Scanning ion conductance microscopy reveals differential effect of PM2.5 exposure on A549 lung epithelial and SH-SY5Y neuroblastoma cell membranes.

Numerous studies have linked a wide range of diseases including respiratory illnesses to harmful particulate matter (PM) emissions indoors and outdoors, such as incense PM and industrial PM. Because of their ability to penetrate the lower respiratory tract and the circulatory system, fine particles with diameters of 2.5 µm or less (PM2.5) are believed to be more hazardous than larger PMs. Despite the enormous number of studies focusing on the intracellular processes associated with PM2.5 exposure, there have been limited reports studying the biophysical properties of cell membranes, such as nanoscale morphological changes induced by PM2.5. Our study assesses the membrane topographical and structural effects of PM2.5 from incense PM2.5 exposure in real time on A549 lung carcinoma epithelial cells and SH-SY5Y neuroblastoma cells that had been fixed to preclude adaptive cell responses. The size distribution and mechanical properties of the PM2.5 sample were characterized with atomic force microscopy (AFM). Nanoscale morphological monitoring of the cell membranes utilizing scanning ion conductance microscopy (SICM) indicated statistically significant increasing membrane roughness at A549 cells at half an hour of exposure and visible damage at 4 h of exposure. In contrast, no significant increase in roughness was observed on SH-SY5Y cells after half an hour of PM2.5 exposure, although continued exposure to PM2.5 for up to 4 h affected an expansion of lesions already present before exposure commenced. These findings suggest that A549 cell membranes are more susceptible to structural damage by PM2.5 compared to SH-SY5Y cell membranes, corroborating more enhanced susceptibility of airway epithelial cells to exposure to PM2.5 than neuronal cells.

pH-Responsive Metal-Organic Framework Thin Film for Drug Delivery.

In this work, surface-supportive MIL-88B(Fe) was explored as a pH-stimuli thin film to release ibuprofen as a model drug. We used surface plasmon resonance microscopy to study the pH-responsive behaviors of MIL-88B(Fe) film in real time. A dissociation constant of (6.10 ± 0.86) × 10-3 s-1 was measured for the MIL-88B(Fe) film in an acidic condition (pH 6.3), which is about 10 times higher than the dissociation of the same film in a neutral pH condition. MIL-88B(Fe) films are also capable of loading around 6.0 µg/cm2 of ibuprofen, which was measured using a quartz crystal microbalance (QCM). Drug release profiles were compared in both acidic and neutral pH conditions (pH 6.3 and 7.4) using a QCM cell to model the drug release in healthy body systems and those containing inflammatory tissues or cancerous tumors. It was found that the amount of drug released in acidic environments had been significantly higher compared to that in a neutral system within 55 h of testing time. The pH-sensitive chemical bond breaking between Fe3+ and the carboxylate ligands is the leading cause of drug release in acidic conditions. This work exhibits the potential of using MOF thin films as pH-triggered drug delivery systems.

Observation of α-Synuclein Preformed Fibrils Interacting with SH-SY5Y Neuroblastoma Cell Membranes Using Scanning Ion Conductance Microscopy.

Parkinson's disease (PD) is the second-most prevalent neurodegenerative disorder in the U.S. α-Synuclein (α-Syn) preformed fibrils (PFFs) have been shown to propagate PD pathology in neuronal populations. However, little work has directly characterized the morphological changes on membranes associated with α-Syn PFFs at a cellular level. Scanning ion conductance microscopy (SICM) is a noninvasive in situ cell imaging technique and therefore uniquely advantageous to investigate PFF-induced membrane changes in neuroblastoma cells. The present work used SICM to monitor cytoplasmic membrane changes of SH-SY5Y neuroblastoma cells after incubation with varying concentrations of α-Syn PFFs. Cell membrane roughness significantly increased as the concentration of α-Syn PFFs increased. Noticeable protrusions that assumed a more crystalline appearance at higher α-Syn PFF concentrations were also observed. Cell viability was only slightly reduced, though statistically significantly, to about 80% but independent of the dose. These observations indicate that within the 48 h treatment period, PFFs continue to accumulate on the cell membranes, leading to membrane roughness increase without causing prominent cell death. Since PFFs did not induce major cell death, these data suggest that early interventions targeting fibrils before further aggregation may prevent the progression of neuron loss in Parkinson's disease.

Plasmonic Imaging of Electrochemical Reactions at Individual Prussian Blue Nanoparticles.

Prussian blue is an iron-cyanide-based pigment steadily becoming a widely used electrochemical sensor in detecting hydrogen peroxide at low concentration levels. Prussian blue nanoparticles (PBNPs) have been extensively studied using traditional ensemble methods, which only provide averaged information. Investigating PBNPs at a single entity level is paramount for correlating the electrochemical activities to particle structures and will shed light on the major factors governing the catalyst activity of these nanoparticles. Here we report on using plasmonic electrochemical microscopy (PEM) to study the electrochemistry of PBNPs at the individual nanoparticle level. First, two types of PBNPs were synthesized; type I synthesized with double precursors method and type II synthesized with polyvinylpyrrolidone (PVP) assisted single precursor method. Second, both PBNPs types were compared on their electrochemical reduction to form Prussian white, and the effect from the different particle structures was investigated. Type I PBNPs provided better PEM sensitivity and were used to study the catalytic reduction of hydrogen peroxide. Progressively decreasing plasmonic signals with respect to increasing hydrogen peroxide concentration were observed, demonstrating the capability of sensing hydrogen peroxide at a single nanoparticle level utilizing this optical imaging technique.

Plasmonic Imaging of Oxidation and Reduction of Single Gold Nanoparticles and Their Surface Structural Dynamics.

Gold nanoparticles (AuNPs) have been widely used in catalytic electrochemistry. Heterogeneity in size, shape, and surface sites leads to variable, particle-specific catalytic activities. Conventional electrochemical methods can only obtain the collective responses from all the catalytic nanoparticles on the electrode surface; the heterogeneity of particle performance will be averaged. Alternatively, plasmonic electrochemical imaging (PECi) is capable of imaging the electrochemical activity at individual nanoparticles. In this work, PECi was used to image the oxidation and reduction of the gold surface at individual AuNPs, and their associated structural alterations were successfully measured. We have studied the electrochemical responses from gold nanocubes, gold nanorods, and gold nanowires with PECi and observed different surface redox activities. We have also demonstrated the capability of monitoring the surface dynamics at individual AuNPs utilizing characteristic PECi derived cyclic voltammograms (CVs).