A portable test system (PTS) for determination of bacterial endotoxins in 18F-FDG radiopharmaceutical

Abstract

Introduction: Pyrogens include any substance capable of eliciting a febrile response upon injection or infection. Endotoxin is a type of pyrogen that is strictly of gram-negative origin, a natural complex of lipopolysaccharide ocurring in the outer layer of the bilayered gram-negative bacterial cell. An automated portable test system (PTS) has been developed for determination of bacterial endotoxins in water, in-process and end-products using the Limulus amebocyte lysate (LAL) kinetic chromogenic test. The aim of this work was to validate this method for 18F-FDG radiopharmaceutical. Materials and methods: Experiments were performed in three batches of 18F-FDG produced at IPENCNEN/ SP in a portable test system (PTS) from Endosafe, Inc.TM, Charleston, SC. Single polystyrene cartridges containing dry LAL-reagents, control standard endotoxin (CSE) and synthetic color substrate were used. The LAL sensitivity was 0.05 EU mL-1. 25 µL samples of the product in serial dilutions were pipetted into the cartridge wells and the temperature of the reaction was 37 ± 1 ºC. Results were obtained for the endotoxin concentration in samples by interpolation of an archived standard curve (5.0; 0.5 and 0.05 EU mL-1) at OD (optical density) 405 nm, after 20 minutes. Results: The maximum valid dilution was calculated to establish the extent of dilution to avoid interfering test conditions (MVD = 500). The endotoxin concentration was lower than the lowest concentration of the standard curve in all samples, and the parameters of coefficient correlation (R) < 0.980, recovery of positive product control (RPPC) 50-200% and coefficient variation (CV) of the samples < 25% were satisfied from 1:5 until 1:50 dilution factor. Discussion/conclusion: The PTS is a new kinetic chromogenic technique for bacterial endotoxin determination. Especially for short-lived radiopharmaceuticals, it trends to be the method of choice. The technique showed to be simple, easy, fast and accurate and the validation was successfully performed.