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Surface-enhanced Raman spectroscopy (SERS) is an attractive tool in the analytical sciences due to its high specificity and sensitivity. Because SERS-active substrates are only available as two-dimensional arrays, the fabrication of three-dimensional (3D) nanostructures allows for an increased number of hot spots in the focus volume, thus further amplifying the SERS signal. Although a great number of fabrication strategies for powerful SERS substrates exist, the generation of 3D nanostructures with high complexity and periodicity is still challenging. For this purpose, we report an easy fabrication technique for 3D nanostructures following a bottom-up preparation protocol. Enzymatically generated silver nanoparticles (EGNPs) are prepared, and the growth of hierarchically-designed 3D flower-like silica–silver composite nanostructures is induced by applying plasma-enhanced atomic layer deposition (PE-ALD) on the EGNPs. The morphology of these nanocomposites can be varied by changes in the PE-ALD cycle number, and a flower height of up to 10 μm is found. Moreover, the metallized (e.g., silver or gold) 3D nanostructures resulting from 135 PE-ALD cycles of silica creation provide highly reproducible SERS signals across the hydrophobic surface. Within this contribution, the morphological studies, optical properties, as well as the SERS response of these metallized silica–silver composite nanostructures applying vitamin B2 as a model analyte are introduced.

In utilizing the exceptional optical properties of metallic nanoparticles, surface enhanced Raman spectroscopy (SERS) is an excellent candidate for analytical detection schemes due to its molecular specificity and high sensitivity. To record reliable SERS signals, impurifications on the metallic surface contributing to the overall SERS signal, have to be removed. In this context, it is important to improve the nanostructures’ quality to implement SERS in routine analytical applications. Here, we report about an easy to handle and fast protocol for the generation of SERS active nanoparticles by enzymatically reducing silver ions to their elementary state and oxidizing hydroquinone (HQ) to p-benzoquinone (p-BQ). However, these SERS substrates lead to a strong background signal overlapping with the actual analyte Raman bands. In order to quench this background signal and to protect the silver nanoparticles from oxidation we covered metallic nanoparticles with a dielectric layer of alumina (Al2O3) by applying plasma enhanced atomic layer deposition (PE-ALD). This coating guarantees the stability of these SERS substrates for at least 4 weeks after preparation under ambient storing conditions. The sensitivity of these enzymatically generated nanoparticles (EGNPs) coated with a 1 nm Al2O3layer allows for a background free detection of riboflavin down to less than 10 nM. Furthermore, the improved specificity of these background-free and bottom-up produced plasmonic arrays has also been demonstrated by detecting a retinol monolayer.

The aim of this study was to compare the image quality of a compact mobile flat-panel computed tomography (FPCT) capable of extremity imaging and a multidetector computed tomography (MDCT) in examinations with the same radiation dose.

Neovascularization represents an important issue in tissue-engineering applications, since survival of implanted cells strongly relies on sufficient oxygen and nutrient supply. We have recently observed that human bone marrow-derived mesenchymal stem cells (MSCs) support neovessel formation originating from coimplanted endothelial cells (ECs) in vivo, suggesting that MSCs may function as perivascular cells by investing and stabilizing nascent EC-derived neovessels. In this study, we investigated EC-induced mural cell differentiation of MSCs in vitro. For this purpose, endothelial progenitor cells (EPCs) from two different origins, namely adult peripheral blood (pbEPCs) and neonatal cord blood (cbEPCs), or human umbilical vein endothelial cells (HUVECs), were cocultured with human MSCs to analyze the effect on MSC differentiation toward a smooth muscle cell (SMC)/pericyte phenotype. EPCs as well as HUVECs increased alpha-smooth muscle actin expression in MSCs upon cocultivation in a time-dependent manner. This effect was strongly dependent on direct cell-to-cell contact and extracellular signal-regulated kinase (ERK) signaling, but was not mediated by heterotypic gap junction communication. Beyond enhanced SMC marker gene expression in MSCs, EPCs also enhanced the functional characteristics of cocultured MSCs by increasing their ability to attach to EC tubes in vitro. In conclusion, our study has shown that EPCs from adult peripheral blood as well as from cord blood commit cocultivated MSCs toward an SMC/pericyte phenotype in a cell-contact- and ERK-dependent manner.