ABSTRACT
Large volume parenteral solutions (LVPS) that are widely used in the healthcare system must be processed by moist-heat treatment to an assured sterility level in which the efficacy is measured by a bioindicator (BI) that provides fast, accurate and reliable results. This study evaluated the thermal stability of green fluorescent protein (GFP) into glucose-based LVPS (1.5-50%) solutions to determine its utility as a BI for thermal processes. GFP, expressed by Escherichia coli, isolated/purified by TPP/HIC, was diluted in buffered (each 10mM: Tris-EDTA, pH 8; phosphate, pH 6 and 7; acetate, pH 5) and in water for injection (WFI; pH 6.70+/-0.40) glucose solutions (1.5-50%) and exposed to constant temperatures from 80 degrees C to 95 degrees C. The thermal stability was expressed in decimal reduction time (D-value, time required to reduce 90% of the GFP fluorescence intensity). At 95 degrees C, the D-values for GFP in 1.5-50% glucose were: (i) 1.63+/-0.23 min (pH 5); (ii) 2.64+/-0.26 min (WFI); (iii) 2.50+/-0.18 min (pH 6); (iv) 3.24+/-0.28 min (pH 7); (v) 2.89+/-0.44 min (pH 8). By the convenient measure of fluorescence intensity and its thermal stability, GFP has the potential as a BI to assay the efficacy of moist-heat processing of LVPS at temperatures < or =100 degrees C.
