NANOPARTICLE-CELL MEMBRANE INTERACTIONS: ADSORPTION KINETICS AND THE MONOLAYER RESPONSE

The fast-growing production and utilization of nanomaterials in diverse applications will undoubtedly lead to the release of these materials into the environment. As nanomaterials enter the environment, determining their interaction with biological systems is a key aspect to understanding their impact on environmental health and safety. It has been shown that engineered nanoparticles (ENPs) can interact with cell membranes by adhering onto their surface and compromising their integrity, permeability, and function. The interfacial and biophysical forces that drive these processes can be examined using lipid monolayers or bilayers as model cell membranes. Interfacial interactions between NPs and cell membranes have been proven to be affected by various parameters such as the physicochemical properties of the NPs, cell membrane composition, and the extent of exposure. This study focuses on the effects of NP charge, surface functional groups and interfacial activity on the response of lipid monolayers. Dynamic surface pressure measurements were used to examine the kinetics of nanoparticle adsorption and the monolayer response. Fluorescence and real-time in situ Brewster angle microscopy (BAM) imaging were employed to characterize the morphology and structure of the monolayers. Bulk concentrations of NP and phosphorus were examined to determine the extent of NP binding and lipid extraction. The results of this study will contribute to further understanding of the membrane’s role in ENP cytotoxicity and cellular uptake and aid the design of biocompatible nanomaterials with minimal or controlled membrane activity

Albumin protein coronas render nanoparticles surface active: consonant interactions at air–water and at lipid monolayer interfaces

Protein coronas are known to alter the physicochemical properties, colloidal stability, and biological fate of nanoparticles. Using human serum albumin (HSA) and polystyrene nanoparticles (NPs) with anionic or cationic surface chemistries, we show that protein coronas also govern the surface activity of PS nanoparticles as well as their interactions with a model red blood cell (RBC) lipid monolayer. The adsorption kinetics of bare nanoparticles (no corona) and nanoparticles with a hard corona (HC) at an air–water interface were well-described theoretically, which revealed that the adsorption energy was greater with the corona due to hydrophobic interactions that were enhanced with protein restructuring. Corona complexation increased the concentration of nanoparticles at the interface and led to the formation of interfacial aggregates. Despite clear differences in monolayer structure, the compressibility of PS–HC monolayers was similar to free HSA, indicating that conformational changes associated with the protein were not restricted in a hard corona. The intrinsic behavior of the proteins driving the surface activity and compressibility of the complexes at an air–water interface was also observed at an air–lipid (RBC)–water interface. In this case the lipid monolayer acted as a barrier and reduced the interface concentration of bare nanoparticles. However, with a corona the nanoparticles penetrated into the monolayer and led to the formation of NP–HC–lipid ‘pillars’ that extended into air. Our results suggest that nanoparticle surface activity, and changes in surface activity due to corona formation, are insightful parameters to predicting nanoparticle–membrane interactions, complementing the conventional view that electrostatic forces are dominant

Artifact-Robust Graph-Based Learning in Digital Pathology

Whole slide images~(WSIs) are digitized images of tissues placed in glass slides using advanced scanners. The digital processing of WSIs is challenging as they are gigapixel images and stored in multi-resolution format. A common challenge with WSIs is that perturbations/artifacts are inevitable during storing the glass slides and digitizing them. These perturbations include motion, which often arises from slide movement during placement, and changes in hue and brightness due to variations in staining chemicals and the quality of digitizing scanners. In this work, a novel robust learning approach to account for these artifacts is presented. Due to the size and resolution of WSIs and to account for neighborhood information, graph-based methods are called for. We use graph convolutional network~(GCN) to extract features from the graph representing WSI. Through a denoiser {and pooling layer}, the effects of perturbations in WSIs are controlled and the output is followed by a transformer for the classification of different grades of prostate cancer. To compare the efficacy of the proposed approach, the model without denoiser is trained and tested with WSIs without any perturbation and then different perturbations are introduced in WSIs and passed through the network with the denoiser. The accuracy and kappa scores of the proposed model with prostate cancer dataset compared with non-robust algorithms show significant improvement in cancer diagnosis

Surface Activity of Poly(ethylene glycol)-Coated Silver Nanoparticles in the Presence of a Lipid Monolayer

We have investigated the surface activity of poly(ethylene glycol) (PEG)-coated silver nanoparticles (Ag-PEG) in the presence or absence of lipid monolayers comprised of monounsaturated dioleoylphosphocholine and dioleoylphosphoglycerol (DOPC/DOPG; 1:1 mol ratio). Dynamic measurements of surface pressure demonstrated that Ag-PEG were surface-active at the air/water interface. Surface excess concentrations suggested that at high Ag-PEG subphase concentrations, Ag-PEG assembled as densely packed monolayers in the presence and absence of a lipid monolayer. The presence of a lipid monolayer led to only a slight decrease in the excess surface concentration of Ag-PEG. Surface pressure–area isotherms showed that in the absence of lipids Ag-PEG increased the surface pressure up to 45 mN m–1 upon compression before the Ag-PEG surface layer collapsed. Our results suggest that surface activity of Ag-PEG was due to hydrophobic interactions imparted by a combination of the amphiphilic polymer coating and the hydrophobic dodecanethiol ligands bound to the Ag-PEG surface. With lipid present, Ag-PEG + lipid surface pressure–area (π–A) isotherms reflected Ag-PEG incorporation within the lipid monolayers. At high Ag-PEG concentrations, the π–A isotherms of the Ag-PEG + lipid films closely resembled that of Ag-PEG alone with a minimal contribution from the lipids present. Analysis of the subphase silver (Ag) and phosphorus (P) concentrations revealed that most of the adsorbed material remained at the air/lipid/water interface and was not forced into the aqueous subphase upon compression, confirming the presence of a composite Ag-PEG + lipid film. While interactions between “water-soluble” nanoparticles and lipids are often considered to be dominated by electrostatic interactions, these results provide further evidence that the amphiphilic character of a nanoparticle coating can also play a significant role

A Comparative Study of Enamel Surface Roughness after Bleaching with Diode Laser and Nd: YAG Laser

Introduction: Bleaching process can affect surface roughness of enamel, which is a vital factor in esthetic and resistance of tooth. The aim of this study was to compare surface roughness of enamel in teeth bleached using Diode and Neodymium-Doped Yttrium Aluminium Garnet (Nd: YAG) lasers with those bleached using conventional method.Methods: In this study, 75 anterior human teeth from upper and lower jaws were randomly divided into 5 groups. Group 1: Laser white gel (Biolase, USA) with 45% hydrogen peroxide concentration and GaAlAs Diode laser (CHEESETM, GIGAA, China), group 2: Heydent gel (JW, Germany) with 30% Hydrogen peroxide concentration and Diode laser, group 3: Laser white gel and Nd:YAG laser (FIDELISTM, Fotona, Slovenia), group 4: Heydent gel and Nd:YAG laser and group 5: The Iranian gel Kimia (Iran) with 35% hydrogen peroxide concentration were used. Surface roughness of the samples was measured using the Surface Roughness Tester system (TR 200 Time Group, Germany) before and after bleaching. In each group, one sample was randomly selected for SEM analysis.Results: The results showed that the mean surface roughness of the teeth before and after bleaching had a significant difference in all the study groups. It was indicated that after bleaching, the mean surface roughness had increased in all the study groups. The highest surface roughness was seen in the conventional bleaching group and the lowest surface roughness was reported in group 3 (laser white gel + diode laser), in which the average surface roughness increased by only 0.1 μm.Conclusion: It was concluded that using the Laser white gel and the diode laser for bleaching resulted in the least surface roughness compared to conventional method

Optimized Er: YAG Laser Irradiation Distance to Achieve the Strongest Bond Strength Between Orthodontic Brackets and Zirconia-Ceramics

Introduction: In recent decades zirconium oxide has been introduced in the field of dentistry as a high-strength ceramic. Unlike its mechanical advantages, however, due to its inert chemical properties, it bonds poorly to other substrates, so improving bonding strength to an adhesive material is necessary.Methods: In this experimental study, 70 ceramic zirconia blocks were prepared and distributed randomly among 7 groups. Then the shear bond strengths were determined and the samples were examined by a scanning electron microscope (SEM). Statistical analysis was performed by one-way ANOVA and multiple Tukey comparisons.Results: One-way analysis of variance (ANOVA) showed that laser irradiation distance has a significant effect on orthodontics brackets bond strength to zirconia-ceramics. Based on the Tukey post hoc test, each group was compared with other groups and the contact mode and 2 mm distance groups showed significantly higher bond strength than other groups (P-value <0.05).Conclusion: Orthodontic bracket bond strength to zirconia-ceramics will be reduced by increasing Er: YAG laser irradiation distance from samples. The highest bond strength will be achieved when the laser irradiation distance is 2 mm or when the laser beam is in contact with samples.

Open Air Direct Oxidative Coupling of Alcohols and Amines to Imines Catalyzed by Ruthenium Nanoclusters Supported on a Mesoporous Carbon (CMK-8) in/on Water

We present a green and efficient protocol for the synthesis of various imines including challenging α,β-unsaturated imines directly from alcohols and amines via a tandem oxidative cross-coupling strategy. The reaction is catalyzed by ruthenium nanoclusters supported on a cubic ordered mesoporous carbon (CMK-8) under ambient air pressure (622 Torr) and mild aqueous conditions without requiring a base or other additives. The catalyst shows excellent activity and selectivity for a broad range of alcohols and amines, giving the desired imines in excellent yield and high purity. The catalyst was characterized by various analytical techniques such as N2 sorption analysis, X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA), high-resolution transmission electron microscopy (TEM), high-angle annular dark-field scanning TEM, and the corresponding elemental mapping. The results revealed that the catalyst has a large surface area, uniform pore size distribution with ordered cubic arrangement, and active Ru species with very small sizes (mostly less than 1 nm), which most likely accounts for its exceptional catalytic performance. Hot filtration and recycling tests demonstrated that the catalyst operated heterogeneously and remained active for at least three cycles

Comparative study between chemostat and batch reactors to quantify membrane permeability changes on bacteria exposed to silver nanoparticles

Continuous and batch reactors were used to assess the effect of the exposure of casein-coated silver nanoparticles (AgNPs) on Escherichia coli (E. coli). Additionally, E. coli membrane extracts, membrane permeability and Langmuir film balance assays were used to determine integrity and changes in lipid composition in response to AgNPs exposure. Results showed that batch conditions were not appropriate for the tests due to the production of exopolymeric substances (EPS) during the growth phase. After 5 h of contact between AgNPs and the used growth media containing EPS, the nanoparticles increased in size from 86 nm to 282 nm reducing the stability and thus limiting cell-nanoparticle interactions. AgNPs reduced E. coli growth by 20% at 1 mg/L, in terms of Optical Density 670 (OD670), while no effect was detected at 15 mg/L. At 50 mg/L of AgNPs was not possible to perform the test due to aggregation and sedimentation of the nanoparticles. Membrane extract assays showed that at 1 mg/L AgNPs had a greater change in area (− 4.4cm2) on bacteria compared to 15 mg/L (− 4.0cm2). This area increment suggested that membrane disruption caused by AgNPs had a stabilizing/rigidifying effect where the cells responded by shifting their lipid composition to more unsaturated lipids to counteract membrane rigidification. In chemostats, the constant inflow of fresh media and aeration resulted in less AgNPs aggregation, thus increased the AgNPs-bacteria interactions, in comparison to batch conditions. AgNPs at 1 mg/L, 15 mg/L, and 50 mg/L inhibited the growth (OD670 reduction) by 0%, 11% and 16.3%, respectively. Membrane extracts exposed to 1 mg/L, 15 mg/L, and 50 mg/L of AgNPs required greater changes in area by − 0.5 cm2, 2.7 cm2 and 3.6 cm2, respectively, indicating that the bacterial membranes were disrupted and bacteria responded by synthesizing lipids that stabilize or strengthen membranes. This study showed that the chemostat is more appropriate for the testing of nanotoxicological effects when testing bacteria at growing conditions