Functioned Calix[4]arenes as Artificial Enzymes Catalyze Aldol Condensation

Aldolase models derived from calix[4]arene were designed and synthesized. The aldol condensation of p-nitrobenzaldehyde with acetone was catalyzed by the synthetic enzymes proceeded under mild conditions to offer chiefly aldol-type product in good yield.

Light-responsive organic artificial enzymes:Material designs and bio-applications

As significant biocatalysts,natural enzymes have exhibited a vast range of applications in biocatalytic reactions.However,the“always-on”natural enzyme activity is not beneficial for the regulation of catalytic processes,which limits their bio-applications.Recently,it has been extensively reported that various organic artificial enzymes exhibit prominent absorption and controlled activity under illumination,which not only creates a series of light-responsive catalytic platforms but also plays a key role in biosensing and biomedical research.To provide novel ideas for the design of artificial enzymes,we conduct this review to highlight the recent progress of light-responsive organic artificial enzymes(LOA-Enz).The specific photoresponse mechanism and various bio-applications of LOA-Enz are also presented in detail.Furthermore,the remaining challenges and future perspectives in this field are discussed.

Studies on Artificial Imitation of Glutathione Peroxidase by Chemical Mutation

fter the alcoholic group of serine located in the binding site of Anti-HumanIgM(Fcμ) (Rabbit IgG) was selectively activated by phenylmethylsulfonyl fluoride(PMSF) and displaced with hydrogen selenide(H2Se) , the serine residue was con-verted to selenocysteine(SeCys). Because SeCys is a catalytic group of glutathioneperoxidase (GPX), the mutated antibody has the GPX activity which is seventytimes more than that of PZ51, the best GPX mimic in the world. Moreover, themutated antibody remains its original antibody titer.

Regulation of artificial supramolecular transmembrane signal transduction by selenium-containing artificial enzyme receptors

Signal transduction across lipid bilayers is of profound importance in biological processes.In biological systems,natural enzymes mediate biochemical effects by binding to substrates and facilitating the conversion of external signals into physiological responses.Sequential transmission of biological signals from one enzyme to the next promotes signal transduction with feedforward and feedback mechanisms.Reconstructing these processes in an artificial system provides potential applications and offers a new way to understand fundamental biological processes in depth.However,the design of artificial signal transduction systems regulated by artificial enzyme receptors in a predictable and intelligent manner remains a challenge.Herein,benefiting from the polarity-regulated characteristics of Se-containing compounds with artificial glutathione peroxidase(GPx)activity,we constructed an artificial transmembrane signaling receptor with a Se-containing GPx-like recognition head group,a membrane-anchoring group,and a pre-enzyme end group.The artificial supramolecular signal transduction system containing such signal transduction receptors extends the range of signaling systems based on enzyme regulation,which provides a new way to study natural signal processes in cells and artificially regulated biological processes.

Aggregation-induced emission artificial enzyme(AIEzyme)with DNase-like activity:Imaging and matrix cleavage for combating bacterial biofilm

DNase-catalyzed hydrolysis of extracellular DNA(eDNA)has been widely employed to eradicate intractable biofilms.Although aggregation-induced emission(AIE)has become the ideal tool for killing planktonic bacteria,AIE luminogens(AIEgens)often lack DNase-mimetic activity,so as to suffer from poor anti-biofilm capacity.Here,an“AIEzyme”,a kind of AIE nanomaterial with enzyme-like activity,is designed and synthesized,where the AIEgens are used as the ligands of Zr-based coordination polymer nanoparticles.Not only does AIEzyme have enduring DNasemimetic activity with low activation energy,but also structural rigidity-stabilized fluorescence.Due to the long-acting hydrolysis for eDNA in biofilm,AIEzyme can efficiently disorganize the established biofilms with good penetrability and realize the healing of superbug-infected wounds under only one dose of AIEzyme.This work provides a strategy to endow ordinary AIEgens with DNase-like and antibiofilm activities.Moreover,AIEzymes can be observed by virtue of their own AIE character,facilitating the study on self-positioning and residual amount of AIEzymes in wounds.The concept“AIEzyme”would hopefully stimulate the tremendous expansion for the tool kits and the application of AIEgens and artificial enzymes.

Dual inhibition of glycolysis and oxidative phosphorylation by aptamer-based artificial enzyme for synergistic cancer therapy

Dual inhibition of glycolysis and oxidative phosphorylation(OXPHOS)can break the metabolic plasticity of cancer cells to inhibit most energy supply and lead to effective cancer therapy.However,the pharmacokinetic difference among drugs hinders these two inhibitions to realize a uniform temporal and spatial distribution.Herein,we report an aptamer-based artificial enzyme for simultaneous dual inhibition of glycolysis and OXPHOS,which is constructed by arginine aptamer modified carbon-dots-doped graphitic carbon nitride(AptCCN).AptCCN can circularly capture intracellular arginine attribute to the specific binding ability of arginine aptamers to arginine,and further catalyze the oxidation of enriched arginine to nitric oxide(NO)under red light irradiation.In vitro and in vivo experiments showed that arginine depletion and NO stress could inhibit glycolysis and OXPHOS,leading to energy blockage and apoptosis of cancer cells.The presented aptamer-based artificial enzyme strategy provides a new path for cell pathway regulation and synergistic cancer therapy.

Hydrogel-based artificial enzyme for combating bacteria and accelerating wound healing

Artificial enzymes have provided great antimicrobial activity to combat wound infection.However,the lack of tissue repair capability compromised their treatment effect.Therefore,development of novel artificial enzyme concurrently with the excellent antibacterial activity and the property of promoting wound healing are required.Here,we demonstrated the hydrogel-based artificial enzyme composed of copper and amino acids possessed intrinsic peroxidase-like catalytic activity,which could combat wound pathogen effectively and accelerate wound healing by stimulating angiogenesis and collagen deposition.Furthermore,the system possesses good biocompatibility for practical application.The synergic effect of the hydrogel-based artificial enzyme promises the system as a new paradigm in bacteria-infected wound healing therapy.

Nanozymes for biomedical applications in orthopaedics

As the next generation of artificial enzymes,nanozymes have attracted increasing attention in biomedical applications due to their multienzyme-like characteristics,multifunctionalities,low cost,and high stability.By taking advantage of their diverse activities,a growing number of nanozyme-mediated therapeutic strategies have been developed for various diseases.Herein,we provide a brief review of the representative studies of nanozymes,especially in orthopaedic diseases over the past decade,which include arthritis,osteoporosis,bone regeneration,bacteria-associated infections,and osteosarcoma.Moreover,the future potential applications and some major challenges are also discussed.This review would not only provide some instructive views of nanozymes but also promote the development of enzyme-mimetic strategies in orthopaedics.

A colorimetric assay for cholesterol based on the encapsulation of multienzyme in leaf-shape crossed ZIF-L

The serum cholesterol level is an important indicator of healthy and there is a great necessity for frequent cholesterol monitoring to some cardiovascular-related diseases, which puts forward higher requirements for point-of-care testing(POCT) of cholesterol. In this work, a cascade catalytic system of cholesterol is developed by encapsulation of cholesterol oxidase(Ch Ox) and Pd Cu Au nanoparticles into zeolitic imidazolate framework-L(Ch Ox/PCA@ZIF-L). Results indicate that ZIF-L carrier can significantly increase the catalytic activity of single or multiple enzymes, due to its high loading capacity and efficient molecular transport. Under the optimal conditions, the absorbance of reaction system performs linear relationships with the concentration of cholesterol in two intervals from 0.0005 mmol/L to 1.0000 mmol/L, with a limit of detection of 0.2176 μmol/L. The proposed colorimetric strategy based on Ch Ox/PCA@ZIF-L performs a good agreement with the results provided by chemiluminescence method for the serum cholesterol detection. Interestingly, a simple paper-based sensing system is constructed through a pre-reaction-transfer operation, which gets rid of the complex pre-processing requirements of traditional operations on filter paper. The presented strategy allows for the sensitive, convenient, costless assay of serum cholesterol,and paves a new way to design the POCT device for daily monitoring of healthy.

Porous Ruthenium Selenide Nanoparticle as a Peroxidase Mimic for Glucose Bioassay

Nanozyme is a promising field that offers the substitution for natural enzymes using various nanomaterials.Various nanoma-terials with peroxidase-like activity were investigated.Among them,transition metal chalcogenides were explored as promis-ing nanozymes due to their excellent enzyme-mimicking activities.However,ruthenium selenide has not been studied as a peroxidase mimic because of the difficulty for synthesis.Herein,we prepared ruthenium selenide nanomaterial with ordered mesoporous structure(P-RuSe_(2))employing KIT-6 silica as the template.The composition and structure of P-RuSe_(2) were fully characterized.Further,its peroxidase-like activity was investigated.P-RuSe_(2) possessed excellent peroxidase-mimicking activ-ity,which catalyzed the oxidation of peroxidase substrates,including 3,3′,5,5′-tetramethylbenzidine,o-phenylenediamine,and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)in the presence of H_(2)O_(2).Moreover,P-RuSe_(2) exhibited higher peroxidase-like activity when compared with several representative nanozymes as well as bulk RuSe_(2).To demonstrate its potential applications,the colorimetric detection systems for H_(2)O_(2) and glucose were successfully constructed based on P-RuSe_(2) nanozyme.

Tumor microenvironment-responsive MnSiO_(3)-Pt@BSA-Ce6 nanoplatform for synergistic catalysis-enhanced sonodynamic and chemodynamic cancer therapy

Compared with traditional photodynamic therapy(PDT),ultrasound(US)triggered sonodynamic therapy(SDT)has a wide application prospect in tumor therapy because of its deeper penetration depth.Herein,a novel MnSiO_(3)-Pt(MP)nanocomposite composed of Mn Si O_(3)nanosphere and noble metallic Pt was successfully constructed.After modification with bovine serum albumin(BSA)and chlorine e6(Ce6),the multifunctional nanoplatform Mn SiO_(3)-Pt@BSA-Ce6(MPBC)realized the magnetic resonance imaging(MRI)-guided synergetic SDT/chemodynamic therapy(CDT).In this nanoplatform,sonosensitizer Ce6 can generate singlet oxygen(^(1)O_(2))to kill cancer cells under US irradiation.Meanwhile,the loaded Pt has the ability to catalyze the decomposition of overexpressed hydrogen peroxide(H_(2)O_(2))in tumor microenvironment(TME)to produce oxygen(O_(2)),which can conquer tumor hypoxia and promote the SDT-induced^(1)O_(2)production.In addition,MP can degrade in mildly acidic and reductive TME,causing the release of Mn^(2+).The released Mn^(2+) not only can be used for MRI,but also can generate hydroxyl radical(^·OH)for CDT by Fenton-like reaction.The multifunctional nanoplatform MPBC has high biological safety and good anticancer effect,which displays the great latent capacity in biological application.

Molecular Hydrogels with Esterase-like Activity

The development of molecular hydrogels that can be applied for mimicking bioactive molecules attracts exten- sive interests of researchers in fields of self-assembly. In this study, we reported on several molecular hydrogels based on naphthylacetic acid-peptides containing L-histidine formed by the heating-cooling process. All hydrogels exhibited higher activity to hydrolyze 4-nitrophenyl acetate （4-NPA） than the free L-histidine probably due the high density of L-histidine residue at the surface of self-assembled nanofibers. To calculate the 4-NPA hydrolysis rates, the Michaelis-Menten enzyme kinetics model was made. Among these gels, the gel of Nap-GFFYGHY possesses the highest enzyme activity of making the ester bond cleavage, which is approximately 25 times higher than that of the control （free L-histidine and Nap-GFFYGYY）. These results indicate that molecular hydrogels with self-assembled nanofibers have great potential for the generation of self-assembled multivalent materials.

The Analysis of Zirconium (Ⅳ) Oxide (ZrO_(2)) Nanoparticles for Peroxidase Activity

In this study,the peroxidase-like activity of zirconium(Ⅳ)oxide nanoparticles(nZr)is reported.Peroxidases catalyze the oxidation of their substrate in the presence of peroxide species.3,3′,5,5′-tetramethylbenzidine(TMB)is a peroxidase substrate,and we have demonstrated that nZr oxidizes the TMB in the presence of hydrogen peroxide resulting in a colored(TMBox)product.The reaction was tested in various buffers,and sodium acetate with pH 4 was observed to be an ideal buffer for the enzymatic reaction and the dispersity of the nZr in the solution.The nanozyme behavior was studied systematically at three different temperatures(25,35 and 45℃)and a wide range of H_(2)O_(2) concentrations.The dependence of the enzymatic reaction on temperature,nZr content and H_(2)O_(2) concentration was observed.The enzymatic reaction was tested in different protein solutions and no noticeable interference was observed with these proteins.Overall,we demonstrate that nZr,which is often used for industrial applications,mimics peroxidase enzyme and catalyzes oxidation of its substrate in the presence of peroxide species.