ABSTRACT
Allergic reactions to sulfonamide-based drugs are quite common; hence, medications containing sulfonamides are prescribed carefully. Metal ion complexation may block the nitrogen binding site of sulfonamide by complexation and reduce such responses. In this study, trace concentrations of Zn were found to bind with sulfanilamide at pH â¼ 1. The complexation was studied in water as well as in vesicular medium of polyethylene glycol (PEG) and a block copolymer, PPG-PEG-PPG. The binding constants (k) of Zn-sulfanilamide complex were determined in water, PEG, and PPG-PEG-PPG block copolymer media. The values suggest that complexation occurs best in water followed by PPG-PEG-PPG, PEG #4000, and PEG #12000. Though the binding constants are high in water and block copolymer media, the complex is not very stable as the absorbance value for the complex was found to decline with time. The same complex when prepared in polymer matrix shows higher stability. The results prompted us to explore the extraction possibilities of the Zn-sulfanilamide complex by using aqueous biphasic extraction systems comprising the polymers against sodium sulfate solution. The complex was analyzed for its allergenic response in different media by competitive enzyme-linked immunosorbent assay (ELISA) technique. The allergic response of the compounds in the respective media is the resultant of the binding constant and the stability of the complex in that particular medium.
ABSTRACT
Fluorescence in poly(ethylene glycol) (PEGs 400-12000) solutions is reported here for the first time. PEG solutions form a vesicular organization with the hydrophilic groups attached at both ends which arrange themselves beyond a particular concentration and offer electron-dense regions at the center of the vesicle. These vesicles provide an inherent site for fluorescence generation in PEG solutions. Fluorescence emission was observed at ~380 nm with an excitation wavelength of 300 nm. PEG of molecular weight 6000 was found to show maximum emission intensity at a particular concentration. The formation of PEG vesicles (~1 nm size) was confirmed by dynamic light scattering (DLS) and confocal laser microscopy. On addition of metal ions the polymeric vesicle breaks up to monomeric PEG, and hence, the fluorescence intensity decreases with a red shift. Fluorescence lifetime measurements indicate the nature of complexation of the metals with PEG. Since PEGs are used as one of the phases in aqueous biphasic systems (ABS) of liquid-liquid extractions, the nature of the fluorescence emission spectrum of the PEG phase after extraction was studied. Metal extraction in the PEG-rich phase of an ABS leads to quenching of fluorescence in PEG.
