Enhancing the photo-induced oxidase-like activity of fluorescein with methyl viologen for colorimetric detection of organophosphorus pesticide.

Overcoming the intrinsic low activity of most photoinduced oxidase mimics has been extremely challenging. In this work, we developed a methyl viologen (MV) mediated strategy to enhance the oxidase-like activity of fluorescein. The presence of MV gives it a high affinity for TMB with a low Michaelis-Menten constant (K) of 0.

Intrinsic oxidase-mimicking activity of nitrite upon visible light illumination and its colorimetric detection in saliva.

Small molecules with enzyme-like properties have recently attracted considerable attention. Herein, we discovered that nitrite possesses intrinsic oxidase-mimicking activity upon visible light, catalyzing the oxidation of the typical chromogenic substrate in the absence of HO. Notably, nitrite exhibited a markedly high value of K, approximately 4, 7, and 4000-fold greater than that of Acr-Mes, Eosin Y, and Diacetyl, respectively.

Detecting uric acid base on the dual inner filter effect using BSA@Au nanoclusters as both peroxidase mimics and fluorescent reporters.

Fluorescent bovine serum albumin-protected gold nanoclusters (BSA@Au NCs) can catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to produce blue oxTMB for its peroxidase-like activity. The two absorption peaks of oxTMB overlapped with the excitation and emission peaks of BSA@Au NCs, respectively, causing efficient quenching on the fluorescence of BSA@Au NCs. The quenching mechanism can be attributed to the dual inner filter effect (IFE).

Colorimetric detection of biothiols and Hg based on the peroxidase-like activity of GTP.

Guanosine-5'-triphosphate (GTP) not only plays a key role in a majority of cellular processes but also be proposed as a peroxidase-like mimic. Compared with nanozymes, GTP shows good tolerance under harsh conditions, which can be used to construct an easy colorimetric analysis for the detection of biomolecules. Here, on the basis of the peroxidase-like activity of GTP which can catalyze the oxidation of 3,3',5,5'-tetramethyl benzidine dihydrochloride (TMB), colorimetric sensing was established for biothiols and Hg.

Ru(bpy) as a photoinduced oxidase mimic for colorimetric detection of biothiols.

We have found that tris (2,2'-bipyridyl) ruthenium (II) (Ru(bpy)) possesses a high photo-induced oxidase-like activity and is capable of catalyzing the color reaction of 3,3',5,5'-tetramethylbenzidine (TMB) with dissolved oxygen. Ru(bpy) has a catalytic constant (K) that is twice as high as that of fluorescein, 170 and 275-fold higher than that of 9-mesityl-10-methyl acridine and Eosin Y, respectively. Electron spin resonance spectroscopy (ESR) and radical scavenging experiments have verified the major active radicals involved in the color reaction are •OH.

Colorimetric detection of ATP by inhibiting the Peroxidase-like activity of carbon dots.

Adenosine triphosphate (ATP) is the main energy currency for cells and an important biomolecule involved in cellular reactions, whose abnormal levels are closely related to physical disease, thus it is extremely important to establish a convenient, fast and simple ATP monitoring method. Toward this end, we developed a facile method for colorimetric detection of ATP on the basis of the inhibiting effect of ATP on the peroxidase-like activity of carbon dots (CDs). The detection principle of this method was utilizing the peroxidase-like activity of CDs, which catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by HO to generate blue products.

Metal-free colorimetric detection of pyrophosphate ions by the peroxidase-like activity of ATP.

Pyrophosphate (PO, PPi) plays a vital role in ecological environment. Its elevated levels in water bodies can lead to eutrophication. Hence, its detection is extremely significant.

Enhancing the peroxidase activity and decreasing the protease activity of ficin with rational modification and its application to one-step colorimetric detection of glucose.

Ficin has dual enzyme activity, i.e., protease and peroxidase-like activity.

Reducing background absorbance via a double-lock strategy for detection of alkaline phosphatase and α-fetoprotein.

Lowering the background signal for more sensitive analysis of determinands is as important as amplifying the target signal. The photoinduced oxidase of fluorescein has been reported, which can catalyze the oxidization of common substrates in a few minutes. As a metaphor for locks and keys, we designed double locks confining the activity of fluorescein to reduce the background absorbance during colorimetric detection.

Bifunctional antibody and copper-based metal-organic framework nanocomposites for colorimetric α-fetoprotein sensing.

Cu are found to greatly reduce the photoinduced oxidase activity of fluorescein and then inhibit the chromogenic reaction catalyzed by fluorescein. A simple colorimetric assay for Cu is established. Based on this, bifunctional nanocomposites of α-fetoprotein (AFP) antibody (Ab) and copper-based metal-organic framework (Ab2@Cu-MOF) are synthesized by the simple self-assembly of AFP Ab2, Cu, and 4,4'-dipyridyl: the binding site of AFP Ab2 exposed on the surface of the nanocomposites can specifically recognize AFP antigen; Cu in nanocomposites can inhibit the visible light-induced activity of fluorescein.

Cetyltrimethylammonium chloride-loaded mesoporous silica nanoparticles as a mitochondrion-targeting agent for tumor therapy.

Mitochondria play an important role in supplying cellular energy, cell signaling and governing cell death. In addition, mitochondria have also been proved to be essential for tumor generation and development. Thus, mitochondrion-targeting therapeutics and treatments have emerged as promising strategies against cancer.

A signal amplification strategy for prostate specific antigen detection via releasing oxidase-mimics from coordination nanoparticles by alkaline phosphatase.

A novel signal amplification method for prostate specific antigen (PSA) is developed by freeing fluorescein with photoinduced oxidase-like activity from coordination nanoparticles (CNPs) in the presence of alkaline phosphatase (ALP). CNPs loaded with fluorescein (F@CNPs) are obtained in aqueous solution by self-assembly using Tb as metal ion, guanosine monophosphate (5'-GMP) as ligand, and fluorescein as signal molecule. The F@CNPs display outstanding properties of simple synthesis, low cost, good water solubility, negligible leakage and satisfactory load capacity.

Ficin encapsulated in mesoporous metal-organic frameworks with enhanced peroxidase-like activity and colorimetric detection of glucose.

Ficin has been reported to possess peroxidase activity, but its applications in some respects have been limited because of its relatively low activity. Herein, a mesoporous metal-organic framework, PCN-333(Fe), was synthesized, which was selected to encapsulate ficin to form ficin@PCN-333(Fe). Compared with ficin, the peroxidase-like activity of ficin@PCN-333(Fe) toward 3,3',5,5'-tetramethylbenzidine (TMB) oxidation was about 3 times increase in the presence of HO, and followed classical Michaelis-Menten model.

A siramesine-loaded metal organic framework nanoplatform for overcoming multidrug resistance with efficient cancer cell targeting.

Cancer is the leading cause of death and the most important obstacle to increasing life expectancy. With the sophisticated design and research of anticancer drugs, multidrug resistance to chemotherapy has become more and more common. After the emergence of multidrug resistance, the development of a new drug is beset with difficulties.

Enhancing the peroxidase-like activity of ficin by rational blocking thiol groups for colorimetric detection of biothiols.

The peroxidase-like activity of ficin is relatively low, which limits its application. It was found that thiol groups of ficin could inhibit its peroxidase-like activity. So, two procedures, i.

Tuning the fluorescence performance of carbon dots with a reduction pathway.

A reduction pathway was developed to tune the fluorescence quantum yield (QY) and emission wavelength of carbon dots (CDs). Reducing the original CDs (QY ca. 1.

One-pot synthesis of a composite consisting of the enzyme ficin and a zinc(II)-2-methylimidazole metal organic framework with enhanced peroxidase activity for colorimetric detection for glucose.

An enzyme-metal organic framework (MOF) composite with saucer-like structure was prepared via one-pot synthesis from ficin (a cysteine proteolytic enzyme with POx activity), zinc(II) ions and 2-methylimidazole. The composites exhibit a 2.5-fold higher catalytic activity and stronger affinity for substrates compared to free ficin.

Competitive method for fluorescent dopamine detection in cerebrospinal fluid based on the peroxidase-like activity of ficin.

Dopamine (DA), a catecholamine neurotransmitter, is considered to be an important indicator for mental diseases detection in the clinic. In this study, a novel fluorescent sensing platform consisting of the ficin-HO-tyramine system for determining DA in cerebrospinal fluids (CSF) was established. The proposed method is based on the fact that ficin, a mimetic peroxidase, can catalyze HO decomposition into OH radicals, which can oxidize non-fluorescent tyramine into fluorescent dityramine.

Acidic amino acids: A new-type of enzyme mimics with application to biosensing and evaluating of antioxidant behaviour.

Nanomaterials have triggered tremendous interest to mimick peroxidase but rarely attention has been paid to small molecules. Herein we first found that acidic amino acids including l-glutamic acid (L-Glu) and l-aspartic acid (L-Asp) exhibited an intrinsic peroxidase-like activity, endowing acidic amino acids with the capability of catalysing the oxidation of the peroxidase substrates 3,3',5,5'-tetramethylbenzidine (TMB) to produce color reaction in the presence of HO. Reaction mechanism was further investigated by means of electron spin resonance spectroscopy (ESR), enzyme kinetics assay and quantum theoretical calculations, to verify and provide a good deal of insight into the catalytic process.

Enhancing the peroxidase-like activity of ficin via heme binding and colorimetric detection for uric acid.

Ficin, a classical sulfhydryl protease, was found to possess intrinsic peroxidase-like activity. In this paper, we have put forward a novel strategy to improving the peroxidase-like activity of ficin through binding heme. Heme-ficin complexes were successfully obtained by simple one-step syntheticism.

Quantum dots-based sandwich immunoassay for sensitive detection of Alzheimer's disease-related Aβ.

Amyloid-beta peptide 1-42 (Aβ) is known as a component of amyloid plaques in association with Alzheimer's disease. Herein, we developed a reliable and remarkably sensitive sandwich immunoassay to detect the Aβ using quantum dots (QDs) as fluorescent label. In the presence of Aβ, the biotinylated Anti-beta Amyloid 1-16 (N-Ab) recognized the target and formed C-Ab-Aβ-N-Ab sandwich immunocomplexes.

Hollow carbon dots labeled with FITC or TRITC for use in fluorescent cellular imaging.

Hollow carbon dots (HCDs) were prepared by a solvothermal method and conjugated to either tetramethyl rhodamine isothiocyanate (TRITC) or fluorescein-5-isothiocyanate (FITC). This resulted in HCDs with bright red or green fluorescence, with excitation/emission peaks at 550/580 and 491/520 nm, respectively. The nanocomposites are well water-soluble, remarkably photostable and biocompatible.

Peroxidase-like activity of 2',7'-difluorofluorescein and its application for galactose detection.

The peroxidase-like activity of 2',7'-difluorofluorescein (DFF), was investigated using 3,3',5,5'-tetramethylbenzidine (TMB) as a chromogenic substrate in the presence of HO. DFF could catalyze oxidization of TMB by HO to produce a blue colored oxidation product. Effect of various reaction conditions, such as pH, temperature, HO concentration and reaction time on the catalytic activity of DFF was studied.

Fluorescein as a Visible-Light-Induced Oxidase Mimic for Signal-Amplified Colorimetric Assay of Carboxylesterase by an Enzymatic Cascade Reaction.

We have found that fluorescein possesses high visible-light-induced oxidase mimetic activity and could transform colorless 3,3',5,5'-tetramethylbenzidine (TMB) into blue oxidized TMB (oxTMB) without unstable and destructive H O under visible-light illumination. Instead, fluorescein uses oxygen as a mild and green electron acceptor, and its activity can be easily controlled by the switching "on/off" of visible light. In addition, the visible-light-induced catalytic mechanism was elucidated in detail and, as the main reactive species h and O accounted for TMB oxidation.

Targeted H-Triggered Bubble-Generating Nanosystems for Effective Therapy in Cancer Cells.

A novel targeting drug delivery system for cancer therapy based on H-triggered bubble-generating nanosystems (BGNSs) was engineered. First, hollow mesoporous silica nanoparticles (HMSNs) were used to load doxorubicin (DOX). Then, the obtained drug-loaded HMSNs were treated with NaHCO to prepare the BGNSs.