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In optical biosensing, silk fibroin (SF) appears as a promising alternative where other materials, such as paper, find limitations. Besides its excellent optical properties and unmet capacity to stabilize biomacromolecules, SF in test strips exhibits additional functions, i.e. capillary pumping activity of 1.5 mm s−1, capacity to filter blood cells thanks to its small, but tuneable, porosity and enhanced biosensing sensitivity. The bulk functionalization of SF with the enzymes glucose oxidase and peroxidase and the mediator ABTS produces colourless and transparent SF films that respond to blood glucose increasing 2.5 times the sensitivity of conventional ABTS-based assays. This enhanced sensitivity results from the formation of SF–ABTS complexes, where SF becomes part of the bioassay. Additionally, SF films triple the durability of most stable cellulose-based sensors. Although demonstrated for glucose, SF microfluidic test strips may incorporate other optical bioassays, e.g. immunoassays, with the aim of transferring them from central laboratories to the place of patient's care. [ABSTRACT FROM AUTHOR]

CdFe2O4 nanoparticles of around 3.9 nm were synthesized using the coprecipitation method and protected by a silica layer. The nanoparticles were mixed with a coacervate and transformed into phosphate glasses with 1, 4 and 8% in mass of nanoparticles by the melt-quenching method. TEM images confirm that the nanoparticles were successfully incorporated into the matrix without inducing crystallization. 31P NMR and Raman spectral analyses show that new P–O–Si bonds are formed in the glasses containing nanoparticles. The glass transition increases as a function of the nanoparticle content due to an increase in the connectivity of the phosphate glass chains. The UV-Vis spectra show bands at 415 and 520 nm assigned to Fe3+ ions and at 1025 nm, characteristic of Fe2+ ions, indicating that some of the nanoparticles dissolve during the melting process. The sample with 8% CdFe2O4 presents a paramagnetic behavior. The glasses obtained are transparent, non-hygroscopic and possess enormous thermal stability which is important for the production of optical devices. [ABSTRACT FROM AUTHOR]

Bombyx mori silk fibroin offers unlimited opportunities for functionalization, processing, and biological integration. We describe in this work the design of structured organic inorganic hybrids based on silica and silk fibroin, taking advantage of the relationship between the structure and processing of the latter. In situ self-assembly of fibroin nanofibers along with hydrolysis and polycondensation of tetraethyl orthosilicate was employed. Structural characterization was performed by Raman and solid state NMR spectroscopies. Our findings demonstrated that fibroin precipitates in the reaction medium with prevailing β-sheet conformation. The transition from amorphous to crystalline state was observed to be favored by the increase of the fibroin concentration in the samples. The samples were obtained as robust and biocompatible monoliths, making them candidates for several applications, particularly in the biomedical field. As a novel development, the fibroin nanofibers were used as pore biotemplates to create mechanically robust silica monoliths with a hierarchical macro-mesoporous network in an easy templating process. The template was removed by thermal treatment and the as obtained silica based materials displayed surface area values ranging from 704 to 1057 m2 g−1 and a maximum pore volume of 0.621 mL g−1. The porous silica monoliths were then doped with rhodamine 6G and typical random laser action could be observed, with a minimum laser threshold of 9.7 μJ per pulse and a linewidth narrowing from 40 to 4 nm. In addition, it was shown that two coupled gain mechanisms were taking place, the random lasing and the stimulated Raman scattering, allowing us to observe Raman Stokes lines due to vibrational modes of the dye molecule. [ABSTRACT FROM AUTHOR]