Size controlled green synthesis of gold nanoparticles using Coffea arabica seed extract and their catalytic performance in 4-nitrophenol reduction

Na+ and Cl- adsorption derived enhancement in 4-nitrophenol reduction using Au/Ag nanoparticle: An experimental and theoretical study

4-Nitrophenol (4-NP) is an organic contaminant attached to textiles, pharmaceuticals, and pesticides. Its presence has been increasingly detected in various water bodies such as lakes, rivers, and occasionally in drinking water. The present work shows the reduction of 4-NP using a hybrid catalytic system composed of gold and silver nanoparticles supported onto the biogenic porous silica (AgAu-SiO2). The AgAu nanoparticles were fabricated in situ onto the salinized biogenic silica substrates through a green synthesis. The catalytic reaction was analyzed with NaBH4 and the proposed AgAu-SiO2 catalyst. Mimicking 4-NP reduction reaction in different spiked river/marine water samples revealed superior catalytic activity in marine water. Subsequently, interference studies performed in the presence of different metal salts and pHs (found in the marine water) showed the vital role played by NaCl in the 4-NP reduction as the increase in the NaCl concentration enhances the catalytic activity of the proposed catalyst. Additional reusability of the proposed catalyst demonstrated its efficacy up to 10 cycles. The density functional theory (DFT) results supported the experimental findings, confirming the crucial role of Na+ and Cl- in the catalytic process. Our experimental results, which have significant implications for the field, have been explained by comparing them with DFT calculations. The main reason behind the enhanced catalysis performance in our systems was deduced at the atomic scale. The study included the adsorption energies and electronic density of molecular structures (4-NP and 4-AP) on different surface coverages. In exceptional cases, at the intermediate of 4-NP on Au(111)-NaCl, a displacement of the electronic density is observed, leading to a quinoline-type ring weakening the N-O bond and favoring the catalytic performance.

Green synthesis of copper oxide nanoparticles using walnut shell and their size dependent anticancer effects on breast and colorectal cancer cell lines

Metal oxide nanoparticles(NPs) contain unique properties which have made them attractive agents in cancer treatment. The CuO nanoparticles were green synthesized using walnut shell powder in different calcination temperatures (400°, 500°, 700°, and 900 °C). The CuO nanoparticles are characterized by FTIR, XRD, BET, SEM and DLS analyses. SEM and DLS analyses showed that by increasing the required calcination temperature for synthesizing the NPs, their size was increased. DPPH analysis displayed no significant anti-oxidative properties of the CuO NPs. The MTT analysis showed that all synthesized CuO NPs exhibited cytotoxic effects on MCF-7, HCT-116, and HEK-293 cell lines. Among the CuO NPs, the CuO-900 NPs showed the least cytotoxic effect on the HEK-293 cell line (IC50 = 330.8 µg/ml). Hoechst staining and real-time analysis suggested that the CuO-900 NPs induced apoptosis by elevation of p53 and Bax genes expression levels. Also, the CuO-900 NPs increased the Nrf-2 gene expression level in MCF-7 cells, despite the HCT-116 cells. As can be concluded from the results, the CuO-900 NPs exerted promising cytotoxic effects on breast and colon cancer cells.

Biosynthesis and characterization of gold nanoparticles from citrullus colocynthis (L.) schrad pulp ethanolic extract: Their cytotoxic, genotoxic, apoptotic, and antioxidant activities

The age-old discipline of plant therapy has gained renewed importance through the utilization of plants for the synthesis of metal nanoparticles. However, toxicity testing and characterization of the recently synthesized nanomaterials are essential to evaluating their appropriate application. Citrullus colocynthis is a medicinal plant with several health benefits. Herein, we used its ethanolic pulp extract (PE) to manufacture gold nanoparticles (PE-AuNPs). Various approaches were employed to assess the MTT50 and NR50 values of PE and PE-AuNPs at different concentrations in the human hepatocarcinoma cell line (HepG2). The study aimed to assess the genotoxic effects and in vivo toxicity of PE and PE-AuNPs at MTT50 dosages. The quasi-spherical, cubic/triangular prisms, and nail-looking particles exhibited no antioxidant properties. They had an absorbance peak between 540 and 560 nm, diameters of less than 20 nm, hydrodynamic diameters of 177.9 nm, and a negative surface charge (-10.3 mV). The significant role of plant phytochemicals in the formation of metal nanoparticles is confirmed by the diminished antioxidant capacity of extract residues following PE-AuNP synthesis. PE-AuNPs exhibited in vivo and cytotoxic effects at relatively lower concentrations compared to PE. In contrast to PE, PE-AuNPs exhibited lower genotoxic at MTT50 dosages. Despite having MTT50 values of approximately 1.95 ± 0.06 and 0.89 ± 0.03 mg/ml, PE and PE-AuNPs can still be considered biocompatible. Nonetheless, our results suggest that the characteristics of recently produced nanoparticles can differ from those of the matching plant. Further investigation can provide a better understanding of the possible therapeutic and pharmacological impacts of PE-AuNPs.

Gold Nanoparticles (AuNPs)-Toxicity, Safety and Green Synthesis: A Critical Review

In recent years, the extensive exploration of Gold Nanoparticles (AuNPs) has captivated the scientific community due to their versatile applications across various industries. With sizes typically ranging from 1 to 100 nm, AuNPs have emerged as promising entities for innovative technologies. This article comprehensively reviews recent advancements in AuNPs research, encompassing synthesis methodologies, diverse applications, and crucial insights into their toxicological profiles. Synthesis techniques for AuNPs span physical, chemical, and biological routes, focusing on eco-friendly "green synthesis" approaches. A critical examination of physical and chemical methods reveals their limitations, including high costs and the potential toxicity associated with using chemicals. Moreover, this article investigates the biosafety implications of AuNPs, shedding light on their potential toxic effects on cellular, tissue, and organ levels. By synthesizing key findings, this review underscores the pressing need for a thorough understanding of AuNPs toxicities, providing essential insights for safety assessment and advancing green toxicology principles.

Microalgae as a potential natural source for the green synthesis of nanoparticles

The increasing global population is driving the development of alternative sources of food and energy, as well as better or new alternatives for health and environmental care, which represent key challenges in the field of biotechnology. Microalgae represent a very important source material to produce several high-value-added bioproducts. Due to the rapid changes in the modern world, there is a need to build new materials for use, including those in the nanometer size, although these developments may be chronological but often do not occur at a time. In the last few years, a new frontier has opened up at the interface of biotechnology and nanotechnology. This new frontier could help microalgae-based nanomaterials to possess new functions and abilities. Processes for the green synthesis of nanomaterials are being investigated, and the availability of biological resources such as microalgae is continuously being examined. The present review provides a concise overview of the recent advances in the synthesis, characterization, and applications of nanoparticles formed using a wide range of microalgae-based biosynthesis processes. Highlighting their innovative and sustainable potential in current research, our study contributes towards the in-depth understanding and provides latest updates on the alternatives offered by microalgae in the synthesis of nanomaterials.

Extremely Monodispersed Micrometer-Scale Spherical Particle Synthesis of Ag Inside a Microdroplet Vaporizing in Plasma

Spherical Ag particles have received considerable attention because of their unique properties as well as their applications in various fields. In the present study, the synthesis of micrometer-scale spherical Ag particles with an extremely narrow size distribution is demonstrated using a simple capacitively coupled atmospheric-pressure plasma reactor with an inkjet head. Droplets of a Ag nitrate aqueous solution are ejected from the inkjet head to synthesize Ag particles. The gaseous temperature in the reactor is adjusted such that Ag can be melted with a negligibly small vapor pressure. These particles exhibit a spherical shape with a smooth surface. The mean diameter of the particles is 0.91 ± 0.013 μm with a small coefficient of variation of 1.5%, the smallest value ever reported for Ag particles of less than 1 μm. The grain sizes of the particles are larger than 100 nm, as expected from the broadening of the X-ray diffraction peaks. The excellent monodispersity of the particles synthesized by this method may expand the applications with micrometer-scale spheres such as ball spacer, microsized ball bearing, and inks for printed electronics.

Exfoliated MXene-AuNPs hybrid in sensing and multiple catalytic hydrogenation reactions

The increasing use of nanomaterials in consumer products is expected to lead to environmental contamination sometime soon. As water pollution is a pressing issue that threatens human survival and impedes the promotion of human health, the search for adsorbents for removing newly identified contaminants from water has become a topic of intensive research. The challenges in the recyclability of contaminated water continue to campaign the development of highly reusable catalysts. Although exfoliated 2D MXene sheets have demonstrated the capability towards water purification, a significant challenge for removing some toxic organic molecules remains a challenge due to a need for metal-based catalytic properties owing to their rapid response. In the present study, we demonstrate the formation of hybrid structure AuNPs@MXene (Mo2CTx) during the sensitive detection of Au nanoparticle through MXene sheets without any surface modification, and subsequently its applications as an efficient catalyst for the degradation of 4-nitrophenol (4-NP), methyl orange (MO), and methylene blue (MB). The hybrid structure (AuNPs@MXene) reveals remarkable reusability for up to eight consecutive cycles, with minimal reduction in catalytic efficiency and comparable apparent reaction rate constant (Kapp) values for 4-NP, MB, and MO, compared to other catalysts reported in the literature.

Green Coffee Bean Extract Assisted Facile Synthesis of Reduced Graphene Oxide and Its Dye Removal Activity

To discharge the colored effluents from industries there needs to be effective and affordable treatment options. Adsorption using reduced graphene oxide (rGO) as an adsorbent is a prominent one. In this study, green coffee bean extract (GCBE) is utilized as a safe reducing agent for the reduction of graphene oxide (GO) to synthesize rGO. The formation of rGO is confirmed by a new peak in the UV-vis spectra at 275 nm and a diffraction peak in the XRD patterns at 22°. The effective formation of rGO is further substantiated by a change in the GO peak's properties in the FTIR, EDX, and Raman spectra and a weight loss change in TGA. The SEM and TEM analyses demonstrate the effective production of the nano-sheets of rGO having exfoliated and segregated in a few layers. Furthermore, the obtained rGO exhibited outstanding efficacy in wastewater cleanup, effectively adsorbing MB as a prototype organic dye. The kinetics and isotherm study suggested that the adsorption leads by the chemisorption and monolayer formation on the homogeneous surface of rGO. The maximum adsorption capacity is found to be 89.3 mg g-1. This process offers a fresh opportunity for the economical and safe production of rGO for wastewater treatment.

Scalable Synthesis of Dodecanethiol-Capped Bismuth Nanoparticles by a Solvent-Free Solid-State Grinding Method for Reduction of 4-Nitrophenol to 4-Aminophenol

Thiol-capped metal nanoparticles have two constituents: an inorganic metal and an organic molecule as a shell. Both characters are inbuilt in the structure of the metal thiolate. Herein, we have investigated bismuth dodecanethiolate as a precursor for the synthesis of dodecanethiol-capped bismuth nanoparticles (Bi NPs) by a solid-state grinding method. By using sodium borohydride and bismuth dodecanethiolate, crystalline bismuth nanoparticles are synthesized in a solvent-free environment at room temperature (24 ± 4 °C). Bi NPs are tested for catalytic activity by reducing 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) with an excess of NaBH4. Dodecanethiol-capped bismuth nanoparticles exhibit an efficient reduction of 4-NP to 4-AP within 12 min. Additionally, these nanoparticles remain catalytically active for up to three cycles.

Aboyewa J, Moabelo KL, Sibuyi NRS, Meyer S, Onani MO, Meyer M, Madiehe AM. Anticancer, Antioxidant, and Catalytic Activities of Green Synthesized Gold Nanoparticles Using Avocado Seed Aqueous Extract

Disposal of agricultural waste has a negative impact on the environment and human health and may contribute to the greenhouse effect. The field of nanotechnology could provide alternative solutions to upcycle agricultural wastes in a safer manner into high-end value products. Organic waste from plants contain biomaterials that could serve as reducing and capping agents in the synthesis of nanomaterials with enhanced activities for use in biomedical and environmental applications. Persea americana (avocado) is a fruit with a high nutritional value; however, despite its rich phytochemical profile, its seed is often discarded as waste. Therefore, this study aimed to upcycle avocado seeds through the synthesis of gold nanoparticles (AuNPs) and evaluate their anticancer, antioxidant, and catalytic activities. The biosynthesis of avocado seed extract (AvoSE)-mediated AuNPs (AvoSE-AuNPs) was achieved following the optimization of various reaction parameters, including pH, temperature, extract, and gold salt concentrations. The AvoSE-AuNPs were poly-dispersed and anisotropic, with average core and hydrodynamic sizes of 14 ± 3.7 and 101.39 ± 1.4 nm, respectively. The AvoSE-AuNPs showed excellent antioxidant potential in terms of ferric reducing antioxidant power (343.88 ± 0.001 μmolAAE/L), 2,2-diphenyl-1-picrylhydrazyl (128.80 ± 0.0159 μmolTE/L), and oxygen radical absorbance capacity (1822.02 ± 12.6338 μmolTE/L); significantly reduced the viability of Caco-2 and PC-3 cells in a dose-dependent manner; and efficiently reduced 4-nitrophenol (4-NP) to 4-aminophenol. This study demonstrated how avocado seeds, an agricultural waste, can be used as sources of new bioactive materials for the synthesis of AuNPs, which have excellent antioxidant, anticancer, and catalytic activities, showing AvoSE-AuNPs' versatility in various applications. In addition, the AvoSE-AuNPs exhibited good stability and recyclability during the catalytic activity, which is significant because some of the primary issues with the use of metallic NPs as catalysts are around the cost-effectiveness, recovery, and reusability of the catalyst.

The Biogenic Synthesis of Bimetallic Ag/ZnO Nanoparticles: A Multifunctional Approach for Methyl Violet Photocatalytic Degradation and the Assessment of Antibacterial, Antioxidant, and Cytotoxicity Properties

In this study, bimetallic nanoparticles (NPs) of silver (Ag) and zinc oxide (ZnO) were synthesized using Leptadenia pyrotechnica leaf extract for the first time. Monometallic NPs were also obtained for comparison. The characterization of the prepared NPs was carried out using various techniques, including UV-Visible spectroscopy (UV-Vis), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The latter confirmed the crystalline nature and diameter of the monometallic and bimetallic NPs of Ag and ZnO. The SEM images of the prepared NPs revealed their different shapes. The biological activities of the NPs were evaluated concerning their antibacterial, antioxidant, and cytotoxic properties. The antibacterial activities were measured using the time-killing method. The results demonstrated that both the monometallic and bimetallic NPs inhibited the growth of Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria. The antioxidant activities of the NPs were evaluated using the DPPH (2,2-diphenyl-1-picrylhydrazyl) assay and their cytotoxicity was checked using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. The results indicated that the controlled quantity of the monometallic and bimetallic NPs did not affect the viability of the cells. However, the decreased cell (L-929) viability suggested that the NPs could have anticancer properties. Furthermore, the photocatalytic degradation of methyl violet and 4-nitrophenol was investigated using the prepared Ag/ZnO NPs, examining the factors affecting the degradation process and conducting a kinetic and thermodynamic study. The prepared Ag/ZnO NPs demonstrated good photocatalytic degradation (88.9%) of the methyl violet (rate constant of 0.0183 min^-1) in comparison to 4-nitrophenol (NPh), with a degradation rate of 81.37% and 0.0172 min^-1, respectively. Overall, the bimetallic NPs showed superior antibacterial, antioxidant, cytotoxic, and photocatalytic properties compared to the monometallic NPs of Ag and ZnO.

PDDA induced step-pyramidal growth of nickel-platinum (Ni-Pt) nanoparticles for enhanced 4-nitrophenol reduction

Herein, we report the synthesis of novel platinum-based nanoparticles with step-pyramidal growth induced by poly(diallyldimethylammonium chloride) (PDDA). The complex stepped pyramidal shape became the central point for outstanding catalytic reduction of 4-nitrophenol, overcoming the activity of bare Pt nanoparticles. These results are valuable for the catalytic degradation of reactive molecules.

Bifunctional Polymer Brush Reactor for In Situ Synthesis of Hollow Silica-Supported Gold Nanocatalysts

Gold nanoparticles (AuNPs) on carriers have received wide attention as catalysts as a result of their excellent stability and catalytic performance. Herein, we report the design and synthesis of hollow silica-supported gold nanocatalysts (SNPs@AuNPs) composed of highly dispersed AuNPs with approximately 4.30 nm using an in situ colloidal polyelectrolyte template strategy. The monodisperse polystyrene nanospheres accompanied by poly[(2-methacryloyloxyethyl)trimethylammonium chloride] brushes were first synthesized. Subsequently, the facile polymer-brush-engaged strategy for the synthesis of hollow SNPs@AuNPs involves in situ reduction of AuNPs, hydrolytic condensation of silica, and a chemical etching process. In combination with dynamic light scattering, transmission electron microscopy, small-angle X-ray scattering, X-ray powder diffraction, and Fourier transform infrared spectroscopy, the as-obtained polymer brushes were proven as effective versatile nanoreactors for the synthesis of AuNPs and silica nanoparticles without any catalysts. Benefiting from the structural advantages, the resultant hollow SNPs@AuNPs manifested superior catalytic activity and reusability for the reduction of p-nitrophenol by sodium borohydride in aqueous solution. With a delicate design, we believe that this synthetic strategy can be extended to fabricate multifunctional nanomaterials with diverse compositions, which would be of great interest in catalysis, energy, and many other important domains.

UV assisted synthesis of folic acid functionalized ZnO-Ag hexagonal nanoprisms for efficient catalytic reduction of Cr+6 and 4-nitrophenol

Chemical-based syntheses of metallic nanoparticles (MNPs) has become a major topic of research exploration in the field of nanotechnology. The utilization of folic acid (FA) as stabilizing and capping agent has been reported as a novel route for the synthesis of bimetallic nanomaterials. The present study includes novel research and brief discussion about preparation of UV light assisted ZnO-Ag nanobars (NBs) using FA as stabilizing agent and its catalytic applications on the reduction of organic pollutants (4-NP and Cr⁺⁶) using NBs as a catalyst alongwith ascorbic acid (AA). Analytical techniques including UV-visible spectroscopy, XRD, SEM, EDX and FT-IR were used for the characterizing synthesized ZnO-Ag NBs. Hexagonal structure of ZnO-Ag NBs were found having crystallite size 5.6 nm and SEM studies revealed the nanobar width 33.2 nm and length 133.5 nm. The prepared ZnO-Ag NBs were tested for their catalytic activity for the reduction of 4-nitrophenol (4-NP) and Cr⁺⁶. In the presence of ZnO-Ag NBs and AA, an effective reduction of 4-nitrophenol (4-NP) and Cr⁺⁶ was achieved up to 93% and 90% in 17 and 26 min with respectively. The successful and efficient catalytic activity of NBs may be attributed to the size of NBs or the concentration of FA employed for synthesis.

Antibody-modified Gold Nanobiostructures: Advancing Targeted Photodynamic Therapy for Improved Cancer Treatment

Photodynamic therapy (PDT) is an innovative, non-invasive method of treating cancer that uses light-activated photosensitizers to create reactive oxygen species (ROS). However, challenges associated with the limited penetration depth of light and the need for precise control over photosensitizer activation have hindered its clinical translation. Nanomedicine, particularly gold nanobiostructures, offers promising solutions to overcome these limitations. This paper reviews the advancements in PDT and nanomedicine, focusing on applying antibody-modified gold nanobiostructures as multifunctional platforms for enhanced PDT efficacy and improved cancer treatment outcomes. The size, shape, and composition of gold nanobiostructures can significantly influence their PDT efficacy, making synthetic procedures crucial. Functionalizing the surface of gold nanobiostructures with various molecules, such as antibodies or targeting agents, bonding agents, PDT agents, photothermal therapy (PTT) agents, chemo-agents, immunotherapy agents, and imaging agents, allows composition modification. Integrating gold nanobiostructures with PDT holds immense potential for targeted cancer therapy. Antibody-modified gold nanobiostructures, in particular, have gained significant attention due to their tunable plasmonic characteristics, biocompatibility, and surface functionalization capabilities. These multifunctional nanosystems possess unique properties that enhance the efficacy of PDT, including improved light absorption, targeted delivery, and enhanced ROS generation. Passive and active targeting of gold nanobiostructures can enhance their localization near cancer cells, leading to efficient eradication of tumor tissues upon light irradiation. Future research and clinical studies will continue to explore the potential of gold nanobiostructures in PDT for personalized and effective cancer therapy. The synthesis, functionalization, and characterization of gold nanobiostructures, their interaction with light, and their impact on photosensitizers' photophysical and photochemical properties, are important areas of investigation. Strategies to enhance targeting efficiency and the evaluation of gold nanobiostructures in vitro and in vivo studies will further advance their application in PDT. The integrating antibody-modified gold nanobiostructures in PDT represents a promising strategy for targeted cancer therapy. These multifunctional nanosystems possess unique properties that enhance PDT efficacy, including improved light absorption, targeted delivery, and enhanced ROS generation. Continued research and development in this field will contribute to the advancement of personalized and effective cancer treatment approaches.

Biogenic Synthesis of Copper-Based Nanomaterials Using Plant Extracts and Their Applications: Current and Future Directions

Plants have been used for multiple purposes over thousands of years in various applications such as traditional Chinese medicine and Ayurveda. More recently, the special properties of phytochemicals within plant extracts have spurred researchers to pursue interdisciplinary studies uniting nanotechnology and biotechnology. Plant-mediated green synthesis of nanomaterials utilises the phytochemicals in plant extracts to produce nanomaterials. Previous publications have demonstrated that diverse types of nanomaterials can be produced from extracts of numerous plant components. This review aims to cover in detail the use of plant extracts to produce copper (Cu)-based nanomaterials, along with their robust applications. The working principles of plant-mediated Cu-based nanomaterials in biomedical and environmental applications are also addressed. In addition, it discusses potential biotechnological solutions and new applications and research directions concerning plant-mediated Cu-based nanomaterials that are yet to be discovered so as to realise the full potential of the plant-mediated green synthesis of nanomaterials in industrial-scale production and wider applications. This review provides readers with comprehensive information, guidance, and future research directions concerning: (1) plant extraction, (2) plant-mediated synthesis of Cu-based nanomaterials, (3) the applications of plant-mediated Cu-based nanomaterials in biomedical and environmental remediation, and (4) future research directions in this area.

The identification of byproducts from the catalytic reduction reaction of 4-nitrophenol to 4-aminophenol: A systematic spectroscopic study

Acetaminophenol, commonly recognized as paracetamol (considered safer than aspirin) is formed by nitration of phenol (4-nitrophenol (4-NP)) for its conversion to 4-aminophenol (4-AP), followed by the acetylation for the final product. As 4-NP is an intermediate product in acetaminophenol (paracetamol) production from phenol the dynamic analysis of acetylation of amine group is important. This study focuses on the feasibility of spectroscopic studies to monitor the removal of 4-NP using sodium borohydride (NaBH₄) probe reaction in the presence of silver, gold, and bimetallic Ag/Au nanoparticles. UV-visible absorbance and fluorescence spectroscopy measurements reveal the formation of 1,4-benzoquinone (BQ), hydroquinone (HQ), and phenol (Ph) as the final products, in addition to the formation of typically reported 4-AP. The intermediates of NaBH₄ seem to play a significant role in the formation of BQ, which converts to HQ in the basic medium followed by the formation of phenol in an acidic medium. Complete kinetic analysis with respect to spectroscopic studies of the standard compounds is presented. Similar results were obtained with 4-NP spiked river and seawater samples. The present findings may lead to catalytic benchmarking that can differ from most of the current practices and highlight the importance of adopting a holistic approach towards the fundamental understanding of 4-NP catalytic reduction that must take into account the concentration of NaBH₄ and pH interdependencies.

Monodisperse Gold Nanoparticles: A Review on Synthesis and Their Application in Modern Medicine

Gold nanoparticles (AuNPs) are becoming increasingly popular as drug carriers due to their unique properties such as size tenability, multivalency, low toxicity and biocompatibility. AuNPs have physical features that distinguish them from bulk materials, small molecules and other nanoscale particles. Their unique combination of characteristics is just now being fully realized in various biomedical applications. In this review, we focus on the research accomplishments and new opportunities in this field, and we describe the rising developments in the use of monodisperse AuNPs for diagnostic and therapeutic applications. This study addresses the key principles and the most recent published data, focusing on monodisperse AuNP synthesis, surface modifications, and future theranostic applications. Moving forward, we also consider the possible development of functionalized monodisperse AuNPs for theranostic applications based on these efforts. We anticipate that as research advances, flexible AuNPs will become a crucial platform for medical applications.

Plant-mediated gold and silver nanoparticles as detectors of heavy metal contamination

Heavy metals are dumped into the environment as a result of human activities, posing a serious threat to ecology and human health. Surface water, potable drinking water, potable groundwater, and majority of wastewater include their traces, due to which, their detection by nanoparticles has received a lot of attention in recent years. Although microorganisms are utilised for green nanoparticle production, plant materials have recently been explored because they are more environmentally friendly, easier to scale up, and require fewer specific growth conditions. The production and attributes of nanoparticles synthesized by plant mediation could be enhanced through design of experiments approach, extending their feasibility in the detection of heavy metals in polluted environmental samples. A concise review on green synthesis of silver and gold nanoparticles utilizing plant phytochemicals, its mechanism of synthesis along with significance of design of experiments for enhancement, and their use as heavy metal contamination detectors is presented in the current study.

Latest Trends in Lateral Flow Immunoassay (LFIA) Detection Labels and Conjugation Process

LFIA is one of the most successful analytical methods for various target molecules detection. As a recent example, LFIA tests have played an important role in mitigating the effects of the global pandemic with SARS-COV-2, due to their ability to rapidly detect infected individuals and stop further spreading of the virus. For this reason, researchers around the world have done tremendous efforts to improve their sensibility and specificity. The development of LFIA has many sensitive steps, but some of the most important ones are choosing the proper labeling probes, the functionalization method and the conjugation process. There are a series of labeling probes described in the specialized literature, such as gold nanoparticles (GNP), latex particles (LP), magnetic nanoparticles (MNP), quantum dots (QDs) and more recently carbon, silica and europium nanoparticles. The current review aims to present some of the most recent and promising methods for the functionalization of the labeling probes and the conjugation with biomolecules, such as antibodies and antigens. The last chapter is dedicated to a selection of conjugation protocols, applicable to various types of nanoparticles (GNPs, QDs, magnetic nanoparticles, carbon nanoparticles, silica and europium nanoparticles).

Green Synthesis of Gold Nanoparticles: An Eco-Friendly Approach

By virtue of their unique physicochemical properties, gold nanoparticles (AuNPs) have gained significant interest in a broad range of biomedical applications such as sensors, diagnosis, and therapy. AuNPs are generally synthesized via different conventional physical and chemical methods, which often use harmful chemicals that induce health hazards and pollute the environment. To overcome these issues, green synthesis techniques have evolved as alternative and eco-friendly approaches to the synthesis of environmentally safe and less-expensive nanoparticles using naturally available metabolites from plants and microorganisms such as bacteria, fungi, and algae. This review provides an overview of the advances in the synthesis of AuNPs using different biological resources with examples, and their profound applications in biomedicine. A special focus on the biosynthesis of AuNPs using different medicinal plants and their multifunctional applications in antibacterial, anti-inflammatory, and immune responses are featured. Additionally, the applications of AuNPs in cancer theranostics, including contrast imaging, drug delivery, hyperthermia, and cancer therapeutics, are comprehensively discussed. Moreover, this review will shed light on the importance of the green synthesis approach, and discuss the advantages, challenges, and prospects in this field.

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.

3D printing of recombinant Escherichia coli/Au nanocomposites as agitating paddles towards robust catalytic reduction of 4-nitrophenol

Three-dimensional (3D) printing technology has received remarkable attention in manufacturing catalysts with tailored shapes and high precision, particularly facilitating catalyst recovery, maximizing heat/mass transfer, as well as enhancing catalytic performance. Herein, an engineered recombinant Escherichia coli strain (denoted as e-E. coli) with overexpressing metallothionein (a metal-binding protein) was explored to synthesize Au nanoparticles serving as both reducing and stabilizing agents. Then, the mixed inks containing e-E. coli/Au composite and biocompatible polymers (sodium alginate and gelatin) were extruded based on a direct ink writing method followed by chemical crosslinking to form robust 3D grids with square symmetry. To boost the mass transfer and minimize pressure drop, the monolith catalysts were assembled into agitating paddles and used for liquid-phase batch reactions (volume: 1 L). As such, the reaction solutions were mixed internally via the powered "catalytic paddles" with high mechanical strength, excellent reactivity, and easy recyclability, which could be reused at least 7 cycles without performance loss. Our work provides a novel strategy for the fabrication of supported Au catalysts, and the proof-of-concept "catalytic paddles" by 3D printing technology can be applied to other industrial solution-based reactions.

Biosynthesis of Gold Nanoisotrops Using Carallia brachiata Leaf Extract and Their Catalytic Application in the Reduction of 4-Nitrophenol

The past decade has observed a significant surge in efforts to discover biological systems for the fabrication of metal nanoparticles. Among these methods, plant-mediated synthesis has garnered sizeable attention due to its rapid, cost-effective, environmentally benign single-step procedure. This study explores a step-wise, room-temperature protocol for the synthesis of gold nanoparticles (AuNPs) using Carallia brachiata, a mangrove species from the west coast of Peninsular Malaysia. The effects of various reaction parameters, such as incubation time, metal ion concentration, amount of extract and pH, on the formation of stable colloids were monitored using UV-visible (UV-Vis) absorption spectrophotometry. Our findings revealed that the physicochemical properties of the AuNPs were significantly dependent on the pH. Changing the pH of the plant extract from acidic to basic appears to have resulted in a blue-shift in the main characteristic feature of the surface plasmon resonance (SPR) band, from 535 to 511 nm. The high-resolution-transmission electron microscopy (HR-TEM) and field emission scanning electron microscopy (FESEM) images revealed the morphologies of the AuNPs synthesized at the inherent pH, varying from isodiametric spheres to exotic polygons and prisms, with sizes ranging from 10 to 120 nm. Contrarily, an optimum pH of 10 generated primarily spherical-shaped AuNPs with narrower size distribution (8-13 nm). The X-ray diffraction (XRD) analysis verified the formation of AuNPs as the diffraction patterns matched well with the standard value of a face-centered cubic (FCC) Au lattice structure. The Fourier-transform infrared (FTIR) spectra suggested that different functional groups are involved in the biosynthetic process, while the phytochemical test revealed a clear role of the phenolic compounds. The reduction of 4-nitrophenol (4-NP) was selected as the model reaction for evaluating the catalytic performance of the green-synthesized AuNPs. The catalytic activity of the small, isotropic AuNPs prepared using basic aqueous extract was more effective than the nanoanisotrops, with more than 90% of 4-NP conversion achieved in under an hour with just 3 mg of the nanocatalyst.

Gums-based engineered bio-nanostructures for greening the 21st-century biotechnological settings

Naturally occurring plant-based gums and their engineered bio-nanostructures have gained an immense essence of excellence in several industrial, biotechnological, and biomedical sectors of the modern world. Gums derived from bio-renewable resources that follow green chemistry principles are considered green macromolecules with unique structural and functional attributes. For instance, gum mostly obtained as exudates are bio-renewable, bio-degradable, bio-compatible, sustainable, overall cost-effective, and nontoxic. Gum exudates also offer tunable attributes that play a crucial role in engineering bio-nanostructures of interest for several bio- and non-bio applications, e.g., food-related items, therapeutic molecules, sustained and controlled delivery cues, bio-sensing constructs, and so on. With particular reference to plant gum exudates, this review focuses on applied perspectives of various gums, i.e., gum Arabic, gum albizzia, gum karaya, gum tragacanth, and gum kondagogu. After a brief introduction with problem statement and opportunities, structural and physicochemical attributes of plant-based natural gums are presented. Following that, considerable stress is given to green synthesis and stabilization of gum-based bio-nanostructures. The final part of the review focuses on the bio- and non-bio related applications of various types of gums polysaccharides-oriented bio-nanostructures.

Reduction of 4-nitrophenol using green-fabricated metal nanoparticles

Noble metal (silver (Ag), gold (Au), platinum (Pt), and palladium (Pd)) nanoparticles have gained increasing attention due to their importance in several research fields such as environmental and medical research. This review focuses on the basic perceptions of the green synthesis of metal nanoparticles and their supported-catalyst-based reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). The mechanisms for the formation of these nanoparticles and the catalytic reduction of 4-NP are discussed. Furthermore, the parameters that need to be considered in the catalytic efficiency calculations and perspectives for future studies are also discussed.

Noble metal (silver (Ag), gold (Au), platinum (Pt), and palladium (Pd)) nanoparticles have gained increasing attention due to their importance in several research fields such as environmental and medical research.

Cinnamomum verum-derived bioactives-functionalized gold nanoparticles for prevention of obesity through gut microbiota reshaping

Existing drugs have limited success in managing obesity in human due to their low efficacy and severe side-effects. Surface-modified gold nanoparticles have now received considerable attention of researchers for efficient biomedical applications owing to their superior uptake by cells, biocompatibility, hydrophilicity and non-immunogenicity. Here we prepared Cinnamomum verum derived bioactives-functionalized gold nanoparticles (Au@P-NPs) and assessed their impact on obesity and related immune-metabolic complications in high-fat diet (HFD)-induced obese mice using metabolic experiments along with 16S RNA gene-based gut microbial profiling and faecal microbiota transplantation (FMT). Au@P-NPs treatment prevented weight gain, decreased fat deposition, reduced metabolic inflammation and endotoxaemia in HFD-fed mice. Au@P-NPs-treated group exhibited better glucose tolerance and insulin sensitivity than HFD-fed control mice, and got completely protected against hepatic steatosis. These impacts were related to increased energy expenditure and enhanced Ucp1 expression in the brown adipose tissues of Au@P-NPs-administered animals, which strongly linked with the mRNA expression of the membrane bile acid receptor TGR5. Treatment of HFD-fed animals with Au@P-NPs altered plasma bile acid profile, and increased Akkermansia muciniphila and decreased Lactobacillus populations in the faeces. Au@P-NPs-treated animals revealed altered plasma bile acid profile, and increased Akkermansia muciniphila and decreased Lactobacillus populations in the faeces. FMT experiments showed lesser weight gain and greater energy expenditure in the mice fed with faecal suspension from Au@P-NPs-treated animals than that from HFD-fed mice. These results clearly establish that gold nanoparticles functionalized with bioactive compounds of C. verum have high potential to be an anti-obesity drug.

Molecular intervention of colon cancer and inflammation manifestation by tannin capped biocompatible controlled sized gold nanoparticles from Terminalia bellirica: A green strategy for pharmacological drug formulation based on nanotechnology principles

Among the diverse nanomaterials, gold nanoparticles (AuNps) are utilised for various therapeutic application due to the distinct physical, chemical properties and biocompatibility. Synthesis of gold nanoparticles using plants is the promising route. This method is low cost, eco-friendly and higher biological activities. In this present study, Gold nanoparticles were synthesised from fruit extract of Terminalia bellirica fruit extract. Their anticancer and anti-inflammatory activity was evaluated against colorectal cancer cell line (HT29) and TNBS-induced zebrafish model. Highly stable tannin capped gold nanoparticles were synthesised from fruit extract broth of Terminalia bellirica rapidly. Structural and functional properties of the synthesised nanoparticles were studied by Fourier transform infrared spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM) equipped with energy-dispersive atomic X-ray spectroscopy (EDAX) and X-ray diffraction (XRD). All the characterisation studies reveal highly stable, crystalline, phytochemicals, mainly tannin doped, spherical, 28 nm controlled sized gold nanoparticles. The molecular mechanism of anticancer activity was studied by determining cancer markers' expression, which was studied using quantitative real-time polymerase chain reaction (qPCR). Antioxidative enzymes' status and apoptosis changes were also investigated. Synthesised nanoparticles brought a drastic reduction of all the tested cancer markers' expression. Notable changes in antioxidative enzymes' status and a good sign of apoptosis were observed in nanoparticles' treatment. The anti-inflammatory activity was studied against TNBS-induced zebrafish model, which was confirmed by determining inflammatory markers' expression TNF-α, iNOS (induced Nitric Oxide Synthase) and histopathological examination. Nanoparticles' treatment recorded a drastic reduction of inflammatory markers' expression. No marked sign of inflammation was also observed in histopathological analysis of the nanoparticles' treatment group. The present study suggests the possible utilisation of T. bellirica-mediated gold nanoparticles as an effective therapeutic agent against a prolonged inflammatory disease that progressively develops into cancer.

Reduction of 4-nitrophenol Mediated by Silver Nanoparticles Synthesized using Aqueous Leaf Extract of Peronema canescens

In this study, we developed an alternative of 4-nitrophenol reduction mediated by silver nanoparticles (AgNPs) which was synthesized using aqueous extract of the Peronema canescens leaf through an eco-friendly approach. The reducing 4-nitrophenol to 4-aminophenol mediated by AgNPS in the presence of sodium borohydride as a hydrogen source proceeded rapidly at room temperature without any additional treatments. The AgNPS synthesis was simple and was carried out under mild conditions. Ultraviolet–visible spectroscopy was performed to examine the properties of the obtained AgNPs, which displayed an absorption peak at 431 nm. A transmission electron microscopy analysis revealed that the AgNPs were spherical in shape and had an average particle size of 19 nm as determined by particle size analysis. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Plasmonic Gold Nanoparticles (AuNPs): Properties, Synthesis and their Advanced Energy, Environmental and Biomedical Applications

Inducing plasmonic characteristics, primarily localized surface plasmon resonance (LSPR), in conventional AuNPs through particle size and shape control could lead to a significant enhancement in electrical, electrochemical, and optical properties. Synthetic protocols and versatile fabrication methods play pivotal roles to produced plasmonic gold nanoparticles (AuNPs), which can be employed in multipurpose energy, environmental and biomedical applications. The main focus of this review is to provide a comprehensive and tutorial overview of various synthetic methods to design highly plasmonic AuNPs, along with a brief essay to understand the experimental procedure for each technique. The latter part of the review is dedicated to the most advanced and recent solar-induced energy, environmental and biomedical applications. The synthesis methods are compared to identify the best possible synthetic route, which can be adopted while employing plasmonic AuNPs for a specific application. The tutorial nature of the review would be helpful not only for expert researchers but also for novices in the field of nanomaterial synthesis and utilization of plasmonic nanomaterials in various industries and technologies.

Preparation, Functionalization, Modification, and Applications of Nanostructured Gold: A Critical Review

Gold nanoparticles (Au NPs) play a significant role in science and technology because of their unique size, shape, properties and broad range of potential applications. This review focuses on the various approaches employed for the synthesis, modification and functionalization of nanostructured Au. The potential catalytic applications and their enhancement upon modification of Au nanostructures have also been discussed in detail. The present analysis also offers brief summaries of the major Au nanomaterials synthetic procedures, such as hydrothermal, solvothermal, sol-gel, direct oxidation, chemical vapor deposition, sonochemical deposition, electrochemical deposition, microwave and laser pyrolysis. Among the various strategies used for improving the catalytic performance of nanostructured Au, the modification and functionalization of nanostructured Au produced better results. Therefore, various synthesis, modification and functionalization methods employed for better catalytic outcomes of nanostructured Au have been summarized in this review.

Simplification of gold nanoparticle synthesis with low cytotoxicity using a greener approach: opening up new possibilities

Gold nanoparticles (AuNPs) have diverse applications in the diagnosis and treatment of ailments. This study describes an extremely simplified synthesis of AuNPs using antioxidant-rich pollen extract as a local natural source. Ultraviolet-visible (UV-vis) spectroscopy, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM) were used to characterize the synthesized AuNPs; strong UV-vis absorption at 534 nm confirmed their formation, the XRD pattern showed the presence of a crystalline structure, and TEM images showed them to be spherical nanoparticles with an average size of 9.3 ± 2.9 nm. As synthesized AuNPs remained stable for up to two months under laboratory conditions without any sedimentation or change in the absorption value, presumably due to the protection afforded by the capping agents from pollen. AuNPs revealed low toxicity effects on MCF-7 and HUVECs cell lines (with an IC50 value of ∼400 μg mL-1 for both the cell lines). The proposed method did not use any hazardous materials or high-energy consuming devices; thus this efficient protocol may be adapted for large-scale production using local resources.

Addressing Antimicrobial Resistance Through Nanoantibiotics

In recent years, the irrational use of antibiotics has escalated the evolution of multidrug-resistant (MDR) bacterial strains. The infectious diseases caused by these MDR bacterial strains remain a major threat to human health and have emerged as the leading cause of morbidity and mortality. The WHO and CDC have expressed serious concern regarding the continued increase in the development of multidrug resistance among bacteria. The antimicrobial resistance (AMR) poses a severe global threat of growing concern to human health and economic burden. Bacteria have developed the ability to resist antimicrobials by altering target site/enzyme, inactivation of the enzyme, decreasing cell permeability, increasing efflux due to over-expression of efflux pumps, target protection, target overproduction, and many other ways. The shortage of new antimicrobials and rapid rise in antibiotic resistance demands pressing need to develop alternate antibacterial agents.

A Review on the Synthesis and Functionalization of Gold Nanoparticles as a Drug Delivery Vehicle

Metal nanoparticles are being extensively used in biomedical fields due to their small size-to-volume ratio and extensive thermal stability. Gold nanoparticles (AuNPs) are an obvious choice for biomedical applications due to their amenability of synthesis, stabilization, and functionalization, low toxicity, and ease of detection. In the past few decades, various chemical methods have been used for the synthesis of AuNPs, but recently, newer environment friendly green approaches for the synthesis of AuNPs have gained attention. AuNPs can be conjugated with a number of functionalizing moieties including ligands, therapeutic agents, DNA, amino acids, proteins, peptides, and oligonucleotides. Recently, studies have shown that gold nanoparticles not only infiltrate the blood vessels to reach the site of tumor but also enter inside the organelles, suggesting that they can be employed as effective drug carriers. Moreover, after reaching their target site, gold nanoparticles can release their payload upon an external or internal stimulus. This review focuses on recent advances in various methods of synthesis of AuNPs. In addition, strategies of functionalization and mechanisms of application of AuNPs in drug and bio-macromolecule delivery and release of payloads at target site are comprehensively discussed.

Functionalization of Gold Nanoparticles by Inorganic Entities

The great affinity of gold surface for numerous electron-donating groups has largely contributed to the rapid development of functionalized gold nanoparticles (Au-NPs). In the last years, a new subclass of nanocomposite has emerged, based on the association of inorganic molecular entities (IME) with Au-NPs. This highly extended and diversified subclass was promoted by the synergy between the intrinsic properties of the shell and the gold core. This review-divided into four main parts-focuses on an introductory section of the basic notions related to the stabilization of gold nanoparticles and defines in a second part the key role played by the functionalizing agent. Then, we present a wide range of inorganic molecular entities used to prepare these nanocomposites (NCs). In particular, we focus on four different types of inorganic systems, their topologies, and their current applications. Finally, the most recent applications are described before an overview of this new emerging field of research.