A water-soluble peptide fluorescent chemosensor for detection of cadmium (II) and copper (II) by two different response modes and its application in living LNcap cells

Electrochemical Nanopipette Sensor for In Vitro/In Vivo Detection of Cu2+ Ions

In vitro/in vivo detection of copper ions is a challenging task but one which is important in the development of new approaches to the diagnosis and treatment of cancer and hereditary diseases such as Alzheimer's, Wilson's, etc. In this paper, we present a nanopipette sensor capable of measuring Cu2+ ions with a linear range from 0.1 to 10 μM in vitro and in vivo. Using the gold-modified nanopipette sensor with a copper chelating ligand, we evaluated the accumulation ability of the liposomal form of an anticancer Cu-containing complex at three levels of biological organization. First, we detected Cu2+ ions in a single cell model of human breast adenocarcinoma MCF-7 and in murine melanoma B16 cells. The insertion of the nanoelectrode did not result in leakage of the cell membrane. We then evaluated the distribution of the Cu-complex in MCF-7 tumor spheroids and found that the diffusion-limited accumulation was a function of the depth, typical for 3D culture. Finally, we demonstrated the use of the sensor for Cu2+ ion detection in the brain of an APP/PS1 transgenic mouse model of Alzheimer's disease and tumor-bearing mice in response to injection (2 mg kg-1) of the liposomal form of the anticancer Cu-containing complex. Enhanced stability and selectivity, as well as distinct copper oxidation peaks, confirmed that the developed sensor is a promising tool for testing various types of biological systems. In summary, this research has demonstrated a minimally invasive electrochemical technique with high temporal resolution that can be used for the study of metabolism of copper or copper-based drugs in vitro and in vivo.

Sensitive detection of cadmium ions based on a quantum-dot-mediated fluorescent visualization sensor

A sensitive ratiometric fluorescent sensor for detecting cadmium ions (Cd2+) was constructed based on carbon quantum dots (CQDs)/CdTe quantum dots (CdTe QDs). Red fluorescence (from CdTe QDs) played the role of the signal response and blue fluorescence (from CQDs) served as a reference probe without a color change. The fluorescent sensor showed high selectivity and sensitivity to Cd2+ with a limit of detection (LOD) of 0.018 μM and a range from 0.1 μM to 23 μM. The proposed method was successfully applied to the determination of Cd2+ in real rice samples. In addition, a fluorescent sensor integrated with a smartphone platform was further designed for the visualized and quantitative detection of Cd2+. This work might extend the range of visualization analysis strategies and provide new insights into the rapid quantitative, portable and sensitive detection of Cd2+ in real-time and on-site applications.

Highly catalytic nanoenzyme of covalent organic framework loaded starch- surface-enhanced Raman scattering/absorption bi-mode peptide as biosensor for ultratrace determination of cadmium

High affinity peptides (PTs) have been used in nanoanalysis, but there are no reports which combine PTs with a liquid crystal (LC) covalent organic framework (COF) supported soluble starch (SS) catalytic amplification system as a biosensor recognition element. In this study, a new, highly sensitive and selective bi-mode molecular biosensor has been developed for the determination of cadmium ion (Cd²⁺). Specifically, a highly catalytic and stable COF supported SS nanosol catalyst was fabricated such that a nanocatalytic indicator reaction system for HAuCl₄-sodium formate was established based on surface-enhanced Raman scattering (SERS). The Au nanoparticles produced exhibited a surface plasmon resonance (SPR) absorption peak at 535 nm and a SERS peak at 1,615 cm^-1. Combining the nanocatalytic amplification indicator system with the specific PTs reaction permitted a sensitive and selective SERS/absorption bi-mode platform to be developed for the determination of cadmium in rice. The linear range for SERS determination was 0.025-0.95 nmol/L and the detection limit (DL) was 0.012 nmol/L.

Progress in the Development of Biosensors Based on Peptide-Copper Coordination Interaction

Copper ions, as the active centers of natural enzymes, play an important role in many physiological processes. Copper ion-based catalysts which mimic the activity of enzymes have been widely used in the field of industrial catalysis and sensing devices. As an important class of small biological molecules, peptides have the advantages of easy synthesis, excellent biocompatibility, low toxicity, and good water solubility. The peptide-copper complexes exhibit the characteristics of low molecular weight, high tenability, and unique catalytic and photophysical properties. Biosensors with peptide-copper complexes as the signal probes have promising application prospects in environmental monitoring and biomedical analysis and diagnosis. In this review, we discussed the design and application of fluorescent, colorimetric and electrochemical biosensors based on the peptide-copper coordination interaction.

Recent progress in cadmium fluorescent and colorimetric probes

Cadmium is a heavy metal which exists widely in industrial and agricultural production and can induce a variety of diseases in organisms. Therefore, its detection is of great significance in the fields of biology, environment and medicine. Fluorescent probe has been a powerful tool for cadmium detection because of its convenience, sensitivity, and bioimaging capability. In this paper, we reviewed 98 literatures on cadmium fluorescent sensors reported from 2017 to 2021, classified them according to different fluorophores, elaborated the probe design, application characteristics and recognition mode, summarized and prospected the development of cadmium fluorescent and colorimetric probes. We hope to provide some help for researchers to design cadmium fluorescent probes with higher selectivity, sensitivity and practicability.

Cadmium is a heavy metal which exists widely in industrial and agricultural production and can induce a variety of diseases in organisms.

A smartphone-integrated ratiometric fluorescence sensor for visual detection of cadmium ions

A novel fluorescence sensing platform was fabricated for visual detection of cadmium ions (Cd²⁺) with excellent stability and portability. In this protocol, dual-emission ratiometric fluorescence probe were constructed based on silicon oxide-coated copper nanoclusters (CuNCs@SiO₂) as a signal reference and cadmium telluride quantum dots (CdTe QDs) as signal response, thereby greatly improving the accuracy of test results. The level of Cd²⁺ can be reported within a wide linear range from 0.010 mg·L^-1 to 2.0 mg·L^-1 with a sensitive detection limit of 1.1 μg·L^-1 (2.75 μg·kg^-1) and a quick sample-to-answer monitoring time of 6 min, which was quite qualified for regularly monitoring Cd²⁺. Moreover, aiming to attain portable analysis, the smartphone as colorimetric reader and analyzer were also utilized for rapidly analyzing Cd²⁺ by capturing the change in fluorescence color. Additionally, benefiting from the strong combination of 1, 10-phenanthroline (Phen) and Cd²⁺, the fluorescence probe showed excellent anti-interference activities for Cd²⁺ assay in complex oyster matrix. Overall, the sensing platform had significant stability, specificity and sensitivity, offering a promising potential for conveniently evaluating the quality of marine bivalves polluted with Cd²⁺.

Preparation of a new fluorescence nanochemosensor for Sn(II) ions by a modified nanoprecipitation method

A new dialdehyde was designed and synthesized containing naphthalene groups, and then its macrocycle was prepared with 1,4-diaminobuthan. A modified nanoprecipitation method has been reported for the preparation of the nanoparticles. In this method, to obtain nanoparticles with small particle sizes, the nucleation rate was increased with decreasing of the mixing time. The organic nanoparticles were used for turn-off fluorescence response of low concentration of Sn²⁺ ions over cations such as Cs⁺, K⁺, Na⁺, Ba²⁺, Ca²⁺, Mg²⁺, Al³⁺, Pb^2+, Zn²⁺, Cu²⁺, Ni²⁺, Co²⁺, Fe²⁺, Mn²⁺, Ag⁺, Cd²⁺, and Hg²⁺ and ions in aqueous buffer solution. The limit of detection was 5.4 nM.

Graphdiyne nanosheets as a platform for accurate copper(ii) ion detection via click chemistry and fluorescence resonance energy transfer

A novel sensing platform for sensitive detection of copper(ii) ions (Cu²⁺) in living cells and body fluids was developed by taking advantage of the excellent fluorescence quenching ability of graphdiyne (GDY) and the high specificity of click chemistry for the first time.

Cu²⁺ detection was performed by taking advantage of the fluorescence quenching ability of graphdiyne and the high specificity of click chemistry.

A simple fluorescent probe for detection of Ag+ and Cd2+ and its Cd2+ complex for sequential recognition of S2

In this study, we designed and synthesized a simple probe 2-(8-((8-methoxyquinolin-2-yl)methoxy)quinolin-2-yl)benzo[d]thiazole (DQT) for detection of Ag⁺ and Cd²⁺ in a CH₃OH/HEPES (9 : 1 v/v, pH = 7.30) buffer system. Its structure was characterized by NMR, ESI-HR-MS and DFT calculations, and its fluorescence performance was also investigated. Probe DQT showed fluorescence quenching in response to Ag⁺ and Cd²⁺ with low detection limits of 0.42 μM and 0.26 μM, respectively. Importantly, the complexation of the probe with Cd²⁺ resulted in a red shift from blue to green, making it possible to detect Ag⁺ and Cd²⁺ by the naked eye under an ultraviolet lamp. The DQT-Cd²⁺ complex could be used for sequential recognition of S^2-. The recovery response could be repeated 3 times by alternate addition of Cd²⁺ and S^2-. A filter paper strip test further demonstrated the potential of probe DQT as a convenient and rapid assay.