Construction of Hybrid Fluorescent Sensor for Cu2+ Detection Using Fluorescein-functionalized CdS Quantum Dots Via FRET

CoMnOx Nanoflower-Based Smartphone Sensing Platform and Virtual Reality Display for Colorimetric Detection of Ziram and Cu2

Transition metal doping is an ideal strategy to construct multifunctional and efficient nanozymes for biosensing. In this work, a metal-doped CoMnOx nanozyme was designed and synthesized by hydrothermal reaction and high-temperature calcination. Based on its oxidase activity, an "on-off-on" smartphone sensing platform was established to detect ziram and Cu2+. The obtained flower-shaped CoMnOx could exhibit oxidase-, catalase-, and laccase-like activities. The oxidase activity mechanism of CoMnOx was deeply explored. O2 molecules adsorbed on the surface of CoMnOx were activated to produce a large amount of O2·-, and then, O2·- could extract acidic hydrogen from TMB to produce blue oxTMB. Meanwhile, TMB was oxidized directly to the blue product oxTMB via the high redox ability of Co species. According to the excellent oxidase-like activity of CoMnOx, a versatile colorimetric detection platform for ziram and Cu2+ was successfully constructed. The linear detection ranges for ziram and Cu2+ were 5~280 μM and 80~360 μM, and the detection limits were 1.475 μM and 3.906 μM, respectively. In addition, a portable smartphone platform for ziram and Cu2+ sensing was established for instant analysis, showing great application promise in the detection of real samples including environmental soil and water.

A Novel L-Arginine Functionalized CdTe Quantum Dots Fluorescence Probe for Pyrophosphate Anion Detection

In this paper, a novel amino acid surface-functionalized semiconductor CdTe quantum dot fluorescent probe amidated by carboxyl and amide groups was synthesized to detect pyrophosphate ions (P2O74-, PPi). L-Arginine (L-Arg) was grafted onto cysteine modified CdTe quantum dots (Mea-CdTe QDs) to form a new L-Arginine-functionalized quantum dot fluorescent probe (L-Arg@Mea-CdTe). The prepared probe has good optical properties with multiple grafted functional groups on the surface. The guanidine group of the L-Arg@Mea-CdTe fluorescent probe is strongly basic and will be fully protonated under physiological conditions. The resulting hydrogen bonds bound to pyrophosphate lead to significant changes in the fluorescence of CdTe quantum dots. IR and XPS characterization were performed to confirm it. The addition of PPi induces a significant fluorescence quenching of L-Arg@Mea-CdTe in aqueous solution. The fluorescent QDs probe can also detect pyrophosphate with good sensitivity and anti-interference performance. The detection limit of the L-Arg@Mea-CdTe fluorescence probe for PPi is as low as 0.30 μM. In addition, the novel nano-fluorescent probe was successfully applied to detect PPi in water and in cell imaging.

Enrichment and detection of VEGF165 in blood samples on a microfluidic chip integrated with multifunctional units

In this paper, a multifunctional microfluidic chip integrated with a centrifugal separation zone, aqueous two-phase system (ATPS) mixing zone and enrichment detection zone was proposed and fabricated. An automatic and efficient separation and quantitative analysis method for vascular endothelial growth factor 165 (VEGF₁₆₅) in whole blood samples was established with the designed microfluidic chip. A blood sample was divided into blood cells and plasma in the centrifugation zone. In the ATPS mixing zone, plasma was mixed with PEG/KH₂PO₄ aqueous two-phase solution containing Apt-Au NP nanoprobes. In the enrichment detection zone, the mixture was separated on CN140 modified with a ZnO NP-anti VEGF₁₆₅ nanostructure. The VEGF₁₆₅ captured by Apt-Au NPs was distributed in the PEG phase, concentrated at the front of CN140 and combined with anti-VEGF₁₆₅ to form a sandwich structure. The sensitive detection of VEGF₁₆₅ was achieved through fluorescence resonance energy transfer between rhodamine B and Au NPs on the nanoprobe. Under the optimized rotation program, capillary and centrifugal forces propelled the fluid in the whole process of pretreatment and detection. The detection linear range was between 1 pg mL^-1 and 50 ng mL^-1, the detection limit of VEGF₁₆₅ in blood was 0.22 pg mL^-1 and the enrichment efficiency was 983. It was illustrated that a convenient and reliable way for detection of tumor markers based on the multifunctional microfluidic chip was provided and it has a potential value for early screening and prognosis of clinical cancer.

Multi-layered g-C3N4 as a Fluorescent Probe for Hg2+ Detection

Hg²⁺ is one of the most toxic heavy metal ions that exist in the environment and it forms large numbers of toxic binary compounds. Accurate and rapid detection of the concentration of heavy metal ions is a prerequisite technology to achieve pollution control and prevention. Fluorescent probes have attracted extensive attention because of their high sensitivity, prominent precision, convenient and fast visualization of heavy metals. Herein, we report multi-layered graphitic carbon nitride via a simple thermopolymerization treatment as a very effectual fluorescent probe for sensitive and selective detection of Hg²⁺ with a limit of detection as low as 1.14 nM.