A novel fluorescent probe with Aggregation-Induced emission characteristics for PTP1B activity sensing and inhibitor screening

Protein tyrosine phosphatase 1B (PTP1B) is an attractive target for the treatment of metabolic diseases such as type 2 diabetes and obesity. In this study, a novel fluorescent probe with aggregation-induced emission (AIE) characteristics was designed and synthesized. Within the fluorescent probe, a tetraphenylethene core is connected to a peptide sequence that can be specifically recognized and hydrolysed by PTP1B. Due to the dephosphorylation of PTP1B, the fluorescent probe exhibited AIE in a turn-on manner, indicating PTP1B activity. This probe was successfully used to detect PTP1B activity in HepG2 cell lysates. Then, a probe-based method was applied to screen for potential PTP1B inhibitors from a natural product library, and three novel PTP1B inhibitors were discovered. These findings indicated that the proposed approach offered a new avenue for discovering potential PTP1B inhibitors.

Real-time monitoring of dephosphorylation process of phosphopeptide and rapid assay of PTP1B activity based on a 100 MHz QCM biosensing platform

The misregulation of protein phosphatases is a key factor in the development of many human diseases, notably cancers. Here, based on a 100 MHz quartz crystal microbalance (QCM) biosensing platform, the dephosphorylation process of phosphopeptide (P-peptide) caused by protein tyrosine phosphatase 1B (PTP1B) was monitored in real time for the first time and PTP1B activity was assayed rapidly and sensitively. The QCM chip, coated with a gold (Au) film, was used to immobilized thiol-labeled single-stranded 5'-phosphate-DNAs (P-DNA) through Au-S bond. The P-peptide, specific to PTP1B, was then connected to the P-DNA via chelation between Zr4+ and phosphate groups. When PTP1B was injected into the QCM flow cell where the P-peptide/Zr4+/MCH/P-DNA/Au chip was placed, the P-peptide was dephosphorylated and released from the Au chip surface, resulting in an increase in the frequency of the QCM Au chip. This allowed the real-time monitoring of the P-peptide dephosphorylation process and sensitive detection of PTP1B activity within 6 min with a linear detection range of 0.01-100 pM and a detection limit of 0.008 pM. In addition, the maximum inhibitory ratios of inhibitors were evaluated using this proposed 100 MHz QCM biosensor. The developed 100 MHz QCM biosensing platform shows immense potential for early diagnosis of diseases related to protein phosphatases and the development of drugs targeting protein phosphatases.

Novel fluorescence biosensor custom-made for protein tyrosine phosphatase 1B detection based on titanium dioxide-decorated single-walled carbon nanohorn nanocomposite

This paper presents a new fluorescent approach for the detection of protein tyrosine phosphatase 1B (PTP1B) based on titanium dioxide-decorated single-wall carbon nanohorns (TiO₂-SWCNHs). The novel TiO₂-SWCNHs nanocomposite was synthesized and characterized for the first time and the phosphorylated peptide as the substrate of PTP1B was designed. Properties of SWCNHs and TiO₂ were combined by growing nano-sized TiO₂ particles on SWCNHs, resulting in TiO₂-SWCNHs. TiO₂ provides SWCNHs a large adsorption surface area and can specifically bind to phosphopeptide substrate. TiO₂-SWCNHs effectively quenched the fluorescence of the phosphorylated peptide substrate labeled by the fluorophore, and the system had a low fluorescence background. In the presence of PTP1B, dephosphorylation of the peptide occurred owing to the reaction between PTP1B and the peptide, causing the separation of the dye-labeled peptide from TiO₂-SWCNHs, which resulted in fluorescence enhancement of the reaction system. Thus, a simple and rapid strategy for the detection of PTP1B activity was developed, with a detection limit of 0.01 ng/mL and linear range of 0-10 ng/mL. The system can be used to detect PTP1B in serum using the standard addition method. This system provides a new approach for screening PTP1B inhibitors.

Bifunctional Magnetic Fe3O4@Cu2O@TiO2 Nanosphere-Mediated Dual-Mode Assay of PTP1B Activity Based on Photocurrent Polarity Switching and Nanozyme-Engineered Biocatalytic Precipitation Strategies

Dysregulation of protein phosphatases is associated with the progression of various human diseases and cancers. Herein, a photoelectrochemical (PEC)-quartz crystal microbalance (QCM) dual-mode sensing platform was developed for protein tyrosine phosphatase 1B (PTP1B) activity assay based on bifunctional magnetic Fe₃O₄@Cu₂O@TiO₂ nanosphere-mediated PEC photocurrent polarity switching and QCM signal amplification strategies. The PTP1B-specific phosphopeptide (P-peptide) with a cysteine end was designed and immobilized onto the QCM Au chip via the Au-S bond. Subsequently, the Fe₃O₄@Cu₂O@TiO₂ nanosphere was connected to the P-peptide via the specific interaction between the phosphate group on the P-peptide and TiO₂. After incubation with PTP1B, the dephosphorylation of the P-peptide occurred, causing some Fe₃O₄@Cu₂O@TiO₂ nanospheres to be released from the chip surface. The released magnetic Fe₃O₄@Cu₂O@TiO₂ nanospheres (labeled as R-Fe₃O₄@Cu₂O@TiO₂) were quickly separated via magnetic separation technology and attached to the Bi₂S₃-decorated magnetic indium-tin oxide (Bi₂S₃/MITO) electrode by magnetic force, inducing the switch of the photocurrent polarity of the electrode from anodic current (the Bi₂S₃/MITO electrode) to cathodic current (the R-Fe₃O₄@Cu₂O@TiO₂/Bi₂S₃/MITO electrode). Also, the nondephosphorylated P-peptide linked Fe₃O₄@Cu₂O@TiO₂ nanospheres as nanozymes with horseradish peroxidase activity to catalyze the formation of precipitation on the surface of the Au chip, leading to a frequency change of the QCM. Thus, the proposed PEC-QCM dual-mode sensing platform achieved accurate and reliable assay of PTP1B activity because of the different mechanisms and independent signal transductions. In addition, this dual-mode sensing platform can be easily extended for other protein phosphatase activity analysis and shows great potential in the early diagnosis of the protein phosphatase-related diseases and the protein phosphatase-targeted drug discovery.

Zinc-Air Battery-Assisted Self-Powered PEC Sensors for Sensitive Assay of PTP1B Activity Based on Perovskite Quantum Dots Encapsulated in Vinyl-Functionalized Covalent Organic Frameworks

The self-powered sensors have attracted widespread attention in the analysis field due to a huge demand of point-of-care testing (POCT) in the early diagnosis of diseases. However, the output voltage of the reported self-powered sensors is always small, resulting in a narrow linear detection range and low assay sensitivity. Herein, a self-powered photoelectrochemical (PEC) sensor with zinc-air batteries as a power source was developed for activity assay of protein tyrosine phosphatase 1B (PTP1B) based on perovskite quantum dots encapsulated in the vinyl-functionalized covalent organic framework (COF-V). CsPbBr₃ nanocrystals were stabilized by the confinement effect of the COF-V cage without aggregation, and the resulting CsPbBr₃@COF-V composite was used as the cathodic photoelectric material to construct the zinc-air battery with a large open-circuit voltage (OCV, 1.556 V). Before PTP1B activity assay, an auxiliary peptide-polyamidoamine-phosphopeptide (P2-PAMAM-P1) hybrid was introduced into the photocathode via thiol-ene click reaction between the thiol group on the P1 and the vinyl group on the COF-V. The steric hindrance effect of the P1-PAMAM-P2 hybrid inhibited the PEC performance of the photocathode, resulting in a small OCV of the zinc-air battery. When the PTP1B existed, PTP1B-catalyzed dephosphorylation of tyrosine on P1 facilitated the cleavage process of P1 by chymotrypsin, leading to the removal of the P2-PAMAM-P1 hybrid from the photocathode and consequently the enhancement of the OCV. Therefore, the activity of PTP1B was sensitively detected. The developed self-powered PEC sensor showed superior performance for PTP1B activity assay (broad linear response range, 0.1 pM to 10 nM and low detection limit, 0.032 pM) due to the large output voltage of the constructed zinc-air battery and has great potential in POCT of protein phosphatase-related diseases and the discovery of protein phosphatase-targeted drugs.

Dephosphorylation-directed tricyclic DNA amplification cascades for sensitive detection of protein tyrosine phosphatase

A new fluorescence method is developed for the sensitive detection of protein tyrosine phosphatase based on dephosphorylation-directed tricyclic DNA amplification cascades.

A colorimetric biosensor based on guanidinium recognition for the assay of protein tyrosine phosphatase 1B and its inhibitors

A new colorimetric biosensor for the assay of PTP1B and its inhibitors based on coordination between RGC/AuNPs and MNPs/APP.

A simple and visible colorimetric method through Zr4+–phosphate coordination for the assay of protein tyrosine phosphatase 1B and screening of its inhibitors

Inhibitors of protein tyrosine phosphatase 1B (PTP1B) are promising agents for the treatment of type 2 diabetes and obesity, so a colorimetric method has been developed in this work for PTP1B assay and screening of its inhibitors.

Adsorption between TC-stabilized AuNPs and the phosphate group: application of the PTP1B activity assay

Based on the adsorption between tetracycline (TC) and phosphate groups, a general colorimetric method is explored in this work by using TC-stabilized gold nanoparticles (TC/AuNPs) and 4-aminophenyl phosphate-functionalized Fe₃O₄ magnetic nanoparticles (APP/MNPs).