Since its first experimental realization, tip-enhanced Raman spectroscopy (TERS) has emerged as a potentially powerful nanochemical analysis tool. However, questions about the comparability and reproducibility of TERS data have emerged. This interlaboratory comparison study addresses these issues by bringing together different TERS groups to perform TERS measurements on nominally identical samples. Based on the spectra obtained, the absolute and relative peak positions, number of bands, peak intensity ratios, and comparability to reference Raman and surface-enhanced Raman spectroscopy (SERS) data are discussed. Our general findings are that all research groups obtained similar spectral patterns, irrespective of the setup or tip that was used. The TERS (and SERS) spectra consistently showed fewer bands than the conventional Raman spectrum. When comparing these three methods, the spectral pattern match and substance identification is readily possible. Absolute and relative peak positions of the three major signals of thiophenol scattered by 19 and 9 cm À1 , respectively, which can probably be attributed to different spectrometer calibrations. However, within the same group (but between different tips), the signals only scattered by 3 cm À1 on average. This study demonstrated the suitability of TERS as an analytical tool and brings TERS a big step forward to becoming a routine technique.
In this paper, we present an ultrasonically powered implantable micro-oxygen generator (IMOG) that is capable of in situ tumor oxygenation through water electrolysis. Such active mode of oxygen generation is not affected by increased interstitial pressure or abnormal blood vessels that typically limit the systemic delivery of oxygen to hypoxic regions of solid tumors. Wireless ultrasonic powering (2.15 MHz) was employed to increase the penetration depth and eliminate the directional sensitivity associated with magnetic methods. In addition, ultrasonic powering allowed for further reduction in the total size of the implant by eliminating the need for a large area inductor. IMOG has an overall dimension of 1.2 mm × 1.3 mm × 8 mm, small enough to be implanted using a hypodermic needle or a trocar. In vitro and ex vivo experiments showed that IMOG is capable of generating more than 150 μA which, in turn, can create 0.525 μL/min of oxygen through electrolytic disassociation. In vivo experiments in a well-known hypoxic pancreatic tumor models (1 cm (3) in size) also verified adequate in situ tumor oxygenation in less than 10 min.
This paper presents a minimally invasive implantable pressure sensing transponder for continuous wireless monitoring of intraocular pressure (IOP). The transponder is designed to make the implantation surgery simple while still measuring the true IOP through direct hydraulic contact with the intraocular space. Furthermore, when IOP monitoring is complete, the design allows physicians to easily retrieve the transponder. The device consists of three main components: 1) a hypodermic needle (30 gauge) that penetrates the sclera through pars plana and establishes direct access to the vitreous space of the eye; 2) a micromachined capacitive pressure sensor connected to the needle back-end; and 3) a flexible polyimide coil connected to the capacitor forming a parallel LC circuit whose resonant frequency is a function of IOP. Most parts of the sensor sit externally on the sclera and only the needle penetrates inside the vitreous space. In vitro tests show a sensitivity of 15 kHz/mmHg with approximately 1-mmHg resolution. One month in vivo implants in rabbits confirm biocompatibility and functionality of the device.
We present a disease-on-a-chip model in which cancer grows within phenotypically normal breast luminal epithelium on semicircular acrylic support mimicking portions of mammary ducts. The cells from tumor nodules developing within these hemichannels are morphologically distinct from their counterparts cultured on flat surfaces. Moreover, tumor nodules cocultured with the luminal epithelium in hemichannels display a different anticancer drug sensitivity compared to nodules cocultured with the luminal epithelium on a flat surface and to monocultures of tumor nodules. The mimicry of tumor development within the epithelial environment of mammary ducts provides a framework for the design and test of anticancer therapies.
In this paper, we demonstrate fabrication and characterization of a nanofluidic channel with embedded transverse nanoelectrodes using a combination of conventional photolithography and focused ion beam technologies. Glass-capped silicon dioxide nanochannels having 20 nm depth, 50 nm width, and 2 microm length with embedded platinum nanoelectrodes were fabricated. Channel patency was verified through measurements of the resistivity in phosphate buffered saline and electrostatic action on charged fluorescent nanospheres. Platinum nanoelectrode functionality was also tested using transverse resistance measurements in nanochannels filled with air, deionized water, and saline solution.
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