An electrochemical determination strategy for miRNA based on bimetallic nanozyme and toehold-mediated DNA replacement procedure.

An electrochemical strategy based on bimetallic nanozyme in collaboration with toehold-mediated DNA replacement effect is proposed for the sensitive determination of miRNA-21. The AuPt nanoparticles (AuPt NPs) are prepared as a catalytic beacon; it shows favorable peroxidase properties with a Michaelis contant (Km) of 0.072 mM for H2O2, which is capable of catalyzing H2O2 to induce an intense redox reaction, and causing a measurable electrochemical signal. To further enhance the strength of the signal response, a novel toehold-mediated DNA replacement strategy is employed. DNA strands with specific sequences are modified on electrodes and AuPt NPs, respectively. In the presence of miRNA-21, a cyclic substitution effect is subsequently activated via a specific toehold sequence and leads to a large accumulation of AuPt NPs on the electrodes. Subsequently, a strong signal depending on the amount of miRNA-21 is obtained after adding a small amount of H2O2. The analytical range of this determination method is from 0.1 pM to 1.0 nM, and the LOD is 84.1 fM. The spike recoveries for serum samples are 95.0 to 102.4% and the RSD values are 3.7 to 5.8%. The results suggests a promising application of the established method in clinical testing and disease diagnosis.

Redox-Responsive Breakup of a Nucleic Acids@CoOOH Nanocomplex Triggering Cascade Recycling Amplification for Sensitive Sensing of Alkaline Phosphatase.

Alkaline phosphatase (ALP), an essential hydrolase with crucial roles in living organisms, has widely been regarded as a biomarker for various human diseases in clinical diagnoses. Herein, taking advantage of cobalt oxyhydroxide (CoOOH) nanoflakes and nonenzymatic cascade recycling amplification (CRA), a highly sensitive and label-free fluorescence biosensing strategy for the determination of ALP activity is introduced. In our design, ALP can promote the dephosphorylation of l-ascorbic acid 2-phosphate (AAP) to reduce ascorbic acid (AA), which is then able to decompose CoOOH in a nucleic acids@CoOOH nanocomplex into Co2+ cofactors. Further, enzyme-free CRA was rapidly initiated by integrating DNAzyme recycling amplification and catalytic hairpin assembly, resulting in the generation of an abundance of G-quadruplex structure-contained DNA duplexes. In the presence of thioflavin T (ThT), analytical target ALP was converted in an amplified and activatable fluorescence signal. The experimental results show that this method can be applied for the quantitative analysis of ALP activity with a low detection limit of 0.027 mU/mL. Moreover, this developed biosensing approach exhibits excellent specificity, and the evaluation of ALP activity in the complex human serum samples was successfully realized, indicating that it can afford a reliable, robust, and cost-effective nanoplatform for an ALP-based clinical diagnosis and for biomedical research.

A Facile, Label-free and Versatile Fluorescence Sensing Nanoplatform Based on Titanium Carbide Nanosheets for the Detection of Various Targets.

The construction of a universal nanoplatform for sensitive detection of multiple targets of interest is of great importance in different research fields. Herein, by ingeniously integrating the target recognition sequences and G-rich sequences into a single-stranded multifunctional DNA probe and adopting Ti3C2 nanosheets as an efficient fluorescence quencher, a simple, low-cost and easy operation fluorescence sensing nanoplatform was proposed. Without an analytical target, the hydrogen bond and metal chelate interaction between the target recognition region of the DNA probe and Ti3C2 nanosheet induce the selective self-assembly of highly fluorescent thioflavin T (ThT)-intercalated DNA probe onto the surface of Ti3C2 nanosheets, resulting in dramatic decrease of fluorescence emitted by ThT-G-quadruplex. In the presence of a target, the target recognition region will selectively bind with the target and the constrained DNA probe is released from the Ti3C2 nanosheets surface, leading to enhanced fluorescence recovery of ThT-G-quadruplex. As a proof of concept, the sensitive and selective detection of p53 gene, Hg2+, and adenosine with the assistance of Ti3C2 nanosheets-based fluorescence sensing nanoplatform were successfully realized. Moreover, it is also applicable for the evaluation the level of these analytical targets in real samples. By simply switching the recognition sequences of DNA probe, the universal sensing strategy could also be applied for detecting many other types of targets. The simple and universal sensing nanoplatform is expected to promote wide applications in environment monitoring and bioanalysis.

Cu2+-mediated turn-on fluorescence biosensor based on DNA-templated silver nanoclusters for label-free and sensitive detection of adenosine triphosphate.

A Cu2+-mediated turn-on fluorescence biosensor based on the DNA-templated green-emitting silver nanoclusters (DNA@g-AgNCs) was developed for label-free and sensitive detection of adenosine 5'-triphosphate (ATP). Cu2+ was able to quench the bright green fluorescence of DNA@g-AgNCs because of the coordination and photoinduced electron transfer between DNA@g-AgNCs and Cu2+. Therefore, a unique and effective fluorescence biosensor can be constructed with the formation of DNA@g-AgNCs/Cu2+/ATP ternary-competition system. With the introduction of ATP, the DNA@g-AgNCs/Cu2+ fluorescence sensing system will be disrupted and the fluorescence of DNA@g-AgNCs was recovered due to higher affinity of ATP towards Cu2+. On the basis of this feature, the DNA@g-AgNCs/Cu2+ fluorescence sensing system demonstrated quantitative determination of ATP in the range 0.05 - 3 µM and a detection limit of 16 nM. Moreover, the fluorescence sensing system was successfully applied to the quantitative determination of ATP in human urine and serum samples with recoveries ranging from 98.6 to 106.5%, showing great promise to provide  a label-free, cost-efficient, and rapid platform for ATP-related clinical disease diagnosis.

A ratiometric fluorescence strategy based on inner filter effect for Cu2+-mediated detection of acetylcholinesterase.

A novel ratiometric fluorescence strategy for detection of acetylcholestinerase (AChE) is proposed based on carbon nitride quantum dots (g-CNQD) and the complex (PA) formed between phenylboronic acid (PBA) and alizarin red S (ARS). PA showed fluorescence at 598 nm and quenched the fluorescence of g-CNQD at 438 nm. Through UV-visible absorption, fluorescence, and fluorescence lifetime measurements, the quenching effect was demonstrated as inner filter effect (IFE). When Cu2+ was added, the coordination of ARS and Cu2+ decreased the fluorescence of PA at 598 nm and recovered that of g-CNQD at 438 nm. In the presence of AChE it catalyzed the hydrolysis of acetylthiocholine (ATCh) to produce thiocholine (TCh) which competed with ARS for binding to Cu2+; thus, the fluorescence at 598 nm increased and that at 438 nm decreased again. Under the mediation of Cu2+, the fluorescence ratio F598/F438 of PA-CNQD probe had good linear relationship with AChE concentration in the range 0.5-15 mU/mL with a detection limit of 0.36 mU/mL. The method was successfully applied to the determination of AChE in human serum and the screening of inhibitors.

DNA cyclic assembling control in an electrochemical strategy with MoS2@AuNPs for determination of kanamycin.

A sensitive electrochemical strategy was established for kanamycin determination. A specific aptamer was modified on the electrode as the probe, followed by a cyclic hybridization chain reaction (HCR) with methylene blue, causing an increasing signal response. In the presence of kanamycin, it can initiatively convolve the aptamer and prevent further DNA assembling, resulting in a signal distinction sensitive to the target amount. However, the signal reproducibility is low. To improve the precision, the HCR procedure was investigated. The results demonstrated that the optimal amount of assembled DNA is 12-fold to that of aptamer. This amount was then controlled in further assays. Admittedly, controlled DNA assembling commonly indicates a limited signal amplification. To further enhance the sensitivity, a nanocomposite based on MoS2 and AuNPs was modified on the electrode. The results of the assay proved that the signal distinction sensitive to target amount increased by 50%. A linearity range is obtained from 0.01 nM to 1.0 µM of kanamycin, and the LOD is 8.4 pM. Subsequently, this strategy was employed to detect kanamycin in chicken liver and milk sample; the recovery results suggest that it possess a satisfactory application prospect in analysis of agricultural products.

Nanozyme based on CoFe2O4 modified with MoS2 for colorimetric determination of cysteine and glutathione.

A nanozyme based on CoFe2O4 modified with MoS2 was constructed for colorimetric determination of cysteine (Cys) and glutathione (GSH). Firstly, ferrite CoFe2O4 is synthesized, and it is then modified by MoS2 to form a flower-like polymer (MoS2@CoFe2O4). In the presence of H2O2, a redox interaction takes place, and the resulting hydroxyl promoted a colorimetric conversion from colorless to blue in the presence of 3,3',5,5'-tetramethylbenzidine (TMB). However, once Cys or GSH is added, they are capable to compete with the interaction of the hydroxyl with TMB, resulting in an inhibition of the colorimetric conversion. The colorimetric distinction is sensitive to the amount of target. The results obtained proved that the catalytic efficiency of MoS2@CoFe2O4 is 4.4-fold and 1.8-fold to that of MoS2 and CoFe2O4. Meanwhile, the Km values to TMB and H2O2 are 0.067 and 0.048 mM, respectively, which are 6.5-fold and 77-fold, respectively smaller than those of natural peroxidase such as HPR. This indicates that the MoS2@CoFe2O4 possesses a favorable interaction affinity. Additionally, the colorimetric distinction caused by the competition between TMB and cysteine or glutathione is obvious. The signal responses to cysteine and glutathione are linear in the range 0.5~15 µM and 0.5~35 µM, and the LODs are 0.10 and 0.21 µM, respectively. In practical assay of Cys in serum, the RSD of the sample tests is 4.6%, and the recoveries for the spiked assays are 95.3% and 96.0% with the RSD of 2.1% and 4.2%, respectively.

A ratiometric fluorescence probe based on graphene quantum dots and o-phenylenediamine for highly sensitive detection of acetylcholinesterase activity.

By using graphene quantum dots (GQDs) and o-phenylenediamine (OPD), a ratiometric fluorescence probe was designed for the highly sensitive and selective detection of AChE. GQDs with strong fluorescence were synthesized by the one-step hydrothermal method. The optimal emission wavelength of GQDs was 450 nm at the excitation wavelength of 375 nm. MnO2 nanosheets with a wide absorption band of 300-600 nm were prepared at room temperature. Because of the extensive overlap between the absorption spectrum of MnO2 nanosheets and the excitation and emission spectra of GQDs, the fluorescence of GQDs at 450 nm was efficiently quenched by the inner-filter effect. Meanwhile, due to the peroxidase-like activity of MnO2 nanosheets, OPD was catalytically oxidized to 2,3-diaminophenazine (oxOPD), a yellow fluorescent substance with a new emission peak at 572 nm. When AChE was present, the substrate acetylthiocholine (ATCh) was hydrolyzed to thiocholine (TCh) that is capable of decomposing MnO2 nanosheets. Therefore, the quench of GQDs and the oxidation of OPD by MnO2 nanosheets were suppressed, resulting in the fluorescence recovery of GQDs at 450 nm, while the fluorescence decrease of oxOPD at 572 nm. Utilizing the fluorescence intensity ratio F450/F572 as the signal readout, the ratiometric fluorescence method was established to detect AChE activity. The ratio F450/F572 against the AChE concentration demonstrated two linear relationships in the range 0.1-2.0 and 2.0-4.5 mU mL-1 with a detection limit of 0.09 mU mL-1. The method was applied to the detection of positive human serum samples and the analysis of the inhibitor neostigmine. Due to the advantages of high sensitivity, favorable selectivity, and strong anti-interference, the method possesses an application prospect in clinical diagnosis of AChE and the screening of inhibitors. Graphical abstract Schematic presentation of a ratiometric fluorescence method for the detection of acetylcholinesterase (AChE). The fluorescence of graphene quantum dots (GQDs) is quenched and o-phenylenediamine (OPD) is oxidized to generate fluorescent product 2,3-diaminophenazine (oxOPD) by MnO2 nanosheets. When AChE is present, acetylthiocholine iodide (ATCh) is hydrolyzed to thiocholine (TCh) with reducibility for decomposing MnO2 nanosheets. Due to the decomposition of MnO2 nanosheets, the quenching of GQDs and oxidation of OPD are suppressed. The fluorescence of GQDs at 450 nm is enhanced, while the fluorescence of oxOPD at 572 nm is reduced. The fluorescence intensity ratio F450/F572 is used to establish the ratiometric fluorescence method for AChE activity.

Silicon nanoparticles synthesized using a microwave method and used as a label-free fluorescent probe for detection of VB12.

A simple and rapid detection strategy for vitamin B12 (VB12 ) was established based on label-free silicon quantum dots (SiQDs); the detection mechanism was additionally investigated. SiQDs were synthesized using a one-step microwave method, and their fluorescence was stronger than that synthesized using the hydrothermal method. SiQDs fluorescence was quenched using VB12 due to the inner filter effect (IFE), which was demonstrated using ultraviolet (UV) absorption spectra, fluorescence lifetime, transmission electron microscopy and zeta potential analysis. Subsequently, quercetin (Que) and doxorubicin (Dox) with absorption peaks that overlapped the excitation or emission peaks of SiQDs respectively were used as control groups to investigate the quenching mechanism. Results showed that quenching efficiency was related to the level of overlap between the adsorption peak of the quencher and the excitation or emission peaks of SiQDs. A greater level of overlap caused a higher quenching efficiency. Therefore, the sensitive quenching of VB12 for SiQDs was due to the synergistic effect of the synchronous overlap between the absorption peak of VB12 with the excitation and emission peaks of SiQDs. Fluorescence quenching efficiency increased linearly in the 0.5 to 16.0 µmol·L-1 VB12 concentration range, and the detection limit was 158 nmol·L-1 . In addition, SiQDs were applied to determine VB12 in tablets and human urine samples with satisfactory recoveries ranging from 97.7 to 101.1%.

A novel signal amplification strategy based on the use of copper nanoclusters for ratiometric fluorimetric determination of o-phenylenediamine.

Copper nanoclusters (CuNCs) were synthesized starting from glutathione and copper(II) nitrate. They show blue fluorescence peaking at 432 nm when excited at 334 nm. In the presence of o-phenylenediamine (OPD), the blue fluorescence is decreased, but a yellow fluorescence appears with a peak at 557 nm. UV-visible absorptiometry, fluorometry and fluorescence lifetime measurements were used to show that OPD is oxidized by the small fraction of copper(II) ions present in the CuNCs to form the oxidized form of o-phenylenediamine (oxOPD) which displays weak yellow fluorescence, while the blue fluorescence decreases. The ratio of fluorescences at 557 and 432 nm increases linearly in the 0.15 to 110 µg·L-1 OPD concentration range, and the detection limit is 93 ng·L-1. Compared to the method based on the use of dissolved Cu(II), the employment of CuNCs reduces the detection limit by a factor of 40. The method was applied to the determination of OPD in spiked environmental water and industrial wastewater samples. Recoveries ranged from 96.8 to 100.3%. Graphical abstract Schematic presentation of a ratiometric fluorometric method for detection of o-phenylenediamine (OPD) based on copper nanoclusters (CuNCs). OPD is oxidized by Cu2+ present in CuNCs to form the oxidized form of o-phenylenediamine (oxOPD). FRET occurred between oxOPD and CuNCs, and the F557/F432 value is amplified.

Europium(III) modified silicone nanoparticles for ultrasensitive visual determination of tetracyclines by employing a fluorescence color switch.

Silicon nanoparticles (SiNPs) modified with Eu(III) were synthesized and are shown to be a viable ratiometric fluorescent probe for tetracycline antibiotics. SiNPs/Eu under 405 nm excitation display two emissions, viz. a strong cyan colored fluorescence peaking at 497 nm and a weak pink fluorescence peaking at 622 nm. On addition of tetracyclines (chlortetracycline, tetracycline, doxycycline), the fluorescence at 497 nm is reduced, while the one at 622 nm is increased. Thus, the visible color of fluorescence changes from cyan to pink. This was exploited to design ratiometric fluorometric method for detecting tetracyclines. The method has a limit of detection that is lower by a factor of about 1000 when compared to the use of SiNPs only. A test paper was prepared with the SiNPs/Eu and then applied for the visual semi-quantitative detection of tetracyclines. With the addition of tetracyclines, the test paper exhibited a dosage-sensitive color conversion from cyan to pink with a visually discernible scale as low as 0.4 µM. Graphical abstract Tetracyclines decrease the fluorescence at 497 nm of europium (III) modified silicon nanoparticles (SiNPs/Eu) due to the inner filter effect and increase the one at 622 nm due to an antenna effect. Thus the fluorescence color of SiNPs/Eu changes from cyan to pink. Based on this color switch, a ultrasensitive and visual determination strategy for tetracyclines is proposed.

A multifunctional probe based on the use of labeled aptamer and magnetic nanoparticles for fluorometric determination of adenosine 5'-triphosphate.

A multifunctional fluorescent probe is synthesized for the determination of adenosine 5'-triphosphate (ATP). The 6-carboxyfluorescein-labeled aptamer (FAM-aptamer) was bound to the surface of magnetite nanoparticles coated with polydopamine (Fe3O4@PDA) by π-π stacking interaction to form the multifunctional probe. The probe has three functions including recognition, magnetic separation, and yielding a fluorescent signal. In the presence of ATP, FAM-aptamer on the surface of the probe binds to ATP and returns to the solution. Thus, the fluorescence of the supernatant is enhanced and can be related to the concentration of ATP. Fluorescence intensities were measured at excitation/emission wavelengths of 494/526 nm. Response is linear in the 0.1-100 µM ATP concentration range, and the detection limit is 89 nM. The probe was applied to the quantitation of ATP in spiked human urine and serum samples, with recoveries ranging between 94.8 and 102%. Graphical abstract A multifunctional fluorescent probe based on the use of FAM-aptamer and Fe3O4@PDA is described for the determination of ATP in spiked human urine and serum samples. FAM-aptamer: 6-carboxyfluorescein-labeled aptamer; Fe3O4@PDA: magnetite nanoparticles coated with polydopamine. ATP: adenosine 5'-triphosphate.

Tunable and Nontoxic Fluorescent Probes Based on Carbon Dots for Imaging of Indole Propionic Acid Receptor in Plant Tissues in Situ.

Indole propionic acid (IPA) is one of the important plant growth hormones for promoting rooting and fruiting. Labeling IPA receptor in plant tissues is able to further track the signal transduction processes of IPA and uncover the function mechanism of IPA on crop productions. In this paper, a tunable and nontoxic fluorescent probe for IPA receptors was designed and synthetized base on carbon dots (C dots). Firstly carboxyl-modified carbon dots were prepared by high temperature cracking of citric acid. The fluorescence emission wavelengths of C dots varied with the excitation wavelengths change. Then IPA-modified carbon dots (IPA-C dots) were prepared by coupling the amino of tryptophan with the carboxyl of as-prepared carbon dots. Compared with C dots, the fluorescence intensity of IPA-C dots was double and the fluorescence stability was satisfactory under various conditions. This probe retained the biological activity of IPA and acted as target recognition of IPA receptors in plant tissues. The probe could avoid green fluorescence background of plants. The imaging results showed that the IPA receptors mainly existed on the membrane of stele. The toxicity test indicated the probe was less toxic than traditional inorganic semiconductor quantum dots.

In situ detection of salicylic acid binding sites in plant tissues.

The determination of hormone-binding sites in plants is essential in understanding the mechanisms behind hormone function. Salicylic acid (SA) is an important plant hormone that regulates responses to biotic and abiotic stresses. In order to label SA-binding sites in plant tissues, a quantum dots (QDs) probe functionalized with a SA moiety was successfully synthesized by coupling CdSe QDs capped with 3-mercaptopropionic acid (MPA) to 4-amino-2-hydroxybenzoic acid (PAS), using 1-ethyl-3-(3-dimethyllaminopropyl) carbodiimide (EDC) as the coupling agent. The probe was then characterized by dynamic light scattering and transmission electron microscopy, as well as UV/vis and fluorescence spectrophotometry. The results confirmed the successful conjugation of PAS to CdSe QDs and revealed that the conjugates maintained the properties of the original QDs, with small core diameters and adequate dispersal in solution. The PAS-CdSe QDs were used to detect SA-binding sites in mung bean and Arabidopsis thaliana seedlings in vitro and in vivo. The PAS-CdSe QDs were effectively transported into plant tissues and specifically bound to SA receptors in vivo. In addition, the effects of the PAS-CdSe QDs on cytosolic Ca(2+) levels in the tips of A. thaliana seedlings were investigated. Both SA and PAS-CdSe QDs had similar effects on the trend in cytosolic-free Ca(2+) concentrations, suggesting that the PAS-CdSe QDs maintained the bioactivity of SA. To summarize, PAS-CdSe QDs have high potential as a fluorescent probe for the in vitro/in vivo labeling and imaging of SA receptors in plants.

Effects of compound Anoectochilus roxburghii (Wall.) Lindl. oral liquid on relative metabolic enzymes and various biochemical indices in Wistar rats with isoniazid-induced liver injury.

Isoniazid (INH) is the first-line anti-tuberculosis drug in clinical practice, and its main adverse effect is drug-induced liver injury (DILI). This study aimed to investigate the hepatoprotective effect of Compound Anoectochilus roxburghii (Wall.) Lindl. Oral Liquid (CAROL) and to provide a new strategy for the search of potential drugs against INH-induced liver injury in Wistar rats. Animal experiment was based on INH (100 mg/kg) induced liver injury to explore the intervention effects of CAROL at doses of 1.35, 2.70, and 5.40 mL/kg. LC-QTOF-MS/MS was used to identify hepatoprotective components in CAROL and its' exposed components in rat serum. The hepatoprotective effect of CAROL was evaluated by pathological observation of rat liver tissue and changes in levels of biochemical indices and cytokines in serum or liver tissue. Of the 58 hepatoprotective components identified, 15 were detected in the serum of rats with liver-injured treated by high-dose CAROL. Results of animal experiments showed that the levels of various biochemical indexes and cytokines were significantly reversed with CAROL intervention. In particular, the expression level of cytokeratin-18 and high-mobility group box 1, as specific and sensitive indicators of DILI, was significantly reduced in the serum of rats with CAROL intervention compared with the INH model group. The same reversal was observed in the levels of TBIL, ALP, ALT, and AST in serum, as well as in the levels of TNF-α, IL-6, SOD, and MDA in liver tissue. For INH-metabolizing enzymes, an evident expression inhibition was observed in N-acetyltransferase 2 and glutathione S-transferases with CAROL intervention, which may be the key to controlling INH hepatotoxicity. CAROL has a favorable hepatoprotective effect on INH-induced liver injury. This study takes the first step in studying the hepatoprotective mechanism of CAROL against INH hepatotoxicity and provides reference for wider clinical applications.

Self-assembly of hyperbranched DNA network structure for signal amplification detection of miRNA.

Catalytic hairpin assembly (CHA) and hybridization chain reaction (HCR) can achieve the high sensitivity and rapid reaction rate in detecting miRNA. However, the amplification efficiency by these methods are limited. Herein, an enzyme-free and label-free hyperbranched DNA network structure (HDNS) was designed, in which localized catalytic hairpin assembly (LCHA) and hybridization chain reaction occurred in the horizontal axis and longitudinal axis, respectively, exhibiting intensive signal dual-amplification. miRNA-122 was selected as the target on behalf of miRNA to design the HDNS sensor. The fluorescence signal change of HDNS showed good linearity for detecting miRNA-122 in the concentration range from 0.1 nM to 60 nM with a limit of detection (LOD) at 37 pM which was lower than those of the sensors based on separate CHA or HCR. Afterwards, the HDNS sensor was applied to detect miRNA-122 in serum samples with the recovery rate in the range of 97.2 %-107 %. The sensor could distinguish different kinds of miRNAs, even the family members with high sequence homology, exhibiting excellent selectivity. This method provided a novel design strategy for improving the sensitivity and selectivity of DNA sensor for miRNA detection.

Phosphorus Modulated Peroxidase-Like Activity of Carbon Dots for Colorimetric Detection of Acid Phosphatase.

The precise regulation of nanoenzyme activity is of great significance for application to biosensing analysis. Herein, the peroxidase-like activity of carbon dots was effectively modulated by doping phosphorus, which was successfully employed for sensitive, selective detection of acid phosphatase (ACP). Phosphorus-doped carbon dots (P-CDs) with excellent peroxidase-like activity were synthesized by a one-pot hydrothermal method, and the catalytic activity could be easily modulated by controlling the additional amount of precursor phytic acid. P-CDs could effectively catalyze the oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) to blue TMB oxidation products in the presence of hydrogen peroxide. While ACP was able to catalyze the hydrolysis of L-ascorbyl-2-phosphate trisodium salt (AAP) to produce ascorbic acid (AA), which inhibited the peroxidase-like activity of P-CDs, by combining P-CDs nanoenzymes and ACP-catalyzed hydrolysis the colorimetric method was established for ACP detection. The absorbance variation showed a good linear relationship with ACP concentration in the range of 0.4-4.0 mU/mL with a limit of detection at 0.12 mU/mL. In addition, the method was successfully applied to detect ACP in human serum samples with recoveries in the range of 98.7-101.6%. The work provides an effective strategy for regulating nanoenzymes activity and a low-cost detection technique for ACP.

Multihydrogen Bond Modulated Polyzwitterionic Removable Adhesive Hydrogel with Antibacterial and Hemostatic Function for Wound Healing.

Wound management is a major challenge worldwide, placing a huge financial burden on the government of every nation. Wound dressings that can protect wounds, accelerate healing, prevent infection, and avoid secondary damage continue to be a major focus of research in the health care and clinical communities. Herein, a novel zwitterionic polymer (LST) hydrogel incorporated with [2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide (SBMA), mussel-inspired N-[tris(hydroxymethyl)methyl] acrylamide (THMA), and lithium magnesium salt was prepared for functional wound dressings. The incorporation of the THMA monomer containing three hydroxyl groups gives the hydrogel suitable adhesion properties (∼6.0 KPa). This allows the LST zwitterionic hydrogels to bind well to the skin, which not only protects the wound and ensures its therapeutic efficacy but also allows for painless removal and reduced patient pain. Zwitterionic sulfobetaine units of SBMA provide antimicrobial and mechanical properties. The chemical structure and microscopic morphology of LST zwitterionic hydrogels were systematically studied, along with their swelling ratio, adhesion, and mechanical properties. The results showed that the LST zwitterionic hydrogels had a uniform and compact porous structure with the highest swelling and mechanical strain of 1607% and 1068.74%, respectively. The antibacterial rate of LST zwitterionic hydrogels was as high as 99.49%, and the hemostatic effect was about 1.5 times that of the commercial gelatin hemostatic sponges group. In further studies, a full-thickness mouse skin model was selected to evaluate the wound healing performance. Wounds covered by LST zwitterionic hydrogels had a complete epithelial reformation and new connective tissue, and its vascular regenerative capacity was increased to about 2.4 times that of the commercial group, and the wound could completely heal within 12-13 days. This study provides significant advances in the design and construction of multifunctional zwitterionic hydrogel adhesives and wound dressings.

Enzyme activity termination by titanium carbide nanosheet and its application for the detection of deoxyribonuclease I.

Deoxyribonuclease I (DNase I) is a typical nuclease that plays key roles in many physiological processes and the development of a novel biosensing strategy for DNase I detection is of fundamental significance. In this study, a fluorescence biosensing nanoplatform based on a two-dimensional (2D) titanium carbide (Ti3C2) nanosheet for sensitive and specific detection of DNase I was reported. Fluorophore-labeled single-stranded DNA (ssDNA) can be spontaneously and selectively adsorbed on Ti3C2 nanosheet through the hydrogen bond and metal chelate interaction between phosphate groups of ssDNA and titanium of Ti3C2 nanosheet, resulting in effective quenching of the fluorescence emitted by fluorophore. Notably, it was found the enzyme activity of DNase I will be terminated by the Ti3C2 nanosheet. Therefore, the fluorophore-labeled ssDNA was firstly digested by DNase I and the "post-mixing" strategy of Ti3C2 nanosheet was chosen to evaluate the enzyme activity of DNase I, which provided the possibility of improving the accuracy of the biosensing method. Experimental results demonstrated that this method can be utilized for quantitative analysis of DNase I activity and exhibited a low detection limit of 0.16 U/ml. Additionally, the evaluation of DNase I activity in human serum samples and the screening of inhibitors with this developed biosensing strategy were successfully realized, implying that it has high potential as a promising nanoplatform for nuclease analysis in bioanalytical and biomedical fields.

An "ON-OFF" fluorescent sensor based on a novel zinc-based flower-like structured metal-organic framework for sequential detection of deferasirox and tigecycline.

Deferasirox (DEF) is essential for patients with thalassemia requiring long-term transfusion therapy. Tigecycline (TIGE) is a first-line drug for the clinical treatment of complex, severe bacterial infections. The two drugs can be coordinated to treat Pseudomonas aeruginosa infections. Easy and efficient techniques for monitoring these two drugs in biological samples are few. Metal-organic framework (Zn-MOF) prepared from zinc nitrate hexahydrate and dithioglycolic acid has a flower structure. Interestingly, Zn-MOF can cause DEF to aggregate on it and induce DEF luminescence. The principle may be that Zn-MOF limits the vibration and rotation of DEF to avoid its nonradiative jump, which triggers aggregation-induced emission (AIE) and exhibits intense fluorescence. Further investigation revealed that TIGE could decompose Zn-MOF, thus alleviating the inhibitory effect of Zn-MOF on DEF and reducing the fluorescence intensity of DEF@Zn-MOF. A DEF/TIGE detection biosensor was created based on the fluorescence "turn-on" effect of Zn-MOF on DEF and the fluorescence "turn-off" effect of TIGE on DEF@Zn-MOF. The proposed technique was subsequently used to identify DEF/TIGE levels in pharmaceuticals and human plasma. The mean values for the percentage of the labeled amount of DEF/TIGE in DEF dispersible tablets/TIGE injection were 104.5 and 104.9%, respectively. The detection limits for the fluorescence detection of DEF and TIGE were 3.6 and 1.2 nM, respectively. This fluorescence assay is the first application of MOF to the simultaneous detection of DEF and TIGE and has the advantages of rapid sensitivity and high selectivity, providing a new strategy for drug detection.