PROTECTIVE ASPECTS IN CONTACTLESS INFRARED THERMOGRAPHY FEVER SCREENING

Main symptoms found in patients with same diseases as for example COVID-19 is febrile. The infrared thermography (IRT) represents a fast measurement in case of screening in public places. One of the limitations of IRT is the resolution of sensor, which has close connection with the distance between camera and ROI. To maximize the effectivity of resolution of the camera is to reduce the distance from the object. The aim of presented study showed the possibility how to protect the camera or medical staff that operates the device against potential infection or contamination from the person with infection. Two protective foils of different thickness (40μm; 9μm) were tested as a barrier between the IRT and the ROI (black body model and human face). Even though the results have shown that the transparent foils decrease linearly the measured value of the temperature, it can be used as a protective barrier between IRT and the object if an appropriate recalculation is done during analysis of IRT images. Results are acceptable in the case of 9μm foil especially. The authors see this possibility as a minor concession from IRT standards but as a great help in health protection. The transparent foil can be used as protective barrier of the infrared camera

Hydrogel Containing Anti-CD44-Labeled Microparticles, Guide Bone Tissue Formation in Osteochondral Defects in Rabbits

Hydrogels are suitable for osteochondral defect regeneration as they mimic the viscoelastic environment of cartilage. However, their biomechanical properties are not sufficient to withstand high mechanical forces. Therefore, we have prepared electrospun poly-ε-caprolactone-chitosan (PCL-chit) and poly(ethylene oxide)-chitosan (PEO-chit) nanofibers, and FTIR analysis confirmed successful blending of chitosan with other polymers. The biocompatibility of PCL-chit and PEO-chit scaffolds was tested; fibrochondrocytes and chondrocytes seeded on PCL-chit showed superior metabolic activity. The PCL-chit nanofibers were cryogenically grinded into microparticles (mean size of about 500 µm) and further modified by polyethylene glycol–biotin in order to bind the anti-CD44 antibody, a glycoprotein interacting with hyaluronic acid (PCL-chit-PEGb-antiCD44). The PCL-chit or PCL-chit-PEGb-antiCD44 microparticles were mixed with a composite gel (collagen/fibrin/platelet rich plasma) to improve its biomechanical properties. The storage modulus was higher in the composite gel with microparticles compared to fibrin. The Eloss of the composite gel and fibrin was higher than that of the composite gel with microparticles. The composite gel either with or without microparticles was further tested in vivo in a model of osteochondral defects in rabbits. PCL-chit-PEGb-antiCD44 significantly enhanced osteogenic regeneration, mainly by desmogenous ossification, but decreased chondrogenic differentiation in the defects. PCL-chit-PEGb showed a more homogeneous distribution of hyaline cartilage and enhanced hyaline cartilage differentiation

Elektrische Felder an biomimetischen Grenzflächen : spektro-elektrochemische Untersuchungen des Schwingungs-Stark-Effekts an künstlichen Membranen

Electric fields and electrostatic interactions can essentially influence biological processes. This is particularly true for membrane proteins since their activities may be controlled by changes of the transmembrane potential. To elucidate such processes requires appropriate biomimetic membranes, preferentially on electrodes to allow variations of the potential across a bilayer. Particular convenient model membranes are tethered bilayer lipid membranes (tBLM) on nanostructured Au electrodes, which were characterized with a combination of spectroscopy and electrochemistry. The Au film serves as IR signal amplifier and working electrode at the same time. Thereby, structural and functional characterizations of membrane-embedded proteins could be detected. Quantification of electric fields within the artificial biomimetic membrane is experimentally extremely challenging but of high relevance understanding molecular processes at membranes. As a particularly promising experimental approach, the vibrational Stark effect (VSE) may be exploited. The VSE refers to the electric field dependent modulation of the frequency of a localised vibrational mode. Suitable Stark reporter groups for biological systems are the thiocyanate or cyanide group, which exhibit frequencies that can easily be distinguished from lipid and protein vibrations. On the basis of electrochemical impedance spectroscopy (EIS) and surface-enhanced IR absorbance (SEIRA) spectroscopy the electrostatics of a frequently used simple membrane model, a self-assembled monolayer (SAM), on Au and Ag electrodes were analysed. Here we have investigated SAMs of 6-mercaptohexanenitrile (C5CN), 7-mercaptoheptanenitrile (C6CN) and 4 mercaptobenzonitrile (MBN). The potential-dependent changes of the VSE were determined on the basis of an electrostatic model to derive a relationship between the electrode potential and the electric field at the head groups of the SAMs. The analyses afforded electric field strengths in the order of 108 V/m. In this work, for the first time, Stark reporter groups were incorporated into the tBLM system on a nanostructured Au electrode. A thiocyanate labelled sterol derivate 7–beta-thiocyanocholest-5-en-3-betaylacetate (CLSCN) combined with phospholipids, 1-palmitoyl-2- oleoyl-sn-glycero-3-phosphocholine (POPC) and 1-palmitoyl-2-oleoyl-sn-glycero-phospho-(1’-rac-glycerol) (POPG), was used to characterise the electrostatics and local electric field inside the tBLM. To determine the relationship between the electrode potential and the transmembrane potential, i.e. the quantity controlling membrane processes, two Stark reporter groups were incorporated into the model membrane: the cyanide function of MBN as one fraction of the phase-separated SAM and the azide group introduced in the head group of a phospholipid (1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-(6-azidohexanoyl) - PE-N3). The combined spectroscopic and electro-chemical analysis provided insights into the electrostatics of the water reservoir between the SAM and the lipid bilayer. Upon adaptation of the electrostatic model to the tBLM system, an approximate relationship between the electrode potential and the transmembrane potential was obtained that provides a satisfactory description in the range of the effective potential of zero charge. Altogether, the present work has demonstrated the great potential of EIS and SEIRA spectroscopy in combination with the vibrational Stark effect to study electrostatic interactions and quantify local electric fields within artificial membrane models.Elektrische Felder und elektrostatische Wechselwirkungen können verschiedene biologische Prozesse wesentlich beeinflussen. So kann durch Änderungen des Transmembranpotentials die Aktivität und Struktur von Membranproteinen gesteuert werden. Zur Untersuchung dieser Prozesse sind geeignete biomimetische Modellmembranen erforderlich, die zum Zweck der Potentialkontrolle auf Elektroden aufgebracht werden. Besonders geeignete Membranmodelle sind sog. „tethered bilayer lipid membranes“ (tBLM) auf nanostrukturierten Au-Elektroden, die elektrochemisch und spektroskopisch charakterisiert wurden. Dabei dient die Au-Unterlage zum einen als IR-Signalverstärker und zum anderen als Arbeitselektrode. Mit dieser Methode wurden strukturelle und funktionelle Charakterisierungen von Membranproteinen erhalten. Die Quantifizierung elektrischer Felder oder elektrostatischer Wechselwirkungen innerhalb der künstlichen biomimetischen Membranen ist experimentell herausfordernd, aber von größter Bedeutung für das Verständnis molekularer Prozesse in Membranen. Der Schwingungs-Stark-Effekt (vibrational Stark-effect - VSE) ist dabei ein besonders vielversprechender experimenteller Ansatz, der die Modulation der Frequenz von Valenzschwingungen durch lokale elektrische Felder beschreibt. Geeignete Stark-Reportergruppen für biologische Systeme sind die Thiocyanat- oder Cyanidgruppe, deren Schwingungsfrequenzen sich leicht von Lipid- und Proteinschwingungen unterscheiden lassen. Auf der Basis der elektrochemischen Impedanzspektroskopie (EIS) und oberflächenverstärkten IR Absorptionsspektroskopie (SEIRAS) wurden zunächst die elektrostatischen Eigenschaften der einfachsten Membranmodelle, d.h. selbstorganisierter Monolagen (SAM) auf nanostrukturierten Au- und Ag-Elektroden analysiert. Dazu wurden SAMs aus 6-Mercaptohexannitril (C5CN), 7-Mercaptoheptannitril (C6CN) und 4 Mercaptobenzonitril (MBN) untersucht. Die potentialabhängige Variation des VSE wurde auf der Grundlage eines elektrostatischen Modells beschrieben. Dabei wurden für SAM-beschichtete Elektroden lokale elektrische Felder im Kopfgruppenbereich des SAMs von 108 V/m bestimmt. In dieser Arbeit wurden zum ersten Mal Stark-Reportergruppen in das tBLM-System auf einer nanostrukturierten Au-Elektrode eingebaut. Dazu wurde ein Sterolderivat mit einer Thiocyanatgruppe (7-beta-Thiocyanocholest-5-en-3-betaylacetat - CLSCN) in Kombination mit Phospholipiden, 1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphocholin (POPC) und 1-Palmitoyl-2-oleoyl-sn-glycero-phospho-(1'-rac-glycerol) (POPG) verwendet, um die Elektrostatik und das lokale elektrische Feld in der tBLM zu charakterisieren. Zur Bestimmung des Zusammenhangs zwischen Elektroden- und Transmembranpotential, d.h. der Größe, die Membranprozesse kontrolliert, wurden zwei VSE Reportergruppen in die Modellmembran eingebaut: die Cyanid-Funktion des MBN, das als eine Fraktion des Phasen-separierten SAMs diente, und die Azid-Funktion, die in die Kopfgruppe eines Phospholipids (1,2-Dipalmitoyl-sn-Glycero-3-Phosphoethanolamine-N-(6-Azidohexanoyl) - PE-N3) inkorporiert wurde. Der kombinierte Einsatz der EIS und SEIRA Technik lieferte neue Einsichten in die elektrostatischen Eigenschaften des Wasserreservoirs zwischen SAM und Lipiddoppelschicht. Nach Anpassung des elektrostatischen Modells an die tBLM konnte eine Beziehung zwischen dem Elektroden- und Transmembranpotential entwickelt werden, das zufriedenstellende Ergebnisse im Bereich des effektiven Potentials der Nullladung lieferte. Insgesamt demonstriert die vorliegende Arbeit das große Potenzial der EIS- und SEIRA-Spektroskopie in Kombination mit dem Schwingungs-Stark-Effekts für die Quantifizierung elektrostatischer Wechselwirkungen und lokaler elektrische Felder in Membranmodellen

Potential Distribution across Model Membranes

Membrane models assembled on electrodes are widely used tools to study potential-dependent molecular processes at or in membranes. However, the relationship between the electrode potential and the potential across the membrane is not known. Here we studied lipid bilayers immobilized on mixed self-assembled monolayers (SAM) on Au electrodes. The mixed SAM was composed of thiol derivatives of different chain lengths such that between the islands of the short one, mercapto­benzonitrile (MBN), and the tethered lipid bilayer an aqueous compartment was formed. The nitrile function of MBN, which served as a reporter group for the vibrational Stark effect (VSE), was probed by surface-enhanced infrared absorption spectroscopy to determine the local electric field as a function of the electrode potential for pure MBN, mixed SAM, and the bilayer system. In parallel, we calculated electric fields at the VSE probe by molecular dynamics (MD) simulations for different charge densities on the metal, thereby mimicking electrode potential changes. The agreement with the experiments was very good for the calculations of the pure MBN SAM and only slightly worse for the mixed SAM. The comparison with the experiments also guided the design of the bilayer system in the MD setups, which were selected to calculate the electrode potential dependence of the transmembrane potential, a quantity that is not directly accessible by the experiments. The results agree very well with estimates in previous studies and thus demonstrate that the present combined experimental–theoretical approach is a promising tool for describing potential-dependent processes at biomimetic interfaces

Electrochemical and Resonance Raman Spectroscopic Studies of Water-Oxidizing Ruthenium-Terpyridyl-Bipyridyl Complexes

The irreversible conversion of single-site water oxidation catalysts (WOC) into the more rugged catalysts structurally related to [(trpy)(5,5&rsquo;-X2-bpy)RuIV(&mu;-O)RuIV(trpy)(O)(H2O)]4+ (X = H, 1-dn4+; X = F, 2-dn4+) represents a critical issue in developing active and durable WOC. In this work, the electrochemical and acid-base properties of 1-dn4+ and 2-dn4+ were evaluated. In-situ resonance Raman spectroscopy was employed to characterize species formed upon stoichiometric oxidation of single-site catalysts demonstrating the formation of high oxidation states mononuclear Ru=O and RuO-O complexes. Under turnover conditions, the dinuclear intermediates, 1-dn4+ and 2-dn4+, as well as the previously proposed [RuVI(trpy)(O)2(H2O)]2+ complex (32+) are formed. 32+ is a pivotal intermediate that provides access to the formation of dinuclear species. Single crystal X-ray diffraction analysis of the isolated complex [RuIV(O)(trpy)(5,5&rsquo;-F2-bpy)]2+ reveals a clear elongation of the Ru-N bond located in the trans position to the oxo group, documenting the weakness of this bond which promotes the release of the bpy ligand and the subsequent formation of 32+. &nbsp;</p

Monitoring the Orientational Changes of Alamethicin during Incorporation into Bilayer Lipid Membranes

Antimicrobial peptides (AMPs) are the first line of defense after contact of an infectious invader, for example, bacterium or virus, with a host and an integral part of the innate immune system of humans. Their broad spectrum of biological functions ranges from cell membrane disruption over facilitation of chemotaxis to interaction with membrane-bound or intracellular receptors, thus providing novel strategies to overcome bacterial resistances. Especially, the clarification of the mechanisms and dynamics of AMP incorporation into bacterial membranes is of high interest, and different mechanistic models are still under discussion. In this work, we studied the incorporation of the peptaibol alamethicin (ALM) into tethered bilayer lipid membranes on electrodes in combination with surface-enhanced infrared absorption (SEIRA) spectroscopy. This approach allows monitoring the spontaneous and potential-induced ion channel formation of ALM in situ. The complex incorporation kinetics revealed a multistep mechanism that points to peptide–peptide interactions prior to penetrating the membrane and adopting the transmembrane configuration. On the basis of the anisotropy of the backbone amide I and II infrared absorptions determined by density functional theory calculations, we employed a mathematical model to evaluate ALM reorientations monitored by SEIRA spectroscopy. Accordingly, ALM was found to adopt inclination angles of ca. 69°–78° and 21° in its interfacially adsorbed and transmembrane incorporated states, respectively. These orientations can be stabilized efficiently by the dipolar interaction with lipid head groups or by the application of a potential gradient. The presented potential-controlled mechanistic study suggests an N-terminal integration of ALM into membranes as monomers or parallel oligomers to form ion channels composed of parallel-oriented helices, whereas antiparallel oligomers are barred from intrusion

Determination of the Local Electric Field at Au/SAM Interfaces Using the Vibrational Stark Effect

A comprehensive understanding of physical and chemical processes at biological membranes requires the knowledge of the interfacial electric field which is a key parameter for controlling molecular structures and reaction dynamics. An appropriate approach is based on the vibrational Stark effect (VSE) that exploits the electric-field dependent perturbation of localized vibrational modes. In this work, 6-mercaptohexanenitrile (C5CN) and 7-mercaptoheptanenitrile (C6CN) were used to form self-assembled monolayers (SAMs) on a nanostructured Au electrode as a simple mimic for biomembranes. The CN stretching mode was probed by surface enhanced infrared absorption (SEIRA) spectroscopy to determine the frequency and intensity as a function of the electrode potential. The intensity variations were related to potential-dependent changes of the nitrile orientation with respect to the electric field. Supported by electrochemical impedance spectroscopy, molecular dynamics simulations, and quantum chemical calculations the frequency changes were translated into profiles of the interfacial electric field, affording field strengths up to 4 × 10⁸ V/m (C6CN) and 1.3 × 10⁹ V/m (C5CN) between +0.4 and −0.4 V (vs Ag/AgCl). These profiles compare very well with the predictions of a simple electrostatic model developed in this work. This model is shown to be applicable to different types of electrode/SAM systems and allows for a quick estimate of interfacial electric fields. Finally, the implications for electric-field dependent processes at biomembranes are discussed

Hydrogel Containing Anti-CD44-Labeled Microparticles, Guide Bone Tissue Formation in Osteochondral Defects in Rabbits

Hydrogels are suitable for osteochondral defect regeneration as they mimic the viscoelastic environment of cartilage. However, their biomechanical properties are not sufficient to withstand high mechanical forces. Therefore, we have prepared electrospun poly-ε-caprolactone-chitosan (PCL-chit) and poly(ethylene oxide)-chitosan (PEO-chit) nanofibers, and FTIR analysis confirmed successful blending of chitosan with other polymers. The biocompatibility of PCL-chit and PEO-chit scaffolds was tested; fibrochondrocytes and chondrocytes seeded on PCL-chit showed superior metabolic activity. The PCL-chit nanofibers were cryogenically grinded into microparticles (mean size of about 500 µm) and further modified by polyethylene glycol–biotin in order to bind the anti-CD44 antibody, a glycoprotein interacting with hyaluronic acid (PCL-chit-PEGb-antiCD44). The PCL-chit or PCL-chit-PEGb-antiCD44 microparticles were mixed with a composite gel (collagen/fibrin/platelet rich plasma) to improve its biomechanical properties. The storage modulus was higher in the composite gel with microparticles compared to fibrin. The Eloss of the composite gel and fibrin was higher than that of the composite gel with microparticles. The composite gel either with or without microparticles was further tested in vivo in a model of osteochondral defects in rabbits. PCL-chit-PEGb-antiCD44 significantly enhanced osteogenic regeneration, mainly by desmogenous ossification, but decreased chondrogenic differentiation in the defects. PCL-chit-PEGb showed a more homogeneous distribution of hyaline cartilage and enhanced hyaline cartilage differentiation