Surfactant stabilized gold nanomaterials for environmental sensing applications - A review

Identification and Functional Characterization of a Surfactant-like Protein Region in Flagellin FliC for Stabilizing Selenium Nanoparticles and Enhancing Bioavailability

Biogenic selenium nanoparticles (SeNPs) are the most favorable Se form for nutritional supplementation due to their high stability, low toxicity, and high activity. However, the interaction between the surface-binding proteins and their stable biogenic SeNPs, as well as their impact on the stability and bioavailability of SeNPs, remains to be understood. In vitro stabilization experiments revealed an amino acid segment (F(235-386)) in Rahnella aquatilis' flagellin FliC, with surfactant-like properties, stabilizing SeNPs under harsh conditions. FliC and F(235-386) were employed as stabilizers to synthesize SeNPs (FliC@SeNPs and F(235-386)@SeNPs), and surface chemistry analysis revealed coordination reactions between the proteins and Se atoms on the surface of SeNPs. Both FliC and F(235-386) enhanced SeNPs uptake in wheat seedlings but reduced it in bacteria and yeast. This study highlights FliC's core function in stabilizing SeNPs and enhancing their bioavailability, paving the way for agricultural and nutritional applications.

Natural Polymer Encapsulated Zeolitic Imidazolate Framework-12 Composite toward Electrochemical Sensing of Antitumor Agent

Encapsulation of natural polymer pectin (Pec) into a zeolitic imidazolate framework-12 (ZIF-12) matrix via a simple chemical method toward anticancer agent gallic acid (GA) detection is reported in this work. GA, a natural phenol found in many food sources, has gained attention by its biological effects on the human body, such as an antioxidant and anti-inflammatory. Therefore, it is crucial to accurately and rapidly determine the GA level in humans. The encapsulation of Pec inside the ZIF-12 has been successfully confirmed from the physiochemical studies such as XRD, Raman, FTIR, and XPS spectroscopy along with morphological FESEM, BET, and HRTEM characterization. Under optimized conditions, the Pec@ZIF-12 composite exhibits wide linear range of 20 nM-250 μM with a detection limit of 2.2 nM; also, it showed excellent selectivity, stability, and reproducibility. Furthermore, the real sample analysis of food samples including tea, coffee, grape, and pomegranate samples shows exceptional recovery percentage in an unspiked manner. So far, there is little literature for encapsulating proteins, enzymes, metals, etc., that have been reported; here, we successfully encapsulated a natural polymer Pec inside the ZIF-12 cage. This encapsulation significantly enhanced the composite electrochemical performance, which could be seen from the overall results. All of these strongly suggest that the proposed Pec@ZIF-12 composite could be used for miniaturized device fabrication for the evaluation of GA in both home and industrial applications.

Polyacrylonitrile as a versatile matrix for gold nanoparticle-based SERS substrates

As an effective and ultrasensitive molecule detection technique, surface-enhanced Raman spectroscopy (SERS) needs efficient and highly responsive substrates to further enhance its sensitivity and utility. In this work, the preparation and characterisation of polyacrylonitrile/gold nanoparticle (PAN/AuNPs) composite porous films have been described for SERS-based detection of methylene blue (MB) dye. The PAN/AuNPs composite films were prepared with a simple dip coating technique, yielding a highly porous structure with uniformly dispersed Au nanoparticles (AuNPs). Scanning electron microscopy (SEM) revealed a linked pore network within the films. In X-ray diffraction (XRD), the characteristic crystal peak of AuNP clusters was observed, proving the presence of AuNPs in the composite. UV-vis absorption spectra also indicated the existence of the AuNPs. The methylene blue (MB) dye has been detected using PAN/AuNPs composite SERS substrates. These substrates showed excellent sensitivity by detecting 50 nM dye concentration and enhancing the Raman peak intensity at 1622 cm-1. The SERS enhancement factor (EF) for MB detection was determined to be around 106, demonstrating the remarkable sensitivity of the PAN/AuNPs composite porous films. The findings demonstrate the enormous potential of PAN/AuNPs composite porous films as reliable SERS substrates, displaying their efficacy in detecting trace levels of analytes in chemical and biological sensing applications.

Gold nanoparticles (AuNPs) decrease the viability of cervical cancer cells by inducing the BAX gene and activating antioxidant enzymes

BACKGROUND

Cervical Cancer (CC), a leading cause of female mortality worldwide, demonstrates a direct association with high-risk human papillomavirus (HPV) infections. However, not all CC patients exhibit HPV infection, suggesting additional predisposing factors. Recently, disturbances in the oxidant-antioxidant balance have been implicated in CC development. This study explores the impact of gold nanoparticles (AuNPs) on the survival and antioxidant capacity of HeLa cells, aiming to contribute to novel CC therapy approaches.

METHODS AND RESULTS

Synthesized and characterized AuNPs (25.5 nm, uniform distribution according to the DLS analysis) were administered to HeLa cells at varying concentrations. After 24 h, cell viability was assessed using the (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2 H-tetrazolium bromide) (MTT) assay. Real-time PCR measured expression levels of apoptosis-related genes (BCL2 associated X (BAX) and p53). Catalase and superoxide dismutase (SOD) activities, key antioxidant enzymes, were also evaluated post-AuNP treatment. AuNPs dose-dependently reduced HeLa cell viability, with an IC50 value of 113 µg/ml. BAX gene expression significantly increased, indicating pro-apoptotic effects. Moreover, enzyme activities significantly rose under AuNP influence.

CONCLUSIONS

AuNPs demonstrated the potential to induce HeLa cell death by upregulating pro-apoptotic BAX gene expression and altering antioxidant system enzyme activities. These findings underscore the promise of AuNPs as a therapeutic avenue for CC, emphasizing their impact on crucial cellular processes involved in cancer progression.

Dioctyl sodium sulfosuccinate surfactant self-assembly dependency of solvent hydrophilicity: a modelling study

The self-assembly of dioctyl sodium sulfosuccinate (AOT) model surfactant in solvent environments of differing polarity is examined by means of dissipative particle dynamics (DPD) bead model parametrized against Hildebrand solubility parameters from atomistic molecular dynamics (MD) simulations. The model predicts that in hydrophobic solvents (e.g. dodecane) the surfactant forms small (Nagg ∼ 8) reverse micellar aggregates, while in a solvent corresponding to water lamellar assembly takes place, in good agreement with literature structural parameters. Interestingly, solvents of intermediate polarity lead to formation of large, internally structured aggregates. In these, the surfactant headgroups cluster within the aggregate, surrounded by a continuous phase formed by the hydrocarbon tails. We show that the partitioning of the headgroups between the aggregate surface layer and the inner clustered phase depends primarily on solvent polarity, and can be controlled by the solvent, but also system composition. Finally, we compare the DPD assembly response to simplified effective interaction potentials derived at dilute concentration limit for the interactions. The comparison reveals that the simplified effective potential descriptions provide good level of insight on the assembly morphologies, despite drastic, isotropic interactions simplification involved.

A biogenesis construction of CuO@MWCNT via Chenopodium album extract: an effective electrocatalyst for synaptic plasticity neurodegenerative drug pollutant detection

Clioquinol (CLQ) is one of the most toxic halogenated neurodegenerative drugs, and its synaptic plasticity effect directly affects human health and the environment. Cupric oxide (CuO) is an ideal electrocatalyst owing to its earth-abundance, non-toxic nature, and cost-effectiveness. Since phenolate oxygen and pyridine nitrogen in CLQ act as an electron donor and pave the way for detection with Cu2+ ions in the CuO. Designing the architecture of CuO with a multi-walled carbon nanotube (MWCNT) is a sensible strategy to improve the electrochemical activity of the developed sensor. Inspired by the bio-synthesis and green processing, we have demonstrated the in-situ synthesis of CuO nanosphere-decorated MWCNT by Chenopodium album leaf extract through a sonochemical approach and explored its electrochemical sensing performance toward CLQ. The physical comprehensive characterization of prepared nanocomposite was investigated by various microscopic and spectroscopic techniques. For comparison studies, the CuO nanosphere was prepared by the same preparation process without MWCNT. Based on the physical characterization outcomes, the morphological nature of CuO was observed to be a sphere-like structure, which was decorated on the MWCNT with an average crystallite size of 16 nm (± 1 nm). Based on the electrochemical studies, the fabricated nanocomposite exhibits a wider linear range of 0.025-1375 μM, with a minimum detection limit of 4.59 nM L-1 toward CLQ. The viability examination on the biological matrix obtained considerable spike recoveries.

Design of competition nanoreactor with shell-isolated colloidal plasmonic nanomaterials for quantitative sensor platform

Shell-isolated colloid plasmonic nanomaterials-based nanoreactor is a well-established platform widely applied in catalyst or Surface Enhanced Raman Scattering (SERS) sensors. The potentials versatility of nanoreactor platform is mainly implemented by the well-defined and tailorable structure of colloid plasmonic nanomaterials. Currently, a competitive conjugative-mediated nanoreactor is introduced to determine glucose with SERS. Glucose-conjugating nanoreactor, as convertors of the sensors, are constructed by coordinated deposition colloidal gold nanoparticles with sodium nitroprusside framework (Au@SNF) and covalently bonded 4-mercaptopyridine (4-Mpy) with self-assembly strategy. The nanoreactor contained the signal-amplifier Au@SNF NPs, conjugative-mediated signal receiver 4-Mpy, and signal internal standard molecular CN^-. In addition to well-defined morphology and functionality, conjugative-mediated and internal standards method are also employed to benefit the nanoreactor. The two-parameter strategy significantly improves the signal indication and correction. Using this proposed platform, the competitive-mediated nanoreactor provides a quantitative SERS detection of glucose, and extends the applicability of SERS in more complicated and reproducibility analysis. Meanwhile, the nanoreactor based sensors also exhibited better properties to detect glucose in various food samples and bio-samples which provided strongly appliance for glucose sensors.

Gold nanoparticle shape dependence of colloidal stability domains

Controlling the spatial arrangement of plasmonic nanoparticles is of particular interest to utilize inter-particle plasmonic coupling, which allows changing their optical properties. For bottom-up approaches, colloidal nanoparticles are interesting building blocks to generate more complex structures via controlled self-assembly using the destabilization of colloidal particles. For plasmonic noble metal nanoparticles, cationic surfactants, such as CTAB, are widely used in synthesis, both as shaping and stabilizing agents. In such a context, understanding and predicting the colloidal stability of a system solely composed of AuNPs and CTAB is fundamentally crucial. Here, we tried to rationalize the particle behavior by reporting the stability diagrams of colloidal gold nanostructures taking into account parameters such as the size, shape, and CTAB/AuNP concentration. We found that the overall stability was dependent on the shape of the nanoparticles, with the presence of sharp tips being the source of instability. For all morphologies evaluated here, a metastable area was systematically observed, in which the system aggregated in a controlled way while maintaining the colloidal stability. Combining different strategies with the help of transmission electron microscopy, the behavior of the system in the different zones of the diagrams was addressed. Finally, by controlling the experimental conditions with the previously obtained diagrams, we were able to obtain linear structures with a rather good control over the number of particles participating in the assembly while maintaining good colloidal stability.

Construction of functionalized carbon nanotube@metal oxide nanocomposite for high-performance electrochemical measurement of antipyretic drug in water samples

Acetaminophen (AP) acts as supportive clinical therapy for fever and dysmenorrhea. An overdose of AP may result in severe adverse diseases, such as liver dysfunction. In addition, AP is a key-listed environmental pollutant, which is difficult to degrade in the environment and has serious effects on living bodies. Therefore, the simple and quantitative determination of AP is highly relevant today. In this work, tin dioxide (SnO2) nanoparticles with functionalized multi-walled carbon nanotube (f-MWCNT) as a hybrid composite were prepared by hydrothermal-assisted synthesis. The composite material was characterized by various spectral, morphological, and electrochemical tests. Electrochemical investigations were conducted using a SnO2@f-MWCNT-reinforced electrode for the detection of AP. The composite electrode exhibited better functional properties, which facilitated electron transfer and enhanced electrical conductivity. The calculated low detection limit (LOD) of 0.36 nM is with a wide linear range of concentration from 0.001 to 673 µM. Additionally, the SnO2@f-MWCNT-modified electrode exhibited good anti-interference capability, repeatability, reproducibility, storage, and operational stability. The developed SnO2@f-MWCNT-modified electrode was applied to practical analysis in diverse water matrices (river, drinking, and pond) with acceptable recovery percentages. A synthesized nanoscale metal oxide electrocatalyst is of great interest and an active research area that serves as a foundation for the development of new, cost-effective electrochemical antibiotic drug sensors.

Optical diagnostic imaging and therapy for thyroid cancer

Thyroid cancer, as one of the most common endocrine cancers, has seen a surge in incidence in recent years. This is most likely due to the lack of specificity and accuracy of its traditional diagnostic modalities, leading to the overdiagnosis of thyroid nodules. Although there are several treatment options available, they are limited to surgery and ¹³¹I radiation therapy that come with significant side effects and hence cannot meet the treatment needs of anaplastic thyroid carcinoma with very high malignancy. Optical imaging that utilizes optical absorption, refraction and scattering properties, not only observes the structure and function of cells, tissues, organs, or even the whole organism to assist in diagnosis, but can also be used to perform optical therapy to achieve targeted non-invasive and precise treatment of thyroid cancer. These applications of screening, diagnosis, and treatment, lend to optical imaging's promising potential within the realm of thyroid cancer surgical navigation. Over the past decade, research on optical imaging in the diagnosis and treatment of thyroid cancer has been growing year by year, but no comprehensive review on this topic has been published. Here, we review key advances in the application of optical imaging in the diagnosis and treatment of thyroid cancer and discuss the challenges and potential for clinical translation of this technology.

Determination of heavy metals in water using an FTO electrode modified with CeO2/rGO nanoribbons prepared by an electrochemical method

The rGO/CeO₂/FTO nanocomposite modified electrode was prepared by an electrochemical method. A simple and highly sensitive electrochemical sensing platform for electrochemical rGO and modified CeO₂ nanoribbons directly on FTO electrodes was developed. Simultaneous determination of Pb²⁺ and Cd²⁺ used the differential pulse anodic stripping voltammetry (DPASV) method. The method was simple to operate, and CeO₂ nanobelts could be obtained simultaneously by electrodeposition and reduction of GO without further processing. This is an environmentally friendly electrochemical method to obtain modified electrodes under mild conditions. The experimental results showed that the linear calibration curves of Pb²⁺ and Cd²⁺ are 1–300 and 0.2–500 μg L⁻¹, respectively. At the same time, no interference from other coexisting metal ions was found during the detection process, which proved that the modified electrode had good stability and repeatability.

The rGO/CeO₂/FTO nanocomposite modified electrode was prepared by an electrochemical method.

Facile synthesis of nanomaterials as nanofertilizers: a novel way for sustainable crop production

Nutrient fertilization plays a major role in improving crop productivity and maintaining soil fertility. In the last few decades, the productivity of current agricultural practices highly depends on the use of chemical fertilizers. Major drawback of traditional fertilizers is their low crop nutrient use efficiency and high loss into water. Nanomaterial in agriculture is a multipurpose tool for increasing growth, development, and yield of plants. Nanotechnology facilitates the amplifying of agriculture production by reducing relevant losses and improving the input efficiency. Nanotechnology has emerged as an attractive field of research and has various agriculture applications, especially the use of nano-agrochemicals to increase nutrient use efficiency and agricultural yield. Nanofertilizers are more effective as compared to chemical fertilizers due to their cost-efficient, eco-friendly, non-toxic, and more stable in nature. Overall, this chapter focuses on synthesis of nanofertilizers through physical, chemical, and biological methods. This chapter will also explore the use of nano-enabled fertilizers to enhance the nutrient use efficiency for sustainable crop production, and global food safety.