties have opened new prospects for a variety of applications. In the present study, we report a single-step photochemical synthesis of ~5 nm-sized silver (Ag) and gold (Au) nanoparticles (NPs), and Ag-Au alloy nanoparticles using L-tyrosine. The physicochemical and surface properties of both monometallic and bimetallic NPs were investigated by analytical, spectroscopic, and microscopic techniques. Our results also displayed an interaction between L-tyrosine and surface atoms that leads to the formation of AgAu NPs by preventing the growth and aggregation of the NPs. This method efficiently produced monodispersed NPs, with a narrow-sized distribution and good stability in an aqueous solution. The cytotoxicity assessment performed on breast cancer cell lines (MCF-7) revealed that the biofriendly L-tyrosine-capped AgNPs, AuNPs, and bimetallic AgAu NPs were biocompatible. Interestingly, AgAu NPs have also unveiled controlled cytotoxicity, cell viability, and in vitro peroxidase nanozyme activity reliant on metal composition and surface coating.

Sericin mediated gold/silver bimetallic nanoparticles and exploration of its multi-therapeutic efficiency and photocatalytic degradation potential

The current investigation aimed at bimetallic gold-silver nanoparticles (Au/Ag NPs), here called BM-GS NPs, synthesis using sericin protein as the reducing agent in an easy, cost-effective, and sustainable way. The obtained BM-GS NPs were characterized by UV-Visible spectroscopy, Transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDS), atomic force microscopy (AFM), Dynamic light scattering (DLS) and Zeta potential, X-ray Powder Diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), and Thermogravimetric analysis followed by evaluation of its multitherapeutic and photocatalytic degradation potentials. The TEM analysis revealed its spherical nature and the EDS result displayed the presence of both Ag and Au elements, confirming the synthesis of BM-GS NPs. The XRD pattern verified the crystalline nature of the nanoparticles (NPs). The DLS analysis showed an average size of 86.08 d nm and the zeta potential showed a highly negative value (-26.3 mV) which specifies that the generated bimetallic NPs are stable. The BM-GS NPs exhibited positive wound healing potential (with 63.38% of wound closure rate at 25 μg/ml, as compared to 54.42% by the untreated control) with very negligible toxicity effect on the cell viability of the normal keratinocyte cells. It also demonstrated promising antioxidant properties with 65.00%, 69.23%, and 63.03% activity at 100 μg/ml concentration for ABTS (2, 2-azinobis) (3-ethylbenzothiazoline-6-sulfonic acid)), DPPH (1, 1 diphenyl-2-picrylhydrazyl) and SOD (superoxide dismutase enzyme) assays respectively, antidiabetic potential (with a significantly high α-glucosidase inhibition potential of 99.69% at 10μg/ml concentration and 62.11% of α-amylase enzyme inhibition at 100 μg/ml concentration) and moderate tyrosinase inhibitory potential (with 17.09% at 100 μg/ml concentration). Besides, it displayed reasonable antibacterial potential with the diameter of zone of inhibition ranging between 10.89 and 12.39 mm. Further, its antibacterial mode of action reveals that its effects could be due to being very smaller, the NPs could have penetrated inside the cellular membrane thereby causing rupture and damage to the interior materials leading to cellular lysis. The photocatalytic evaluation showed that synthesized BM-GS NPs have the efficiency of degrading methylene blue dye by 34.70% within 3 h of treatment. The above findings revealed the multi-therapeutic efficacy of the sericin globular protein-mediated BM-GS NPs and its potential future applications in the cosmetics and food sector and environmental contamination management industries.

Hydrothermal Synthesis of Multifunctional Bimetallic Ag-CuO Nanohybrids and Their Antimicrobial, Antibiofilm and Antiproliferative Potential

The rapidly growing global problem of infectious pathogens acquiring resistance to conventional antibiotics is an instigating reason for researchers to continue the search for functional as well as broad-spectrum antimicrobials. Hence, we aimed in this study to synthesis silver-copper oxide (Ag-CuO) nanohybrids as a function of Ag concentration (0.05, 0.1, 0.3 and 0.5 g) via the one-step hydrothermal method. The bimetallic Ag-CuO nanohybrids Ag-C-1, Ag-C-2, Ag-C-3 and Ag-C-4 were characterized for their physico-chemical properties. The SEM results showed pleomorphic Ag-CuO crystals; however, the majority of the particles were found in spherical shape. TEM results showed that the Ag-CuO nanohybrids in formulations Ag-C-1 and Ag-C-3 were in the size range of 20-35 nm. Strong signals of Ag, Cu and O in the EDX spectra revealed that the as-synthesized nanostructures are bimetallic Ag-CuO nanohybrids. The obtained Ag-C-1, Ag-C-2, Ag-C-3 and Ag-C-4 nanohybrids have shown their MICs and MBCs against E. coli and C. albicans in the range of 4-12 mg/mL and 2-24 mg/mL, respectively. Furthermore, dose-dependent toxicity and apoptosis process stimulation in the cultured human colon cancer HCT-116 cells have proven the Ag-CuO nanohybrids as promising antiproliferative agents against mammalian cancer.

Phytochemical-Stabilized Platinum-Decorated Silver Nanocubes INHIBIT Adenocarcinoma Cells and Enhance Antioxidant Effects by Promoting Apoptosis via Cell Cycle Arrest

(1) Background: The increasing use of silver and platinum bimetallic nanoparticles in the diagnosis and treatment of cancer presents significant advances in biomedical applications due to their extraordinary physicochemical properties. This study investigated the role of aqueous phytochemical extract in stabilizing platinum nanodots-decorated silver nanocubes (w-Pt@AgNPs) for enhancing antioxidant activities and their mechanism. (2) Methods: UV-Vis, Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM) were used to characterize the formed w-Pt@AgNPs. LC-QToF-MS/MS was used to analyze the bioactive compounds, while DPPH, ABTS, and FRAP were used to detect the scavenging potential. Flow cytometric assays were performed to investigate the cytotoxicity and the mechanism of cell death. (3) Results: Morphological studies indicated that w-Pt@AgNPs were cube in shape, decorated by platinum nanodots on the surfaces. Compared to ethanolic extract-synthesized e-Pt@AgNPs, w-Pt@AgNPs exhibited the strongest antioxidant and cytotoxic activity, as data from Annexin V and Dead cell labeling indicated higher induction of apoptosis. Despite the high proportion of early apoptotic cells, the w-Pt@AgNPs triggered a decrease in G1/G0 cell cycle phase distribution, thereby initiating a G2/M arrest. (4) Conclusions: By enhancing the antioxidant properties and promoting apoptosis, w-Pt@AgNPs exhibited remarkable potential for improved cancer therapy outcomes.

Ecotoxicological Effects of Bimetallic PdNi/MWCNT and PdCu/MWCNT Nanoparticles onto DNA Damage and Oxidative Stress in Earthworms

Bimetallic nanoparticles are synthesized using two different metal elements and used recently in many fields. However, limited studies related to the ecotoxic effects of nanoparticles available in the literature. The purpose of this study is to synthesize and characterize bimetallic PdCu/MWCNT and PdNi/MWCNT NPs and investigate their ecotoxic effects on earthworms. For this purpose, we injected approximately 20 µL of various concentrations of bimetallic PdCu/MWCNT and PdNi/MWCNT NPs (1, 10, 100, 1000, and 2000 mg/L) into the coelomic space of earthworms. We evaluated survival rate, malformations, reactive oxygen species (ROS) level, 8-OHdG content, and histopathological changes in earthworms at the 48th hour after exposure. PdCu/MWCNT and PdNi/MWCNT NPs were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) pattern, and Raman-scattering spectroscopy. Toxicological examinations showed that PdCu/MWCNT NPs reduced the survival rate of earthworms (2000 mg/L, 84%) and caused various malformations (various lesions, thinning, swelling, and rupture), but nonsignificant effects of survival rate and malformations were observed in earthworms using PdNi/MWCNT NPs. The histopathological examinations of earthworm tissues exposed with PdNi/MWCNT determined that tissues in all treatment groups had a normal histological appearance. However, at a concentration of 2000 mg/L of PdCu/MWCNT NPs, atrophy in the longitudinal muscle layer and less degenerative cells in the epidermis layer were observed in earthworm tissues. It was determined that PdNi/MWCNT and PdCu/MWCNT NPs caused significant increases in ROS levels and 8-OHdG activity in earthworm tissues after 48 h. Finally, our results demonstrated that the toxicity of PdNi/MWCNT NPs was detected to be lower than PdCu/MWCNT NPs. However, both nanoparticles may pose a toxicological risk at high concentrations (1000 and 2000 mg/L). These findings will provide valuable information to studies on the use of PdNi/MWCNT NPs in wastewater treatment systems, industrial and medical fields, which have been determined to have less ecotoxicological risk.

Nanomaterials for application in wound Healing: current state-of-the-art and future perspectives

Nanoparticles are the gateway to the new era in drug delivery of biocompatible agents. Several products have emerged from nanomaterials in quest of developing practical wound healing dressings that are nonantigenic, antishear stress, and gas-exchange permeable. Numerous studies have isolated and characterised various wound healing nanomaterials and nanoproducts. The electrospinning of natural and synthetic materials produces fine products that can be mixed with other wound healing medications and herbs. Various produced nanomaterials are highly influential in wound healing experimental models and can be used commercially as well. This article reviewed the current state-of-the-art and briefly specified the future concerns regarding the different systems of nanomaterials in wound healing (i.e., inorganic nanomaterials, organic and hybrid nanomaterials, and nanofibers). This review may be a comprehensive guidance to help health care professionals identify the proper wound healing materials to avoid the usual wound complications.

Bimetallic Nanomaterials-Based Electrochemical Biosensor Platforms for Clinical Applications

Diabetes is a foremost health issue that results in ~4 million deaths every year and ~170 million people suffering globally. Though there is no treatment for diabetes yet, the blood glucose level of diabetic patients should be checked closely to avoid further problems. Screening glucose in blood has become a vital requirement, and thus the fabrication of advanced and sensitive blood sugar detection methodologies for clinical analysis and individual care. Bimetallic nanoparticles (BMNPs) are nanosized structures that are of rising interest in many clinical applications. Although their fabrication shares characteristics with physicochemical methodologies for the synthesis of corresponding mono-metallic counterparts, they can display several interesting new properties and applications as a significance of the synergetic effect between their two components. These applications can be as diverse as clinical diagnostics, anti-bacterial/anti-cancer treatments or biological imaging analyses, and drug delivery. However, the exploitation of BMNPs in such fields has received a small amount of attention predominantly due to the vital lack of understanding and concerns mainly on the usage of other nanostructured materials, such as stability and bio-degradability over extended-time, ability to form clusters, chemical reactivity, and biocompatibility. In this review article, a close look at bimetallic nanomaterial based glucose biosensing approaches is discussed, concentrating on their clinical applications as detection of glucose in various real sample sources, showing substantial development of their features related to corresponding monometallic counterparts and other existing used nanomaterials for clinical applications.

Liposomes: Structure, Biomedical Applications, and Stability Parameters With Emphasis on Cholesterol

Liposomes are essentially a subtype of nanoparticles comprising a hydrophobic tail and a hydrophilic head constituting a phospholipid membrane. The spherical or multilayered spherical structures of liposomes are highly rich in lipid contents with numerous criteria for their classification, including structural features, structural parameters, and size, synthesis methods, preparation, and drug loading. Despite various liposomal applications, such as drug, vaccine/gene delivery, biosensors fabrication, diagnosis, and food products applications, their use encounters many limitations due to physico-chemical instability as their stability is vigorously affected by the constituting ingredients wherein cholesterol performs a vital role in the stability of the liposomal membrane. It has well established that cholesterol exerts its impact by controlling fluidity, permeability, membrane strength, elasticity and stiffness, transition temperature (Tm), drug retention, phospholipid packing, and plasma stability. Although the undetermined optimum amount of cholesterol for preparing a stable and controlled release vehicle has been the downside, but researchers are still focused on cholesterol as a promising material for the stability of liposomes necessitating explanation for the stability promotion of liposomes. Herein, the prior art pertaining to the liposomal appliances, especially for drug delivery in cancer therapy, and their stability emphasizing the roles of cholesterol.

Recent Advances in Synthesis, Medical Applications and Challenges for Gold-Coated Iron Oxide: Comprehensive Study

Combining iron oxide nanoparticles (Fe3O4 NPs) and gold nanoparticles (Au NPs) in one nanostructure is a promising technique for various applications. Fe3O4 NPs have special supermagnetic attributes that allow them to be applied in different areas, and Au NPs stand out in biomaterials due to their oxidation resistance, chemical stability, and unique optical properties. Recent studies have generally defined the physicochemical properties of nanostructures without concentrating on a particular formation strategy. This detailed review provides a summary of the latest research on the formation strategy and applications of Fe3O4@Au. The diverse methods of synthesis of Fe3O4@Au NPs with different basic organic and inorganic improvements are introduced. The role and applicability of Au coating on the surface of Fe3O4 NPs schemes were explored. The 40 most relevant publications were identified and reviewed. The versatility of combining Fe3O4@Au NPs as an option for medical application is proven in catalysis, hyperthermia, biomedical imaging, drug delivery and protein separation.

Facile synthesis of silver/gold alloy nanoparticles for ultra-sensitive rhodamine B detection

The synthesis of Ag/Au nanoparticles (NPs) in a controlled manner has been a challenge for a long time. The aim of this report is to present a systematic study on the fabrication, characterization of Ag/Au alloy NP-based surface-enhanced Raman spectroscopy (SERS) substrates. Silver (Ag) and gold (Au) colloidal NPs were prepared by chemical reduction route of the corresponding metal salts by trisodium citrate (TSC). Ag/Au alloy nanoparticles with varying molar fractions are prepared in aqueous solution by the simultaneous reduction of AgNO3 and HAuCl4 by TSC. The composition of Ag and Au in the alloy samples was controlled by tuning the molar ratio of Ag+/Au3+ in the mixture solution. The morphologies of the different products were characterized by TEM, and the size of obtained samples was in the range of 40 to 60 nm. The resulting samples were denoted as AgNPs, AuNPs, Ag3Au, AgAu, and AgAu3 NPs. In order to compare the optical property of the Ag/Au alloy and Ag/Au mixture, we mixed the pure Ag and Au NPs with different ratios to obtain the aggregated nanoparticles. Ag/Au alloy NPs were demonstrated as an ultrasensitive SERS substrate for the detection of rhodamine B (RhB) molecules. The concentration of RhB ranged from 10-11 to 10-5 M. The effect of the Au content on the optical and SERS properties of the Ag/Au alloys was studied. The obtained results show that the Au content in the Ag/Au alloys play an important role in the physical properties of Ag/Au alloy NPs. The SERS spectra of RhB from the as-prepared Ag/Au alloy NP substrates indicated the superior enhancement with high reproducibility and sensitivity compared to those of Ag or Au samples. Interestingly, the highest SERS activity was achieved for the Ag3Au sample with an enhancement factor larger than 1010 for 10-11 M RhB and a limit of detection (LOD) at 10-11 M, as well as good long-term stability after storage for 1 year. As far as we know, this is the highest sensitivity record of RhB by SERS detection. Furthermore, the composition-dependent SERS activity was explained in detail. These advantages demonstrated the potential for growing Ag/Au alloy NP-based SERS substrates in food safety and bioanalysis.

Nano-Magnetic NiFe2O4 and Its Photocatalytic Oxidation of Vanillyl Alcohol-Synthesis, Characterization, and Application in the Valorization of Lignin

Here, we report on a phyto-mediated bimetallic (NiFe₂O₄) preparation using a Boswellia carterii extract, which was characterized by XRD, FT-IR, TGA, electron microscopy, magnetic spectroscopy, and Mössbauer spectroscopy measurements. The prepared nano-catalysts were tested for oxidation of lignin monomer molecules-vanillyl alcohol and cinnamyl alcohol. In comparison with previously reported methods, the nano NiFe₂O₄ catalysts showed high photocatalytic activity and selectivity, under visible light irradiation with a nitroxy radical initiator (2,2,6,6-tetramethylpiperidinyloxy or 2,2,6,6-tetramethylpiperidine 1-oxyl; TEMPO) at room temperature and aerobic conditions. The multifold advantages of the catalyst both in terms of reduced catalyst loading and ambient temperature conditions were manifested by higher conversion of the starting material.

Mesoporous gold-silver alloy films towards amplification-free ultra-sensitive microRNA detection

Herein, we report the preparation of mesoporous gold (Au)-silver (Ag) alloy films through the electrochemical micelle assembly process and their applications as microRNA (miRNA) sensors. Following electrochemical deposition and subsequent removal of the templates, the polymeric micelles can create uniformly sized mesoporous architectures with high surface areas. The resulting mesoporous Au-Ag alloy films show high current densities (electrocatalytic activities) towards the redox reaction between potassium ferrocyanide and potassium ferricyanide. Following magnetic isolation and purification, the target miRNA is adsorbed directly on the mesoporous Au-Ag film. Electrochemical detection is then enabled by differential pulse voltammetry (DPV) using the [Fe(CN)6]3-/4- redox system (the faradaic current for the miRNA-adsorbed Au-Ag film decreases compared to the bare film). The films demonstrate great advantages towards miRNA sensing platforms to enhance the detection limit down to attomolar levels of miR-21 (limit of detection (LOD) = 100 aM, s/n = 3). The developed enzymatic amplification-free miniaturized analytical sensor has promising potential for RNA-based diagnosis of diseases.

Versatile and robust synthesis process for the fine control of the chemical composition and core-crystallinity of spherical core-shell Au@Ag nanoparticles

Au nanoparticles (NPs) characterized by distinct surface chemistry (including dodecanethiol or oleylamine as capping agent), different sizes (∼5 and ∼10 nm) and crystallinities (polycrystalline or single crystalline), were chosen as seeds to demonstrate the versatility and robustness of our two-step core-shell Au@Ag NP synthesis process. The central component of this strategy is to solubilize the shell precursor (AgNO₃) in oleylamine and to induce the growth of the shell on selected seeds under heating. The shell thickness is thus controlled by the temperature, the annealing time, the (shell precursor)/(seed) concentration ratio, seed size and crystallinity. The shell thickness is thus shown to increase with the reactant concentration and to grow faster on polycrystalline seeds. The crystalline structure and chemical composition were characterized by HRTEM, STEM-HAADF, EELS and Raman spectroscopy. The plasmonic response of Au@Ag core-shell NPs as a function of core size and shell thickness was assessed by spectrophotometry and simulated by calculations based on the discrete dipole approximation (DDA) method. Finally, the nearly monodisperse core-shell Au@Ag NPs were shown to form micrometer-scale facetted 3D fcc-ordered superlattices (SLs) after solvent evaporation and deposition on a solid substrate. These SLs are promising candidates for applications as a tunable surface-enhanced Raman scattering platform.

Green fabrication of hydrogel-immobilized Au@Ag nanoparticles using tannic acid and their application in catalysis

A catalytic hydrogel was obtained by immobilizing tannic acid reduced and stabilized Au@AgNPs on a PVA/TA hydrogel, used as the good solid catalyst for the degradation of environmental pollutants such as Congo red, 4-nitrophenol, -etc.

Laboratory analysis of Au-Pd bimetallic nanoparticles synthesized with Citrus limon leaf extract and its efficacy on mosquito larvae and non-target organisms

The current study provides novel results on the synthesis of bimetallic nanoparticles (BNPs) of gold and palladium (Au–Pd) with an eco-friendly and non-toxic aqueous leaf extract of plant Citrus limon. The BNPs were characterized and toxicity bioassay was examined on the larvae of the pathogen vectors such as Anopheles stephensi and Aedes aegypti mosquitoes. The predation efficiency test was evaluated on the invertebrate non-target organisms such as natural predatory nymphs of dragonfly and damselfly. The results of material characterization using UV VIS spectroscopy confirmed the synthesis of Au–Pd BNPs with the appearance of the SPR bands. FT-IR spectroscopy indicates the presence of functional groups containing high amounts of nitro compounds and amines on the surface of BNPs. TEM result shows the presence of spherical polydisperse Au–Pd BNPs in the sample. The XRD pattern displayed the semi-crystalline nature and the changes in the hydrodynamic size and surface potential was determined for the sample at 0 h, 24 h, 48 h, and 72 h of synthesis through DLS and ZP analysis. Au–Pd BNPs Bioassay provided the effective lethal concentrations (LC₅₀) against the I–IV instar larvae of An. stephensi and Ae. aegypti after 24 h, 48 h, and 72 h of exposure. The LC₅₀ obtained from the larvicidal bioassay was used to test its effect on the predation efficiency of the selected nymphs which showed increased predation from 40 to 48 h of exposure as compared to the negative control. Hereby, we conclude that Au–Pd BNPs bioassay shows toxic mosquito larvicidal activity at the selected concentration with no lethal effect on the predation efficiency of the selected stage of the predatory non-target aquatic invertebrate insects.

Therapeutic nanodendrites: current applications and prospects

Multidisciplinary efforts in the field of nanomedicine for cancer therapy to provide solutions to common limitations of traditional drug administration such as poor bioaccumulation, hydrophobicity, and nonspecific biodistribution and targeting have registered very promising progress thus far. Currently, a new class of metal nanostructures possessing a unique dendritic-shaped morphology has been designed for improved therapeutic efficiency. Branched metal nanoparticles or metal nanodendrites are credited to present promising characteristics for biomedical applications owing to their unique physicochemical, optical, and electronic properties. Nanodendrites can enhance the loading efficiency of bioactive molecules due to their three-dimensional (3D) high surface area and can selectively deliver their cargo to tumor cells using their stimuli-responsive properties. With the ability to accumulate sufficiently within cells, nanodendrites can overcome the detection and clearance by glycoproteins. Moreover, active targeting ligands such as antibodies and proteins can as well be attached to these therapeutic nanodendrites to enhance specific tumor targeting, thereby presenting a multifunctional nanoplatform with tunable strategies. This mini-review focuses on recent developments in the understanding of metallic nanodendrite synthesis, formation mechanism, and their therapeutic capabilities for next-generation cancer therapy. Finally, the challenges and future opportunities of these fascinating materials to facilitate extensive research endeavors towards the design and application were discussed.

Synthesis and Characterization of Novel Phyto-Mediated Catalyst, and Its Application for a Selective Oxidation of (VAL) into Vanillin under Visible Light

Here, we report an efficient and highly selective oxidation of lignin model substrate using phyto-mediated ZnFe2O4 nanoparticle using Boswellia carterii extract. The nanocatalyst with an average size of 8 nm showed excellent photocatalytic activity of the synthesized carbonyl containing products under visible light irradiation. The catalytic activity and selectivity towards oxidation of vanillyl alcohol to vanillin with selectivity up to 99% at conversion over 98% and turn-over frequency values up to 1600 h−1 were obtained in the presence of H2O2 and base. The cubic spinel nano-ZnFe2O4 catalyst was characterized by powder-XRD, FESEM, HR-TEM and Mössbauer analysis. The demonstrated catalyst was robust and stable under the reaction conditions. Furthermore, it was easy to be separated from the reaction mixture and be reused for subsequent reactions up to 5 times without significant reactivity or selectivity loss.

Synthesis, Properties, and Biological Applications of Metallic Alloy Nanoparticles

Metallic alloy nanoparticles are synthesized by combining two or more different metals. Bimetallic or trimetallic nanoparticles are considered more effective than monometallic nanoparticles because of their synergistic characteristics. In this review, we outline the structure, synthesis method, properties, and biological applications of metallic alloy nanoparticles based on their plasmonic, catalytic, and magnetic characteristics.

Bimetallic Catalysts for Volatile Organic Compound Oxidation

In recent years, the impending necessity to improve the quality of outdoor and indoor air has produced a constant increase of investigations in the methodologies to remove and/or to decrease the emission of volatile organic compounds (VOCs). Among the various strategies for VOC elimination, catalytic oxidation and recently photocatalytic oxidation are regarded as some of the most promising technologies for VOC total oxidation from urban and industrial waste streams. This work is focused on bimetallic supported catalysts, investigating systematically the progress and developments in the design of these materials. In particular, we highlight their advantages compared to those of their monometallic counterparts in terms of catalytic performance and physicochemical properties (catalytic stability and reusability). The formation of a synergistic effect between the two metals is the key feature of these particular catalysts. This review examines the state-of-the-art of a peculiar sector (the bimetallic systems) belonging to a wide area (i.e., the several catalysts used for VOC removal) with the aim to contribute to further increase the knowledge of the catalytic materials for VOC removal, stressing the promising potential applications of the bimetallic catalysts in the air purification.

Antibacterial Effects of Bimetallic Clusters Incorporated in Amorphous Carbon for Stent Application

The purpose of this work is the development of Ag/a:C and Ag-Au/a:C coatings for ureteral stents, to provide them with antimicrobial characteristics. Silver was selected because of its well-known antibacterial properties, while gold was included to assess its capacity to accelerate the silver ion release forming a galvanic couple between Au and Ag. Thus, the metallic (Ag) and bimetallic clusters (Ag-Au) were produced by three different configurations: (i) unbalanced magnetron sputtering (conventional sputtering), (ii) plasma gas condensation process, and by (iii) a combination between both previous approaches. Coatings with Ag-Au bimetallic clusters were characterized by transmission electron microscopy (TEM) in order to study the arrangement (alloy, core-shell, and galvanic couple) of these particles in the carbon matrix. Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used to quantify the Ag ions released through artificial urine from the different coatings deposited on thermoplastic polyurethane tape (one of the materials used in the manufacture of the ureteral stent ). Then, the antibacterial and cytotoxicity properties of Ag and Ag-Au/a:C coatings were evaluated. TEM shows that a biphasic structure was not detected, thus not allowing to anticipate the establishment of a galvanic couple. The ICP-OES results demonstrate that the silver ionization is mainly a function of the amount of silver incorporated in the amorphous carbon (a:C) matrix, and the formation of a bimetallic alloy has a detrimental effect on release of the silver ions. The antibacterial activity was regulated by the silver ionization mechanisms because the coatings with higher Ag release had a higher antibacterial activity.

Noble Metals Based Bimetallic and Trimetallic Nanoparticles: Controlled Synthesis, Antimicrobial and Anticancer Applications

Noble bimetallic and trimetallic nanoparticles (NBT-NPs) have superior biomedical applications as compared to their monometallic counterparts. The performance of these nanomaterials depends on their composition, shape and size. Hence, the controlled-synthesis of these nanomaterials is a hot area of research. Till date, no review article in the literature accounts regarding the controlled-synthesis and biomedical applications related to morphology, optimum composition, biocompatibility and versatile chemistry of NBT-NPs. Taking this into contemplation, an effort was made to provide a clear insight into the morphology-controlled synthesis and size/shape-dependent anticancer and bactericidal applications of NBT-NPs. Chemical reduction method for the controlled-synthesis of NBT-NPs is reviewed critically. Furthermore, the potential role of various reaction parameters such as time, reducing agents, stabilizing/capping agents, nature/concentration of precursors, temperature and pH in the shape/size-controlled synthesis of these nanomaterials are discussed. In the second part of this article, anticancer and bactericidal applications of the NBT-NPs are reviewed and the influences of optimum composition, size, surface structure, versatile chemistry and synergism are studied. Finally, the current challenges in the controlled-synthesis and biomedical applications of these nanomaterials, and prospects to resolve related issues are discussed. HighlightsChemical reduction method for the synthesis of NBT-NPs is reviewed.The influences of parameters on the control synthesis of NBT-NPs are discussed.Antibacterial and anticancer applications and cytotoxicity of NBT-NPs are reviewed.Possible solutions for the key challenges are discussed.Outlooks about the synthesis and biomedical applications of NBT-NPs are discussed.

Structure Differentiation of Hydrophilic Brass Nanoparticles Using a Polyol Toolbox

Nano-brasses are emerging as a new class of composition-dependent applicable materials. It remains a challenge to synthesize hydrophilic brass nanoparticles (NPs) and further exploit them for promising bio-applications. Based on red/ox potential of polyol and nitrate salts precursors, a series of hydrophilic brass formulations of different nanoarchitectures was prepared and characterized. Self-assembly synthesis was performed in the presence of triethylene glycol (TrEG) and nitrate precursors Cu(NO₃)₂·3H₂O and Zn(NO₃)₂·6H₂O in an autoclave system, at different temperatures, conventional or microwave-assisted heating, while a range of precursor ratios was investigated. NPs were thoroughly characterized via X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmition electron microscopy (TEM), Fourier-transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS), and ζ-potential to determine the crystal structure, composition, morphology, size, state of polyol coating, and aqueous colloidal stability. Distinct bimetallic α-brasses and γ-brasses, α-Cu₄₀Zn₂₅/γ-Cu₁₁Zn₂₄, α-Cu₆₃Zn₃₇, α-Cu₄₇Zn₁₀/γ-Cu₁₉Zn₂₄, and hierarchical core/shell structures, α-Cu₅₉Zn₃₀@(ZnO)₁₁, Cu₃₅Zn₁₆@(ZnO)₄₉, α-Cu₃₇Zn₁₈@(ZnO)₄₅, Cu@Zinc oxalate, were produced by each synthetic protocol as stoichiometric, copper-rich, and/or zinc-rich nanomaterials. TEM sizes were estimated at 20–40 nm for pure bimetallic particles and at 45–70 nm for hierarchical core/shell structures. Crystallite sizes for the bimetallic nanocrystals were found ca. 30–45 nm, while in the case of the core-shell structures, smaller values around 15–20 nm were calculated for the ZnO shells. Oxidation and/or fragmentation of TrEG was unveiled and attributed to the different fabrication routes and formation mechanisms. All NPs were hydrophilic with 20–30% w/w of polyol coating, non-ionic colloidal stabilization (−5 mV < ζ-potential < −13 mV) and relatively small hydrodynamic sizes (<250 nm). The polyol toolbox proved effective in tailoring the structure and composition of hydrophilic brass NPs while keeping the crystallite and hydrodynamic sizes fixed.

Nanoparticle-mediated approaches for Alzheimer's disease pathogenesis, diagnosis, and therapeutics

Alzheimer's disease (AD) is an irreversible and progressive neurodegenerative disorder manifested by memory loss and cognitive impairment. Deposition of the amyloid β plaques has been identified as the most common AD pathology; however, the excessive accumulation of phosphorylated or total tau proteins, reactive oxygen species, and higher acetylcholinesterase activity are also strongly associated with Alzheimer's dementia. Several therapeutic approaches targeting these pathogenic mechanisms have failed in clinical or preclinical trials, partly due to the limited bioavailability, poor cell, and blood-brain barrier penetration, and low drug half-life of current regimens. The nanoparticles (NPs)-mediated drug delivery systems improve drug solubility and bioavailability, thus renders as superior alternatives. Moreover, NPs-mediated approaches facilitate multiple drug loading and targeted drug delivery, thereby increasing drug efficacy. However, certain NPs can cause acute toxicity damaging cellular and tissue architecture, therefore, NP material should be carefully selected. In this review, we summarize the recent NPs-mediated studies that exploit various pathologic mechanisms of AD by labeling, identifying, and treating the affected brain pathologies. The disadvantages of the select NP-based deliveries and the future aspects will also be discussed.

Phyto-Nanocatalysts: Green Synthesis, Characterization, and Applications

Catalysis represents the cornerstone of chemistry, since catalytic processes are ubiquitous in almost all chemical processes developed for obtaining consumer goods. Nanocatalysis represents nowadays an innovative approach to obtain better properties for the catalysts: stable activity, good selectivity, easy to recover, and the possibility to be reused. Over the last few years, for the obtaining of new catalysts, classical methods—based on potential hazardous reagents—have been replaced with new methods emerged by replacing those reagents with plant extracts obtained in different conditions. Due to being diversified in morphology and chemical composition, these materials have different properties and applications, representing a promising area of research. In this context, the present review focuses on the metallic nanocatalysts’ importance, different methods of synthesis with emphasis to the natural compounds used as support, characterization techniques, parameters involved in tailoring the composition, size and shape of nanoparticles and applications in catalysis. This review presents some examples of green nanocatalysts, grouped considering their nature (mono- and bi-metallic nanoparticles, metallic oxides, sulfides, chlorides, and other complex catalysts).

Assessing the effectiveness of green synthetized silver nanoparticles with Cryptocarya alba extracts for remotion of the organic pollutant methylene blue dye

In the present work, silver nanoparticles (AgNPs) synthetized with Cryptocarya alba (Peumo) leaf extract were studied. The fabrication method was fast, low cost, and eco-friendly, and the final properties of AgNPs were determined by experimental parameters, such as AgNO₃ and Peumo extract concentrations used. Setting suitable experimental conditions, crystalline AgNPs with apparent spherical forms and average diameter around 3.5 nm were obtained. In addition, the capability of synthesized Peumo-AgNPs to remove methylene blue dye (MB) in aqueous solution as well as their catalytic effectiveness was also investigated. The results showed that green synthesized AgNPs can remove fast and effectively the MB dye from aqueous medium by itself, but better results were found acting like catalyst by using sodium borohydride (NaBH₄) in the reaction. In addition, this green nanomaterial can be recycling several times maintaining initial properties for removal of MB. Thus, AgNPs synthetized with Peumo leaf extracts could be an excellent catalyst candidate for degradation of blue methylene dye in chemical industries.

Advances of nanosystems containing cyclodextrins and their applications in pharmaceuticals

For many years, researchers have worked with supramolecular structures involving inclusion complexes with cyclodextrins. These studies have resulted in new commercially available drugs which have been of great benefit. More recently, studies using nanoparticles, including nanosystems containing cyclodextrins, have become a focus of academic research due to the versatility of the systems and their remarkable therapeutic potential. This review focuses on studies published between 2002 and 2018 involving nanosystems containing cyclodextrins. We consider the type of nanosystems, their importance in a health context, the physicochemical techniques used to show the quality of these systems and their potential for the development of novel pharmaceutical formulations. These have been developed in recent studies which have mainly been focusing on basic science with no clinical trials as yet being performed. This is important to note because it means that the studies do not include any toxicity tests. Despite this limitation, the characterization assays performed suggest that these new formulations may have therapeutic potential. However, more research is required to assess the efficacy and safety of these nanosystems.

Biosynthesis of bimetallic and core-shell nanoparticles: their biomedical applications - a review

Recently, researchers succeeded in designing and manufacturing a new class of nanoparticles (NPs) called hybrid NPs. Among hybrid NPs, bimetallic and core-shell NPs were a revolutionary step in NPs science. A large number of green physiochemical and methods for nanostructures synthesis have been published. Eventually, physiochemical methods are either expensive or require the use of chemical compounds for the synthesis of bimetallic and core-shell nanostructures. The main challenges that scientists are facing are making the process cheaper, facile and eco-friendly efficient synthesis process. Green synthesis (biosynthesis) refers to the use of bio-resources (such as bacteria, fungi, plants or their derivatives) for the synthesis of nanostructures. The popularity of the green synthesis of nanostructures is due to their environmental friendliness and no usage of toxic materials, environmental friendliness for the synthesis or stability of nanostructure. Bimetallic and core-shell NPs have many biomedical applications such as removing heavy metals, parasitology, molecular and microbial sensor, gene carrier, single bacterial detection, oligonucleotide detection and so on. The purpose of this study is to discuss briefly the biosynthesised bimetallic and core-shell NPs, their biomedical applications.

Tunable Surface Plasmon Resonance-Based Remote Actuation of Bimetallic Core-Shell Nanoparticle-Coated Stimuli Responsive Polymer for Switchable Chemo-Photothermal Synergistic Cancer Therapy

New dual light/temperature-responsive nanocarriers were synthesized using bimetallic plasmonic Au-Ag and Ag-Au nanoparticles (NPs) as cores of vehicles which subsequently functionalized with an upper critical solubility temperature-based poly acrylamide-co-acrylonitrile using reversible addition-fragmentation chain transfer for spatiotemporally controlled chemo-photothermal synergistic cancer therapy. The bimetallic cores were assigned to sense wavelengths close to the localized surface plasmon resonance of monometallic NP shell to produce heat which not only can increase the surrounding temperature over the upper critical solubility temperature of polymer to open its valves and promote drug diffusion but also can kill cancerous cells through photothermal effects with increase in environment temperature by nearly 18°C after about 5 min radiation. The bimetallic NPs were shown good reusability even after 5 heating/cooling cycles, and the efficiency of both photothermal/chemotherapic procedures can be modulated by manipulating carrier's concentration and radiation time. In addition, the cytotoxicity of drug-free nanocarriers on normal L929 fibroblast and letrozole-loaded nanocarriers on MDAMB 231 breast-cancer cell lines were investigated in the absence/presence of laser radiation. Finally, the prepared nanocomposites were exhibited switchable on/off drug release in 2 buffered solutions (pH 5.5 and 7.4) with light actuation. The results revealed that the prepared nanocarriers can be served as efficient delivery platforms for remote-control chemophotothermal synergistic cancer therapy.

The tuning of the plasmon resonance of the metal nanoparticles in terms of the SERS effect

The Surface-enhanced Raman spectroscopy is the essential tool for various levels of the molecular studies. In order to become widely used as a fast analytical tool, the enhancing structures such as the nanoparticles have to be simple, inexpensive, and offer good flexibility in enhancing properties and the spectral range. In this paper, we investigated the plasmonic properties of the metal nanoparticles, to which the molecules of interest can be adsorbed, forming the bionanocomplexes. Here, for the first time, we provided the collection of the results gathered in one article, which can serve as the basis or guidance for designing the SERS studies on different bionanocomplexes, various nanoparticle structures, sizes, and excitation wavelengths. The presented plasmonic properties describe the spectral position of the plasmonic resonances as results of their size and structure. The electric field enhancement as a key contributor to the SERS effect is given as well. We considered silver and gold nanoparticles and their variations. Gold is one of the best choice, due to its relevant surface properties, however, suffers from the plasmonic activity and rather static spectral position of the plasmonic resonances. Therefore, one of the main purposes was to show the effective resonance tuning using simple and less expensive geometries. We showed the possibility to adjust the plasmonic resonances with the excitation wavelengths from the blue region to the near infrared region of lasers most commonly used for Raman spectroscopy. The presented studies indicated the high potential of the core-shell structures for this kind of applications.

Nanozyme-Mediated Dual Immunoassay Integrated with Smartphone for Use in Simultaneous Detection of Pathogens

Nanozymes are an excellent class of optical reporters for the development of sensitive biosensors for widespread applications. In this study, mesoporous core-shell palladium@platinum (Pd@Pt) nanoparticles were synthesized and then applied as signal amplifier in a dual lateral flow immunoassay (LFIA) and integrated with a smartphone-based device for use in simultaneous detection of Salmonella Enteritidis and Escherichia coli O157:H7. After optimization, the limit of detections were calculated to be ∼20 cfu/mL for S. Enteritidis and ∼34 cfu/mL for E. coli O157:H7, respectively. The greatly improved sensitivity was contributed by the peroxidase-like catalytic activity of the Pd@Pt nanoparticles for signal enhancement and the parallel design of dual detection for eliminating the cross-interference. The estimated recoveries of the dual LFIA range from 91.44 to 117.00%, which indicated that the developed method is capable of detecting live bacteria in food samples. This approach provides an attractive platform for S. Enteritidis and E. coli O157:H7 detection using a smartphone-based device as the sole piece of equipment, indicating great promise for foodborne pathogen analysis or in-field food safety tracking.