Copolymeric nano/microgels of N-isopropylacrylamide and carboxyalkyl methacrylamides: Effect of methylene chains and the ionization state of the weak acids on size and sensitivity to pH and temperature

ABSTRACT

We prepared nano/microgels by precipitation copolymerization of N-isopropylacrylamide (NIPAAm), and one of three different carboxyalkyl methacrylamides [methacryloylamido hexanoic acid (M₅), 8-methacryloylamido octanoic acid (M₇), and 11-methacryloylamido undecanoic acid (M₁₀)], either in the acid forms or as carboxylates (potassium salts). The hydrodynamic diameter (Dh) of the nano/microgels prepared with the carboxylates was smaller (≈100 nm for M₁₀ copolymers), compared to the size of homopolymeric NIPAAm microgels prepared by dispersion polymerization (around 600 nm), indicating that the carboxylates act as surfactants reducing the size of the seeds during the polymerization process. These materials presented a swollen-shrunken transition temperature (T _tr) similar to the T _tr of the homopolymeric NIPAAm microgels, without pH sensitivity. On the other hand, the copolymeric microgels prepared from the acid form of the comonomers have a similar or bigger size than NIPAAm microgels. For these copolymers, the T _tr can be tuned by the type and proportion of acid comonomer used and present pH sensitivity. This is important for biomedical applications such as positive temperature control release. Polyelectrolyte titration demonstrates that the nano/microgels prepared with the carboxylates behave as hard spheres, while the microgels prepared with the weak acid behave as porous materials.     

Searching for Potential Markers of Glomerulopathy in Urine by HS-SPME-GC×GC TOFMS

Volatile organic compounds (VOCs) exiting in urine are potential biomarkers of chronic kidney diseases. Headspace solid phase microextraction (HS-SPME) was applied for extraction VOCs over the urine samples. Volatile metabolites were separated and identified by means of two-dimensional gas chromatography and time of flight mass spectrometry (GC × GC TOF MS). Patients with glomerular diseases (n = 27) and healthy controls (n = 20) were recruited in the study. Different VOCs profiles were obtained from patients and control. Developed methodology offers the opportunity to examine the metabolic profile associated with glomerulopathy. Four compounds found in elevated amounts in the patients group, i.e., methyl hexadecanoate; 9-hexadecen-1-ol; 6,10-dimethyl-5,9-undecadien-2-one and 2-pentanone were proposed as markers of glomerular diseases.     

Combined Experimental and Multivariate Model Approaches for Glycoalkaloid Quantification in Tomatoes

The intake of tomato glycoalkaloids can exert beneficial effects on human health. For this reason, methods for a rapid quantification of these compounds are required. Most of the methods for α-tomatine and dehydrotomatine quantification are based on chromatographic techniques. However, these techniques require complex and time-consuming sample pre-treatments. In this work, HPLC-ESI-QqQ-MS/MS was used as reference method. Subsequently, multiple linear regression (MLR) and partial least squares regression (PLSR) were employed to create two calibration models for the prediction of the tomatine content from thermogravimetric (TGA) and attenuated total reflectance (ATR) infrared spectroscopy (IR) analyses. These two fast techniques were proven to be suitable and effective in alkaloid quantification (R² = 0.998 and 0.840, respectively), achieving low errors (0.11 and 0.27%, respectively) with the reference technique.     

Importance of van der Waals interaction for organic molecule-metal junctions: adsorption of thiophene on Cu(110) as a prototype

We report ab initio calculations for the interface energetics of a weakly adsorbed organic molecule on a metal surface, which serves as a model interface relevant for organic electronics. The studied thiophene ring is found to be physisorbed on the Cu(110) surface with an adsorption energy of -0.50 eV. Nonlocal correlations, i.e., van der Waals interactions, are solely responsible for the binding in this weakly interacting system, and the choice of the proper exchange-correlation function is crucially important. The adsorption of thiophene lowers the metal work function due to the formation of surface dipoles while no sizable charge transfer is found.     

SHESSLOC: A selective variation of the FUCOUP sequence

In this paper we carried out a comparison between all the possible selective versions of the basic heteronuclear correlation experiment, the FUCOUP sequence. We concluded that the best experiment is that one in which the selective pulse is given in the carbon dimension, which we called SHESSLOC (Selective HEteronuclear Simultaneous Short and LOng-range Correlations). The sensitivity of the sequence was improved with the introduction of pulsed field gradients.     

Diagnostic cellular organization features extracted from autofluorescence images

Depth-resolved NADH autofluorescence images are shown to differentiate between normal and precancerous engineered tissues. An inverse power law behavior of the power spectral density (PSD) of these images is observed, indicating a self-affine organization of mitochondrial NADH at length scales 1-10 microm. Power exponents of the PSD functions vary significantly with tissue depth and precancerous state, giving insight into the morphological changes associated with precancerous lesions and providing substantial potential for noninvasive clinical diagnosis of squamous epithelial lesions and tumors.     

Stereoselective methadone disposition after administration of racemic methadone to anesthetized Shetland ponies assessed by capillary electrophoresis

The enantioselectivity of the pharmacokinetics of methadone was investigated in anesthetized Shetland ponies after a single intravenous (0.5 mg/kg methadone hydrochloride; n = 6) or constant rate infusion (0.25 mg/kg bolus followed by 0.25 mg/kg/h methadone hydrochloride; n = 3) administration of racemic methadone. Plasma concentrations of l -methadone and d -methadone and their major metabolites, l - and d -2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP), respectively, were analyzed by CE with highly sulfated γ-cyclodextrin as chiral selector and electrokinetic analyte injection from liquid/liquid extracts prepared at alkaline pH. In both trials, the d -methadone concentrations were lower than those of l -methadone and the d -EDDP levels were lower than those of L-EDDP. For the case of a single intravenous bolus injection, the plasma concentration versus time profile of methadone enantiomers was analyzed with a two-compartment pharmacokinetic model. l -methadone showed a slower elimination rate constant, a lower body clearance, and a smaller steady-state volume of distribution than d -methadone. d -methadone and d -EDDP were eliminated faster than their respective l -enantiomers. This is the first study that outlines that the disposition of racemic methadone administered to anesthetized equines is enantioselective.     

Magnetic Titanium Dioxide Nanocomposites for Surface‐Enhanced Resonance Raman Spectroscopic Determination and Degradation of Toxic Anilines and Phenols

Mesoporous M‐TiO₂ NCs, functionalized by PATP, can capture toxic anilines and phenols by azo coupling. Loading these nanodevices with Ag NPs offers the possibility for a sensitive quantitative determination of target compounds by SERRS spectroscopy, which allows multiplex detection because of the specific vibrational fingerprints. Sensitivity and selectivity can be further enhanced by concentrating the hybrid particles by an external magnet and compound‐specific binding (anilines versus phenols). The bound toxic compounds can be degraded by TiO₂‐assisted photocatalysis after removal of the loaded hybrid particles from the sample solution with an external magnet. The degradation process can be enhanced in the presence of plasmonic Ag nanostructures.     

Molecular Parameters and Transmembrane Transport Mechanism of Imidazolium‐Functionalized Binols

We describe the molecular parameters governing the transmembrane activity of imidazolium‐functionalized anion transporters and present a detailed mechanistic study. These ionophores adopt a mobile‐carrier mechanism for short methyl and butyl chains, a combined mobile‐carrier/transmembrane‐pore mechanism for octyl and dodecyl chains, and form transmembrane aggregates for hexadecyl chains.