PubMed In order to address this concern, a novel class of biomaterials based upon a cyclic acetal unit has been developed. 24(4):571–577 (2003). These compounds are obtained from the dichlorosilanes or the ditriflates.215 An example for the use of the di-t-butylsilylene group is given in Scheme 55. Swelling degree increased as the PECA concentration decreased, due to the mobility of the polymer chains during gelation and the crosslink density of hydrogels. Alternatively, water swellable EH-PEG hydrogels were able to sustain an encapsulated osteoprogenitor cell population for up to 7 days in vitro as well as deliver BMP-2 to bone in vivo. Its removal is accomplished with tri- or tetra-n-butylammonium fluoride, 0.2 M HCl/MeOH and 0.2 M NaOH in dioxane/water. Biomaterials. volume 25, pages2348–2356(2008)Cite this article. Molecules. Reaction of di(ethylene glycol) vinyl ether with phenyl triflate in presence of a catalytic amount of palladium acetate and 1,3-bis(diphenylphosphino)propane (DPPP), as a ligand, provides a direct route to cyclic ketal of acetophenone 91 (Scheme 21). For example, the common sugar glucose exists in the cylcic manner more than 99% of the time in a mixture of aqueous solution. Actually, as might be expected from the general difficulty of cyclizations which give eight-membered rings (cf. They are also sensitive to strong Lewis acids [e.g., aluminum chloride (AlCl3) and mercuric salts]. S. Kaihara, et al. Mater. After careful evaluation of oxidants, we identified iodobenzene diacetate as the best oxidant to induce the formation of the spiro product 15. While polyesters and polyanhydrides are all widely characterized and under development for biomedical applications, they are not biologically inert and may non-specifically react with the surrounding in vivo environment (53). Thus, the addition of PEGDA strongly influenced the hydrophilicity of the material, due to its hydrophilic EH polymer main chain (58). The mechanism for converting a cyclic ketone to a cyclic acetal. (b) Step 1. Mater. 17 These examples demonstrate the importance of cyclic acetals in organic synthesis. have also used these polyacetal and polyketal based dendrimer structures to create potential drug carriers (72). Pharmacol. T. W. Gilbert, A. M. Stewart-Akers, and S. F. Badylak. John P. Fisher. Carbonyl compounds which have been used include acetaldehyde (or its equivalent), dichloroacetaldehyde and isobutyraldehyde. The results demonstrated that the degradation of the EH networks was not associated with a significant pH change over the course of the 28 day study (Fig. Synthetic route for PECA and PECA hydrogels (60). A. Braz. 2,2-Dimethyl-1,3-dioxocanes have been prepared from 2,2-dimethoxypropane rather than from acetone. N. G. Lemcoff, and B. Fuchs. However, the EHD monomer may be easily synthesized in approximately 4 days (60). Results also confirmed the near constant solvent pH throughout the 28 days degradation study, demonstrating the lack of acidic degradation products produced by CABs. Adhesion of cultured human endothelial cells onto methacrylate polymers with varying surface wettability and charge. Adv. Am. Polyanhydrides are especially desirable due to their surface erosion degradation properties (26,48,49). The goals of the study were to repair the defect while studying tissue response to EH-PEG hydrogels and the extent of bone repair after loading the hydrogels with bone morphogenetic protein-2 (BMP-2). 2b). A. Stenzl, and K. D. Sievert. Step 3. To this end, the copolymer poly[poly(ethylene glycol)-co-cyclic acetal] (PECA) and the resulting PECA hydrogels have been developed. 12(10–12):883–887 (2001). Bioconjug. If your intended use exceeds what is permitted by the license or if Hydrolyze the THP derivative with dilute acid. 7(7):2237–2242 (2006). 5(2):151–157 (1994). HDP is then reacted with trimethylolpropane in 1 M hydrochloric acid. They are more readily cleaved by acids than the acetonides. Res. X. Shi, et al. Reduce the ester with lithium aluminum hydride to give the primary alcohol. Degradation and biocompatibility of a poly(propylene fumarate)-based/alumoxane nanocomposite for bone tissue engineering. PGA degrades via bulk degradation, where mass loss occurs throughout the material while initial dimensions (or volume) of the material remains mostly constant (27). Biomaterials. Effect of physiological temperature on the mechanical properties and network structure of biodegradable poly(propylene fumarate)-based networks. Google Scholar. 19(5):458–467 (1995). Toxicity, biodegradation and elimination of polyanhydrides. More specifically, EHD is first dissolved in tetrahydrofuran with sodium hydride at 0°C.
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