We report preparation of highly transparent, flexible, and thermally stable superhydrophobic organically modified silica (ORMOSIL) aerogel thin films from colloidal dispersions at ambient conditions. The prepared dispersions are suitable for large area processing with ease of coating and being directly applicable without requiring any pre- or post-treatment on a variety of surfaces including glass, wood, and plastics. ORMOSIL films exhibit and retain superhydrophobic behavior up to 500 °C and even on bent flexible substrates. The surface of the films can be converted from superhydrophobic (contact angle of 179.9°) to superhydrophilic (contact angle of <5°) by calcination at high temperatures. The wettability of the coatings can be changed by tuning the calcination temperature and duration. The prepared films also exhibit low refractive index and high porosity making them suitable as multifunctional coatings for many application fields including solar cells, flexible electronics, and lab on papers.

Dopamine is the principle biomarker for diseases such as schizophrenia, Huntington's, and Parkinson's, and the need is urgent for rapid and sensitive detection methods for diagnosis and monitoring of such diseases. In this Article, we report a turn-on fluorescent method for rapid dopamine sensing which is based on monitoring the intrinsic fluorescence of in situ synthesized polydopamine nanoparticles. The assay uses only a common base and an acid, NaOH and HCl to initiate and stop the polymerization reaction, respectively, which makes the assay extremely simple and low cost. First, we studied the in situ optical properties of polydopamine nanoparticles, for the first time, which formed under different alkaline conditions in order to determine optimum experimental parameters. Then, under optimized conditions we demonstrated high sensitivity (40 nM) and excellent selectivity of the assay. With its good analytical figures of merit, the described method is very promising for detection of dopamine related diseases. D opamine (DA), a catecholamine neurotransmitter, regulates many biological processes in central nervous, hormonal, and cardiovascular systems.1,2 Abnormal DA concentrations in biological fluids (e.g., urine, blood plasma, and extracellular fluid of the central nervous system) can be indicator of several diseases such as schizophrenia and Huntington's and Parkinson's diseases. 3−5 In this regard, sensitive and selective measurement of DA levels is important for diagnosis of these diseases and monitoring of patients. 6 Common DA detection methods utilize electrochemical analysis, 7−9 chromatography coupled with spectroscopy 10,11 (e.g., high-pressure liquid chromatography (HPLC)-fluorescence and gas chromatography/mass spectrometry (GC/MS)) and fluorescent 12−16 or colorimetric probes 1,17 (e.g., organic dyes, quantum dots, and gold nanoparticles). These methods, however, have some limitations. For instance, interference from uric acid (UA) and ascorbic acid (AA) largely limits selectivity of electrochemical methods. Chromatographic methods on the other hand, are time-consuming, labor intensive, and expensive with complicated procedures. Similarly, synthesis of fluorescent or colorimetric probes for DA detection involves complicated and time-consuming procedures.A straightforward, cost-effective and rapid alternative for DA detection is measuring the optical absorption of oxidation product of dopamine under alkaline conditions.18−22 These assays use only a common base (e.g., NaOH) or other oxidants (e.g., enzymes) as a reagent, and DA concentration is determined by simply measuring the optical absorption of the resulting brownish oxidation product. Unfortunately, the method demonstrates a poor sensitivity around a few micromolar. In these oxidation studies, the product is assumed as a quinone derivative of dopamine. 18 However, recent studies demonstrated that under alkaline conditions the quinone product is unstable and rapidly polymerized by covalent attachment and aggregation. 23−25 The resul...

While gas-filled micrometer-sized ultrasound contrast agents vastly improve signal-to-noise ratios, microbubbles have short circulation lifetimes and poor extravasation from the blood. Previously reported fluorocarbon-based nanoscale contrast agents are more stable but their contrast is generally lower owing to their size and dispersity. The contrast agents reported here are composed of silica nanoparticles of ≈100 nm diameter that are filled with ≈3 nm columnar mesopores. Functionalization of the silica surface with octyl groups and resuspension with Pluronic F127 create particles with pores that remain filled with air but are stable in buffer and serum. Administration of high intensity focused ultrasound (HIFU) allows sensitive imaging of the silica nanoparticles down to 10 10 particles mL −1, with continuous imaging for at least 20 min. Control experiments with different silica particles supported the hypothesis that entrapped air could be pulled into bubble nuclei, which can then in turn act as acoustic scatterers. This process results in very little hemolysis in whole blood, indicating potential for nontoxic blood pool imaging. Finally, the particles are lyophilized and reconstituted or stored in PBS (phosphate-buffered saline, at least for four months) with no loss in contrast, indicating stability to storage and reformulation.

Although numerous mesoporous silica nanoparticle (MSN) drug carriers and theranostic agents with various surface functionalities have been designed in the last decade, their biocompatibility remains a matter of intensive debate. Here, we systematically evaluated interactions of a series of MSNs possessing different surface functional groups (ionic, polar, neutral, and hydrophobic) with blood constituents, in terms of their hemolytic activity, thrombogenicity, and adsorption of blood proteins on their surfaces. Using a hemolysis assay we showed that surface functionalization can reduce or even completely prevent the hemolytic activity of bare MSNs. We investigated thrombogenicity of MSNs by measuring prothrombin time (PT) and activated partial thromboplastin time (aPTT). We observed that none of the MSNs used in this study exhibit significant thrombogenic activity. Lastly, we examined non-specific protein adsorption on MSN surfaces using human serum albumin (HSA) and gamma globulins (γGs) and found that surface functionalization with ionic groups can greatly reduce protein adsorption. Demonstration of the surface functionalization having a crucial impact on blood compatibility might serve as a guideline for further investigation related to the design of mesoporous silica systems for biomedical applications, and shed light on research towards the ultimate goal of developing smart theranostic systems. © The Royal Society of Chemistry 2013

Ultrasound is widely applied in medical diagnosis and therapy due to its safety, high penetration depth, and low cost. In order to improve the contrast of sonographs and efficiency of the ultrasound therapy, echogenic gas bodies or droplets (with diameters from 200 nm to 10 µm) are often used, which are not very stable in the bloodstream and unable to penetrate into target tissues. Recently, it was demonstrated that nanobubbles stabilized by nanoparticles can nucleate ultrasound responsive microbubbles under reduced acoustic pressures, which is very promising for the development of nanoscale (<100 nm) ultrasound agents. However, there is still very little understanding about the effects of nanoparticle properties on the stabilization of nanobubbles and nucleation of acoustic cavitation by these nanobubbles. Here, a series of mesoporous silica nanoparticles with sizes around 100 nm but with different morphologies were synthesized to understand the effects of nanoparticle porosity, surface roughness, hydrophobicity, and hydrophilic surface modification on acoustic cavitation inception by porous nanoparticles. The chemical analyses of the nanoparticles showed that, while the nanoparticles were prepared using the same silica precursor (TEOS) and surfactant (CTAB), they revealed varying amounts of carbon impurities, hydroxyl content, and degrees of silica crosslinking. Carbon impurities or hydrophobic modification with methyl groups is found to be essential for nanobubble stabilization by mesoporous silica nanoparticles. The acoustic cavitation experiments in the presence of ethanol and/or bovine serum albumin (BSA) demonstrated that acoustic cavitation is predominantly nucleated by the nanobubbles stabilized at the nanoparticle surface not inside the mesopores. Finally, acoustic cavitation experiments with rough and smooth nanoparticles were suggested that a rough nanoparticle surface is needed to largely preserve surface nanobubbles after coating the surface with hydrophilic macromolecules, which is required for in vivo applications of nanoparticles.