A New Class of Smart Gadolinium Contrast Agent for Tissue pH Probing Using Magnetic Resonance Imaging.

: Detecting tissue pH in vivo is extremely vital for medical diagnosis and formulation of treatment decisions. To this end, many investigations have been carried out to develop an accurate and efficient method of in vivo pH measurement. Most of the techniques developed so far suffer from inadequate accuracy, due to poor sensitivity at low concentration of the target or nonspecific interactions within the tissue matrix. To overcome these issues, we describe herein the development of a simple, yet reliable, way to estimate pH with high precision using a Gd(III)-DOTA-silyl-based acid-labile group as a pH-sensitive contrast agent with Magnetic Resonance Imaging (MRI). With this method, a change in T1 weighted image intensity of the newly developed pH-sensitive contrast is directly linked to the proton concentration in the media. As a result, we were able estimate the pH of the target with 95% reliability.

Recoverable and reusable light-induced multi-arm azobenzenes-Fe3O4 hybrid sorbent for enrichment of phthalate plasticizer and utilized as a SALDI substrate for the detection of 2-naphthol.

The construction, structural identifications along with compositional properties, using TEM, FT-IR, and XPS spectroscopies, of an innovative light-induced multi-arm azobenzenes based Fe3O4 magnetic nanoparticles (Azo-Fe3O4 MNPs) are being reported. Such organic (light-sensitive dendrimers-like structure), inorganic (magnet core), hybrid material has been applied as an efficient recoverable/reusable extractive sorbent for the detection of phthalate plasticizers from acetate buffer solution. The extraction study was controlled within consecutive procedures via UV-light exposure to achieve pore-size control which then further subjected for the evaluation of the analytes' retention, separation, and release as well as the detection of the phthalate pollutants using GCMS-. Various experimental conditions, such as time of extraction, salt concentration, pH, and desorption time, were studied and adjusted. Additionally, the extraction repeatability (RSD from 0.46 % to 6.12%, n = 5) of the studied sorbent was comparable to other published work. The linear range extended from 6.25 to 100 µg L-¹ and detection limits (LOD) within the range of 41- 150 ng L-1 were achieved, demonstrating good linearity with values ranging from 0.9992 to 0.9892. The inter-batch and intra-batch RSD ranged from 0.46 % to 6.12 %, respectively. Additionally, it provides effective detection of 2-naphthol when used as a SALDI substrate.

A chromia-based sorbent for the enrichment of phosphotyrosine.

Developing of new core@shell particles (CSPs) bearing metal oxides on their outer surfaces is of a great interest. Such hybrid systems have many benefits, i.e., low cost, operation simplicity, chemical stability and tunability along with simple recoverability and reusability that make them suitable as dispersive solid phase extraction (DSPE) sorbents for selecting/extracting different types of molecular structures. Accordingly, herein, novel chromia-based CSPs were successfully prepared and utilized as efficient DSPE for selective enrichment toward phosphotyrosine (pTyr). A modified version of Stöber method was used to prepare highly dispersed core particles that were further coated with the chromium oxide. The outer shell surface morphology and thickness of SiO2@Cr2O3-CSP system were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), whereas the surface functionalities were determined using X-ray photoelectron spectroscopy (XPS), FT-IR spectroscopy and zeta potential. The prepared chromia sorbent showed a significant improvement in extracting a probe-analyte (pTyr) compared to the results obtained by titania-based counterparts. As well to this, a noticeable stability of the SiO2@Cr2O3-CSP sorbent was remarkably achieved which upon simple solvent-wash cycles, the studied sorbent can be regenerated/reused. Noticeably low-levels of LOD and LOQ (3.0 and 15 pg mL-1) were attained with good linearity (R2 of 0.9995), batch-to-batch reproducibility (RSD% ≤ 10) and run-to-run repeatability (RSD% ≤ 5.5).

Synthesis and characterization of aramid composites reinforced with silanized graphene platelets.

The synthesis and characterization of aramid composites reinforced with graphene platelets are reported. Hydroxy-functionalised graphene platelets were modified with two sol-gel binders (aminopropyl- or aminophenyl-trialkoxysilanes) and then chemically linked with aramid chains. The effect of the two sol-gel binders on the physiochemical and mechanical properties was evaluated. Chemical changes during the sol-gel reaction and subsequent amidation process in the nano-composite preparation were evaluated by the XPS and FTIR analyses. Thin films of these composites with different proportions of graphene were prepared. Morphology of the hybrids prepared was studied by the SEM technique. Properties of the composite films were studied by dynamical mechanical thermal (DMT) analysis to measure their glass transition temperature (T g) and storage modulus. These properties have been compared with previously reported values using pristine graphene (Gr) as a filler. The increase in thermal mechanical properties on addition of silanized graphene (SiGr) showed a large shift in the T g and more increase in storage modulus by chemically binding SiGr sheets on the aramid chains. Aminophenyl-trialkoxysilane was found to give better results due to the presence of phenyl groups which were more rigid than propyl groups present in aminopropyl-trialkoxysilane. The effect of chemical bonding and the possible π-π secondary bond interactions between the matrix and graphene platelets on the properties of the resulting hybrids are discussed.

Aramid-wrapped CNT hybrid sol-gel sorbent for polycyclic aromatic hydrocarbons.

This work describes the preparation of an analytical microextraction sorbent using a simple and versatile sol-gel hybrid composite, i.e., aramid oligomers wrapping multi-walled carbon nanotubes (CNTs) covalently bonded to a porous silica network. To overcome the inherent shortcomings of the CNTs' solubility and dispersion in both organic phases and in the sol-gel solution, the outer surface of the CNTs was initially functionalized with carboxylic acid groups and then reacted with both aramid oligomers and 3-aminopropyl triethoxysilane (APTES). The obtained sorbent was characterized by FT-IR, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). Using sol-gel chemistry, the functionalized CNTs were coated onto SPME fibers and used in conjunction with GC-MS for the analysis of polycyclic aromatic hydrocarbons (PAHs) in water and soil samples. Excellent repeatability (run-to-run RSD% ∼ 8) and reproducibility (fiber-to-fiber RSD% ∼ 6) were achieved in addition to low LODs (0.10-0.30 ng mL-1) and noticeable recovery%. The present method of sorbent preparation led to enhanced thermal and chemical stabilities, a long sorbent lifetime and good affinity towards PAHs. Moreover, the present sorbent enhanced the extraction capability by more than 30% compared to that of commercially available PDMS counterparts.

Sol-gel microextraction phases for sample preconcentration in chromatographic analysis.

Sol-gel technology provides a simple and reliable method for solid-phase microextraction (SPME) fiber preparation through in situ creation of surface-bonded organic-inorganic hybrid coatings characterized by enhanced thermal stability and solvent-resistance properties that are important for the coupling of SPME with GC and HPLC, respectively. The sol-gel coating technology has led to the development of an extensive array of sol-gel sorbent coatings for SPME. In this article, sol-gel microextraction coatings are reviewed, with particular attention on their synthesis, characterization, and applications in conjunction with GC and HPLC analyses. In addition, the development of sol-gel-coated stir bars, their inherent advantages, and applications are discussed. Next, the development and applications of sol-gel capillary microextraction (CME) in hyphenation with GC and HPLC is extensively reviewed. The newly emerging germania- and titania-based sol-gel microextraction phases look promising, especially in terms of pH and hot solvent stability. Finally, sol-gel monolithic beds for CME are reviewed. Such monolithic beds are in a position to greatly improve the extracting capabilities and enhanced sensitivity in CME.

Nonhydrolytic sol-gel approach to facile creation of surface-bonded zirconia organic-inorganic hybrid coatings for sample preparation. Ι. Capillary microextraction of catecholamine neurotransmitters.

Nonhydrolytic sol-gel (NHSG) route was used for the creation of novel zirconia-polypropylene oxide (ZrO2-PPO) sol-gel hybrid sorbents in the form of surface coatings for the extraction and preconcentration of catecholamine neurotransmitters and molecules structurally related to their deaminated metabolites. In comparison to other sorbents made of inorganic transition metal oxides, the presented hybrid organic-inorganic sorbents facilitated reversible sorption properties that allowed for efficient desorption of the extracted analytes by LC-MS compatible mobile phases. The presented sol-gel hybrid sorbents effectively overcame the major drawbacks of traditional silica- or polymer-based sorbents by providing superior pH stability (pH range: 0-14), and a variety of intermolecular interactions. Nonaqueous sol-gel treatment of PPO with ZrCl4 was employed for the derivatization of the terminal hydroxyl groups on PPO, providing zirconium trichloride-containing end groups characterized by enhanced sol-gel reactivity. NHSG ZrO2-PPO sorbent provided excellent microextraction performance for catecholamines, low detection limits (5.6-9.6pM), high run-to-run reproducibility (RSD 0.6-5.1%), high desorption efficiency (95.0-99.5%) and high enrichment factors (∼1480-2650) for dopamine and epinephrine, respectively, extracted from synthetic urine samples. The presented sol-gel sorbents provided effective alternative to conventional extraction media providing unique physicochemical characteristics and excellent extraction capability.