Glutathione regulation-based dual-functional upconversion sensing-platform for acetylcholinesterase activity and cadmium ions

Aptamer-free upconversion nanoparticle/silk biosensor system for low-cost and highly sensitive detection of antibiotic residues

The detection of antibiotics is crucial for safeguarding the environment, ensuring food safety, and promoting human health. However, developing a rapid, convenient, low-cost, and sensitive method for antibiotic detection presents significant challenges. Herein, an aptamer-free biosensor was successfully constructed using upconversion nanoparticles (UCNPs) coated with silk fibroin (SF), based on Förster resonance energy transfer (FRET) and the charge-transfer effect, for detecting roxithromycin (RXM). A synergistic FRET efficiency was achieved by utilizing alizarin red and RXM complexes as energy acceptors, with UCNP as the energy donor, and immobilizing an ultrathin SF protein corona within 10 nm. The biosensor detects RXM in deionized water with high sensitivity primarily through monolayer adsorption, with a detection range of 1.0 nM-141.6 nM and a detection limit as low as 0.68 nM. The performance of this biosensor was compared with the ultra-performance liquid chromatography-mass spectrometry (UPLC-MS/MS) method for detecting antibiotics in river water separately and a strong correlation between the two methods was observed. The biosensor exhibited long-term stability in aqueous solutions (up to 60 d) with no attenuation of fluorescence intensity. Furthermore, the biosensor's applicability extended to the highly sensitive detection of other antibiotics, such as azithromycin. This study introduces a low-cost, eco-friendly, and highly sensitive method for antibiotic detection, with broad potential for future applications in environmental, healthcare, and food-related fields.

Design, synthesis, and evaluation of a carboxylesterase detection probe with therapeutic effects

In this study, a lysosomal targeting fluorescent probe recognition on CEs was designed and synthesized. The obtained probe BF2-cur-Mor demonstrated excellent selectivity, sensitivity, pH-independence, and enzyme affinity towards CEs within 5 min. BF2-cur-Mor could enable recognition of intracellular CEs and elucidate that the CEs content of different cancer cells follows the rule of HepG2 > HCT-116 > A549 > HeLa, and the CEs expression level of hepatoma cancer cells far exceeds that of normal hepatic cells, being in good agreement with the previous reports. The ability of BF2-cur-Mor to monitor CEs in vivo was confirmed by zebrafish experiment. BF2-cur-Mor exhibits some pharmacological activity in that it can induce apoptosis in hepatocellular carcinoma cells but is weaker in normal hepatocyte cells, being expected to be a potential "diagnostic and therapeutic integration" tool for the clinical diagnosis of CEs-related diseases.

A ratiometric fluorescent probe with a large Stokes shift for the detection of Hg2+ and its applications in environmental sample and living system analysis

Toxic mercury ions (Hg2+) can cause serious environmental pollution and accumulate in living organisms via the food chain. Therefore, monitoring Hg2+ is crucial in ensuring the safety of ecosystems and organisms. In this work, a novel ratiometric fluorescent probe CMT (5-(4-(diphenylamino)phenyl)-1-(7-hydroxy-coumarin-3-yl)-4-pentene-1,3-dione) based on coumarin was developed for detecting Hg2+, which displayed obvious fluorescence changes, a low detection limit (2.24 × 10-7 M), good selectivity, and a large Stokes shift (255 nm). The CMT probe could detect Hg2+ in real environmental soil and water samples. Furthermore, the CMT probe enabled the naked-eye detection of Hg2+ using test paper experiments. CMT was also applied for fluorescence imaging in living zebrafish and plants. This work provides a highly efficient tool for monitoring Hg2+ in environmental samples and biological systems.

Plasmon Modulated Upconversion Biosensors

Over the past two decades, lanthanide-based upconversion nanoparticles (UCNPs) have been fascinating scientists due to their ability to offer unprecedented prospects to upconvert tissue-penetrating near-infrared light into color-tailorable optical illumination inside biological matter. In particular, luminescent behavior UCNPs have been widely utilized for background-free biorecognition and biosensing. Currently, a paramount challenge exists on how to maximize NIR light harvesting and upconversion efficiencies for achieving faster response and better sensitivity without damaging the biological tissue upon laser assisted photoactivation. In this review, we offer the reader an overview of the recent updates about exciting achievements and challenges in the development of plasmon-modulated upconversion nanoformulations for biosensing application.

A Comprehensive Review on Upconversion Nanomaterials-Based Fluorescent Sensor for Environment, Biology, Food and Medicine Applications

Near-infrared-excited upconversion nanoparticles (UCNPs) have multicolor emissions, a low auto-fluorescence background, a high chemical stability, and a long fluorescence lifetime. The fluorescent probes based on UCNPs have achieved great success in the analysis of different samples. Here, we presented the research results of UCNPs probes utilized in analytical applications including environment, biology, food and medicine in the last five years; we also introduced the design and construction of upconversion optical sensing platforms. Future trends and challenges of the UCNPs used in the analytical field have also been discussed with particular emphasis.

Applications of upconversion nanoparticles in analytical and biomedical sciences: a review

Lanthanide-doped upconversion nanoparticles (UCNPs) have gained more attention from researchers due to their unique properties of photon conversion from an excitation/incident wavelength to a more suitable emission wavelength at a designated site, thus improving the scope in the life sciences field. Due to their fascinating and unique optical properties, UCNPs offer attractive opportunities in theranostics for early diagnostics and treatment of deadly diseases such as cancer. Also, several efforts have been made on emerging approaches for the fabrication and surface functionalization of luminescent UCNPs in optical biosensing applications using various infrared excitation wavelengths. In this review, we discussed the recent advancements of UCNP-based analytical chemistry approaches for sensing and theranostics using a 980 nm laser as the excitation source. The key analytical merits of UNCP-integrated fluorescence analytical approaches for assaying a wide variety of target analytes are discussed. We have described the mechanisms of the upconversion (UC) process, and the application of surface-modified UCNPs for in vitro/in vivo bioimaging, photodynamic therapy (PDT), and photothermal therapy (PTT). Based on the latest scientific achievements, the advantages and disadvantages of UCNPs in biomedical and optical applications are also discussed to overcome the shortcomings and to improve the future study directions. This review delivers beneficial practical information of UCNPs in the past few years, and insights into their research in various fields are also discussed precisely.

Redox-Responsive Breakup of a Nucleic Acids@CoOOH Nanocomplex Triggering Cascade Recycling Amplification for Sensitive Sensing of Alkaline Phosphatase

Alkaline phosphatase (ALP), an essential hydrolase with crucial roles in living organisms, has widely been regarded as a biomarker for various human diseases in clinical diagnoses. Herein, taking advantage of cobalt oxyhydroxide (CoOOH) nanoflakes and nonenzymatic cascade recycling amplification (CRA), a highly sensitive and label-free fluorescence biosensing strategy for the determination of ALP activity is introduced. In our design, ALP can promote the dephosphorylation of l-ascorbic acid 2-phosphate (AAP) to reduce ascorbic acid (AA), which is then able to decompose CoOOH in a nucleic acids@CoOOH nanocomplex into Co²⁺ cofactors. Further, enzyme-free CRA was rapidly initiated by integrating DNAzyme recycling amplification and catalytic hairpin assembly, resulting in the generation of an abundance of G-quadruplex structure-contained DNA duplexes. In the presence of thioflavin T (ThT), analytical target ALP was converted in an amplified and activatable fluorescence signal. The experimental results show that this method can be applied for the quantitative analysis of ALP activity with a low detection limit of 0.027 mU/mL. Moreover, this developed biosensing approach exhibits excellent specificity, and the evaluation of ALP activity in the complex human serum samples was successfully realized, indicating that it can afford a reliable, robust, and cost-effective nanoplatform for an ALP-based clinical diagnosis and for biomedical research.

Construction of a colorimetric sensor array based on the coupling reaction to identify phenols

Phenols are harmful to the human body and the environment. Since there are a variety of phenols in actual samples, this requires a sensor which possesses the ability to simultaneously distinguish them. Herein, we report a colorimetric sensor array, which uses two nanozymes (Fe-N-C nanozymes and Cu-N-C nanozymes) as electronic tongues for fingerprint identification of six phenols (2,4,6-trichlorophenol (2,4,6-Tri), 4-nitrophenol (P-np), phenol (Phe), 3-chlorophenol (3-CP), 4-chlorophenol (4-CP), and o-nitrophenol (O-np)) in the environment. Nanozymes catalyzed the reaction of hydrogen peroxide, different phenols and 4-aminoantipyrine (4-AAP) to produce different color variations. These signal changes as fingerprints encouraged us to develop a pattern recognition method for the identification of phenols by linear discriminant analysis (LDA). The six phenols at 50 nM have their own response patterns, respectively. Surprisingly, this sensor array had distinguished the six phenols in actual samples successfully.

The dichotomy of nanotechnology as the cutting edge of agriculture: Nano-farming as an asset versus nanotoxicity

The unprecedented setbacks and environmental complications, faced by global agro-farming industry, have led to the advent of nanotechnology in agriculture, which has been recognized as a novel and innovative approach in development of sustainable farming practices. The agricultural regimen is the "head honcho" of the world, however presently certain approaches have been imposing grave danger to the environment and human civilization. The nano-farming paradigm has successfully elevated the growth and development of plants, parallel to the production, quality, germination/transpiration index, photosynthetic machinery, genetic progression, and so on. This has optimized the traditional farming into precision farming, utilising nano-based sensors and nanobionics, smart delivery tools, nanotech facets in plant disease management, nanofertilizers, enhancement of plant adaptive potential to external stress, role in bioenergy conservation and so on. These applications portray nanorevolution as "the big cheese" of global agriculture, mitigating the bottlenecks of conventional practices. Besides the applications of nanotechnology, the review identifies the limitations, like possible harmful impact on environment, mankind and plants, as the "Achilles heel" in agro-industry, aiming to establish its defined role in agriculture, while simultaneously considering the risks, in order to resolve them, thus abiding by "technology-yes, but safety-must". The authors aim to provide a significant opportunity to the nanotech researchers, Botanists and environmentalists, to promote judicial use of nanoparticles and establish a secure and safe environment.

Advances in fluorescence sensing enabled by lanthanide-doped upconversion nanophosphors

Lanthanide-doped upconversion nanoparticles (UCNPs), characterized by converting low-energy excitation to high-energy emission, have attracted considerable interest due to their inherent advantages of large anti-Stokes shifts, sharp and narrow multicolor emissions, negligible autofluorescence background interference, and excellent chemical- and photo-stability. These features make them promising luminophores for sensing applications. In this review, we give a comprehensive overview of lanthanide-doped upconversion nanophosphors including the fundamental principle for the construction of UCNPs with efficient upconversion luminescence (UCL), followed by state-of-the-art strategies for the synthesis and surface modification of UCNPs, and finally describing current advances in the sensing application of upconversion-based probes for the quantitative analysis of various analytes including pH, ions, molecules, bacteria, reactive species, temperature, and pressure. In addition, emerging sensing applications like photodetection, velocimetry, electromagnetic field, and voltage sensing are highlighted.

Versatile Sensing Platform of Innovative Copper Oxide Assisted Cu-Phenolic Coordination Nanosheet mediated Fluorophore tagged GT-rich SSA based Fluorescence ON-OFF Biosensor for Subsequent Detection of Cd2+ and S2− Ions

Increased levels of toxic metal/non-metal ions Cadmium (Cd2+) and Sulfide (S2−) in the environment can be detrimental to human health. Given the circumstances, the detection and measurement of Cd2+ and...

A sensitive fluorescence biosensor based on metal ion-mediated DNAzyme activity for amplified detection of acetylcholinesterase

In this paper, we developed an amplified fluorescence biosensor for acetylcholinesterase (AChE) activity detection by taking advantage of the mercury ion-mediated Mgzyme (Mg2+-dependent DNAzyme) activity.

A veratraldehyde-appended organosilicon probe and its hybrid silica nanoparticles as a dual chemosensor for colorimetric and fluorimetric detection of Cu2+ and Fe3+ ions

Schiff bases of veratraldehyde based organosilatranes have been synthesized. The colorimetric and fluorimetric detection of 3a and its hybrid silica nanoparticles (V-NPs) revealed significant sensorial ability only towards Cu2+ and Fe3+ ions.

In vitro bio-accessibility and distribution characteristic of each arsenic species in different fishes and shellfishes/shrimps collected from Fujian of China

It is very important to consider the bio-accessibilities and concentrations of each arsenic species, not total arsenic, in seafood in order to accurately assess internal exposure level and health risk of arsenic from seafood. Herein, the concentrations and in vitro bio-accessibilities of each arsenic species in various fishes and shellfishes/shrimps were extensively investigated. Experimental results showed that arsenic species and contents in shellfishes/fishes remarkably varied with the difference of fish/shellfish species or individuals and sampling area, and arsenobetaine (AsB) is dominant arsenic species for fishes and shellfishes/shrimps. Different arsenic species in the same fish/shellfish have quite different bio-accessibilities, and the bio-accessibilities of each arsenic species also varied with fish/shellfish species or individuals. As³⁺ in fishes/shellfishes was partly oxidized to form As⁵⁺ during gastrointestinal digestion, and thus it is more reasonable and practicable to evaluate the bio-accessibilities of inorganic arsenic (iAs, total As³⁺ and As⁵⁺), not individual As³⁺ and As⁵⁺. Fishes and shellfishes/shrimps have similar bio-accessibilities of iAs, AsB and total arsenic, whereas have different bio-accessibilities of MMA (monomethylarsonic acid), DMA (dimethylarsinic acid), and two un-identified arsenic (Ui-As1 and Ui-As2). The results of this study provided a valuable knowledge for accurately assessing the health risk of arsenic in seafood.

Exploring the use of upconversion nanoparticles in chemical and biological sensors: from surface modifications to point-of-care devices

Upconversion nanoparticles (UCNPs) have emerged as promising luminescent nanomaterials due to their unique features that allow the overcoming of several problems associated with conventional fluorescent probes. Although UCNPs have been used in a broad range of applications, it is probably in the field of sensing where they best evidence their potential. UCNP-based sensors have been designed with high sensitivity and selectivity, for detection and quantification of multiple analytes ranging from metal ions to biomolecules. In this review, we deeply explore the use of UCNPs in sensing systems emphasizing the most relevant and recent studies on the topic and explaining how these platforms are constructed. Before diving into UCNP-based sensing platforms it is important to understand the unique characteristics of these nanoparticles, why they are attracting so much attention, and the most significant interactions occurring between UCNPs and additional probes. These points are covered over the first two sections of the article and then we explore the types of fluorescent responses, the possible analytes, and the UCNPs' integration with various material types such as gold nanostructures, quantum dots and dyes. All the topics are supported by analysis of recently reported sensors, focusing on how they are built, the materials' interactions, the involved synthesis and functionalization mechanisms, and the conjugation strategies. Finally, we explore the use of UCNPs in paper-based sensors and how these platforms are paving the way for the development of new point-of-care devices.

Photoluminescent Nanoparticles for Chemical and Biological Analysis and Imaging

Research related to the development and application of luminescent nanoparticles (LNPs) for chemical and biological analysis and imaging is flourishing. Novel materials and new applications continue to be reported after two decades of research. This review provides a comprehensive and heuristic overview of this field. It is targeted to both newcomers and experts who are interested in a critical assessment of LNP materials, their properties, strengths and weaknesses, and prospective applications. Numerous LNP materials are cataloged by fundamental descriptions of their chemical identities and physical morphology, quantitative photoluminescence (PL) properties, PL mechanisms, and surface chemistry. These materials include various semiconductor quantum dots, carbon nanotubes, graphene derivatives, carbon dots, nanodiamonds, luminescent metal nanoclusters, lanthanide-doped upconversion nanoparticles and downshifting nanoparticles, triplet-triplet annihilation nanoparticles, persistent-luminescence nanoparticles, conjugated polymer nanoparticles and semiconducting polymer dots, multi-nanoparticle assemblies, and doped and labeled nanoparticles, including but not limited to those based on polymers and silica. As an exercise in the critical assessment of LNP properties, these materials are ranked by several application-related functional criteria. Additional sections highlight recent examples of advances in chemical and biological analysis, point-of-care diagnostics, and cellular, tissue, and in vivo imaging and theranostics. These examples are drawn from the recent literature and organized by both LNP material and the particular properties that are leveraged to an advantage. Finally, a perspective on what comes next for the field is offered.

Lanthanide ion (Ln3+ )-based upconversion sensor for quantification of food contaminants: A review

The food safety issue has gradually become the focus of attention in modern society. The presence of food contaminants poses a threat to human health and there are a number of interesting researches on the detection of food contaminants. Upconversion nanoparticles (UCNPs) are superior to other fluorescence materials, considering the benefits of large anti-Stokes shifts, high chemical stability, non-autofluorescence, good light penetration ability, and low toxicity. These properties render UCNPs promising candidates as luminescent labels in biodetection, which provides opportunities as a sensitive, accurate, and rapid detection method. This paper intended to review the research progress of food contaminants detection by UCNPs-based sensors. We have proposed the key criteria for UCNPs in the detection of food contaminants. Additionally, it highlighted the construction process of the UCNPs-based sensors, which includes the synthesis and modification of UCNPs, selection of the recognition elements, and consideration of the detection principle. Moreover, six kinds of food contaminants detected by UCNPs technology in the past 5 years have been summarized and discussed fairly. Last but not least, it is outlined that UCNPs have great potential to be applied in food safety detection and threw new insight into the challenges ahead.

Inner filter effect between upconversion nanoparticles and Fe(ii)-1,10-phenanthroline complex for the detection of Sn(ii) and ascorbic acid (AA)

Dual-function and multi-function sensors can use the same material or detection system to achieve the purpose of detection of two or more substances. Due to their high sensitivity and specificity, dual-function and multi-function sensors have potential applications in many fields. In this article, we designed a dual-function sensor to detect Sn(ii) and ascorbic acid (AA) based on the inner filter effect (IFE) between NaYF₄:Yb,Er@NaYF₄@PAA (UCNPs@PAA) and Fe(ii)–1,10-phenanthroline complex. Fe(ii)–1,10-phenanthroline complex has strong absorption in most of the ultraviolet-visible light range (350 nm–600 nm), and this absorption band overlaps with the green emission peak of UCNPs@PAA at 540 nm; Fe(ii)–1,10-phenanthroline complex can significantly quench the green light emission of UCNPs@PAA. When Sn(ii) or AA is added to the UCNPs@PAA/Fe(iii)/1,10-phenanthroline, they can reduce Fe(iii) to Fe(ii). Fe(ii) can react with 1,10-phenanthroline to form an orange complex, thereby quenching the green light emission of UCNPs@PAA. And the quenching efficiency is related to the concentration of Sn(ii) and AA; there is a linear relationship between quenching efficiency and the concentration of Sn(ii) and AA, within a certain concentration range the detection limits of this dual-function sensor for Sn(ii) and AA are 1.08 μM and 0.97 μM, respectively. In addition, the dual-function sensor can also detect Sn(ii) and AA in tap and spring water.

Based on the inner filter effect (IFE), we use UCNPs to develop a dual-function sensors, which can realize sensitive and selective detection for the Sn(ii) and ascorbic acid (AA).

Sensitive colorimetric assay for the determination of alkaline phosphatase activity utilizing nanozyme based on copper nanoparticle-modified Prussian blue

Nanozyme based on Prussian blue nanocubes (PB NCs) loaded with copper nanoparticles (Cu@PB NCs) was synthesized. The peroxidase (POD)-like activity of Cu@PB NCs was studied and utilized for detecting the activity of alkaline phosphatase (ALP). The Cu@PB NCs possess higher POD-like activity compared with PB NCs and natural horseradish peroxidase (HRP) due to the loading of copper nanoparticles. 3,3',5,5'-Tetramethylbenzidine (TMB) can be oxidized to oxTMB in the presence of Cu@PB NCs and H₂O₂, generating blue-colored compound, while introduction of pyrophosphate (PPi) leads to the POD-like activity of Cu@PB NCs decreased obviously. In the presence of ALP, PPi was hydrolyzed and then the POD-like activity of Cu@PB NCs was restored. So, according to the change of the POD-like activity of Cu@PB NCs, a sensitive colorimetric assay for ALP activity was reported. The limit of detection of the assay is 0.08 mU/mL, with linear range from 0.1 to 50 mU/mL. In addition, the assay was also applied for screening the inhibitors of ALP. Nanozyme based on Prussian blue nanocube (PB NCs) loaded with copper nanoparticles was synthesized and utilized for detecting the activity of alkaline phosphatase (ALP).

An overview of nanomaterial based biosensors for detection of Aflatoxin B1 toxicity in foods

Aflatoxin B1 (AFB1) is one of the most potent mycotoxin contaminating several foods and feeds. It suppresses immunity and consequently increases mutagenicity, carcinogenicity, teratogenicity, hepatotoxicity, embryonic toxicity and increasing morbidity and mortality. Continuous exposure of AFB1 causes liver damage and thus increases the prevalence of cirrhosis and hepatic cancer. This article was planned to provide understanding of AFB1 toxicity and provides future directions for fabrication of cost effective and user-friendly nanomaterials based analytical devices. In the present article various conventional (chromatographic & spectroscopic), modern (PCR & immunoassays) and nanomaterials based biosensing techniques (electrochemical, optical, piezoelectrical and microfluidic) are discussed alongwith their merits and demerits. Nanomaterials based amperometric biosensors are found to be more stable, selective and cost-effective analytical devices in comparison to other biosensors. But many unresolved issues about their stability, toxicity and metabolic fate needs further studies. In-depth studies are needed for development of advanced nanomaterials integrated biosensors for specific, sensitive and fast monitoring of AFB1 toxicity in foods. Integration of biosensing system with micro array technology for simultaneous and automated detection of multiple AFs in real samples is also needed. Concerted efforts are also required to reduce their possible hazardous consequences of nanomaterials based biosensors.

Exploring Heterostructured Upconversion Nanoparticles: From Rational Engineering to Diverse Applications

Upconversion nanoparticles (UCNPs) represent a class of optical nanomaterials that can convert low-energy excitation photons to high-energy fluorescence emissions. On the basis of UCNPs, heterostructured UCNPs, consisting of UCNPs and other functional counterparts (metals, semiconductors, polymers, etc.), present an intriguing system in which the physicochemical properties are largely influenced by the entire assembled particle and also by the morphology, dimension, and composition of each individual component. As multicomponent nanomaterials, heterostructured UCNPs can overcome challenges associated with a single component and exhibit bifunctional or multifunctional properties, which can further expand their applications in bioimaging, biodetection, and phototherapy. In this review, we provide a summary of recent achievements in the field of heterostructured UCNPs in the aspects of construction strategies, synthetic approaches, and types of heterostructured UCNPs. This review also summarizes the trends in biomedical applications of heterostructured UCNPs and discusses the challenges and potential solutions in this field.

Nanomaterials for Agricultural and Ecological Defense Applications: Active Agents and Sensors

The world we live in today is overpopulated with an unprecedented number of people competing for fewer and fewer precious resources. The struggle to efficiently steward and manage these resources is a global problem in need of concrete and urgent solutions. Nanomaterials have driven innovation in diverse industrial sectors including military, aviation, electronic, and medical among others. Nanoscale materials possess unique surfaces and exquisite opto-electronic properties that make them uniquely suited to environmental, biological, and ecological defense applications. A tremendous upsurge of research activity in these areas is evident from the exponential increase in publications worldwide. Here we review recent applications of nanomaterials toward soil health and management, abiotic and biotic stress management, plant defense, delivery of the RNA Interference (RNAi), plant growth, manufacture of agro-products, and ecological investigations related to farming. For example, nanomaterial constructs have been used to counter environmental stresses and in plant defense and disease diagnosis. Nanosensor chemistries have been developed to monitor water quality and measure specific pollutant levels. Specific nanomaterials such as silver, iron oxide, and zinc oxide proffer protection to plants from pathogens. This review describes progress in nanomaterial-based agricultural and ecological defense and seeks to identify factors that would enable their wider commercialization and deployment. This article is categorized under: Diagnostic Tools > Biosensing Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials Diagnostic Tools > Diagnostic Nanodevices.

Fe-N-C single-atom nanozymes with peroxidase-like activity for the detection of alkaline phosphatase

Single-atom nanozymes have drawn wide attention in bio-sensing for their remarkable merits such as low cost, high stability, and maximum atom utilization. Herein, a colorimetric strategy based on Fe-N-C single-atom nanozymes (Fe/NC-SAs) was established for the detection of alkaline phosphatase (ALP) activity. The Fe/NC-SAs prepared by pyrolysis have excellent peroxidase-like activity and can oxidize 3,3',5,5'-tetramethylbenzidine (TMB) to a blue color product in the presence of hydrogen peroxide (H₂O₂). When ascorbic acid (AA) is added to the system, the blue color fades, and the absorbance has a linear relationship with the concentration of AA. Alkaline phosphatase (ALP) can catalyze the hydrolysis of ascorbic acid 2-phosphate (AAP) to produce AA. Thus, a strategy based on Fe/NC-SAs for the detection of ALP activity was established, which provided a linear range of 0.1-1.5 U L^-1 and a limit of detection as low as 0.05 U L^-1. Besides, Fe/NC-SAs showed high stability under harsh conditions. Moreover, an Fe/NC-SA-based assay was successfully validated using human serum samples for ALP determination with satisfactory results, and has broad prospects in the field of biosensing.

The facile and additive-free synthesis of a cell-friendly iron(iii)-glutathione complex

The straightfoward creation of an unreported glutathione-stabilised iron(iii) complex is disclosed. In contrast to previous reports, glutathione was shown to coordinate and stabilise iron directly under physiological conditions in the absence of additional sulfur containing molecules, such as sodium sulfide. The complex was extensively characterised; the molecular geometry was determined as two inequivalent octahedra, approximately 2/3 of which are slightly distorted towards more tetrahedral in character, with the remaining 1/3 more regularly octahedral. The dispersion of the iron(iii)-glutathione complex in aqueous solution yielded particles of 255 ± 4 nm in diameter that enhanced the growth and proliferation of L929 fibroblast cells over 7 days, and inhibited the activity of matrix metalloproteinase-13. Consequently, the unprecedented glutathione-stabilised iron(iii) complex disclosed has potential use as a simple-to-prepare growth factor for inclusion within cell culture media, and is an excellent candidate as a therapeutic for the treatment of metalloproteinase-13-associated diseases.

Plasmon-Emitter Hybrid Nanostructures of Gold Nanorod-Quantum Dots with Regulated Energy Transfer as a Universal Nano-Sensor for One-step Biomarker Detection

Recently, biosensing based on weak coupling in plasmon-emitter hybrid nanostructures exhibits the merits of simplicity and high sensitivity, and attracts increasing attention as an emerging nano-sensor. In this study, we propose an innovative plasmon-regulated fluorescence resonance energy transfer (plasmon-regulated FRET) sensing strategy based on a plasmon-emitter hybrid nanostructure of gold nanorod-quantum dots (Au NR-QDs) by partially modifying QDs onto the surfaces of Au NRs. The Au NR-QDs showed good sensitivity and reversibility against refractive index change. We successfully employed the Au NR-QDs to fabricate nano-sensors for detecting a cancer biomarker of alpha fetoprotein with a limit of detection of 0.30 ng/mL, which displays that the sensitivity of the Au NR-QDs nano-sensor was effectively improved compared with the Au NRs based plasmonic sensing. Additionally, to demonstrate the universality of the plasmon-regulated FRET sensing strategy, another plasmon-emitter hybrid nano-sensor of Au nano-prism-quantum dots (Au NP-QDs) were constructed and applied for detecting a myocardial infarction biomarker of cardiac troponin I. It was first reported that the change of absorption spectra of plasmonic structure in a plasmon-emitter hybrid nanostructure was employed for analytes detection. The plasmon-regulated FRET sensing strategy described herein has potential utility to develop general sensing platforms for chemical and biological analysis.

Copper(II) complex as a turn on fluorescent sensing platform for acetylcholinesterase activity with high sensitivity

Acetylcholinesterase (AChE) is an important enzyme associated with many nervous diseases, demonstrating the great need for smarter sensing platform with improved sensitivity, selectivity and simplified operation. A "turn on" fluorometric assay is described herein for AChE activity detection, according to the specific enzyme catalyzed reaction of acetylcholine (ATCh) by AChE, which generates thiocholine (TCh) as the product. The well-designed fluorescent probe HBTP possesses ESIPT (Excited State Intramolecular Proton Transfer) nature, leading to a larger Stokes shift, which could be quenched upon coordination with Cu²⁺. The fluorescence-silent HBTP-Cu²⁺ complex could be broken by TCh generated from reaction of ATCh with AChE, giving rise to HBTP release which originates from competitive coordination of TCh with Cu²⁺. This complex probe HBTP-Cu²⁺ offers a limit detection as low as 0.02 mU mL^-1, which is lower than most reported literatures. Furthermore, both HBTP-Cu²⁺ and HBTP show little toxicity to live cells and is available in visualizing cellular AChE activity.

Applications of Nanotechnology in Plant Growth and Crop Protection: A Review

In the era of climate change, global agricultural systems are facing numerous, unprecedented challenges. In order to achieve food security, advanced nano-engineering is a handy tool for boosting crop production and assuring sustainability. Nanotechnology helps to improve agricultural production by increasing the efficiency of inputs and minimizing relevant losses. Nanomaterials offer a wider specific surface area to fertilizers and pesticides. In addition, nanomaterials as unique carriers of agrochemicals facilitate the site-targeted controlled delivery of nutrients with increased crop protection. Due to their direct and intended applications in the precise management and control of inputs (fertilizers, pesticides, herbicides), nanotools, such as nanobiosensors, support the development of high-tech agricultural farms. The integration of biology and nanotechnology into nonosensors has greatly increased their potential to sense and identify the environmental conditions or impairments. In this review, we summarize recent attempts at innovative uses of nanotechnologies in agriculture that may help to meet the rising demand for food and environmental sustainability.

Applications of Nanotechnology in Plant Growth and Crop Protection: A Review

In the era of climate change, global agricultural systems are facing numerous, unprecedented challenges. In order to achieve food security, advanced nano-engineering is a handy tool for boosting crop production and assuring sustainability. Nanotechnology helps to improve agricultural production by increasing the efficiency of inputs and minimizing relevant losses. Nanomaterials offer a wider specific surface area to fertilizers and pesticides. In addition, nanomaterials as unique carriers of agrochemicals facilitate the site-targeted controlled delivery of nutrients with increased crop protection. Due to their direct and intended applications in the precise management and control of inputs (fertilizers, pesticides, herbicides), nanotools, such as nanobiosensors, support the development of high-tech agricultural farms. The integration of biology and nanotechnology into nonosensors has greatly increased their potential to sense and identify the environmental conditions or impairments. In this review, we summarize recent attempts at innovative uses of nanotechnologies in agriculture that may help to meet the rising demand for food and environmental sustainability.

A dual (colorimetric and fluorometric) detection scheme for glutathione and silver (I) based on the oxidase mimicking activity of MnO2 nanosheets

A fluorimetric and colorimetric method is described for the determination of glutathione (GSH) and silver (I). It is based on the use of MnO₂ nanosheets that were prepared by solution mixing and exfoliation. They display oxidase-mimicking activity and can catalyze the oxidation of o-phenylenediamine (OPD) to form yellow 2,3-diaminophenazine (DAP) with an absorption maximum at 410 nm. DAP also has a yellow fluorescence (with a peak at 560 nm). The MnO₂ nanosheets can be rapidly reduced to Mn²⁺ by GSH. This reduces the efficiency of the oxidase mimic MnO₂ and causes a decrease in fluorescence and absorbance intensity. However, on addition of Ag⁺, a complex is formed with GSH. It prevents the destruction of MnO₂ nanosheets so that the enzyme mimicking activity is retained. A dual-method for the determination of GSH and Ag(I) was developed. It has excellent sensitivity for GSH with lower detection limits of 62 nM (fluorimetric) and 0.94 μM (colorimetric). The respective data for Ag(I) are 70 nM and 1.15 μM. The assay was successfully applied to the determination of GSH and Ag(I) in spiked serum samples. Graphical abstract Schematic presentation of a method for colorimetric and fluorometric determination of glutathione (GSH) and silver(I). MnO₂ nanosheets are reduced to Mn(II) by GSH. This reduces the enzyme-mimicking activity of MnO₂ nanosheets and causes a decrease in fluorescence and absorbance. On addition of Ag(I), the enzyme-like activity is increasingly retained. A decrease in fluorescence and absorbance is not observed any longer.

A novel label-free terbium(iii)-aptamer based aptasensor for ultrasensitive and highly specific detection of acute lymphoma leukemia cells

Acute leukemia is a malignant clonal disease of hematopoietic stem cells with a high prevalence and mortality rate. However, there are no efficient tools to facilitate early diagnosis and treatment of leukemia. Therefore, development of new methods for the early diagnosis and prevention of leukemia, especially non-invasive diagnosis at the cellular level, is imperative. Here, a label-free signal-on fluorescence aptasensor based on terbium(iii)-aptamer (Tb³⁺-apt) was applied for the detection of leukemia. The aptamer sensitizes the fluorescence of Tb³⁺ and forms the strong fluorescent Tb³⁺-apt probe. The target cells, the T-cell acute lymphoblastic leukemia cell line (CCRF-CEM) combined with the Tb³⁺-apt probe to form the Tb³⁺-apt-CEM complex, were removed by centrifugation, and the supernatant containing a small amount of the Tb³⁺-apt probe was detected using a fluorescence spectrophotometer. The logarithm of cell concentration showed a good linear relationship (R² = 0.9881) with the fluorescence signal. The linear range for CCRF-CEM detection was 5-5 × 10⁶ cells per ml, while the detection limit was 5 cells per ml of the binding buffer. Clinical samples were collected from 100 cases, and the specificity and positive rates detected by this method were up to 94% and 90%, respectively. Therefore, a single-stranded DNA-sensitized terbium(iii) luminescence method diagnostic was developed which is rapid, sensitive, and economical and can be used for diagnosis of various types of leukemia at the early stage.

A critical comparison of lanthanide based upconversion nanoparticles to fluorescent proteins, semiconductor quantum dots, and carbon dots for use in optical sensing and imaging

The right choice of a fluorescent probe is essential for successful luminescence imaging and sensing and especially concerning in vivo and in vitro applications, the development of new classes have gained more and more attention in the last years. One of the most promising class are upconversion nanoparticles (UCNPs)-inorganic nanocrystals capable to convert near-infrared light in high energy radiation. In this review we will compare UCNPs with other fluorescent probes in terms of (a) the optical properties of the probes, such as their brightness, photostability and excitation wavelength; (b) their chemical properties such as the dispersibility, stability under experimental or physiological conditions, availability of chemical modification strategies for labelling; and (c) the potential toxicity and biocompatibility of the probe. Thereby we want to provide a better understanding of the advantages and drawbacks of UCNPs and address future challenges in the design of the nanocrystals.

Quantitative zeptomolar imaging of miRNA cancer markers with nanoparticle assemblies

Multiplexed detection of small noncoding RNAs responsible for posttranscriptional regulation of gene expression, known as miRNAs, is essential for understanding and controlling cell development. However, the lifetimes of miRNAs are short and their concentrations are low, which inhibits the development of miRNA-based methods, diagnostics, and treatment of many diseases. Here we show that DNA-bridged assemblies of gold nanorods with upconverting nanoparticles can simultaneously quantify two miRNA cancer markers, namely miR-21 and miR-200b. Energy upconversion in nanoparticles affords efficient excitation of fluorescent dyes via energy transfer in the superstructures with core-satellite geometry where gold nanorods are surrounded by upconverting nanoparticles. Spectral separation of the excitation beam and dye emission wavelengths enables drastic reduction of signal-to-noise ratio and the limit of detection to 3.2 zmol/ng_RNA (0.11 amol or 6.5 × 10⁴ copies) and 10.3 zmol/ng_RNA (0.34 amol or 2.1 × 10⁵ copies) for miR-21 and miR-200b, respectively. Zeptomolar sensitivity and analytical linearity with respect to miRNA concentration affords multiplexed detection and imaging of these markers, both in living cells and in vivo assays. These findings create a pathway for the creation of an miRNA toolbox for quantitative epigenetics and digital personalized medicine.