Controlled Release of Herbicides Supported on Polysaccharide Based Hydrogels

Polymeric hydrogels based on polysaccharides, hydroxyethylcellu lose and dextran, were attained by cross-linking with epichlorohydrin. The cross-linked polymer beads were loaded with 2,4-dichlorophenoxyacetic acid by direct esterification in the presence of carbonyldiimidazole. Loads ranging be tween 0.5 and 2.2 mol of 2,4-dichlorophenoxyacetyloyl groups per glucose unit were obtained. The release of 2,4-D herbicide was investigated in buffered aqueous solution at different pH values (4, 7 and 9) and evaluated with respect to different structural parameters, such as nature of the polymer matrices, cross-linking extent and herbicide loading. A fairly slow release, ranging from 10 to 25% after four months, was recorded under neutral and acid conditions, whereas at pH 9 an initial burst in the release profile, reaching almost 90% release of 2,4-D loading, was observed. In the majority of the cases, the release kinetics are reproduced by the combination of two exponential decay processes, that differ by about three orders of magnitude in their absolute rates.

New hydrophilic polyesters and related polymers as bioerodible polymeric matrices

A survey is reported on our activity performed in the last few years on the preparation of new synthetic and semisynthetic polymeric materials endowed with bioerodible-biodegradable characteristics and designed for applications in the practice of controlled release of active principles of pharmaceutical and agrochemical significance. The presentation of the results will be arranged into the following sections: (1) hydroxyl containing polyesters, that comprise polymerization products based on racemic and optically active glyceric acid, or attained by polyaddition reactions among cyclic anhydrides, including also carbon dioxide, with monoglycidyl ethers of reversibly protected polyols. In this class are also presented the related polyhydroxylated systems obtained by selective grafting functional epoxides on cyclodextrins. (2) Bioerodible carboxyl containing polymeric systems as derived from the alternating copolymerization of maleic anhydride with alkyl vinyl ethers followed by partial esterification of maleic anhydride groups. (3) Linear and cross-linked functional polymers of synthetic and semisynthetic origin with hydrogel forming capability. Typical examples of their applications in the release of drugs and phytodrugs are also presented.

Biodegradation of nonionic surfactants. I. Biotransformation of 4-(1-nonyl)phenol by a Candida maltosa isolate

Results are reported concerning biodegradation of 4-(1-nonyl)phenol by cultures of a Candida maltosa strain isolated from aerobic sludge samples collected at a depuration plant treating wastewaters from a textile industry. The yeast was able to utilize 4-(1-nonyl)phenol as a sole carbon and energy source. Preliminary attempts to draw the actual metabolic pathway evidenced microbial attack on the alkyl chain with the production of 4-acetylphenol. To the best of our knowledge this is the first report describing a microorganism capable of attacking nonylphenol in axenic culture and at the same time allowing for the identification of its degradation products.