Appl. Nano, Volume 5, Issue 4 (December 2024) – 6 articles

Interest in the use of nanoparticles in agriculture has grown in recent years due to their potential abilities across a range of applications that could increase agricultural production, improve the efficiency of nutrient delivery, or improve pest management. However, as with any application of nanomaterials, concern exists about potential risks to human health. Because many applications might result in the attachment of nanoparticles to produce surfaces, it is important to understand the conditions under which rinsing is likely to remove nanoparticles from surfaces and the degree to which they can be removed. This work explored the rinsing removal of two types of nanoparticles, titanium dioxide (TiO₂) and zinc oxide (ZnO), from spinach leaf surfaces in the absence and presence of biofilms based on extracellular polymeric substances (EPS). A hypothesis driving the work was that the presence of biofilms might enhance the retention of nanoparticles. The work combined experiments to determine surface energy parameters for fresh and rotten spinach, for use in extended DLVO (xDLVO) calculations, as well as direct rinsing experiments to explore nanoparticle removal from spinach surfaces. Nanoparticles were quantified using backscattered scanning electron microscopy using techniques developed for the work. Results of xDLVO calculations suggest that the presence of biofilms may actually be likely to reduce the retention of nanoparticles by produce surfaces, although this effect was not apparent in rinsing experiments, which exhibited similar removal of high-concentration TiO₂ from spinach leaves. Overall, nanoparticles deposited from high-concentration suspensions were found to be removed to a greater degree by rinsing, while those deposited from low-concentration suspensions exhibited no apparent release, even under conditions where release might be favored. Full article

While microparticles can be removed by a filtration step at a drinking water treatment plant (DWTP), engineered nanoparticles (ENPs), which are widely used in industry, commerce and households, pose a major problem due to their special properties, e.g., size, reactivity and polarity. In addition, many ENPs exhibit toxic potential, which makes their presence in drinking water undesirable. Therefore, this study investigated the removal of ENPs in the laboratory and at a pilot-scale DWTP. Eight ENPs were synthesized and tested for stability in different types of water. Only three of them were stable in natural water: cetyltrimethylammonium bromide-coated gold (CTAB/AuNPs), polyvinylpyrrolidone-stabilized gold and silver nanoparticles (PVP/AuNPs, PVP/AgNPs). Their retention on quartz sand, silica gel and fresh anthracite was low, but CTAB/AuNPs could be retained on fresh river sand and thus should not overcome riverbank filtration, while PVP/AuNPs and PVP/AgNPs showed no retention and may be present in raw water. During ozonation, PVP/AuNPs remained stable while PVP/AgNPs were partially degraded. The advanced oxidation process (AOP) was less effective than ozone. PVP/AgNPs were almost completely retained on the pilot plant anthracite sand filter coated with manganese(IV) oxide and ferrihydrite from raw water treatment. PVP/AuNPs passed the filter with no retention. In contrast to PVP/AuNPs, PVP/AgNPs and CTAB/AuNPs were also retained on activated carbon. The integration of a flocculation step with iron(III) salts can improve ENP removal, with PVP/AuNPs requiring higher flocculant doses than PVP/AgNPs. PVP/AuNPs, in particular, are well-suited for testing the effectiveness of water treatment. Further data on the occurrence of stable ENPs in raw water and their behavior during water treatment are needed to perform a risk assessment and derive the measures. Full article

Flexible nanocomposite sensors hold significant promise in various applications, such as wearable electronics and medical devices. This research aims to tailor the flexibility and sensitivity of 3D-printed piezoresistive nanocomposite pressure sensors through geometric design, by exploring various simple cellular structures. The geometric designs were specifically selected to be 3D printable with a flexible material, allowing evaluation of the impact of different structures on sensor performance. In this study, we used both experimental and finite element (FE) methods to investigate the effect of geometric design on piezoresistive sensors. We fabricated the sensors using a flexible resin mixed with conductive nanoparticles via a Stereolithography (SLA) additive manufacturing technique. Electromechanical testing was carried out to evaluate the performance of four different sensor designs. Finite element (FE) models were developed, and their results were compared with experimental data to validate the simulations. The results demonstrated that auxetic structure exhibited the highest sensitivity and lowest stiffness both in experimental and FE analysis, highlighting its potential for applications requiring highly responsive materials. The validated FE model was further used for a parametric study of one of the promising simple designs, revealing that variations in geometric parameters significantly impact piezoresistive sensitivity. These findings provide valuable insights for advancing the development of pressure sensors with tailored sensitivity characteristics. Full article

Eco-friendly iron and manganese oxide nanoparticles (Fe₂O₃ and Mn₂O₃) were synthesized and integrated into graphene sheets to form uniform composites. These composites were then embedded in polyvinyl alcohol (PVA) fibers using electrospinning. Comprehensive characterization of the composites and the final composite fibers was conducted using XRD, FE-SEM, and FTIR to analyze their structural complexity and morphological differences. The antibacterial efficacy of the resulting PVA nanofibers was evaluated against Escherichia coli, which is a common pathogen in hospital environments. The results show a significant bactericidal effect against these bacteria, which highlights their potential in medical applications, such as functional bandages and wound dressings. This study paves the way for potential commercial applications of these nanofibers in healthcare settings. Full article

Silver nanoparticles (AgNPs) demonstrate potential in treating aggressive cancers such as triple-negative breast cancer (TNBC) in preclinical models. To further the development of AgNP-based therapeutics for clinical use, it is essential to clearly define the specific physicochemical characteristics of the nanoparticles and connect these properties to biological outcomes. This study addresses this knowledge gap through detailed investigations into the structural and surface functional relationships, exploring the mechanisms, safety, and efficacy of AgNPs in targeting TNBC. The surface functionality of nanoparticles is crucial not only for their internalization into cancer cells but also for enhancing their toxicity toward tumor cells. Although the nanoparticles internalized into cancer cells, they failed to exhibit their full toxicity against the cancer. Herein we report a solvent-assisted synthesis amine, mercaptohexanol and bifunctional silver nanoparticles and performing comparative study to understand their selectivity and toxicity toward TNBC cells. The nanoparticles are fully characterized by UV–visible absorption spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and dynamic light scattering measurement (DLS). The synthesis method achieves an extremely high yield and surface coating ratio of synthesized colloidal AgNPs. Our findings reveal that the amine-capped AgNPs exhibit significant selective toxicity against TNBC cell lines MCF7 and MDA-MB-231 at a concentration of 40 µg/mL without affecting normal breast cell lines MCF10A. This study underscores the potential of functionalized AgNPs in developing safe and targeted therapeutic approaches for treating aggressive cancers like TNBC, laying the groundwork for future clinical advancements. Full article

Wound healing is rarely seen as a problem in healthy individuals; however, under certain pathophysiological conditions, this process can be impaired, leading to the emergence of chronic wounds, which are themselves a serious public health problem. This work aimed to review the most important recent literature on the use of nanoparticles of Ag, Au, and Zn produced from plant extracts and their application as healing agents. To that end, we provide an insight into the pathophysiology of wound healing and the main routes to obtaining metallic nanoparticles. The methodology of synthesis, which is part of the so-called green synthesis, has been the focus of several studies on the use of medicinal plants as a substrate to produce silver, gold, and zinc nanoparticles. Their use as wound healing agents is closely related to their natural antimicrobial, anti-inflammatory, and cicatrizing properties. Finally, we address in vitro and in vivo studies on the efficiency of metallic nanoparticles (MNPs) synthesized from plant extracts and applied to wound healing in different pharmaceutical forms. For instance, the excellent wound contraction rates obtained from silver and gold NPs, respectively, were obtained from Euphorbia milii (92%) and Plectranthus aliciae (almost 97%) extracts in in vivo and in vitro analyses. Based on the satisfactory results, we find that MNPs are a potential therapeutic alternative compared to traditional synthetic healing agents and foresee the production of new pharmaceutical drugs. Full article