A colorimetric indicator-displacement assay based on stable Cu2+ selective carbon dots for fluorescence turn-on detection of pyrophosphate anions in urine

Advancements in Nanomedicine for the Diagnosis and Treatment of Kidney Stones

Kidney stones constitute a common condition impacting the urinary system. In clinical diagnosis and management, traditional surgical interventions and pharmacological treatments are primarily utilized; however, these methods possess inherent limitations. Presently, the field of nanomedicine is undergoing significant advancements. The application of nanomaterials in biosensors enables the accurate assessment of urinary ion composition. Furthermore, contrast agents developed from these materials can improve the signal-to-noise ratio and enhance image clarity. By mitigating oxidative stress-induced cellular damage, nanomaterials can inhibit the formation of kidney stones and enhance the efficacy of drug delivery as effective carriers. Additionally, by modifying the physical and chemical properties of bacteria, nanomaterials can effectively eliminate bacterial presence, thereby preventing severe complications. This review explores the advancements in nanomaterials technology related to the early detection of risk factors, clinical diagnosis, and treatment of kidney stones and their associated complications.

A pH switchable hydrophilic fluorescent BODIPY sodium disulfonate for Fe3+ multicolor detection: Experimental and DFT studies

BODIPY-based chemosensors are widely used owing to merits like good selectivity, high fluorescence quantum yield, and excellent optical stability. As such, a pH-switchable hydrophilic fluorescent probe, BODIPY-PY-(SO3Na)2, was developed for detection of Fe3+ ion in aqueous solutions. BODIPY-PY-(SO3Na)2 revealed strong fluorescence intensity and was responsive to pH value in the range of 6.59-1.96. Additionally, BODIPY-PY-(SO3Na)2 showed good selectivity and sensitivity towards Fe3+. A good linear relationship for Fe3+ detection was obtained from 0.0 μM to 50.0 μM with low detecting limit of 6.34 nM at pH 6.59 and 2.36 nM at pH 4.32, respectively. The response to pH and detection of Fe3+ induced obvious multicolor changes. BODIPY-PY-(SO3Na)2 can also be utilized to quantitatively detect Fe3+ in real water sample. Different mechanisms of Fe3+ detection at investigated pH values were unraveled through relativistic density functional theory (DFT) calculations in BODIPY-PY-(SO3Na)2 and experiments of coexisting cations, anions and molecules. These results enabled us to gain a deeper understanding of the interactions between BODIPY-PY-(SO3Na)2 and Fe3+ and provide valuable fundamental information for design of efficient multicolor chemosensors for Fe3+ as well.

Simple, sensitive, colorimetric detection of pyrophosphate via the analyte-triggered decomposition of metal-organic frameworks regulating their adaptive multi-color Tyndall effect

This paper describes initially the application of the Tyndall effect (TE) of metal-organic framework (MOF) materials as a colorimetric signaling strategy for the sensitive detection of pyrophosphate ion (PPi). The used MOF NH2-MIL-101(Fe) was prepared with Fe3+ ions and fluorescent ligands of 2-amino terephthalic acid (NH2-BDC). The fluorescence of NH2-BDC in MOF is quenched due to the ligand-to-metal charge transfer effect, while the NH2-MIL-101(Fe) suspension shows a strong TE. In the presence of PPi analyte, the MOFs will undergo decomposition because of the competitive binding of Fe3+ by PPi over NH2-BDC, resulting in a significant decrease in the TE signal and fluorescence restoration from the released ligands. The results demonstrate that the new method only requires a laser pointer pen (for TE creation) and a smartphone (for portable quantitative readout) to detect PPi in a linear concentration range of 1.25-800 μM, with a detection limit of ~210 nM (3σ) which is ~38 times lower than that obtained from traditional fluorescence with a spectrophotometer (linear concentration range, 50-800 µM; detection limit, 8.15 µM). Moreover, the acceptable recovery of PPi in several real samples (i.e., pond water, black tea, and human serum and urine) ranges from 97.66 to 119.15%.

Metal-free auxiliary pyrophosphate detection based on near-infrared carbon dots

The excessive use of pyrophosphate (PPi) anions as additives poses a serious threat to human health and the environment. Considering the current status of PPi probes, the development of metal-free auxiliary PPi probes has important applications. In this study, a novel near-infrared nitrogen and sulfur co-doped carbon dots (N,S-CDs) were prepared. The average particle size of N,S-CDs was 2.25 ± 0.32 nm with average height was 3.05 nm. The probe N,S-CDs showed a special response to PPi, and a good linear relationship was obtained with PPi concentrations ranging from 0 to 1 μM, with the limit of detection being 0.22 nM. Tap water and milk were used for practical inspection, and ideal experimental results were acquired. In addition, the probe N,S-CDs also showed good results in biological systems, such as cell and zebrafish experiments.

Serotonin-Derived Fluorophore: A Novel Fluorescent Biomaterial for Copper Detection in Urine

We took advantage of the fluorescent features of a serotonin-derived fluorophore to develop a simple and low-cost assay for copper in urine. The quenching-based fluorescence assay linearly responds within the concentration range of clinical interest in buffer and in artificial urine, showing very good reproducibility (CV_av% = 4% and 3%) and low detection limits (16 ± 1 μg L^-1 and 23 ± 1 μg L^-1). The Cu²⁺ content was also estimated in human urine samples, showing excellent analytical performances (CV_av% = 1%), with a limit of detection of 59 ± 3 μg L^-1 and a limit of quantification of 97 ± 11 μg L^-1, which are below the reference value for a pathological Cu²⁺ concentration. The assay was successfully validated through mass spectrometry measurements. To the best of our knowledge, this is the first example of copper ion detection exploiting the fluorescence quenching of a biopolymer, offering a potential diagnostic tool for copper-dependent diseases.

Synthesis of blue fluorescent molybdenum nanoclusters with novel terephthaldehyde-cysteine Schiff base for detection of pyrophosphate

In this work, terephthaldehyde-cysteine-molybdenum nanoclusters (TPA-Cys-MoNCs) were synthesized by using terephthaldehyde-cysteine (TPA-Cys) Schiff base as a novel ligand. The as-synthesized TPA-Cys-MoNCs showed blue fluorescence under UV lamp at 365 nm, displaying emission peak at 455 nm when excited at 340 nm. The fluorescent TPA-Cys-MoNCs are used as a probe for sensitive assay of pyrophosphate (PPi) via fluorescence quenching mechanism. The emission peak intensity of TPA-Cys-MoNCs at 455 nm exhibited a linear quenching with increasing amount of PPi. As a result, quantitative assay was developed for the detection of PPi (0.01-200 µM) with the detection limit of 0.9 nM. The developed probe was successfully demonstrated for the detection of PPi in biofluids (urine and plasma).

Real time sensor for Fe3+, Al3+, Cu2+ & PPi through quadruple mechanistic pathways using a novel dipodal quinoline-based molecular probe

A quinoline-based small molecular probe, H₂L was designed, synthesized and characterized by different spectroscopic methods. It was utilized as a multi-responsive probe for the detection of Fe³⁺, Al³⁺, Cu²⁺ and PPi. It showed very selective instant turn-on fluorimetric response towards Fe³⁺and Al³⁺ with a detection limit in nanomolar range. Solutions of H₂L containing Fe³⁺ or Al³⁺ could sequentially sense PPi by a turn-off mechanism. Also, H₂L could determine the presence of Cu²⁺ very selectively among a series of other metal ions by a sharp change in colour. Detection of Cu²⁺ through colorimetry was further investigated by systematic UV-Vis studies and the potential of H₂L to act as a potential colorimetric sensor for Cu²⁺ was suitably established. Filter-paper strip experiments were conducted to demonstrate the practical utility of the proposed sensor. Potential applications of H₂L as a sensor for pH in the acidic range has also been explored.

Fluorescence "off-on" probe for lead (II) detection based on Atractylodes III CQDs and bioimaging

In this work, a type of carbon quantum dots (CQDs) with bright blue emission were readily fabricated through one-step hydrothermal treatment from Atractylodes III. We explored the surface morphology and optical properties of CQDs by Transmission electron microscope (TEM), X-ray diffraction patterns (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR) and UV-vis spectrophotometer. The obtained CQDs possessed good photoluminescence properties, water solubility and biocompatibility. The fluorescence quantum yield of them was 3.72%. It was found that the fluorescence intensity of CQDs will be quenched by picric acid (PA). After adding lead (II), the fluorescence can be effectively recovered. Hence, an "off-on" fluorescence probe was designed to detect lead (II) in the range of 0-580 μM and the limit of detection (LOD) was 0.068 μM. In the meanwhile, the experiments showed that the CQDs can be successfully used in bioimaging and as a hidden fluorescent ink.

Copper (II) Ion-Modified Gold Nanoclusters as Peroxidase Mimetics for the Colorimetric Detection of Pyrophosphate

Copper (II) ions have been shown to greatly improve the chemical stability and peroxidase-like activity of gold nanoclusters (AuNCs). Since the affinity between Cu²⁺ and pyrophosphate (PPi) is higher than that between Cu²⁺ and AuNCs, the catalytic activity of AuNCs-Cu²⁺ decreases with the introduction of PPi. Based on this principle, a new colorimetric detection method of PPi with high sensitivity and selectivity was developed by using AuNCs-Cu²⁺ as a probe. Under optimized conditions, the detection limit of PPi was 0.49 nM with a linear range of 0.51 to 30,000 nM. The sensitivity of the method was three orders of magnitude higher than that of a fluorescence method using AuNCs-Cu²⁺ as the probe. Finally, the AuNCs-Cu²⁺ system was successfully applied to directly determine the concentration of PPi in human urine samples.