Self-assembling polysaccharide nanostructures have moved to the forefront of many fields due to their wide range of functional properties and unique advantages, including biocompatability and stimulus responsiveness. In particular, the field of controlled release, which involves influencing the location, concentration, and efficacy of active pharmaceutical ingredients (APIs), diagnostics, nutrients, or other bioactive compounds, has benefited from polysaccharide biomaterials. Nanostructure formation, stimulus responsiveness, and controlledrelease performance can be engineered through facile chemical functionalization and noncovalent intermolecular interactions. This review discusses polysaccharide nanoparticles, designed for targeted and time-controlled delivery of emerging APIs, with improved in vivo retention, stability, solubility, and permeability characteristics. Topics covered include nanoparticles of cyclodextrin and cyclodextrin-containing polymers, hydrophobically modified polysaccharides, polysaccharide nanoparticles that respond to pH, temperature, or light stimulus, polysaccharide prodrug complexes, polysaccharide complexes with lipids and proteins, and other polysaccharide polyelectrolyte complexes.
Dual-responsive polysaccharide microgel dispersions were synthesized by the self-assembly of a temperature-responsive water-soluble cellulose ether, hydroxypropyl cellulose (HPC), and a pH-responsive polymer, sodium alginate (NaAlg). Spontaneous temperature-induced aggregation of aqueous HPC at a temperature above the lower critical solution temperature (LCST) of the polymer, in the presence of a surfactant (soy lecithin), resulted in microparticles that could be covalently cross-linked with trisodium trimetaphosphate (TSTMP). The microgel particles were saturated with a model carbohydrate, D-glucose (dextrose), and covered by a layer of alginic acid nanoparticles to obtain a controlledrelease platform for sustained oral delivery of nutrients to athletes for improving their endurance capacity and exercise performance. Diffusion-cell studies of the in vitro release kinetics showed that the microgel dispersion released the absorbed glucose at a slower rate at pH 2, corresponding to the pH of gastric fluid, than at pH 7, corresponding to the pH of intestinal fluid. Furthermore, the rate of release of glucose from the microparticles was faster at a temperature above the LCST of the polymer particles. The LCSTs of the aqueous microgel dispersions were determined using rheology and calorimetric measurements and found to be strongly affected by the presence of kosmotropic solutes. Measurements of in vivo release kinetics in human subjects demonstrated that the temperature-and pHresponsive microgel dispersions were able to sustain higher concentrations of glucose in the blood plasma for a longer time, compared with conventional sugar solutions used as controls.
Many scientists use quantitative measurements to compare the presence and amount, of various proteins and nucleotides among series of one- and two-dimensional (1-D and 2-D) electrophoretic gels. These gels are often scanned into digital image files. Gel spots are then quantified using stand-alone analysis software. However, as more research collaborations take place over the Internet, it has become useful to share intermediate quantitative data between researchers. This allows research group members to investigate their data and share their work in progress. We developed a World Wide Web group-accessible software system, WebGel, for interactively exploring qualitative and quantitative differences between electrophoretic gels. Such Internet databases are useful for publishing quantitative data and allow other researchers to explore the data with respect to their own research. Because intermediate results of one user may be shared with their collaborators using WebGel, this form of active data-sharing constitutes a groupware method for enhancing collaborative research. Quantitative and image gel data from a stand-alone gel image processing system are copied to a database accessible on the WebGel Web server. These data are then available for analysis by the WebGel database program residing on that server. Visualization is critical for better understanding of the data. WebGel helps organize labeled gel images into montages of corresponding spots as seen in these different gels. Various views of multiple gel images, including sets of spots, normalization spots, labeled spots, segmented gels, etc. may also be displayed. These displays are active and may be used for performing database operations directly on individual protein spots by simply clicking on them. Corresponding regions between sets of gels may be visually analyzed using Flicker-comparison (Electrophoresis 1997, 18, 122-140) as one of the WebGel methods for qualitative analysis. Quantitative exploratory data analysis can be performed by comparing protein concentration values between corresponding spots for multiple samples run in separate gels. These data are then used to generate reports on statistical differences between sets of gels (e.g., between different disease states such as benign or metastatic cancers, etc.). Using combined visual and quantitative methods, WebGel can help bridge the analysis of dissimilar gels which are difficult to analyze with stand-alone systems and can serve as a collaborative Internet tool in a groupware setting.
Tetradentate Janus heads L−: Staples for the construction of square tetranuclear clusters of the type [M4L8] 1 (M=Ni, Zn; see picture). The [2×2] grids 1 are generated in a one‐pot reaction by self‐assembly. The magnetic susceptibility of the nickel complex [Ni4L8] Ni‐1 exhibits an increase of χT at low temperature due to intramolecular ferromagnetic coupling of the Ni ions.
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