Growth of gold nanoparticles in human cells

Intratumoral Biosynthesis of Gold Nanoclusters by Pancreatic Cancer to Overcome Delivery Barriers to Radiosensitization

Nanoparticle delivery to solid tumors is a prime challenge in nanomedicine. Here, we approach this challenge through the lens of biogeochemistry, the field that studies the flow of chemical elements within ecosystems as manipulated by living cellular organisms and their environments. We leverage biogeochemistry concepts related to gold cycling against pancreatic cancer, considering mammalian organisms as drivers for gold nanoparticle biosynthesis. Sequestration of gold nanoparticles within tumors has been demonstrated as an effective strategy to enhance radiotherapy; however, the desmoplasia of pancreatic cancer impedes nanoparticle delivery. Our strategy overcomes this barrier by applying an atomic-scale agent, ionic gold, for intratumoral gold nanoparticle biosynthesis. Our comprehensive studies showed the cancer-specific synthesis of gold nanoparticles from externally delivered gold ions in vitro and in a murine pancreatic cancer model in vivo; a substantial colocalization of gold nanoparticles (GNPs) with cancer cell nuclei in vitro and in vivo; a strong radiosensitization effect by the intracellularly synthesized GNPs; a uniform distribution of in situ synthesized GNPs throughout the tumor volume; a nearly 40-day total suppression of tumor growth in animal models of pancreatic cancer treated with a combination of gold ions and radiation that was also associated with a significantly higher median survival versus radiation alone (235 vs 102 days, respectively).

Evaluation of the parameters affecting the loading of anticancer drug Paclitaxel on coated gold nanoparticles for breast cancer treatment

The purpose of this study is the design and synthesis of gold nanoparticles (GNPs) conjugated with paclitaxel and to investigate the parameters affecting the stability of synthesised nanoparticles with drug delivery capability. Here, synthesised GNPs were coated with polyethylene glycol. Then these particles were conjugated with paclitaxel under different conditions and the physical and structural characteristics, as well as the factors affecting the loading of paclitaxel on nanoparticles, were evaluated by ultraviolet spectrophotometer, fourier transform infrared spectroscopy, transmission electron microscopy, dynamic light scattering and zeta potential apparatus. It was found that pegylated GNPs have a limited loading capacity at the time of 24 h of incubation and the Paclitaxel loading was observed to be pH dependent. The use of these particles in the treatment of breast cancer (MCF7) was also investigated using the MTT test. It was determined that the survival percentage of MCF7 cells in the presence of paclitaxel-bound nanoparticles decreases to about 55% at the maximum measured concentration (690 μM).

Prospecting Cellular Gold Nanoparticle Biomineralization as a Viable Alternative to Prefabricated Gold Nanoparticles

Gold nanoparticles (GNPs) have shown considerable potential in a vast number of biomedical applications. However, currently there are no clinically approved injectable GNP formulations. Conversely, gold salts have been used in the clinic for nearly a century. Further, there is evidence of GNP formation in patients treated with gold salts (i.e., chrysiasis). Recent reports evaluating this phenomenon in human cells and in murine models indicate that the use of gold ions for in situ formation of theranostic GNPs could greatly improve the delivery within dense biological tissues, increase efficiency of intracellular gold uptake, and specificity of GNP formation within cancer cells. These attributes in combination with safe clinical application of gold salts make this process a viable strategy for clinical translation. Here, the first summary of the current knowledge related to GNP biomineralization in mammalian cells is provided along with critical assessment of potential biomedical applications of this newly emergent field.

Biosynthesis of Gold Nanoparticles by Vascular Cells in vitro

Biosynthesis of gold nanoparticles (AuNPs) for antimicrobial and chemotherapeutic applications is a well-established process in microbial hosts such as bacterial, fungi, and plants. However, reports on AuNPs biosynthesis in mammalian cells are scarce. In this study, bovine aortic endothelial cells (BAECs) and bovine aortic smooth muscle cells (BASMCs) were examined for their ability to synthesize AuNPs in vitro. Cell culture conditions such as buffer selection, serum concentration, and HAuCl4 concentration were optimized before the biosynthesized AuNPs were characterized through visible spectrometry, transmission electron microscopy, X-ray diffraction, and Fourier transform infrared (FTIR) spectroscopy. BAECs and BASMC produced small, spherical AuNPs that are semi-crystalline with a similar diameter (23 ± 2 nm and 23 ± 4 nm). Hydrogen peroxide pretreatment increased AuNPs synthesis, suggesting that antioxidant enzymes may reduce Au3+ ions as seen in microbial cells. However, buthionine sulfoximine inhibition of glutathione synthesis, a key regulator of oxidative stress, failed to affect AuNPs generation. Taken together, these results show that under the right synthesis conditions, non-tumor cell lines can produce detectable concentrations of AuNPs in vitro.

Surface enhanced Raman scattering for probing cellular biochemistry

Surface enhanced Raman scattering (SERS) from biomolecules in living cells enables the sensitive, but also very selective, probing of their biochemical composition. This minireview discusses the developments of SERS probing in cells over the past years from the proof-of-principle to observe a biochemical status to the characterization of molecule-nanostructure and molecule-molecule interactions and cellular processes that involve a wide variety of biomolecules and cellular compartments. Progress in applying SERS as a bioanalytical tool in living cells, to gain a better understanding of cellular physiology and to harness the selectivity of SERS, has been achieved by a combination of live cell SERS with several different approaches. They range from organelle targeting, spectroscopy of relevant molecular models, and the optimization of plasmonic nanostructures to the application of machine learning and help us to unify the information from defined biomolecules and from the cell as an extremely complex system.

Silver Nanoparticle Production Mediated by Vitis vinifera Cane Extract: Characterization and Antibacterial Activity Evaluation

The ever-growing range of possible applications of nanoparticles requires their mass production. However, there are problems resulting from the prevalent methods of nanoparticle production; physico-chemical routes of nanoparticle synthesis are not very environmentally friendly nor cost-effective. Due to this, the scientific community started exploring new methods of nanoparticle assembly with the aid of biological agents. In this study, ethanolic Vitis vinifera cane extract combined with silver nitrate was used to produce silver nanoparticles. These were subsequently characterized using UV-visible (UV-Vis) spectrometry, transmission electron microscopy, and dynamic light-scattering analysis. The antimicrobial activity of produced nanoparticles was tested against the planktonic cells of five strains of Gram-negative bacterium Pseudomonas aeruginosa (PAO1, ATCC 10145, ATCC 15442, DBM 3081, and DBM 3777). After that, bactericidal activity was assessed using solid medium cultivation. In the end, nanoparticles’ inhibitory effect on adhering cells was analyzed by measuring changes in metabolic activity (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay-MTT). Our results confirmed that ethanolic Vitis vinifera cane extract is capable of mediating silver nanoparticle production; synthesis was conducted using 10% of extract and 1 mM of silver nitrate. The silver nanoparticles’ Z-average was 68.2 d nm, and their zeta potential was –30.4 mV. These silver nanoparticles effectively inhibited planktonic cells of all P. aeruginosa strains in concentrations less than 5% v/v and inhibited biofilm formation in concentrations less than 6% v/v. Moreover, minimum bactericidal concentration was observed to be in the range of 10–16% v/v. According to the results in this study, the use of wine agriculture waste is an ecological and economical method for the production of silver nanoparticles exhibiting significant antimicrobial properties.

Anti-excitotoxicity and neuroprotective action of asiaticoside encapsulated polymeric nanoparticles in pilocarpine rodent seizure model

Asiaticoside (ASI), an ursane-type triterpenoid saponin, isolated from the memory enhancing herb Centella asiatica, is known for its neuroprotective activities. Here the anti-excitotoxicity and neuro protective effects of ASI encapsulated alginate chitosan nanoparticles (ACNPs) were evaluated in pilocarpine (PC) induced seizure in mice model. ACNPs were prepared by ionic gelation-polyelectrolyte complex method and their physicochemical characterization was carried out by TEM, SEM, DLS, XRD and FT-IR. Subsequently their encapsulation efficiency (EE), in vitro drug release, cell viability, seizure score, DNA fragmentation and mRNA expression of regulatory stress markers were evaluated. Membrane permeability of ACNPs in brain, histopathology and biological TEM and SEM analyses were also carried out. TEM of ACNPs showed spherical morphology with a particle size of 200-400 nm. DLS of ACNPs displayed an average size of 486.2 nm with polydispersity index (PDI) of 0.567 and zeta potential of -14.1 mV. ACNPs achieved high EE (> 90%) and controlled release (10%). Biological evaluation studies revealed ACNPs as non-toxic to mouse neural stem cells (mNSCs). They displayed enhanced brain permeability and attenuated seizure. Our results confirmed ACNPs as effective in crossing the brain membrane barrier and mitigating seizure severity induced by PC.

Cell-Derived Biogenetic Gold Nanoparticles for Sensitizing Radiotherapy and Boosting Immune Response against Cancer

The biosynthesis of nanomedicine has gained enormous attention and exhibited promising prospects, while the underlying mechanism and advantage remain not fully understood. Here, a cell-reactor based on tumor cells is developed to obtain biogenetic gold nanoparticles (Au@MC38) for sensitizing radiotherapy and boosting immune responses. It demonstrates that the intracellular biomineralization and exocytosis process of Au@MC38 can be regulated by the cellular metabolites level and other factors, such as glutathione and reactive oxygen species (ROS), autophagy, and UV irradiation. The elucidation of mechanisms may promote the understanding of interaction principles between nanoparticles and biosystems in the process of biosynthesis. Combined with radiotherapy, Au@MC38 strengthens the radiation-induced DNA damage and ROS generation, thus aggravating cell apoptosis and necrosis. Benefiting from homologous targeting and transcytosis effect, Au@MC38 demonstrates good tumor distribution. Local radiation-induced immunogenic cell death initiates an effective immune response. Especially, CD8a⁺ dendritic cells are significantly increased in mice that received combinatorial treatment. This radio-sensitization strategy has demonstrated the effective inhibition on primary and metastatic tumors, and achieved satisfactory survival benefit in combinatorial with immune checkpoint blockade. Thus, this bio-inspired synthetic strategy may impulse the development of biosynthesis and its therapeutic applications, contributing to a non-invasive and efficient modality for nanomedicine exploitation.

A Simplistic Single-Step Method for Preparing Biomimetic Nanoparticles from Endogenous Biomaterials

Many works utilize products isolated from nature as capping agents to functionalize gold nanoparticles for targeting and therapeutic applications. Some of the most advanced of these strategies utilize complex multicomponent biomaterials, such as whole cell-membranes, for nanoparticle functionalization strategies for evading or initializing immune response as well as for targeting. Strategies like these, wherein whole cell membrane is utilized for functionalization, take advantage of the complexity of the protein-lipid content and organization, which cells normally use for communication and interaction (instilling these capacities to nanoparticle vectors). Many approaches for achieving this in functionalizing the surface of nanoparticles rely on multistep processes, which necessitate the addition and then removal of synthetic molecules, heating, or pH modifications. These processes can have deleterious modifying effects on the functionalizing biomolecules, resulting in loss of product and time during each purification step, as well as potentially changing the biomolecule functionality toward a nondesirable effect. Here, we describe methods for forming gold nanoparticles at room temperature in a single step, functionalized with proteins, using nicotinamide adenine dinucleotide (NADH). This process enables formation of nanoparticles that can be functionalized by individual proteins (demonstrated with FBS) or whole cells membrane (extracted from B16F10 cells). This work is derivative from observations found in the literature by us and others, that mammalian cells are capable of producing gold nanoparticles from ionic gold without the supplementation of chemical species. The products of this single-step synthesis described herein have been optimized to maintain biomolecule integrity and so that there are no further purification steps required. To characterize the nanoparticles in terms of their shape, size, surface functionality, and biomolecule integrity throughout development, we employed light-based spectroscopy techniques, molecular modeling, electron microscopy, light scattering, and gel electrophoresis techniques. In order to compare the optimized biomolecule-functionalized nanoparticles against current standards (which require synthetic linkers, heating, or pH manipulation), we employed metabolic and live/dead assays as well as light-based microscopy/spectroscopy in vitro. In comparing our synthetic process against others for forming gold nanoparticles functionalized with complex biomolecule components (whole-cell membrane), we found that this process had superior particle internalization. Our strategy has similar outlets for application to these other works, however, because this process is entirely reliant on endogenous biomaterials and has additional potential.

Single cell detection using intracellularly-grown-Au-nanoparticle based surface-enhanced Raman scattering spectroscopy for nasopharyngeal cell line classification

The aim of this study was to evaluate the feasibility of applying intracellularly-grown-Au-nanoparticle (IGAuNP)-based surface-enhanced Raman scattering (SERS) technology to classify two types of nasopharyngeal cancer (NPC) cell lines (CNE2 and CNE1). The IGAuNP technology provides excellent delivery efficiency of Au NPs to the cytoplasm and nucleus, thus leading to an extraordinary enhancement of the Raman signals of cells. Compared with normal Raman scattering (NRS) spectra of cells, IGAuNP-based SERS spectra not only have a high signal-to-noise ratio, but also can detect more characteristic Raman peaks, which can be used to explore more differences when comparing the biochemical components of different nasopharyngeal carcinoma cell lines. Based on the linear discriminant analysis (LDA) and support vector machine (SVM) analysis of SERS spectral data, an exciting result with a diagnostic sensitivity of 100%, specificity of 100%, and accuracy of 100%, could be achieved to differentiate CNE2 and CNE1 cells, which is better than the result obtained by NRS spectroscopy. This exploratory study indicated that the SERS technology based on IGAuNPs in conjunction with multivariate statistical analysis methods has great potential in the identification of nasopharyngeal carcinoma cell lines.

Design and Encapsulation of Immunomodulators onto Gold Nanoparticles in Cancer Immunotherapy

The aim of cancer immunotherapy is to reactivate autoimmune responses to combat cancer cells. To stimulate the immune system, immunomodulators, such as adjuvants, cytokines, vaccines, and checkpoint inhibitors, are extensively designed and studied. Immunomodulators have several drawbacks, such as drug instability, limited half-life, rapid drug clearance, and uncontrolled immune responses when used directly in cancer immunotherapy. Several strategies have been used to overcome these limitations. A simple and effective approach is the loading of immunomodulators onto gold-based nanoparticles (GNPs). As gold is highly biocompatible, GNPs can be administered intravenously, which aids in increasing cancer cell permeability and retention time. Various gold nanoplatforms, including nanospheres, nanoshells, nanorods, nanocages, and nanostars have been effectively used in cancer immunotherapy. Gold nanostars (GNS) are one of the most promising GNP platforms because of their unusual star-shaped geometry, which significantly increases light absorption and provides high photon-to-heat conversion efficiency due to the plasmonic effect. As a result, GNPs are a useful vehicle for delivering antigens and adjuvants that support the immune system in killing tumor cells by facilitating or activating cytotoxic T lymphocytes. This review represents recent progress in encapsulating immunomodulators into GNPs for utility in a cancer immunotherapeutic regimen.

Tumor-targeting inorganic nanomaterials synthesized by living cells

Inorganic nanomaterials (NMs) have shown potential application in tumor-targeting theranostics, owing to their unique physicochemical properties. Some living cells in nature can absorb surrounding ions in the environment and then convert them into nanomaterials after a series of intracellular/extracellular biochemical reactions. Inspired by that, a variety of living cells have been used as biofactories to produce metallic/metallic alloy NMs, metalloid NMs, oxide NMs and chalcogenide NMs, which are usually automatically capped with biomolecules originating from the living cells, benefitting their tumor-targeting applications. In this review, we summarize the biosynthesis of inorganic nanomaterials in different types of living cells including bacteria, fungi, plant cells and animal cells, accompanied by their application in tumor-targeting theranostics. The mechanisms involving inorganic-ion bioreduction and detoxification as well as biomineralization are emphasized. Based on the mechanisms, we describe the size and morphology control of the products via the modulation of precursor ion concentration, pH, temperature, and incubation time, as well as cell metabolism by a genetic engineering strategy. The strengths and weaknesses of these biosynthetic processes are compared in terms of the controllability, scalability and cooperativity during applications. Future research in this area will add to the diversity of available inorganic nanomaterials as well as their quality and biosafety.

Green nanomedicine: the path to the next generation of nanomaterials for diagnosing brain tumors and therapeutics?

Introduction: Current brain cancer treatments, based on radiotherapy and chemotherapy, are sometimes successful, but they are not free of drawbacks.Areas covered: Traditional methods for the treatment of brain tumors are discussed here with new solutions presented, among which the application of nanotechnology has demonstrated promising results over the past decade. The traditional synthesis of nanostructures, which relies on the use of physicochemical methodologies are discussed, and their associated concerns in terms of environmental and health impact due to the production of toxic by-products, need for toxic catalysts, and their lack of biocompatibility are presented. An overview of the current situation for treating brain tumors using nanotechnological-based approaches is introduced, and some of the latest advances in the application of green nanomaterials (NMs) for the effective targeting of brain tumors are presented.Expert opinion: Green nanotechnology is introduced as a potential solution to toxic NMs through the application of environmentally friendly and cost-effective protocols using living organisms and biomolecules. The current status of this field, such as those involving clinical trials, is included, and the possible limitations of green-NMs and potential ways to avoid those limitations are discussed so that the field can potentially evolve.

Unmodified Titanium Dioxide Nanoparticles as a Potential Contrast Agent in Photon Emission Computed Tomography

Highly crystalline titanium dioxide nanoparticles (TiO2-NPs) are synthesized via a simple hydrothermal technique. After structural and compositional analysis, the as-synthesized unmodified TiO2-NPs are tested for improvement in two modes of kilovoltage radiation therapy and single-photon emission computed tomography (SPECT)/computed tomography (CT). Our results show that the unmodified TiO2-NPs provide an observable enhancement in CT scan image contrast ranging from 0 ± 3 HU (without NPs) to 283.7 ± 3 HU (0.23 g/mL). TiO2-NPs has excellent biocompatibility, selective uptake at target sites, and reduced toxicity. The unmodified TiO2-NPs as a contrast agent can significantly improve the existing methods of diagnosing and treating cancer.

Intracellular mineralization of gold nanoparticles using gold ion-binding peptides with cell-penetrating ability

We developed a system to directly produce gold nanoparticles in cells by intracellular mineralization in lower concentration than conventional methods using a peptide consisting of a cell-penetrating sequence and a gold ion-binding sequence. Furthermore, we could control the uniquely shaped gold nanostructures that were produced by changing peptide structures.

Intratumoral generation of photothermal gold nanoparticles through a vectorized biomineralization of ionic gold

Various cancer cells have been demonstrated to have the capacity to form plasmonic gold nanoparticles when chloroauric acid is introduced to their cellular microenvironment. But their biomedical applications are limited, particularly considering the millimolar concentrations and longer incubation period of ionic gold. Here, we describe a simplistic method of intracellular biomineralization to produce plasmonic gold nanoparticles at micromolar concentrations within 30 min of application utilizing polyethylene glycol as delivery vector for ionic gold. We have characterized this process for intracellular gold nanoparticle formation, which progressively accumulates proteins as the ionic gold clusters migrate to the nucleus. This nano-vectorized application of ionic gold emphasizes its potential biomedical opportunities while reducing the quantity of ionic gold and required incubation time. To demonstrate its biomedical potential, we further induce in-situ biosynthesis of gold nanoparticles within MCF7 tumor mouse xenografts which is followed by its photothermal remediation.

Blood-brain barrier amenable gold nanoparticles biofabrication in aged cell culture medium

Green fabrication of nanoscale materials is highly desirable because of associated adverse effects with conventional nanomaterial biomedical applications. Moreover, the higher selective nature of the blood-brain barrier (BBB) limits the brain ailments treatment through conventional chemotherapy, thus providing room for nanotechnology-based modalities for BBB traversing. In this contribution, we have biosynthesized gold nanoparticles from the HAuCl4 solution in the aged cells culture medium. This approach is highly facile without any other chemical utilization. The cell culture medium age and cell number can tune the Au nanoparticles (AuNPs) size from 2 to several hundred nm. The 24 h MTT assay and cell uptake studies in vitro and murine models' vital organs (liver, kidney, spleen, lung, and heart) study up to 48 h demonstrated that biosynthesized AuNPs were biocompatible and BBB amenable. Interestingly, the transferrin and cell culture medium isolated proteins were found factors responsible for HAuCl4 solution biomineralization and size control. Moreover, the protein corona on biosynthesized AuNPs could help them traverse BBB both in vitro and in vivo, suggesting their potential applications for brain disease theranostics. In conclusion, the biosynthesis of AuNPs from aged cells medium is highly facile, green, and biocompatible for brain disease theranostics.

In Vivo Biosynthesis of Inorganic Nanomaterials Using Eukaryotes-A Review

Bionanotechnology, the use of biological resources to produce novel, valuable nanomaterials, has witnessed tremendous developments over the past two decades. This eco-friendly and sustainable approach enables the synthesis of numerous, diverse types of useful nanomaterials for many medical, commercial, and scientific applications. Countless reviews describing the biosynthesis of nanomaterials have been published. However, to the best of our knowledge, no review has been exclusively focused on the in vivo biosynthesis of inorganic nanomaterials. Therefore, the present review is dedicated to filling this gap by describing the many different facets of the in vivo biosynthesis of nanoparticles (NPs) using living eukaryotic cells and organisms-more specifically, live plants and living biomass of several species of microalgae, yeast, fungus, mammalian cells, and animals. It also highlights the strengths and weaknesses of the synthesis methodologies and the NP characteristics, bio-applications, and proposed synthesis mechanisms. This comprehensive review also brings attention to enabling a better understanding between the living organisms themselves and the synthesis conditions that allow their exploitation as nanobiotechnological production platforms as these might serve as a robust resource to boost and expand the bio-production and use of desirable, functional inorganic nanomaterials.

Biogenic Gold Nanoparticles as Potent Antibacterial and Antibiofilm Nano-Antibiotics against Pseudomonas aeruginosa

Plant-based synthesis of eco-friendly nanoparticles has widespread applications in many fields, including medicine. Biofilm—a shield for pathogenic microorganisms—once formed, is difficult to destroy with antibiotics, making the pathogen resistant. Here, we synthesized gold nanoparticles (AuNPs) using the stem of an Ayurvedic medicinal plant, Tinospora cordifolia, and studied the action of AuNPs against Pseudomonas aeruginosa PAO1 biofilm. The synthesized AuNPs were characterized by techniques such as ultraviolet-visible spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, energy-dispersive X-ray diffraction, X-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy. The AuNPs were spherically shaped with an average size of 16.1 nm. Further, the subminimum inhibitory concentrations (MICs) of AuNPs (50, 100, and 150 µg/mL) greatly affected the biofilm-forming ability of P. aeruginosa, as observed by crystal violet assay and SEM, which showed a decrease in the number of biofilm-forming cells with increasing AuNP concentration. This was further justified by confocal laser scanning microscopy (CLSM), which showed irregularities in the structure of the biofilm at the sub-MIC of AuNPs. Further, the interaction of AuNPs with PAO1 at the highest sub-MIC (150 µg/mL) showed the internalization of the nanoparticles, probably affecting the tendency of PAO1 to colonize on the surface of the nanoparticles. This study suggests that green-synthesized AuNPs can be used as effective nano-antibiotics against biofilm-related infections caused by P. aeruginosa.

New avenues of controlling microbial infections through anti-microbial and anti-biofilm potentials of green mono-and multi-metallic nanoparticles: A review

Nanoparticles synthesized through the green route deserve special mention because this green technology is not only energy-efficient and cost-effective but also amenable to the environment. Various biological resources have been used for the generation of these 'green nanoparticles'. Biological wastes have also been focused in this direction thereby promoting the value of waste. Reports indicate that green nanoparticles exhibit remarkable antimicrobial activitiesboth singly as well as in combination with standard antibiotics. The current phenomenon of multi-drug resistance has resulted due to indiscriminate administration of high-doses of antibiotics followed by significant toxicity. In the face of this emergence of drug-resistant microbesthe efficacy of green nanoparticles might prove greatly beneficial. Microbial biofilm is another hurdle in the effective treatment of diseases as the microorganismsbeing embedded in the meshwork of the biofilmevade the antimicrobial agents. Nanoparticles may act as a ray of hope on the face of this challenge tooas they not only destroy the biofilms but also lessen the doses of antibiotics requiredwhen administered in combination with the nanoparticles. It should be further noted that the resistance mechanisms exhibited by the microorganisms seem not that relevant for nanoparticles. The current review, to the best of our knowledgefocuses on the structures of these green nanoparticles along with their biomedical potentials. It is interesting to note how a variety of structures are generated by using resources like microbes or plants or plant products and how the structure affects their activities. This study might pave the way for further development in this arena and future work may be taken up in identifying the detailed mechanism by which 'green' synthesis empowers nanoparticles to kill pathogenic microbes.

Controlled biosynthesis of gold nanoparticles with Coffea arabica using factorial design

Green synthesis of metallic nanoparticles has become incredibly popular, mainly by minimizing problems of environmental contamination and by being able to reduce, stabilize and potentially functionalize nanomaterials. Such compounds have possible applications in various areas, e.g., pharmaceuticals (drug delivery systems, cosmetics), textile industry (clothing with antimicrobial properties), diagnostic medicine (imaging, high efficiency biosensors), energy (solar panels), bioremediation, among others. However, the lack of reproducibility and information on the control mechanisms during synthesis have made the application of green-synthesized nanoparticles unfeasible. Thus, this study proposed the investigation of the main mechanisms affecting synthesis control, using factorial design for the preparation of gold nanoparticles with extract of Coffea arabica. We obtained stable (Zeta Potential, UV-vis and DLS), monodisperse, and quasi-spherical (TEM) nanoparticles, which presented adsorbed aromatic molecules (FTIR and RAMAN) and defined crystal structure (XRD), proving that the plant extract acted as a reducing agent, as well as a stabilizer and functionalizer for the synthesized nanostructures. The factorial design employed here to obtain gold nanoparticles with Coffea arabica extract allowed for a controlled and reproducible synthesis, enabling new possibilities for the application in several fields.

Algae-based metallic nanoparticles: Synthesis, characterization and applications

Nanomaterials (NMs) tailored via conventional physicochemical routes play havoc with the environment that has led to the evolution of competent green routes for the actualization of a circular economy on an industrial-scale. Algae belonging to the class Cyanophyceae, Chlorophyceae, Phaeophyceae and Rhodophyceae have been harnessed as nano-machineries through intracellular and extracellular synthesis of gold (Au), silver (Ag) and several other metallic nanoparticles. Algae are an appealing platform for the production of diverse NMs, primarily due to the presence of bioactive compounds such as pigments and antioxidants in their cell extracts that act as biocompatible reductants. Chlorella spp. and Sargassum spp. have been extensively explored for the synthesis of nanoparticles having antimicrobial properties, which can potentially substitute conventional antibiotics. Characterization of nanoparticles (NPs) synthesised from algae has been done using advanced spectroscopic, diffractographic and microscopic techniques such as UV-Vis FT-IR, DLS, XPS, XRD, SEM, TEM, AFM, HR-TEM, and EDAX. The present paper reviews the information available on algae-mediated biosynthesis of various NPs, their characterization and applications in different domains.

Production, characterization and antibacterial activity of silver nanoparticles produced by Fusarium oxysporum and monitoring of protein-ligand interaction through in-silico approaches

The present study envisages biological production of silver nanoparticles using Fusarium oxysporum and in-silico identification of the antibacterial activity of the nanoparticles using protein-ligand interaction studies. The morphology of the nanoparticles was variable, with majority of them spherical in the size range 1-50 nm. For in-silico studies, two microorganisms, Escherichia coli and Pseudomonas aeruginosa were selected and metal docking was carried out using the licensed software SYBYL X 1.1.1. The ligand docked deeply into the binding pockets of the outer membrane proteins (OMPs) of both E. coli and P. aeruginosa. The results showed that silver may prove to be a strong antibacterial agent against both the pathogens, with the antibacterial action of silver being greater in the case of P. aeruginosa. The results obtained through in-silico studies were further validated by in-vitro approaches on both solid and liquid media to confirm the results obtained by in-silico analysis. The corroboration of in-silico and in-vitro results amply demonstrates the immense antibacterial potential of silver nanoparticles against the selected pathogens.

Use of DNA-generated gold nanoparticles to radiosensitize and eradicate radioresistant glioma stem cells

The surface reactivity of gold nanoparticles (AuNPs) is receiving attention as a radiosensitizer of cancer cells for radiation therapy and/or as a drug carrier to target cells. This study demonstrates the potential of DNA-AuNPs (prepared by mixing calf thymus DNA with HAuCl₄ solution) as a radiosensitizer of human glioma cells that have cancer stem cell (CSC)-like properties, to reduce their survival. CSC-like U251MG-P1 cells and their parental glioblastoma U251MG cells are treated with a prepared DNA-AuNP colloid. The radiosensitivity of the resultant AuNP-associated cells are significantly enhanced. To reveal the mechanism by which survival is reduced, the generation of reactive oxygen species (ROS), apoptosis induction, or DNA damage in the cells is assayed using the fluorescent dye DCFDA, annexin V-FITC/PI, and foci formation of γ-H2AX, respectively. X-ray irradiation with administration of AuNPs overcomes the radioresistance of U251MG-P1 cells. It does not induce ROS generation or apoptosis in the cells but enhances the number of abnormal nuclei with abundant γ-H2AX foci, which is judged as cell death by mitotic catastrophe. The AuNP association with the cells effectively induces mitotic catastrophe in x-ray-irradiated CSC-like cells, implicating that DNA-AuNPs might be a promising tool to develop an efficient radiosensitizer against CSC.

Gold nanoparticles for diagnosis and therapy of oncological diseases

Due to chemical stability, low toxicity, and relative simplicity of synthesis/modification techniques, gold nanoparticles (NP) enjoy a wide range of biomedical applications, including in vitro diagnostics, targeted drug delivery, contrast-enhanced radiation therapy, and photothermal therapy. The high ratio of the gold NP surface area to their volume facilitates design of complex nanoplatforms for various therapeutic and diagnostic purposes. Unique electrical and optical properties of gold NP known as surface plasmon resonance assist medical diagnosis. In this work we look at the basic methods for gold NP synthesis and modification, including the so-called green chemistry, talk about the pharmacological aspects of their application and highlight their potential as diagnostic agents. We believe that due to their unique properties, gold-based nanoplatforms for targeted drug delivery and theranostics have indisputable advantages over other nanoparticles.

L-Glutamine-assisted synthesis of ZnO oatmeal-like/silver composites as an electrochemical sensor for Pb2+ detection

We report a green synthesis of oatmeal ZnO/silver composites in the presence of L-glutamine as an electrochemical sensor for Pb²⁺ detection. The synthesis was performed via the direct reduction of Ag⁺ in the presence of L-glutamine in NaOH. X-ray diffraction indicated that the Ag⁺ was completely reduced to metallic Ag. The field emission scanning electron microscopy (FESEM) and energy dispersive X-ray results confirmed an oatmeal-like morphology of the ZnO with the presence of Ag. The FESEM images showed the effect of L-glutamine on the ZnO morphology. The EIS results confirmed a significant decrease in the charge transfer resistance of the modified glassy carbon electrode due to the presence of Ag. From the differential pulse voltammetry results, a linear working range for the concentration of Pb²⁺ between 5 and 6 nM with LOD of 0.078 nM (S/N = 3) was obtained. The sensitivity of the linear segment is 1.42 μA nM^-1 cm^-2. The presence of L-glutamine as the capping agent and stabilizer decreases the size of Ag nanoparticles and prevents the agglomeration of ZnO, respectively. Graphical abstract ᅟ.

Seed-mediated synthesis of plasmonic gold nanoribbons using cancer cells for hyperthermia applications

A surfactant-less, seed mediated, biological synthesis of two dimensional (2-D) nanoribbons in the presence of breast cancer cells (MCF7) is demonstrated. The diameter and yield of nanoribbons are tunable via seeds and gold precursor concentration. Such crystalline nanoribbons serve to enhance the Raman signals over MCF7 cells. The side and slopes of the triangular nanoplatelets fused as nanoribbons exhibit plasmon excitement in quadrupole resonance modes in the infrared region. Consequently, when irradiated with an infrared laser they show an excellent photothermal effect and rapid rise in temperature. The experimental results verified by finite-difference time-domain (FTDT) calculations reveal the presence of wedge-plasmon polaritons propagating along the edges of the nanoribbons. These simulations confirm that long aspect ratio nanoribbon's edges and vertices act as an active optical waveguide, allowing for heat propagation along the long axis, killing cancer cells in the process at lower power doses.

Identification of nanoparticles and nanosystems in biological matrices with scanning probe microscopy

Identification of nanoparticles and nanosystems into cells and biological matrices is a hot research topic in nanobiotechnologies. Because of their capability to map physical properties (mechanical, electric, magnetic, chemical, or optical), several scanning probe microscopy based techniques have been proposed for the subsurface detection of nanomaterials in biological systems. In particular, atomic force microscopy (AFM) can be used to reveal stiff nanoparticles in cells and other soft biomaterials by probing the sample mechanical properties through the acquisition of local indentation curves or through the combination of ultrasound-based methods, like contact resonance AFM (CR-AFM) or scanning near field ultrasound holography. Magnetic force microscopy can detect magnetic nanoparticles and other magnetic (bio)materials in nonmagnetic biological samples, while electric force microscopy, conductive AFM, and Kelvin probe force microscopy can reveal buried nanomaterials on the basis of the differences between their electric properties and those of the surrounding matrices. Finally, scanning near field optical microscopy and tip-enhanced Raman spectroscopy can visualize buried nanostructures on the basis of their optical and chemical properties. Despite at a still early stage, these methods are promising for detection of nanomaterials in biological systems as they could be truly noninvasive, would not require destructive and time-consuming specific sample preparation, could be performed in vitro, on alive samples and in water or physiological environment, and by continuously imaging the same sample could be used to dynamically monitor the diffusion paths and interaction mechanisms of nanomaterials into cells and biological systems. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Cancer cells biomineralize ionic gold into nanoparticles-microplates via secreting defense proteins with specific gold-binding peptides

Cancer cells have the capacity to synthesize nanoparticles (NPs). The detailed mechanism of this process is not very well documented. We report the mechanism of biomineralization of aqueous gold chloride into NPs and microplates in the breast-cancer cell line MCF7. Spherical gold NPs are synthesized in these cells in the presence of serum in the culture media by the reduction of HAuCl₄. In the absence of serum, the cells exhibit gold microplate formation through seed-mediate growth albeit slower reduction. The structural characteristics of the two types of NPs under different media conditions were confirmed using scanning electron microscopy (SEM); crystallinity and metallic properties were assessed with transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy (XPS). Gold-reducing proteins, related to cell stress initiate the biomineralization of HAuCl₄ in cells (under serum free conditions) as confirmed by infrared (IR) spectroscopy. MCF7 cells undergo irreversible replicative senescence when exposed to a high concentration of ionic gold and conversely remain in a dormant reversible quiescent state when exposed to a low gold concentration. The latter cellular state was achievable in the presence of the rho/ROCK inhibitor Y-27632. Proteomic analysis revealed consistent expression of specific proteins under serum and serum-free conditions. A high-throughput proteomic approach to screen gold-reducing proteins and peptide sequences was utilized and validated by quartz crystal microbalance with dissipation (QCM-D).

STATEMENT OF SIGNIFICANCE

Cancer cells are known to synthesize gold nanoparticles and microstructures, which are promising for bioimaging and other therapeutic applications. However, the detailed mechanism of such biomineralization process is not well understood yet. Herein, we demonstrate that cancer cells exposed to gold ions (grown in serum/serum-free conditions) secrete shock and stress-related proteins with specific gold-binding/reducing polypeptides. Cells undergo reversible senescence and can recover normal physiology when treated with the senescence inhibitor depending on culture condition. The use of mammalian cells as microincubators for synthesis of such particles could have potential influence on their uptake and biocompatibility. This study has important implications for in-situ reduction of ionic gold to anisotropic micro-nanostructures that could be used in-vivo clinical applications and tumor photothermal therapy.

Mammalian cells: a unique scaffold forin situbiosynthesis of metallic nanomaterials and biomedical applications

Nanoscale materials biosynthesis by using mammalian scaffold is green and highly biocompatible.

Properties of in situ generated gold nanoparticles in the cellular context

Gold nanostructures that serve as probes for nanospectroscopic analysis of eukaryotic cell cultures can be obtained by the in situ reduction of tetrachloroauric acid (HAuCl₄). To understand the formation process of such intracellularly grown particles depending on the incubation medium, the reaction was carried out with 3T3 fibroblast cells in three different incubation media, phosphate buffer, Dulbecco's Modified Eagle Medium (DMEM), and standard cell culture medium (DMEM with fetal calf serum). The size, the optical properties, the biomolecular corona, and the localization of the gold nanoparticles formed in situ vary for the different conditions. The combination of surface-enhanced Raman scattering (SERS) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) microscopic mapping and transmission electron microscopy (TEM) provides complementary perspectives on plasmonic nanoparticles and non-plasmonic gold compounds inside the cells. While for the incubation with HAuCl₄ in PBS, gold particles provide optical signals from the nucleus, the incubation in standard cell culture medium leads to scavenging of the toxic molecules and the formation of spots of high gold concentration in the cytoplasm without formation of SERS-active particles inside the cells. The biomolecular corona of nanoparticles formed in situ after incubation in buffer and DMEM differs, suggesting that different intracellular molecular species serve for reduction and stabilization. Comparison with data obtained from ready-made gold nanoparticles suggests complementary application of in situ and ex situ generated nanostructures for optical probing.

Bio-Inspired Green Nanoparticles: Synthesis, Mechanism, and Antibacterial Application

In the recent years, noble nanoparticles have attracted and emerged in the field of biology, medicine and electronics due to their incredible applications. There were several methods have been used for synthesis of nanoparticles such as toxic chemicals and high energy physical procedures. To overcome these, biological method has been used for the synthesis of various metal nanoparticles. Among the nanoparticles, silver nanoparticles (AgNPs) have received much attention in various fields, such as antimicrobial activity, therapeutics, bio-molecular detection, silver nanocoated medical devices and optical receptor. Moreover, the biological approach, in particular the usage of natural organisms has offered a reliable, simple, nontoxic and environmental friendly method. Hence, the current article is focused on the biological synthesis of silver nanoparticles and their application in the biomedical field.

Optical Clearing Delivers Ultrasensitive Hyperspectral Dark-Field Imaging for Single-Cell Evaluation

A single-cell optical clearing methodology is developed and demonstrated in hyperspectral dark-field microscopy (HSDFM) and imaging of plasmonic nanoprobes. Our strategy relies on a combination of delipidation and refractive index (RI) matching with highly biocompatible and affordable agents. Before applying the RI-matching solution, the delipidation step by using a mild solvent effectively eliminates those high-density, lipid-enriched granular structures which emit strong scattering. Upon treatment, the background scattering from cellular organelles could be repressed to a negligible level while the scattering signals from plasmonic nanomaterials increase, leading to a significant improvement of the signal-to-noise ratio (SNR). With this method established, the versatility and applicability of HSDFM are greatly enhanced. In our demonstration, quantitative mapping of the dimerization-activated receptor kinase HER2 is achieved in a single cancer cell by a nonfluorescent approach. High-resolution imaging for oncogenic mRNAs, namely ER, PR, and HER2, is performed with single labeling. More importantly, in situ multiplex detection of mRNA and protein is made possible by HSDFM since it overcomes the difficulties of complex staining and signal imbalance suffered by the conventional optical imaging. Last, we show that with optical clearing, characterization of intracellularly grown gold particulates is accomplished at an unprecedented spatiotemporal resolution. Taken together, the uniqueness of optical clearing and HSDFM is expected to open ample avenues for single-cell studies and biomedical engineering.

Green synthesis of gold nanoparticles (Elixir of Life) from banana fruit waste extract – an efficient multifunctional agent

Revealing the potential of banana fruit waste extract as a reducing, capping and stabilizing agent for the synthesis of the Elixir of Life.

Identification of Metal Oxide Nanoparticles in Histological Samples by Enhanced Darkfield Microscopy and Hyperspectral Mapping

Nanomaterials are increasingly prevalent throughout industry, manufacturing, and biomedical research. The need for tools and techniques that aid in the identification, localization, and characterization of nanoscale materials in biological samples is on the rise. Currently available methods, such as electron microscopy, tend to be resource-intensive, making their use prohibitive for much of the research community. Enhanced darkfield microscopy complemented with a hyperspectral imaging system may provide a solution to this bottleneck by enabling rapid and less expensive characterization of nanoparticles in histological samples. This method allows for high-contrast nanoscale imaging as well as nanomaterial identification. For this technique, histological tissue samples are prepared as they would be for light-based microscopy. First, positive control samples are analyzed to generate the reference spectra that will enable the detection of a material of interest in the sample. Negative controls without the material of interest are also analyzed in order to improve specificity (reduce false positives). Samples can then be imaged and analyzed using methods and software for hyperspectral microscopy or matched against these reference spectra in order to provide maps of the location of materials of interest in a sample. The technique is particularly well-suited for materials with highly unique reflectance spectra, such as noble metals, but is also applicable to other materials, such as semi-metallic oxides. This technique provides information that is difficult to acquire from histological samples without the use of electron microscopy techniques, which may provide higher sensitivity and resolution, but are vastly more resource-intensive and time-consuming than light microscopy.

Internalization: acute apoptosis of breast cancer cells using herceptin-immobilized gold nanoparticles

Herceptin, the monoclonal antibody, was successfully immobilized on gold nanoparticles (GNPs) to improve their precise interactions with breast cancer cells (SK-BR3). The mean size of the GNPs (29 nm), as determined by dynamic light scattering, enlarged to 82 nm after herceptin immobilization. The in vitro cell culture experiment indicated that human skin cells (FB) proliferated well in the presence of herceptin-conjugated GNP (GNP–Her), while most of the breast cancer cells (SK-BR3) had died. To elucidate the mechanism of cell death, the interaction of breast cancer cells with GNP–Her was tracked by confocal laser scanning microscopy. Consequently, GNP–Her was found to be bound precisely to the membrane of the breast cancer cell, which became almost saturated after 6 hours incubation. This shows that the progression signal of SK-BR3 cells is retarded completely by the precise binding of antibody to the human epidermal growth factor receptor 2 receptor of the breast cancer cell membrane, causing cell death.