Universal Behavior of Fractal Water Structures Observed in Various Gelation Mechanisms of Polymer Gels, Supramolecular Gels, and Cement Gels.

So far, it has been difficult to directly compare diverse characteristic gelation mechanisms over different length and time scales. This paper presents a universal water structure analysis of several gels with different structures and gelation mechanisms including polymer gels, supramolecular gels composed of surfactant micelles, and cement gels. The spatial distribution of water molecules was analyzed at molecular level from a diagram of the relaxation times and their distribution parameters (τ-ß diagrams) with our database of the 10 GHz process for a variety of aqueous systems. Polymer gels with volume phase transition showed a small decrease in the fractal dimension of the hydrogen bond network (HBN) with gelation. In supramolecular gels with rod micelle precursor with amphipathic molecules, both the elongation of the micelles and their cross-linking caused a reduction in the fractal dimension. Such a reduction was also found in cement gels. These results suggest that the HBN inevitably breaks at each length scale with relative increase in steric hindrance due to cross-linking, resulting in the fragmentation of collective structures of water molecules. The universal analysis using τ-ß diagrams presented here has broad applicability as a method to characterize diverse gel structures and evaluate gelation processes.

Anesthetic Molecule Interaction of Noble Gases with Proteins and Lipids and their Effect: A Review.

Surgical operations are impossible without administering proper analgesia. Advancement in the field of anesthesia has invariably resulted in the accomplishment of all surgical processes without any inconvenience. Admittedly, the use of noble gas is on the decline. The noble gases may not interact chemically with any other substance under normal temperature and pressure but they may interact with proteins and lipids. Different anesthetic molecules may stimulate either proteins or lipids in membrane. There is a connection between the anesthetic molecules and the hydrophobic region of the membrane. In the present review, we attempt to highlight the interaction between the anesthetic molecule with proteins and lipids and their effects. We sketched few noble gases and some other existing molecules such as halothane and alcohol which interacted with proteins and lipids.

Recent trends of polymer mediated liposomal gene delivery system.

Advancement in the gene delivery system have resulted in clinical successes in gene therapy for patients with several genetic diseases, such as immunodeficiency diseases, X-linked adrenoleukodystrophy (X-ALD) blindness, thalassemia, and many more. Among various delivery systems, liposomal mediated gene delivery route is offering great promises for gene therapy. This review is an attempt to depict a portrait about the polymer based liposomal gene delivery systems and their future applications. Herein, we have discussed in detail the characteristics of liposome, importance of polymer for liposome formulation, gene delivery, and future direction of liposome based gene delivery as a whole.

Next generation delivery system for proteins and genes of therapeutic purpose: why and how?

Proteins and genes of therapeutic interests in conjunction with different delivery systems are growing towards new heights. "Next generation delivery systems" may provide more efficient platform for delivery of proteins and genes. In the present review, snapshots about the benefits of proteins or gene therapy, general procedures for therapeutic protein or gene delivery system, and different next generation delivery system such as liposome, PEGylation, HESylation, and nanoparticle based delivery have been depicted with their detailed explanation.

Effect of salt content on the rheological properties of hydrogel based on oligomeric electrolyte.

Dynamic light scattering and oscillatory rheology experiments were performed to study the effects of various salts on the hydrogel consisting of an oligomeric electrolyte gelator, poly(pyridinium-1,4-diyliminocarbonyl-1,4-phenylenemethylene chloride) (1-Cl). Sol-gel transition temperature increased with increasing salt concentration that suggested the salt-in behavior. The concentration dependence of the dynamic shear moduli showed power-law scaling behavior and was compared with the predictions made by the fractal gel model. The brittleness was increased by increasing salt concentration, indicating that 1-Cl hydrogel became better packed into stronger networks in ionic solutions. After certain salt concentrations, 1-Cl hydrogel started precipitation that might be due to the excessive network formation resulting in collapse of the network structure. The recovery of the mechanical properties of 1-Cl hydrogel was completely reduced in the presence of salts.

Phase transition and abnormal behavior of a nematic liquid crystal in benzene.

Differential scanning calorimetry and broadband dielectric spectroscopy measurements were performed to investigate the phase transitions in nematic liquid crystal (LC)/benzene mixtures. Noticeable changes of the crystal-isotropic phase transition and the phase transition enthalpy were observed. We also estimated the number of unfreezable benzene molecules from the LC/benzene mixtures. The crystal-isotropic phase transition temperature was described very accurately from the temperature-dependent relaxation strength, the relaxation time, and the symmetric shape parameter obtained from the fitting procedure. Surprisingly, the abnormal behavior of the isotropic phase was observed in LC/benzene mixtures that suggested the presence of local structure in the mixture, which set off the dipole moments along the long axis. The interaction between the LC molecules was also discussed from the tau-beta diagram.

Microwave dielectric study of an oligomeric electrolyte gelator by time domain reflectometry.

The dynamics of water molecules in aqueous solutions of an oligomeric electrolyte gelator, poly[pyridinium-1,4-diyliminocarbonyl-1,4-phenylene-methylene chloride] (1-Cl) was characterized by microwave dielectric measurements using the time domain reflectometry method. The dielectric dispersion and absorption curves related to the orientational motion of water molecules were described by the Cole-Cole equation. Discontinuities were observed in the concentration dependence of the dielectric relaxation strength, Deltaepsilonh, as well as in the Cole-Cole parameter, betah. These discontinuities were observed between the samples with concentrations of 6 and 7 g/L 1-Cl/water, which correspond to a change in the transparency. Such a discontinuity corresponds to the observation of the critical concentration of gelation. The interaction between water and 1-Cl molecules was discussed from the tauh-betah diagram. As 1-Cl carries an amide group, it could be expected that 1-Cl may interact hydrophilically with water, but the present result suggests that 1-Cl interact hydrophobically with water.

Broadband dielectric spectroscopy of a nematic liquid crystal in benzene.

Broadband dielectric spectroscopy has been used to analyze the temperature, frequency, and concentration dependences of the molecular dynamics of a nematic liquid crystal (5CB) mixed with the nonpolar solvent benzene. Differential scanning calorimetry measurement has been also performed to confirm the phase transitions of 5CB/benzene mixtures. The phase transition temperatures (crystalline to isotropic phases) thus obtained have been described very accurately from the temperature-dependent relaxation strength, the relaxation time, and the symmetric shape parameter of the relaxation function obtained from the fitting procedure. Two relaxation processes reflecting overall rotations around the short and long molecular axes are observed in both the nematic and isotropic phases. In the crystalline phase, the former process with the longer relaxation time disappeared, and latter process with shorter relaxation time shows a discontinuity at the freezing temperature. The relaxation process with shorter relaxation time obtained in the crystalline phase is larger than that obtained in the nematic phase because of the large restrictions in the crystalline phase. For the first time, we have precisely explained the molecular mechanism and structure of liquid crystalline materials as a function of concentration, temperature, and frequency.

Structural characterization of ionic gelator studied by dynamic light scattering and small-angle neutron scattering.

Structural characterization of a hydrogel consisting of an oligomeric electrolyte, poly[pyridinium-1,4-diyliminocarbonyl-1,4-phenylenemethylene chloride] (1-Cl) as an ionic gelator was carried out by static and dynamic light scattering (SLS/DLS) and small-angle neutron scattering (SANS) techniques. All the measurements were performed by changing the concentration and temperature. We have successfully obtained the weight average molecular weight and the degree of polymerization of poly(1-Cl) by SLS. The sol-gel transition was clearly observed as large fluctuations in the scattering intensity of the time-intensity correlation function. Time correlation function of the scattering light intensity entailed a power law behavior at the sol-gel transition. 1-Cl hydrogel showed strong hysteresis and its hysteresis loop was observed both by DLS and theological methods. We have estimated the critical concentration of gelation and the gelation temperature by DLS. The enthalpy change for gelation was estimated to be ca. -10 kJ/mol. SANS experiments revealed that the unit structure of the gel network is responsible for the gelation of 1-Cl hydrogel.

Rheological study on rapid recovery of hydrogel based on oligomeric electrolyte.

The hydrogel consisting of an oligomeric electrolyte, poly[pyridinium-1,4-diyl-iminocarbonyl-1,4-phenylenemethylene chloride] (1-Cl) underwent self-healing at temperatures lower than its gelation temperature after destruction of the gel network in a shear flow. The self-healing mechanism was investigated by rheological measurements on three different kinds of gels including a low-molecular weight organogelator and a polymeric hydrogelator. Although all of the three gels exhibited thermo-reversible hysteresis loops in the shear moduli, only 1-Cl hydrogel recovered its mechanical properties after vigorous agitation. It is conjectured that the self-healing is due to formation of network structure via a chlorine ion mediated hydrogen bond for which the activation energy is on the order of 10 kJ/mol.