Study of the radiofrequency-induced heating inside the human head with dental implants at 7 T.

Conductive dental implants are commonly used in restorative therapy to replace missing teeth in patients. Ensuring the radiofrequency (RF) safety of these patients is crucial when performing 7 T magnetic resonance scans of their heads. This study aimed to investigate RF-induced heating inside the human head with dental implants at 7 T. Dental implants and their attachments were fabricated and integrated into an anatomical head model, creating different measurement configurations (MCs). Numerical simulations were conducted using a 7 T transmit coil loaded with the anatomical head model, both with and without dental implants. The maximum temperatures inside the head for various MCs were computed using the maximum permissible input powers (MPIPs) obtained without dental implants and compared with published limits. Additionally, the MPIPs with dental implants were calculated for scenarios where the temperature limits were exceeded. The maximum temperatures observed inside the head ranged from 38.4°C to 39.6°C. The MPIPs in the presence of dental implants were 81.9%-97.3% of the MPIPs in the absence of dental implants for scenarios that exceeded the regulatory limit. RF-induced heating effect of the dental implants was not significant. The safe scanning condition in terms of RF exposure was achievable for patients with dental implants. For patients with conductive dental implants of unknown configuration, it is recommended to reduce the input power by 18.1% of MPIP without dental implants to ensure RF safety.

A smartphone sensing platform for the sensitive and selective detection of clothianidin based on MIP-functionalized lanthanide MOF.

A novel molecularly imprinted nanomaterial (Eu (BTC)-MPS@MIP) was synthesized on the surface of silanized europium-based metal-organic frameworks (Eu (BTC)-MPS) using 1, 3, 5-benzotrioic acid (H3BTC) as a ligand. The resulting Eu (BTC)-MPS@MIP was applied to constructing a smartphone sensing platform for the sensitive and selective detection of clothianidin (CLT) in vegetables. The synthesized Eu (BTC)-MPS@MIP demonstrated the successful formation of a typical core-shell structure featuring a shell thickness of approximately 70 - 80 nm. The developed sensing platform based on Eu (BTC)-MPS@MIP exhibited sensitivity in CLT detection with a detection limit of 4 µg/L and a linear response in the range 0.01 - 10 mg/L at excitation and emission wavelengths of 365 nm and 617 nm, respectively. The fluorescence sensing platform displayed excellent specificity for CLT detection, as evidenced by a high imprinting factor of 3.1. This specificity is primarily attributed to the recognition sites in the molecularly imprinted polymer (MIP) layer. When applied to spiked vegetable samples, the recovery of CLT ranged from 78.9 to 102.0%, with relative standard deviation (RSD) values falling between 2.2 and 6.2%. The quenching mechanism of Eu (BTC)-MPS@MIP toward CLT can be attributed to the inner filter effect (IFE), resulting from the optimal spectral overlap between the absorption spectrum of CLT and the excitation spectra of Eu (BTC)-MPS@MIP. The proposed method has the potential for extension to the detection of other pesticides by replacing the MIP recognition probes.

A novel fluorescent biosensor based on affinity-enhanced aptamer-peptide conjugate for sensitive detection of lead(II) in aquatic products.

Lead contamination is a major concern in food safety and, as such, many lead detection methods have been developed, especially aptamer-based biosensors. However, the sensitivity and environmental tolerance of these sensors require improvement. A combination of different types of recognition elements is an effective way to improve the detection sensitivity and environmental tolerance of biosensors. Here, we provide a novel recognition element, an aptamer-peptide conjugate (APC), to achieve enhanced affinity of Pb2+. The APC was synthesized from Pb2+ aptamers and peptides through clicking chemistry. The binding performance and environmental tolerance of APC with Pb2+ was studied through isothermal titration calorimetry (ITC); the binding constant (Ka) was 1.76*106 M-1, indicating that the APC's affinity was increased by 62.96% and 802.56% compared with the aptamers and peptides, respectively. Besides, APC demonstrated better anti-interference (K+) than aptamer and peptide. Through the molecular dynamics (MD) simulation, we found that more binding sites and stronger binding energy between APC with Pb2+are the reasons for higher affinity between APC with Pb2+. Finally, a carboxyfluorescein (FAM)-labeled APC fluorescent probe was synthesized and a fluorescent detection method for Pb2+ was established. The limit of detection of the FAM-APC probe was calculated to be 12.45 nM. This detection method was also applied to the swimming crab and showed great potential in real food matrix detection.

Low-cost, portable, on-site fluorescent detection of As(III) by a paper-based microfluidic device based on aptamer and smartphone imaging.

A turn-on fluorescent aptasensor based on a paper-based microfluidic chip was developed to detect arsenite via aptamer competition strategy and smartphone imaging. The chip was prepared by wax-printing hydrophilic channels on filter paper. It is portable, low-cost, and environmentally friendly. Double-stranded DNA consisting of aptamer and fluorescence-labeled complementary strands was immobilized on the reaction zone of the paper chip. Due to the specific strong binding between aptamer and arsenite, the fluorescent complementary strand was squeezed out and driven by capillary force to the detection area of the paper chip, so that the fluorescent signal arose in the detection area under the excitation wavelength of 488 nm. Arsenite can be quantified by using smartphone imaging and RGB image analysis. Under the optimal conditions, the paper-based microfluidic aptasensor exhibited excellent linear response over a wide range of 1 to 1000 nM, with a detection limit as low as 0.96 nM (3σ).

A Novel Fluorescent Aptasensor for Arsenic(III) Detection Based on a Triple-Helix Molecular Switch.

A novel aptamer-based fluorescent-sensing platform with a triple-helix molecular switch (THMS) was proposed as a switch for detecting the arsenic(III) ion. The triple helix structure was prepared by binding a signal transduction probe and arsenic aptamer. Additionally, the signal transduction probe labeled with fluorophore (FAM) and quencher (BHQ1) was employed as a signal indicator. The proposed aptasensor is rapid, simple and sensitive, with a limit of detection of 69.95 nM. The decrease in peak fluorescence intensity shows a linear dependence, with the concentration of As(III) in the range of 0.1 µM to 2.5 µM. The whole detection process takes 30 min. Moreover, the THMS-based aptasensor was also successfully used to detect As(III) in a real sample of Huangpu River water with good recoveries. The aptamer-based THMS also presents distinct advantages in stability and selectivity. The proposed strategy developed herein can be extensively applied in the field of food inspection.

Enhanced ion transport in nanochannels of MXenes by Mg2+ pre-intercalation.

How to enhance the ion transport between MXene layers is a critical topic in the fields of electrochemical storage (especially supercapacitors) and water treatment. Vertical structure design of MXene nanosheets and single-molecule organic pre-intercalation are proposed, but the methods to enhance the ion transport through MXene nanochannels by modulating MXene's surface state have not been investigated yet. The interaction mechanism between Mg2+ and MXene 2D nanochannels during the transport process has not been thoroughly explored. In our work, we used a facile infiltration method to immerse the Ti3C2Tx membranes in MgCl2 solution for ion pre-intercalation. We found that the pre-intercalation of Mg2+ has a significant effect on the increase of the ion transport rate of Ti3C2Tx membranes, especially for Li+ which reached 268.49% compared with those of non-intercalation membranes. Through multiple characterization methods, we discovered that the enhancement of ion transport rate by pre-intercalation of Mg2+ mainly originated from the fact that the pre-intercalation of Mg2+ increased the layer spacing of MXene films as the channel support between layers while Mg2+ increased the work function (WF) of 2D nanochannels thereby reducing the interaction of other ions with the channel surface. The acceleration phenomenon of ion transport by surface state modulation proposed in our work will provide new strategies for the design of structure and regulation of surface states, revealing the mechanism of capacity improvement.

An aptasensor for the detection of Pb2+ based on photoinduced electron transfer between a G-quadruplex-hemin complex and a fluorophore.

Due to the threat to health of heavy metal contamination, simple and rapid detection methods for heavy metals are an urgent needed in environment protection and food safety. In this work, we have developed a fluorescent aptasensor for the 'turn-off' model detection of Pb2+ . The key feature of the aptasensor is that the dye-labelled nucleic acid strand can be folded into a G-quadruplex structure in the presence of Pb2+ . This conformational change induces photoinduced electron transfer (PET) between a G-quadruplex-hemin complex and 6-carboxyrhodamine X (ROX), which results in fluorescence quenching of ROX. We systematically investigated the interaction mechanism between Pb2+ and the aptasensor and the effects of several environmental parameters were also studied. Under the optimum conditions, the proposed method exhibited a good liner relationship between the concentration of Pb2+ and fluorescence quenching efficiency in the range 25-500 nM and the limit of detection was 1.02 nM. In addition, this method also manifested good performance in spiked lettuce samples with satisfactory recoveries of 87.10-109.6%. This target-induced PET platform can be further expanded to other heavy metal analysis.

Spherical nucleic acids with tailored DNA conformation via bromide backfilling for the detection of kanamycin.

The improper conformation of oligonucleotides on gold nanoparticle surfaces is caused by unintended base adsorption, which hinders DNA hybridization and lowers colloidal stability. In this work, we treated spherical nucleic acids with Br- , which serves as an efficient backfilling agent, to adjust the DNA conformation by displacing bases from the gold surface. To investigate the effect of DNA conformation on interfacial recognition, a kanamycin fluorescent aptasensor was constructed with bromide backfilled-treated spherical nucleic acids. In the presence of kanamycin, the anchored aptamer binds with the target and the partially complementary reporter strand is dissociated from the surface of the gold nanoparticles, resulting in the fluorescence recovery of labelled fluorophore on the reporter strand. Under optimum conditions, the apparent binding affinity of the aptasensor with bromide backfilling was 2.2-fold that without backfilled one. The proposed aptasensor exhibited a good liner relationship between the concentration of kanamycin and fluorescence intensity change in the range 200 nM to 10 µM and the limit of detection was calculated to be 71.53 nM. Moreover, this aptasensor was also successfully applied in a spiked milk sample assay and the satisfactory recoveries were obtained in the range 96.94-101.57%, which demonstrated its potential in practical applications.

Poly-adenine-mediated spherical nucleic acids for interfacial recognition of kanamycin.

Kanamycin fluorescence aptasensors were created using a series of di-block oligonucleotide modified gold nanoparticles with various lengths of poly-adenine. In the presence of kanamycin, the double strand structure of the aptamer-reporter strand complex is disrupted, and the dye-labelled reporter strand detaches from the surface of gold nanoparticles, resulting in fluorescence recovery (Ex/Em = 485/520 nm). By adjusting the number of consecutive adenines, the programable aptamer density can be implemented on the gold nanoparticle surface, and the conformation of nucleic acid changed from lying-down to up-right. The apparent binding constant, binding kinetics, and limit of detection of the prepared aptasensors were carefully examined to explore the influence of surface density. Under the optimum condition, the aptasensor had a tenfold lower limit of detection than the thiolated aptamer modified one, as low as 23.6 nM, when a di-block oligonucleotide with twenty consecutive adenines tailed. In addition, satisfactory recoveries ranging from 96.33 to 99.47% were achieved in spiked milk samples with relative standard deviation of 1.2-6.9% (n = 3). This surface density regulation strategy holds great promise in other aptamer-based interfacial recognition and sensing. Schematic presentation of di-block oligonucleotide modified gold nanoparticle with different surface densities and its kanamycin sensing application.

A Novel Aptamer-Imprinted Polymer-Based Electrochemical Biosensor for the Detection of Lead in Aquatic Products.

Lead contamination in aquatic products is one of the main hazard factors. The aptasensor is a promising detection method for lead ion (Pb(II)) because of its selectivity, but it is easily affected by pH. The combination of ion-imprinted polymers(IIP) with aptamers may improve their stability in different pH conditions. This paper developed a novel electrochemical biosensor for Pb(II) detection by using aptamer-imprinted polymer as a recognition element. The glassy carbon electrode was modified with gold nanoparticles and aptamers. After the aptamer was induced by Pb(II) to form a G-quadruplex conformation, a chitosan-graphene oxide was electrodeposited and cross-linked with glutaraldehyde to form an imprint layer, improving the stability of the biosensor. Under the optimal experimental conditions, the current signal change (∆I) showed a linear correlation of the content of Pb(II) in the range of 0.1-2.0 µg/mL with a detection limit of 0.0796 µg/mL (S/N = 3). The biosensor also exhibited high selectivity for the determination of Pb(II) in the presence of other interfering metal ion. At the same time, the stability of the imprinted layer made the sensor applicable to the detection environment with a pH of 6.4-8.0. Moreover, the sensor was successfully applied to the detection of Pb(II) in mantis shrimp.

Mechanisms of photoreactivity in hydrogen-bonded adenine-H2O complexes.

The mechanisms of photoinduced reactions of adenine with water molecules in hydrogen-bonded adenine-water complexes were investigated with ab initio wave-function-based electronic-structure calculations. Two excited-state electron/proton transfer reaction mechanisms have been characterized: H-atom abstraction from water by photoexcited adenine as well as H-atom transfer from photoexcited adenine or the (adenine+H) radical to water. In the water-to-adenine H-atom transfer reaction, an electron from one of the p orbitals of the water molecule fills the hole in the n (π) orbital of the nπ* (ππ*) excited state of adenine, resulting in a charge-separated electronic state. The electronic charge separation is neutralized by the transfer of a proton from the water molecule to adenine, resulting in the (adenine+H)OH biradical in the electronic ground state. In the adenine-to-water H-atom transfer reaction, πσ* states localized at the acidic sites of adenine provide the mechanism for the photoejection of an electron from adenine, which is followed by proton transfer to the hydrogen-bonded water molecule, resulting in the (adenine-H)H3O biradical. The energy profiles of the photoreactions have been computed as relaxed scans with the ADC(2) electronic-structure method. These reactions, which involve the reactivity of adenine with hydrogen-bonded water molecules, compete with the well-established intrinsic excited-state deactivation mechanisms of adenine via ring-puckering or ring-opening conical intersections. By providing additional decay channels, the electron/proton exchange reactions with water can account for the observed significantly shortened excited-state lifetime of adenine in aqueous environments. These findings indicate that adenine possibly was not only a photostabilizer at the beginning of life, but also a primordial photocatalyst for water splitting.

Evaluation of fixed-jaw IMRT and tangential partial-VMAT radiotherapy plans for synchronous bilateral breast cancer irradiation based on a dosimetric study.

PURPOSE: To investigate the fixed-jaw intensity-modulated radiotherapy (F-IMRT) and tangential partial volumetric modulated arc therapy (tP-VMAT) treatment plans for synchronous bilateral breast cancer (SBBC). MATERIALS AND METHOD: Twelve SBBC patients with pTis-2N0M0 stages who underwent whole-breast irradiation after breast-conserving surgery were planned with F-IMRT and tP-VMAT techniques prescribing 42.56 Gy (2.66 Gy*16f) to the breast. The F-IMRT used 8-12 jaw-fixed tangential fields with single (sF-IMRT) or two (F-IMRT) isocenters located under the sternum or in the center of the left and right planning target volumes (PTVs), and tP-VMAT used 4 tangential partial arcs with two isocenters located in the center of the left and right PTVs. Plan evaluation was based on dose-volume histogram (DVH) analysis. Dosimetric parameters were calculated to evaluate plan quality; total monitor units (MUs), and the gamma analysis for patient-specific quality assurance (QA) were also evaluated. RESULTS: For PTVs, the three plans had similar Dmean and conformity index (CI) values. F-IMRT showed a slightly better target coverage according to the V100% values and demonstrated an obvious reduction in V105% and Dmax compared with the values observed for sF-IMRT and tP-VMAT. Compared with tP-VMAT, sF-IMRT was slightly better in terms of V100% , V105% and Dmax . In addition, F-IMRT achieved the best homogeneity index (HI) values for PTVs. Concerning healthy tissue, tP-VMAT had an advantage in minimizing the high dose volume. The MUs of the tP-VMAT plan were decreased approximately 1.45 and 1 times compared with the sF-IMRT and F-IMRT plans, respectively, and all plans passed QA. For the lungs, heart and liver, F-IMRT achieved the smallest values in terms of Dmean and showed a significant difference compared with tP-VMAT. Simultaneously, sF-IMRT was also superior to tP-VMAT. For the coronary artery, tP-VMAT achieved the lowest Dmean , while the value for F-IMRT was 2.24% lower compared with sF-IMRT. For all organs at risk (OARs), tP-VMAT was superior at the high dose level. In contrast, sF-IMRT and F-IMRT were obviously superior at the low dose level. The sF-IMRT and F-IMRT plans showed consistent trends. CONCLUSION: All treatment plans for the provided techniques were of high quality and feasible for SBBC patients. However, we recommend F-IMRT with a single isocenter as a priority technique because of the tremendous advantage of local hot spot control in PTVs and the reduced dose to OARs at low dose levels. When the irradiated dose to the lungs and heart exceed the clinical restriction, two isocenter F-IMRT can be used to maximize OAR sparing. Additionally, tP-VMAT can be adopted for improving cold spots in PTVs or high-dose exposure to normal tissue when the interval between PTVs is narrow.

Role of Electron-Driven Proton-Transfer Processes in the Ultrafast Deactivation of Photoexcited Anionic 8-oxoGuanine-Adenine and 8-oxoGuanine-Cytosine Base Pairs.

It has been reported that 8-oxo-7,8-dihydro-guanosine (8-oxo-G), which is the main product of oxidative damage of DNA, can repair cyclobutane pyrimidine dimer (CPD) lesions when incorporated into DNA or RNA strands in proximity to such lesions. It has therefore been suggested that the 8-oxo-G nucleoside may have been a primordial precursor of present-day flavins in DNA or RNA repair. Because the electron transfer leading to the splitting of a thymine-thymine pair in a CPD lesion occurs in the photoexcited state, a reasonably long excited-state lifetime of 8-oxo-G is required. The neutral (protonated) form of 8-oxo-G exhibits a very short (sub-picosecond) intrinsic excited-state lifetime which is unfavorable for repair. It has therefore been argued that the anionic (deprotonated) form of 8-oxo-G, which exhibits a much longer excited-state lifetime, is more likely to be a suitable cofactor for DNA repair. Herein, we have investigated the exited-state quenching mechanisms in the hydrogen-bonded complexes of deprotonated 8-oxo-G- with adenine (A) and cytosine (C) using ab initio wave-function-based electronic-structure calculations. The calculated reaction paths and potential-energy profiles reveal the existence of barrierless electron-driven inter-base proton-transfer reactions which lead to low-lying S1/S0 conical intersections. The latter can promote ultrafast excited-state deactivation of the anionic base pairs. While the isolated deprotonated 8-oxo-G- nucleoside may have been an efficient primordial repair cofactor, the excited states of the 8-oxo-G--A and 8-oxo-G--C base pairs are likely too short-lived to be efficient electron-transfer repair agents.

Excited-State Deactivation of Adenine by Electron-Driven Proton-Transfer Reactions in Adenine-Water Clusters: A†Computational Study.

The reactivity of photoexcited 9H-adenine with hydrogen-bonded water molecules in the 9H-adenine-(H2 O)5 cluster is investigated by using ab initio electronic structure methods, focusing on the photoreactivity of the three basic sites of 9H-adenine. The energy profiles of excited-state reaction paths for electron/proton transfer from water to adenine are computed. For two of the three sites, a barrierless or nearly barrierless reaction path towards a low-lying S1 -S0 conical intersection is found. This reaction mechanism, which is specific for adenine in an aqueous environment, can explain the substantially shortened excited-state lifetime of 9H-adenine in water. Depending on the branching ratio of the nonadiabatic dynamics at the S1 -S0 conical intersection, the electron/proton transfer process can enhance the photostability of 9H-adenine in water or can lead to the generation of adenine-H(⋅) and OH(⋅) free radicals. Although the branching ratio is yet unknown, these findings indicate that adenine might have served as a catalyst for energy harvesting by water splitting in the early stages of the evolution of life.

Excess electron reactivity in amino acid aqueous solution revealed by ab initio molecular dynamics simulation: anion-centered localization and anion-relayed electron transfer dissociation.

Studies on the structure, states, and reactivity of excess electrons (EEs) in biological media are of great significance. Although there is information about EE interaction with desolvated biological molecules, solution effects are hardly explored. In this work, we present an ab initio molecular dynamics simulation study on the interaction and reactivity of an EE with glycine in solution. Our simulations reveal two striking results. Firstly, a pre-solvated EE partially localizes on the negatively charged -COO(-) group of the zwitterionic glycine and the remaining part delocalizes over solvent water molecules, forming an anion-centered quasi-localized structure, due to relative alignment of the lowest unoccupied molecular orbital energy levels of potential sites for EE residence in the aqueous solution. Secondly, after a period of anion-centered localization of an EE, the zwitterionic glycine is induced to spontaneously fragment through the cleavage of the N-Cα bond, losing ammonia (deamination), and leaving a ˙CH2-COO(-) anion radical, in good agreement with experimental observations. Introduction of the same groups (-COO(-) or -NH3(+)) in the side chain (taking lysine and aspartic acid as examples) can affect EE localization, with the fragmentation of the backbone part of these amino acids dependent on the properties of the side chain groups. These findings provide insights into EE interaction mechanisms with the backbone parts of amino acids and low energy EE induced fragmentation of amino acids and even peptides and proteins.

Characterization of stipe elongation of the mushroom Coprinopsis cinerea.

Previously, we observed an acid-induced short-term wall extension in Flammulina velutipes apical stipes during a 15 min period after a change from a neutral to an acidic pH. This acid-induced stipe wall extension was eliminated by heating and reconstituted by a snail expansin-like protein, although we failed to isolate any endogenous expansin-like protein from F. velutipes because of its limited 1 mm fast elongation region. In this study, we report that Coprinopsis cinerea stipes possess a 9 mm fast elongation apical region, which is suitable as a model material for wall extension studies. The elongating apical stipe showed two phases of acid-induced wall extension, an initial quick short-term wall extension during the first 15 min and a slower, gradually decaying long-term wall extension over the subsequent 2 h. After heating or protein inactivation pretreatment, apical stipes lost the long-term wall extension, retaining a slower short-term wall extension, which was reconstituted by an expansin-like snail protein. In contrast, the non-elongating basal stipes showed only a weaker short-term wall extension. We propose that the long-term wall extension is a protein-mediated process involved in stipe elongation, whereas the short-term wall extension is a non-protein mediated process not involved in stipe elongation.

Study on the affinity sites of cadmium's binding to ligands by thermodynamics and nuclear magnetic resonance spectroscopy.

The affinity sites of cadmium (Cd(II)) when binding to cysteine (Cys) and glutathione (GSH) were studied via thermodynamics and nuclear magnetic resonance (NMR) spectroscopy methods. The results showed that the Cd(II) binding sites of Cys and GSH were -SH (exothermic), -NH2 (endothermic) and -COOH (endothermic). The thermodynamic behaviour of Cd(II) binding to Cys/GSH in boric acid and HEPES buffers differed, with the former being mainly endothermic and the latter mainly exothermic. It could be inferred that, in the boric acid system, the main binding site of Cd(II) with Cys and GSH is changed from -SH in HEPES to -COOH and -NH2 in boric acid. This was confirmed by the results of NMR experiments of Cd(II) with Cys/GSH. 1D 1H-NMR experiments showed that, after the combination of Cd(II) and Cys, the changes in the chemical shifts and peak strengths of protons near the -SH group for the reaction in HEPES were greater than when boric acid buffer was used. Changes in the chemical shift and peak strength of the -NH2 protons due to the binding of Cd(II) to GSH were evident in the boric acid buffer but not in HEPES. The screening of functional monomers is very important in the process of preparation of cadmium ion-imprinted materials. This research provides important theoretical and experimental guidance for the screening of functional monomers.

Whole grain germinated brown rice intake modulates the gut microbiota and alleviates hypertriglyceridemia and hypercholesterolemia in high fat diet-fed mice.

Hyperlipidemia is a common clinical disorder of lipid metabolism in modern society and is considered to be one of the major risk factors leading to cardiovascular-related diseases. Germinated brown rice (GBR) is a typical whole grain food. The lipid-lowering effect of GBR has received increasing attention, but its mechanism of action is not fully understood. The gut microbiota has been proposed as a novel target for the treatment of hyperlipidemia. The aim of this study was to investigate the effects of GBR on the gut microbiota and lipid metabolism in high-fat diet (HFD)-fed C57BL/6J mice. The effect of GBR on hyperlipidemia was evaluated by measuring blood lipid levels and by pathological examination. The gut microbiota was detected by 16S rRNA sequencing, and the protein and mRNA expression levels involved in cholesterol metabolism were detected by western blotting and RT-qPCR to find potential correlations. The results showed that GBR supplementation could effectively reduce the levels of TC, TG, LDL-C and HDL-C in the serum and alleviate the excessive accumulation of fat droplets caused by HFD. Moreover, GBR intervention improved HFD-fed gut microbiota disorder via increasing the diversity of the gut microbiota, reducing the Firmicutes/Bacteroidetes ratio, and improving gut barrier damage. In addition, GBR could inhibit endogenous cholesterol synthesis and promote cholesterol transport and excretion. These findings suggest that GBR may be a competitive candidate for the development of functional foods to prevent abnormal lipid metabolism.

A trivalent aptasensor by using DNA tetrahedron as scaffold for label-free determination of antibiotics.

Owing to advantage in high sensitivity and fast response, aptamer based electrochemical biosensors have attracted much more attention. However, inappropriate interfacial engineering strategy leads to poor recognition performance, which ascribe to the following factors of immobilized oligonucleotide strand including steric hindrance, interchain entanglement, and unfavorable conformation. In this work, we proposed a DNA tetrahedron based diblock aptamer immobilized strategy for the construction of label-free electrochemical biosensor. The diblock aptamer sequence is composite of T-rich anchor domain and recognition domain, where T-rich domain enabling anchored on the edge of DNA tetrahedron via Hoogsteen hydrogen bond at neutral condition. The DNA tetrahedron scaffold offers an appropriate lateral space for target recognition of diblock aptamer. More importantly, this trivalent aptamer recognition interface can be regenerated by simply adjusting the pH environment to alkaline, resulting in the dissociation of diblock aptamer. Under the optimum condition, proposed electrochemical aptasensor manifested a satisfied sensitivity for aminoglycosides antibiotic, kanamycin with a limit of detection of 0.69 nM, which is 45-fold lower than traditional Au-S immobilization strategy. Moreover, the proposed aptasensor had also successfully been extended to ampicillin detection by changing the sequence of recognition domain in diblock aptamer. This work paves a new way for the rational design of aptamer-based electrochemical sensor.

A colorimetric and fluorescent dual-mode sensor based on bifunctional G-quadruplex-hemin complex for the determination of Pb2.

Due to the threat of lead pollution to health, environmental and food safety, developing simple and fast detection methods is highly required. Whereas, traditional single-mode probe suffers from limited application scenario. In this study, a colorimetric and fluorometric dual-mode probe for Pb2+ determination was constructed by using bifunctional G-quadruplex-hemin complex. In this dual-mode probe, enzyme strand and substrate strand of 8-17 DNAzyme are labeled with G-quadruplex-hemin complex and fluorophore, respectively. In the absence of Pb2+, the self-assembly of enzyme strand and substrate strand inhibits intrinsic mimic peroxidase of G-quadruplex-hemin complex by base-pairing, which also quench the fluorescence via in proximity effect. When the DNAzyme is activated by Pb2+, the quenched fluorescence is restored as well as the inherent peroxidase mimetic activity, leading to dual signal output. Under optimal conditions, this dual-mode probe exhibit a good linear relationship between logarithm of Pb2+ concentration and signal difference within the range from 1.5 nM to 20 nM and 0.5 nM to 10 nM for colorimetric and fluorescence mode, respectively. The detection limits for the corresponding mode were estimated to be 1.29 nM and 0.16 nM, respectively. This dual-mode probe also successfully applied for the spiked river water assay with satisfactory recovery in the range of 93.2 %-115.3 %. This work paves a new way for DNAzyme based dual-mode probe construction.