Alkaline phosphatase-responsive Zn2+ double-triggered nucleotide capped gold nanoclusters/ alginate hydrogel with recyclable nanozyme capability

Phosphatase-mimicking Zr@PDA nanozyme with excellent dispersion stability for the detection of fructose 1,6-diphosphate

Zr4+-doped polydopamine (Zr@PDA) nanozyme with phosphatase-like activity was synthesized by a one-pot hydrothermal method for the first time. Compared with previous representative phosphatase-mimicking nanozymes (i.e., CeO2 NPs, ZrO2 NPs and UiO-66), Zr@PDA not only exhibited higher dispersion stability in water, but also higher catalytical efficiency. Kcat/Km of Zr@PDA is 35 and 12 times that of UiO-66 and ZrO2 NPs, respectively, which would endow the Zr@PDA-based analytical methods with high sensitivity. As a demonstration, a novel colorimetric method based on Zr@PDA nanozyme was developed for sensitive detection of the drug fructose 1,6-diphosphate. The linear range is 1-15 μM with a detection limit as low as 0.38 μM.

Hofmeister Effect Promoted the Introduction of Tunable Large Mesopores in MOFs at Low Temperature for Femtomolar ALP Detection

In addressing the demand for hierarchically mesoporous metal-organic frameworks (HMMOFs) with adjustable large mesopores, a method based on the synergistic effects of low-temperature microemulsions and Hofmeister ions is developed. Low temperature dramatically enhanced the solubility of hydrophobic solvent in the microemulsion core, enlarging the mesopores in HMMOFs replica. Meanwhile, Hofmeister salt-in ions continuously controlled mesopore expansion by modulating the permeability of swelling agent into the microemulsion core. The large mesopores up to 33 nm provided sufficient space for the alkaline phosphatase (ALP) enrichment, and retained the remaining channel to facilitate the free mass diffusion. Leveraging these advantages, a colorimetric sensor is successfully developed using large-mesopore HMMOFs for femtomolar ALP detection based on the enrichment and cycling amplification principles. The sensor exhibited a linear detection range of 100 to 7500 fm and a limit of detection of 42 fm, presenting over 4000 times higher sensitivity than classic para-nitrophenyl phosphate colorimetric methods. Such high sensitivity highlights the importance of adjustable mesoporous structures of HMMOFs in advanced sensing applications, and prefigures their potential for detecting large biomolecules in diagnostics and biomedical research.

Surface modification strategies and the functional mechanisms of gold nanozyme in biosensing and bioassay

Gold nanozymes (GNZs) have been widely used in biosensing and bioassay due to their interesting catalytic activities that enable the substitution of natural enzyme. This review explains different catalytic activities of GNZs that can be achieved by applying different modifications to their surface. The role of Gold nanoparticles (GNPs) in mimicking oxidoreductase, helicase, phosphatase were introduced. Moreover, the effect of surface properties and modifications on each catalytic activity was thoroughly discussed. The application of GNZs in biosensing and bioassay was classified in five categories based on the combination of the enzyme like activities and enhancing/inhibition of the catalytic activities in presence of the target analyte/s that is realized by proper surface modification engineering. These categories include catalytic activity enhancer, reversible catalytic activity inhibitor, binding selectivity enhancer, agglomeration base, and multienzyme like activity, which are explained and exemplified in this review. It also gives examples of those modifications that enable the application of GNZs for in vivo biosensing and bioassays.

A fluorescent assay for alkaline phosphatase activity based on phosphorylation protection and DNAzyme-assisted amplification

Alkaline phosphatase is one of the most important tool enzymes and diseases indicator, monitoring ALP activity with convenient, precise, efficient and sensitive methods plays a fundamental role in modern life and healthcare industries. In this study, we described a novel method for ALP analysis based on Pb²⁺ dependent DNAzyme. By modifying DNAzyme sequence with terminal phosphate group and introducing exonuclease I (exo I), we managed to analyze ALP by utilizing its causal function of DNAzyme probe from exo I mediated degradation and function of triggering the subsequent cleavage of the hairpin reporting probe. Other than one amplificative strategy by DNAzyme mediated cleavage and cycle, this system also involved an exo I mediated degradation to further reduce the background noise. Combining stepwise fluorimetry and electrophoresis, we verified the detective mechanism of this proposed method. Further, after selectivity demonstration, this method achieved a considerable LOD of 0.0017 U L^-1 and linear range of 0.0025 U L^-1 to 250 U L^-1. For potential of practical application, this method also exhibited excellent performances in inhibitor screening and intracellular ALP assay, both with a linear fitting equation. Based on these results, this method should be highly committed for improving ALP analysis in modern life industry.

Catechin-inspired gold nanocluster nanoprobe for selective and ratiometric dopamine detection via forming azamonardine

The sensitive and selective perception of dopamine (DA, a typical neurotransmitter) is important to evaluate the biological environment. In this study, a catechin-functionalized gold nanocluster (C-Au NC) nanoprobe has been explored for the ratiometric DA sensing. The detection mechanism is based on the formation of azamonardine via selective DA-catechin chemical reaction and subsequent enhanced fluorescence emission. Using Au NC emission as the internal reference, ratiometric fluorescence variation is realized, which allows sensitive DA analysis with a limit of detection of 1.0 nM (S/N = 3) and linear response concentration range from 0 to 500 nM. The characteristic chemical reaction between catechin and DA affords favorable selectivity over other amino acids, metal ions and small molecules. In addition, the practical application of the proposed nanoprobe is validated by the accurate detection of DA content in urea and cell lysate samples.