Methods of Gold and Silver Nanoparticles Preparation

On the influence of metal nanoparticle and π-system sizes in the stability of noncovalent adducts: a theoretical study

Herein we have computationally evaluated the relationship between Ag and Au nanoparticle (Ag/AuNP) size and π-surface extension in the formation of noncovalent complexes at the PBE0-D3/def2-TZVP level of theory. The NP-π interaction is known in supramolecular chemistry as a Regium-π bond (Rg-π), and differentiates from classical coordination bonds in strength and type of metal orbitals involved. In this study, the Rg-π complexes involved small Ag/AuNPs composed by 1 to 5 atoms and benzene, naphthalene and anthracene as π-systems, being characterized using several molecular modeling tools, including molecular electrostatic potential (MEP) calculations, energy decomposition analysis (EDA), quantum theory of atoms in molecules (QTAIM), non covalent interaction plot (NCIplot) and natural bonding orbital (NBO) methodologies. We believe the results reported herein will be useful for those scientists working in catalysis, molecular recognition and materials science fields, where structural-energetic relationships of weak interactions are crucial to achieve product selectivity, a particular molecular recognition mode or a specific molecular assembly.

Stability and biological response of PEGylated gold nanoparticles

Stability and cytotoxicity of PEGylated Au NPs is crucial for biomedical application. In this study, we have focused on thermal stability of PEGylated Au NPs at 4 and 37 °C and after sterilization in autoclave. Gold nanoparticles were prepared by direct sputtering of gold into PEG and PEG-NH2. Transmission electron microscopy revealed that NPs exhibit a spherical shape with average dimensions 3.8 nm for both AuNP_PEG and AuNP_PEG-NH2. The single LSPR band at wavelength of 509 nm also confirmed presence of spherical Au NPs in both cases. Moreover, according to UV-Vis spectra, the Au NPs were overall stable during aging or thermal stressing and even after sterilization in autoclave. Based on gel electrophoresis results, the higher density of functionalizing ligands and the higher stability is assumed on AuNP_PEG-NH2. Changes in concentration of gold did not occur after thermal stress or with aging. pH values have to be adjusted to be suitable for bioapplications - original pH values are either too alkaline (AuNP_PEG-NH2, pH 10) or too acidic (AuNP_PEG, pH 5). Cytotoxicity was tested on human osteoblasts and fibroblasts. Overall, both Au NPs have shown good cytocompatibility either freshly prepared or even after Au NPs' sterilization in the autoclave. Prepared Au NP dispersions were also examined for their antiviral activity, however no significant effect was observed. We have synthesized highly stable, non-cytotoxic PEGylated Au NPs, which are ready for preclinical testing.

Tau- and α-synuclein-targeted gold nanoparticles: applications, opportunities, and future outlooks in the diagnosis and therapy of neurodegenerative diseases

The use of nanomaterials in medicine offers multiple opportunities to address neurodegenerative disorders such as Alzheimer's and Parkinson's disease. These diseases are a significant burden for society and the health system, affecting millions of people worldwide without sensitive and selective diagnostic methodologies or effective treatments to stop their progression. In this sense, the use of gold nanoparticles is a promising tool due to their unique properties at the nanometric level. They can be functionalized with specific molecules to selectively target pathological proteins such as Tau and α-synuclein for Alzheimer's and Parkinson's disease, respectively. Additionally, these proteins are used as diagnostic biomarkers, wherein gold nanoparticles play a key role in enhancing their signal, even at the low concentrations present in biological samples such as blood or cerebrospinal fluid, thus enabling an early and accurate diagnosis. On the other hand, gold nanoparticles act as drug delivery platforms, bringing therapeutic agents directly into the brain, improving treatment efficiency and precision, and reducing side effects in healthy tissues. However, despite the exciting potential of gold nanoparticles, it is crucial to address the challenges and issues associated with their use in the medical field before they can be widely applied in clinical settings. It is critical to ensure the safety and biocompatibility of these nanomaterials in the context of the central nervous system. Therefore, rigorous preclinical and clinical studies are needed to assess the efficacy and feasibility of these strategies in patients. Since there is scarce and sometimes contradictory literature about their use in this context, the main aim of this review is to discuss and analyze the current state-of-the-art of gold nanoparticles in relation to delivery, diagnosis, and therapy for Alzheimer's and Parkinson's disease, as well as recent research about their use in preclinical, clinical, and emerging research areas.

A Step Forward for the Treatment of Localized Prostate Cancer Using Gold Nanoparticles Combined with Laser Irradiation

Prostate cancer (PCA) is the second most common cancer diagnosis in men and the fifth leading cause of death worldwide. The conventional treatments available are beneficial to only a few patients and, in those, some present adverse side effects that eventually affect the quality of life of most patients. Thus, there is an urgent need for effective, less invasive and targeted specific treatments for PCA. Photothermal therapy (PTT) is a minimally invasive therapy that provides a localized effect for tumour cell ablation by activating photothermal agents (PTA) that mediate the conversion of the light beam's energy into heat at the site. As tumours are unable to easily dissipate heat, they become more susceptible to temperature increases. In the PTT field, gold nanoparticles (AuNPs) have been attracting interest as PTA. The aim of this study was to formulate AuNPs capable of remaining retained in the tumour and subsequently generating heat at the tumour site. AuNPs were synthesized and characterized in terms of size, polydispersity index (PdI), zeta potential (ZP), morphology and the surface plasmon resonance (SPR). The safety of AuNPs and their efficacy were assessed using in vitro models. A preliminary in vivo safety assessment of AuNPs with a mean size lower than 200 nm was confirmed. The morphology was spherical-like and the SPR band showed good absorbance at the laser wavelength. Without laser, AuNPs proved to be safe both in vitro (>70% viability) and in vivo. In addition, with laser irradiation, they proved to be relatively effective in PCA cells. Overall, the formulation appears to be promising for use in PTT.

Rational approach to design gold nanoparticles for photothermal therapy: the effect of gold salt on physicochemical, optical and biological properties

Among the unique characteristics associated to gold nanoparticles (AuNPs) in biomedicine, their ability to convert light energy into heat opens ventures for improved cancer therapeutic options, such as photothermal therapy (PTT). PTT relies on the local hyperthermia of tumor cells upon irradiation with light beams, and the association of AuNPs with radiation within the near infrared (NIR) range constitutes an advantageous strategy to potentially improve PTT efficacy. Herein, it was explored the effect of the gold salt on the AuNPs' physicochemical and optical properties. Mostly spherical-like negatively charged AuNPs with variable sizes and absorbance spectra were obtained. In addition, photothermal features were assessed using in vitro phantom models. The best formulation showed the ability to increase their temperature in aqueous solution up to 19 °C when irradiated with a NIR laser for 20 min. Moreover, scanning transmission electron microscopy confirmed the rearrangement of the gold atoms in a face-centered cubic structure, which further allowed to calculate the photothermal conversion efficiency upon combination of theoretical and experimental data. AuNPs also showed local retention after being locally administered in in vivo models. These last results obtained by computerized tomography allow to consider these AuNPs as promising elements for a PTT system. Moreover, AuNPs showed high potential for PTT by resulting in in vitro cancer cells' viability reductions superior to 70 % once combine with 5 min of NIR irradiation.

A comprehensive review of cancer therapies mediated by conjugated gold nanoparticles with nucleic acid

Nucleic acids provide a promising therapeutic platform by targeting various cell signaling pathways involved in cancer and genetic disorders. However, maintaining optimal stability during delivery limits their utility. Nucleic acid delivery vehicles are generally categorized into biological and synthetic carriers. Regardless of the efficiency of biological vectors, such as viral vectors, issues related to their immunogenicity and carcinogenesis are very important and vital for clinical applications. On the other hand, synthetic vectors such as lipids or polymers, have been widely used for nucleic acid delivery. Despite their transfection efficiency, low storage stability, targeting inefficiency, and tracking limitations are among the limitations of the clinical application of these vectors. In the past decades, gold nanoparticles with unique properties have been shown to be highly efficient mineral vectors for overcoming these obstacles. In this review, we focus on gold nanoparticle-nucleic acid combinations and highlight their use in the treatment of various types of cancers. Furthermore, by stating the biological applications of these structures, we will discuss their clinical applications.

Biochemical Screening, Fabrication of Green Nanoparticles and Its Antimicrobial, and Antioxidant Studies of Endophytic Fungus Phlebia Species

Endophytes are organism dwelling totally dynamic and novel biotopes this makes them able to produce novel biochemicals that may become assets to the future. This study aims at understanding the biochemical components of the endophytic fungus Phlebia sp. synthesis of gold and silver nanoparticles from it, and the antimicrobial as well as antioxidant ability of these green synthesised nanoparticles. Aqueous fungal extract was subjected for HRLCMS analysis which revealed 34 biochemicals within the extract. Silver and gold nanoparticles were also produced from the fungal extract. UV-vis analysis revealed a peak at 450 nm for silver nanoparticle and 550 nm for gold nanoparticles. FESEM analysis confirmed the presence of these nanoparticles with its spherical shape. Both of these nanoparticles were able to produce a conspicuous zone of inhibition in the antimicrobial tests against Escherichia coli, Salmonella paratyphi. For both of the organisms under study, a concentration-dependent expansion of the zone of inhibition was discovered in the nanoparticles. However, with silver nanoparticles, a relatively high zone of inhibition and vulnerability of the organism was discovered. Four in vitro free radical scavenging assays, including the DPPH, Hydroxyl, Superoxide, and Nitric oxide radical scavenging assays, were used for antioxidant analysis. The results of every test demonstrated that green synthesised silver nanoparticles had higher activity than gold nanoparticles. All of the tests showed that silver nanoparticles were more active than gold nanoparticles with the maximum value of 86.254 ± 0.296% being discovered at the greatest concentration of superoxide radical scavenging assay.

Recent advances in nanoantibiotics against multidrug-resistant bacteria

Multidrug-resistant (MDR) bacteria-caused infections have been a major threat to human health. The abuse of conventional antibiotics accelerates the generation of MDR bacteria and makes the situation worse. The emergence of nanomaterials holds great promise for solving this tricky problem due to their multiple antibacterial mechanisms, tunable antibacterial spectra, and low probabilities of inducing drug resistance. In this review, we summarize the mechanism of the generation of drug resistance, and introduce the recently developed nanomaterials for dealing with MDR bacteria via various antibacterial mechanisms. Considering that biosafety and mass production are the major bottlenecks hurdling the commercialization of nanoantibiotics, we introduce the related development in these two aspects. We discuss urgent challenges in this field and future perspectives to promote the development and translation of nanoantibiotics as alternatives against MDR pathogens to traditional antibiotics-based approaches.

Present and future of metal nanoparticles in tumor ablation therapy

Cancer is an important factor affecting the quality of human life as well as causing death. Tumor ablation therapy is a minimally invasive local treatment modality with unique advantages in treating tumors that are difficult to remove surgically. However, due to its physical and chemical characteristics and the limitation of equipment technology, ablation therapy cannot completely kill all tumor tissues and cells at one time; moreover, it inevitably damages some normal tissues in the surrounding area during the ablation process. Therefore, this technology cannot be the first-line treatment for tumors at present. Metal nanoparticles themselves have good thermal and electrical conductivity and unique optical and magnetic properties. The combination of metal nanoparticles with tumor ablation technology, on the one hand, can enhance the killing and inhibiting effect of ablation technology on tumors by expanding the ablation range; on the other hand, the ablation technology changes the physicochemical microenvironment such as temperature, electric field, optics, oxygen content and pH in tumor tissues. It helps to stimulate the degree of local drug release of nanoparticles and increase the local content of anti-tumor drugs, thus forming a synergistic therapeutic effect with tumor ablation. Recent studies have found that some specific ablation methods will stimulate the body's immune response while physically killing tumor tissues, generating a large number of immune cells to cause secondary killing of tumor tissues and cells, and with the assistance of metal nanoparticles loaded with immune drugs, the effect of this anti-tumor immunotherapy can be further enhanced. Therefore, the combination of metal nanoparticles and ablative therapy has broad research potential. This review covers common metallic nanoparticles used for ablative therapy and discusses in detail their characteristics, mechanisms of action, potential challenges, and prospects in the field of ablation.

Hybrid Nanoplatforms Comprising Organic Nanocompartments Encapsulating Inorganic Nanoparticles for Enhanced Drug Delivery and Bioimaging Applications

Organic and inorganic nanoparticles (NPs) have attracted significant attention due to their unique physico-chemical properties, which have paved the way for their application in numerous fields including diagnostics and therapy. Recently, hybrid nanomaterials consisting of organic nanocompartments (e.g., liposomes, micelles, poly (lactic-co-glycolic acid) NPs, dendrimers, or chitosan NPs) encapsulating inorganic NPs (quantum dots, or NPs made of gold, silver, silica, or magnetic materials) have been researched for usage in vivo as drug-delivery or theranostic agents. These classes of hybrid multi-particulate systems can enable or facilitate the use of inorganic NPs in biomedical applications. Notably, integration of inorganic NPs within organic nanocompartments results in improved NP stability, enhanced bioavailability, and reduced systemic toxicity. Moreover, these hybrid nanomaterials allow synergistic interactions between organic and inorganic NPs, leading to further improvements in therapeutic efficacy. Furthermore, these platforms can also serve as multifunctional agents capable of advanced bioimaging and targeted delivery of therapeutic agents, with great potential for clinical applications. By considering these advancements in the field of nanomedicine, this review aims to provide an overview of recent developments in the use of hybrid nanoparticulate systems that consist of organic nanocompartments encapsulating inorganic NPs for applications in drug delivery, bioimaging, and theranostics.

Packaging of DNA Integrated with Metal Nanoparticles in Solution

The transformation of high-molecular DNA from a random swollen coil in a solution to a discrete nanosized particle with the ordered packaging of a rigid and highly charged double-stranded molecule is one of the amazing phenomena of polymer physics. DNA condensation is a well-known phenomenon in biological systems, yet its molecular mechanism is not clear. Understanding the processes occurring in vivo is necessary for the usage of DNA in the fabrication of new biologically significant nanostructures. Entropy plays a very important role in DNA condensation. DNA conjugates with metal nanoparticles are useful in various fields of nanotechnology. In particular, they can serve as a basis for creating multicomponent nanoplatforms for theranostics. DNA must be in a compact state in such constructions. In this paper, we tested the methods of DNA integration with silver, gold and palladium nanoparticles and analyzed the properties of DNA conjugates with metal nanoparticles using the methods of atomic force microscopy, spectroscopy, viscometry and dynamic light scattering. DNA size, stability and rigidity (persistence length), as well as plasmon resonance peaks in the absorption spectra of systems were studied. The methods for DNA condensation with metal nanoparticles were analyzed.

Surface-Enhanced Raman Scattering (SERS) Substrates Based on Ag-Nanoparticles and Ag-Nanoparticles/Poly (methyl methacrylate) Composites

SERS substrates formed by spherical silver nanoparticles (Ag-NPs) with a 15 nm average diameter adsorbed on Si substrate at three different concentrations and Ag/PMMA composites formed by an opal of PMMA microspheres of 298 nm average diameter were synthesized. The Ag-NPs were varied at three different concentrations. We have observed from SEM micrographs, in the Ag/PMMA composites, the periodicity of the PMMA opals is slightly altered as the Ag-NP concentration is increased; as a consequence of this effect, the PBGs maxima shift toward longer wavelengths, decrease in intensity, and broaden as the Ag-NP concentration is increased in the composites. The performance of single Ag-NP and Ag/PMMA composites as SERS substrates was determined using methylene blue (MB) as a probe molecule with concentrations in the range of 0.5 µM to 2.5 µM. We found that in both single Ag-NP and Ag/PMMA composites as SERS substrates, the enhancement factor (EF) increases as the Ag-NP concentration is increased. We highlight that the SERS substrate with the highest concentration of Ag-NPs has the highest EF due to the formation of metallic clusters on the surface, which generates more "hot spots". The comparison of the EFs of the single Ag-NP with those of Ag/PMMA composite SERS substrates shows that the EFs of the former are nearly 10-fold higher than those of Ag/PMMA composites. This result is obtained probably due to the porosity of the PMMA microspheres that decreases the local electric field strength. Furthermore, PMMA exerts a shielding effect that affects the optical efficiency of Ag-NPs. Moreover, the metal-dielectric surface interaction contributes to the decrease in the EF. Other aspect to consider in our results is in relation to the difference in the EF of the Ag/PMMA composite and Ag-NP SERS substrates and is due to the existing mismatch between the frequency range of the PMMA opal stop band and the LSPR frequency range of the Ag metal nanoparticles adsorbed on the PMMA opal host matrix.

Advanced Ag nanoparticles for the catalyzation of glyoxylic acid oxidation in through-holes electroless copper metallization

Advanced Ag nanoparticles (Ag NPs) were prepared by wet chemical oxidation-reduction method, using mainly the tannic acid as reducing agent and carboxymethylcellulose sodium as stabilizer. The prepared Ag NPs uniformly disperse and are stable for more than one month without agglomeration. The studies of transmission electron microscopy (TEM) and ultraviolet-visible (UV-vis) absorption spectroscopy indicate that the Ag NPs are in homogeneous sphere with only 4.4 nm average size and narrow particle size distribution. Electrochemical measurements reveal that the Ag NPs behave excellent catalytic activity for electroless copper plating using glyoxylic acid as reducing agent. In situ fourier transform infrared (in situ FTIR) spectroscopic analysis combined with density functional theory (DFT) calculation illustrate that the molecular oxidation of glyoxylic acid catalyzed by Ag NPs is as the following routes: glyoxylic acid molecule first is adsorbed on Ag atoms with carboxyl oxygen terminal, then hydrolyzed to diol anionic intermediate, and last oxidized to oxalic acid. Time-resolved in situ FTIR spectroscopy further reveals the real-time reactions of electroless copper plating as follows: glyoxylic acid is continuously oxidized to oxalic acid and releases electrons at the active catalyzing spots of Ag NPs, and Cu(II) coordination ions are in situ reduced by the electrons. Based on the excellent catalytic activity, the advanced Ag NPs can replace the expensive Pd colloids catalyst and successfully apply in through-holes metallization of printed circuit board (PCB) by electroless copper plating.

The impact of silver nanoparticles on the growth of plants: The agriculture applications

Nanotechnology is the most advanced and rapidly progressing field of science and technology. It primarily deals with developing novelty in nanomaterials by understanding and controlling matter at the nanoscale level. Silver nanoparticles (AgNPs) are the most prominent nanoparticles incorporated with wide-ranging applications, owing to their distinct characteristics. Different methods have been employed for nanoparticles synthesis like chemical method, physical method, photochemical method, top-down/bottom-up approach and biological methods. The positive impacts of silver nanoparticles have been observed in various economy-based sectors, including agriculture. The scientific curiosity about AgNPs in agriculture and plant biotechnology has shown optimum efficacy over the last few years. It not only enhances seed germination and plant growth, but also improves the quantum efficiency of the photosynthetic process. AgNPs play a vital role in agriculture by having several applications that are crucial for ensuring food security and improving crop production. Moreover, they also act as nano-pesticides, providing sufficient dose to the target plants without releasing unnecessary pesticides into the environment. Nano-fertilizers slowly release nutrients to the plants, thereby preventing excessive nutrient loss. AgNPs are utilized for effective and non-toxic pest management, making them an excellent tool for combating pests safely. They combine either edible or non-biodegradable polymers for active food packaging. In addition, AgNPs also possess diverse biological properties such as antiviral, antibacterial and antifungal activities, which protect plants from hazardous microbes. The aim of this review is to comprehensively survey and summarize recent literature regarding the positive and negative impacts of AgNPs on plant growth, as well as their agricultural applications.

A Straightforward Method for the Development of Positively Charged Gold Nanoparticle-Based Vectors for Effective siRNA Delivery

The therapeutic potential of short interfering RNA (siRNA) to treat many diseases that are incurable with traditional preparations is limited by the extensive metabolism of serum nucleases, low permeability through biological membrane barriers because of a negative charge, and endosomal trapping. Effective delivery vectors are required to overcome these challenges without causing unwanted side effects. Here, we present a relatively simple synthetic protocol to obtain positively charged gold nanoparticles (AuNPs) with narrow size distribution and the surface modified with Tat-related cell-penetrating peptide. The AuNPs were characterized using TEM and the localized surface plasmon resonance technique. The synthesized AuNPs showed low toxicity in experiments in vitro and were able to effectively form complexes with double-stranded siRNA. The obtained delivery vehicles were used for intracellular delivery of siRNA in an ARPE-19 cell line transfected with secreted embryonic alkaline phosphatase (SEAP). The delivered oligonucleotide remained intact and caused a significant knockdown effect on SEAP cell production. The developed material could be useful for delivery of negatively charged macromolecules, such as antisense oligonucleotides and various RNAs, particularly for retinal pigment epithelial cell drug delivery.

Silver-Based Surface Plasmon Sensors: Fabrication and Applications

A series of novel phenomena such as optical nonlinear enhancement effect, transmission enhancement, orientation effect, high sensitivity to refractive index, negative refraction and dynamic regulation of low threshold can be generated by the control of surface plasmon (SP) with metal micro-nano structure and metal/material composite structure. The application of SP in nano-photonics, super-resolution imaging, energy, sensor detection, life science, and other fields shows an important prospect. Silver nanoparticles are one of the commonly used metal materials for SP because of their high sensitivity to refractive index change, convenient synthesis, and high controllable degree of shape and size. In this review, the basic concept, fabrication, and applications of silver-based surface plasmon sensors are summarized.

Solid-State Formation of a Potential Melphalan Delivery Nanosystem Based on β-Cyclodextrin and Silver Nanoparticles

Melphalan (Mel) is an antineoplastic widely used in cancer and other diseases. Its low solubility, rapid hydrolysis, and non-specificity limit its therapeutic performance. To overcome these disadvantages, Mel was included in β-cyclodextrin (βCD), which is a macromolecule that increases its aqueous solubility and stability, among other properties. Additionally, the βCD-Mel complex has been used as a substrate to deposit silver nanoparticles (AgNPs) through magnetron sputtering, forming the βCD-Mel-AgNPs crystalline system. Different techniques showed that the complex (stoichiometric ratio 1:1) has a loading capacity of 27%, an association constant of 625 M^-1, and a degree of solubilization of 0.034. Added to this, Mel is partially included, exposing the NH₂ and COOH groups that stabilize AgNPs in the solid state, with an average size of 15 ± 3 nm. Its dissolution results in a colloidal solution of AgNPs covered by multiple layers of the βCD-Mel complex, with a hydrodynamic diameter of 116 nm, a PDI of 0.4, and a surface charge of 19 mV. The in vitro permeability assays show that the effective permeability of Mel increased using βCD and AgNPs. This novel nanosystem based on βCD and AgNPs is a promising candidate as a Mel nanocarrier for cancer therapy.

Chiral inorganic nanomaterials for biological applications

Chiral nanomaterials in biology play indispensable roles in maintaining numerous physiological processes, such as signaling, site-specific catalysis, transport, protection, and synthesis. Like natural chiral nanomaterials, chiral inorganic nanomaterials can also be established with similar size, charge, surface properties, and morphology. However, chiral inorganic nanomaterials usually exhibit extraordinary properties that are different from those of organic materials, such as high g-factor values, broad distribution range, and symmetrical mirror configurations. Because of these unique characteristics, there is great potential for application in the fields of biosensing, drug delivery, early diagnosis, bio-imaging, and disease therapy. Related research is summarized and discussed in this review to showcase the bio-functions and bio-applications of chiral inorganic nanomaterials, including the construction methods, classification and properties, and biological applications of chiral inorganic nanomaterials. Moreover, the deficiencies in existing studies are noted, and future development is prospected. This review will provide helpful guidance for constructing chiral inorganic nanomaterials with specific bio-functions for problem solving in living systems.

Laser Ablated Albumin Functionalized Spherical Gold Nanoparticles Indicated for Stem Cell Tracking

Cell tracking in cell-based therapy applications helps distinguish cell participation among paracrine effect, neovascularization, and matrix deposition. This preliminary study examined the cellular uptake of gold nanoparticles (AuNPs), observing cytotoxicity and uptake of different sizes and AuNPs concentrations in Adipose-derived stromal cells (ASCs). ASCs were incubated for 24 h with Laser ablated Albumin functionalized spherical AuNPs (LA-AuNPs), with average sizes of 2 nm and 53 nm in diameter, in four concentrations, 127 µM, 84 µM, 42 µM, and 23 µM. Cytotoxicity was examined by Live/Dead assay, and erythrocyte hemolysis, and the effect on the cytoskeleton was investigated by immunocytochemistry for β-actin. The LA-AuNPs were internalized by the ASCs in a size and concentration-dependent manner. Clusters were observed as dispersed small ones in the cytosol, and as a sizeable perinuclear cluster, without significant harmful effects on the cells for up to 2 weeks. The Live/Dead and hemolysis percentage results complemented the observations that the larger 53 nm LA-AuNPs in the highest concentrated solution significantly lowered cell viability. The demonstrated safety, cellular uptake, and labelling persistency with LA-AuNPs, synthesized without the combination of chemical solutions, support their use for cell tracking in tissue engineering applications.

Inorganic/organic combination: Inorganic particles/polymer composites for tissue engineering applications

Biomaterials have ushered the field of tissue engineering and regeneration into a new era with the development of advanced composites. Among these, the composites of inorganic materials with organic polymers present unique structural and biochemical properties equivalent to naturally occurring hybrid systems such as bones, and thus are highly desired. The last decade has witnessed a steady increase in research on such systems with the focus being on mimicking the peculiar properties of inorganic/organic combination composites in nature. In this review, we discuss the recent progress on the use of inorganic particle/polymer composites for tissue engineering and regenerative medicine. We have elaborated the advantages of inorganic particle/polymer composites over their organic particle-based composite counterparts. As the inorganic particles play a crucial role in defining the features and regenerative capacity of such composites, the review puts a special emphasis on the various types of inorganic particles used in inorganic particle/polymer composites. The inorganic particles that are covered in this review are categorised into two broad types (1) solid (e.g., calcium phosphate, hydroxyapatite, etc.) and (2) porous particles (e.g., mesoporous silica, porous silicon etc.), which are elaborated in detail with recent examples. The review also covers other new types of inorganic material (e.g., 2D inorganic materials, clays, etc.) based polymer composites for tissue engineering applications. Lastly, we provide our expert analysis and opinion of the field focusing on the limitations of the currently used inorganic/organic combination composites and the immense potential of new generation of composites that are in development.

Development, preparation, and evaluation of a novel dotted lateral flow immunochromatographic kit for rapid diagnosis of dermatophytosis

Dermatophytosis is a widely spread contagious zoonotic disease, affecting both man (tinea) and animals (ringworm). This disease is caused by a group of closely related keratinophilic fungi known collectively as the dermatophytes group. Although the wide distribution of dermatophytosis cases throughout the whole world and its adverse clinical effect on human health, economical effect on productive animals, and pet animal welfare, there is no rapid accurate diagnostic tool for such disease. The current conducted study tries to accomplish the difficult equation by achieving an accurate, sensitive, specific, user-friendly, rapid, robust, device-less, deliverable to end-users, and economic cost for the development and production of diagnostic kits. Through the development of a rapid diagnostic kit based on immunochromatographic assay with three major affordable reproducible production stages; preliminary stage, developmental and standardization stage, and evaluation stage. Obtaining dermatophytes-specific polyclonal antibodies against criteria-based selected dermatophytes strains associating proper gold nanoparticle preparation, characterization, and conjugation, with proper loading of the different bio-reactants on the efficiently laminated and fabricated lateral flow strips were the main challenge and control points through the whole process. Also, as a result of examining 100 animal samples using the new kit, the κ coefficients of the kit with the direct microscopy while the kit with the culture were 0.44 and 0.76, respectively. Therefore, the newly designated and developed kit showed a very promising competitive diagnostic result within 5-7 min through easy-to-be-performed three steps.

Non-medicinal parts of safflower (bud and stem) mediated sustainable green synthesis of silver nanoparticles under ultrasonication: optimization, characterization, antioxidant, antibacterial and anticancer potential

The flower of safflower is widely used in Chinese herbal preparations and the non-medicinal parts have been applied to develop a sustainable green method, where AgNPs were generated using a mixture of leaf and stem after 12 h of incubation in the dark. In this study, we intend to improve the efficiency of the reduction reaction and optimize this green method by selecting other non-medicinal parts, such as the bud and the pure stem, evaluating the biosynthesis parameters and harnessing the assistance of ultrasonication. Visual observation and UV-vis spectroscopy confirmed that both safflower stem (SS) and bud (SB) mediated AgNPs (SS-AgNPs and SB-AgNPs, respectively) could be produced rapidly over time under ultrasonication. An alkaline solution could accelerate the formation of SS-AgNPs and SB-AgNPs with greater surface loads. SS-AgNPs and SB-AgNPs of small size could be obtained at pH 8.0 and 10.0, respectively. Large concentrations of SS and SB extract are also beneficial for forming AgNPs of small size. It is in acid and neutral solutions that monodispersed SS-AgNPs and SB-AgNPs can be generated. Characterization of selectively synthesized SS-AgNPs and SB-AgNPs demonstrated their spherical shape with the actual size below 30 nm covered by anions. Both SS-AgNPs and SB-AgNPs exhibited potent antioxidant and antibacterial activity. The MIC values of SS-AgNPs for S. aureus and E. coli were 12.5 and 25.0 μg mL^-1, respectively, slightly superior to SB-AgNPs. In an in vitro anticancer assay, both kinds of AgNPs show potent toxicity action against the SW620 cell line with IC₅₀ values of 5.4 and 10.6 μg mL^-1, respectively. However, only SS-AgNPs reveal an inhibitory action against the HeLa cell line, where the IC₅₀ is found to be 26.8 μg mL^-1. These results provide experimental proof that the assistance of ultrasonication and adjusting the process parameters are efficient methods for promoting the reduction reaction, and both SS and SB mediated AgNPs could serve as a promising antioxidant, antibacterial and anticancer agents.

Construction of antibacterial nano-silver embedded bioactive hydrogel to repair infectious skin defects

Background

Hydrogels loaded with antimicrobial agents have been widely used for treating infected wound defects. However, hydrogels derived from a porcine dermal extracellular matrix (PADM), containing silver nanoparticles (AgNPs), have not yet been studied. Therefore, we investigated the therapeutic effect of an AgNP-impregnated PADM (AgNP–PADM) hydrogel on the treatment of infected wounds.

Methods

An AgNP–PADM hydrogel was synthesized by embedding AgNPs into a PADM hydrogel. We examined the porosity, moisture retention, degradation, antibacterial properties, cytotoxicity, antioxidant properties, and ability of the PADM and AgNP–PADM hydrogels to treat infected wounds in animals.

Results

The PADM and AgNP–PADM hydrogels were pH sensitive, which made them flow dynamically and solidify under acidic and neutral conditions, respectively. The hydrogels also exhibited porous network structures, satisfactory moisture retention, and slow degradation. Additionally, the AgNP–PADM hydrogel showed a slow and sustained release of AgNPs for at least 7 days without the particle size changing. Thus, the AgNPs exhibited adequate antibacterial ability, negligible toxicity, and antioxidant properties in vitro. Moreover, the AgNP–PADM hydrogel promoted angiogenesis and healed infected skin defects in vivo.

Conclusions

The AgNP–PADM hydrogel is a promising bioderived antibacterial material for clinical application to infected wound dressings.

Silver as an Antibiotic-Independent Antimicrobial: Review of Current Formulations and Clinical Relevance

Background: The increase of multi-drug-resistant organisms has revived the use of silver as an alternative antibiotic-independent antimicrobial. Although silver's multimodal mechanism of action provides low risk for bacterial resistance, high local and uncontrolled concentrations have shown toxicity. This has resulted in efforts to develop novel silver formulations that are safer and more predictable in their application. Optimization of silver as an antimicrobial is crucial given the growing resistance profile against antibiotics. This article reviews formulations of silver used as antimicrobials, focusing on the mechanisms of action, potential for toxicity, and clinical applications. Methods: A search of four electronic databases (PubMed, Embase, MEDLINE, and Cochrane Library) was conducted for relevant studies up to January 2022. Searches were conducted for the following types of silver: ionic, nanoparticles, colloidal, silver nitrate, silver sulfadiazine, silver oxide, silver carboxylate, and AQUACEL^® (ConvaTec, Berkshire, UK). Sources were compiled based on title and abstract and screened for inclusion based on relevance and study design. Results: A review of the antimicrobial activity and uses of ionic silver, silver nanoparticles, colloidal silver, silver nitrate, silver sulfadiazine, silver oxide, Aquacel, and silver carboxylate was conducted. The mechanisms of action, clinical uses, and potential for toxicity were studied, and general trends between earlier and more advanced formulations noted. Conclusions: Early forms of silver have more limited utility because of their uncontrolled release of silver ions and potential for systemic toxicity. Multiple new formulations show promise; however, there is a need for more prospective in vivo studies to validate the clinical potential of these formulations.

Natural corrosion-induced gold nanoparticles yield purple color of Alhambra palaces decoration

Despite its fame as a chemically inert noble metal, gold (alloys) may suffer degradation under specific scenarios. Here, we show evidence of electrochemically corroded gilded tin plasterwork in the Alhambra (Granada, Spain) driving spontaneously made gold nanospheres with the optimal size (ca. 70 nm) to impart purple color at the surface. Purple gold on damaged artworks is found sparsely, and its formation is not fully explained yet. We prove that our decayed gold/silver-tin ornament is due to sequential/coexisting galvanic corrosion, differential aeration corrosion, and dealloying of nonperfectly bonded and defect-based metals. Damage is enhanced by exposure to a chloride-rich atmosphere. A white gypsum coat applied during the 19th century to overlap the unaesthetic gilding assists observation of the gold-based purple color. Our work demonstrates gold dissolution, millimetric migration, physical translocation, and deposition as secondary pure gold nanospheres over a centurial time scale under natural environmental conditions.

Faris H, Ahmed H, Mamdouh S, Thambiratnam K, Mohamed T. Using Femtosecond Laser Pulses to Explore the Nonlinear Optical Properties of Au NP Colloids That Were Synthesized by Laser Ablation

In this study, we experimentally investigated the nonlinear optical properties of Au nanoparticles (Au NPs) that were prepared in pure distilled water using the laser ablation method. The Au NPs were prepared using a nanosecond Nd:YAG laser with an ablation time of 5 or 10 min at a constant laser energy of 100 mJ. The structure and the linear optical properties of the Au NPs were investigated using a transmission electron microscope (TEM) and UV-visible spectrophotometer analysis, respectively. The TEM measurements showed that the average size of the Au NPs varied from 20.3 to 14.1 nm, depending on the laser ablation time. The z-scan technique was used to investigate the nonlinear refractive index (n2) and nonlinear absorption coefficient (γ) of the Au NPs, which were irradiated at different excitation wavelengths that ranged from 740 to 820 nm and at different average powers that ranged from 0.8 to 1.6 W. The Au NP samples exhibited a reverse saturable absorption (RSA) behavior that increased when the excitation wavelength and/or incident laser power increased. In addition, the Au NPs acted as a self-defocusing material whenever the excitation wavelength or incident power were modified.

Characterization of the biosynthesized intracellular and extracellular plasmonic silver nanoparticles using Bacillus cereus and their catalytic reduction of methylene blue

The biosynthesis of silver nanoparticles (Ag NPs) has been studied in detail using two different approaches. For the first time, Bacillus cereus is used for one-pot biosynthesis of capsulated Ag NPs, using both intracellular and extracellular approaches. To discriminate between the produced nanostructures by these two approaches, their structures, nanomorphologies, optical properties, hydrodynamic sizes and zeta potentials are studied using different techniques. Fourier-transform infrared spectroscopy was used to identify the bioactive components responsible for the reduction of Ag⁺ ions into Ag and the growth of stable Ag NPs. Scanning and transmission electron microscopy images displayed spherical and polygon nanomorphology for the intracellular and extracellular biosynthesized Ag NPs. For intracellular and extracellular biosynthesized Ag NPs, a face-centred cubic structure was observed, with average crystallite sizes of 45.4 and 90.8 nm, respectively. In comparison to the noncatalytic reduction test, the catalytic activities of intracellular and extracellular biosynthesized Ag NPs were explored for the reduction of highly concentrated MB dye solution. Extracellular Ag NPs achieved 100% MB reduction efficacy after around 80 min, compared to 50.6% and 24.1% in the presence and absence of intracellular Ag NPs, respectively. The rate of MB reduction was boosted by 22 times with the extracellular catalyst, and by 3 times with the intracellular catalyst. Therefore, the extracellular production process of Ag NPs utilizing Bacillus cereus bacteria might be applied in the industry as a cost-effective way for eliminating the toxic MB dye.

The Antibacterial and Cytotoxic Effects of Silver Nanoparticles Coated Titanium Implants: A Narrative Review

Nanotechnology has become an emerging research field with numerous biomedical scientific applications. Silver possesses bactericidal activities that have been harnessed for centuries; however, there is a concern about the toxic effects of silver nanoparticles. This paper aims to provide an overview of silver-treated dental implants and discuss their potential to reduce the prevalence of peri-implant diseases. An electronic search was performed using PubMed. After screening, data extraction was performed on the 45 remaining articles using inclusion and exclusion criteria. Most of the articles demonstrated that silver nanoparticles embedded in a coating layer and/or on surface-treated titanium exhibit sound antibacterial effects and biocompatibility. Most of the reviewed studies revealed that silver nanoparticles on dental implant surfaces reduced cytotoxicity but provided a prolonged antibacterial effect. The cytotoxicity and antibacterial effect are closely linked to how the silver nanoparticles are released from the titanium surfaces, where a slower release increases cell viability and proliferation. However, to improve the clinical translation, there is still a need for more studies, especially evaluating the long-term systemic effects and studies recreating the conditions in the oral cavity.

Heterostructures Based on Cobalt Phthalocyanine Films Decorated with Gold Nanoparticles for the Detection of Low Concentrations of Ammonia and Nitric Oxide

This work is aimed at the development of new heterostructures based on cobalt phthalocyanines (CoPc) and gold nanoparticles (AuNPs), and the evaluation of the prospects of their use to determine low concentrations of ammonia and nitric oxide. For this purpose, CoPc films were decorated with AuNPs by gas-phase methods (MOCVD and PVD) and drop-casting (DC), and their chemiresistive sensor response to low concentrations of NO (10–50 ppb) and NH₃ (1–10 ppm) was investigated. A comparative analysis of the characteristics of heterostructures depending on the preparation methods was carried out. The composition, structure, and morphology of the resulting hybrid films were studied by X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma atomic emission (ICP-AES) spectroscopy, as well as electron microscopy methods to discuss the effect of these parameters on the sensor response of hybrid films to ammonia and nitric oxide. It was shown that regardless of the fabrication method, the response of Au/CoPc heterostructures to NH₃ and NO gases increased with an increase in the concentration of gold. The sensor response of Au/CoPc heterostructures to NH₃ increased 2–3.3 times compared to CoPc film, whereas in the case of NO it increased up to 16 times. The detection limits of the Au/CoPc heterostructure with a gold content of ca. 2.1 µg/cm² for NH₃ and NO were 0.1 ppm and 4 ppb, respectively. It was shown that Au/CoPc heterostructures can be used for the detection of NH₃ in a gas mixture simulating exhaled air (N₂—74%, O₂—16%, H₂O—6%, CO₂—4%).

Gold nanoparticle-based optical nanosensors for food and health safety monitoring: recent advances and future perspectives

Modern society has been facing serious health-related problems including food safety, diseases and illness. Hence, it is urgent to develop analysis methods for the detection and control of food contaminants, disease biomarkers and pathogens. As the traditional instrumental methods have several disadvantages, including being time consuming, and having high cost and laborious procedures, optical nanosensors have emerged as promising alternative or complementary approaches to those traditional ones. With the advantages of simple preparation, high surface-to-volume ratio, excellent biocompatibility, and especially, unique optical properties, gold nanoparticles (AuNPs) have been demonstrated as excellent transducers for optical sensing systems. Herein, we provide an overview of the synthesis of AuNPs and their excellent optical properties that are ideal for the development of optical nanosensors based on local surface plasmon resonance (LSPR), colorimetry, fluorescence resonance energy transfer (FRET), and surface-enhanced Raman scattering (SERS) phenomena. We also review the sensing strategies and their mechanisms, as well as summarizing the recent advances in the monitoring of food contaminants, disease biomarkers and pathogens using developed AuNP-based optical nanosensors in the past seven years (2015-now). Furthermore, trends and challenges in the application of these nanosensors in the determination of those analytes are discussed to suggest possible directions for future developments.

Green synthesis of gold nanaoparticles using Delphinium Chitralense tuber extracts, their characterization and enzyme inhibitory potential

Green synthesis has been introduced as an alternative to chemical synthesis due to the serious consequences. Metal nanoparticles synthesized through green approach have different pharmaceutical, medical and agricultural applications. The present study followed a green and simple route for the preparation of potentially bioactive gold nanoparticles (Au NPs). Au NPs were prepared via green synthesis approach using crude basic alkaloidal portion of the tuber of Delphinium chitralense. The green synthesized Au NPs were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) fourier transform infrared (FTIR), and UV-Visible spectrophotometer. Morphological analysis shows that Au NPs have cubic geometry with different sizes. UV-Vis spectroscopic analysis confirmed the synthesis of Au NPs while XRD proved their pure crystalline phase. The Au NPs showed promising dose dependent inhibition of both AChE and BChE as compared to the crude as well as standard drug.

Statistical optimization of silver nanoparticle synthesis by green tea extract and its efficacy on colorimetric detection of mercury from industrial waste water

For the optimization of silver nanoparticle production, a central composite design was used with three parameters: AgNO₃ concentration, green tea extract concentration, and temperature at three different levels. The size of the synthesized silver nanoparticle, its UV absorbance, zeta potential, and polydispersity index were set as the response parameters. Silver nanoparticles obtained in the optimization process were characterized and its efficacy on colorimetric detection of mercury was evaluated. The response variables were significant for the factors analyzed, and each variable had a significant model (P < 0.05). The ideal conditions were: 1 mM AgNO₃, 0.5% green tea extract, and 80 °C temperature. To analyze the produced AgNPs under certain ideal conditions, Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD) were used. The UV-visible spectra of AgNPs revealed an absorption maxima at 424 nm. The XRD pattern reveals a significant diffraction peak at 38.25°, 44.26°, 64.43°, and 77.49°, which corresponds to the (111), (200), (220), and (311) planes of polycrystalline face-centered cubic (fcc) silver, respectively. The TEM and SEM analyses confirmed that the particles were spherical, and dynamic light scattering study determined the average diameter of AgNPs to be 77.4 nm. The AgNPs have a zeta potential of -62.6 mV, as determined by the zeta sizer analysis. The AgNPs detects mercury at a micromolar concentration. Furthermore, the environmentally friendly generated AgNPs were used to detect mercury in a colorimetric method that was effectively employed for analytical detection of Hg²⁺ ions in an aqueous environment for the purpose of practical application.

Silver and Gold Nanoparticles for Antimicrobial Purposes against Multi-Drug Resistance Bacteria

Several pieces of research have been done on transition metal nanoparticles and their nanocomplexes as research on their physical and chemical properties and their relationship to biological features are of great importance. Among all their biological properties, the antibacterial and antimicrobial are especially important due to their high use for human needs. In this article, we will discuss the different synthesis and modification methods of silver (Ag) and gold (Au) nanoparticles and their physicochemical properties. We will also review some state-of-art studies and find the best relationship between the nanoparticles' physicochemical properties and potential antimicrobial activity. The possible antimicrobial mechanism of these types of nanoparticles will be discussed in-depth as well.

Synthesis and Organization of Gold-Peptide Nanoparticles for Catalytic Activities

A significant development in the synthesis strategies of metal-peptide composites and their applications in biomedical and bio-catalysis has been reported. However, the random aggregation of gold nanoparticles provides the opportunity to find alternative fabrication strategies of gold-peptide composite nanomaterials. In this study, we used a facile strategy to synthesize the gold nanoparticles via a green and simple approach where they show self-alignment on the assembled nanofibers of ultrashort oligopeptides as a composite material. A photochemical reduction method is used, which does not require any external chemical reagents for the reduction of gold ions, and resultantly makes the gold nanoparticles of size ca. 5 nm under mild UV light exposure. The specific arrangement of gold nanoparticles on the peptide nanofibers may indicate the electrostatic interactions of two components and the interactions with the amino group of the peptide building block. Furthermore, the gold-peptide nanoparticle composites show the ability as a catalyst to degradation of environmental pollutant p-nitrophenol to p-aminophenol, and the reaction rate constant for catalysis is calculated as 0.057 min-1 at a 50-fold dilute sample of 2 mg/mL and 0.72 mM gold concentration in the composites. This colloidal strategy would help researchers to fabricate the metalized bioorganic composites for various biomedical and bio-catalysis applications.

Green Fabrication of Bioactive Silver Nanoparticles Using Mentha pulegium Extract under Alkaline: An Enhanced Anticancer Activity

Fabrication of silver nanoparticles (AgNPs) using Chinese herbal medicine is popular as the bioactive components included in them would generate potential synergistic effect with the metal nanoparticles. The leaf of Mentha pulegium, whose extract contains a range of phytochemicals and exhibits a wide spectrum of bioactivities, is used as Chinese herbal medicine after drying naturally. Thus, the green synthesis of AgNPs using Mentha pulegium has aroused interests from analysts. However, the biosynthesis of AgNPs under alkaline conditions and the biological activities remain elusive, where alkaline conditions may influence the physicochemical properties and the biological activities of biosynthesized AgNPs. In this study, we were stimulated to fabricate bioactive AgNPs using Mentha pulegium extract under alkaline conditions, accompanied by a systematic evaluation on the effect of biosynthesis parameters on the formation, average size, and polydispersity of AgNPs. Our results showed that alkaline conditions could accelerate the formation of AgNPs with a small average size but at a disadvantage to the polydispersity. Additionally, the as-prepared AgNPs had a hexagonal structure and spherical shape with an average size of 15.7 ± 0.1 nm, existing in the monodispersed form and revealing a high degree of stability. The AgNPs exhibited potent antioxidant and significant inhibitory activity for both bacterial and cancer cell lines. The MIC values of AgNPs for Staphylococcus aureus and Escherichia coli were both 50.0 μg·mL-1, and the IC50 values for HCT116, HepG2, and HeLa cells were 9.0, 14.5, and 31.5 μg·mL-1, respectively. The AgNPs biosynthesized using M. pulegium under alkaline conditions, which had a smaller size and more surface loads, are entirely different with those synthesized under acidic conditions, and the anticancer activity increased significantly. The internalization of AgNPs inside these five cells displayed a variant trend with variable AgNPs concentrations, suggesting the different mechanism of cell death. For two pathogens, HCT116 and HepG2 cancer cell lines, both cell wall and intracellular damage may be responsible for the cell death. However, for Hela cell line the cell death may be rooted in oxidative stress or intracellular penetration. These results confirmed that the AgNPs biosynthesized from M. pulegium extract under alkaline conditions would act as better anticancer agents in biomedicine.

The Role of Rosmarinic Acid on the Bioproduction of Gold Nanoparticles as Part of a Photothermal Approach for Breast Cancer Treatment

Breast cancer is a high-burden malignancy for society, whose impact boosts a continuous search for novel diagnostic and therapeutic tools. Among the recent therapeutic approaches, photothermal therapy (PTT), which causes tumor cell death by hyperthermia after being irradiated with a light source, represents a high-potential strategy. Furthermore, the effectiveness of PTT can be improved by combining near infrared (NIR) irradiation with gold nanoparticles (AuNPs) as photothermal enhancers. Herein, an alternative synthetic method using rosmarinic acid (RA) for synthesizing AuNPs is reported. The RA concentration was varied and its impact on the AuNPs physicochemical and optical features was assessed. Results showed that RA concentration plays an active role on AuNPs features, allowing the optimization of mean size and maximum absorbance peak. Moreover, the synthetic method explored here allowed us to obtain negatively charged AuNPs with sizes favoring the local particle accumulation at tumor site and maximum absorbance peaks within the NIR region. In addition, AuNPs were safe both in vitro and in vivo. In conclusion, the synthesized AuNPs present favorable properties to be applied as part of a PTT system combining AuNPs with a NIR laser for the treatment of breast cancer.

Biogenic proficient synthesis of (Au-NPs) via aqueous extract of Red Dragon Pulp and seed oil: Characterization, antioxidant, cytotoxic properties, anti-diabetic anti-inflammatory, anti-Alzheimer and their anti-proliferative potential against cancer cell lines

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Novel Green synthesis of Au-NPs using Dragon fruit pulp and seed oil extract for the first time.

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Use of green and safer protocol for synthesis of Au-NPs further demonstrate that we can apply green chemistry protocols to reduce environmental pollution and disposal of waste toxicants.

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FTIR analysis confirmed the capping of therapeutically potent phytochemicals which are of great use in applied field especially medical.

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Significant Anti-diabetic, Anti-inflammatory, Anti-Alzheimer and Cytotoxic potential of biosynthesized Au-NPs create a new idea and shifting experts to treat cancerous cell lines.

Gold nanoparticles with tiny sizes and biostability are particularly essential and are employed in a variety of biomedical applications. Using a reducing agent and a stabilising agent to make gold nanoparticles has been reported in a number of studies. Gold nanoparticles with a particle size of 25.31 nm were synthesized in this study utilising Hylocereus polyrhizus (Red Pitaya) extract, which functions as a reducing and stabilising agent. The extract of Red Pitaya is said to be a powerful antioxidant and anti-cancer agent. Because of its substantial blood biocompatibility and physiological stability, green production of gold nanoparticles with H. polyrhizus fruit extract is an alternative to chemical synthesis and useful for biological and medical applications. The formation and size distribution of gold nanoparticles were confirmed by HPLC, UV-Vis spectrophotometer, X-ray diffraction (XRD), Dynamic light scattering (DLS), Zeta potential, Transmission electron microscopy (TEM), Fourier transformed infrared spectroscopy (FTIR), Energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS). The well-analysed NPs were used in various biological assays, including anti-diabetic, anti-inflammatory, anti-Alzheimer, and antioxidant (DPPH), and cytotoxic investigations. The NPs also showed a dose-dependent cytotoxic activity against HCT-116, HepG2 and MCF-7 cell lines, with IC₅₀ of 100 µg/mL for HCT-116 cells, 155 µg/mL for HepG2, and for MCF-7 cells the value was 165 µg/mL respectively. Finally, the outstanding biocompatibility of Au-NPs has led to the conclusion that they are a promising choice for various biological applications.

Engineered Nanomaterials in Soil: Their Impact on Soil Microbiome and Plant Health

A staggering number of nanomaterials-based products are being engineered and produced commercially. Many of these engineered nanomaterials (ENMs) are finally disposed into the soil through various routes in enormous quantities. Nanomaterials are also being specially tailored for their use in agriculture as nano-fertilizers, nano-pesticides, and nano-based biosensors, which is leading to their accumulation in the soil. The presence of ENMs considerably affects the soil microbiome, including the abundance and diversity of microbes. In addition, they also influence crucial microbial processes, such as nitrogen fixation, mineralization, and plant growth promoting activities. ENMs conduct in soil is typically dependent on various properties of ENMs and soil. Among nanoparticles, silver and zinc oxide have been extensively prepared and studied owing to their excellent industrial properties and well-known antimicrobial activities. Therefore, at this stage, it is imperative to understand how these ENMs influence the soil microbiome and related processes. These investigations will provide necessary information to regulate the applications of ENMs for sustainable agriculture and may help in increasing agrarian production. Therefore, this review discusses several such issues.

Catalytic and Medical Potential of a Phyto-Functionalized Reduced Graphene Oxide-Gold Nanocomposite Using Willow-Leaved Knotgrass

In the current study, a simple, environmentally friendly, and cost-effective reduced graphene oxide-gold nanoparticle (rGO-AuNP) nanocomposite was successfully phytosynthesized using the aqueous leaf extract of a common weed found on the Nile banks, Persicaria salicifolia, for the first time. The phytosynthesis of rGO-AuNPs was first confirmed via the color transformation from brown to black as well as throughvarious techniques such as transmission electron microscopy (TEM) and Raman spectroscopy. Two UV-vis peaks at 275 and 530 nm were observed for the nanocomposite with a typical particle size of mostly spherical AuNPs of 15-20 nm. However, other shapes were occasionally detected including rods, triangles, and rhomboids. Existing phytoconstituents such as flavonoids and glycosides in the plant extract were suggested to be responsible for the phytosynthesis of rGO-AuNPs. The excellent catalytic efficacy of rGO-AuNPs against MB degradation was confirmed, and a high antibacterial efficiency against Escherichia coli and Klebsiella pneumonia was also confirmed. Promising antioxidant performance of rGO-AuNPs was also proved. Furthermore, it was concluded that rGO-AuNPs acquired higher efficiency than AuNPs synthesized from the same plant extract in all of the studied applications.

Nanogold-based materials in medicine: from their origins to their future

The properties of gold-based materials have been explored for centuries in several research fields, including medicine. Multiple published production methods for gold nanoparticles (AuNPs) have shown that the physicochemical and optical properties of AuNPs depend on the production method used. These different AuNP properties have allowed exploration of their usefulness in countless distinct biomedical applications over the last few years. Here we present an extensive overview of the most commonly used AuNP production methods, the resulting distinct properties of the AuNPs and the potential application of these AuNPs in diagnostic and therapeutic approaches in biomedicine.

Plasmonic Spherical Nanoparticles Coupled with Titania Nanotube Arrays Prepared by Anodization as Substrates for Surface-Enhanced Raman Spectroscopy Applications: A Review

As surface-enhanced Raman spectroscopy (SERS) continues developing to be a powerful analytical tool for several probes, four important aspects to make it more accessible have to be addressed: low-cost, reproducibility, high sensibility, and recyclability. Titanium dioxide nanotubes (TiO₂ NTs) prepared by anodization have attracted interest in this field because they can be used as safe solid supports to deposit metal nanoparticles to build SERS substrate nanoplatforms that meet these four desired aspects. TiO₂ NTs can be easily prepared and, by varying different synthesis parameters, their dimensions and specific features of their morphology can be tuned allowing them to support metal nanoparticles of different sizes that can achieve a regular dispersion on their surface promoting high enhancement factors (EF) and reproducibility. Besides, the TiO₂ photocatalytic properties enable the substrate's self-cleaning property for recyclability. In this review, we discuss the different methodological strategies that have been tested to achieve a high performance of the SERS substrates based on TiO₂ NTs as solid support for the three main noble metal nanoparticles mainly studied for this purpose: Ag, Au, and Pt.

Argyreia nervosa (Samudra pala) leaf extract mediated silver nanoparticles and evaluation of their antioxidant, antibacterial activity, in vitro anticancer and apoptotic studies in KB oral cancer cell lines

In the present investigation, green synthesis of silver nanoparticles (AgNPs) was carried out using aqueous leaf extract of Argyreia nervosa. The results of the spectral characterisation have revealed that the surface Plasmon resonance band was observed at 421 nm confirms the formation of AgNPs. The Fourier Transform Infra-red Spectroscopy result shows the reduction of silver nitrate into AgNPs by the reduction of different functional groups. Transmission Electron Microscope analysis revealed that the particles are roughly spherical and poly-disperse in shape and size, the particles are within the size range of 10-55 nm. Dynamic Light Scattering revealed that the nanoparticles were also within the range of 10-50 nm, An-AgNPs have a high negative zeta potential value of -38.9 mV. An-AgNPs showed efficient free radical scavenging activity and showed excellent antimicrobial activity. Anti-proliferative and cytotoxic effect of An-AgNPs was carried out by MTT assay against KB oral cancer cells, the IC₅₀ value of An-AgNPs is 58.64 µg/ml. The cell's growth is arrested at the G2/M phase, so the An-AgNPs activated the Caspase 3 pathway which leads to the Apoptosis of KB oral cancer cells. So it is concluded that the green synthesised An-AgNPs have manifold functions.

Localized surface plasmon resonance-based biosensor on gold nanoparticles for Taenia solium detection

This paper describes, for the first time to our knowledge, a fast-response and specific biosensor for detection of Taenia solium, a parasite responsible for neurocysticercosis disease that affects the central nervous system. The biosensor is based on the localized surface plasmon resonance (LSPR) technique on gold nanoparticles (AuNPs) in colloidal suspension that were functionalized and activated with antibodies to perform an immuno-capture effect. The AuNPs were synthetized by Turkevich and seed-mediated growth methods. A variety of concentrations of T. solium antigen were added to test the detection and the dose-response profile. Small antigen concentrations were detected indicating that the limit of detection is lower than 0.1 µg/mL of antigen. The results demonstrate the potential of the AuNPs LSPR biosensor as a clinical tool for neurocysticercosis diagnostic.