Suzuki-Miyaura cross-coupling of arenediazonium salts catalyzed by alginate/gellan-stabilized palladium nanoparticles under aerobic conditions in water
The use of palladium nanoparticles stabilized by natural. beads made of an alginate/gellan mixture in the Suzuki-Miyaura cross-coupling reaction of arenediazonium. tetrafluoroborates with potassium aryltrifluoroborates. (1 : 1 molar ratio) with loading as low as 0.01–0.002. mol% under aerobic, phosphine-, and base-free conditions. in water is described. The catalyst system can be reused. several times without significant loss of activity.
Photocrosslinking of dextran and polyaspartamide derivatives: a combination suitable for colon-specific drug delivery.
Abstract The aim of this study was to prepare and characterize novel hydrogels with polysaccharide–polyaminoacid structure, able to undergo an enzymatic hydrolysis in the colon and potentially useful for treating inflammatory bowel diseases (IBD). Starting materials were methacrylated dextran (DEX-MA) and methacrylated α,β-poly(N-2-hydroxyethyl)- dl -aspartamide (PHM). These polymers were photocrosslinked by exposure of their aqueous solutions at 313 nm without photoinitiators. Different samples, shaped as microparticles, were obtained as a function of polymer concentration and irradiation time. FT-IR analysis confirmed the occurrence of a co-crosslinking between DEX-MA and PHM in all exper…
Biodegradable and pH-sensitive hydrogels for potential colon-specific drug delivery: Characterization and in vitro release studies
A novel pH-sensitive and biodegradable composite hydrogel, based on a methacrylated and succinic derivative of dextran, named Dex-MA-SA, and a methacrylated and succinic derivative of alpha,beta-poly( N-2-hydroxyethyl)- DL-aspartamide (PHEA), named PHM-SA, was produced by photocross-linking. The goal was to obtain a colon-specific drug delivery system, exploiting both the pH-sensitive behavior and the colon-specific degradability. The hydrogel prepared with a suitable ratio between the polysaccharide and the polyaminoacid was characterized regarding its swelling behavior in gastrointestinal simulated conditions, chemical and enzymatic degradability, interaction with mucin, and cell compatib…
Biodegradable hydrogels obtained by photocrosslinking of dextran and polyaspartamide derivatives
The functionalization of dextran with glycidyl methacrylate (GMA) leads to the formation of a derivative that generates hydrogels for irradiation at 365nm. The effects of various polymer concentrations and irradiation times on the yield and the properties of the obtained hydrogels are reported. The networks have been characterized by FT-IR spectra, dimensional analysis and swelling measurements carried out at different pH values. In vitro studies suggest that all samples undergo a partial chemical hydrolysis, whereas the incubation with dextranases causes a total degradation whose rate depends on the degree of crosslinking. In addition, aqueous solutions of functionalized dextran have been …
Chemical gels of scleroglucan obtained by cross-linking with 1,w-dicarboxylic acids: Synthesis and characterization
Chemical gels obtained by cross-linking reaction between scleroglucan and I, omega-dicarboxylic acids having a number of carbon atoms from 4 to 8 in the chain, have been prepared and characterised. The networks show properties correlated with the number of carbon atoms of the acid and with the molar ratio carboxylic acid/glucose unit of the polymer (r) employed in the cross-linking reaction. The diffusion of theophylline, chosen as model drug, through the swelled cross-linked polymers has been also investigated and it has enabled the diffusion coefficients of the drug to be calculated under different environmental conditions. The release profiles of theophylline from tablets prepared with t…