Solution-based Supramolecular Hierarchical Assembly of Frenkel Excitonic Nanotubes Driven by Gold Nanoparticle Formation and Temperature.

Translating nature's successful design principle of solution-based supramolecular self-assembling to broad applications─ranging from renewable energy and information technology to nanomedicine─requires a fundamental understanding of supramolecular hierarchical assembly. Though the forces behind self-assembly (e.g., hydrophobicity) are known, the specific mechanism by which monomers form the hierarchical assembly still remains an open question. A crucial step toward formulating a complete mechanism is understanding not only how the monomer's specific molecular structure but also how manifold environmental conditions impact the self-assembling process. Here, we elucidate the complex correlation between the environmental self-assembling conditions and the resulting structural properties by utilizing a well-characterized model system: well-defined supramolecular Frenkel excitonic nanotubes (NTs), self-assembled from cyanine dye molecules in aqueous solution, which further self-assemble into bundled nanotubes (b-NTs). The NTs and b-NTs inhabit distinct spectroscopic signatures, which allows the use of steady-state absorption spectroscopy to monitor the transition from NTs to b-NTs directly. Specifically, we investigate the impact of temperature (ranging from 23 °C, 55 °C, 70 °C, 85 °C, up to 100 °C) during in situ formation of gold nanoparticles to determine their role in the formation of b-NTs. The considered time regime for the self-assembling process ranges from 1 min to 8 days. With our work, we contribute to a basic understanding of how environmental conditions impact solution-based hierarchical supramolecular self-assembly in both the thermodynamic and the kinetic regime.

Biofilm formation of clinically important microorganisms on 2D and 3D poly (methyl methacrylate) substrates: A surface-enhanced Raman scattering study.

Clinically relevant microorganisms threaten patient's health often through biofilm formation on polymeric medical devices and implants. Poly (methyl methacrylate) is a commonly used polymer in medical implants and dental devices. In this study, biofilm characteristics of model microorganisms, Pseudomonas aeruginosa, Staphylococcus epidermidis and Candida albicans, were investigated at molecular level on 2-dimensional (2D) and 3-dimensional (3D) PMMA substrates to understand the influence of surface structures on biofilm formation and also to demonstrate the discrimination of microorganisms according to their metabolic activities by utilizing surface-enhanced Raman scattering (SERS). It was found that the fibrous 3D structure enhanced the assembly of microorganisms and enriched the biofilm structure while smooth polymeric surface decreased the biofilm formation rate and variety of biofilm content. Among the studied microorganisms, Pseudomonas aeruginosa and Candida albicans had a higher tendency to form biofilm on both 2D and 3D PMMA substrates. Although Staphlylococcus epidermidis showed slow adaption on PMMA surfaces, the 3D porous surfaces increased its biofilm formation rate significantly compared to 2D surface.

Role of modification route for zinc oxide nanoparticles on protein structure and their effects on glioblastoma cells.

Zinc oxide nanoparticles (ZnO) are presented as potential cancer therapeutic agent based on their surface properties. In this study, the most abundant blood proteins, albumin, fibrinogen and apo-transferrin, were covalently bound (c-ZnO NPs) and nonspecifically adsorbed (n-ZnO NPs) onto ZnO NPs to evaluate the role of modification route on protein structure and their effects on glioblastoma cells. The success of modification and structures of proteins on ZnO NPs were characterized with FT-IR. It was found that non-covalent interaction significantly damaged the secondary structure of proteins compared to those covalently attached to the ZnO nanoparticle. The effects of modified ZnO NPs were investigated by evaluating viability, cycle, and death mechanisms of glioblastoma (U373) cells. n-ZnO NPs were found more toxic compared to the pristine and c-ZnO NPs. However, c-ZnO NPs with albumin and apo-transferrin both perturbed the cell cycle function, and decreased the necrotic cell death rate of U373 cells below toxic concentration, suggesting their potential curative effect on glioblastoma cells.

Early Stage Alterations in CA1 Extracellular Region Proteins Indicate Dysregulation of IL6 and Iron Homeostasis in the 5XFAD Alzheimer's Disease Mouse Model.

In recent years, an increasing number of research papers revealed that the compositional and volumetric alterations in the extracellular matrix are the consequences of aging and may be related to Alzheimer's disease (AD). In this study, we aimed to demonstrate the alterations in hippocampal extracellular fluid proteins in vivo using the 5XFAD mouse model. Samples were obtained from hippocampi of 5XFAD mice (n = 6) and their non-transgenic littermates by intracerebral push-pull perfusion technique at 3 months of age, representing the pre-pathological stage of the AD. Proteins in the hippocampal perfusates were analyzed by Ultra Performance Liquid Chromatography-Electrospray Ionization Quadrupole Time-of-Flight Mass Spectrometry (UPLC-ESI-qTOF-MS/MS). 178 proteins were identified and 19 proteins of them were found to be statistically significantly altered (p≤0.05, fold change ≥40%, unique peptide count ≥3) in the hippocampal CA1 extracellular fluid of the 5XFAD mouse model. Ingenuity pathway analysis of the protein expression results identified IL6 as an upstream regulator. The upregulation of IL6 was validated by immunohistochemical staining of the hippocampus and cortex of the 5XFAD mice prior to Aß plaque formation. Furthermore, the iron level in the hippocampus was measured by inductively coupled plasma-mass spectrometry as IL6 is mentioned in several studies to take part in iron homeostasis and inflammation and found to be increased in 5XFAD mice hippocampus. Alterations in extracellular matrix proteins in addition to increasing amount of hippocampal IL6 and iron in the early stages of AD may reveal inflammation-mediated iron dyshomeostasis in the early stages of neurodegeneration.

Understanding and Discrimination of Biofilms of Clinically Relevant Microorganisms Using Surface-Enhanced Raman Scattering.

Biofilm formation is a defense mechanism for microorganisms to survive under both natural and stress conditions. Clinically relevant microorganisms threaten patient health through biofilm formation on medical devices and implants. It is very important to identify biofilm formation in order to suppress their pathogenic activities in early stages. With the aim for better understanding biofilm formation and possibility of detection, in this study, biofilm formation of clinically important microorganisms, Pseudomonas aeruginosa, Staphylococcus epidermidis, and Candida albicans are monitored with surface-enhanced Raman scattering (SERS). The SERS spectra were collected by mapping a dried droplet area where a volume of colloidal silver nanoparticle (AgNP) suspension is placed on microorganism culture plate. The spectral changes on the SERS spectra with increasing incubation time of the model microorganisms from 4 to 120 h are monitored. The unique spectra originating from the biofilms of three pathogenic microorganisms and the spectral changes as a result of time-dependent concentration fluctuations of biomolecular species in their biofilms including carbohydrates, lipids, proteins, and genetic materials allow not only identification but also discrimination of biofilms using principal component analysis.

Source of cytotoxicity in a colloidal silver nanoparticle suspension.

Silver nanoparticles (AgNPs) are increasingly used in a variety of applications because of their potential antimicrobial activity and their plasmonic and conductivity properties. In this study, we investigated the source of cytotoxicity, genotoxicity, and reactive oxygen species (ROS) production on human dermal fibroblast and human lung cancer (A549) cell lines upon exposure to AgNP colloidal suspensions prepared with the simplest and most commonly used Lee­Meisel method with a variety of reaction times and the concentrations of the reducing agent. The AgNPs synthesized with shorter reaction times were more cytotoxic and genotoxic due to the presence of a few nanometer-sized AgNP seeds. The suspensions prepared with an increased citrate concentration were not cytotoxic, but they induced more ROS generation on A549 cells due to the high citrate concentration. The genotoxicity of the suspension decreased significantly at the higher citrate concentrations. The analysis of both transmission electron microscopy images from the dried droplet areas of the colloidal suspensions and toxicity data indicated that the AgNP seeds were the major source of toxicity. The completion of the nucleation step and the formation of larger AgNPs effectively decreased the toxicity.