It is still an open challenge to find a biodegradable metallic material exhibiting sufficient mechanical properties and degradation behavior to serve as an arterial stent. In this study, Zn-Mg alloys of 0.002 (Zn-002Mg), 0.005 (Zn-005Mg) and 0.08wt% Mg (Zn-08Mg) content were cast, extruded and drawn to 0.25mm diameter, and evaluated as potential biodegradable stent materials. Structural analysis confirmed formation of MgZn intermetallic in all three alloys with the average grain size decreasing with increasing Mg content. Tensile testing, fractography analysis and micro hardness measurements showed the best integration of strength, ductility and hardness for the Zn-08Mg alloy. Yield strength, tensile strength, and elongation to failure values of >200-300MPa, >300-400MPa, and >30% respectively, were recorded for Zn-08Mg. This metal appears to be the first formulated biodegradable material that satisfies benchmark values desirable for endovascular stenting. Unfortunately, the alloy reveals signs of age hardening and strain rate sensitivity, which need to be addressed before using this metal for stenting. The explants of Zn-08Mg alloy residing in the abdominal aorta of adult male Sprague-Dawley rats for 1.5, 3, 4.5, 6 and 11months demonstrated similar, yet slightly elevated inflammation and neointimal activation for the alloy relative to what was recently reported for pure zinc.
To investigate the typical magnetic resonance imaging (MRI) and computed tomography (CT) features of hepatic epithelioid hemangioendothelioma (HEH), the CT and MRI findings of 14 histopathologically confirmed cases of HEH were retrospectively analyzed. Non-contrast and dynamic contrast-enhanced scans were conducted in all cases. A total of 229 lesions were detected in the 14 cases. All cases were classified as one of three types: (i) Solitary nodular type (1 case, 7%); (ii) multifocal nodular type (11 cases, 79%); or (iii) diffuse type (2 cases, 14%). The diameter of the lesions ranged from 5 to 105 mm. For the first two types (solitary and multifocal nodular types), the CT findings included low density lesions with clear margins on non-contrast scans, centripetal enhancement in arterial phase, and homogeneous enhancement in the portal venous and delay phases. The findings of non-contrast MRI scans for these two types included low signal intensity on T1-weighted images, heterogeneous high signal intensity on T2-weighted images, and heterogeneous high signal intensity on diffusion-weighted images. The lesions were predominantly located in submarginal areas. On contrast-enhanced MRI, the findings for the first two types included peripheral ring-like enhancement with a central low signal intensity (‘black target-like’ sign) and a central enhanced core surrounded by a low signal intensity halo (‘white target-like’ sign). The findings for the third HEH type (diffuse type) on CT and MRI scans included low density or heterogeneous signal intensity lesions involving regions of part or the whole liver, coalescent lesions (‘strip-like’ sign), and gradual enhancement along central vessels (‘lollipop’ sign). Collectively, these findings indicate that the ‘white target-like’ sign, ‘black target-like’ sign, ‘lollipop’ sign and ‘strip-like’ sign, in addition to capsular contraction and submarginal location, on CT and MRI imaging may have implications for the diagnosis of HEH. Furthermore, a variety of MRI sequences may provide additional information for the differential diagnosis of HEH.
The development of a multiplexed DNA detection assay has been of great interest in gene-expression profiling, drug screening, clinical diagnostics, and the detection of pathogens. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] However, it is still a challenging task to detect many different targets in one sample while retaining high target sensitivity. Restriction enzymes that can recognize and cleave specific double-stranded DNA (dsDNA) sequences have been widely used in molecular biology and genetic engineering. [16] Over 2000 site-specific endonucleases have been identified so far. Restriction enzymes have been used with DNA-modified gold nanoparticles (AuNPs) in various applications, such as release of the particle from the surface, conformational effects of nanoparticles on bioactivity, nanoparticle assembly and disassembly, and optimal conditions of efficient biomanipulation. [17][18][19][20][21][22] The availability of numerous enzymatic restriction DNA sequences as well as the high specificity of restriction enzymes could be very useful aspects in a multiplexed DNA detection assay.Herein, we report a restriction-enzyme-coded multiple DNA detection method using oligonucleotide-modified AuNPs and magnetic microparticles (MMPs; Figure 1). Different target DNA capture sequences were modified to each MMP probe, and the other half of the target DNA complements were modified to AuNP probes. Target DNA strands were then hybridized to form AuNPÀMMP sandwich complexes, and the AuNPÀMMP complexes were separated by a magnetic field ( Figure 1A and B). A specific, targethybridized DNA sequence can be recognized and cut by a specific restriction endonuclease. A series of restrictionenzyme-based release steps of DNA-modified AuNPs (BamHI for HAV target, SpeI for HBV target, and EcoRV for HIV target) were followed for the subsequent AuNP analysis. Released AuNPs were recovered by applying a magnetic field to remove MMPs and imaged by using dark-field microscopy, which allows counting of the released AuNPs ( Figure 1C and D). A great versatility in choosing DNA sequences and restriction enzymes provides a powerful tool for detecting a large number of different DNA strands in one solution. Importantly, dark-field nanoparticle analysis using a simple optical microscopy method allows imaging of individual particles and improves detection sensitivity over a fluorophore-based method, in which individual fluorophore imaging and analysis is a daunting task.As a proof-of-concept experiment, three different DNA sequences were used ( Figure 1A): hepatitis A virus Vall7 polyprotein gene (HAV: 5 0 -CAATTGAGGATCCAGTTT-TAGCAAAGAA-3 0 , recognized by BamHI), hepatitis B virus surface antigen gene (HBV: 5 0 -TCAGTTTACTAGTGC-CATTTGTTCAGTGGT-3 0 , recognized by SpeI), and human immunodeficiency virus gene (HIV: 5 0 -CTCGACAACTAG-GAAATCTATAGAAAGATA-3 0 , recognized by EcoRV); the underlined bases are restriction sites for each restriction enzyme. The multiplexed DNA detection assay involves two types of probes. The first is a DNA-modif...
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