[18F]F-DOPA synthesis by poly(dimethylsiloxane)-based platforms: thermal aging protocol to reduce chemicals-induced damage

Abstract 6-[ 18 F]fluoro-3,4-dihydroxyphenylalanine ([ 18 F]F-DOPA) is a diagnostic positron emission tomography agent, widely used in imaging the loss of dopaminergic neurons in Parkinson’s disease and, recently, to detect, stage and restage neuroendocrine tumors and to search for recurrence of viable glioma tissue. In this paper, we establish a protocol of thermal aging (i.e., heating timescales of the order of 24 h and temperatures higher than 120 °C) against the swelling and morphological surface degradation (inspected by microscope imaging) of poly(dimethylsiloxane) (PDMS) by dichloromethane (DCM) and hydriodic acid (HI), that are chemicals involved in the microfluidic synthesis of [ 18 F]F-DOPA. Swelling tests on PDMS channels heated at 150 °C (for 24 and 48 h) and 180 °C (for 24 h) confirm a percentage change of the channel dimension as low as 2–8% after loading with DCM. Also, X-ray photoelectron spectroscopy analysis is presented to illustrate changes of surface chemistry following treatments with DCM, HI and an aqueous solution containing 19 F-fluoride as one of the products (impurities) in the [ 18 F]F-DOPA synthesis. Rinsing with distilled water was demonstrate to allow removal of any chemical contamination from the PDMS surface treated with HI and a [ 18 F]-fluoride-based solution, which is critical to synthesize high-purity (≥98%) [ 18 F]F-DOPA to be clinically used.