Agent-free Method Research Articles

High dynamic range widefield fundus photography with transcranial illumination: A contrast agent-free method for non-mydriatic choroidal imaging

High dynamic range widefield fundus photography with transcranial illumination: A contrast agent-free method for non-mydriatic choroidal imaging

Improvement of UV aging resistance of PBAT composites with silica-immobilized UV absorber prepared by a facile method

Prolonging the service life of polymer materials by enhancing their aging resistance is an effective and practical way to reduce the polymer waste. In this work, to improve the migration resistance and thermal stability of commercial UV absorber used in polymer composites, a solvent & coupling agent-free method with only one-step reaction was proposed to immobilize a commercial UV absorber 2‑hydroxy-4-(octyloxy)benzophenone (UV-531) onto the surface of silica nano particles (SiO2). UV-531 was chemically bonded on the surface of SiO2 with the loading weight of 12%. The as-prepared immobilized UV-531 (SiO2–531) could be homogeneously dispersed in the matrix of poly(butylene adipate-co-terephthalate) (PBAT) and showed significantly improved migration resistance and thermal stability compared with free UV-531. For example, the initial decomposition temperature of SiO2–531 is about 200 °C higher than that of free UV-531. Therefore, PBAT/SiO2–531 composites showed even better anti-UV aging performance than PBAT/SiO2 composites with twofold added free UV-531 during accelerated ultraviolet weathering and long-term natural climatic aging tests. For example, PBAT/SiO2–531 composites can maintain higher retentions of tensile strength and elongation at break than PBAT/SiO2 composites with free UV-531 does after accelerated UV aging. Hopefully, the proposed facile method to enhance the anti-UV aging efficiency of commercial UV absorber may potentially uncover an extensive family of building blocks for constructing highly anti-aging plastic composites.

Prognostic value of coronary microvascular dysfunction assessed by coronary angiography-derived index of microcirculatory resistance in diabetic patients with chronic coronary syndrome

BackgroundCoronary microvascular dysfunction (CMD) is common and is associated with unfavorable cardiovascular events in patients with diabetes mellitus (DM). Coronary angiography-derived index of microcirculatory resistance (caIMR) is a recently developed wire- and hyperemic agent-free method to assess CMD. We aimed to investigate the prognostic impact of CMD assessed by caIMR on clinical outcomes in patients with DM and chronic coronary syndrome (CCS).MethodsCCS patients who underwent coronary angiography between June 2015 to May 2018 were included. Coronary microvascular function was measured by caIMR, and CMD was defined as caIMR ≥ 25U. The primary endpoint was major adverse cardiac events (MACE). Kaplan-Meier analysis and Cox proportional hazards models were used to assess the relationship between caIMR and the risk of MACE.ResultsOf 290 CCS patients, 102 patients had DM. Compared with non-diabetic patients, CMD (caIMR ≥ 25U) was higher among DM patients (57.8% vs. 38.3%; p = 0.001). During a mean 35 months follow-up, 40 MACE had occurred. Patients with caIMR ≥ 25 had a higher rate of MACE than patients with caIMR < 25 (20.6% vs. 8.2%, p = 0.002). Of these, the MACE rate was higher among DM patients with caIMR ≥ 25 than those with caIMR < 25 (33.9% vs. 14.0%; p = 0.022). In multivariable Cox analysis, caIMR ≥ 25 was independently associated with MACE in the DM patients but not in non-DM patients (HR, 2.760; 95% CI, 1.066–7.146; P = 0.036).ConclusionCMD assessed by caIMR was common and is an independent predictor of MACE among diabetic patients with CCS. This finding potentially enables a triage of higher-risk patients to more intensive therapy.

Relaxation-compensated CEST (chemical exchange saturation transfer) imaging in breast cancer diagnostics at 7T

PurposeTo investigate whether fat-corrected and relaxation-compensated amide proton transfer (APT) and guanidyl CEST-MRI enables the detection of signal intensity differences between breast tumors and normal-appearing fibroglandular tissue in patients with newly-diagnosed breast cancer. MethodTen patients with newly-diagnosed breast cancer and seven healthy volunteers were included in this prospective IRB-approved study. CEST-MRI was performed on a 7 T-whole-body scanner followed by a multi-Lorentzian fit analysis. APT and guanidyl CEST signal intensities were quantified in the tumor and in healthy fibroglandular tissue after correction of B0/B1-field inhomogeneities, fat signal contribution, T1- and T2-relaxation; signal intensity differences of APT and guanidyl resonances were compared using Mann–Whitney-U-tests. Pearson correlations between tumor CEST signal intensities and the proliferation index Ki-67 were performed. ResultsAPT CEST signal in tumor tissue (6.70 ± 1.38%Hz) was increased compared to normal-appearing fibroglandular tissue of patients (3.56 ± 0.54%Hz, p = 0.001) and healthy volunteers (3.70 ± 0.68%Hz, p = 0.001). Further, a moderate positive correlation was found between the APT signal and the proliferation index Ki-67 (R2 = 0.367, r = 0.606, p = 0.11). Guanidyl CEST signal was also increased in tumor tissue (5.24 ± 1.85%Hz) compared to patients’ (2.42 ± 0.45%Hz, p = 0.006) and volunteers’ (2.36 ± 0.54%Hz, p < 0.001) normal-appearing fibroglandular tissue and a positive correlation with the Ki-67 level was observed (R2 = 0.365, r = 0.604, p = 0.11). APT and guanidyl CEST signal in normal-appearing fibroglandular tissue was not different between patients and healthy volunteers (p = 0.88; p = 0.93). ConclusionRelaxation-compensated and fat-corrected CEST-MRI allowed a non-invasive differentiation of breast cancer and normal-appearing breast tissue. Thus, this approach represents a contrast agent-free method that may help to increase diagnostic accuracy in MR-mammography.

Crystal-facet-controllable synthesis of Cu2O micron crystals by one-step, surfactant- and capping agent-free method and the formation mechanism

In this paper, well-defined polyhedral Cu2O crystals with different shapes were achieved by using different copper salts (including copper sulfate, copper chloride and copper acetate) and glucose as reactants. The growth process and formation mechanism were discussed in detail. The results indicated that at a low pH value, Cu4(OH)6(SO4), Cu2(OH)3Cl and CuO precursors were generated when CuSO4, CuCl2 and Cu(CH3COO)2 were used as reactants respectively. With the increase of pH value, the precursors decomposed and converted into Cu2O crystals with truncated octahedroal, octahedroal and cubic shapes in turn. In the formation of Cu2O crystal copper salt anions acted as the capping agents. According to the action of the charge, radius and concentration of the anion, the adsorption of anions on {111} facets follow the order: CH3COO− < SO42− < Cl−. This induces the increases of R value from 0.58, 1.15 to 1.73, thus Cu2O crystals show different morphology from cube, truncated octahedron to octahedron. When the reaction temperature of CuSO4 with glucose was set at 80 °C, the microcrystal Cu2O subunits with truncated octahedral shape self-organized on the preexisting octa-pods framework to form Cu2O crystal with octa-pods microcrystal polyhedral shape. The photocatalytic abilities of Cu2O crystals follow the order: cube＞octahedron＞truncated octahedron＞octa-pods microcrystal polyhedron, and the result was elucidated via DRS, PL and EIS analysis.

Physicochemical Trapping of Neurotransmitters in Polymer-Mediated Gold Nanoparticle Aggregates for Surface-Enhanced Raman Spectroscopy.

Because of the sharp distance dependence of surface-enhanced Raman spectroscopy (SERS), analyte molecules that do not exhibit strong affinity for Au/Ag often elude detection. New methods of integrating such analytes with SERS substrates are required to circumvent this limitation and expand the sensitivity of SERS to new molecules and applications. We communicate here a solution-phase, capture agent-free method of aggregating Au nanospheres in the presence of five neurotransmitters (dopamine, epinephrine, norepinephrine, serotonin, and histamine) and preventing sedimentation by encapsulating the aggregated nanospheres with polyvinylpyrrolidone, thereby trapping the neurotransmitters in close proximity to the Au nanospheres and enabling SER detection. The primary advantages of this physicochemical trapping method, which is generalizable to analytes beyond the scope of this work, are the high signal-to-noise ratio and spectral consistency down to nM levels. Normal Raman spectra and density functional theory calculations corroborate the accuracy of the spectra. Spectra collected over a wide range of concentrations were used to construct adsorption isotherms for all five neurotransmitters, from which adsorption dissociation constants were calculated, spanning from 5.7 × 10-4 M to 1.7 × 10-10 M. We expect this method to produce high quality SER spectra of any molecule with an Au affinity known or expected (based on functional groups) to be within that range. Our results have implications for plasmonic detection of these neurotransmitters, particularly for mixtures of those that exhibited disparate Au affinity in our study. We also present evidence that this method produces spectra of sufficient resolution to explore hypotheses related to surface adsorption behavior.

Cs-Beta with an Al-rich composition as a highly active base catalyst for Knoevenagel condensation

Ion-exchange of an Al-rich zeolite beta, synthesized by organic structure-directing agent-free method (Beta-OF), was studied for application as a base catalyst. While the as-synthesized Beta-OF in Na-form itself had base sites and showed moderate catalytic activity for Knoevenagel condensation, the ion-exchange with Cs+ improved the catalytic activity. For Knoevenagel condensation of benzaldehyde with ethyl acetoacetate, the catalytic activity of Beta-OF ion-exchanged with Cs+ largely surpassed that of the conventional zeolite beta with less Al content. CO2-TPD and IR observation with chloroform as a probe molecule revealed that the Cs-exchanged Beta-OF had strong base sites comparable to Cs-exchanged Y zeolite. Base strength of Beta-OF was stronger than that expected by Sanderson’s theory. A local high density of Al atoms in the framework of Beta-OF resulted in the unexpected base property and high catalytic activity.

Arterial Spin Labeling Cerebral Perfusion Magnetic Resonance Imaging in Migraine Aura: An Observational Study

Changes in cerebral perfusion during migraine with aura (MA) have been assessed mainly using dynamic susceptibility contrast (DSC) magnetic resonance perfusion imaging. A contrast agent-free method to assess these changes would be desirable. We assessed changes in cerebral perfusion during MA using arterial spin labeling (ASL) perfusion magnetic resonance imaging. We investigated 4 patients with a standardized protocol including ASL perfusion imaging during MA (n = 2) or early headache phase (n = 2) and asymptomatic follow-up. Semiquantitative evaluation was done using a region of interest (ROI) within hypoperfused or hyperperfused areas and corresponding ROIs in the contralateral hemisphere. Relative ratios of mean perfusion in the corresponding ROIs were calculated. DSC imaging was done at initial time points and compared visually with ASL findings. In all patients, regional perfusion changes were detected in the acute phase. These abnormalities did not respect the boundaries of major cerebral vascular territories but overlapped onto adjoining regions. During MA, adjacent hypoperfused and hyperperfused areas were found, whereas during headache, regional hyperperfusion only was observed. Perfusion abnormalities normalized on follow-up. ASL perfusion imaging is a contrast agent-free method suitable for assessment of reversible perfusion changes during or immediately after MA.

A simplified method to synthesize pure vanadium silicate analogue of ETS-10

High purity microporous vanadosilicate (EVS-10/AM-6) has been hydrothermally synthesised by a simple template-free, reducing agent-free method in the absence of titanosilicate ETS-10 seeds. Direct comparison between EVS-10 and ETS-10 showed successful isomorphous substitution of titanium with vanadium in the framework. The existence of vanadium is confirmed by energy dispersive X-ray spectroscopy and inductively coupled plasma mass spectrometry. The scan electron microscopy and the X-ray diffractometry show similar crystal morphology and similar molecular structure between the as-synthesised material and the ETS-10. Preliminary results indicate a similar internal surface area to ETS-10. Similar to ETS-10, EVS-10 may be useful for semiconductor and other electronic applications. This new simplified synthesis method may allow the economical production of EVS-10/AM-6 for quantum wire and other applications.

Direct Formation of Platinum Nanoparticles by Internally Isopropanol-Modified Dendritic Poly(amido amine)

We report a reducing agent-free method for preparing platinum (Pt) nanoparticles by internally isopropanol (IPA)-modified dendritic poly(amido amine) (PAMAM). The internally modified dendritic PAMAM were synthesized via divergent strategy using 1,3-diaminopropanol as a linking spacer, and NMR analyses confirm the embedded IPA moieties within the dendrimers by the appearance of characteristic proton and carbon resonances at 3.81 and 67.9 ppm, respectively. The in situ formation of stable Pt colloids was carried out by thermal treatment in the presence of internally modified dendritic PAMAM bearing either ester or alcohol peripherals, suggesting that the internal IPA functionalities dominate the reduction of Pt4+ ions. Moreover, the overall reducing rate was accelerated with increasing pH values. This result agreed with a reaction feature for preparing metal nanocomposites through polyol process in which basic environment facilitates the thermal-promoted reduction of metal ions accompanied with the oxidation of internal hydroxyl groups. The morphology of the dendrimer/Pt composite monitored by a transmission electron microscope (TEM) exhibited narrowly dispersed and roughly spherical shaped nanoparticles with a mean diameter of 5.4 nm.