Pore networks and polymer rearrangement on a drug-eluting stent as revealed by correlated confocal Raman and atomic force microscopy.

Drug release from and coating morphology on a CYPHER sirolimus-eluting coronary stent (SES) during in vitro elution were studied by correlated confocal Raman and atomic force microscopy (CRM and AFM, respectively). Chemical surface and subsurface maps of the SES were generated in the same region of interest by CRM and were correlated with surface topography measured by AFM at different elution times. For the first time, a direct correlation between drug-rich regions and the coating morphology was made on a drug-eluting medical device, linking drug release with pore formation, pore throats, and pore networks. Drug release was studied on a drug-eluting stent (DES) system with a multicomponent carrier matrix (poly(n-butyl methacrylate) [PBMA] and poly(ethylene-co-vinyl acetate) [PEVA]). The polymer was found to rearrange postelution because confluence of the carrier polymer matrix reconstituted the voids created by drug release.

Surface-enhanced Raman spectroscopy of benzenethiol adsorbed from the gas phase onto silver film over nanosphere surfaces: determination of the sticking probability and detection limit time.

A chemical warfare agent (CWA) gas detector based on surface-enhanced Raman spectroscopy (SERS) using robust nanostructured substrates and a portable Raman spectrometer is a promising alternative to existing modalities. A gas-dosing apparatus was constructed to simulate chemical gas exposure and provide a platform for quantitative analysis of SERS detection. As a first step toward characterizing SERS detection from the gas phase, benzenethiol (BT) has been chosen as the test analyte. SERS spectra were monitored during BT adsorption onto a silver film over a nanosphere (AgFON) substrate. The SERS detection limit time (DLt) for BT on a AgFON at 356 K is found to be 6 ppm-s (30 mg-s m(-3)) for a data acquisition time (t(acq)) of 1 s. The DLt for this kinetically controlled sensor is fundamentally determined by the low sticking probability of BT on AgFONs which is determined to be approximately 2 x 10(-5) at 356 K. The sticking probability increases with increasing temperature consistent with an adsorption activation barrier of approximately 13 kJ mol(-1). Although the DLts found in the present study for BT are in the low ppm-s, a theoretical model of SERS detection indicates DLts below 1 ppb s(-1) for t(acq)= 1 s are, in fact, achievable using existing portable Raman instrumentation and AgFON surfaces. Achieving this goal requires the sticking probability be increased 3 orders of magnitude, illuminating the importance of appropriate surface functionalization.

Surface-enhanced Raman spectroscopy of half-mustard agent.

The detection and identification of chemical warfare agents is an important analytical goal. Herein, it is demonstrated that 2-chloroethyl ethyl sulfide (half-mustard, CEES) can be successfully analysed using surface-enhanced Raman spectroscopy (SERS). A critical component in this detection system is the fabrication of a robust, yet highly enhancing, sensor surface. Recent advances in substrate fabrication and in the fundamental understanding of the SERS phenomenon enable the development of improved substrates for practical SERS applications.