Laser Light Scattering Research Articles

In vitro drug release and biological evaluation of biomimetic polymeric micelles self-assembled from amphiphilic deoxycholic acid–phosphorylcholine–chitosan conjugate

Novel biomimetic amphiphilic chitosan derivative, deoxycholic acid–phosphorylcholine–chitosan conjugate (DCA–PCCs) was synthesized based on the combination of Atherton–Todd reaction for coupling phosphorylcholine (PC) and carbodiimide coupling reaction for linking deoxycholic acid (DCA) to chitosan. The chemical structure of DCA–PCCs was characterized by 1H and 31P nuclear magnetic resonance (NMR). The self-assembly of DCA–PCCs in water was analyzed by fluorescence measurements, dynamic laser light-scattering (DLS), zeta potential and transmission electron microscopy (TEM) technologies. The results confirmed that the amphiphilic DCA–PCCs can self-assemble to form nanosized spherical micelles with biomimetic PC shell. In vitro biological evaluation revealed that DCA–PCCs micelles had low toxicity against NIH/3T3 mouse embryonic fibroblasts as well as good hemocompatibility. Using quercetin as a hydrophobic model drug, drug loading and release study suggested that biomimetic DCA–PCCs micelles could be used as a promising nanocarrier avoiding unfavorable biological response for hydrophobic drug delivery applications.

Solution crystallization analysis of poly(lactic acid) by Scalls: A facile approach for thermal analysis of polymers in solution

Non-isothermal solution crystallization and dissolution behaviour of both enantiomers (D and L) of poly(lactic acid) (PLA) and their blends were studied by the unique Solution Crystallization Analysis by Laser Light Scattering (Scalls) method. For the first time, we have investigated the crystallization of this biopolymer in solution, as well as the subsequent dissolution or “solution melting”. It was found that addition of the D-enantiomer (PDLA) to the L-enantiomer (PLLA) in solution resulted in the formation of stereocomplex crystals (SC), and the nucleation-effect of the crystals was intensified with increase in PDLA content, leading to an earlier onset of crystallization and increased crystallization peak area. Differential Scanning Calorimetry (DSC) analysis confirmed the formation of SC during solution crystallization. Large re-crystallization events were seen for the pristine polymers, indicative of their low crystallization rates. Overall, results obtained by Scalls provided promising information regarding PLA crystallization kinetics, which significantly influences practical applications of this biopolymer.

Migration of nanoparticles from plastic packaging materials containing carbon black into foodstuffs

Carbon black was investigated to assess and quantify the possibility that nanoparticles might migrate out of plastic materials used in the food packaging industry. Two types of carbon black were incorporated in low-density polyethylene (LDPE) and polystyrene (PS) at 2.5% and 5.0% loading (w/w), and then subjected to migration studies. The samples were exposed to different food simulants according to European Union Plastics Regulation 10/2011, simulating long-term storage with aqueous and fatty foodstuffs. Asymmetric flow field-flow fractionation (AF4) coupled to a multi-angle laser light-scattering (MALLS) detector was used to separate, characterise and quantify the potential release of nanoparticles. The AF4 method was successful in differentiating carbon black from other matrix components, such as extracted polymer chains, in the migration solution. At a detection limit of 12 µg kg−1, carbon black did not migrate from the packaging material into food simulants. The experimental findings are in agreement with theoretical considerations based on migration modelling. From both the experimental findings and theoretical considerations, it can be concluded that carbon black does not migrate into food once it is incorporated into a plastics food contact material.

Synthesis and characterization of a renewable cyanate ester/polycarbonate network derived from eugenol

A homogenous polycarbonate/cyanate ester network has been prepared from a renewable, eugenol-derived bisphenol. The pure polycarbonate exhibited a Tg of 71 °C, Mn = 8360, and polydispersity of 1.88. An 80:20 blend of cyanate ester: polycarbonate was prepared and thermally cured. The presence of the polycarbonate had no significant effect on the cure behavior of the cyanate ester. Small Angle Laser Light Scattering (SALLS) and DSC were used to analyze the blend and no phase separation was observed either during or after cure, suggesting that a homogenous network was generated. TMA of the resulting composite material revealed a single Tg of 132 °C (tan δ), roughly 55 °C lower than the Tg of the pure polycyanurate and 60 °C higher than the polycarbonate. A solvent extraction study showed that the polycarbonate could be quantitatively separated from the thermoset matrix after cure. This result proved that no chemical grafting occured under the cure conditions employed. The excellent miscibility of the polycarbonate and cyanate ester coupled with the efficient cure of the blend to a homogenous network suggests that these types of blends may have applications for fabrication of toughened composite structures.

Construction of polyelectrolyte-responsive microgels, and polyelectrolyte concentration and chain length-dependent adsorption kinetics.

We report on the construction of a polyelectrolyte-responsive system evolved from sterically stabilized protonated poly(2-vinylpyridine) (P2VPH(+)) microgels. Negatively charged sodium dodecylbenzenesulfonate (SDBS) surfactants could be readily internalized into the cationic microgels by means of electrostatic interactions, resulting in microgel collapse and concomitant formation of surfactant micellar domains (P2VPH(+)/SDBS)-contained electrostatic complexes. These internal hydrophobic domains conferred the opportunity of fluorescent dyes to be loaded. The obtained fluorescent microgel complexes could be further disintegrated in the presence of anionic polyelectrolyte, poly(sodium 4-styrenesulfonate) (PNaStS). The stronger electrostatic attraction between multivalent P2VPH(+) microgels and PNaStS polyelectrolyte than single-charged surfactant led to triggered release of the encapsulated pyrene dyes from the hydrophobic interiors into microgel dispersion. The process was confirmed by laser light scattering (LLS) and fluorescence measurements. Furthermore, the entire dynamic process of PNaStS adsorption into P2VPH(+) microgel interior was further studied by stopped-flow equipment as a function of polyelectrolyte concentration and degree of polymerization. The whole adsorption process could be well fitted with a double-exponential function, suggesting a fast (τ1) and a slow (τ2) relaxation time, respectively. The fast process (τ1) was correlated well with the approaching of PNaStS with P2VPH(+) microgel to form a nonequilibrium complex within the microgel shell, while the slow process (τ2) was consistent with the formation of equilibrium complexes in the microgel deeper inside. This simple yet feasible design augurs well for the promising applications in controlled release fields.

A Progress in Development and Application of Size Exclusion Chromatograph/Multi-Angle Laser Light Scattering

This paper reveals the development and significance of size exclusion chromatograph/multi-angle laser light scattering(SEC-MALLS) for determination of the molecular weight and characterization of the molecular weight distribution. This technque has been applied in many aspects, such as biology, polymer and carboxylate surfactant. It has made a big contribution to study the property of macromolecular substances.

Synthesis and characterization of multi-responsive poly (NIPAm-co-AAc) microgels

Two samples of multi-responsive copolymer microgels, poly(N-isopropylacrylamide-co-acrylic acid) [P(NIPAm-co-AAc)], were synthesized by emulsion polymerization using different amounts of emulsifier. The unreacted monomers and surfactant were removed from the microgels by dialysis. Dynamic Laser Light Scattering (DLS) was used to determine the diffusion coefficient and hydrodynamic radius (Rh) of the microgels at different pH values and temperatures. At pH 7 the microgel showed rapid response to temperature and underwent volume phase transition (VPT) as the temperature was raised. At lower temperature the microgels were in the hydrated or swollen state but beyond 38oC, the size was abruptly decreased. Under different conditions of pH and NaCl concentrations, variations in VPTT values were noticed. By increasing pH the VPTT was increased but the addition of salt had an inverse effect. The weight average molar mass (Mw) and radius of gyration (Rg) were measured by Static Laser Light Scattering (SLS). FTIR spectroscopy was used to confirm the chemical structures of microgels

Biocatalytic designs for the conversion of renewable glycerol into glycerol carbonate as a value-added product

Abstract A comparative study of two different biocatalytic models, e.g. enzyme immobilized on magnetic particles (EIMP) and cross-linking enzyme aggregates onto magnetic particles (CLEMPA) was performed. The first model was designed as enzyme-immobilized on the magnetic particles surface (EIMP). The second model was constructed as a network structure with the enzyme aggregates and magnetic particles placed into the nodes and polyglutaraldehyde cross-linker as the network ledges. The design was called cross-linking enzyme aggregates onto magnetic particles (CLEMPA). The biocatalysts were prepared using lipase enzyme from Aspergillus niger for catalyzing the glycerol (Gly) conversion to glycerol carbonate (GlyC). The biocatalyst characteristics for both designs (EIMP and CLEMPA) were evaluated using scanning electron microscopy (SEM), laser light scattering (LLS) and UV-Vis techniques. The EIMP model was strongly influenced by the composition of the polymeric layer covering the particles surface, while the size of the magnetic particles affected mostly the CLEMPA design. Also, the biocatalytic capacity of the tested models was evaluated as maximum 52% Gly conversion with 90% GlyC selectivity for EIMP, and 73% Gly conversion with 77% GlyC selectivity for CLEMPA. Both biocatalytic models were successfully used to prepare GlyC from “crude” glycerol collected directly from the biodiesel process (e.g. 49% Gly conversion with 91% GlyC selectivity for EIMP and 70% Gly conversion with 80% GlyC selectivity for CLEMPA).

Comparative study on molecular size, multi‐branched structure, and chain conformation of amylopectins from three rice cultivars

Molecular size, multi‐branched structure, and chain conformation of amylopectins from indica (Ir‐AP), japonica (Jr‐AP), and glutinous rice (Gr‐AP) were investigated by laser light scattering (LLS), isoamylase debranching with gel permeation chromatography (GPC) separation and viscometry. The weight‐average molecular weight (Mw), radius of gyration (〈S2〉1/2), and intrinsic viscosities ([η]) in DMSO at 25°C were measured separately for Ir‐AP (4.72 ± 0.15 × 107, 163.70 ± 2.1 nm and 456.47 mL/g), Jr‐AP (6.61 ± 0.41 × 107, 170.40 ± 2.6 nm and 569.68 mL/g), and Gr‐AP (2.35 ± 0.34 × 108, 253.20 ± 16.3 nm and 926.08 mL/g). The Gr‐AP showed a dramatically lower overlapping concentration (c* = 1/(A2Mw), 1.40 × 10−4 g/mL) than Ir‐AP and Jr‐AP (1.13 × 10−3 g/mL and 1.04 × 10−3 g/mL), indicating that the first had more entanglements between macromolecular chains than the latter two. Based on the cluster model and A:B chain ratios, the Gr‐AP had more branched chains and longer internal‐chains than Ir‐AP and Jr‐AP. In view of polymer solution theory, the molecular parameters of ρ (viscometric radius Rη/〈S2〉1/2) and σ (A2Mw/[η]) revealed that Ir‐AP, Jr‐AP, and Gr‐AP existed as hyperbranched chains occupying a spherical volume and the first two presented a star‐like branched conformation in DMSO. This research provides the insights into multi‐branched structure and chain conformation of AP as well as a theoretical basis for interpretation of AP functional properties associated with their molecular structure.

Surfactant-mediated settleability and dewaterability of activated sludge

The activated sludge process is widely used for wastewater treatment, and the settleability and dewaterability of activated sludge are crucial to the operation of wastewater treatment plants. In this study the surfactant-mediated settleability and dewaterability of activated sludge were investigated. It is found that dose of anionic surfactant sodium dodecyl sulfate (SDS) caused substantial release of extracellular polymer substances (EPS), especially proteins, from sludge. Laser light scattering (LLS) results reveal that the released EPS became stretched and more expanded when the SDS dosage was increased. The sludge dewaterability was significantly deteriorated at a dosage of 2.084g/L SDS, and meanwhile the capillary suction time (CST) and specific resistance of filtration (SRF) increased by 6.3 and 5.1 times, respectively, than the raw sludge. The correlations between the EPS contents and the sludge properties, i.e., CST, SRF, moisture content of filter-cake and sludge volume index, were evaluated and the significant roles of proteins in governing the EPS properties as well as the settleability and dewaterability of sludge were further confirmed. This study elucidates how the settleability and dewaterability of activated sludge were affected by surfactants via changing the properties and structure of the released EPS from sludge.

Mapping Phase Diagrams of Polymer Solutions by a Combination of Microfluidic Solution Droplets and Laser Light-Scattering Detection

Conventional mapping of a phase diagram of a polymer in a solvent requires a substantial amount of polymer (e.g., at least of the order of ∼100 mg of narrowly distributed samples with different molar masses) and may take months or even years to reach the true two phase equilibrium at each given temperature, especially when the polymer concentration is high. This is why good phase diagrams of polymer solutions are rare in the literature. To solve such a problem, we developed a Teflon microfluidic device to prepare and store a series of droplets (∼10 nL) at different polymer concentrations inside a glass capillary. The phase transition inside each polymer solution droplet sealed and isolated in immiscible fluorohydrocarbon could be quickly and precisely monitored by a newly developed small angle laser light scattering detector. Using poly(vinyl acetate) (PVAc) in isobutyl alcohol and in benzene as two examples, we demonstrated that a combination of microfluidic device and small angle light scattering enables us to map the phase diagram of a polymer in a given solvent within hours by using only a few mg of the sample because (1) each droplet contains no more than ∼10 μg polymer and (2) the phase-transition induced interchain association inside each droplet can be quickly and sensitively detected. We have demonstrated that two sets of a total of eight precisely mapped phase diagrams of four PVAc fractions in the two solvents can be reasonably scaled together to form a master curve.

Preparation and characterization of paclitaxel-loaded PLDLA microspheres

Paclitaxel (Taxol®), is a drug used to treat ovarian, breast, lung and bladder cancer. However, the low solubility of this drug in water is a major limitation in its clinical use. One strategy to overcome this limitation would be to encapsulate paclitaxel in polymeric microspheres that are biocompatible and can be used as drug carriers. The aim of this study was to use the bioresorbable, biocompatible copolymer poly-L-co-D,L-lactic acid (PLDLA) in the 70:30 rate to produce and characterize microspheres containing paclitaxel. The simple emulsion technique was used to obtain spherical microspheres that were studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The average size of PLDLA microspheres without and with paclitaxel was 10.3 ± 1.7 μm and 12.7 ± 1.3 μm, respectively, as determined by laser light scattering (LLS). Differential scanning calorimetry (DSC) showed that pure paclitaxel had an endothermic peak corresponding to a melting point of 220 °C, which indicated its crystalline nature. The same peak was observed in a physical mixture of PLDLA + paclitaxel in which both components were present in the same proportions used to prepare the microspheres . In contrast, this peak was not observed for the drug, indicating that paclitaxel did not crystallize in PLDLA microspheres. Differential scanning calorimetry (DSC) indicated that paclitaxel was homogeneously dispersed in the PLDLA microspheres, the incorporation of paclitaxel into the microspheres did not alter the thermal properties of PLDLA. The Fourier transform infrared spectroscopy (FTIR) analysis seems to indicate the absence of chemical interaction between polymer and drugs in microspheres and the presence of drugs as a molecular dispersion in the polymer matrix. The efficiency of paclitaxel encapsulation in PLDLA microspheres was 98.0 ± 0.3%, as assessed by high performance liquid chromatography (HPLC). A kinetic study of drug release in vitro using HPLC showed an initial burst release followed by a slower release characteristic of large diameter distribution systems. PLDLA microspheres released 90 ± 4% of the drug over a 30-day period. These findings indicate that PLDLA microspheres are promising carriers for paclitaxel, with a potential for future applications in drug delivery systems.

The preliminary evaluation on cholesterol-modified pullulan as a drug nanocarrier

To further develop cholesterol-modified pullulan self-aggregated nanoparticles (CHSPNs) as a drug nanocarrier, CHSP was synthesized and characterized. Its cholesterol degree determined by 1H NMR was 5.2 cholesterol groups per hundred glucose units. CHSPNs were prepared in aqueous media and characterized by dynamic laser light-scattering (DLS), zeta potential and transmission electron microscopy (TEM). These nanoparticles were almost spherical in shape, and the zeta potentials of CHSPNs were near zero in aqueous media. CHSPNs can be stable at least 2 months with no significant size and zeta potential changes. Single dose toxicity test in mice was investigated for the safety evaluation of CHSPNs as a drug nanocarrier, and the result showed CHSPNs were well tolerated at the dose of 200 mg/kg in mice. Epirubicin (EPI)-loaded CHSPNs (EPI-CHSPNs) were prepared and the in vivo pharmacokinetics and biodistribution were studied. Compared with the EPI solution, EPI-CHSPNs have exhibited higher plasma drug concentration, longer half-life time (t1/2) and the larger area under-the-curve (AUC). Moreover, the drug level of EPI-CHSPNs increased in liver and decreased in heart. The results indicated that CHSPNs were stable, safe and may be a promising drug delivery carrier.

Structural analysis of glucans.

Glucans are most widespread polysaccharides in the nature. There is a large diversity in their molecular weight and configuration depending on the original source. According to the anomeric structure of glucose units it is possible to distinguish linear and branched α-, β- as well as mixed α,β-glucans with various glycoside bond positions and molecular masses. Isolation of glucans from raw sources needs removal of ballast compounds including proteins, lipids, polyphenols and other polysaccharides. Purity control of glucan fractions is necessary to evaluate the isolation and purification steps; more rigorous structural analyses of purified polysaccharides are required to clarify their structure. A set of spectroscopic, chemical and separation methods are used for this purpose. Among them, NMR spectroscopy is known as a powerful tool in structural analysis of glucans both in solution and in solid state. Along with chemolytic methods [methylation analysis (MA), periodate oxidation, partial chemical or enzymatic hydrolysis, etc.], correlation NMR experiments are able to determine the exact structure of tested polysaccharides. Vibration spectroscopic methods (FTIR, Raman) are sensitive to anomeric structure of glucans and can be used for purity control as well. Molecular weight distribution, homogeneity and branching of glucans can be estimated by size-exclusion chromatography (SEC), laser light scattering (LLS) and viscometry.

Lipids of adult brown shrimp,Crangon crangon: seasonal variations in fatty acids class composition

Sea food is very rich in lipids. The brown shrimp,Crangon crangonis a most popular and very valuable taxon in the White Sea, in the Mediterranean and in the Black Seas. The aim of this study was to determine the seasonal variations of lipids inC. crangonmuscle tissue using gas chromatography–mass spectrometry. The lipids were separated into groups: neutral lipids (triacylglycerols, free fatty acids, sterols) and polar lipids (phospholipids), by high performance liquid chromatography with a laser light-scattering detector. Fatty acids were identified using the GC-MS technique. The mainly fatty acids were 16:0, 18:0 (saturated FAs), 16:1, 18:1 (monounsaturated FAs), 20:4 (ARA), 20:5 (EPA) and 22:6 (DHA). The largest amounts of fatty acids in the muscle were observed in spring; these were the result of collecting food after winter and before reproduction. The muscle lipid content was 32.2 ± 1.8 mg g−1. The summer was the poorest season and the lipid value was 7.7 ±0.4 mg g−1. The levels of muscle neutral lipids (NL) oscillated between 80% (autumn) and 90% (spring). The temperature and salinity has a significant influence on content and profile of fatty acids. This work will help to understand the biology, the seasonal variation in lipid mass, lipid classes content and fatty acids profile in the abdominal muscle ofC. crangon.

Evolution of Actinyl Peroxide Clusters U28 in Dilute Electrolyte Solution: Exploring the Transition from Simple Ions to Macroionic Assemblies

Actinyl peroxide clusters, a unique class of uranyl-containing nanoclusters discovered in recent years, are crucial intermediates between the(UO2)(2+) aqua-ion monomer and bulk uranyl minerals. Herein, two actinyl polyoxometalate nanoclusters of Cs15[(Ta(O2)4)Cs4K12(UO2(O2)1.5)28]⋅20 H2O (CsKU28) and Na6K9[(Ta(O2)4)Rb4Na12(UO2(O2)1.5)28]⋅20 H2O (RbNaU28) were synthesized by incorporating a central Ta(O2)4(3-) anion that templates a hollow shell of 28 uranyl peroxide polyhedra. When dissolved in aqueous solutions with additional electrolytes, those 1.8 nm-size macroanions self-assembled into spherical, hollow, blackberry-type supramolecular structures, as was characterized by laser-light scattering (LLS) and TEM techniques. These clusters are the smallest macroions reported to date that form blackberry structures in solution, therefore, can be treated as valuable models for investigating the transition from simple ions to macroions. Kinetic studies showed an unusually long lag phase in the initial self-assembly process, which is followed by a rapid formation of the blackberry structures in solution. The small cluster size and high surface-charge density are essential in regulating the supramolecular structure formation, as was shown from the high activation energy barrier of 51.2±2 kJ mol(-1). Different countercations were introduced into the system to investigate the effect of ion binding to the length of the lag phase. The current research provides yet another scale of self-assembly of uranyl peroxide complexes in aqueous media.

Stopped-flow kinetic studies of the formation and disintegration of polyion complex micelles in aqueous solution

The formation of soluble polyion complexes (PICs) from anionic block copolymers, poly(ethylene oxide)-b-poly(sodium 4-styrene sulfonate) (PEO-b-PSSNa) and cationic block copolymers, poly(ethylene oxide)-b-poly(quaternized 2-(dimethyl amino)ethyl methacrylate) (PEO-b-PQDMA) was investigated by fluorescence spectroscopy, laser light scattering (LLS), and stopped-flow light scattering. Colloidally stabilized dispersions could be obtained upon direct mixing of the aqueous solutions of these two block copolymers, which indicated the formation of core-shell nanostructures with the core consisting of interpolymer electrostatic complexes between PSSNa and PQDMA blocks and the corona of PEO block. Both LLS and fluorescence results revealed that the most compact complex micelles formed at the equal molar ratio of oppositely charged SSNa and QDMA residues. The kinetics of the assembly process was studied via stopped-flow upon direct mixing of the two polymer solutions. The complexation process between PEO-b-PQDMA and PEO-b-PSSNa was fast and could finish within seconds. Moreover, the relaxation process can only be detected at near equal SSNa to QDMA molar ratios. The relaxation curves can be well fitted by a double-exponential function, leading to a fast relaxation process related to the initial quasi-equilibrium complex formation and a slow process related to the pre-complex structure rearrangements to the final equilibrium complexes. Both stages are determined as second-order reactions and processed through a micelle fusion-fission mechanism. Fluorescence kinetic studies revealed that the neutralization of an oppositely charged polyion was too fast to be detected and should be completed within the stopped-flow dead-time. Thermodynamic studies revealed that spontaneous complexation is entropy driven. Upon increasing the ionic strength of the solutions, the complexation processes became slower due to the decrease of entropy driving force. The PIC dissociation process was further studied and considered to consist of two competing processes: a second-order process depending on PIC concentration and a first-order process independent of the PIC concentration.

基于激光光散射层貌术的蓝宝石内部缺陷检测系统

基于激光光散射层貌术的蓝宝石内部缺陷检测系统

全方位角度分解散乱光計測による加工表面性状解析技術

全方位角度分解散乱光計測による加工表面性状解析技術

Aggregate formation in tauroursodeoxycholate solutions

The hydrodynamic radius (rH) values of simple tauroursodeoxycholate (TUDC) micelles formed between 12mM and 60mM TUDC solutions were measured using a laser light-scattering method to be nearly constant (∼15.4Å). Additionally, a kinetic dialysis technique was employed to determine the TUDC monomer concentrations with respect to the total TUDC concentrations. According to the chemical equilibrium treatment, a relationship between the TUDC monomer concentrations and the total TUDC concentrations was derived. By using a least-squares technique, the best curve-fitting to the kinetic dialysis data of the relationship predicted by the mass-action model was obtained. The equilibrium constants were also quantified. Their values together with the light-scattering results indicate that both TUDC dimers and simple TUDC micelles are formed from TUDC monomers by hydrophobic interaction. Moreover, the concentration of TUDC dimers is much higher than the concentration of simple TUDC micelles in TUDC solutions.