Graphite/Gold Nanoparticles Electrode for Direct Protein Attachment: Characterization and Gas Sensing Application

In this work, graphite/gold nanoparticles (G/AuNPs) were synthesized through a facile chemical method, and its potential application for direct protein attachment for electrochemical detection of carbon monoxide (CO) was investigated. The preparation of G/AuNPs electrodes was optimized by synthesizing the nanoparticles in different concentration of HAuCl4.3H2O at various temperatures. The G/AuNPs electrode was subsequently modified by four types of mercaptopropionic acid, including 1-mercaptopropionic, 3-mercaptopropionic, 6-mercaptopropionic, and 11-mercaptopropionic acid, to achieve the best structure for protein attachment. Visible absorption and electrochemical studies showed that 3-mercaptopropionic acid possesses the best performance regarding the electrical conductivity between electrode and protein redox center. The cyclic voltammetry results revealed that the modified electrode has an appropriate performance for CO detection at very low concentrations while keeping a linear response. The limit of detection for the modified electrode was calculated to be about 0.2 ppb. Finally, the interactions of cytochrome C and carbon monoxides were simulated using molecular dynamics (MD), and the effect of protein conformation changes on the electrochemical signal was thoroughly examined. The simulation results suggested that the proposed electrochemical sensor has an acceptable performance for the detection of CO due to less fluctuation of amino acids near the protein chain in the presence of CO molecules

A Glassy Carbon Electrode Modified with Reduced Graphene Oxide and Gold Nanoparticles for Electrochemical Aptasensing Of Lipopolysaccharides from Escherichia Coli Bacteria

An electrochemical aptasensor is described for the voltammetric determination of lipopolysaccharide (LPS) from Escherichia coli 055:B5. Aptamer chains were immobilized on the surface of a glassy carbon electrode (GCE) via reduced graphene oxide and gold nanoparticles (RGO/AuNPs). Fast Fourier transform infrared, X-ray diffraction and transmission electron microscopy were used to characterize the nanomaterials. Cyclic voltammetry, square wave voltammetry and electrochemical impedance spectroscopy were used to characterize the modified GCE. The results show that the modified electrode has a good selectivity for LPS over other biomolecules. The hexacyanoferrate redox system, typically operated at around 0.3 V (vs. Ag/AgCl) is used as an electrochemical probe. The detection limit is 30 fg·mL−1. To decrease the electrochemical potential for detection of LPS, Mg/ carbon quantum dots were used as redox active media. They decrease the detection potentialto 0 V and the detection of limit (LOD) to 1 fg·mL−1. The electrode was successfully used to analyze serum of patients and healthy persons

Layer-By-Layer Assembly of Graphene Oxide on Thermosensitive Liposomes for Photo-Chemotherapy

Stimuli responsive polyelectrolyte nanoparticles have been developed for chemo-photothermal destruction of breast cancer cells. This novel system, called layer by layer Lipo-graph (LBL Lipo-graph), is composed of alternate layers of graphene oxide (GO) and graphene oxide conjugated poly (l-lysine) (GO-PLL) deposited on cationic liposomesencapsulating doxorubicin. Various concentrations of GO and GO-PLL were examined and the optimal LBL Lipo-graph was found to have a particle size of 267.9 ± 13 nm, zeta potentialof +43.9 ± 6.9 mV and encapsulation efficiency of 86.4 ± 4.7%. The morphology of LBL Lipo-graph was examined by cryogenic-transmission electron microscopy (Cryo-TEM), atomic force microcopy (AFM) and scanning electron microscopy (SEM). The buildup of LBL Lipo-graph was confirmed via ultraviolet-visible (UV–Vis) spectrophotometry, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis. Infra-red (IR) response suggests that four layers are sufficient to induce a gel-to-liquid phase transition in response to near infra-red (NIR) laser irradiation. Light-matter interaction of LBL Lipo-graph was studied by calculating the absorption cross section in the frequency domain by utilizing Fourier analysis. Drug release assay indicates that the LBL Lipo-graph releases much faster in an acidic environment than a liposome control. A cytotoxicity assay was conducted to prove the efficacy of LBL Lipo-graph to destroy MD-MB-231 cells in response to NIR laser emission. Also, image stream flow cytometry and two photon microcopy provide supportive data for the potential application of LBL Lipo-graph for photothermal therapy. Study results suggest the novel dual-sensitive nanoparticles allow intracellular doxorubin delivery and respond to either acidic environments or NIR excitation. Statement of Significance Stimuli sensitive hybrid nanoparticles have been synthesized using a layer-by-layer technique and demonstrated for dual chemo-photothermal destruction of breast cancer cells. The hybrid nanoparticles are composed of alternating layers of graphene oxide and graphene oxide conjugated poly-l-lysine coating the surface of a thermosensitive cationic liposome containing doxorubicin as a core. Data suggests that the hybrid nanoparticles may offer many advantages for chemo-photothermal therapy. Advantages include a decrease of the initial burst release which may result in the reduction in systemic toxicity, increase in pH responsivity around the tumor environment and improved NIR light absorption

Maximum Flow Interdiction Problem in Multi-Period Dynamic Networks in Fuzzy Stochastic Hybrid Conditions

Undoubtedly, the best tool to help military decision-makers and commanders choose the appropriate strategy is to formulate models that are as close to the real world as possible. This is possible when these problems are presented in conditions of uncertainty. In this research, a multi-period dynamic interdiction problem in fuzzy stochastic conditions is investigated. In general, interdiction problem, scarce resources are allocated to degrade the enemy, whose behavior is formatted by the network optimization problem. In this problem, the defense forces in the role of interdictor try to minimize the maximum flow during the period so that at each stage the interdictor and the enemy are fully aware of the performance of the other side. Edge capacities in this model are considered as fuzzy stochastic variables. To solve the proposed model, first, the fuzzy stochastic dynamic interdiction problem is transformed into the deterministic dynamic interdiction problem with the help of the concepts of probability measure, credibility measure and chance constraint programming. Then, by creating the crisp two-level problem created by duality, it is transformed into a single-level problem, and then it is solved by using the generalization of Banders decomposition algorithm. Finally, the validity of the problem is evaluated by providing a numerical sample

Case report: Endovascular treatment of transplant renal artery stenosis in patient with normal color duplex ultrasound of the renal artery

Key Clinical Message Proper diagnosis and treatment of vascular stenosis which is a possible complication of renal transplant is important in improving patients' quality of life and prognosis. Abstract One known consequence among recipients of renal transplants is graft renal artery stenosis. Early identification and therapy are crucial to avoid graft malfunction and the serious consequences that might arise due to elevated hypertension in several organs. We report a rare case of transplant renal artery stenosis in a mid‐aged woman who presented with edema, hypertension, and increased creatinine 2 months after kidney transplant. The patient had normal renal arterial resistive index (RI) and perfusion index (PI), and there was only a modest decrease in perfusion on duplex ultrasound. Following the patient's renal stenting treatment, angiographic resolution was observed. After 14 days of regulated blood pressure following renal artery stenting, she was discharged from the hospital with her edema resolved. Considering complications in patients with clinical manifestations such as hypertension resistant to treatment and graft dysfunction, vascular stenosis is a notable issue to consider even in the context of normal renal arterial RI, PI, and duplex ultrasound. Proper diagnosis and treatment are of importance to improve patients' quality of life and prognosis

Synergistic Effects of Conductive PVA/PEDOT Electrospun Scaffolds and Electrical Stimulation for More Effective Neural Tissue Engineering

Fabrication and optimization of conductive scaffolds capable of inducing proper intercellular connections through electrical signals is critical for neural tissue engineering. In this research, electrospun conductive PVA (Polyvinyl alcohol)/PEDOT(poly(3,4-ethylenedioxythiophene)) scaffolds were fabricated in different compositions. Conductivity of electrospinning solutions and electrospun scaffolds were measured. Morphology and topography, mechanical properties and water contact angle of scaffolds were analyzed. Chemistry of scaffolds were studied using FTIR analysis, while biocompatibility and cellular interactions with scaffolds were tested using MTT assay and cellular attachment and spreading testing. Our results show improvements in PEDOT-containing scaffolds, in terms of physiochemical properties, and cell viability compared to pure PVA scaffolds. After optimization of scaffolds, real-time PCR analysis was used to study neural differentiation of rat mesenchymal stem cells (MSCs). Scaffold samples with and without induction of electrical stimulation are shown to upregulate β-tubulin, nestin and enolase as compared to TCP samples. Additionally, expression of nestin gene in scaffold samples with electrical stimulation was 1.5 times more significant than scaffold sample. Overall, this study shows that using PVA/PEDOT conductive scaffolds with electrical stimulation can improve cellular response and neural differentiation through mimicking the properties of native neural tissue