Electrostrictive and piezoelectrical properties of chitosan-poly(3-hydroxybutyrate) blend films.

Herein, we report the high apparent piezoelectric coefficient for chitosan-poly(3-hydroxybutyrate) (CS-PHB) blend films. The structure of chitosan-poly(3-hydroxybutyrate) (CS-PHB) blend films, exploiting characteristics such as dielectric, polarization, apparent piezoelectric properties, and their dependencies on the composition, were investigated. Based on the results of XRD, SEM, FTIR, PFM, and dielectric spectroscopy measurements, the structure of CS-PHB blend films has been proposed, which consists of spheric-like inclusion formed by precipitating isotactic-PHB interface layer, which consists of syndiotactic-PHB hydrogen bonding with CS, and CS matrix. The synergistic effects of piezoelectricity and electrostriction help explain the high value of the apparent piezoelectric coefficient (d33) obtained in the blend film with 13 wt% of PHB (d33 ≈ 200 pC/N). The investigated CS-PHB blend films are a good candidate for tissue engineering applications.

Chitosan/copper nanocomposites: Correlation between electrical and antibacterial properties.

Correlation between electrical and antibacterial properties of chitosan/copper nanocomposites (CS/CuNPs) is investigated. We aim at achieving the minimum CuNPs concentration in a CS-matrix while keeping high antibacterial activity. UV-vis, TEM and XRD measurements confirms the formation of polygonal metallic CuNPs (ca. 30-50 nm). Interactions between NH2/OH groups of CS and CuNPs were determined by FTIR and XPS suggesting Cu chelation-induced mechanism during the CuNPs formation. DC electrical conductivity measurements reveals a percolation threshold at CuNPs volumetric concentration of ca. 0.143%. Antibacterial assays against Gram-positive bacteria and DC measurements helps correlate the antibacterial potency to the electron transfer between the negatively charged bacteria and CuNPs. Our study suggests that nanocomposite's maximum antibacterial activity is obtained below the electrical percolation threshold at extremely low CuNPs concentrations; this fact may prove useful in the design of nontoxic nanocomposites for biomedical applications.

Synthesis of gold nanoparticles supported on functionalized nanosilica using deep eutectic solvent for an electrochemical enzymatic glucose biosensor.

Engineering of nanoparticle (NP) surfaces offers an effective approach for the development of enzymatic biosensors or microbial fuel cells with a greatly enhanced direct electron transport process. However, lack of control over the surface functionalization process and the operational instability of the immobilized enzymes are serious issues. Herein, we demonstrate a facile and green deep eutectic solvent (DES)-mediated synthetic strategy for efficient amine-surface functionalization of silicon dioxide and to integrate small gold nanoparticles (AuNPs) for a glucose biosensor. Owing to the higher viscosity of the DES, it provides uniform surface functionalization and further coupling of the AuNPs on the SiO2 support with improved stability and dispersion. The amine groups of the functionalized Au-SiO2NPs were covalently linked to the FAD-center of glucose oxidase (GOx) through glutaraldehyde as a bifunctional cross-linker, which promotes formation of "electrical wiring" with the immobilized enzymes. The Au-SiO2NP/GOx/GC electrode exhibits direct electron transfer (DET) for sensing of glucose with a sensitivity of 9.69 µA mM-1, a wide linear range from 0.2 to 7 mM and excellent stability. The present green DES-mediated synthetic approach expands the possibilities to support different metal NPs on SiO2 as a potential platform for biosensor applications.

Combined antibacterial/tissue regeneration response in thermal burns promoted by functional chitosan/silver nanocomposites.

We report the combined antibacterial/tissue regeneration responses to thermal burns promoted by functional chitosan/silver nanocomposites (CS/nAg) with ultralow silver content (0.018wt.%, 7-30nm). Our approach allows one to produce CS/nAg nanocomposites without silver nanoparticles (nAg) agglomeration, with bactericide potency higher than 1wt.% of nAg (ca. 10nm) content and, promoting the healing process in controlled thermal burns. CS/nAg films exhibit high antibacterial activity against S. aureus and P. aeruginosa after 1.5h of incubation, demonstrating the bacterial penetration into hydrated films and their interaction with nAg. Additionally, exceptional healing of induced thermal burns was obtained by increasing myofibroblasts, collagen remodeling, and blood vessel neoformation. These factors are associated with epiderma regeneration after 7days of treatment with no nAg release. Our results corroborate the controlled synthesis of nAg embedded in CS matrix with combined antibacterial/biocompatibility properties aiming to produce functional nanocomposites with potential use in wound dressing and health care applications.

In vivo dc and ac measurements at acupuncture points in healthy and unhealthy people.

OBJECTIVES: The aim of this work was to compare in vivo measurements of direct current (dc) and alternating current (ac) obtained from acupuncture points in Ukrainian and Mexican residents. METHODS: Measurements were made using the method of Voll. The participants were 43 healthy Ukrainian and 71 healthy Mexican residents aged between 20 and 30 years, as well as 24 Mexican patients with a clinical diagnosis of rheumatoid arthritis and 14 patients with a clinical diagnosis of allergy. RESULTS: The results showed that dc measurements are not directly applicable to different populations. Thus, the dc resistance of the acupuncture points in the Mexican participants was 4-5 times larger than in the Ukrainians. In contrast, the capacitance of the two groups did not differ by more than 25%. CONCLUSIONS: Impedance measurements from acupuncture points can be used as an efficient and prompt non-invasive method for diagnostic purposes.

Surface functionalized halloysite nanotubes decorated with silver nanoparticles for enzyme immobilization and biosensing.

Improving enzyme immobilization with high loading capacity and achieving direct electron transfer (DET) between the enzyme and the electrode surface is key to designing highly sensitive enzymatic electrochemical biosensors. Herein, we report a novel approach based on the selective modification of the outer surface of halloysite nanotubes (HNTs) that supports silver nanoparticles (AgNPs) to obtain a hybrid nanocomposite. AgNPs of about 10 nm average size could be uniformly supported on silane-modified HNTs through in situ reduction of Ag+ ions. The resultant nanocomposite shows an excellent support capability for the effective immobilization and electrical wiring of redox enzyme glucose oxidase (GOx). The GOx immobilized HNT/AgNPs were deposited on the glassy carbon electrode (GCE) and utilized for the bioelectrocatalyzed electrochemical detection of glucose. The GOx modified composite electrodes show glucose sensitivity as high as 5.1 µA mM-1 cm-2, which is higher than for the electrodes prepared without surface functionalization.

In vivo impedance measurements on nerves and surrounding skeletal muscles in rats and human body.

The aim of the work was to use impedance measurements to find the location of nerves under the human skin. In vivo impedance measurements were performed on exposed nervous and muscular tissues of rats. Similarly, the impedance measurements were also performed on the skin of six men, over the median nerve at the wrist, as well as 4-5 mm away from this location. Results obtained with rats have shown that the relative permittivity and conductivity of nerves are larger (by almost two orders of magnitude) than those observed for the muscular tissues surrounding the nerve. The results obtained on human skin in the frequency range of 20-200 kHz, when the electrodes were placed over the nerve, show lower resistance and higher capacitance than in the other areas measured. These preliminary results indicate that it may be possible to use impedance measurements to find the location of exposed nerves and also nerves under the skin.

In vivo electrical characteristics of human skin, including at biological active points.

The aim is to compare the mean values of the in vivo electrical characteristics of biological active points (BAPs) with those of the surrounding human skin. The impedance measurements at BAPs and on the surrounding skin are carried out in vivo on ten young, healthy people. The results of the measurements show that the BAP resistance RP is smaller, and the capacitance CP is higher, than the corresponding values for skin, RS and CS, respectively, these differences are larger at low frequencies (at f = 3 Hz, RS/RP = 3.19 and CP/CS = 3.2). The mean values of the impedance measurements at the BAPs are different from those measured on the skin. The dependence of RP and CP on the pressing force, in the range of about 1-5 N, for the BAPs, has a smaller slope than that observed for the surrounding skin. An equivalent circuit for the BAPs is proposed that describes sufficiently well the experimental results obtained. These results show that the large dispersion in the observed impedance characteristics of the human body measurements in different body regions can be related to the influence of the BAPs present under the electrodes.

[Electromyograph unit for automated analysis of interference electromyogram]. / Pristavka k élektromiografu dlia avtomaticheskogo analiza interferentsionnoi élektromiogrammy.

Electromyograph unit for an automated analysis of the interference electromyogram is intended for quantitative analysis of the interference electromyogram, drawn aside by a needle electrode. The offered unit is very simple in design and allows to get the objective data of the functional state of the neuromuscular system.

[Prerequisites to the use of multichannel programmed muscle electrostimulation in patients with infantile cerebral palsy]. / Predposylki ispol'zovaniia mnogokanal'noi programmiruemoi élektrostimuliatsii myshts u bol'nykh detskim tserebral'nym paralichom.

The paper deals with the use of multichannel programmed electrostimulation of muscles or artificial correction of movements to treat patients with infantile cerebral paralysis. This electrostimulation is a highly effective technique for correction of a pathological human motor stereotype and serves to consolidate the physiological movement patterns simulated during treatment sessions.

[State of prostaglandin system in adolescents with the hypotensive type vegetovascular dysfunction during hyperbaric oxygenation]. / Sostoianie sistemy prostaglandinov u podrostkov s vegetososudistoi disfunktsiei po gipotenzivnomu tipu pri provedenii giperbaricheskoi oksigenatsii.

As many as 185 adolescents with hypotensive type vegetovascular dysfunction who ranged between 11 to 14 years old were studied for impact of a conventional treatment and that involving the use of hyperbaric oxygenation on the blood content of prostaglandins E2 and F2 alpha. The control group was 69 essentially healthy adolescents of the same age. Before the start of the treatment those persons presenting with hypotensive type vegetovascular dysfunction revealed an increase in prostaglandins E2 and decline in prostaglandins F2 alpha. There was no change in this trend with the conventional therapy. Owing to hyperbaric oxygenation, the above classes prostaglandins recovered their normal balance, which fact promoted reversal of clinical symptoms of the condition. The results secured permit recommending hyperbaric oxygenation as an efficient mode of treatment of hypotensive type vegetovascular dysfunction in juvenile subjects.

[Character of central hemodynamics in hypotensive type autonomic vascular dysfunction in juveniles]. / Kharakter tsentral'noi gemodinamiki u podrostkov s vegetososudistoi disfunktsiei po gipotenzivnomu tipu.

With an aid of an ultrasound investigation of the heart, aspects of central hemodynamics in 408 juveniles ranging in age between 11 to 14 years have been studied. Of these, 339 were diagnosed as having hypotensive type vegetovascular dysfunction, the other 69 essentially healthy juveniles formed a control group signs of systolic and diastolic dysfunction of the myocardium of the left ventricle revealed in the patients with hypotensive type vegetovascular dysfunction. Systolic dysfunction was compensated by increase in the rate of the heart's beat. Compensation of diastolic dysfunction was achieved by increase in contractility of the muscle of the left ventricle.

[Dynamics of the indices of the prostacyclin-thromboxane system in adolescents with hypotensive type vegetovascular dysfunction exposed to hyperbaric oxygenation]. / Dinamika pokazatelei prostatsiklin-tromboksanovoi sistemy pod vliianiem giperbaricheskoi oksigenatsii u podrostkov s vegetososudistoi disfunktsiei po gipotenzivnomu tipu.

As many as 185 juveniles aged between 11 to 14 years presenting with hypotensive type vegetovascular dysfunction have been examined to study the time-related changes in the blood content of prostacyclin and tromboxane under conditions of hyperbaric oxygenation. The control group copmrised 69 essentially healthy juvenile subjects the same age as those with dysfunction. Hyperbaric oxygenation has had a normalizing effect on indices for the prostacyclin-tromboxane system in those juveniles presenting with hypotensive type vegetovascular dysfunction, which fact can be explained by a drop in tenseness of mechanisms of the vegetative imbalance compensation.

[A method of evaluating the effectiveness of advanced training courses for phthisiologists]. / Metodika otsenki éffektivnosti obucheniia na tsiklakh usovershenstvovaniia ftiziatrov.

A method for estimating efficiency of advanced medical training is described. It was used at 9 courses in advanced medical training of phthisiologists. The method provided estimation of the students knowledge in all the subjects of the program and early correction of the teaching procedure if necessary for improving the results.

[The importance of radionuclide methods in the diagnosis of sarcoidosis and the determination of its activity]. / Znachenie radionuklidnykh metodov v diagnostike sarkoidoza i opredelenii ego aktivnosti.

Sclerotic changes are brought about rather early in case of sarcoidosis. Therefore, it is extremely important for the clinicians to assess a functional condition of the sarcoidosis patients' lungs, to locate the lesions and their extent and to have an idea about the process activity. To a certain degree, the answers to all these questions can be found by means of radionuclide methods using 133Xe, 99mTc and 67Ga. A complex of radioisotope investigations makes it possible to produce a proper assessment of external respiration and capillary blood flow in patients with pulmonary sarcoidosis, including the extent and activity of the process itself.