User:Maria Briscione/Notebook/Chem 571/2011/08/31

Biomaterials Design Lab

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Objective The purpose of the present subset of experiments was to monitor the change in concentration of AuNPs. Description Bovine serum albumin (BSA, 0.0015-0.015 mM), a weak reducing agent, was mixed at room temperature with HAuCl4 (0.25-1mM) in aqueous phase. For 6 hours the mixture was maintained in a thermostat at 40, 60, or 80 °C. A color change of colorless to pink then purple was observed and indicative of the reduction. After 6 hours, the samples were first cooled, kept overnight, and purified twice to remove excess BSA. Specifically, AuNPs were collected at 10000-14000 rpms for 5 minutes after washing with distilled water. UV spectrophotometer recorded UV- visible spectra of the prepared gold colloidal suspensions and a time dependent factor was determined by performing time dependent scans of choice reactions. Additionally, temperature monitoring over 20-70 °C range determined whether temperature was a significant factor. The pH of the samples was also determined. The various reaction solutions were contained in glass flasks that contained a double walled jacket. The temperature was maintained by use of externally circulating water while pH measurements were taken from a pH meter at regular increments for 6 hours. The following procedure was taken from Bakshi and colleagues (2011) and utilized for use by the Biomaterial Design Lab to determine a proper pH to synthesize AuNPs. 10 mL of Au3+ (0.25 mM) and BSA (0.0015 mM) were added to 10 mL of 50 mM of Tris Buffer (pH 7.55). Small portions of distilled water were used to aid in mixing the solutions. A UV-vis spectrum was analyzed at 0 seconds (t0) and after every thirty minutes was completed. The samples were placed in an 80 degree Celsius oven while the reaction proceeded. A spectrum of a blank solution of pH buffer was also analyzed. (.00084 g/mL) .0007 measured of chloroauric acid (.001g/mL) .0013 measured of BSA Data Notes Use categories like tags. Change the "Course" category to the one corresponding to your course. The "Miscellaneous" tag can be used for particular experiments, as instructed by your professor. Please be sure to change or delete this tag as required so that the categories remain well organized.