Poly -dextran system

The main disadvantage in using poly(acrylamide) systems is that they are not biodegradable and the monomers are toxic. Extensive purification is also required to remove the organic solvents, anionic surfactants, and residual monomers. Edman et al. [74] produced biodegradable poly(acryldextran) particles by incorporating dextran into the poly(acrylamide) chain. These particulate systems were metabolized and eliminated faster, both in vivo and in vitro, than poly(acrylamide) particles. 

Muller, W. New phase supports for liquid-liquid partition chromatography of biopolymers in aqueous poly(ethyleneglycol)-dextran systems. Synthesis and application for the fractionation of DNA restriction fragments, Eur. J. Bio-chem., 1986, 155, 213. 

The different types of cross-axis coil planet centrifuges (cross-axis CPCs) were tested for the retention of the stationary phase of aqueous-aqueous pol3fmer-phase systems such as poly(ethylene glycol) (PEG) l(X)0-potassium phosphate and PEG SOOCf iextran T500. The XL and XLL CPC are suitable for the PEG 1000-potassium phosphate, which has a relatively large difference in density between the two phases. On the other hand, the XLLL and L CPC are required to acheive satisfactory phase retention phase retention of the PEG-dextran system. These cross-axis CPCs were utilized for the separation of several proteins. 

Aqueous two-phase systems have been used as a fast and effective process for separation of biomolecules (Gupta et al, 1999). The two-phase polymer systems are commonly formed by using two incompatible polymer/poly-mer or polymer/salt systems. Poly(ethylene) glycol-dextran systems are commonly used in two-phase separation. Partitioning is a complex process and depends on the surface properties of the proteins. Depending on its hydrophilic/hydrophobic properties the target product concentrates in one of the phases, while the impurities remain in another phase and can be easily removed. The recovery of the protein from the phase-forming polymer is the main bottleneck of the purification process. 

Two-phase aqueous systems with SPs were introduced as an alternative to poly(ethylene) glycol and dextran systems (Persson et /., 2000). SPs could easily be recovered after separation owing to the reversible phase transition... 

In one of the earliest studies [39], we carried out the purification of A5 4 3-oxosteroid isomerase from a crude extract of Pseudomonas testosteroni by affinity pardoning in a poly(ethylene glycol)/dextran system. The macroligand was prepared by covalent coupling on poly(ethylene glycol) (PEG) of the same steroid derivative as previously described in Fig. 14.2. The resulting macroligand PEG-E,i had an inhibition constant Ki around 5 pM towards the isomerization of A5-androstene-3,17-dione, by isomerase. 

Two-Phase Aqueous Extraction. Liquid—Hquid extraction usually involves an aqueous phase and an organic phase, but systems having two or more aqueous phases can also be formed from solutions of mutually incompatible polymers such as poly(ethylene glycol) (PEG) or dextran. A system having as many as 18 aqueous phases in equiHbrium has been demonstrated (93). Two-phase aqueous extraction, particularly useful in purifying biological species such as proteins (qv) and enzymes, can also be carried out in combination with fermentation (qv) so that the fermentation product is extracted as it is formed (94). 

Microspheres and nanoparticles often consist of biocompatible polymers and belong either to the soluble or the particle type carriers. Besides the aforementioned HPMA polymeric backbone, carriers have also been prepared using dextrans, ficoll, sepharose or poly-L-lysine as the main carrier body. More recently alginate nanoparticles have been described for the targeting of antisense oligonucleotides [28]. As with other polymeric carrier systems, the backbone can be modified with e.g. sugar molecules or antibody fragments to introduce cellular specificity. 

Amphiphilic poly(ethylene glycol)-alkyl dextran ethers are emerging as vehicles in the oral delivery of poorly water soluble drugs [251,268,269]. They form polymer micelles of low critical association concentrations (CAC) and small micelle sizes in aqueous solution. Particulate delivery systems lead to an enhancement of the absorption efficiency and bioavailability of highly hpophihc drugs orally applied, and provide the drug with some level of pro-... 

As an example of a correlation of ternary LLE data, the system water-dextran (Mn = 23,000)-poly(ethylene glycol) (Mw = 6,750) at 273 K (Albertsson, 1986) was correlated... 

Poly(amino acid)s (PAAs) have also been used in drug delivery PEO-(l-aspartic acid) block copolymer nano-associates , formed by dialysis from a dimethyl acetamide solution against water, could be loaded with vasopressin. PLA-(L-lysine) block copolymer microcapsules loaded with fluorescently labelled (FITC) dextran showed release profiles dependent on amino acid content. In a nice study, poly(glutamate(OMe)-sarcosine) block copolymer particles were surface-grafted with poly(A-isopropyl acrylamide) (PNIPAAm) to produce a thermally responsive delivery system FITC-dextran release was faster below the lower critical solution temperature (LCST) than above it. PAAs are prepared by ring-opening polymerisation of A-carboxyanhydride amino acid derivatives, as shown in Scheme 1. 

A recent study has explored the potential of the ternary complex formed between a poly(p-cyclodextrin) (formed by polycondensation of p-cyclodextrin), a cationic surfactant (dodecyltrimethylammonium chloride), and a polyanion in water, to act as a delivery system for gene therapy,using a combination of viscometric and SANS studies as well as visual observations to determine the macroscopic and microscopic properties of the complexes. In the study, sodium dextran sulfate was used as a substitute for DNA. The potential advantages of the use of such ternary complexes over the more commonly investigated DNA-lipid or polymer complexes (lipoplexes and poly-plexes, respectively) include a high water solubility of the resulting complex (lipoplexes and polyplexes often... 

Passirani, C. Barratt, G. Devissaguet, J.P. Labarre, D. Interactions of nanoparticles bearing heparin or dextran covalently bound to poly(methylmethacrylate) with the complement system. Life Sci. 1998, 62, 775-785. 

Many ATPS systems contain a polymer which is sugar based and a second one which is of hydrocarbon ether type. Sugar-based polymers include dextran (Dx), hydroxy propyl dextran (HPDx), FicoU (Fi) (a polysaccharide), methyl cellulose (MC), or ethylhydroxyethyl cellulose (EHEC). Hydrocarbon ether-type polymers include poly (ethylene glycol) (PEG), poly (propylene glycol) (PPG), or the copolymer of PEG and PPG. De-rivatized polymers can also be useful, such as PEG-fatty acids or di-ethylaminoethyl-dextran (Dx-DEAE). 

Conventional SEC is the classical method for measuring the MMD of synthetic or natural polymers. Conventional SEC essentially means the use of an on-line single concentration detector - differential refractometer (DRI) or UV. In such SEC systems, the molar mass is calculated by means of a direct or universal calibration applying a set of appropriate narrow and/or broad MMD standards. Unfortunately, classical narrow MMD standards for aqueous SEC mobile phases such as pullulan, poly(ethylene oxide), poly (ethylene glycole), and dextran are not suitable for characterization of HA. The listed SEC standards are neutral molecules existing in solution as flexible random coils, and some of... 

Fig. 17 Electropherograms obtained from different ANDS-dextran derivatives in the described separation system. Samples case A dextran 1,080 (c=l g L 1), the numbers represent the degree of oligomerization case B dextran 21,400 (c=10 g L ) case C dextran 401,000 (c=20 g L ). Separation conditions fused-silica capillary 88/100 cm, i.d. 50 pm BGE 0.05 mol L 1 phosphate pH 6.0+2% wlw poly(vinylsulfate) U=+25 kV injection for 24 s at 200 mbar detection EX 259 nm, EM 442 nm...

Huddleston, J.G. and Rogers, R.D. (2005) Solvent property characterization of poly(ethylene glycol) / dextran aqueous biphasic systems using the free energy of transfer of a methylene group and a linear solvation energy relationship. Ind. Eng. Chem. Res., 44, 3749-3760. 

Systems with two aqueous phases have been used in the separation of proteins and metal ions.46 These involve water-soluble polymers, such as poly (ethylene glycol), with or without salts, such as potassium phosphate.47 Such systems eliminate the need for volatile organic solvents. A typical example is the separation of myoglobin with aqueous poly(/V-vinylacetamide)-dextran, the protein going to the bottom phase containing the dextran.48... 

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