One-step process to create porous structures in cross-linked polymer films via breath-figure formations during in situ cross-linking reactions

This work demonstrates a new strategy of producing honeycomb-like porous structures in cross-linked polymer films via a simple one-step synthesis/fabrication process. This is based on the “breath figure” formation during the in situ cross-linking of reactive monomer solutions. A chloroform solution, containing tert-butyl acrylate monomer and tetraethylene glycol dimethacrylate cross-linker, was cross-linked upon UV radiation under a moist and nitrogen saturated chamber. Micron-sized pores with reasonable uniformity were obtained in the cross-linked polymer films. The size, shape, uniformity and ordering of the pores show significant dependences on the processing conditions. Using this method, porous structures were also achieved in a commercially available photo-active resin, NOA 65, illustrating the generality of this approach.     

Fabrication and characterizations of crosslinked porous polymer films with varying chemical compositions

In this paper, we demonstrated the successful fabrication of crosslinked porous films with varying monomer-crosslinker ratios, by photo-induced crosslinking during the breath figure formation. For all the samples fabricated, the pores at the peripheral regions appeared more uniform in size and showed higher degree of ordering, due to the interplay between the solvent evaporation and crosslinking reaction. The pore morphology remains similar despite varying film compositions, suggesting that the pore-fixing process is still dominated by the solvent evaporation similar to that of conventional breath figure process, and is less dependent on the crosslinking process. Detailed characterizations of the chemical and physical properties, including the glass transition temperature, thermal stability, and surface wettability of the porous films were carried out.     

A Thermal‐Reflow‐Based Low‐Temperature,High‐Pressure Sintering of Lyophilized Silk Fibroin for the Fast Fabrication of Biosubstrates

Solid fibroin is a bulk nonporous material that can be prepared with two methods: a liquid–gel–solid transition from a fibroin solution or a sintering procedure starting from silk powder. Both methods have their own disadvantages: the first requires several weeks and the process is size dependent; the second requires high temperatures. To overcome these limitations, a low‐temperature sintering procedure based on a thermal‐reflow is proposed in this work to produce in fast‐fashion monoliths of solid fibroin. Thermal‐reflow is a well‐known mechanism that takes place when the glass transition temperature of the material is lower than the temperature used to process it. Water plays an important role decreasing the glass transition temperature down to 40 °C. For the first time, a thermal reflow is conducted on lyophilized silk fibroin at 40 °C, associating to the water addition a high‐pressure compression. To optimize the process, a full factorial design of experiment is used. The material is then studied in the crucial phases by digital scanning calorimetry, Fourier‐transform infrared spectroscopy, and scanning electron microscopy. Finally, a mechanical characterization and a preliminary in vitro test are conducted.     

Luminescent graphene quantum dots from oxidized multi-walled carbon nanotubes

Fluorescent nano-graphene quantum dots (GQD) were isolated from oxidized carbon nanotube suspension with the aid of cysteamine. The oxidized GQD were thiol functionalized with cysteamine in presence of dicyclohexylcarbodiimide as coupling agent. The GQD chemistry and morphology were characterized by means of X-ray photoelectron spectroscopy and atomic force microscopy. The thiolated graphene quantum dots exhibit an intense luminescence (quantum yield around 10%) in the visible range with an excitation wavelength-dependent fluorescence.     

Polyelectrolytes-coated gold nanoparticles detection by PEDOT:PSS electrochemical transistors

Electrochemical transistors made of PEDOT:PSS are used to detect different polymeric shells used to functionalize the nanoparticles for drug delivering. The devices were realized drawing their configuration directly on glass with a micro-syringe and micro-positioning system. This permits a great flexibility in the definition of the needed geometry giving the possibility to maximize the signal to the different polymeric shells. The realized devices exhibit different responses respect to the functionalized nanoparticles and in particular respect to the polymer used for their functionalization. The linear behavior observed gives the possibility to use these devices to detect the quantity of polymer loaded on the nanoparticles. This opens to the possibility to determine the quantity of drugs that could be loaded inside the functionalized shells and also to detect the kinetics of drug delivery or, even, to monitor the stability of the nanoparticles themselves.     

Mesothelioma and Colorectal Cancer: Report of Four Cases with Synchronous and Metachronous Presentation

There is evidence that asbestos could play a role in the carcinogenesis of digestive cancers. The presence of asbestos fibres in histological samples from gastric, biliary, colon cancers has been reported, but the mechanism is still controversial. It has been hypothesised that asbestos reaches these sites, especially through contaminated water; however, some experimental studies have shown that the inhaled fibres are mobile, so they can migrate to many organs, directly or via blood and lymph flow. We report four unusual cases of colorectal cancers in patients with a long history of asbestos exposure who also developed synchronous or metachronous mesothelioma. We evaluated the roles of BRCA associated protein-1 (BAP1) and cyclin-dependent kinase inhibitor 2A (CDKN2A) in colon cancer and mesothelioma to support the hypothesis that BAP-1 and CDKN2A are tumour suppressor genes involved in disease progression, recurrence, or death in both digestive cancers and mesothelioma. Potentially, these markers may be used as predictors of worse prognosis, but we also stress the importance of clinical surveillance of exposed patients because asbestos could induce cancer in any organ.     

Breath figures decorated silica-based ceramic surfaces with tunable geometry from UV cross-linkable polysiloxane precursor

Little has been published so far on the fabrication of porous ceramic films by using the Breath Figure method. In this work we explored the Breath Figure method to obtain ceramics with patterned surfaces. A UV cross-linkable polysiloxane was used to produce Breath Figures with tunable pore size. Pores formation, in terms of size and distribution on the polysiloxane films, were studied as a function of the concentration of the starting solution and time before UV irradiation. The polymeric breath figures were then pyrolyzed in controlled atmosphere to obtain, through the polymer-derived ceramic, PDCs, route the corresponding ceramic preserving the original porous surface. Pyrolysis under different gases, in particular air, nitrogen and ammonia, allows obtaining films of three different ceramic materials: silicon dioxide, SiO₂, silicon oxycarbide, SiOC and silicon oxynitride, SiON respectively.