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Synthesis of Fluorescent Gels of Gold made using Proteins

Radha Perumal Ramasamy 1Shihabudeen M. Maliyekkal 2

1. Anna University, Department of Applied Science and Technology, ACT campus (ACT), Chennai 600 025, India
2. VIT University,School of Mechanical and Building Sciences, Chennai Campus (VIT), Chennai 600 127, India


                Gels are interesting class of materials that comprise of three dimensional networks swollen by large amount of solvent. In their rheological characteristics their storage modulus is lower than their loss modulus. They have solid like behavior in macroscopic scale and liquid like behavior in microscopic scales. They are classified as physical gels and chemical gels. Physical gels result due to formation of aggregates while chemical gels are formed due to covalent bonds. Gels have several applications that include biotechnology, micro fluidics and lab on a chip. In this research, gels were made using BSA. BSA is a globular protein. The presence of aminoacids like lysine can provide active sites on the surface of BSA for the formation of nanoparticles. Here solutions containing different concentrations of BSA were mixed with HAuCl4 of concentration 5mM. To this NaOH was added to have a final concentration of 250mM NaOH. It was observed that for concentration of HAuCl4 greater than 50 mg/ml, gels were formed. The gels were found to be fluorescent. Their photoluminescence properties were measured and emission peak was observed at 700 nm. Their rheological behavior was also examined. Interestingly, the gels were found to collapse after a while. SEM analysis showed that the solutions containing BSA of concentration 25 mg/ml had nanoparticles in it. In time all the samples became brown in color indicating the formation of nanoparticles.The formation and the collapse of the gel is attributed to the formation of nanoparticles and the subsequent weakening of the chitosan-chitosan bond due to the nanoparticles. The secondary  structural modifications were characterized using FTIR spectroscopy and it was observed that as the concentration of the proteins decreased the second derivative peak shifted to position for random coil (1640 cm-1). This indicates that the structure of the protein changes from helical to random coil as the nanoparticles form. XRD analysis was also done on the samples. A model is proposed for the formation of the fluorescent gels. 


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Related papers

Presentation: Oral at 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17, General Session 3, by Radha Perumal Ramasamy
See On-line Journal of 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17

Submitted: 2013-04-14 09:35
Revised:   2013-04-15 07:35