Physicochemical characterization

The aim of this chapter is to summarize some of the research findings on xylan, a natural polymer extracted from corn cobs, which presents a promising application in the development of colon-specific drug carriers. Physicochemical characterization of the polymer regarding particle size and morphology, composition, rheology, thermal behavior, and crystallinity will be provided. Additionally, research data on its extraction and the development of microparticles based on xylan and prepared by different methods will also be presented and discussed. 

Comprehensive physicochemical characterization of any raw material is a crucial and multi-phased requirement for the selection and validation of that matter as a constituent of a product or part of the product development process (Morris et al., 1998). Such demand is especially important in the pharmaceutical industry because of the presence of several compounds assembled in a formulation, such as active substances and excipients, which highlights the importance of compatibility among them. Besides, variations in raw materials due to different sources, periods of extraction and various environmental factors may lead to failures in production and/or in the dosage form performance (Morris et al., 1998). Additionally, economic issues are also related to the need for investigating the physicochemical characteristics of raw materials since those features may determine the most adequate and low-cost material for specific procedures and dosage forms. 

Few, if any, minor signals are in evidence for which the signal-to-noise ratio is good and which can be assigned to known chemical entities that are available in quantities sufficiently large to allow for a complete physicochemical characterization. 

In recent decades, many investigations have been carried out on the solubilization and on the physicochemical characterization of a wide variety of substances confined in water-containing reversed micelles. Even if these studies have not produced a general theory to predict a priori all the effects accompanying the solubihzation process, some general aspects nonetheless have been underhned. In the following, the results of some of these investigations, selected to show the extent of some peculiar behaviors, will be reported. 

The crystallization step is generally studied quite exhaustively at the laboratory scale and often at the pilot scale. The reaction chemistry should be properly understood to access effects, if any, of the synthesis step on the impurity profile. In batch cooling crystallizers attempts have been made to create optimum conditions by on-line turbidity analysis (Moscosa-Santillan et al., 2000). Physicochemical characterization of the products should be done rigorously (Tanguy and Marchal, 1996). 

Buszewski, B., Gadza-la-Kopciuch, R. M., Markuszewski, M. L, Kaliszan, R. Chemically bonded silica stationary phases synthesis, physicochemical characterization, and molecular mechanism of reversed-phase HPLC retention. Anal. Chem. 1997, 69, 3277-3284. 

K Westesen, T Wehler. Physicochemical characterization of a model intravenous oil-in-water emulsion. J Pharm Sci 81(8) 777-786, 1992. 

The cyclotrisilazane (R = Me) produced in reaction (14) is recycled at 650°C [by reaction with MeNHo) the reverse of reaction (14)] to increase the yield of processible polymer. Physicochemical characterization of this material shows it to have a softening point at 190°C and a C Si ratio of 1 1.18. Filaments 5-18 pm in diameter can be spun at 315°C. The precursor fiber is then rendered infusible by exposure to air and transformed into a ceramic fiber by heating to 1200°C under N2- The ceramic yield is on the order of 54% although, the composition of the resulting amorphous product is not reported. The approach used by Verbeek is quite similar to that employed by Yajima et al. (13) in the pyrolytic preparation of polycarbosilane and its transformation into SiC fibers. 

Magnetic iron oxide nanoparticles synthesis, stabilization, vectorization, physicochemical characterizations, and biological applications. Chemical Reviews, 108 (6), 2064-2110. 

Badley, J.E., Grieve, R.B., Bowman, D.D., Glickman, L.T. and Rockey,J.H. (1987) Analysis of Toxocara canis larval excretory-secretory antigens physicochemical characterization and antibody recognition. Journal of Parasitology 73, 593-600. 

Ramirez-Corredores, M. M. Mujica, E., and Salazar, J. A., Physicochemical characterization of VGO MHCK catalysts and its extrapolation to catalytic activity. Stud. Surf. Scien. Catal, 1999. 127 pp. 279-86. 

Halloysite was found to be a viable and inexpensive nanoscale container for the encapsulation of biologically active molecules and drugs as was first demonstrated by Price et al. [5-8]. Its physicochemical characterization as a novel drug delivery system was also reported by Levis and Deasy et al. [9,10], who further demonstrated the controlled release of diltiazem hydrochloride and propanol hydrochloride... 

Lutolf MP, Hubbell JA (2003) Synthesis and physicochemical characterization of end-linked poly(ethylene glycol)-co-peptide hydrogels formed by michael-type addition. Biomacromolecules 4 713-722... 

A synthesis and physicochemical characterization, including molecular second-order nonlinear optical properties, of new push-pull-based chromophores 170 properly functionalized for polymerization and containing oxadiazole rings were reported <2002J(P2)1791>. 

The physicochemical characterization of a colloidal carrier is necessary because important characteristics, such as particle size, hydrophobicity, and surface charge, determine the biodistribution after administration [129-132]. Preparation conditions, such as the pH of the polymerization medium, monomer concentration, and surfactant concentration, can influence the physicochemical characteristics of the particles [60, 62, 64]. It is, therefore, essential to perform a comprehensive physicochemical characterization of nanoparticles, which has been reviewed by Magenheim and Benita [133]. 

Sonvico F, Mornet S, Vasseur S, Dubernet C, Jaillard D, Degrouard J, Hoebeke J, Duguet E, Colombo P, Couvreur P (2005) Folate-conjugated iron oxide nanoparticles for solid tumor targeting as potential specific magnetic hyperthermia mediators synthesis, physicochemical characterization, and in vitro experiments. Bioconjugate Chemistry 16 1181-1188. 

In M14 = Mi4 compounds (M, M = Si, Ge, Sn), only >Si = Sn< derivatives have not yet been physicochemically characterized (a transient compound of this type has been postulated by Lappert et al. as possible intermediate in the reaction between a silylene and a stannylene leading to a silylstannylene118). 

Patani GA, Pang YP, Chien YW (2005) A potent and selective tacrine analog-biomembrane permeation and physicochemical characterization. Pharm Dev Tech-nol 10 525-538. 

Two common threads will connect the various aspects considered in this chapter the pivotal yet double-edged role of water for the operation of PEFCs and the hierarchy of scales that has to be considered in theoretical modeling, physicochemical characterization, and materials design, as illustrated in Figure 6.2. ... 

Jurgens G, Muller M, Koch MH, et al. Interaction of hemoglobin with enterobacterial lipopolysaccharide and lipid A. Physicochemical characterization and biological activity. Eur J Biochem 2001 268 4233. 

B., and Hunger, M. (1992) Mordenite acidity dependence on the silicon/ aluminum ratio and the framework aluminum topology. 1. Sample preparation and physicochemical characterization. /. Phys. Chem., 96 (21), 8473-8479. 

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