Interactions of Graphene Oxide with Model Cell Membranes: Probing Nanoparticle Attachment and Lipid Bilayer Disruption

With the rapid growth in the application of graphene oxide (GO) in diverse fields, the toxicity of GO toward bacterial and mammalian cells has recently attracted extensive research attention. While several mechanisms have been proposed for the cytotoxicity of GO, the attachment of GO to cell membranes is expected to be the key initial process that precedes these mechanisms. In this study, we investigate the propensity for GO to attach to and disrupt model cell membranes using supported lipid bilayers (SLBs) and supported vesicular layers (SVLs) that are composed of zwitterionic 1,2-dioleoyl-<i>sn</i>-glycero-3-phosphocholine (DOPC). The deposition kinetics of GO on SLBs were determined using quartz crystal microbalance with dissipation monitoring and were observed to increase with increasing electrolyte (NaCl and CaCl₂) concentrations, indicating that GO attachment to SLBs was controlled by electrostatic interactions. The GO deposition kinetics measured at elevated electrolyte concentrations were lower than mass-transfer-limited kinetics, likely due to the presence of hydration forces between GO and SLBs. Upon the attachment of GO to supported vesicles that were encapsulated with a fluorescent dye, dye leakage was detected, thus indicating that the lipid vesicles were disrupted. When the exposure of the SVL to the GO suspension was terminated, the leakage of dye decreased significantly, demonstrating that the pores on the lipid bilayers have a self-healing ability

Probing the Affinity of Coronavirus with Contact Surfaces in Simulated Body Fluids

Transmission of viral pathogens has raised serious public health concerns, but the affinity and strength of viruses adhering to high-touch surfaces are not clear. We systematically investigated the propensities of a coronavirus, Murine hepatitis virus A59 (MHV), adhering onto and releasing from four representative contact surfaces, silica, stainless steel, cellulose, and polystyrene, in simulated saliva and urine using quartz crystal microbalance with dissipation monitoring (QCM-D). We also quantified the interactions between MHV and contact surfaces using atomic force microscopy (AFM). Both initial adhesion rates and saturated adhesion mass of MHV were higher in urine buffer than in saliva buffer, which is attributed to the higher repulsions between the virus and surfaces in the presence of mucin. The maximum adhesion mass of MHV follows the order of stainless steel > silica > cellulose ≈ polystyrene in both urine and saliva buffers. Stainless steel and silica are surfaces with likely higher risks of virus contamination due to their highest maximum adhesion mass in both urine and saliva buffers and lower virus release percentages upon water rinse. The results of this study will provide insights into risk assessment and control of pathogens associated with contact surfaces

Enhanced Removal of Fluoride by Polystyrene Anion Exchanger Supported Hydrous Zirconium Oxide Nanoparticles

Here we fabricated a novel nanocomposite HZO-201, an encapsulated nanosized hydrous zirconium oxide (HZO) within a commercial porous polystyrene anion exchanger D201, for highly efficient defluoridation of water. HZO-201 exhibited much higher preference than activated alumina and D201 toward fluoride removal when competing anions (chloride, sulfate, nitrate, and bicarbonate) coexisted at relatively high levels. Fixed column adsorption indicated that the effective treatable volume of water with HZO-201 was about 7–14 times as much as with D201 irrespective of whether synthetic solution or groundwater was the feeding solution. In addition, HZO-201 could treat >3000 BV of the acidic effluent (around 3.5 mg F^–/L) per run at pH 3.5, compared to only ∼4 BV with D201. The exhausted HZO-201 could be regenerated by NaOH solution for repeated use without any significant capacity loss. Such attractive performance of HZO-201 resulted from its specific hybrid structure, that is, the host anion exchanger D201 favors the preconcentration of fluoride ions inside the polymer based on the Donnan principle, and the encapsulated nanosized HZO exhibits preferable sequestration of fluoride through specific interaction, as further demonstrated by XPS spectra. The influence of solution pH, competitive anions, and contact time was also examined. The results suggested that HZO-201 has a great potential in efficient defluoridation of groundwater and acidic mine drainage

Influence of Solution Chemistry and Soft Protein Coronas on the Interactions of Silver Nanoparticles with Model Biological Membranes

The influence of solution chemistry and soft protein coronas on the interactions between citrate-coated silver nanoparticles (AgNPs) and model biological membranes was investigated by assembling supported lipid bilayers (SLBs) composed of zwitterionic 1,2-dioleoyl-<i>sn</i>-glycero-3-phosphocholine (DOPC) on silica crystal sensors in a quartz crystal microbalance with dissipation monitoring (QCM-D). Our results show that the deposition rates of AgNPs on unmodified silica surfaces increased with increasing electrolyte concentrations under neutral pH conditions. Similar trends were observed when AgNPs were deposited on SLBs, hence indicating that the deposition of AgNPs on model cell membranes was controlled by electrostatic interactions. In the presence of human serum albumin (HSA) proteins at both pH 7 and pH 2, the colloidal stability of AgNPs was considerably enhanced due to the formation of HSA soft coronas surrounding the nanoparticles. At pH 7, the deposition of AgNPs on SLBs was suppressed in the presence of HSA due to steric repulsion between HSA-modified AgNPs and SLBs. In contrast, pronounced deposition of HSA-modified AgNPs on SLBs was observed at pH 2. This observation was attributed to the reduction of electrostatic repulsion as well as conformation changes of adsorbed HSA under low pH conditions, resulting in the decrease of steric repulsion between AgNPs and SLBs

Correction to Diketone-Mediated Photochemical Processes for Target-Selective Degradation of Dye Pollutants

Correction to Diketone-Mediated Photochemical Processes for Target-Selective Degradation of Dye Pollutant