Visual detection of hexokinase activity and inhibition with positively charged gold nanoparticles as colorimetric probes

Colorimetric Detection of Organophosphate Pesticides Based on Acetylcholinesterase and Cysteamine Capped Gold Nanoparticles as Nanozyme

Organophosphates (OPs) are neurotoxic agents also used as pesticides that can permanently block the active site of the acetylcholinesterase (AChE). A robust and sensitive detection system of OPs utilising the enzyme mimic potential of the cysteamine capped gold nanoparticles (C-AuNPs) was developed. The detection assay was performed by stepwise addition of AChE, parathion ethyl (PE)-a candidate OP, acetylcholine chloride (ACh), C-AuNPs, and 3, 3′, 5, 5′-tetramethylbenzidine (TMB) in the buffer solution. The whole sensing protocol completes in 30–40 min, including both incubations. The Transmission Electron Microscopy (TEM) results indicated that the NPs are spherical and have an average size of 13.24 nm. The monomers of C-AuNPs exhibited intense catalytic activity (nanozyme) for the oxidization of TMB, revealed by the production of instant blue colour and confirmed by a sharp peak at 652 nm. The proposed biosensor’s detection limit and linear ranges were 5.8 ng·mL⁻¹ and 11.6–92.8 ng·mL⁻¹, respectively, for PE. The results strongly advocate that the suggested facile colorimetric biosensor may provide an excellent platform for on-site monitoring of OPs.

Versatile small molecule kinase assay through real-time, ratiometric fluorescence changes based on a pyrene-DPA-Zn2+ complex

A real-time kinase assay method based on a ratiometric fluorescence probe that can be applied to various small-molecule kinases is described herein. The probe can trace the reversible interchange of ATP and ADP, which is a common phenomenon in most small-molecule kinase reactions, by a ratiometric fluorescence change. This property facilitates the monitoring of phosphorylation and dephosphorylation in small-molecule kinases, whereas most of the existing methods focus on one of these reactions. To prove the applicability of this method for small-molecule kinase assays, hexokinase and creatine kinase, which phosphorylate and dephosphorylate substrates, respectively, were analyzed. The ratiometric fluorescence change was correlated with the enzyme activity, and the inhibition efficiencies of the well-known inhibitors, N-benzoyl-d-glucosamine and iodoacetamide, were also monitored. Notably, the change in fluorescence can be observed with a simple light source by the naked eye.

A versatile assay system that can be trace both phosphorylation and dephosphorylation by small molecule kinase is demonstrated, and can be applied regardless of substrate diversity.

Sensitive detection of hexokinase activity by use of Zr(4+)-coated magnetic beads coupled with phenylboronic acid-functionalized upconversion nanophosphors

Hexokinase (HK)-catalyzed glucose phosphorylation plays an important role in the regulation of circulating glucose levels, so aberrant HK activity may result in various human diseases. Herein, we present a new strategy for highly sensitive detection of HK activity by use of Zr(4+)-coated magnetic beads (ZrMBs) for selective capture of HK-induced phospho-glucose coupled with phenylboronic acid-functionalized upconversion nanophosphors (UCNPs) for specific recognition and low-background detection of the phospho-glucoses anchored on the ZrMBs. In this design, ZrMBs exhibit highly selective binding utility for the phospho-glucose, which binds on the surface of ZrMBs while the unphosphorylated glucose does not. In addition, the magnetic nature of ZrMBs allows the simple purification and separation operations. On the other hand, phenylboronic acid-functionalized UCNPs can specifically recognize the phospho-glucoses anchored on the ZrMBs through strong boronic acid-diols interaction, so the UCNPs finally accumulated on the ZrMBs are proportional to the HK activity. The utilization of UCNPs as the signal reporters can greatly reduce the autofluorescence and light scattering interferences owing to their NIR excitation characteristic, which results in a high signal-to-background ratio. Therefore, by combining these distinct advantages of UCNPs and ZrMBs, ultrahigh sensitivity for the detection of HK activity is achieved.