Electrochemical immunosensing of low-density lipoprotein based on sol-gel encapsulation

Abstract Lipoprotein monitoring is desirable in the management of medical conditions such as atherosclerotic cardiovascular disease and coronary artery disease, in which controlling the concentration of these chylomicrons is crucial. Current clinical methods are complex and present poor reproducibility between laboratories. For these reasons, recent guidelines discard the assessment of low-density lipoprotein cholesterol (LDL-C) as a routine analysis during lipid-lowering therapies. Concerning the importance of monitoring this parameter, the authors present an electrochemical immunosensor constructed from a simple and easy-to-reproduce platform that allows detecting and quantifying LDL nanoparticles directly from human serum samples. The performance of the biosensor was studied by scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The biosensing platform displays good stability and linearity between 30 mg dL-1 and 135 mg dL-1 with a detection limit of 20 mg dL-1. The proposed biosensor can be easily employed for monitoring LDL concentration in clinical treatments.

Corrosion Behaviors of Dental Implant Alloy after Micro-sized Surface Modification in Electrolytes Containing Mn Ion

PURPOSE: The purpose of this study was to investigate the corrosion behaviors of dental implant alloy after micro-sized surface modification in electrolytes containing Mn ion. MATERIALS AND METHODS: Mn-TiO₂ coatings were prepared on the Ti-6Al-4V alloy for dental implants using a plasma electrolytic oxidation (PEO) method carried out in electrolytes containing different concentrations of Mn, namely, 0%, 5%, and 20%. Potentiodynamic method was employed to examine the corrosion behaviors, and the alternating-current (AC) impedance behaviors were examined in 0.9% NaCl solution at 36.5℃±1.0℃ using a potentiostat and an electrochemical impedance spectroscope. The potentiodynamic test was performed with a scanning rate of 1.667 mV s⁻¹ from −1,500 to 2,000 mV. A frequency range of 10⁻¹ to 10⁵ Hz was used for the electrochemical impedance spectroscopy (EIS) measurements. The amplitude of the AC signal was 10 mV, and 5 points per decade were used. The morphology and structure of the samples were examined using field-emission scanning electron microscopy and thin-film X-ray diffraction. The elemental analysis was performed using energy-dispersive X-ray spectroscopy. RESULT: The PEO-treated surface exhibited an irregular pore shape, and the pore size and number of the pores increased with an increase in the Mn concentration. For the PEO-treated surface, a higher corrosion current density (I(corr)) and a lower corrosion potential (E(corr)) was obtained as compared to that of the bulk surface. However, the current density in the passive regions (I(pass)) was found to be more stable for the PEO-treated surface than that of the bulk surface. As the Mn concentration increased, the capacitance values of the outer porous layer and the barrier layer decreased, and the polarization resistance of the barrier layers increased. In the case of the Mn/Ca-P coatings, the corroded surface was found to be covered with corrosion products. CONCLUSION: It is confirmed that corrosion resistance and polarization resistance of PEO-treated alloy increased as Mn content increased, and PEO-treated surface showed lower current density in the passive region.

Characterization of Tetrodes Coated with Au Nanoparticles (AuNPs) and PEDOT and Their Application to Thalamic Neural Signal Detection in vivo

Tetrodes, consisting of four twisted micro-wires can simultaneously record the number of neurons in the brain. To improve the quality of neuronal activity detection, the tetrode tips should be modified to increase the surface area and lower the impedance properties. In this study, tetrode tips were modified by the electrodeposition of Au nanoparticles (AuNPs) and dextran (Dex) doped poly (3,4-ethylenedioxythiophene) (PEDOT). The electrochemical properties were measured using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). A decrease in the impedance value from 4.3 MΩ to 13 kΩ at 1 kHz was achieved by the modified tetrodes. The cathodic charge storage capacity (CSC(C)) of AuNPs-PEDOT deposited tetrodes was 4.5 mC/cm², as determined by CV measurements. The tetrodes that were electroplated with AuNPs and PEDOT exhibited an increased surface area, which reduced the tetrode impedance. In vivo recording in the ventral posterior medial (VPM) nucleus of the thalamus was performed to investigate the single-unit activity in normal rats. To evaluate the recording performance of modified tetrodes, spontaneous spike signals were recorded. The values of the L-ratio, isolation distance and signal-to-noise (SNR) confirmed that electroplating the tetrode surface with AuNPs and PEDOT improved the recording performance, and these parameters could be used to effectively quantify the spikes of each cluster.

Rapid culture-based detection of living mycobacteria using microchannel electrical impedance spectroscopy (m-EIS)

BACKGROUND: Multiple techniques exist for detecting Mycobacteria, each having its own advantages and drawbacks. Among them, automated culture-based systems like the BACTEC-MGIT™ are popular because they are inexpensive, reliable and highly accurate. However, they have a relatively long "time-to-detection" (TTD). Hence, a method that retains the reliability and low-cost of the MGIT system, while reducing TTD would be highly desirable. METHODS: Living bacterial cells possess a membrane potential, on account of which they store charge when subjected to an AC-field. This charge storage (bulk capacitance) can be estimated using impedance measurements at multiple frequencies. An increase in the number of living cells during culture is reflected in an increase in bulk capacitance, and this forms the basis of our detection. M. bovis BCG and M. smegmatis suspensions with differing initial loads are cultured in MGIT media supplemented with OADC and Middlebrook 7H9 media respectively, electrical "scans" taken at regular intervals and the bulk capacitance estimated from the scans. Bulk capacitance estimates at later time-points are statistically compared to the suspension's baseline value. A statistically significant increase is assumed to indicate the presence of proliferating mycobacteria. RESULTS: Our TTDs were 60 and 36 h for M. bovis BCG and 20 and 9 h for M. smegmatis with initial loads of 1000 CFU/ml and 100,000 CFU/ml respectively. The corresponding TTDs for the commercial BACTEC MGIT 960 system were 131 and 84.6 h for M. bovis BCG and 41.7 and 12 h for M smegmatis, respectively. CONCLUSION: Our culture-based detection method using multi-frequency impedance measurements is capable of detecting mycobacteria faster than current commercial systems.

A Fundamental Study to Observe Correlation at Molecular Level between Bio-Samples of Patients and Indicated Homoeopathic Medicines

Background: 'Like cures like' is the principle that is followed in homoeopathy. Substances whichcause disorder in healthy individuals are used as medicines to treat similar patterns of disorder in sick persons. This article aims to find out whether any similarity picture exists at molecular levelalso that can make a selection of medicines based on scientifically measurable parameters. Method: It consisted of getting frequency domain signatures for the dielectric functions of (i) biofluids(blood serums) of six arthritis patients and (ii) medicines selected for them on the basis of macroscopic similarity. Then, they were compared to find existence/absence of similarity betweenthem.Results: Medicines administered to the six patients were Rhus tox 200cH, Thuja 30cH, Medorrhinum 200cH. The dielectric loss at resonance for the bio-fluids of the patients and themedicines are given in the body of the article.Conclusion: It was observed that the patients who had beneficial results with their medicines havea similarity (resonance frequency matching) in spectral signatures of the two groups of substancesi.e. bio-fluids (blood serum) of patients and the indicated remedies. This similarity was not evidentin the cases where medicines failed to benefit the patients. These results are explorative andenthusiastic, but as the research is limited only to patients with arthritis, generalization could notbe drawn. Further work with more rigor is required to establish the facts and apply generalizationsto other disease condition. In future, this might be a new tool to integrate the fundamental researchwith clinical applications in homeopathy. (AU)

Corrosion behavior of zirconia in acidulated phosphate fluoride

ABSTRACT Objective The corrosion behavior of zirconia in acidulated phosphate fluoride (APF) representing acidic environments and fluoride treatments was studied. Material and Methods Zirconia rods were immersed in 1.23% and 0.123% APF solutions and maintained at 37°C for determined periods of time. Surfaces of all specimens were imaged using digital microscopy and scanning electron microscopy (SEM). Sample mass and dimensions were measured for mass loss determination. Samples were characterized by powder X-ray diffraction (XRD) to detect changes in crystallinity. A biosensor based on electrochemical impedance spectroscopy (EIS) was used to detect ion dissolution of material into the immersion media. Results Digital microscopy revealed diminishing luster of the materials and SEM showed increased superficial corrosion of zirconia submerged in 1.23% APF. Although no structural change was found, the absorption of salts (sodium phosphate) onto the surface of the materials bathed in 0.123% APF was significant. EIS indicated a greater change of impedance for the immersion solutions with increasing bathing time. Conclusion Immersion of zirconia in APF solutions showed deterioration limited to the surface, not extending to the bulk of the material. Inferences on zirconia performance in acidic oral environment can be elucidated from the study.

Effect of ultrahigh diluted homeopathic medicines on the electrical properties of PVDF-HFP

In an effort to improve the electrical properties of the electroactive Poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP), we introduced a novel and simple approach to synthesize PVDFHFP composite films by incorporating ultrahigh dilutions of two homeopathic medicines Ferrum metallicum (FM) and Zincum oxidatum (ZO) in different potencies. The homeo-PVDF-composite films (HPCF) were synthesized by simple solution casting technique. XRD, FESEM, FTIR studies were performed to check the presence of nanoparticles in the film. The electrical properties of the HPCF samples get enhanced significantly due to the incorporation of the medicines and the effect increases with the increase in potency of the medicines.

Effects of chemical composition on the corrosion of dental alloys

The aim of this study was to determine the effect of the oral environment on the corrosion of dental alloys with different compositions, using electrochemical methods. The corrosion rates were obtained from the current-potential curves and electrochemical impedance spectroscopy (EIS). The effect of artificial saliva on the corrosion of dental alloys was dependent on alloy composition. Dissolution of the ions occurred in all tested dental alloys and the results were strongly dependent on the general alloy composition. Regarding the alloys containing nickel, the Ni-Cr and Ni-Cr-Ti alloys released 0.62 mg/L of Ni on average, while the Co-Cr dental alloy released ions between 0.01 and 0.03 mg/L of Co and Cr, respectively.The open-circuit potential stabilized at a higher level with lower deviation (standard deviation: Ni-Cr-6Ti = 32 mV/SCE and Co-Cr = 54 mV/SCE). The potenciodynamic curves of the dental alloys showed that the Ni-based dental alloy with >70 wt% of Ni had a similar curve and the Co-Cr dental alloy showed a low current density and hence a high resistance to corrosion compared with the Ni-based dental alloys. Some changes in microstructure were observed and this fact influenced the corrosion behavior for the alloys. The lower corrosion resistance also led to greater release of nickel ions to the medium. The quantity of Co ions released from the Co-Cr-Mo alloy was relatively small in the solutions. In addition, the quantity of Cr ions released into the artificial saliva from the Co-Cr alloy was lower than Cr release from the Ni-based dental alloys.

O objetivo deste estudo foi determinar o efeito do ambiente bucal na corrosão de diferentes ligas odontológicas, utilizando métodos eletroquímicos. Os índices de corrosão foram obtidos por meio das curvas de corrente-potencial e impedância eletroquímica (EIS). O efeito de saliva artificial na corrosão de ligas odontológicas foi dependente da composição. A dissolução dos íons ocorreu em todas as amostras e os resultados foram dependentes da composição da liga. Algumas mudanças na microestrutura foram observadas durante o estudo e influenciou o comportamento corrosivo das ligas investigadas. As ligas de Ni-Cr e Ni-Cr-Ti libertaram quantidade de 0,62 mg/L de íons Ni enquanto a liga de Co-Cr liberou entre 0,01 e 0,03 mg/L. As curvas potenciodinâmicas das ligas odontológicas mostraram que as ligas a base >70 wt% de Ni obtiveram curvas similares e a liga de Co-Cr apresentou a menor densidade de corrente e em consequência uma resistência alta a corrosão quando comparada as ligas à base de Ni. A baixa resistência à corrosão também levou a maior libertação de íons de níquel para o meio e a quantidade de Co liberado pela liga de Co-Cr-Mo foi relativamente pequena nas soluções. As quantidades de Cr liberada na saliva artificial pela liga de Co-Cr foi menor que a libertação de Cr pela liga à base de Ni.

Electrical impedance spectroscopy for evaluation of the influence of simulated weightlessness on the electrical properties of rat blood / 生物医学工程学杂志

In the present study, the AC impedance of rat blood was measured with Agilent 4294A impedance analyzer in the frequency range of 10(4)-10(8) Hz, and the effect of simulated weightlessness (SWL)on electrical properties of rat blood was investigated by analyzing the data characteristics with the use of electrical impedance spectroscopy, the Bode diagram, the Nyquist diagram and the Nichols diagram. The results demonstrated 60 days SWL caused some changes: (1) the electrical impedance of rat blood were reduced, mainly in the real part of complex impedance (Z'o and Z'infinity), the electrical impedance modulus amplitude (|Z*|o and |Z*|infinity), the impedance relaxation strength (deltaZ', delta|Z*|) and the logarithm of impedance modulus amplitude at low frequency (Log |Z*|o) were lower than that in the control (CON) group; (2) the characteristic frequency of the electrical impedance spectrum of rat blood and the phase angle were increases, mainly in the characteristic frequency (fc1, fc2) and the phase angle [theta(p) (degree), theta(p) (radian)] increased compared with that in the CON group. These data indicate that SWL leads to reduced resistivity and enhanced conductivity of blood.

Biophysical approach to anemia of rheumatoid arthritis

Serum iron, zinc and copper concentrations in Rheumatoid Arthritic [RA] patients as compared to normal controls were measured. Serum calcium, magnesium, phosphorus concentrations, and alkaline phosphatase activity as well as 1, 25 [OH][2] Vitamin D in RA patients as compared to normal controls were measured. In addition, Hemoglobin derivatives, and the dielectric relaxation in the frequency range 100 KHz up to 10 MHz of Hb molecules of RA patients compared to normal controls were measured. It was found that a significant increase in Met-Hb, abnormal dynamic motion of Hb and changes in the overall shape of Hb. Also, The dielectric results indicated that the molecular shape of hemoglobin tends to deviate from the spherical form as the disease geos to the severity