Amorphous Aggregation of Amyloid Beta 1-40 Peptide in Confined Space.

The amorphous aggregation of Aß1-40 peptide is addressed by using micromolding in capillaries. Both the morphology and the size of the aggregates are modulated by changing the contact angle of the sub-micrometric channel walls. Upon decreasing the hydrophilicity of the channels, the aggregates change their morphology from small aligned drops to discontinuous lines, thereby keeping their amorphous structure. Aß1-40 fibrils are observed at high contact angles.

Applications of dewetting in micro and nanotechnology.

Dewetting is a spontaneous phenomenon where a thin film on a surface ruptures into an ensemble of separated objects, like droplets, stripes, and pillars. Spatial correlations with characteristic distance and object size emerge spontaneously across the whole dewetted area, leading to regular motifs with long-range order. Characteristic length scales depend on film thickness, which is a convenient and robust technological parameter. Dewetting is therefore an attractive paradigm for organizing a material into structures of well-defined micro- or nanometre-size, precisely positioned on a surface, thus avoiding lithographical processes. This tutorial review introduces the reader to the physical-chemical basis of dewetting, shows how the dewetting process can be applied to different functional materials with relevance in technological applications, and highlights the possible strategies to control the length scales of the dewetting process.

Interfacing Polymers and Tissues: Quantitative Local Assessment of the Foreign Body Reaction of Mononuclear Phagocytes to Polymeric Materials.

A quantitative method to assess the in vitro foreign body reaction (FBR) of mononuclear phagocytes (MP) to polymers relevant in implants for prosthetics, advanced therapies, and regenerative medicine is presented. It integrates single-cell force spectroscopy (SCFS) with immunogenic profiles of the MPs. In cell force spectroscopy experiments a single phagocyte, linked at the end of an atomic force microscopy cantilever, probes the adhesion forces between the cell and the polymer surface. SCFS measures adhesion forces in a range from 10 pN to 100 nN and with spatial resolution from cell size down to nanometers, accessing the early adhesion events established at contact times between milliseconds and minutes. The time evolution within the first 60 s of the adhesion force between the phagocyte and the polymer surface before and after the treatment with an immunosuppressive drug, viz. Minocycline, a Federal Drug Administration (FDA)-approved third generation tetracycline with anti-inflammatory effects, is then studied. The adhesion force values measured at the single cell level is shown to correlate to the immunogenic profiles obtained by analysis of biomarkers and morphology of the MPs in culture. Also, Minocycline causes a decrease of both proinflammatory gene expression profiles and adhesive forces of single cells.

Electrical release of dopamine and levodopa mediated by amphiphilic ß-cyclodextrins immobilized on polycrystalline gold.

Vesicles of cationic amphiphilic ß-cyclodextrins have been immobilized on polycrystalline gold by exploiting the chemical affinity between their amino groups and Au atoms. The presence of cyclodextrins has been widely investigated by means of AFM, XPS, kelvin probe and electrochemical measurements. This multi-functional coating confers distinct electrochemical features such as pH-dependent behavior and partial/total blocking properties towards electro-active species. The host-guest properties of ß-cyclodextrins have been successfully exploited in order to trap drugs, like dopamine and levodopa. The further release of these drugs was successfully achieved by providing specific electrical stimuli. This proof-of-concept led us to fabricate an electronic device (i.e. an organic transistor) capable of dispensing both dopamine and levodopa in aqueous solution.

Electrowetting of nitro-functionalized oligoarylene thiols self-assembled on polycrystalline gold.

Four linear terarylene molecules (i) 4-nitro-terphenyl-4″-methanethiol (NTM), (ii) 4-nitro-terphenyl-3″,5″-dimethanethiol (NTD), (iii) ([1,1';4',1″] terphenyl-3,5-diyl)methanethiol (TM), and (iv) ([1,1';4',1″] terphenyl-3,5-diyl)dimethanethiol (TD) have been synthesized and their self-assembled monolayers (SAMs) have been obtained on polycrystalline gold. NTM and NTD SAMs have been characterized by X-ray photoelectron spectroscopy, Kelvin probe measurements, electrochemistry, and contact angle measurements. The terminal nitro group (-NO2) is irreversibly reduced to hydroxylamine (-NHOH), which can be reversibly turned into nitroso group (-NO). The direct comparison between NTM/NTD and TM/TD SAMs unambiguously shows the crucial influence of the nitro group on electrowetting properties of polycrystalline Au. The higher grade of surface tension related to NHOH has been successfully exploited for basic operations of digital µ-fluidics, such as droplets motion and merging.