We sought to describe the response of the polymer surface of drug-eluting stents (DES) to delivery balloon expansion, including quantitation of any resulting detached microparticles.We expanded the US Food and Drug Administration (FDA)-approved first- and second-generation DES in a vacuum filtration system and used optical and scanning electron microscopy to image the polymer surface, filters and delivery balloons. DES were expanded under a range of conditions, from in vitro conditions used for FDA regulatory submissions to human in vivo conditions. Dispersive Raman spectroscopy was used for definitive identification of microparticles. All polymer surfaces were topographically disturbed over an average of 4.6%-100% of the surface area imaged. Disturbances ranged from deformation (including peeling) to complete delamination. The dimensions of detached microparticles were 2-350 μm. The extent and nature of surface disturbances and microparticles were primarily a function of polymer composition (p<0.001 for 8/10 disturbance types/locations) and were independent of expansion condition (p=0.100 to 0.989 for 9/10 disturbance types/locations).Balloon expansion of first- and second-generation DES disturbs the polymer surface and can cause detachment of microparticles; each is functionally related to the specific polymer but not to expansion condition. Disturbance "roughness" and detached microparticles may contribute to DES limitations.
Discussed in detail is the synthesis and primary structure characterization of two polymers aimed at advancing the treatment of pediatric osteosarcoma. These polymers are designed to systemically deliver radiometals specifically to osteosarcomas using the passive targeting mechanism of enhanced permeability and retention (the EPR effect). The approach begins with the synthesis of a polymer capable of binding radiometals, for which prior data show improved site-specific targeting of solid tumors. Building on this success, a second polymer has been designed for improving the efficacy of currently available radionuclide therapies by incorporating the FDA-approved small-molecule ligand Quadramet directly onto the polymer structure. Time-activity curves of the phosphonate-functionalized polymers show rapid clearance from the central compartment and nontargeted organs, with up to 65% of injected activity being excreted within 3 hours. Both polymer ligands demonstrate good osteosarcoma targeting capability with little to no uptake in organs associated with the dose-limiting bone marrow. Additionally, biodistribution studies in nonosseous tumor models demonstrate the tumor targeting mechanism of the polymer ligands, which appears to be influenced by the high affinity of the phosphonate functionality for the positively charged hydroxyapatite mineral found in bone tumors.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTX-ray photoelectron spectroscopy of nitroso compounds: relative ionicity of the closed and open formsC. D. Batich and D. S. DonaldCite this: J. Am. Chem. Soc. 1984, 106, 10, 2758–2761Publication Date (Print):May 1, 1984Publication History Published online1 May 2002Published inissue 1 May 1984https://pubs.acs.org/doi/10.1021/ja00322a004https://doi.org/10.1021/ja00322a004research-articleACS PublicationsRequest reuse permissionsArticle Views578Altmetric-Citations64LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts
Alterations in regional brain iron are a feature of many neurodegenerative disorders, and provide a degree of natural contrast in magnetic resonance imaging (MRI). However, the nature of the iron species causing this is generally not known, but this will likely have a significant effect on relaxation times. We are using high field high resolution imaging to investigate the contribution of iron to magnetic relaxation in autopsy tissues for Alzheimer's and matched control cases to assess the potential for a non-invasive MRI-based early detection and monitoring technique. The relaxation parameters T1, T2 and T2* are measured for a variety of iron standards, including iron solutions and ferritin, using Bruker 750MHz and 600MHz instruments (17.6 and 14 Tesla respectively). A protocol to image unfixed fresh-frozen tissue is developed in order to quantify the same relaxation parameters in autopsy tissue, where standard fixation significantly affects iron states. Imaging parameters were optimized using iron standards to permit accurate determination of T1, T2 and T2* in unfixed human autopsy brain tissue. Tissue from both Alzheimer's cases and controls was selected from the hippocampus, superior temporal gyrus and inferior parietal cortex, and imaged at high resolution allowing quantitative comparisons between cases and regions. Synchrotron X-ray imaging is subsequently used to determine the extent to which iron accumulations contribute to T2 shortening and T2* contrast in these tissues. In figure 1, an example of hippocampal tissue imaged using a gradient echo sequence in a 14 Tesla field is shown. The field of view is 8 × 8 mm, slice thickness is 80 microns, and in-plane resolution is 60 × 60 microns. The experimental technique presented here allows high resolution quantitative MRI of unfixed autopsy tissues. Combined with subsequent synchrotron X-ray analysis, these techniques will enable identification and validation of specific iron compounds responsible for altered relaxation parameters – an approach which has potential application to a broad range of neurodegenerative disorders.
A series of butadiene/styrene homopolymers and copolymers were exposed to air-enriched ozone. For butadiene and random copolymers, surface energies quickly increase and oxygen/carbon ratios are large upon initial exposure as evidenced by contact angle measurements and XPS spectra. This is presumed to be simple oxidative degradation of carbon-carbon double bonds. For polystyrene and high % styrene block copolymers, surface energies are increased slightly by ozone but surface oxygen concentrations are not significantly affected. For low percent styrene block copolymers, surface energies approach their highest levels and surface oxygen content their lowest levels upon ozone exposure. This study indicates preferential segregation of styrene at the surface of the block copolymers.
Abstract A combination of chain and step propagations is being used to prepare a series of segmented copolymers containing polyoxyethylene and polypivalolactone segments each with narrow molecular weight distributions. The incompatibility of the two segments coupled with the difference in surface energies of the two segments could result in good phase separation with the polyoxyethylene segment thereby being found on the surface. Poly(oxyethylene)‐co‐(pivalolactone) telechelomer, which is the precursor to the segmented copolymer, is used as a model to develop an XPS method for surface analysis. An angular resolution study shows that negligible amounts of poly(pivalolactone) segments are present near the surface. Core level spectra of the telechelomer and its model compounds are presented to indicate that poly(oxyethylene) segment is richer near the surface.
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