Biogenic synthesis of reduced graphene oxide decorated with silver nanoparticles (rGO/Ag NPs) using table olive (olea europaea) for efficient and rapid catalytic reduction of organic pollutants

Enhanced removal of Pb(II) from acid mine drainage using green reduced graphene oxide/silver nanoparticles

Mining activities can potentially release high levels of Pb(II) in acid mine drainage (AMD), which thereafter poses a significant threat to ecological security. In this study, green reduced graphene oxide/silver nanoparticles (rGO/Ag NPs) were successfully synthesized via a one-step approach using a green tea extract and subsequently used as a cost-effective absorbent to remove Pb(II) from AMD. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy indicated that organic functional groups in the green tea extracts, such as C=O-C, CO, and CC, acted both as reductants and stabilizers in the synthesis of rGO/Ag NPs. In addition, the removal efficiency of Pb(II) by rGO/Ag NPs (84.2 %) was much better than either rGO (75.4 %) or Ag NPs (12.3 %) alone. Also, in real AMD, the distribution coefficient (Kd) of Pb(II) (4528 mL/g), was much higher than other heavy metal indicating the adsorbent had a high selective affinity for Pb(II). Interestingly, after five cycles of use, the removal efficiency of Pb(II) by rGO/Ag NPs from AMD actually increased from 46.4 to 65.2 % due to iron oxides (i.e., Fe2O3 and Fe3O4) being generated when rGO/Ag NPs was exposed to AMD. The removal of Pb(II) via adsorption on the rGO/Ag NPs surface involved formation of hexagonal rod-like precipitates. This work demonstrated the potential of rGO/Ag NPs to be continuously used for the removal of Pb(II) from AMD.

Application of Ag nanoparticles decorated on graphene nanosheets for electrochemical sensing of CEA as an important cancer biomarker

In this research, a novel biosensing platform is described based on graphene nano-sheets decorated with Ag nano-particles (GNSs@Ag NPs). The designed electrochemical aptasensor was employed to determine carcinoembryonic antigen (CEA), an important cancer biomarker. Inherently, aptasensing interfaces provide high sensitivity for CEA tumor marker because of the high specific surface area and excellent conductivity of the prepared GNSs@Ag NPs composite. The established assay demonstrated a wide linear range from 0.001 pg/mL to 10 pg/mL with a correlation coefficient of 0.9958 and low detection limit (DL) of 0.5 fg/mL based on S/N = 3 protocol. The derived biosensor illustrated acceptable selectivity towards common interfering species including HER2, VEGF, IgG, MUC1 and CFP10. In addition, the aptsensor showed good reproducibility and fast response time. The applicability of the suggested strategy in human serum samples was also examined and compared to the commercial enzyme-linked immunosorbent assay (ELISA). Based on the experimental data, it was found that the discussed sensing platform can be exerted in the monitoring of CEA in different cancers for early diagnosis.

Novel biosynthesis of gold nanoparticles for multifunctional applications: Electrochemical detection of hydrazine and treatment of gastric cancer

In this work, an environmentally friendly strategy was used to synthesize gold nanoparticles (Au NPs) using Olea europaea (olive) fruit. Transmission electron microscopy (TEM), UV-Vis spectroscopy, X-ray diffraction (XRD) and energy-dispersive X-ray (EDX) were used to characterize the physicochemical properties of the synthesized NPs. An Au NPs modified glassy carbon electrode was used to investigate the direct electrochemical oxidation of hydrazine. The suggested hydrazine sensor has good performance, such as a wide linear range (2.5-275 μM), low limit of detection (0.09 μM), notable selectivity and excellent reproducibility (RSD = 2.2%). The in-vitro cytotoxicity of three human cancer cell lines (KATOIII, NCI-N87, and SNU-16) was also explored with various concentrations of Au NPs prepared from olive fruit extract. Bio-synthesized Au NPs were found to have cytotoxic properties against gastric cancer in humans based on MTT assay protocol. The obtained results show that green synthesized Au NPs can be successfully employed in electrochemical sensing and cancer treatment applications.

Cancer treatment and toxicity outlook of nanoparticles

Diversified nanosystems with tunable physicochemical attributes have emerged as potential solution to globally devastating cancer by offering novel possibilities for improving the techniques of cancer detection, imaging, therapies, diagnosis, drug delivery and treatment. Drug delivery systems based on nanoparticles (NPs) with ability of crossing different biological barriers are becoming increasingly popular. Besides, NPs are utilized in pharmaceutical sciences to mitigate the toxicity of conventional cancer therapeutics. However, significant NPs-associated toxicity, off-targeted activities, and low biocompatibility limit their utilization for cancer theranostics and can be hazardous to cancer patients up to life-threatening conditions. NPs interact with the biomolecules and disturb their regular function by aggregating inside cells and forming a protein corona, and the formulation turns ineffective in controlling cancer cell growth. The adverse interactions between NPs and biological entities can lead to life-threatening toxicities. This review focuses on the widespread use of various NPs including zinc oxide, titanium oxide, silver, and gold, which serve as efficient nano-vehicles and demonstrate notable pharmacokinetic and pharmacodynamic advantages in cancer therapy. Subsequently, the mechanism of nanotoxicity attached with these NPs, alternate solutions and their prospect to revolutionize cancer theranostics are highlighted. This review will serve as guide for future developments associated with high-performance NPs with controlled toxicity for establishing them as modern-age nanotools to manage cancer in tailored manner.

Biogenic preparation of copper oxide nanoparticles using table olive: Catalytic reduction, cytotoxicity, and burn wound healing activities

Green strategy for the preparation of copper oxide nanoparticles (CuO NPs) using table olive has been researched in the present work. Some characterization assays viz., transmission electron microscopy (TEM), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) was used for evaluation of the crystal structure, size and morphology of the manufactured NPs. As a catalyst, the prepared material demonstrated remarkable catalytic capability (>99% in 4 min) for the reduction of rhodamine B using sodium borohydride. In addition, the treated cells with the CuO NPs were examined by regarding the cytotoxicity properties on normal (HUVEC) cell line. The results showed that the prepared CuO NPs did not have any cytotoxicity effects on HUVEC (up to 500 μg/mL). Furthermore, in vivo experiments on burn wounds in rats show that the synthesized CuO NPs ointment significantly diminished (p ≤ 0.01) the wound area. On the other hand, the wound contracture factor was increased in comparison with the control groups. Collectively, the CuO NPs prepared by biological method have potential applications in organic pollutants reduction and wound care applications. In this viewpoint, CuO NPs may be considered as an effective for treatment of different wounds including burn wounds or injuries from surgeries such as plastic surgery.

Dynamics of reduced graphene oxide: synthesis and structural models

Technological advancements are leading to an upsurge in demand for functional materials that satisfy several of humankind's needs. In addition to this, the current global drive is to develop materials with high efficacy in intended applications whilst practising green chemistry principles to ensure sustainability. Carbon-based materials, such as reduced graphene oxide (RGO), in particular, can possibly meet this criterion because they can be derived from waste biomass (a renewable material), possibly synthesised at low temperatures without the use of hazardous chemicals, and are biodegradable (owing to their organic nature), among other characteristics. Additionally, RGO as a carbon-based material is gaining momentum in several applications due to its lightweight, nontoxicity, excellent flexibility, tuneable band gap (from reduction), higher electrical conductivity (relative to graphene oxide, GO), low cost (owing to the natural abundance of carbon), and potentially facile and scalable synthesis protocols. Despite these attributes, the possible structures of RGO are still numerous with notable critical variations and the synthesis procedures have been dynamic. Herein, we summarize the highlights from the historical breakthroughs in understanding the structure of RGO (from the perspective of GO) and the recent state-of-the-art synthesis protocols, covering the period from 2020 to 2023. These are key aspects in the realisation of the full potential of RGO materials through the tailoring of physicochemical properties and reproducibility. The reviewed work highlights the merits and prospects of the physicochemical properties of RGO toward achieving sustainable, environmentally friendly, low-cost, and high-performing materials at a large scale for use in functional devices/processes to pave the way for commercialisation. This can drive the sustainability and commercial viability aspects of RGO as a material.

Green Biogenic of Silver Nanoparticles Using Polyphenolic Extract of Olive Leaf Wastes with Focus on Their Anticancer and Antimicrobial Activities

Agro-industrial wastes are rich in polyphenols and other bioactive compounds, and valorizing these wastes is a crucial worldwide concern for saving health and the environment. In this work, olive leaf waste was valorized by silver nitrate to produce silver nanoparticles (OLAgNPs), which exhibited various biological, antioxidant, anticancer activities against three cancer cell lines, and antimicrobial activity against multi-drug resistant (MDR) bacteria and fungi. The obtained OLAgNPs were spherical, with an average size of 28 nm, negatively charged at -21 mV, and surrounded by various active groups more than the parent extract based on FTIR spectra. The total phenolic and total flavonoid contents significantly increased in OLAgNPs by 42 and 50% over the olive leaf waste extract (OLWE); consequently, the antioxidant activity of OLAgNPs increased by 12% over OLWE, recording an SC₅₀ of OLAgNPs of 5 µg/mL compared to 30 µg/mL in the extract. The phenolic compound profile detected by HPLC showed that gallic acid, chlorogenic acid, rutin, naringenin, catechin, and propyl gallate were the main compounds in the HPLC profile of OLAgNPs and OLWE; the content of these compounds was higher in OLAgNPs than OLWE by 16-fold. The higher phenolic compounds in OLAgNPs are attributable to the significant increase in biological activities of OLAgNPs than that of OLWE. OLAgNPs successfully inhibited the proliferation of three cancer cell lines, MCF-7, HeLa, and HT-29, by 79-82% compared to 55-67% in OLWE and 75-79% in doxorubicin (DOX). The preliminary worldwide problem is multi-drug resistant microorganisms (MDR) because of the random use of antibiotics. Therefore, in this study, we may find the solution in OLAgNPs with concentrations of 2.5-20 µg/mL, which significantly inhibited the growth of six MDR bacteria L. monocytogenes, B. cereus, S. aureus, Y. enterocolitica, C. jejuni, and E. coli with inhibition zone diameters of 25-37 mm and six pathogenic fungi in the range of 26-35 mm compared to antibiotics. OLAgNPs in this study may be applied safely in new medicine to mitigate free radicals, cancer, and MDR pathogens.

Novel biomimetic Prussian blue nanocubes-based biosensor for Tau-441 protein detection

Tau protein is a promising biomarker for early diagnosis of Alzheimer's disease. Therefore, there is an urgent need to develop a simple and effective method for its detection. To this end, an innovative sensing device was developed using a carbon screen-printed electrode (C-SPE) decorated with graphene oxide/Prussian Blue nanocubes (GO/PBNCs) for the selective and sensitive determination of Tau-441 protein. The molecular imprinting polymer (MIP) was built on the GO/PBNCs/C-SPE by electropolymerizing 3-aminophenol (3-AMP) in the presence of the target protein using chronoamperometry, and the template was subsequently removed from the polymer matrix with oxalic acid. In parallel, a non-imprinted material (NIP) was also prepared in the absence of the target for comparison purposes. Scanning electron microscopy and transmission electron microscopy, were used to study the morphology of the modified electrode and electrochemical techniques were used to monitor the stepwise assembly of the sensor. Under optimized conditions, the sensing platform exhibited a linear range within 1.09 and 2.18 nmol/L and a detection limit of 0.01 pmol/L in spiked phosphate buffer solution (PBS). The MIP sensor showed minimal interference with uric acid and bovine albumin. The simplicity of production, affordable cost and promising performance make this sensor a potential strategic sensing platform for the detection of chemical and biological molecules.

One-step electrochemical elaboration of SnO2 modified electrode for lead ion trace detection in drinking water using SWASV

A facile method was proposed for the elaboration of an electrochemical sensor for heavy metal's trace detection by using square wave anodic stripping voltammetry (SWASV); this method is based on a simple anodic conversion of tin electrode into Sn/SnO₂ modified electrode. Both electrochemical and physico-chemical techniques were used to confirm the modification process and better understand the electrode's behavior. Then, depending on the operating conditions, the response signal was studied and adjusted in order to obtain optimal sensor performance. When optimized, the proposed method reached a lowest detection limit (LOD) of 2.15 μg L^-1 (0.0104 μM), and quantification limit (LOQ) of 5.36 μg L^-1 (0.0259 μM), in linearity range between from 6.2 and 20.7 μg L^-1. Additionally, after having used the elaborated electrode for ten successive measurements, the repeatability remains very high with an RSD of approximately 5.3%; furthermore, ten other species appear to have very slight effect on Pb(II) detection. Finally, for the method validation, the proposed electrode was able to sense different lead concentration integrated in a local bottled spring water by showing recovery levels ranging from 103.8 to 108.4%.

A signal-on electrochemical DNA biosensor based on exonuclease III-assisted recycling amplification

DNA electrochemical detection technology has attracted tremendous interest in recent years. However, a facile and sensitive method for the detection of the disease indicators or genes is still waiting. Herein, we constructed a signal-on electrochemical platform for detecting the manganese superoxide dismutase (MnSOD) gene by incorporating a redox electrochemical signal probe (methylene blue) and exonuclease III-assisted target recycling signal amplification strategy. The sensor was prepared by self-assembly of a capture DNA probe of thiol-modified on GCE with gold electrodeposition. In the presence of target DNA, the exonuclease III can cleave the duplexes formed by the target DNA and the redox-labeled hairpin probes, release the target DNA and produce a residual sequence. The target DNA can continue to hybridize with the hairpin probe for the next cycle of amplification. The residual sequence hybridized with the surface-immobilized capture probes on AuNPs-modified GCE to generate a significantly amplified redox current. In particular, the redox current value of the resultant sensor showed a linear relationship with MnSOD gene concentration in the range of 1-10⁴ pM with the detection limit as low as 0.3 pM. Furthermore, the sensor has excellent specificity and can distinguish single-base mismatch from perfectly matched target DNA. The sensor is fast in operation, and simple in design for detecting different DNA sequences or DNA identification by selecting the appropriate probe sequence, thus shedding light on a good promising application when encountering disease outbreaks or for the early clinical diagnosis of gene-related diseases.