Polymer-based systems

SchaffertD, Wagner E (2008) Gene therapy progress and prospects synthetic polymer-based systems. Gene Ther 15 1131-1138... 

Due to the short transit time of materials taken orally, large PLGA matrices cannot deliver their entire contents prior to being eliminated. For this reason, microparticles have been the dosage form of choice for not only PLGAs, but also the majority of the hydrophobic polymer based systems. Microparticles of PLGA deliver their contents over a period from hours to years, depending on their composition... 

Material 3 has been found to serve as a highly effective and clean catalyst for the oxidation of primary alcohols to aldehydes with a superior performance over that of the previously reported polymer based system (PSP). The oxidations, using our previously published protocol, produced the corresponding aldehydes in less than three hours using a 10 wt% of solid catalyst,22 significantly, the aldehydes were free of contaminants. 

Polymer-based systems. Pulsatile release of medicaments can be obtained from polymer-based delivery systems. Based on the mechanism of drug release from the polymer, these systems can be divided into various classes and subclasses. Broadly, they can be classified into three classes delivery by hydrolysis of polymers, delivery by osmotic pressure, and delivery by both hydrolytic degradation and osmotic effects. 

Here we will exclusively discuss polymer-based systems in which the switching unit itself is chiral.[70 ... 

Both aqueous polymer-based systems (latex), made by emulsion or dispersion polymerization, and oil-modified alkyd resin-based systems are still in wide use [781], Table 12.2 shows the composition of a typical water-based emulsion paint. There is a wide variety of coatings, ranging from broad applicability to highly specialized, including latexes, amino resins, isocyanates, epoxy resins, acrylic resins, polyester... 

The use of multiscale modeling for polymers and polymer-based systems can be distinguished into synthetic (man-made) and biological (God-made) materials. Although synthetic polymers have been used as monolithic structural materials,... 

The design of a polymer-based system requires understanding both the steady state and transient behavior in response to the substrate or analyte of interest. For sensor applications, this information is obtained during the operation of the sensor. However, for other applications of environmentally sensitive polymers, such as drag delivery systems, the polymer response to the substrate/analyte is not usually studied directly. Our work with the pAAm/GO/PR system illustrates the usefulness of an in situ probe to measure what governs the membrane s performance in response to the substrate/analyte and how to analyze it. We continue to use this valuable information in the further... 

Other nonaqueous systems, which were mentioned in the first chapter, such as ionically conducting polymers, molten salts and solid electrolytes, have uses that are more specific. Hence, experimental aspects that are related to polymer based systems and molten salts are mentioned in the chapters that deal with them. 

One can distinguish between real more-component polymeric systems (Class A), which do not contain anything else than polymeric materials, and polymer-based systems (Class B) in which isotropic polymeric materials are present together with either non-polymeric components or with already preformed oriented polymeric components (fibres or filaments)... 

Polymer-based systems offer numerous advantages, such as biocompatibility, biodegradability, and ability to incorporate functional groups for attachment of drugs. Drugs can be incorporated into the polymer matrix or in the cavity created by the polymeric architecture, from which the drug molecule can be released with an element of temporal control, and controlled pharmacokinetic profile with almost zero-order release achievable. 

The photoreduction of aromatic ketones by tertiary amines is reported [38] to proceed at rates which are substantially faster than those observed for the corresponding photoinduced hydrogen abstraction from, e.g. alcohols. A limit case is given by fluorenone, the photoreduction of which does not occur in alcohol, ether or alkane solution, but readily takes place in the presence of amines, tertiary amines being the most effective [39,40]. Xanthone has also been reported to be easily photoreduced by iV,A-dimethylaniline [41], but not by 2-propanol [42]. However, the oxidation of tertiary amines photosensitized by fluorenone and xanthone is much less efficient than when sensitized by benzophenone, apparently because of lower rates of hydrogen abstraction [43]. Fluorenone/tertiary amine systems have been used successfully to photoinitiate the polymerization of MMA, St, MA and AN [30,38,44] and rather similar results have been obtained in the photoinitiated polymerization of MA by the benzophenone/EtsN system [45]. Thus, the great variety of substrates participating in exciplex formation has been readily extended to polymer-based systems. 

The large variety of molecular structures capable of undergoing photoffag-mentation processes has readily been extended to polymer-based systems. 

Reis, Rui L., Daniel Cohn, and North Atlantic Treaty Organization Scientific Affairs Division. Polymer Based Systems on Tissue Engineering, Replacement and Regeneration. Vol. 86 of Mathematics, Physics, and Chemistry. NATO Science Series, ser. II. Boston Kluwer Academic Publishers, 2002. 

One practical approach to double staining with monoclonal antibodies is given in Appendix lA, but polymer-based systems are widely available today and generally simpler to perform. 

Haupt, K., Mayes, A.G., and Mosbach, K. (1998) Herbicide assay using an imprinted polymer based system analogous to competitive fluoroimmunoassays. Analytical Chem istry, 70, 3936 3989. 

Azobenzene-containing materials can be classified into two groups polymer-based systems and molecular glasses. Azobenzene chromophore units, which are the optically addressable moiety, can be incorporated into polymer systems in several ways, as is schematically illustrated in Fig. 3. 

R.L. Reis, D. Cohn, Polymer based systems on tissue engineering, replacement and regeneration, Kluwer Academic Publishers, Dordrecht, The Netherlands, 2002. 

The development of transparent conductive electrodes based on SWNT thin films represented an outstanding scientific breakthrough for applications in the area of optoelectronics. However, to build integrated CNT-polymer-based systems it is necessary to engineer the interfaces between the two constituents through organized nanotube architectures. 

On a molecular scale all of these polymer-based systems consist of two phases a continuous, polymer network and a continuous solvent network. I consider them heterogeneous on a molecular scale because the dielectric constant in the solvent phase varies locally. I was one of the first to argue (in 1966) that the socalled homogeneous gel model of ion exchange resins was not possible. The dielectric constant in the vicinity of a sulfonate group cannot be the same as it is in the vicinity of a hydrocarbon (or fluorocarbon) backbone. 

Extracellular barriers in systemic delivery involve hurdles to nucleic acid delivery encountered from the point of injection to the surface of the cellular target. For cationic polymer-based systems, these barriers typically include the toxicity of the nanoparticles, interactions with semm proteins, extracellular matrices, and nonspecific cell surfaces, clearance by the innate immune system, aggregation due to physiological salt conditions, and evasion of the adaptive immune response. Ideally, the nanoparticle should (1) remain nontoxic, small, and dis-aete, (2) bypass the immune system, and (3) interact only with the cells of interest. Efforts to prepare polymer systems that endow nanoparticles with these characteristics are discussed below. 

---