Crude oil aggregation by microscopy and dynamic light scattering

This research is focused on establishing a methodology to evaluate the aggregation state of Mexican crude oil solutions from two different sources and SARA compositions, by using Dynamic Light Scattering (DLS). Different crude oil concentrations were established and monitored through time in order to determine their effects on the aggregation state. DLS results indicate that the aggregation state of the studied solutions is influenced by crude oil composition, specifically by the amount of resins. Particle size and elemental analysis of the aggregates were performed by Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX), respectively. Results from these techniques reveal particulated low-porosity smooth surfaces due to the presence of resin, as well as the determination of the characteristic elements found in asphaltenes. High-Resolution Transmission Electron Microscopy (HTEM) indicated the presence of asphaltene aggregates constituted by nanometric particles and asphaltene stacking as well as ultrafine nanocrystalline-oriented structures.     

Transformation of amorphous silica colloids to nanosized MEL zeolite

Si-MEL molecular sieve is prepared from aged colloidal precursor solutions under hydrothermal treatment (HT) at 90 °C. In situ dynamic light scattering (DLS) investigations of the precursor solutions and the crystalline Si-MEL sols are performed with the original concentrations. Sub-colloidal particles with a mean radius of about 1 nm and colloidal aggregates with a radius of 10 nm are detected in the precursor colloidal solutions after 5 h aging at room temperature. Consumption of the sub-colloidal particles with time and an increase of the colloidal fraction of 10 nm particles after 48 h aging is observed. After heating of the aged precursor solution at 90 °C for 30 h, three particle populations of 1, 10, and 100 nm radius are formed. Complete transformation from amorphous to crystalline colloidal particles is observed after 68 h extended HT of the aged precursor solution. The mean hydrodynamic radius of the crystalline Si-MEL particles is about 100 nm based on the DLS measurements. The size of the MEL crystals was also confirmed with SEM. Additional time-dependent ²⁹Si NMR measurements of the aged precursor colloidal solutions prior to further crystal growth show that the amount of Q⁰ species (δ=−71.2) decreases, while signals of high intensity in the range between δ=−88.6 and −98.9 indicating the formation of Q³₆ and Q³₈ silicon species appear. IR data reveal that with aging of the precursor colloidal solutions at room temperature, an increased ordering of the silica species similar to those found in the final MEL product is observed.     

可溶性交联大分子的合成及稀溶液行为

在浓溶液中合成了可溶性交联大分子（ICM）,研究了不同交联度,不同浓度下聚氨酯交联大分子,系列样品在溶液中的行为。发现这样的大分子在溶液中通过分子之间的物理作用易于相互粘接形成分子簇,且这种分子间作用的大小及其分布对交联度有很大的依赖。交联度不同的大分子,溶液行为有很大的差别。透射电镜显示交联大分子有着千差万别的特殊形状,这些形状还显示了交联大分子可能存在一个特殊的成长过程。     

ZrO2溶胶的醇盐受控水解-缩聚合成及光散射研究

采用一缩二乙二醇（DEG）修饰丙醇锆（Zr（OPr）4）的水解-缩聚过程,在乙醇（EtOH）介质中制备ZrO2基溶胶;借助小角X射线散射和激光动态光散射研究胶体微观结构对合成体系组成的依赖性。结果表明,DEG分子可以通过其端羟基与Zr（OPr）4发生亲核取代而形成稳定的配合中间体,有效抑制Zr（OPr）4的水解-缩聚过程,从而在很宽的组成范围内获得稳定的ZrO2基溶胶。此外,在稳定溶胶对应的组成范围内,随DEG引入量减少或反应H2O量增加,胶体粒子数量增大并形成团簇。受胶粒表面未水解的DEG配体残留的影响,胶粒之间通过表面羟基缩合迅速长大的几率很小。     

Efficient loading and entrapment of tamoxifen in human serum albumin based nanoparticulate delivery system by a modified desolvation technique

Herein, the poorly water-soluble drug, Tamoxifen (Tmx), was loaded in the amphipathic matrix of human serum albumin (HSA) nanoparticles by a modified desolvation method. In order to enhance the drug loading (DL) and drug entrapment efficiency (DEE) (<2% and 10%, respectively), ultrasonication of Tmx-HSA mixture was performed prior to desolvation process. Tmx loading and entrapment efficiency were optimized by employment of the response surface methodology (RSM)-central composite design (CCD) of experiments. Under the optimum conditions of 1.59 mg Tmx/ml concentration, 7.76 pH and 5 h incubation of HSA-Tmx, the DL of 6.7% and DEE of 74% are achievable. Particles with the average size of 195 nm, zeta potential of −21 mV and polydispersity index of 0.09 were produced under these conditions. A more sustained Tmx release behavior was observed from polyethylene glycol (PEG) conjugated nanoparticles in comparison to the non-PEGylated ones. The short-term stability investigation showed no alteration in physicochemical properties of nanoparticles at 4 and 37 °C, but small increase in nanoparticles size was observed after three months of storage at room temperature. This is the first report for efficient production of a Tmx delivery system based on HSA nanoparticles.     

Micellar Properties of Surface Active Ionic Liquid Lauryl Isoquinolinium Bromide and Anionic Polyelectrolyte Poly(Acrylic Acid Sodium Salt) in Aqueous Solution

The complex formation between anionic polyelectrolyte poly(acrylic acid sodium salt) [NaPAA] and surface active ionic liquid (SAIL) lauryl isoquinolinium bromide [C₁₂iQuin][Br] in aqueous media has been investigated by surface tension, isothermal titration calorimetry (ITC), and conductance. The self‐assembled structures have been characterized using dynamic light scattering (DLS) and turbidity measurements. A range of surface parameters have been calculated from tensiometric measurements including critical micelle concentration (CMC), surface excess concentration (Γ_cmc), surface pressure at the interface (Π_cmc), minimum area occupied at air–solvent interface (A_min), adsorption efficiency (pC₂₀), and surface tension at the CMC (γ_cmc). The thermodynamic parameters, i.e., standard enthalpy of micellization , standard free energy of micellization (), and standard entropy of micellization () have also been evaluated. Four different stages of transitions, corresponding to the progressive formation of NaPAA–[C₁₂iQuin][Br] complex (C₁)_, critical aggregation concentration (CAC), critical saturation concentration (C₃) and CMC have been observed owing to strong electrostatic and hydrophobic interactions. The results obtained from DLS and turbidity measurements show that size of the aggregates first decreases and then increases in the presence of polyelectrolyte. The binding isotherms obtained using isothermal titration calorimetry (ITC) show the concentration dependence as well as the highly cooperative nature of interactions corresponding to formation of polyelectrolyte–SAIL complexes.     

Drug self-assembly: A phenomenon at the nanometer scale with major impact in the structure–biological properties relationship and the treatment of disease

Under water-rich conditions, small amphiphilic and hydrophobic drug molecules self-assemble into supramolecular nanostructures. Thus, substantial modifications in their interaction with cellular structures and the ability to reach intracellular targets could happen. Additionally, drug aggregates could be more toxic than the non-aggregated counterparts, or vice versa. Moreover, since self-aggregation reduces the number of effective “monomeric” molecules that interact with the target, the drug potency could be underestimated. In other cases, the activity could be ascribed to the non-aggregated molecule while it stems from its aggregates. Thus, drug self-assembly could mislead from drug throughput screening assays to advanced preclinical and clinical trials. Finally, aggregates could serve as crystallization nuclei. The impact that this phenomenon has on the biological performance of active compounds, the inconsistent and often controversial nature of the published data and the need for recommendations/guidelines as preamble of more harmonized research protocols to characterize drug self-aggregation were main motivations for this review. First, the key molecular and environmental parameters governing drug self-aggregation, the main drug families for which this phenomenon and the methods used for its characterization are described. Then, promising nanotechnology platforms investigated to prevent/control it towards a more efficient drug development process are briefly discussed.