Applied Mechanics and Materials Vol. 835

Abstract: Nowadays biosensors have been extensively used in a wide variety of applications especially in clinical works and food industry. In this work, a specific ascorbic acid (AA) biosensor was developed by immobilizing ascorbate oxidase (ASOD) on a polyethylene glycol (PEG) modified silk fibroin (SF) membrane then coupling to the glassy carbon electrode (GCE). The SF-PEG-ASOD membrane provided the highest enzyme activity in phosphate buffer at pH 5. As being the electrode, the SF-PEG-ASOD modified GCE displayed the highest response when it is operated under the condition of 0.40 mg/L of ASOD in phosphate buffer at pH 5. This biosensor provided both good linearity (r² = 0.999 in the range of 1.0-10.0 mM) and sensitivity with short response time (26s). It also exhibited good anti-interference ability with the storage time of 5 days without changing its initial response.

Abstract: Prolonged monitoring is more likely to result in an accurate diagnosis of atrial fibrillation patients than intermittent or short-term monitoring. In this study, we present an implantable ECG sensor to monitor atrial fibrillation patients in real time. The developed implantable sensor is composed of a micro controller unit, analog to digital converter, signal transmitter, antenna, and two electrodes. The sensor detects ECG signals from the two electrodes and transmits these signals to the external receiver that is carried by the patient. The sensor continuously transmits signals, so its battery consumption rate is extremely high. To overcome this problem, we consider using a wireless power transmission module in the sensor module. This module helps the sensor charge power wirelessly without holding the battery in the body. The size of the integrated sensor is approximately 0.12 inch x 1.18 inch x 0.19 inch. This sensor size is appropriate enough for cardiologists to insert the sensor into patients without the need for a major surgery. The data sampling rate was 300 samples/sec, and the frequency was 430 Hz for signal and power transmission. To verify the validation of the developed sensor, the small animal experiments were conducted.

Abstract: This study aimed to synthesize and then characterized the physical property of thiocarbamide (SN) doped TiO₂ thin films performance coated on stainless steel surfaces at low temperature by a rotary evaporator-assisted sol–gel process. The study also investigated the efficiency of this compound to inhibit the growth of Staphylococcus aureus. The films were analyzed using X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray photo electron microscopy (XPS) and inductively couple plasma (ICP). The result of the physical properties showed the smaller size of doped compound crystal (10.3 nm.) than undoped crystal (11.0 nm.) by the x-ray refraction test. The antibacterial activities against Staphylococcus aureus (63%) under UV irradiation showed SN doped TiO₂ nano particulates film enhance bacterial inactivation within 150 minutes. The expected overall properties of nanocomposites may open the way towards new applications of high performance stainless steel, leading to an innovative product development in the hospitals, electronics for coatings and many other applications.

Abstract: Due to rapid growing of nanotechnology, it is currently being used in many areas including biotechnology, electronics, drug delivery systems, cosmetics, material science and biosensors. Oxidative stress is considered as main cause behind the toxicity of nanoparticles (NPs). Recent reports indicate that boron is effective in protecting cells or organisms against oxidative damages by enhancing antioxidant defense mechanisms. However, protective role of boron compounds in nanotoxicity is not investigated yet. Therefore we assessed the potential protective role of boric acid (BA) and borax (BX) against the toxic responses of nano-Fe₃O₄ particles (IO NPs) in cultured human whole blood cells. Our results showed that IO NPs induced genotoxicity in human lymphocytes demonstrated by sister chromatid exchange (SCE) and 8-hydroxy-2′-deoxyguanosine (8-OH-dG) assays. Again, IO NPs caused decreases of total antioxidant capacity (TAC) and decreases of total oxidative stress (TOS) levels in vitro. Co-application of boric acid and borax (2.5 to 10 ppm) into the cell cultures significantly ameliorated genotoxicity and oxidative stress caused by IO NPs. In a conclusion, this study is the first report revealing that BA and BX significantly protected human blood cells from the toxicity of IO NPs, which is mediated through the generation of oxidative stress and depletion of antioxidant capacity.

Abstract: Brittle break downs are typical failures of ceramic materials. Chipping problems associated with all-ceramic zirconia restorations are studied and discussed at the moment. Factorial analysis showed that material and thickness of prosthetic crowns are of primary importance in stress magnitude. Laboratory tests such as finite element analysis (FEA) may help to predict the behaviour of different restorations during biomechanical simulation. The aim of this study was to evaluate by FEA stresses in all-ceramic crowns in regard to different veneer thicknesses. For the experimental analysis a first upper premolar was chosen. A static structural analysis was performed to calculate the stress distribution from different coping designs. FEA may help to predict the behaviour of all-ceramic bilayer crowns during biomechanical simulation. FEA investigations show that a constant veneering thickness of 1-1.8 mm doesn't affect the stress distribution and maximal stress values in the teeth structures and restorations.

Abstract: Zirconia is an extremely successful material for prosthetic restorations, offering attractive mechanical and optical properties. It offers several advantages for posterior restorations because it can withstand physiological posterior forces. The aim of the study was to achieve the influence of zirconia framework thickness on the mechanical behavior of all-ceramic crowns using numerical simulation. For the study a premolar was chosen in order to simulate the mechanical behavior in the components of all-ceramic crowns and teeth structures regarding to the zirconia framework thickness. Maximal Von Mises equivalent stress values were recorded in teeth and restorations. Due to the registered maximal stress values it can be concluded that it is indicated to achieve frameworks of at least 0.5 mm thickness in the premolar area. Regarding stress distribution concentration were observed in the veneer around the contact areas with the antagonists, in the framework under the functional cusp and in the oral part overall and in dentin around and under the marginal line, also oral. The biomechanical behavior of all ceramic crowns under static loads can be investigated by the finite element method.

Abstract: The purpose of this paper is to investigate the preparation of peanut antioxidant peptides by Bacillus subtilis solid state fermentation method and to provide a theoretical basis for further investigating deep processing products of fermentation peanut meal. The preparation technics for peanut antioxidant peptides optimized with the soluble nitrogen concentration of peptides, 1, 1-diphenyl-2-picryl-hydrazyl (DPPH) and hydroxyl free radicals scavenging rates of fermentation broth as the indexes of investigation including the cell age was 20h, bacterial suspension volume was 3.0mL, fermentation temperature was 40°C, nutrient salt solution was 15mL, the fermentation time was 42h, water bath temperature was 45°C, and water bath time was 3h. The research shows that IC₅₀ values for peptides scavenging of DPPH, hydroxyl and superoxide anion free radicals, iron and copper ion chelating rates, lipid peroxidation inhibiting rate, iron and molybdenum reducing activity were 3.48mg/mL, 6.24mg/mL, 2.06mg/mL, 0.54mg/mL, 1.19mg/mL, 4.56mg/mL, 9.58mg/mL and 2.17mg/mL, respectively.

Abstract: In this paper, the binding assay of potential aptamer candidates targeted to L. acidophilus was monitored by flow cytometry. Furthermore, the equilibrium dissociation constant of the aptamer-bacterial cell interaction were estimated.

Abstract: All materials which are intended to have in contact with food and other commodities produced or processed for human consumption are called food contact materials (FCM’s). Stainless steel (SS) – a widely known metallic FCM is used mainly in processing equipment, containers and household utensils. It is known for having numerous industrial and domestic applications worldwide due to its special characteristics of having notable corrosion resistance. However, this corrosion resistance is not all-encompassing since SS may still undergo degradation when subjected to a specific corrosion-inducing environment. SS may be classified according to its microstructure. If the atoms which make up the SS can be viewed as having a face-centered cubic structure, then the alloy is said to be austenitic. This SS grades include the conventional 300-series and the newly-developed 200-series. The former has superior corrosion resistance while the latter is far cheaper. In this study, the corrosion behavior of AISI 202 SS in two different levels of dissolved oxygen (O₂) and three acid concentrations was investigated using electrochemical techniques, namely, open-circuit potential (OCP) measurements and electrochemical impedance spectroscopy (EIS). As the concentration of citric acid is increased, the measured OCP values of the alloy decreased and the polarization resistance (R_p) decreased, indicating decrease in alloy stability and decline in the corrosion resistance, respectively. With regards to effects of dissolved O₂, results revealed that increasing the level of dissolved O₂ has consequently increased the polarization resistance and shifted the OCP to more positive values. All the generated Nyquist plots exhibited a depressed capacitive loops indicating that corrosion in the designated solution occurred with charge transfer as the rate-determining step.

Abstract: Electrochemical reactions occurring at a SiO_x electrode were investigated to gain insight about the effects of film-forming additives, such as vinylene carbonate (VC), ethylene sulfite (ES) and 1,3-propane sultone (PS), on the formation of a solid electrolyte interface (SEI) on the SiO_x electrode. The SEI formed in the presence of PS was found to have the smallest resistance, resulting in low irreversible capacity and good cycle performance.