Structural and therapeutic properties of salicylic acid-solubilized Pluronic solutions and hydrogels.

Salicylic acid (SA) finds extensive applications in the treatment of rheumatic and skin diseases because of its analgesic, anti-inflammatory and exfoliating properties. As it is lipophilic in nature, there is a need for appropriate delivery systems to harness these properties for different applications. Herein, we examined the suitability of Pluronic P123/F127 micellar systems as delivery media by investigating the structural, flow and antimicrobial properties of P123/F127-SA solutions and hydrogels using DLS, SANS, rheological and zone inhibition measurement techniques. SA modulates the aggregation characteristics of these surfactant systems and brings about spherical-to-worm-like micelle-to-vesicular structural transitions in the hydrophobic Pluronic P123 system, a spherical-to-worm-like micellar transition in the mixed P123/F127 system and an onset of inter-micellar attraction in the hydrophilic Pluronic F127 system. SA-solubilized systems of both hydrophobic and hydrophilic Pluronics inhibit the growth of Gram-positive and Gram-negative bacteria with comparable MIC values. This suggests that the interaction of SA molecules with the bacterial cell membrane remains unobstructed upon encapsulation in Pluronic micelles. F127 hydrogel-based SA formulations with rheological properties suitable for topical applications and up to 15% SA loading were prepared. These will be useful SA ointments as F127 is an FDA-approved excipient for topical drug delivery applications. The results indicate that Pluronics remain effective as delivery agents for SA and exhibit interesting structural polymorphism upon its solubilization.

Evaluation of uranium removal by Hydrilla verticillata (L.f.) Royle from low level nuclear waste under laboratory conditions.

The present study evaluated uranium (U) removal ability and tolerance to low level nuclear waste (LLNW) of an aquatic weed Hydrilla verticillata. Plants were screened for growth in 10%-50% waste treatments up to 3 d. Treatments of 20% and 50% waste imposed increasing toxicity with duration assessed in terms of change in fresh weight and in the levels of photosynthetic pigments and thiobarbituric acid-reactive substances. U concentration, however, did not show a progressive increase and was about 42 µg g(-1) dw from 20% to 50% waste at 3 d. This suggested that a saturation stage was reached with respect to U removal due to increasing toxicity. However, in another experiment with 10% waste and 10% waste+10 ppm U treatments, plants showed an increase in U concentration with the maximum level approaching 426 µg g(-1) dw at 3 d without showing any toxicity as compared to that at 20% and 50% waste treatments. Hence, plants possessed significant potential to take up U and toxicity of LLNW limited their U removal ability. This implies that the use of Hydrilla plants for U removal from LLNW is feasible at low concentrations and would require repeated harvesting at short intervals.

Investigation of uranium accumulation potential and biochemical responses of an aquatic weed Hydrilla verticillata (L.f.) Royle.

The uranium (U) accumulation potential and ensuing biochemical responses were studied in Hydrilla verticillata (L.f.) Royle upon exposure to U (0, 20 and 100 mg L(-1)). There was a concentration-duration dependent increase in U accumulation with the maximum being 78 mg g(-1) DW at 100 mg L(-1) U after 24 h. Plants experienced an initial phase of the maximum toxicity (within 30 min) followed by almost complete recovery after 24 h. The recovery was attributed to an integrated modulation in the level of both enzymatic and molecular antioxidants (viz., guaiacol peroxidase, ascorbate peroxidase, catalase, proline, total phenolics) and also the constituents of thiol metabolism (viz., cysteine and glutathione). Thus, plants were found to be able to accumulate significant amount of U in a short time and to tolerate it efficiently. Hence, they may find application in U phytoremediation considering there accumulation ability, fast growth due to weed-like habit and world-wide distribution.

Uranium(VI) biosorption by dried roots of Eichhornia crassipes (water hyacinth).

Uranium uptake by dried roots of Eichhornia crassipes was rapid and the biomass could remove 54% of the initial uranium present within 4 min of contact time. The process was favored at pH 5-6 and was least influenced by temperature. Biosorption data fitted to both Langmuir and Freundlich isotherm. The maximum loading capacity obtained was 371 mg U/g dry biomass. Distribution coefficient of 9336 ml/g was observed at a residual concentration of 4.9 mg U/L. Uptake increased at higher dose of biomass and reached a plateau beyond the concentration of 6 g/L. The specific metal ion uptake decreased with increasing initial uranium concentration. Anions (0.1 M) inhibited the uptake and followed the trend acetate > sulphate > nitrate > chloride. However presence of carbonate had no effect on uranium biosorption.