Research Progress in Enzyme Biofuel Cells Modified Using Nanomaterials and Their Implementation as Self-Powered Sensors.

Enzyme biofuel cells (EBFCs) can convert chemical or biochemical energy in fuel into electrical energy, and therefore have received widespread attention. EBFCs have advantages that traditional fuel cells cannot match, such as a wide range of fuel sources, environmental friendliness, and mild reaction conditions. At present, research on EBFCs mainly focuses on two aspects: one is the use of nanomaterials with excellent properties to construct high-performance EBFCs, and the other is self-powered sensors based on EBFCs. This article reviews the applied nanomaterials based on the working principle of EBFCs, analyzes the design ideas of self-powered sensors based on enzyme biofuel cells, and looks forward to their future research directions and application prospects. This article also points out the key properties of nanomaterials in EBFCs, such as electronic conductivity, biocompatibility, and catalytic activity. And the research on EBFCs is classified according to different research goals, such as improving battery efficiency, expanding the fuel range, and achieving self-powered sensors.

DFT Investigation of Hydrogen Atom Abstraction from NHC-Boranes by Methyl, Ethyl and Cyanomethyl Radicals-Composition and Correlation Analysis of Kinetic Barriers.

Understanding the hydrogen atom abstraction (HAA) reactions of N-heterocyclic carbene (NHC)-boranes is essential for extending the practical applications of boron chemistry. In this study, density functional theory (DFT) computations were performed for the HAA reactions of a series of NHC-boranes attacked by •CH2CN, Me• and Et• radicals. Using the computed data, we investigated the correlations of the activation and free energy barriers with their components, including the intrinsic barrier, the thermal contribution of the thermodynamic reaction energy to the kinetic barriers, the activation Gibbs free energy correction and the activation zero-point vibrational energy correction. Furthermore, to describe the dependence of the activation and free energy barriers on the thermodynamic reaction energy or reaction Gibbs free energy, we used a three-variable linear model, which was demonstrated to be more precise than the two-variable Evans-Polanyi linear free energy model and more succinct than the three-variable Marcus-theory-based nonlinear HAA model. The present work provides not only a more thorough understanding of the compositions of the barriers to the HAA reactions of NHC-boranes and the HAA reactivities of the substrates but also fresh insights into the suitability of various models for describing the relationships between the kinetic and thermodynamic physical quantities.

DFT investigation of hydrogen atom-abstraction reactions of NHC-boranes by various carbon-centered radicals: barriers and correlation analyses.

In this study, we employed a quantum-mechanical computational method to investigate the hydrogen-atom abstraction reactions of two nitrogen heterocyclic carbene boranes (NHC-boranes), NHC-BH3 and NHC-BH2CN, by a series of carbon-centered radicals bearing various substituents. We explored the degree of correlation of the activation and free energy barriers to their components. Furthermore, we also investigated the effects of the radical and substituent sizes, nucleophilicity/electrophilicity indices, and the spin density distribution of the radical reactants on the three fundamental barriers and the thermal contribution of the reaction energy to the kinetic barrier. Using the generated data, we assessed the abilities of the various radical reactants to abstract the hydrogen atom from NHC-boranes. Further, we performed a similar analysis after dividing those radical reactants into four groups, which were classified based on the dominant factor affecting their electronic density distribution, which involves the inductive effect, conjugation, hyperconjugation, and the feedback of lone-pair electrons. The results and conclusions of this investigation not only provide insight into the relationships between some of the key kinetic and thermodynamic parameters, which is useful for understanding the dynamics of such hydrogen-abstraction reactions, but also provide information for selecting suitable radical reactants for further experimental investigations.

Does the Neophyl-like Rearrangement Play a Decisive Role in Intramolecular Cyclization of Iminyl Radicals? A Combined Quantum Chemistry and Numerical Simulation Investigation of the Cyclization Mechanism and Product Distributions of Bicyclic 2-Allyl-2-methyl-2,3-dihydro-1 H-inden-1-iminyl Radical and Several Iminyl Model Compounds.

In this study, we performed a theoretical investigation of the intramolecular cyclization of bicyclic 2-allyl-2-methyl-2,3-dihydro-1 H-inden-1-iminyl radical 1 along with several iminyl model compounds. The results were used to comparatively evaluate the reaction mechanism suggested previously, in which the neophyl-like rearrangement was deemed to play a decisive role. The present computation and numerical simulation identify the experimentally observed endo product in the high-temperature cyclization of 1. The product results from a kinetically controlled endo cyclization-reduction pathway involving an initial reversible 5- exo ring-closure/ring-opening process, not via 5- exo cyclization/neophyl-like rearrangement/ endo-radical reduction pathway as proposed previously. Considering many available theoretical and experimental results, the neophyl-like rearrangement seems to play only a minor role in the intramolecular cyclization of N- and C-centered radicals. The structural effect of cyclized radical intermediates of bicyclic 1 leads to a lower thermodynamic reaction energy of exo cyclization than of endo cyclization, which together with the temperature effect should be responsible for the formation of the dominant endo product in the high-temperature region. Additionally, this investigation provided further insight into the cyclization of 1 and compounds structurally similar to 1; that is, control of endo- or exo-regioselective products is readily available by regulating the reaction temperature.

Significance of heparanase in metastatic lymph nodes of cervical squamous cell cancer.

The aim of this study was to explore the expression of heparanase (HPA) in metastatic lymph nodes (LNs) of cervical cancer and to evaluate HPA as a marker of micro-metastasis of LNs. Immunohistochemistry was performed to detect the expression of HPA in 53 cases with metastasis of LNs (group A) and 49 cases without (group B). Scoring was determined based on the intensity of immunostaining and the size of the staining area. Three points or higher score was considered as positive. Among all cases, the positive rate of HPA was 76.5% in primary lesions and 84.9% in both primary lesions and metastatic LNs in group A. In group B, the rates were 67.3% in primary lesions and 8.2% in metastatic LNs. The expression of HPA in group A was significantly higher than that in group B (P<0.05). Compared with stage IA-IB and well-differentiated and non-metastatic LNs, the LNs of stage IIA and moderately/poorly differentiated and metastatic LNs expressed higher HPA (P<0.05). The overall 5-year survival rate was 73.3% and the median overall survival time (MOS) was 49.0 months. The MOS of the two groups was 36.0 and 58.5 months, respectively (P=0.023); the MOS of patients with positive HPA expression was distinctly lower than that of negative patients (P=0.040). Clinical staging, degree of differentiation, lymph node metastasis and expression of HPA notably affected patient prognosis; lymph node metastasis and expression of HPA were independent risk factors affecting patient prognosis (P<0.05). Our study demonstrated that high-level expression of HPA in cervical cancer was involved in LN metastasis, further impacting on patients' long-term survival. The clinical value of HPA requires further in-depth study.

Novel 1, 3-N, O-Spiroheterocyclic compounds inhibit heparanase activity and enhance nedaplatin-induced cytotoxicity in cervical cancer cells.

Heparanase (HPA) is an enzyme that plays an important role in cancer metastasis and angiogenesis and is a potential target for molecular treatment of tumors. We previously found that abnormally high HPA expression in cervical cancer tissues is associated with poor survival and increased lymph node metastasis. The present study was conducted to assess the utility of inhibiting HPA enzyme activity in cervical cancer treatment. Two series of 13 novel HPA inhibitors were synthesized and optimized. All tested inhibitors reduced HPA enzyme activity (IC50 values ranged from 4.47 µM to 47.19 µM) and inhibited the growth of HeLa cells (IC50 values ranged from 48.16 µM to 96.64 µM). The No. 16 inhibitor inhibited the migration and growth of HeLa and Siha cells in a dose- and time-dependent manner, and increased cell apoptosis and cell cycle G0/G1 and G2/M phase arrest, while decreasing the S phase cell population. More importantly, No. 16 sensitized cervical cancer cells to low concentrations of nedaplatin, decreased HPA, c-Myc and h-TERT levels, and increased p53 levels in HeLa and Siha cells. These results suggest that this HPA inhibitor reduced proliferation and HPA expression in cervical cancer cells by restoring p53 activity and downregulating h-TERT and c-Myc expression.

[Effect of 1,3-O,N spiroheterocyclic inhibitors of heparanase on the growth of HeLa cells].

OBJECTIVE: To provide the theoretical supportting for targeted heparanase (HPA) inhibition of cervical cancer through observing the anti-proliferative effect of the HPA inhibitor on HeLa cell line of cervical cancer. METHODS: The two series of 13 kinds of novel HPA inhibitors were synthesized and optimized. Heparan degrading enzyme assay kit was used to test the effect of the inhibitors on the inhibition of HPA enzyme activity. Methyl thiazolyl tetrazolium (MTT) method and scratch test were used to observe the anti-proliferative and the migration effect of the inhibitors on HeLa cells. Flow cytometry was performed to determine the cell cycles and apoptosis. The expression of HPA was evaluated by reverse transcription (RT)-PCR, western blot and immunocytochemistry. RESULTS: All tested inhibitors could inhibit the activity of HPA enzyme [the range of 50% inhibiting concentration (IC50) values from 4.47 to 47.19 µmol/L] and the growth of HeLa cells (the range of IC50 values from 48.16 to 96.64 µmol/L). Among them, No.16 compound exhibits the strongest inhibition against the growth of HeLa, which could arrest the cell into G0/G1 and G2/M phases. The rate of cell apoptosis in the group treated with 50 µmol/L No.16 for 48 hours [(11.9 ± 1.2)%] was significantly higher than that [(6.6 ± 1.8)%] in untreated group (P = 0.013). Real time PCR and western blot showed that expression levels of HPA mRNA (1.23 ± 0.46) and protein (0.46 ± 0.31) significantly decreased in the treated group as compared with the levels of HPA mRNA (3.43 ± 0.45) and protein (1.30 ± 0.58) in the untreated group (both P < 0.05). Immunocytochemistry also showed that the treatment of No.16 significantly reduced the average optical density (0.39 ± 0.04) of HPA immuostaining signal compared with that in the control group (0.50 ± 0.09; P = 0.026). CONCLUSION: Novel 1,3-O,N spiroheterocyclic HPA inhibitors could inhibit the proliferation of HeLa cells, inhibit the HPA enzyme activity in different degree, and downregulate the expression of HPA protein.

Suramin inhibits cell proliferation in ovarian and cervical cancer by downregulating heparanase expression.

BACKGROUND: Aberrant expression of heparanase (Hpa) is associated with apoor prognosis in ovarian and cervical cancer patients. Inhibitors of Hpa can prevent the growth and metastasis of malignant tumor cells, and suramin may be such a compound that has strong anti-proliferative effects on several kinds of cancer cells. We have therefore tested whether the growth inhibiting effect of suramin on ovarian and cervical cancer cells is due to downregulation of Hpa expression. RESULTS: Suramin at 300-600 µg/ml significantly inhibited HO-8910 PM and HeLa cell growth at 24 h, in both a time-dependent and dose-dependent manner, with an IC50 of 320 µg/ml and 475 µg/ml, respectively. Suramin at 300 µg/ml significantly decreased the expression of Hpa mRNA (P < 0.005) and protein (P < 0.005) in both HO-8910 PM and HeLa cells at 48 h. CONCLUSIONS: The inhibitory effect of suramin on Hpa enzyme may be due to downregulating of its expression in cancer cells. These findings confirm the importance of Hpa in tumor growth and the potential clinical application of Hpa inhibitors in the treatment of ovarian and cervical cancer.