Protein Biophosphors: Biodegradable, Multifunctional, Protein-Based Hydrogel for White Emission, Sensing, and pH Detection

A highly efficient, multifunctional, bioderived white-emitting hydrogel (biophosphor) consisting of crosslinked bovine serum albumin and three fluorescent dyes, Coumarin 460, fluorescein, and 5(6)-carboxy-x-rhodamine, is reported here. White emission is obtained upon excitation of the biophosphor at 365 nm with appropriate mole ratios of the above dyes. The CIE 1931 chromaticity coordinates of white emission with 365 nm excitation are (0.36, 0.37), and the correlated color temperature is 5300 K. Multifunctional nature of the biophosphor is also demonstrated. A UV-light-emitting-diode (361 nm) coated with this biophosphor, for example, indicates white emission (CIE 0.28, 0.31) with a half-life of 106 (+/- 5) h. The white emission is also highly sensitive to pH over a broad range (pH 1-11). Incorporation of glucose oxidase and peroxidase in the biophosphor allows for the detection of glucose over a physiologically relevant range of 1.8-288 mg dL(-1). This is a unique, advanced biophosphor with LED and sensing applications, and it is the first example of a multifunctional, proteinaceous white emitter.