Nanowire-Intensified MEF in Hybrid Polymer-Plasmonic Electrospun Filaments

Hybrid polymer-plasmonic nanostructures might combine high enhancement of localized fields from metal nanoparticles with light confinement and long-range transport in subwavelength dielectric structures. Here we report on the complex behavior of fluorophores coupling to Au nanoparticles within polymer nanowires, which features localized metal-enhanced fluorescence (MEF) with unique characteristics compared to conventional structures. The intensification effect when the particle is placed in the organic filaments is remarkably higher with respect to thin films of comparable thickness, thus highlighting a specific, nanowire-related enhancement of MEF effects. A dependence on the confinement volume in the dielectric nanowire is also evidenced, with MEF significantly increasing upon reducing the wire diameter. These findings are rationalized by finite element simulations, predicting a position-dependent enhancement of the quantum yield of fluorophores embedded in the fibers. Calculation of the ensemble-averaged fluorescence enhancement unveils the possibility of strongly enhancing the overall emission intensity for structures with size twice the diameter of the embedded metal particles. These new, hybrid fluorescent systems with localized enhanced emission, as well as the general Nanowire-Intensified MEF effect associated to them, are highly relevant for developing nanoscale light-emitting devices with high efficiency and inter-coupled through nanofiber networks, highly sensitive optical sensors, and novel laser architectures.Comment: 29 pages, 12 figures, Small (2018

Phenoxy resin-based vinylogous urethane covalent adaptable networks

This work presents a post-polymerization approach to the preparation of vitrimers, exploiting the transamination of vinylogous urethane in linear phenoxy resins. Phenoxy vitrimers are obtained by a two-steps synthesis from a commercial phenoxy resin via partial conversion of hydroxyl groups to acetoacetates (AcAc), followed by network formation by reaction with m-xylylendiamine (XYDIA) as crosslinker. Three different vitrimers with variable crosslinking density are obtained by tuning the density of AcAc moieties along the phenoxy resin scaffold (5%, 10% and 15% conversion of hydroxyl groups). The conversion of linear polymers to dynamic crosslinked networks is confirmed by Dynamic Mechanical Thermal Analyzer (DMTA) and rheology measurements, followed by stress relaxation tests to investigate the kinetics of bond exchanges. Tensile tests as a function of reprocessing cycles reveal an increase of the maximum elongation and stress at break and prove the good recyclability of the vitrimers. Enhanced adhesive properties compared to pristine phenoxy resins are demonstrated, including the possibility to thermally re-join the assembly after its mechanical failure. Finally, the solvent-free preparation of vitrimer is explored for 5% crosslinked vitrimer via melt reactive blending, providing a valuable alternative to the less environmentally sustainable synthesis in solution

Conformable nanowire-in-nanofiber hybrids for low-threshold optical gain in the ultraviolet

The miniaturization of diagnostic devices that exploit optical detection schemes requires the design of light-sources combining small size, high performance for effective excitation of chromophores, and mechanical flexibility for easy coupling to components with complex and non-planar shapes. Here, ZnO nanowire-in-fiber hybrids with internal architectural order are introduced, exhibiting a combination of polarized stimulated emission, low propagation losses of light modes, and structural flexibility. Ultrafast transient absorption experiments on the electrospun material show optical gain which gives rise to amplified spontaneous emission, with threshold lower than the value found in films. These systems are highly flexible and can conveniently conform to curved surfaces, which makes them appealing active elements for various device platforms, such as bendable lasers, optical networks and sensors, as well as for application in bioimaging, photo-crosslinking, and optogenetics.Comment: 50 pages, 17 figures, 1 table, ACS Nano, 202

Human Adipose Mesenchymal Stromal/Stem Cells Improve Fat Transplantation Performance

The resorption rate of autologous fat transfer (AFT) is 40-60% of the implanted tissue, requiring new surgical strategies for tissue reconstruction. We previously demonstrated in a rabbit model that AFT may be empowered by adipose-derived mesenchymal stromal/stem cells (AD-MSCs), which improve graft persistence by exerting proangiogenic/anti-inflammatory effects. However, their fate after implantation requires more investigation. We report a xenograft model of adipose tissue engineering in which NOD/SCID mice underwent AFT with/without human autologous AD-MSCs and were monitored for 180 days (d). The effect of AD-MSCs on AFT grafting was also monitored by evaluating the expression of CD31 and F4/80 markers. Green fluorescent protein-positive AD-MSCs (AD-MSC-GFP) were detected in fibroblastoid cells 7 days after transplantation and in mature adipocytes at 60 days, indicating both persistence and differentiation of the implanted cells. This evidence also correlated with the persistence of a higher graft weight in AFT-AD-MSC compared to AFT alone treated mice. An observation up to 180 d revealed a lower resorption rate and reduced lipidic cyst formation in the AFT-AD-MSC group, suggesting a long-term action of AD-MSCs in support of AFT performance and an anti-inflammatory/proangiogenic activity. Together, these data indicate the protective role of adipose progenitors in autologous AFT tissue resorption

Heterogeneous Random Laser with Switching Activity Visualized by Replica Symmetry Breaking Maps

In the past decade, complex networks of light emitters are proposed as novel platforms for photonic circuits and lab-on-chip active devices. Lasing networks made by connected multiple gain components and graphs of nanoscale random lasers (RLs) obtained from complex meshes of polymeric nanofibers are successful prototypes. However, in the reported research, mainly collective emission from a whole network of resonators is investigated, and only in a few cases, the emission from single points showing, although homogeneous and broad, spatial emission. In all cases, simultaneous activation of the miniaturized lasers are observed. Here, differently, we realize heterogeneous random lasers made of ribbon-like and highly porous fibers with evident RL action from separated micrometric domains that alternatively switch on and off by tuning the pumping light intensity. We visualize this novel effect by building for the first time replica symmetry breaking (RSB) maps of the emitting fibers with 2 μm spatial resolution. In addition, we calculate the spatial correlations of the laser regions showing clearly an average extension of 50 μm. The observed blinking effect is due to mode interaction along light guiding fibers and opens new avenues in the fabrication of flexible photonic networks with specific and adaptable activity

Low-defectiveness exfoliation of MoS2 nanoparticles and their embedment in hybrid light-emitting polymer nanofibers

Molybdenum disulfide (MoS2) has been attracting extraordinary attention for its intriguing optical, electronic and mechanical properties. Here, we demonstrate hybrid, organic-inorganic light-emitting nanofibers based on MoS2 nanoparticle dopants obtained through a simple and inexpensive sonication process in N-methyl-2-pyrrolidone and successfully encapsulate the nanofibers in polymer filaments. The gentle exfoliation method used to produce the MoS2 nanoparticles results in low defectiveness and preserves the stoichiometry. The fabricated hybrid fibers are smooth, uniform and flawless and exhibit bright and continuous light emission. Moreover, the fibers show significant capability for waveguiding self-emitted light along their longitudinal axes. These findings suggest that emissive MoS2 fibers formed by gentle exfoliation are novel and highly promising optical materials for sensing surfaces and photonic circuits

Label-Free Optical Sensing and Medical Grade Resins: An Advanced Approach to Investigate Cell–Material Interaction and Biocompatibility

The Corning Epic® label-free (ELF) system is an innovative technology widely used in drug discovery, immunotherapy, G-protein-associated studies, and biocompatibility tests. Here, we challenge the use of ELF to further investigate the biocompatibility of resins used in manufacturing of blood filters, a category of medical devices representing life-saving therapies for the increasing number of patients with kidney failure. The biocompatibility assays were carried out by developing a cell model aimed at mimicking the clinical use of the blood filters and complementing the existing cytotoxicity assay requested by ISO10993-5. Experiments were performed by putting fibroblasts in both direct contact with two types of selected resins, and indirect contact by means of homemade customized well inserts that were precisely designed and developed for this technology. For both types of contact, fibroblasts were cultured in medium and human plasma. ELF tests confirmed the biocompatibility of both resins, highlighting a statistically significant different biological behavior of a polyaromatic resin compared to control and ion-exchanged resin, when materials were in indirect contact and soaking with plasma. Overall, the ELF test is able to mimic clinical scenarios and represents a promising approach to investigate biocompatibility, showing peculiar biological behaviors and suggesting the activation of specific intracellular pathways

Portone A., Moffa M., Gardin C., Ferroni L., Tatullo M., Fabbri F., Persano L., Piattelli A., Zavan B., Pisignano D., Lineage-specific commitment of stem cells with organic and graphene-oxide functionalized nanofibers.

Controlling the differentiation to certain lineages is the main goal of current stem cell research, which might exploit new routes based on the interaction of cells with nanomaterials. Here it is shown that primary neurospheres from dental pulp stem cells grown on combinatorial surfaces with different fibrous morphology and graphene oxide functionalization exhibit different differentiation propensity. The developed materials strongly influence the stem cell fate, as highlighted by morphological, immunofluorescence, molecular biology, and functional analyses. Instructive cues lead to the increased expression of markers that are characteristic of selective differentiation into osteoblasts, glial cells, fibroblasts, and neurons even in basal medium conditions, and randomly oriented fibers are found to revert neuronal precommitment and to trigger osteoblastic differentiation. Graphene oxide coatings lead instead to the relatively enhanced expression of genes typical of either glial or neuronal commitment, depending on the underlying nanofibrous morphology. The mechanisms addressing cell fate are investigated, highlighting the correlation of wetting anisotropy and protein adsorption capacity of different surfaces, ultimate cell conformational changes reflected by skeletal and nuclear elongation, and directed cell commitment. Cues from the different surfaces are therefore lineage‐specific, unveiling remarkable potentialities for cellular programming by means of nanomaterials