A simple and sensitive electrochemical biosensor for circulating tumor cell determination based on dual-toehold accelerated catalytic hairpin assembly.

Tumor cells in blood circulation (CTCs) are vital biomarkers for noninvasive cancer diagnosis. We developed a simple and sensitive electrochemical biosensor based on dual-toehold accelerated catalytic hairpin assembly (DCHA) to distinguish CTCs from blood cells. In the presence of CTCs, the aptamer probe initiates the DCHA process, which produces amplified electrochemical signals. Compared with conventional catalytic hairpin assembly (CHA), the proposed DCHA showed high sensitivity, which led to a broader working range of 10-1000 cells mL-1 with a limit of detection of 4 cells mL-1. Furthermore, our method exhibited an excellent capability of distinguishing malignant breast cancers from healthy people, with a sensitivity of 97.4%. In summary, we have established an enzyme-free, easy-to-operate, and nondisruptive method for detecting circulating tumor cells in blood circulation based on the DCHA strategy. Its versatility and simplicity will make it more widely used in clinical diagnosis and biomedical research.

Ultrasound-assisted extraction of tamarind xyloglucan: an effective approach to reduce the viscosity and improve the α-amylase inhibition of xyloglucan.

BACKGROUND: Water extraction (WE) is the classical extraction method for tamarind xyloglucan (XyG), but its low yield, high viscosity and poor dispersion in aqueous solution are not conducive to the industrial applications. To promote the industrial application of tamarind XyG, an ultrasonic-assisted extraction (UAE) method for extracting low-viscosity XyG from tamarind kernel powder was proposed. RESULTS: The yield of UAE-XyG was higher (502.33 ± 0.036 g kg-1 ) than that of WE-XyG (163.43 ± 0.085 g kg-1 ). UAE reduced the molecular weight, monosaccharide content and apparent viscosity of XyG. The hypoglycemic experiment in vitro showed that UAE-XyG had a stronger inhibitory effect on α-amylase activity than WE-XyG, but its glucose dialysis retardation index was lower. CONCLUSION: In sum, UAE is a type of extraction method that could effectively improve the yield of XyG and reduce its viscosity to expand its application without reducing its physiological activity. UAE exhibits an excellent potential in the extraction of XyG. © 2022 Society of Chemical Industry.

Revealing the Intrinsic Nature of the Synergistic Effect Caused by the Formation of Heterojunctions in Cu-Cu2O/rGO-NH2 Nanomaterials in the Catalysis of Selective Aerobic Oxidation of Benzyl Alcohol.

Ternary nanomaterials Cu-Cu2O/rGO-NH2 (rGO = reduced graphene oxide) exhibited a synergistic effect in the quantitative catalysis of selective aerobic oxidation of benzyl alcohol. The synergistic effect is attributed to the heterojunctions among the three components and in intrinsic nature, the formation of the heterojunctions lowered the conduction band (CB) energy level and raised the valence band (VB) energy level of the main catalyst Cu2O, which eases electron transfer from the catalyst to O2 in its activation and from the substrate to the catalyst in the oxidation, respectively.

Coherently enhanced third-harmonic generation in cascaded microfibers.

A scheme using cascaded silica microfibers is proposed for efficient third-harmonic (TH) generation. By tuning the phase difference via input pump power, the TH from the microfibers could overlap coherently, yielding great output enhancement. Conversion efficiency ∼20% is demonstrated analytically and numerically. Moreover, as the TH output features are dominated by behavior analogous to optical interference, the influence of random diameter deviation of each microfiber is reduced, and the conversion process could be well controlled.

A fluorescent immunosensor for determination and imaging of circulating tumor cells based on a bifunctional DNA nanomachine.

A fluorescent platform was developed for the determination and visualization of circulating tumor cells by a toehold-mediated bifunctional DNA nanomachine. In the presence of target tumor cells, the DNA nanomachine was activated. Multiple DNA products were formed, including dendritic DNA products and double-strand DNA products. Dendritic DNA products bound to their target cells for the visualization, while double-strand DNA products were released for the determination of tumor cells. At fluorescence excitation and emission wavelengths of 530 and 550 nm, this method could detect as low as 43 cells/mL (S/N = 3) with a linear range of 100 to 10,000 cells/mL. In clinical hydrothorax samples, this platform exhibited high reliability with a recovery of 93 to 116%. At the fluorescence excitation and emission wavelengths of 490 and 515 nm, the specificity and biocompatibility of this method were further verified by tumor cells imaging. Furthermore, the robustness of the toehold-mediated bifunctional DNA nanomachine was demonstrated by the specific gene mutation detection in single-cell analysis. Graphical abstract Schematic illustration of the fluorescent immunosensor for determination and imaging of circulating tumor cells. The method is based on aptamer-based recognition and toehold-mediated bifunctional DNA nanomachine.

Enhanced UV third-harmonic generation in microfibers by controlling nonlinear phase modulations.

The influence of nonlinear phase modulations on third-harmonic (TH) conversion in silica microfibers is experimentally demonstrated. By utilizing such influence, enhanced narrow-bandwidth ultraviolet TH is generated at a high signal-to-noise ratio (33 dB) and an average power of several hundred nanowatts. Detailed trends of TH power against input pump power were characterized with peak pump power up to 2.5 kW, and the results agree with predicted features, confirming that harmonic output could be optimized with adaptive control of the phase mismatch.

Optimized microfiber-based third-harmonic generation with adaptive control of phase mismatch.

An effective approach is presented to improve intermodal third-harmonic generation in microfibers. It is demonstrated that structure-independent incident pump power could be utilized, via its effect on nonlinear phase modulations, to compensate for the phase mismatch caused by diameter deviation. The output harmonic of a fabricated microfiber can be optimized adaptively; thus, efficient third-harmonic generation with efficiency reaching several percent could realistically be achieved.

Arabinoxylan activates lipid catabolism and alleviates liver damage in rats induced by high-fat diet.

BACKGROUND: Arabinoxylan was thought to have the potential to change lipid metabolism and redox homeostasis in human and animal. However, the effect of arabinoxylan on the liver damage induced by high-fat diet needs further exploiting. RESULTS: Six-weeks-old 30 male Sprague-Dawley Rats were assigned randomly to three groups (n = 10 per group), i.e. a control diet (CON) group, a high-fat diet (HF) group and a high-fat diet supplemented with arabinoxylan (6% AX, HF-AX) group. Results showed that final body weight and liver weight were similar in CON group and HF-AX group, but higher in the HF group. In serum, the HF-AX group showed lower triglyceride concentrations than did the HF group. In liver, higher lipoprotein lipase, hepatic lipase, total lipase, and acyl-CoA oxidase activities and lower triglyceride and cholesterol level were observed in the HF-AX group than in the HF group. For the redox homeostasis, arabinoxylan supplemented in HF increased T-SOD activity and GSH-PX activity and reduced MDA + 4-HNE level in liver and/or compared with those in the HF group. Lipid droplets and liver cell damage were observed in the HF group compared with the CON and HF-AX groups. CONCLUSION: Arabinoxylan could improve lipid metabolic disorder and alleviate liver damage in rats induced by high-fat diet via activating lipid catabolism and suppressing lipid peroxidation. © 2017 Society of Chemical Industry.

Fundamental-mode third harmonic generation in microfibers by pulse-induced quasi-phase matching.

A scheme to enhance the fundamental-mode third harmonic generation efficiency in microfibers is presented. By introducing an appropriate counter-propagating pulse train, large propagation constant mismatch is partly overcome and nonlinear phase shifts could be corrected for, thus quasi-phase matching between the fundamental pump mode and the fundamental third harmonic mode is achieved, enabling the harmonic power to grow along the direction of propagation. Depending on the microfiber and pulse parameters, phase matching can enhance the conversion efficiency by several orders of magnitude with respect to the non-phase matched case. This scheme offers an alternative approach for harmonic generation and could potentially be applied to other small core waveguides.

Sterigmatocystin-induced checkpoint adaptation depends on Chk1 in immortalized human gastric epithelial cells in vitro.

Sterigmatocystin (ST) is a common contaminant detected in food and animal feed that has been recognized as a possible human carcinogen. Our previous studies demonstrate that ST causes DNA damage and subsequently triggers cell cycle arrest in G2 and apoptosis in immortalized human gastric epithelial cells (GES-1). Recently, studies have shown that in certain contexts, cells with DNA damage may escape checkpoint arrest and enter mitosis without repairing the damage. The term for this process is "checkpoint adaptation," and it increases the risk of unstable genome propagation, which may contribute to carcinogenesis. Thus, we aimed to investigate whether checkpoint adaptation occurs in GES-1 cells treated with ST and explored the underlying molecular mechanisms that contribute to this phenotype. In this study, we found that ST treatment for 24 h in GES-1 cells led to an initial G2 arrest; however, a fraction of GES-1 cells became large and rounded, and the number of p-H3-positive cells increased sharply after ST treatment for 48 h. Moreover, collection of the large and rounded cells by mechanical shake-off revealed that the majority of these large cells were found in the mitotic phase of the cell cycle. Importantly, we found that these rounded cells entered mitosis despite damaged DNA and that a small subset of this cell population survived and continued to propagate. These results suggest that ST induces an initial G2 arrest that is subsequently followed by G2 phase checkpoint adaptation, which may potentially promote genomic instability and result in tumorigenesis. Furthermore, we showed that activation of Chk1 contributes to the G2 arrest in GES-1 cells that are treated with ST for 24 h and that prolonged treatment of cells with ST for 48 h led to a decrease in the total protein and phosphorylation levels of Chk1 in mitotic cells, indicating that checkpoint adaptation may be driven by inactivation of Chk1. Knockdown studies confirmed that cells entered mitosis following inactivation of Chk1. Taken together, we show that ST treatment for 24 h activates Chk1 and induces a G2 arrest in GES-1 cells. However, prolonged ST treatment for 48 h led to Chk1 inactivation in GES-1 cells, which promotes checkpoint adaptation and entry of cells into mitosis despite damaged DNA. Importantly, checkpoint adaptation in GES-1 cells treated with ST may potentially promote genomic instability and drive tumorigenesis.

Photoinduced Carbon Monoxide Release from Half-Sandwich Iron(II) Carbonyl Complexes by Visible Irradiation: Kinetic Analysis and Mechanistic Investigation.

Three half-sandwich iron(II) complexes, [Fe(η(5) -Cp)(cis-CO)2 X] (X(-) =Cl(-) , Br(-) , I(-) ), were synthesized and characterized. The kinetics of the CO-releasing behaviour of these complexes upon illumination by visible irradiation in various media was investigated. Our results indicated that the CO release was significantly affected by the auxiliary ligands. Of the three light sources used (blue, green, and red), blue light exhibited the highest efficiency. In the photoinduced CO release, the solvents and exogenous nucleophiles in the media were involved, which allowed their CO-releasing reaction to comply with pseudo first-order model rather than the characteristic zero-order model for a photochemical reaction. In aqueous media (D2 O), an intermediate bearing the core of {Fe(II) (cis-CO)2 } involving cleavage of cyclopentadiene was detected. Despite the non-absorption of the red light, its illumination combined with nucleophilic substitution did cause considerable CO release. Assessment of the cytotoxicity of the three complexes indicated that they showed good biocompatibility.

Sterigmatocystin induces G1 arrest in primary human esophageal epithelial cells but induces G2 arrest in immortalized cells: key mechanistic differences in these two models.

Sterigmatocystin (ST), a mycotoxin commonly found in food and feed commodities, has been classified as a "possible human carcinogen." Our previous studies suggested that ST exposure might be a risk factor for esophageal cancer and that ST may induce DNA damage and G2 phase arrest in immortalized human esophageal epithelial cells (Het-1A). To further confirm and explore the cellular responses of ST in human esophageal epithelia, we comparatively evaluated DNA damage, cell cycle distribution and the relative mechanisms in primary cultured human esophageal epithelial cells (EPC), which represent a more representative model of the in vivo state, and Het-1A cells. In this study, we found that ST could induce DNA damage in both EPC and Het-1A cells but led to G1 phase arrest in EPC cells and G2 phase arrest in Het-1A cells. Furthermore, our results indicated that the activation of the ATM-Chk2 pathway was involved in ST-induced G1 phase arrest in EPC cells, whereas the p53-p21 pathway activation in ST-induced G2 phase arrest in Het-1A cells. Studies have demonstrated that SV40 large T-antigen (SV40LT) may disturb cell cycle progression by inactivating some of the proteins involved in the G1/S checkpoint. Het-1A is a non-cancerous epithelial cell line immortalized by SV40LT. To evaluate the possible perturbation effect of SV40LT on ST-induced cell cycle disturbance in Het-1A cells, we knocked down SV40LT of Het-1A cells with siRNA and found that under this condition, ST-induced G2 arrest was significantly attenuated, whereas the proportion of cells in the G1 phase was significantly increased. Furthermore, SV40LT-siRNA also inhibited the activation of the p53-p21 signaling pathway induced by ST. In conclusion, our data indicated that ST could induce DNA damage in both primary cultured and immortalized esophageal epithelial cells. In primary human esophageal epithelial cells, ST induced DNA damage and then triggered the ATM-Chk2 pathway, resulting in G1 phase arrest, whereas in SV40LT-immortalized human esophageal epithelial cells, SV40LT-mediated G1 checkpoint inactivation occurred, and ST-DNA damage activated p53-p21 signaling pathway, up-regulating G2/M phase regulatory proteins and finally leading to a G2 phase arrest. Thus, the SV40LT-mediated G1 checkpoint inactivation is responsible for the difference in the cell cycle arrest by ST between immortalized and primary cultured human esophageal epithelial cells.

Localized surface modes in parity-time-symmetric potentials.

We investigate light-beam propagation along the interface between linear and nonlinear media with parity-time symmetry. A novel class of two-dimensional localized surface modes (LSMs) is found analytically and numerically. If the potential is parity-time invariant along the direction parallel to the interface between the two media, stable LSMs can exist. Otherwise, if the potential is parity-time invariant along the direction perpendicular to the interface between the two media, there are no stable LSMs.

A highly sensitive C3-symmetric Schiff-base fluorescent probe for Cd2+.

A new C3-symmetric Schiff-base fluorescent probe (L) based on 8-hydroxy-2-methylquinoline has been developed. As expected, the probe L can display high fluorescent selectivity for Cd(2+) over Zn(2+) and most other common ions in neutral ethanol aqueous medium. Moreover, the mechanism of the L-Cd(2+) complex has been confirmed by X-ray crystallography and density functional theory calculation results. More importantly, L could be used to image Cd(2+) within living cells.

Green one-step synthesis of N-doped carbon quantum dots for fluorescent detection of lemon yellow in soft drinks.

A new fluorescent sensor for the determination of lemon yellow was developed based on nitrogen-doped carbon quantum dots (N-CQDs), which were prepared via a hydrothermal method with dried pomelo peel and L-tyrosine. The N-CQDs exhibited the blue fluorescence with a quantum yield of 28 %. The sensing principle of N-CQDs was quenched by lemon yellow via static quenching. The potential interfering substances showed no influence on the detection of lemon yellow. The limit of detection was 0.023 mg/L and lower than that of national standard. Furthermore, the synthesized N-CQDs have been successfully applied to the measurement of lemon yellow in real samples. Hence, the N-CQDs would be a promising sensor in food analysis.

Performance of target irradiation in a high-power laser with a continuous phase plate and spectral dispersion.

We report on the performance of target irradiation at the SG-II high-power laser facility with a continuous phase plate (CPP) and the technique of smoothing by spectral dispersion (SSD). Simulative and experimental results are presented, where the irradiation uniformity and energy concentration of the target spots are analyzed. The results show that the designed CPP can focus the spot energy into the desired region and shape a profile with steep edge and flat top, but the actual performance of the fabricated CPP needs some improvements. It is also proved that the CPP is insensitive to the long-scale wavefront distortion in the incident beam. The one-dimensional SSD configuration evidently works in smoothing the fine-scale intensity modulation inside the target spot.

catena-Poly[[silver(I)-µ-4,4'-bipyridine-κ(2)N:N'] 4-[2-(4-carb-oxy-phen-yl)-1,1,1,3,3,3-hexa-fluoro-propan-2-yl]benzoate].

Assembly of the flexible dicarb-oxy-lic ligand 4-[2-(4-carboxyphenyl)-1,1,1,3,3,3-hexafluoropropan-2-yl]benzoate and 4,4'-bipyridine as co-ligand with Ag(I) ions resulted in the formation of the polymeric title compound, {[Ag(C(10)H(8)N(2))](C(17)H(9)F(6)O(4))}(n), in which the metal atoms are bridged by the 4,4'-bipyridine ligands, generating cationic chains extending along [010]. The dihedral angles between the benzene rings in the anion and the pyridine rings in the cation are 72.42 (9) and 9.36 (10)°, respectively. The mol-ecular conformation of the anion is stabilized by intra-molecular C-H⋯F hydrogen bonds. In the crystal, the anions inter-act with the cationic chains via C-H⋯O hydrogen bonds, forming layers parallel to (001), in which weak π-π stacking inter-actions [centroid-centroid distances = 3.975 (3)-4.047 (3) Å] involving the pyridine rings of adjacent 4,4'-bipyridine ligands are present. The planes are further assembled into a three-dimensional network by O-H⋯O hydrogen bonds.

Iron(0) tricarbonyl η4-1-azadiene complexes and their catalytic performance in the hydroboration of ketones, aldehydes and aldimines via a non-iron hydride pathway.

Six iron(0) tricarbonyl complexes (1a-f) with a η4-1-azadiene moiety were prepared and their performance in the hydroboration of unsaturated organic compounds was investigated. All the complexes exhibit catalytic activity towards hydroboration of ketones, aldehydes and aldimines with pinacolborane (HBpin) as a hydride source to lead to secondary alcohols, primary alcohols, and secondary amines, respectively, after hydrolysis of the hydroboration products. Of the iron(0) tricarbonyl complexes, complex 1e is the most robust one and was employed throughout the catalytic investigation. Its preference towards the three types of substrates is as follows: aldimines > aldehydes ≫ ketones. In total, 24 substrates were examined for the catalytic hydroboration reactivity and generally, isolation yields ranging from 40% to 95% were achieved. Mechanistic investigation suggests that the catalytic hydroboration of the substrates proceeds via intramolecular hydride transfer without going through an Fe-H intermediate. As indicated by 1H NMR spectroscopic monitoring, the substrates and the borane agent bind to the iron centre and the imine N atom, respectively, which facilitates the hydride transfer by activating the B-H bond and polarizing the double bond of the substrates.

Human-Machine Interaction Methods for Minimally Invasive Surgical Robotic Arms.

Minimally invasive surgery has a smaller incision area than traditional open surgery, which can greatly reduce damage to the human body and improve the utilization of medical devices. However, minimally invasive surgery also has disadvantages such as limited flexibility and operational characteristics. The interactive minimally invasive surgical robot system not only improves the stability, safety, and accuracy of minimally invasive surgery but also introduces force feedback in controlling the surgical robot, which is a new development direction in the field of minimally invasive surgery. This paper reviews the development status of interactive minimally invasive surgical robotic systems and key technologies to achieve human-robot interaction and finally provides an outlook and summary of its development. Fuzzy theory and reinforcement learning are introduced into the parameter adjustment process of the variable guide control model, and a human-robot interaction method for minimally invasive surgical robot posture adjustment is proposed.

Point-of-Care Urinalysis with One Drop of Sample Using an Aggregation-Induced Emission Luminogen under the Coffee-Ring Effect.

Development of a practical point-of-care test for urinalysis is crucial for early diagnosis and treatment of chronic kidney disease (CKD). However, the classical gold standard detection method depends on sophisticated instruments and complicated procedures, impeding them from being utilized in resource-limited settings and daily screening. Herein, we report a rapid point-of-care device for the simultaneous quantification of microalbuminuria and leukocyte using one drop of urine. A luminogen (TTVP) with an aggregation-induced emission property can selectively activate its near-infrared fluorescence in the presence of albumin and leukocyte via hydrophobic or electrostatic interactions. The fluorescence signals from urine albumin and leukocyte could be well-separated combined with the coffee-ring effect. Using a smartphone-based detection device, simultaneous quantification of urine albumin and leukocyte was successfully achieved, which only took 20 min and required one drop of urine. The performance of this system is also verified with 120 clinical samples, which might serve as a simple, low-cost, and rapid tool for CKD screening and disease monitoring at the point of care.