Zi-Han Chen

Dual lanthanide-doped complexes: the development of a time-resolved ratiometric fluorescent probe for anthrax biomarker and a paper-based visual sensor

In this work, a novel time-resolved ratiometric fluorescent probe based on dual lanthanide (Tb: terbium, and Eu: europium)-doped complexes (Tb/DPA@SiO2-Eu/GMP) has been designed for detecting anthrax biomarker (dipicolinic acid, DPA), a unique and major component of anthrax spores. In such complexes-based probe, Tb/DPA@SiO2 can serve as a stable reference signal with green fluorescence and Eu/GMP act as a sensitive response signal with red fluorescence for ratiometric fluorescent sensing DPA. Additionally, the probe exhibits long fluorescence lifetime, which can significantly reduce the autofluorescence interferences from biological samples by using time-resolved fluorescence measurement. More significantly, a paper-based visual sensor for DPA has been devised by using filter paper embedded with Tb/DPA@SiO2-Eu/GMP, and we have proved its utility for fluorescent detection of DPA, in which only a handheld UV lamp is used. In the presence of DPA, the paper-based visual sensor, illuminated by a handheld UV lamp, would result in an obvious fluorescence color change from green to red, which can be easily observed with naked eyes. The paper-based visual sensor is stable, portable, disposable, cost-effective and easy-to-use. The feasibility of using a smartphone with easy-to-access color-scanning APP as the detection platform for quantitative scanometric assays has been also demonstrated by coupled with our proposed paper-based visual sensor. This work unveils an effective method for accurate, sensitive and selective monitoring anthrax biomarker with backgroud-free and self-calibrating properties.

GelRed/[G3T]5/Tb3+ hybrid: A novel label-free ratiometric fluorescent probe for H2O2 and oxidase-based visual biosensing

A novel label-free ratiometric fluorescent probe is developed for the detection of H2O2 based on GelRed/[G3T]5/Tb3+ hybrid, in which GelRed (a nucleic acid dye) intercalated into the designed single-stranded DNA [G3T]5 (i.e. GelRed/[G3T]5) acts as a stable build-in reference with red emission and Tb3+ sensitized by [G3T]5 (i.e. [G3T]5/Tb3+) as a sensitive response signal with green fluorescence. With the successive addition of Hg2+ and cysteine (Cys) to GelRed/[G3T]5/Tb3+, the fluorescence of [G3T]5/Tb3+ can be effectively quenched and recovered respectively, while the fluorescence of GelRed/[G3T]5 remains unchangeable. Combined with these properties, we have demonstrated its application for label-free ratiometric fluorescence detection of H2O2 with self-calibration. The sensing mechanism is based on the specific reaction between H2O2 and Cys, the resulting disulfide reverses the Cys-mediated fluorescence changes of [G3T]5/Tb3+. This method is further applied to the monitoring of oxidase-related reactions. As the glucose oxidase (GOx)-biocatalyzed oxidation of glucose and the acetylcholine esterase/choline oxidase (AChE/ChOx) cascade yield H2O2, such two biocatalytic processes are successfully examined utilized our proposed method, indicating its potential broad applications in biomedical analysis. In addition, we have also demonstrated its feasibility for oxidase-based visual biosensing, in which only a handheld UV lamp is used. Importantly, coupled with our proposed visual biosensing, a realtime quantitative scanometric assays has been also demonstrated by using a smartphone with easy-to-access color-scanning APP as the detection platform. Compared to traditional methods, the proposed design is cost-effective, simple to prepare and easy-to-use without fluorescence labeling or chemical modification.

Bioinspired Copolymers Based Nose/Tongue-Mimic Chemosensor for Label-Free Fluorescent Pattern Discrimination of Metal Ions in Biofluids

There is a close correlation between body health and the level of biofluid-derived metal ions, which makes it an attractive model analyte for noninvasive health monitoring. The present work has developed a novel nose/tongue-mimic chemosensor array based on bioinspired polydopamine/polyethylenimine copolymers (PDA/PEI n) for label-free fluorescent determination of metal ions in biofluids. Three types of PDA/PEI n (PDA/PEI6, PDA/PEI18, and PDA/PEI48) were prepared by using different concentrations of PEI to construct the proposed sensor array, which would lead to unique fluorescence response patterns upon challenged with metal ions for their pattern discrimination. The results show that as few as 3 PDA/PEI n sensors can successfully realize the largescale sensitive detection of metal ions in biofluids. Moreover, we have demonstrated that PDA/PEI n sensors are qualified for lifetime-based pattern discrimination application. Furthermore, the sensors can distinguish between different concentrations of metal ions, as well as a mixture of different metal ions in biofluids, even the mixtures with different valence states. The method promises the simple, rapid, sensitive, and powerful discrimination of metal ions in accessible biofluids, showing the potential applications in the diagnosis of metal ion-involved diseases.

pH-Regulated Optical Performances in Organic/Inorganic Hybrid: A Dual-Mode Sensor Array for Pattern Recognition-Based Biosensing

Dual-mode optical assays are becoming more popular and attractive because they would provide robust detailed information in biochemical analysis. We herein unveil a novel dual-mode optical (i.e., UV-vis absorption and fluorescence) method for multifunctional sensing of phosphate compounds (PCs) (e.g., nucleotides and pyrophosphate) based on pattern recognition, which innovatively employs only one kind of porphyrin/lanthanide-doped upconversion nanoparticles (Ln-UCNPs) hybrid integrated with a facile pH-regulated strategy as the sensor array. An easy-to-obtain porphyrin hydrate (tetraphenylporphyrin tetrasulfonic acid hydrate, TPPS) can assemble onto the ligand-free Ln-UCNPs to construct the organic/inorganic hybrid (TPPS/Ln-UCNPs), leading to a new absorption band to quench the upconversion fluorescence of Ln-UCNPs due to fluorescence resonance energy transfer (FRET). The dual-mode optical performances of TPPS/Ln-UCNPs are characteristically correlated with the pH in aqueous solution. Thus, as a proof-of-concept design, three types of TPPS/Ln-UCNPs (TPPS/Ln-UCNPs4, TPPS/Ln-UCNPs4.5, and TPPS/Ln-UCNPs5) were prepared by using buffers with different pH (at 4, 4.5, and 5) to form our proposed sensor array, which would result in individual dual-mode optical response patterns upon being challenged with PCs for their pattern recognition through a competitive mechanism between TPPS and PCs. The results show that three TPPS/Ln-UCNPs n sensors can successfully permit the sensitive detection of 14 PCs and differentiate them between different concentrations, as well as a mixture of them. The pH-dependent TPPS/Ln-UCNPs promises the simple, yet powerful discrimination of PCs via pattern recognition, would prospectively stimulate and expand the use of organic/inorganic hybrid toward more biosensing applications.

Label-free non-invasive fluorescent pattern discrimination of thiols and chiral recognition of cysteine enantiomers in biofluids using bioinspired copolymers-Cu2+ hybrid sensor array regulated by pH

Thiols play a crucial role in various biological processes, and the discrimination of thiols in biofluids is a significant but difficult issue. Herein, a facile label-free non-invasive fluorescent sensor array has been presented based on PDA/PEIn-Cu2+ in three different pH buffer solutions for pattern discrimination of thiols and chiral recognition of cysteine (Cys) enantiomers in biofluids toward health monitoring. The proposed sensor array was fabricated based on the fact that Cu2+ has a strong affinity toward thiols, which prevents Cu2+ from binding PDA/PEIn, and the fluorescence properties of PDA/PEIn were recovered to a certain degree. Different thiols exhibited different affinities toward Cu2+, generating distinct fluorescence response patterns. These response patterns are characteristic for each thiol and can be discriminated by principal component analysis (PCA). In this work, three types of PDA/PEI48-Cu2+ sensors (PDA/PEI48-Cu4 2+, PDA/PEI48-Cu4.5 2+ and PDA/PEI48-Cu5 2+) were prepared by using acetate buffer with different pHs (at 4, 4.5, and 5) to form our proposed sensor array, which could realize the pattern discrimination of 8 thiols. Moreover, we successfully realized the sensitivity and selectivity assays to these thiols. Furthermore, the proposed sensor array could discriminate mixtures of thiols as well as the chiral recognition of mixtures of Cys enantiomers, promising its potential practical usage. Significantly, the resultant practical application in real samples showed that it could be a fascinating assay for the development of non-invasive diagnosis. This method promises the facile, sensitive and powerful discrimination of thiols in biofluids and would sprout more relevant strategies toward a broad range of applications.