Fluorescence Quenching of b-Casein by Silver Nanoparticles and Copper Nanoparticles in Presence of Sugars: A Quantitative Exploration

Abstract

INTRODUCTIONInvention of non-invasive in vivo biosensors is today's necessity in diagnostics, medical analysis and therapy [1,2]. Detection and estimation of sugars in biological systems attract the attention of medical engineers. When protein-carbohydrate interactions are studied and established in presence of silver and copper nanoparticles, new immunotherapeutic strategies may be discovered in the treatment of malignant diseases [3]. In this paper the studies on the interaction of silver nanoparticles (AgNP) and copper nanoparticles (CuNP) with milk protein, β-casein (BCA) is quantitatively described using fluorescence quenching measurements. The interaction studies between the protein and the nanoparticles (Pro-NP) are extensively studied in presence of various monosaccharide and disaccharide sugars like glucose, fructose, galactose, sucrose, maltose and lactose. The protein β-casein (BCA) exhibits a strong fluorescence emission, which is sensitive to active quenchers. Metal nanoparticles like copper nanoparticles and silver nanoparticles with enhanced and unique properties are reported to quench protein fluorescence appreciably. In the present work, the fluorescence quenching effects of metal nanoparticles on the protein fluorescence are extensively studied in presence of various sugar molecules. This may play a significant role in the sensing applications of sugar molecular systems in the presence of metal nanoparticles. β-Casein is used as fluorophore and sugar molecular systems like sucrose, maltose, fructose, lactose, galactose and glucose are chosen as quenchers and the protein-sugar interactions are arrived from fluorescence quenching results in the presence of copper nanoparticles and silver nanoparticles. To find the role of life time on the intensity of fluorescence, time resolved fluorescence measurements for the protein-sugar systems in the presence and absence of nanoparticles is measured. The proteinnanoparticles-sugar fluorescence interactions are analyzed by using Stern-Volmer plots and thermodynamic plots using fluorescence intensity quenching data. The trends in the extent of quenching action on protein fluorescence and also the binding interactions among protein sugar systems are quantified in the presence of copper nanoparticles and silver nanoparticles separately, in terms of Stern-Volmer constant values and binding constants values. β-Casein is found to interact strongly with the quenchers in the presence of copper nanoparticle and silver nanoparticle. Silver nanoparticle is read to be a better quenching mediator than copper nanoparticle for the fluorescence intensity in molecular interactions. Order of sugars quenching the protein fluorescence in presence of the nanoparticles is found.

Impact of nanogold morphology on interactions with human serum

“…44 Furthermore, the binding constant kb and number of binding sites n are intrinsically linked, with higher kb values observed where increased affinity is observed. 46 Commonly, kb values follow similar trends to the KSV values. This holds true in our current study (AuNR > AuNS > AuNC > AuNPr), with a notable observation that depending on the concentration of AuNPr, its binding affinity towards HSA may vary, such that increasing concentrations of AuNPr with a fixed amount of HSA greatly improves its binding affinity.…”