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Silver chalcogenide quantum dots (QDs) are potential nanosensors for biological and environmental applications. These QDs present low toxicity and their narrow band gap makes them promising as near-infrared (NIR) photoluminescence (PL) probes, exhibiting images with higher penetrability. In addition, hydrophilicity is essential for applications in biological systems as well as detection in aqueous media. Using the same methodology, variations in synthesis conditions can alter the efficiency and performance of their intrinsic properties. Most studies seek the best conditions for each experimental variable in a univariate manner; however, multivariate strategies are a faster and more economical way to achieve this goal. Thus, in this work, we utilized chemometric approaches to enhance the NIR-II PL properties of Ag2Se QDs stabilized with 3-mercaptopropionic acid (MPA). Three experimental designs were used, totaling 58 syntheses, showing that the Ag2Se–MPA QDs, obtained under the conditions of [Ag+] of 2.5 mmol L−1, Ag : Se molar ratio of 8 : 1, MPA : Ag molar ratio of 6 : 1, heating at 70 °C, pH 10, and 180 min, presented the best emission profile with a maximum at 1070 nm and a FWHM of approximately 140 nm. The nanocrystals presented an average diameter of 6 nm and the orthorhombic crystalline phase. Preliminary surface-enhanced infrared absorption (SEIRA) spectroscopy assays were carried out for the detection of methyl violet 2B (MV) dye using these QDs. The enhancement factor obtained was higher than 3.5, which is comparable to those observed for other systems, namely Ag2Se-MSA QDs. These results showed the potential of the Ag2Se–MPA QDs for (bio)sensing applications. [ABSTRACT FROM AUTHOR]

Quantum dots (QDs) have captured the attention of the scientific community due to their unique optical and electronic properties, leading to extensive research for different applications. They have also been employed as sensors for ionic species owing to their sensing properties. Detecting anionic species in an aqueous medium is a challenge because the polar nature of water weakens the interactions between sensors and ions. The anions bicarbonate (HCO3−), carbonate (CO32−), sulfate (SO42−), and bisulfate (HSO4−) play a crucial role in various physiological, environmental, and industrial processes, influencing the regulation of biological fluids, ocean acidification, and corrosion processes. Therefore, it is necessary to develop approaches capable of detecting these anions with high sensitivity. This study utilized CdTe QDs stabilized with cysteamine (CdTe-CYA) as a fluorescent sensor for these anions. The QDs exhibited favorable optical properties and high photostability. The results revealed a gradual increase in the QDs' emission intensity with successive anion additions, indicating the sensitivity of CdTe-CYA to the anions. The sensor also exhibited selectivity toward the target ions, with good limits of detection (LODs) and quantification (LOQs). Thus, CdTe-CYA QDs show potential as fluorescent sensors for monitoring the target anions in water sources. [ABSTRACT FROM AUTHOR]

The evolution of construction engineering depends on the development of cementitious materials with optimized properties and lower environmental impacts, such as the preparation of mortars with higher mechanical resistance and durability. Nanotechnology is a promising tool for industrial innovation, enhancing material properties like durability and mechanical performance. Thus, herein, we prepared mortars incorporating ZnO nanoparticles and evaluated their properties. The results showed that smaller percentages of ZnO presented better performance in consistency tests, and all samples containing ZnO showed higher mechanical resistance than the reference, thus suggesting the great potential of nanoparticles in optimizing the mechanical properties of mortars. [ABSTRACT FROM AUTHOR]

Quantum dots (QDs) are nanocrystal semiconductors that feature unique optical properties. However, they have a high density of dangling bonds on their surface, causing defects that can compromise their fluorescence. Their superficial passivation using another semiconductor is an alternative to reduce these defects. Herein, CdTe QDs stabilized with mercaptusuccinic acid (MSA) and cysteamine (CYA) were synthesized in water and coated with a ZnSe layer, forming a core–shell heterostructure. An improvement in photoluminescence greater than 300% was obtained for CdTe/ZnSe-MSA. However, for CdTe/ZnSe-CYA, the emission enhancement was around 55%. This study reinforces the importance of the experimental conditions to optimize QDs' emission. [ABSTRACT FROM AUTHOR]

The high industrial demand generates an increased consumption and a high waste of materials that impacts the environment in different spheres. One of the most affected environments are aquatic systems. Moreover, one of the most common forms of water contamination is the improper disposal of dyes by industries such as textiles, cosmetics, and pharmaceuticals. These dyes are organic substances that can give color to a substrate through chemical affinity. The most commonly used synthetic dyes are the ones containing the azo group, which have been reported as carcinogenic, mutagenic, and genotoxic, causing harm to the environment and living beings. Therefore, the study of methods that contribute to the degradation of these species will contribute to better treatment of polluted aquatic environments. Thus, the main objective of this work was to promote the catalytic degradation of organic dyes, such as Methyl Orange and Congo Red, through silver nanoparticles (AgNPs). For this, AgNPs were synthesized with spherical shapes using two stabilizers (polyvinylalcohol-PVA, and polyvinylpyrrolidone-PVP). Subsequently, the AgNPs were applied for the degradation of organic dyes, with the catalysis analyzed via UV-Vis absorption spectrometry in a maximum time of 40 min. Finally, it was observed that these nanocatalysts were successful in degrading the organic dyes. Thus, AgNPs have the potential to be used as catalysts for wastewater treatment. [ABSTRACT FROM AUTHOR]

Polyphosphate (PP) is an inorganic polymer formed by the condensation of orthophosphate groups and represented by the formula [PO3−]n. Due to its properties, such as biocompatibility and low toxicity, polyphosphate presents itself as a biomimetic compound of hydroxyapatite, the main constituent of bone tissue. PP can be applied for bone tissue applications as a ceramic material in the form of calcium polyphosphate (CPP), due to its chemical similarity with hydroxyapatite. Thus, CPP has been used to develop scaffolds for bone tissue repair. However, CPP does not have adequate mechanical properties for application in bone, requiring the use of substances that add other properties to the material, such as resistance to compression and tension. For this, polymers, ions, and nanoparticles have been used as additives. In this context, this work presents the development of composite materials based on CPP, PVA, and Mg2+ as candidates for bone applications. The production of materials was based on the precipitation of CPP in an aqueous medium containing a pre-solubilized polymer, followed by the addition of Mg2+. The materials were characterized by TGA, SEM, EDS, and Raman. The results confirmed the formation of the composites, presenting a porous structure and containing a Ca/P ratio of 0.90. Thus, these composites have the potential to be applied in bone regeneration applications. [ABSTRACT FROM AUTHOR]

Inadequate treatment of industrial waste causes the contamination of rivers and seas, impacting human health and aquatic biodiversity. Among the pollutants are industrial dyes, such as methylene blue (MB), which is toxic in high doses and prevents solar radiation from penetrating the water's surface. To reduce water pollution, the organic dyes could be degraded, generating less harmful and colorless substances. The use of nanoparticles as catalysts has been gaining attention since they have excellent catalytic activity due to their high surface-to-volume ratio. Thus, this work aims to study the use of silver nanoparticles (AgNPs) to degrade MB. AgNPs were prepared in water using the chemical reduction strategy and four different organic stabilizers: sodium citrate, ascorbic acid, polyvinylpyrrolidone, and poly(vinyl alcohol). The MB degradation in the presence of the AgNPs was monitored by UV-Vis absorption spectroscopy. The results showed the formation of AgNPs with a spherical shape for all the stabilizers used. All the AgNPs prepared were efficient in the degradation of MB, having degraded more than 90%. However, the AgNPs stabilized with sodium citrate and polyvinylpyrrolidone presented the best catalytic performance. Nevertheless, the four AgNPs prepared are potential catalysts for the degradation of organic dyes of wastewater. [ABSTRACT FROM AUTHOR]

Nanotechnology is a field that has advanced significantly in the last decades. Nanomaterials, as a result of their nanometric dimensions, exhibit unique properties that enhance their technological and biomedical applications. Metallic nanoparticles, like silver nanoparticles (AgNPs), have stood out due to their intrinsic properties, such as the localized surface plasmon resonance, which can be controlled by their size and shape. Thus, in this work, we have developed a practical synthetic procedure to obtain AgNPs with controlled morphology. AgNPs were prepared in water by the chemical reduction methodology, using different stabilizers under room temperature or with heating, and sodium borohydride as the reducing agent. The results obtained showed that the AgNPs were successfully prepared using polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP) as the stabilizing agents. The AgNPs' shape could be controlled by the absence or presence of H2O2, forming nanospheres or nanoprisms, respectively. The nanomaterials prepared exhibited colloidal stability with a negative surface charge, and TEM images confirmed their spherical and prismatic morphology. Furthermore, the results showed that the two synthesis conditions, room temperature and heating, afforded AgNPs in spherical and prismatic shapes; however, with temperature, the size distribution was lower. Thus, this methodology has the potential to be expanded to other stabilizing agents as a simple and practical method to prepare silver nanostructures with controlled morphology. [ABSTRACT FROM AUTHOR]

Near-infrared-emitting quantum dots (QDs) are very interesting for (bio)medical uses because they penetrate biological tissues more deeply and emit light in the biological diagnostic window, that is, the region from 650 to 1450 nm. Among the semiconductors with appropriate band gaps to provide photoluminescence at wavelengths longer than 650 nm, silver chalcogenides are distinguished mainly by being environmentally friendly. This work proposes the use of experimental design techniques to optimize a one-pot aqueous procedure to synthesize photoluminescent silver selenide (Ag2Se) QDs capped with mercaptosuccinic acid (MSA). The best conditions found were Ag/Se and MSA/Ag molar ratios of 8 : 1 and 6 : 1, respectively, pH 5.0, and stirring for 20 minutes at 60 °C. The Ag2Se nanocrystals synthesized under those experimental parameters showed a photoluminescence quantum yield of 16.3%, absorption edge at 583 nm, and emission within the biological diagnostic window, at 789 nm, with orthorhombic crystal structure and an average diameter of 5.7 nm. [ABSTRACT FROM AUTHOR]

In this study, we present the optimization of the optical properties of Mn2+ doped ZnSe QDs (also referred to as d-dots) coated with thioglycolic acid in aqueous medium. The nanoparticles were characterized by ionic coupled plasma, electron paramagnetic resonance, transmission electron microscopy and X-ray diffractometry. By applying a controlled dose of UV irradiation, we obtained efficient orange emitting d-dots (4T1→ 6A1 transition centered at 580 nm). The results point out to a doping fraction in the nanoparticles smaller than 1% (0.89%), and that the Mn2+ ions are preferentially located close to the particle's surface. The UV photoactivation procedure has a definite influence on the emission intensity and on the colloidal stability of the particles. Photoactivated Mn2+ d-dots were conjugated to Concanavalin A and labeled specifically Candida albicans yeast cells, by targeting carbohydrate residues depicting the successful use of these QDs as fluorescent probes. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Magnetic resonance imaging (MRI) is a powerful non-invasive diagnostic tool that enables distinguishing healthy from pathological tissues, with high anatomical detail. Nevertheless, MRI is quite limited in the investigation of molecular/cellular biochemical events, which can be reached by fluorescence-based techniques. Thus, we developed bimodal nanosystems consisting in hydrophilic quantum dots (QDs) directly conjugated to Gd(III)-DO3A monoamide chelates, a Gd(III)-DOTA derivative, allowing for the combination of the advantages of both MRI and fluorescence-based tools. These nanoparticulate systems can also improve MRI contrast, by increasing the local concentration of paramagnetic chelates. Transmetallation assays, optical characterization, and relaxometric analyses, showed that the developed bimodal nanoprobes have great chemical stability, bright fluorescence, and high relaxivities. Moreover, fluorescence correlation spectroscopy (FCS) analysis allowed us to distinguish nanosystems containing different amounts of chelates/QD. Also, inductively coupled plasma optical emission spectrometry (ICP - OES) indicated a conjugation yield higher than 75%. Our nanosystems showed effective longitudinal relaxivities per QD and per paramagnetic ion, at least 5 times [per Gd(III)] and 100 times (per QD) higher than the r1 for Gd(III)-DOTA chelates, suitable for T1-weighted imaging. Additionally, the bimodal nanoparticles presented negligible cytotoxicity, and efficiently labeled HeLa cells as shown by fluorescence. Thus, the developed nanosystems show potential as strategic probes for fluorescence analyses and MRI, being useful for investigating a variety of biological processes. [ABSTRACT FROM AUTHOR]

A green, fast and effective multivariate method for the determination of atrazine (ATZ) was developed using conventional infrared equipment furnished with an attenuated total reflectance module (ATR-IR), providing limit of detection (LOD) and limit of quantification (LOQ) in the ranges from 1.9 to 4.6 µg/mL and from 5.6 to 14 µg/mL, respectively. Furthermore, the surface-enhanced infrared absorption (SEIRA) approach was investigated to improve the sensitivity of the measurements and detect ATZ at low concentrations, addressing the compatibility with reference methods. To this end, a substrate formed by silver selenide quantum dots stabilized with mercaptopropionic acid (Ag 2 Se/MPA), synthesized in aqueous medium by an one-pot synthesis, was used. The spectral data were investigated by univariate and multivariate calibrations, allowing to calculate the enhancement factor (EF) and the multivariate enhancement factor (MEF), respectively. The SEIRA strategy proved to be able to enhance the atrazine signal up to 86-fold, allowing the detection of ATZ at concentrations as low as 0.001 µg/mL., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Water contamination represents a significant ecological impact with global consequences, contributing to water scarcity worldwide. The presence of several pollutants, including heavy metals, pharmaceuticals, pesticides, and pathogens, in water resources underscores a pressing global concern, prompting the European Union (EU) to establish a Water Watch List to monitor the level of these substances. Nowadays, the standard methods used to detect and quantify these contaminants are mainly liquid or gas chromatography coupled with mass spectrometry (LC/GC-MS). While these methodologies offer precision and accuracy, they require expensive equipment and experienced technicians, and cannot be used on the field. In this context, chalcogenide quantum dots (QDs)-based sensors have emerged as promising, user-friendly, practical, and portable tools for environmental monitoring. QDs are semiconductor nanocrystals that possess excellent properties, and have demonstrated versatility across various sensor types, such as fluorescent, electrochemical, plasmonic, and colorimetric ones. This review summarizes recent advances (2019-2023) in the use of chalcogenide QDs for environmental sensing, highlighting the development of sensors capable of detect efficiently heavy metals, anions, pharmaceuticals, pesticides, endocrine disrupting compounds, organic dyes, toxic gases, nitroaromatics, and pathogens., Competing Interests: Declaration of competing interest The authors confirm that there are no conflicts of interest in this work., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

We report the development of a new nanostructured electrochemical immunosensing platform for the detection of the Zika virus envelope protein (EP-ZIKV). For this, quantum dots (QDs) were explored in combination with screen-printed carbon electrodes (SPCEs) functionalized with a conductor polymeric film, formed from 2-(1H-pyrrol-1-yl)ethanamine (Py am ), and anti-EP DIII ZIKV antibodies. Carboxylated CdTe QDs were synthesized, characterized by optical and structural techniques, and covalently immobilized onto the SPCE/PPy am surface. Then, anti-EP ZIKV antibodies were also covalently conjugated to QDs. All stages of platform assembly were evaluated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The detection of EP-ZIKV was performed by differential pulse voltammetry (DPV). Results indicated that QDs were efficiently immobilized, and did not show oxidation, under the conditions evaluated, for at least 7 months. Anti-EP ZIKV antibodies were effectively immobilized on the PPy am /QDs surface, even after 2 months of electrode storage. The platform enabled the detection of EP-ZIKV with high sensitivity using minimal sample volumes (LOD = 0.1 ng mL -1 and LOQ = 0.4 ng mL -1 ). The platform was also able to detect EP-ZIKV in spiked serum samples. Moreover, the platform showed specificity, not detecting the EP-DENV 3 nor a mixture of four DENV serotypes antigens. Thus, the proposed combination favored the development of a sensitive immunosensing platform, promising for the detection of Zika in the viremic phase, which also holds potential for transposition to other arboviruses., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Sialic acids (SAs) modulate essential physiological and pathological conditions, including cell-cell communication, immune response, neurological disorders, and cancer. Besides, SAs confer negative charges to cell membranes, also contributing to hemorheology. Phenylboronic acids, called as mimetic lectins, have been highlighted to study SA profiles. The association of these interesting molecules with the optical properties of quantum dots (QDs) can provide a deeper/complementary understanding of mechanisms involving SAs. Herein, we explored the thiol affinity to the QD surface to develop a simple, fast and direct attachment procedure to functionalize these nanocrystals with 3-mercaptophenylboronic acids (MPBAs). The functionalization was confirmed by fluorescence correlation spectroscopy and inductively coupled plasma spectrometry. The conjugate specificity/efficiency was proved in experiments using red blood cells (RBCs). A labeling >90% was found for RBCs incubated with conjugates, which reduced to 17% after neuraminidase pretreatment. Moreover, QDs-MPBA conjugates were applied in a comparative study using acute (KG-1) and chronic (K562) myelogenous leukemia cell lines. Results indicated that KG-1 membranes have a greater level of SA, with 100% of cells labeled and a median of fluorescence intensity of ca. 2.5-fold higher when compared to K562 (94%). Therefore, this novel QDs-MPBA conjugate can be considered a promising nanoplatform to evaluate SA contents in a variety of biological systems., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Zika virus (ZIKV) has been declared a public health emergency of international concern. ZIKV has been associated with some neurological disorders, and their long-term effects are not completely understood. The majority of the methods for ZIKV diagnosis are based on the detection of IgM antibodies, which are the first signs of immunological response. However, the detection of IgG antibodies can be an important approach for ZIKV past infection diagnosis, especially for pregnant women, helping the comprehension/treatment of this disease. There has been a growing interest in applying nanoparticles for efficient ZIKV or antibodies detection. Quantum dots (QD) are unique fluorescent semiconductor nanoparticles, highly versatile for biological applications. In the present study, we explored the special QD optical properties to develop an immunofluorescence assay for anti-ZIKV IgG antibodies detection. Anti-IgG antibodies were successfully conjugated with QDs and applied in a fluorescence sensing nanoplatform. After optimization using IgG antibodies, the conjugates were employed to detect anti-ZIKV IgG antibodies in polystyrene microplates sensitized with ZIKV envelope E protein. The nanoplatform was able to detect anti-ZIKV IgG antibodies in a concentration at least 100-fold lower than the amount expected for protein E immune response. Moreover, conjugates were able to detect the antibodies for at least 4 months. Thus, our results showed that this QDs-based fluoroimmunoplatform can be considered practical, simple and promising to detect Zika past infections and/or monitoring immune response in vaccine trials., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Background: Site-specific multimodal nanoplatforms with fluorescent-magnetic properties have great potential for biological sciences. For this reason, we developed a multimodal nanoprobe (BNPs-Tf), by covalently conjugating an optical-magnetically active bimodal nanosystem, based on quantum dots and iron oxide nanoparticles, with the human holo-transferrin (Tf)., Methods: The Tf bioconjugation efficiency was evaluated by the fluorescence microplate assay (FMA) and the amount of Tf immobilized on BNPs was quantified by fluorescence spectroscopy. Moreover, relaxometric and fluorescent properties of the BNPs-Tf were evaluated, as well as its ability to label specifically HeLa cells. Cytotoxicity was also performed by Alamar Blue assay., Results: The FMA confirmed an efficient bioconjugation and the fluorescence spectroscopy analysis indicated that 98% of Tf was immobilized on BNPs. BNPs-Tf also presented a bright fluorescence and a transversal/longitudinal relaxivities ratio (r 2 /r 1 ) of 65. Importantly, the developed BNPs-Tf were able to label, efficiently and specifically, the Tf receptors in HeLa cells, as shown by fluorescence and magnetic resonance imaging assays. Moreover, this multimodal system did not cause noteworthy cytotoxicity., Conclusions: The prepared BNPs-Tf hold great promise as an effective and specific multimodal, highly fluorescent-magnetic, nanoplatform for fluorescence analyses and T 2 -weighted images., General Significance: This study developed an attractive and versatile multimodal nanoplatform that has potential to be applied in a variety of in vitro and in vivo studies, addressing biological processes, diagnostic, and therapeutics. Moreover, this work opens new possibilities for designing other efficient multimodal nanosystems, considering other biomolecules in their composition able to provide them important functional properties., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Background: Overexpression of transferrin receptors (TfRs), which are responsible for the intracellular uptake of ferric transferrin (Tf), has been described in various cancers. Although molecular biology methods allow the identification of different types of receptors in cancer cells, they do not provide features about TfRs internalization, quantification and distribution on cell surface. This information can, however, be accessed by fluorescence techniques. In this work, the quantum dots (QDs)' unique properties were explored to strengthen our understanding of TfRs in cancer cells., Methods: QDs were conjugated to Tf by covalent coupling and QDs-(Tf) bioconjugates were applied to quantify and evaluate the distribution of TfRs in two human glioblastoma cells lines, U87 and DBTRG-05MG, and also in HeLa cells by using flow cytometry and confocal microscopy., Results: HeLa and DBTRG-05MG cells showed practically the same TfR labeling profile by QDs-(Tf), while U87 cells were less labeled by bioconjugates. Furthermore, inhibition studies demonstrated that QDs-(Tf) were able to label cells with high specificity., Conclusions: HeLa and DBTRG-05MG cells presented a similar and a higher amount of TfR than U87 cells. Moreover, DBTRG-05MG cells are more efficient in recycling the TfR than the other two cells types., General Significance: This is the first study about TfRs in human glioblastoma cells using QDs. This new fluorescent tool can contribute to our understanding of the cancer cell biology and can help in the development of new therapies targeting these receptors.