Changes In Membrane Thickness Research Articles

Dexamethasone-loaded PLGA porous microspheres used as 3D-bioprinted bioink promote tissue-engineered cartilage regeneration

The current investigation focused on fabricating and thoroughly analyzing porous microspheres (MPs) comprising poly (lactic-co-glycolic acid, PLGA) encapsulating dexamethasone, by utilizing the water-in-oil-in-water (W/O/W) emulsion solvent evaporation technique. The meticulous characterization encompassed various parameters, including particle size distribution, morphology, and polymer integrity, all of which exhibited consistent attributes across the MPs populations. The analysis of drug content and release kinetics revealed a sustained and controlled liberation of dexamethasone, characterized by an initial burst release within the initial 3 days followed by a gradual, protracted release profile. Subsequent in vivo assessments further validated the potent anti-inflammatory effects of the dexamethasone-loaded PLGA MPs, as evidenced by notable reductions in CD86 immunohistochemical staining intensity, along with the change in membrane thickness. Additionally, the MPs demonstrated an impressive capability to support the maintenance of cartilage phenotype, as indicated by the augmented secretion of cartilage matrix components and elevated glycosaminoglycan content.  

Distributing aminophospholipids asymmetrically across leaflets causes anomalous membrane stiffening

We studied the mechanical leaflet coupling of prototypic mammalian plasma membranes using neutron spin-echo spectroscopy. In particular, we examined a series of asymmetric phospholipid vesicles with phosphatidylcholine and sphingomyelin enriched in the outer leaflet and inner leaflets composed of phosphatidylethanolamine/phosphatidylserine mixtures. The bending rigidities of most asymmetric membranes were anomalously high, exceeding even those of symmetric membranes formed from their cognate leaflets. Only asymmetric vesicles with outer leaflets enriched in sphingolipid displayed bending rigidities in conformity with these symmetric controls. We performed complementary small-angle neutron and x-ray experiments on the same vesicles to examine possible links to structural coupling mechanisms, which would show up in corresponding changes in membrane thickness. In addition, we estimated differential stress between leaflets originating either from a mismatch of their lateral areas or spontaneous curvatures. However, no correlation with asymmetry-induced membrane stiffening was observed. To reconcile our findings, we speculate that an asymmetric distribution of charged or H-bond forming lipids may induce an intraleaflet coupling, which increases the weight of hard undulatory modes of membrane fluctuations and hence the overall membrane stiffness.

Entrapment and Voltage-Driven Reorganization of Hydrophobic Nanoparticles in Planar Phospholipid Bilayers.

Engineered nanoparticles (NPs) possess diverse physical and chemical properties, which make them attractive agents for targeted cellular interactions within the human body. Once affiliated with the plasma membrane, NPs can become embedded within its hydrophobic core, which can limit the intended therapeutic functionality and affect the associated toxicity. As such, understanding the physical effects of embedded NPs on a plasma membrane is critical to understanding their design and clinical use. Here, we demonstrate that functionalized, hydrophobic gold NPs dissolved in oil can be directly trapped within the hydrophobic interior of a phospholipid membrane assembled using the droplet interface bilayer technique. This approach to model membrane formation preserves lateral lipid diffusion found in cell membranes and permits simultaneous imaging and electrophysiology to study the effects of embedded NPs on the electromechanical properties of the bilayer. We show that trapped NPs enhance ion conductance and lateral membrane tension in 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1,2-diphytanoyl-sn-glycero-3-phosphocholine (DPhPC) bilayers while lowering the adhesive energy of the joined droplets. Embedded NPs also cause changes in bilayer capacitance and area in response to applied voltage, which are nonmonotonic for DOPC bilayers. This electrophysical characterization can reveal NP entrapment without relying on changes in membrane thickness. By evaluating the energetic components of membrane tension under an applied potential, we demonstrate that these nonmonotonic, voltage-dependent responses are caused by reversible clustering of NPs within the unsaturated DOPC membrane core; aggregates form spontaneously at low voltages and are dispersed by higher transmembrane potentials of magnitude similar to those found in the cellular environment. These findings allow for a better understanding of lipid-dependent NP interactions, while providing a platform to study relationships between other hydrophobic nanomaterials and organic membranes.

Influence of Seawater Cation Contamination on the Performance and Lifetime of PEM Electrolysis Cells

Polymer electrolyte membrane water electrolysis (PEMWE) requires highly purified water (resistivity ≥ 1 MOhm·cm). If the electrolyzer is fed with water of poor quality, both the lifetime and the performance are reduced. [1] Mainly cationic species cause several degradation effects in the membrane and the catalyst layer of the cell. Within the membrane, protons are exchanged by the cations, leading to a reduced ionic conductivity. Further, according to Fenton's reaction, some transition metal cations catalyze the formation of radicals attacking the membrane structure. [2] Additionally, the catalyst layer is occupied with cations, which causes a reduced electrochemical surface area. [3] For offshore applications of PEMWE, the feed water is generated by the purification of seawater, which contains a high amount of impurities such as calcium and magnesium. [4, 5] This purified seawater nevertheless contains some impurities [4] and as soon as the purification process is erroneous, the PEMWE is contaminated with the cations. For that reason, the scope of this contribution is to find a threshold value of a magnesium and calcium contamination in the water supply of a PEM water electrolysis cell, which affects the cell performance and lifetime to a tolerable extent.To do so, electrolysis cells equipped with commercially available catalyst coated membranes (CCM) are contaminated with magnesium and calcium solutions of different concentrations and operated for up to 100 h. The actual performance of a cell is measured by polarization curve and electrochemical impedance spectroscopy every 25 h. In order to get deeper insights into the degradation phenomena, several in- and ex-situ characterization techniques are used. The investigation contains ion chromatography (IC), inductive coupled plasma mass spectroscopy (ICP-MS), mass spectrometry (MS) and thermo-gravimetric analysis (TGA).The polarization curves show the cell's overall performance over time but give only a little information about the occurring phenomena. The high frequency resistance of the measured impedance spectra can determine the change in the ionic resistance of the membrane. This ionic resistance increases when the cations occupy the active sides of the membrane. Otherwise, a possible membrane thinning caused by the radical attack decreases the ionic resistance. To distinguish between these antithetical effects, the fluoride concentration in the water supply is measured with an anion IC. The resulting fluoride emission rate correlates with membrane thinning and quantifies this effect. Another method to detect membrane thinning is investigating the process gases with MS. The occurring gas crossover, especially at the anode with its H2 in O2 content, indicates a membrane thickness change. The occupation of the catalyst particles by cations is measurable in-situ by tracking the polarization current at a set potential over time and the impedance spectra reveal changes in the charge-transfer and resistance characteristics as well. Other degradation effects like losing catalyst particles because of weak ionomer structure or catalyst dissolution are investigated with the ICP-MS, which measures the metal concentration in the process water. At the end of the test procedure, the CCMs are analyzed in the TGA to investigate the thermal stability after the operation and the residual weight fraction of the catalyst particles, which is also an indicator for catalyst loss. With these in- and ex-situ characterization techniques, the degradation effects in a PEM electrolysis cell caused by different cation contaminations are investigated separately and their specific contribution is revealed. With this knowledge of different cation concentrations, a relation is derived to find a tolerable concentration of cations in PEM electrolysis operation.

Enhanced polarization and abnormal flexural deformation in bent freestanding perovskite oxides

Recent realizations of ultrathin freestanding perovskite oxides offer a unique platform to probe novel properties in two-dimensional oxides. Here, we observe a giant flexoelectric response in freestanding BiFeO3 and SrTiO3 in their bent state arising from strain gradients up to 3.5 × 107 m−1, suggesting a promising approach for realizing ultra-large polarizations. Additionally, a substantial change in membrane thickness is discovered in bent freestanding BiFeO3, which implies an unusual bending-expansion/shrinkage effect in the ferroelectric membrane that has never been seen before in crystalline materials. Our theoretical model reveals that this unprecedented flexural deformation within the membrane is attributable to a flexoelectricity–piezoelectricity interplay. The finding unveils intriguing nanoscale electromechanical properties and provides guidance for their practical applications in flexible nanoelectromechanical systems.

The Effects of Cholesterol Oxidation on Erythrocyte Plasma Membranes: A Monolayer Study.

Cholesterol plays a key role in the molecular and mesoscopic organisation of lipid membranes and it is expected that changes in its molecular structure (e.g., through environmental factors such as oxidative stress) may affect adversely membrane properties and function. In this study, we present evidence that oxidation of cholesterol has significant effects on the mechanical properties, molecular and mesoscopic organisation and lipid–sterol interactions in condensed monolayers composed of the main species found in the inner leaflet of the erythrocyte membrane. Using a combination of experimental methods (static area compressibility, surface dilatational rheology, fluorescence microscopy, and surface sensitive X-ray techniques) and atomistic molecular dynamics simulations, we show that oxidation of cholesterol to 7-ketocholesterol leads to stiffening of the monolayer (under both static and dynamic conditions), significant changes in the monolayer microdomain organisation, disruption in the van der Waals, electrostatic and hydrophobic interactions between the sterol and the other lipid species, and the lipid membrane hydration. Surface sensitive X-ray techniques reveal that, whilst the molecular packing mode is not significantly affected by cholesterol oxidation in these condensed phases, there are subtle changes in membrane thickness and a significant decrease in the coherence length in monolayers containing 7-ketocholesterol.

Effect of Sinus Perforation with Flaplessly Placed Mini Dental Implants for Oral Rehabilitation: A 5-Year Clinical and Radiological Follow-Up.

Background: Flaplessly placed one-piece mini dental implants (MDI) are an option to support maxillary overdentures. Evenly distribution of the implants over the atrophic alveolar process implies a risk of accidental sinus perforation in the posterior area which could induce sinus-related pathology. Methods: Thirty-one patients received 5–6 maxillary MDIs. Schneiderian membrane swelling was assessed with CBCT at the deepest point of the sinus in the mid-sagittal plane prior to surgery (baseline), after 2 and 5 years. Additionally, subjective patient-reported rhinosinusitis complaints, the effect of smoking, and gender differences were investigated. Results: Mean thickness of the Schneiderian membrane was 2.87 mm at baseline, 3.15 mm at 2 years, and 4.30 mm at 5 years in 27 of 31 initially treated patients. MDI perforation was detected in 21/54 sinuses. At 2 years, perforation length does not affect membrane thickness whereas baseline swelling does. In smokers, each perforated mm induced 0.87 mm additional swelling. After 5 years, the effect of baseline swelling becomes smaller whereas perforation length became statistically significant, with 0.53 mm increase for every perforated mm. The effect of smoking lost its significance. No relations between gender, membrane thickness changes, or subjective clinical sinus complaints and MDI perforation were found. Conclusion: Accidental MDI sinus perforation induces Schneiderian membrane swelling but does not interfere with clinical sinusal outcome after 5 years.

Responses of Sinus Membrane and Antral Pseudocyst Following Lateral Window Sinus Augmentation with Bone Grafting: A Retrospective Study.

To investigate the influence of lateral window sinus augmentation on sinus physiology, including sinus membrane thickness and the outcome of antral pseudocysts. This retrospective study was performed by reviewing all lateral window sinus augmentation procedures, which were done between the years 2013 and 2015. Each enrolled patient had CBCT images preoperatively (T0), immediately postoperatively (T1), and 6 months postoperatively (T2). The sinus membrane thickness, pseudocyst dimensions, and intraoperative perforation were evaluated. Patient-related factors such as age and sex that could influence the mucosal properties were also analyzed. Based on established inclusion criteria, 306 patients with 320 sinuses were included in this study. The overall mean thickness of the sinus membrane (T0) was 1.30 ± 1.08 mm, and membrane thickening (> 2 mm) was observed in 22.19% of the sinuses. Preexisting pseudocysts were identified in 24 sinuses (7.50%), most of which remained unchanged or disappeared after 6 months. The intraoperative membrane perforation rate was lowest (1.96%) when the membrane thickness was 1.0 to 1.5 mm, and the perforation rate was increased in patients with thickened (> 2 mm) or thinned (≤ 1 mm) membrane. Membranes swelled immediately after operation (T1 vs T0, P < .01) and gradually recovered at 6 months. No significant change in membrane thickness was shown after the sinus augmentation procedure in the perforation group and pseudocyst group. The mean thickness of the sinus membrane at T0 and T1 was significantly higher for male subjects (P < .01). Lateral window sinus augmentation has little or no impact on sinus membrane thickness and antral pseudocysts after a 6-month healing period, except for a transient mild membrane swelling. Thickened and thinned membrane were risk factors for intraoperative perforation. Small-sized perforation and pseudocysts might not contraindicate sinus augmentation from the standpoint of the surgical impact on the sinus membrane.

Sinus Mucosa Thickness Changes and Ostium Involvement after Maxillary Sinus Floor Elevation in Sinus with Septa. A Cone Beam Computed Tomography Study.

Background: A thickening of the sinus mucosa is observed after sinus floor augmentation. The objective of this retrospective study was to evaluate the influence of the presence of septa in the dimensional variation and ostium involvement over time of the Schneiderian mucosa after sinus floor augmentation. Materials and Methods: Fifteen sinuses with septa (septa group) and 15 without (control group) were selected. CBCTs taken before surgery, and were analyzed after 1 week and after 9 months. Schneiderian membrane thickness changes over time and involvement of the ostium were evaluated. Results: Four perforations occurred in the septa group and none in the control group. After 1 week of healing, the sinus mucosa thickness increased in height by 5.7 mm and 7.1 mm in the septa and control groups, respectively. In this period, the patency of the ostium decreased in both groups, and three infundibula were obstructed in the septa group, and five in the control group. The mucosa was thicker and the edema was closer to the ostium in the control compared to in the septa group. After 9 months of healing, the dimensions regressed to normal pattern and no obstruction of the infundibula were observed. No statistically significant differences were found between septa and control groups. Conclusions: after one week of healing, the sinus mucosa increased in dimensions in both septa and control groups. However, the sinus mucosa presented a tendency of being thicker and closer to the ostium, resulting in a higher number of infundibula obstructions, in the control group compared to in the septa group. After 9 months, the sinus mucosa regressed to normal dimensions and no obstructions of the infundibula were observed in any group.

Effect of ridge preservation at molar extraction sites with severe periodontitis on the Schneiderian membrane thickness changes: a pilot study

BackgroundInformation regarding the reaction of bone augmentation in terms to sinus mucosa thickness of periodontally compromised molar extraction sites is limited. This retrospective study aimed to analyze the effect of ridge preservation procedures following the extraction of molars with severe periodontitis on the healing pattern of adjacent maxillary sinus mucosal membranes.MethodsThirty-one periodontally compromised maxillary molar teeth either receiving ridge preservation (test group, n = 20) or undergoing spontaneous healing (control group, n = 11) were investigated. Cone-beam computed tomography (CBCT) scanning was performed before the extraction procedure and repeated 6 months later. The mucosa thickness (MT) of the adjacent periodontally compromised molar tooth was measured from CBCT images before tooth extraction and after 6 months of healing at nine assigned measurement points. The data were analyzed at α = 0.05.ResultsThe prevalence of pre-extraction maxillary sinus mucosal thickening was 60.0% and 63.6% in the test and control groups, respectively. The average MT of the thickened sinus mucosa before tooth extraction was 3.78 ± 2.36 mm in the test group and 4.63 ± 3.20 mm in the control group (P = 0.063). The mean mucosal thickening reductions in the thickened MT subjects after 6 months of healing were 2.20 ± 2.05 mm (test group) and 2.64 ± 2.70 mm (control group), P = 0.289. The differences of MT between the time prior to extraction and after 6 months of healing were statistically significant within both groups (P < 0.05).ConclusionsFollowing extraction of molars with severe periodontitis, a reduction in swelling of the Schneiderian membrane has been observed regardless of the addition of a DBBM socket graft. However, a mucosal thickness > 2 mm was still frequently observed.

Investigation of long term drift of an intraocular pressure sensor

“Zero drift” behavior of an optical intraocular pressure sensor is studied using an analytical model based on the deflection of a circular membrane. Results from the analytical model were verified with experimental results from “bulge” testing. The analytical model was used to study the zero drift of the sensor as a function of changes in membrane thickness, geometry of the sensor and amount of gas inside the cavity of the sensor. The results show that dissolution of the membrane, swelling of the spacer layer and oxidative aging can contribute significantly to zero drift of the sensor over time. The results are useful in guiding design and fabrication optimization to minimize drift in intraocular pressure sensors used for long term implantation.

Membrane Thinning Induces Sorting of Lipids and the Amphipathic Lipid Packing Sensor (ALPS) Protein Motif.

Heterogeneities (e.g., membrane proteins and lipid domains) and deformations (e.g., highly curved membrane regions) in biological lipid membranes cause lipid packing defects that may trigger functional sorting of lipids and membrane-associated proteins. To study these phenomena in a controlled and efficient way within molecular simulations, we developed an external field protocol that artificially enhances packing defects in lipid membranes by enforcing local thinning of a flat membrane region. For varying lipid compositions, we observed strong thinning-induced depletion or enrichment, depending on the lipid's intrinsic shape and its effect on a membrane's elastic modulus. In particular, polyunsaturated and lysolipids are strongly attracted to regions high in packing defects, whereas phosphatidylethanolamine (PE) lipids and cholesterol are strongly repelled from it. Our results indicate that externally imposed changes in membrane thickness, area, and curvature are underpinned by shared membrane elastic principles. The observed sorting toward the thinner membrane region is in line with the sorting expected for a positively curved membrane region. Furthermore, we have demonstrated that the amphipathic lipid packing sensor (ALPS) protein motif, a known curvature and packing defect sensor, is effectively attracted to thinner membrane regions. By extracting the force that drives amphipathic molecules toward the thinner region, our thinning protocol can directly quantify and score the lipid packing sensing of different amphipathic molecules. In this way, our protocol paves the way toward high-throughput exploration of potential defect- and curvature-sensing motifs, making it a valuable addition to the molecular simulation toolbox.

Chiral supramolecular architecture of stable transmembrane pores formed by an \u03b1-helical antibiotic peptide in the presence of lyso-lipids

The amphipathic α-helical antimicrobial peptide MSI-103 (aka KIA21) can form stable transmembrane pores when the bilayer takes on a positive spontaneous curvature, e.g. by the addition of lyso-lipids. Solid-state 31P- and 15N-NMR demonstrated an enrichment of lyso-lipids in these toroidal wormholes. Anionic lyso-lipids provided additional stabilization by electrostatic interactions with the cationic peptides. The remaining lipid matrix did not affect the nature of the pore, as peptides maintained the same orientation independent of lipid charge, and a change in membrane thickness did not considerably affect their tilt angle. Under optimized conditions (i.e. in the presence of lyso-lipids and appropriate bilayer thickness), stable and well-aligned pores could be obtained for solid-state 2H-NMR analysis. These data revealed for the first time the complete 3D alignment of this representative amphiphilic peptide in fluid membranes, which is compatible with either monomeric helices as constituents, or left-handed supercoiled dimers as building blocks from which the overall toroidal wormhole is assembled.

Determination of a Biological Hydrophobicity Scale for SecA- Guided Insertion of Single-Span Membrane Proteins

We have used a single-span MalE/RodZ chimeric protein to determine the stability of single-span transmembrane segments (H-segments). The constructs consist of a fusion of preMalE, an engineered H-segment, and the RodZ periplasmic domain. If the H-segment has a low hydrophobicity (e.g. A17) ∼ 90% of the protein is secreted into the periplasm; if the H-segment is moderately greasy (e.g. A13L4 or A27) it is 50% secreted and 50% membrane inserted; if the H-segment has a high hydrophobicity (e.g. L16 or L24) the whole protein is membrane-incorporated. Using the preMalE/RodZ chimera with a moderately greasy H-segment (A27, A17, L9, and L7) in which the center position is successively replaced by all the natural amino acids, we determined an in vivo hydrophobicity scale (ΔGapp). Moderately hydrophobic H-segments are targeted to the membrane by SecA via the first-occurring signal sequence and inserted, but subsequently cleaved by GlpG. ΔGapp values were obtained by comparing the ratio of full-length (secreted) protein to GlpG-cleaved protein (membrane incorporated) for each amino acid. The topologies were confirmed by proteinase K digestion of spheroplast preparations using a GlpG− strain. Interestingly, we observed a significant change in membrane incorporation efficiency based on the E. coli growth temperature (24°, 30°, or 37°C). We hypothesize that this phenomenon is caused by changes in membrane thickness resulting from changes in inner-membrane lipid composition.

The Influence of Lipid Tail Composition on Bid-Mediated Bax Pore Formation

Physical membrane properties are known to influence the function of proteins interacting with lipid bilayers. In the particular case of mitochondrial outer membrane permeabilization by the protein Bax, it is thought that modifications of membrane properties due to, for example, cholesterol overload or lipid oxidation, might have a crucial influence on the process in cells. But what are the physical reasons behind this influence? In this paper, we examine the role of lipid tail composition in mediating the Bax pore formation process when activated by cleaved Bid. We use different fluorescence methods and a reconstituted system to assess this role on different steps in the process. In complement, we use x-ray scattering and molecular dynamics simulations to evaluate the change in membrane thickness and order with change in lipid tail composition. We show that there is an ideal membrane thickness for Bax pore formation. We also show that lipid disorder is crucial in order to allow for both Bid and Bax insertion into the membrane and for their activation, and therefore pore formation.

Use of a micro-porous membrane multi-tubular fixed-bed reactor for tri-reforming of methane to syngas: CO2, H2O or O2 side-feeding

A one-dimensional heterogeneous model for four configurations of a reactor, three micro-porous membrane reactors with O2 (O-MMTR), CO2 (C-MMTR) or H2O (H-MMTR) side-feeding strategy and one traditional reactor (i.e., multi-tubular fixed-bed reactor (MTR)), was developed to explain tri-reforming of methane to produce syngas. Effect of various side-feeding strategies on reactor performance containing CH4 and CO2 conversion, H2/CO ratio, and H2 yield was investigated under the same condition and then described by chemical species and temperature profiles. It was found that use of side-feeding strategies could be feasible, beneficial, and flexible in terms of change in membrane thickness and shell-side pressure for syngas production with H2/CO = 2 which is proper for methanol and Fischer-Tropsch process, and = 1.2 which is suitable for DME direct synthesis. However, the syngas produced by the MTR is only appropriate for the methanol and Fischer-Tropsch synthesis under the base case conditions. Also, the results show that the micro-porous membrane reactors have higher CO2 conversion, based on the H2/CO = 1.2; so these strategies are more environmentally friendly compared to the traditional reactor.

Study of G-Protein Coupled Receptor Signaling in Membrane Environment by Plasmon Waveguide Resonance.

Here we describe an experimental technique, termed plasmon waveguide resonance (PWR) spectroscopy that enables the characterization of molecular interactions occurring at the level of anisotropic thin films as lipid membranes and therein inserted or interacting molecules. PWR allows one to characterize such molecular interactions at different levels: (1) acquire binding curves and calculate dissociation constants; (2) obtain kinetic information; (3) obtain information about associated anisotropy changes and changes in membrane thickness; (4) obtain insight about lateral homogeneity (formation of domains). Points 1, 2, and 4 can be directly obtained from the data. Point 3 requires spectral fitting procedures so that the different optical parameters characterizing thin films as proteolipid membranes, namely refractive index and extinction coefficient for both p- (TM component of light that is parallel to the incident light) and s- (TE component of light that is perpendicular to the incident light) polarizations and thickness, can be determined. When applied to membrane proteins as the G-protein coupled receptor (GPCR) family, both ligand-induced conformational changes of the receptor can be followed as well as interactions with effectors (e.g., G-proteins). Additionally, by either altering the lipid composition in cellular membranes or specifically controlling its composition in the case of lipid model membranes with reconstituted proteins, the role of the lipid environment in receptor activation and signaling can be determined. Additionally, the eventual partition of receptors in different lipid microdomains (e.g., lipid rafts) can be followed. Such information can be obtained ex cellulo with mammalian cell membrane fragments expressing the protein of interest and/or in vitro with lipid model systems where the protein under investigation has been reconstituted. Moreover, PWR can also be applied to directly follow the reconstitution of membrane proteins in lipid model membranes. The measurements are performed directly (no labeling of molecular partners), in real time and with very high sensitivity. Here we will discuss different aspects of GPCR activation and signaling where PWR brought important information in parallel with other approaches. The utility of PWR is not limited to GPCRs but can be applied to any membrane protein. PWR is also an excellent tool to characterize the interaction of membrane active molecules (as cell penetrating, antimicrobial, viral and amyloid peptides) with lipids. A brief section is dedicated to such applications, with particular emphasis on amyloid peptides. To finalize, as PWR is a homemade technology, ongoing instrument developments aiming at breaking current experimental limitations are briefly discussed, namely, the coupling of PWR with electrochemical measurements and the expansion of measurements from the visible to the infrared region.

Long-term Schneiderian membrane thickness changes following zygomatic implant placement: A retrospective radiographic analysis using cone beam computed tomography.

The purpose of this retrospective study was to evaluate the long-term changes in the thickness of Schneiderian membranes after zygomatic implant placement using cone beam computed tomography (CBCT). Twenty-five consecutive patients were included in this study. All the patients underwent bilateral zygomatic implant placement. Schneiderian membrane thickness (SMT) in 49 maxillary sinuses (one sinus was not included because of early loss of the zygomatic implants) was measured using CBCT before and at least 1year after zygomatic implant placement. Ostium patency of each sinus was also evaluated and recorded. In total, 84 zygomatic implants and 30 regular implants were placed in included patients. Two unilateral maxillary zygomatic implants in one patient were removed 2months after implant placement. The SMT increased from 1.03mm (inter-quartile range: 1.57mm) to 1.33mm (inter-quartile range: 1.98mm) after a median follow-up time of 23.00months (inter-quartile range: 14months), and the difference was statistically significant. Before zygomatic implant insertion, 24.5% (12/49) of sinuses had SMT greater than 2mm, whereas this value was 28.6% (14/49) after zygomatic implant placement. The percentage of sinuses observed with ostium patency also increased from 2.0% (1/49) to 12.2% (6/49). Chronic Schneiderian membrane thickening could result from zygomatic implant insertion. Intensive postoperative care and clinical and radiographic monitoring are recommended after zygomatic implant placement.

Investigation on uric acid biosensor model for enzyme layer thickness for the application of arthritis disease diagnosis.

Uric acid biosensors for arthritis disease has been developed for the specific selection of uricase enzyme film thickness coated over the TiO2-CeO2 nano-composite matrix is modelled mathematically. This model is purely based on R-diffusion conditions with irreversible first-order catalytic reactions. By arithmetical method, the impact of the thickness of enzyme layer on the current response of the biosensor was explored. This article displays a structure for choice of the enzyme layer thickness, guaranteeing the adequately stable sensitivity of a biosensor in a required extent of the maximal enzymatic rate. The numerical outcomes showed subjective and sensible quantitative information for oxidation current due to uric acid also shows the maximum change in the biosensor current response due to the change in membrane thickness, which will be more suitable for uric acid biosensor for the application of arthritis disease diagnosis.

Multilamellar-to-Unilamellar Transition Induced by Diphenylalanine in Lipid Vesicles

In the present work, we investigate the effect of two short phenylalanine-based peptides on lipid membranes. A simplified model membrane composed of lecithin vesicles was used to incorporate different amounts of the two amino acid sequences, the dimmer l,l-diphenylallanine (FF) and the trimmer cysteine-diphenylallanine (CFF). Spectroscopic and scattering techniques were applied to probe in detail the structural behavior of lipid membranes in the presence of the peptides. The experimental results demonstrate that both peptides are located mainly at the interface of the membrane interacting with phosphate groups modifying membrane thickness and flexibility. The multilamellar structure of the vesicles is preserved with inclusion of small amounts of FF, accompanied by changes in membrane thickness and elasticity. Finally, a multi- to unilamellar transition is observed as a result of peptide self-association into a crystalline structure onto the membrane interface.