Colloidally Stable Silicon Nanocrystals with Near‐Infrared Photoluminescence for Biological Fluorescence Imaging

Luminescent silicon nanocrystals (ncSi) are showing great promise as photoluminescent tags for biological fluorescence imaging, with size‐dependent emission that can be tuned into the near‐infrared biological window and reported lack of toxicity. Here, colloidally stable ncSi with NIR photoluminescence are synthesized from (HSiO_1.5)_n sol–gel glasses and are used in biological fluorescence imaging. Modifications to the thermal processing conditions of (HSiO_1.5)_n sol–gel glasses, the development of new ncSi oxide liberation chemistry, and an appropriate alkyl surface passivation scheme lead to the formation of colloidally stable ncSi with photoluminescence centered at 955 nm. Water solubility and biocompatibility are achieved through encapsulation of the hydrophobic alkyl‐capped ncSi within PEG‐terminated solid lipid nanoparticles. Their applicability to biological imaging is demonstrated with the in‐vitro fluorescence labelling of human breast tumor cells.     

Preparation of Fluorescent Microcystin Derivatives by Direct Arginine Labelling and Their Biological Evaluation

Microcystin is the most prevalent toxin produced by cyanobacteria and poses a severe threat to livestock, humans and entire ecosystems. We report the preparation of a series of fluorescent microcystin derivatives by direct arginine labelling of the unprotected peptides at the guanidinium side chain. This new method allows a simple late‐stage diversification strategy for native peptides devoid of protecting groups under mild conditions. A series of fluorophores were conjugated to microcystin‐LR in good to very good yield. The fluorescent probes displayed biological activity comparable to that of unlabelled microcystin, in both phosphatase inhibition assays and toxicity tests on the crustacean Thamnocephalus platyurus. In addition, we demonstrate that the fluorescent probes penetrated Huh7 cells. Whole‐animal imaging was performed on T. platyurus: labelled compound was mainly observed in the digestive tract.     

Nanoparticle-Based Strain Gauges: Anisotropic Response Characteristics,Multidirectional Strain Sensing,and Novel Approaches to Healthcare Applications

Directional strain sensing is essential for advanced sensor applications in the field of human-machine interfaces and healthcare. Here, the angle dependent anisotropic strain sensitivity caused by charge carriers percolating through cross-linked gold nanoparticle (GNP) networks is studied and these versatile materials are used for the fabrication of wearable triaxial pulse and gesture sensors. More specifically, the anisotropic response of 1,9-nonanedithiol cross-linked GNP films is separated into geometric and piezoresistive contributions by fitting the measured data with an analytic model. Hereby, piezoresistive coefficients of g₁₁ ∼ 32 and g₁₂ ∼ 21 are extracted, indicating a slightly anisotropic response behavior of the GNP-based material. To use the material for healthcare applications, arrangements of three GNP transducers are patterned lithographically and fully embedded into a highly flexible silicone polymer (Dragon Skin 30). The new encapsulation method ensures good and robust electrical contacts and enables facile handling and protection from external influences. A facile read-out with wireless data transmission using off-the-shelf electrical components underlines the great potential of these devices for applications as skin-wearable healthcare sensors.     

Wear Behavior of Roller-Burnished High Interstitial Austenitic Stainless Steel Parts in Glass-Reinforced Plastic Melt

Herein this investigation, profiled high interstitial austenitic stainless steel parts are burnished on a profile-rolling machine, and afterward, the wear behavior is analyzed in a melt of glass-reinforced polypropylene. Wear and corrosion resistance are significant properties of steel parts in the plastics and food industries. The high work-hardening ability of high interstitial austenitic stainless steel enables burnishing parts with a significant local hardness to increase up to maximum values of ≈600 HV 1. Wear tests on a recently developed test stand reveal that the burnished austenitic stainless steel surface performs similarly to a nitrided surface of the standard nitriding steel 31CrMoV9 + QT with a hardness of ≈830 HV 0.5. Regarding the given advantage of corrosion resistance, it is concluded that roller burnishing supports the applicability of high interstitial austenitic stainless steel in plastics and food industries.