Optical Detection of Copper Ions via Structural Dissociation of Plasmonic Sugar Nanoprobes

A highly-sensitive fluorescent probe for the detection of copper ions and its applications in water quality monitoring, neural cell imaging and plant imaging

High copper levels pose a risk to environmental and human health due to their toxicity and widespread industrial application, in which abnormal copper levels are associated with various diseases both in neurodegenerative diseases and plant growth. Thus, a turn-on fluorescent probe BBYD-Cu, based on donor-acceptor type structure, was designed and synthesized with easy preparations. BBYD-Cu can specifically recognized Cu2+ by 2-picolinic ester group, then released the fluorophore to enhance the fluorescent signals. With a detection limit of 31 nM, it displays extremely sensitive and precise Cu2+ detection. In addition, BBYD-Cu has the advantages of fast response speed (within 3 min), excellent selectivity and strong anti-interference ability for Cu2+. Significantly, the BBYD-Cu demonstrates superior detection and imaging performance even in intricate real-world environmental samples, biological nerve cells and plant soybean sprout root tissue.

Construction of multifunctional hydrogel containing pH-responsive gold nanozyme for bacteria-infected wound healing

Nanozymes have become promising alternative antibacterial agents for bacteria-infected wounds. In this study, fucoidan-confined gold nanoparticles (Fuc@AuNPs) are developed by in situ reduction, and stabilized by sulfate groups of fucoidan. Fuc@AuNPs exhibit pH-responsive catalytic activity that can mimic oxidase (OXD) under acidic bacterial infection conditions and mimic superoxide dismutase (SOD) under normal physiological conditions. The OXD-like catalytic activity of Fuc@AuNPs generates active singlet oxygen (1O2), exhibiting effective antibacterial properties against both Gram-negative E. coli and Gram-positive S. aureus. Fuc@AuNPs and aldehyde grafted saponin incorporate with chitosan to form a hybrid hydrogel. This hydrogel exhibits superior mechanical, adhesive, and self-healing properties due to electrostatic complex coacervation networks and dynamic covalent Schiff base reactions. Animal experiments show that the hydrogel aids S. aureus-infected skin wound healing by reducing bacterial infection and promoting granulation tissue formation without causing excessive ROS-induced inflammation. This study presents the design of multifunctional nanozymes and bioactive hydrogels as a promising wound healing dressing for biomedical applications.

Green Synthesis of Biocompatible Chiral Gold Nanoparticles

Chiral gold nanoparticles (Au NPs) have been investigated widely and have shown great potential in biomedical applications, such as biosensing, combating bacterial infections and tissue regeneration. However, some stabilizers and reducing agents for the synthesis of chiral Au NPs can produce toxicity in living organisms. Therefore, it is interesting to design green methods to prepare chiral gold nanoparticles that are nontoxic, environment-friendly, and low-cost. Herein, novel biocompatible chiral Au NPs with a diameter of 54.4 ± 14.9 nm were prepared by the in situ reduction of HAuCl4 with alginates as the green reducing agent and chiral-inducing and stabilizing agent. XPS, TGA, UV-Vis and CD analyses demonstrated that alginate-stabilized chiral Au NPs (ALG-Au NPs) were successfully prepared, while biocompatibility assessment showed that cell viability was 116.0% when the concentration of ALG-Au NPs arrived at 300 μg/mL, which indicated that ALG-AuNPs showed excellent biocompatibility. Furthermore, the ALG-Au NPs can respond to metal ions, such as Ca2+, Cu2+, Mn2+ and so on, implying potential application for biosensing.

A dual-channel sensing platform for the cross-interference-free detection of tetracycline and copper ion

Tetracycline (TC) and copper ion (Cu2+), as important additives in animal feed, play a crucial role in disease prevention and growth regulation. However, the abuse leads to concentration accumulation, which seriously threatens human health and the ecological environment. There is an urgent need to develop a detection method to achieve fast and synchronous detection of these pollutants without cross-interference. Here, a carbon dots-doped lanthanide-based fluorescent nanosensor (CDs@Tb-MOFs@SiO2-NH2-Eu) was synthesized, which can detect TC in the 380 nm channel by "antenna effect" and internal filtering effects (IFE), and identify Cu2+ in the 320 nm channel. The sensor was highly sensitive to TC within 0-4 μM with a detection limit as low as 3.64 nM, and Cu2+ could be detected within 0-40 μM with a detection limit of 38 nM. A portable dual-channel visual fluorescence sensor was obtained by loading the probes onto test paper and cotton swabs in food samples, which indicates the practicability of this sensing strategy.

Insight into the charge transfer behavior of an electrochemiluminescence sensor based on porphyrin-coumarin derivatives with a donor-acceptor configuration

The excellent photophysical and electrochemical properties of porphyrins have inspired widespread interest in the realm of electrochemiluminescence (ECL). The aggregation-caused deficiency of ECL emission in aqueous solution, however, still severely impedes further applications. Herein, a molecule with a donor-acceptor (D-A) configuration, ATPP-Cou, consisting of monoaminoporphyrin as an electron donor and coumarin as an electron acceptor, was designed as an ECL luminophore to address the susceptibility of the porphyrin to aggregation-caused quenching (ACQ) in aqueous solution. ATPP-Cou demonstrated a three-fold enhanced ECL signal compared to pristine ATPP. Despite the acknowledged significance of intramolecular charge transfer (ICT) in generating excited states in ECL, there is a lack of quantitative descriptions. Herein, intensity-modulated photocurrent spectroscopy (IMPS) and scanning photoelectrochemical microscopy (SPECM) were utilized to validate the influence of ICT on the enhancement performance of D-A type ECL molecules. Additionally, ATPP-Cou was also developed as a probe for the successful detection of Cu2+ in aqueous solution. The present study not only enriches the repertoire of efficient porphyrin-based ECL luminophores applicable in aqueous environments but also exemplifies the successful integration of novel measurement techniques to provide more comprehensive insights into the underlying mechanisms responsible for improved ECL performance.

Sustainable triethylenetetramine modified sulfonated graphene oxide/chitosan composite for enhanced adsorption of Pb(II), Cd(II), and Ni(II) ions

A novel sulfonated group and triethylenetetramine modified GO/chitosan (GO-CS) adsorbent (T-SGO-CS) was successfully prepared and utilized for the adsorption of heavy metal ions from single-metal, binary-metal, and ternary-metal solutions. In a single system, the adsorption capacity was 312.28 mg/g for Pb2+, 260.52 mg/g for Cd2+, and 84.61 mg/g for Ni2+, whereas, Adsorption of Pb(II), Cd(II), and Ni(II) in binary and ternary systems was systematically studied. In tertiary systems, the effect of competitive adsorption was more pronounced. In addition, T-SGO-CS exhibited a high adsorption capacity and was recyclable for Pb2+, Cd2+, and Ni2+. T-SGO-CS is a novel and highly efficient adsorbent for omnidirectionally enhancing the adsorption of Pb2+, Cd2+, and Ni2+, as demonstrated by these results. Therefore, T-SGO-CS could be investigated as a potential new material for future applications in heavy metal removal.

Colorimetric sensor based on biogenic nanomaterials for high sensitive detection of hydrogen peroxide and multi-metals

Hydrogen peroxide (H2O2) and heavy metals, which are among the wastes of the industrial sector, become a threat to living things and the environment above certain concentrations. Therefore, the detection of both H2O2 and heavy metals with simple, low-cost, and fast analytical methods has gained great importance. The use of nanoparticles in colorimetric sensor technology for the detection of these analytes provides great advantages. In recent years, green synthesis of nanomaterials with products that can be considered biowaste is among the popular topics. In this study, silver/silver chloride nanoparticles (Ag@AgCl NPs) were synthesized using the green synthesis method as an eco-friendly and cheap method, the green algae extract was used as a reducing agent. The characterization of Ag@AgCl nanoparticles and green algae extract was carried out with several techniques such as Transmission Electron Microscopy (TEM), UV-Visible spectrometry (UV-Vis), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction patterns (XRD) methods were used for characterization. According to TEM analysis, the Ag@AgCl NPs typically spherical in form and range in size from 4 to 10 nm, and UV-vis showed the formation of surface plasmon resonance (SPR) of the Ag@AgCl between 400 and 450 nm. In addition, its activity as a colorimetric sensor for hydrogen peroxide (H2O2) and multi-metal detection was evaluated. Interestingly, Ag/AgCl NPs caused different color formations for 3 metals simultaneously in the sensor study for heavy metal detection, and Fe3+, Cu2+, and Cr6+ ions were detected. The R2 values for H2O2, Fe3+, Cu2+, and Cr6+ were 0.9360, 0.9961, 0.9787, and 0.9625 the limit of detection (LOD) was 43.75, 1.69, 3.18, and 5.05 ppb (ng/mL), respectively. It was determined that Ag@AgCl NPs have the potential to be used as a colorimetric sensor for the detection of H2O2 and heavy metals from wastewater.

Colorimetric sensing of Cu(II) ions in water on the basis of selective chemical etching of EDA-capped Ag nanoplates

Cu(II) ions are one of the essential mineral elements in the human body, but can pose a substantial health risk to people exposed to high concentrations of Cu(II) ions over a long period. Therefore, the ability to detect Cu(II) ions in drinking water is important. In this study, a novel colorimetric sensing probe for the easy and onsite detection of Cu(II) ions in drinking water was developed. The probe was constructed through selective chemical etching of triangular Ag nanoplates with tunable localized surface plasmon resonance (LSPR) properties. Ethylenediamine (EDA) was used as an organic capping agent to improve the chemical stability of triangular Ag nanoplates. Selective chemical etching of the EDA-capped Ag nanoplates in the presence of Cu(II) ions as a result of the formation of a coordination complex between the EDA and Cu(II) ions caused remarkable changes in the nanoplates' LSPR characteristics. On the basis of this phenomenon, a novel colorimetric sensing probe capable of detecting Cu(II) ions in drinking water at concentrations above the safety limit was developed. Our findings were also extended to develop a portable and paper-based sensing probe with good long-term stability to overcome the shortcomings of liquid-phase colorimetric sensors without requiring a spectrometer. The proposed colorimetric sensing probes provide accurate results even with a real sample and offer numerous advantages over conventional sensing platforms, including clearly distinguishable color changes that can be observed by the naked eye; thus, the proposed probes can be used for the selective, reliable, and low-cost point-of-care detection of Cu(II) ions in water.

A colorimetric and fluorometric dual-mode probe for Cu2+detection based on functionalized silver nanoparticles

A novel colorimetric/fluorescent probe (AgNPs-GSH-Rh6G2) was prepared by linking silver nanoparticles (AgNPs) with rhodamine 6G derivative (Rh6G2) using glutathione (GSH) as a linker molecule. The prepared probe showed obvious fluorescence change and colorimetric response after adding copper ions. Based on this phenomenon, a colorimetric/fluorescence dual-mode detection method was constructed to recognize copper ions. The linear ranges of fluorescence detection and colorimetric detection were 0.10 to 0.45 mM and 0.15 to 0.65 mM, respectively, and the limit of detection were 0.18 μM and 24.90 μΜ. In addition, the dual-mode probe has achieved satisfactory results in the detection of copper ions in sediment samples. The successful construction of AgNPs-GSH-Rh6G2 not only provide a reliable tool for the detection of copper ions, but also shed light on a new idea for the multi-mode development of the detection platform.

Spatiotemporally controlled drug delivery via photothermally driven conformational change of self-integrated plasmonic hybrid nanogels

BACKGROUND

Spatiotemporal regulation is one of the major considerations for developing a controlled and targeted drug delivery system to treat diseases efficiently. Light-responsive plasmonic nanostructures take advantage due to their tunable optical and photothermal properties by changing size, shape, and spatial arrangement.

RESULTS

In this study, self-integrated plasmonic hybrid nanogels (PHNs) are developed for spatiotemporally controllable drug delivery through light-driven conformational change and photothermally-boosted endosomal escape. PHNs are easily synthesized through the simultaneous integration of gold nanoparticles (GNPs), thermo-responsive poly (N-isopropyl acrylamide), and linker molecules during polymerization. Wave-optic simulations reveal that the size of the PHNs and the density of the integrated GNPs are crucial factors in modulating photothermal conversion. Several linkers with varying molecular weights are inserted for the optimal PHNs, and the alginate-linked PHN (A-PHN) achieves more than twofold enhanced heat conversion compared with others. Since light-mediated conformational changes occur transiently, drug delivery is achieved in a spatiotemporally controlled manner. Furthermore, light-induced heat generation from cellular internalized A-PHNs enables pinpoint cytosolic delivery through the endosomal rupture. Finally, the deeper penetration for the enhanced delivery efficiency by A-PHNs is validated using multicellular spheroid.

CONCLUSION

This study offers a strategy for synthesizing light-responsive nanocarriers and an in-depth understanding of light-modulated site-specific drug delivery.

A Highly Sensitive Dual-Signal Strategy via Inner Filter Effect between Tween 20-Gold Nanoparticles and CdSe/ZnS Quantum Dots for Detecting Cu2

A highly sensitive and accurate dual-signal strategy is developed for trace Cu²⁺ detection based on the inner filter effect (IFE) between Tween 20-gold nanoparticles (AuNPs) and CdSe/ZnS quantum dots (QDs). Tween 20-AuNPs are utilized as colorimetric probes and excellent fluorescent absorbers. The fluorescence of CdSe/ZnS QDs can be quenched efficiently by Tween 20-AuNPs via IFE. In the presence of D-penicillamine, D-penicillamine induces the aggregation of Tween 20-AuNPs and the fluorescent recovery of CdSe/ZnS QDs at high ionic strength. Upon addition of Cu²⁺, D-penicillamine tends to selectively chelate with Cu²⁺ and then forms the mixed-valence complexes, which consequently inhibits the aggregation of Tween 20-AuNPs and the fluorescent recovery. The dual-signal method is used to quantitatively detect trace Cu²⁺, with low detection limits of 0.57 μg/L and 0.36 μg/L for colorimetry and fluorescence, respectively. In addition, the proposed method using a portable spectrometer is applied to the detection of Cu²⁺ in water. This sensitive, accurate and miniature sensing system has potential in environmental evaluations.

The fabrication of N-doped carbon dots by methionine and their utility in sensing Cu2+ in real water

Copper ions (Cu²⁺) are ubiquitous in the ecosystem and cause serious environmental pollution, posing a threat to human health. Therefore, sensitive detection of Cu²⁺ is urgently needed. Herein, we employed a solvothermal method to prepare blue-emitting carbon dots (Met-CDs) using formamide (FA) and methionine (Met) as precursors, with a high quantum yield (QY) of 38%. Based on the good optical stability of Met-CDs and selective quenching by Cu²⁺, a sensitive probe using Met-CDs for the detection of Cu²⁺ in water was successfully designed. Within the linear range of 0.15-2 μM, the limit of detection (LOD) was determined to be as low as 47.7 nM, enabling the quantitative detection of Cu²⁺. Moreover, the recovery data of the spiked analysis of lake/river water samples were also satisfactory and verified the feasibility of the probe by the analysis of Cu²⁺ in natural conditions.

Colorimetric detection of Cu2+ based on the inhibition strategy for etching reaction of AgNCs

In this study, an efficient and simple colorimetric method for sensing of Cu²⁺ was established using inhibition effect of Cu²⁺ to the etching reaction of silver nanocubes (AgNCs) induced by H₂O₂. The etching reaction of AgNCs changes its morphology and absorbance with the visual appearance from yellow to colorless. On the contrary, the presence of Cu²⁺ can significantly inhibit the etching progress. Thus Cu²⁺ induces the obvious absorbance enhancement compared with AgNCs/H₂O₂ system. This design realizes colorimetric detection of Cu²⁺ based on the inhibition effect of etching reaction using AgNCs nanoprobe. The colorimetric response of AgNCs nanoprobe in ΔAbs_417.5 shows the linearity with the increasing concentrations of Cu²⁺ from 0.01 to 40 μM with good selectivity. The concentration limit of Cu²⁺ efficaciously discriminated by the naked eye is as low as 0.01 μM. Furthermore, the Euclidean distance (ED) of the difference map in RGB change before and after response with Cu²⁺ is applied for further visualization recognition of Cu²⁺. All the above results indicate the outstanding practicability and accuracy of the proposed assay for Cu²⁺ sensing.

Fabrication of hierarchical β-Bi2O3/AuAg microspheres for sensitive, selective and rapid detection of environment pollutants by surface-enhanced Raman spectroscopy

In this paper, we report a novel surface-enhanced Raman spectroscopy (SERS) substrate based on hierarchical β-Bi2O3/Au2Ag2 microspheres for rapid, sensitive and selective detection of environment pollutants including o-dianisidine (o-diASD) and Hg2+ in environmental samples. The sheet-like β-Bi2O3 not only provides large specific surface areas for adsorption of molecules and AuAg, but also emerges as semiconductor matrix with chemical enhancement combined with AuAg with electromagnetic enhancement, making promising SERS activity. Particularly, the β-Bi2O3/Au2Ag2 shows high SERS performance for 4-mercaptobenzoic acid and TMB with minimum detectable concentration of 0.1 μg/L with enhancement factor of 3.1 × 107 and 6.3 × 107, respectively. The density functional theory simulations were further adopted to explain the high SERS activity and selectivity for o-diASD and TMB. Finally, the β-Bi2O3/Au2Ag2 was applied to direct detection of o-diASD, and indirect detection of Hg2+ by TMB marking in environmental samples. The linearity range of 0.5-200.0 and 0.2-500.0 μg/L with limit of detection of 0.2 and 0.07 μg/L for o-diASD and Hg2+ ions can be achieved, respectively. This method provides a novel strategy in designing and fabricating SERS substrates with high performance for rapid, sensitive and accurate analysis of environmental pollutants.