PT  - JOURNAL ARTICLE
AU  - Mohammed Bhuiyan
AU  - Anna Kucharski
AU  - Richard Freifelder
AU  - Lisa Won
AU  - Richard Kraig
AU  - Chin-Tu Chen
TI  - Semi-automatic radiolabeling of insulin-like growth factor-1 protein for the verification of its nose-to-brain delivery by positron emission tomography imaging.
DP  - 2020 May 01
TA  - Journal of Nuclear Medicine
PG  - 512--512
VI  - 61
IP  - supplement 1
4099  - http://jnm.snmjournals.org/content/61/supplement_1/512.short
4100  - http://jnm.snmjournals.org/content/61/supplement_1/512.full
SO  - J Nucl Med2020 May 01; 61
AB  - 512Introduction: Insulin-like growth factor-1 (IGF-1) is important in the regulation of normal physiology and a number of pathological states such as cancer. Being the naturally occurring ligand for the IGF-1 receptor it is interesting for PET imaging of receptor expression. Generally, 18F is incorporated into a peptide through the attachment of a radiolabeled prosthetic group the most common being 4-fluorobenzoate and 2-fluoropropionate. We report the labeling of IGF-1 protein with 18F 2-fluoropropionate in two steps using a preparative HPLC for PET by intranasal delivery. Methods: Carrier‐free 18F-fluoride anions were produced by our cyclotron. A Synthera synthesizer with HPLC capabilities and standard nucleophilic integrated fluidic processors were used without any modifications. A work-up frame exchanged the HPLC solvents of radiolabeled prosthetic group to DMSO, for the next step radiolabeling reaction. 18F was trapped on a QMA cartridge and eluted using 15 mg Kryptofix in 0.8 mL of acetonitrile and 1.4 mg K2CO3 in 0.2 mL of water. The 18F-Kryptofix was dried at 110 °C for 5 minutes and 95 °C for 4 minutes under periodic vacuum and helium flow. After drying, the 4-nitrophenyl 2-19Ffluoropropanoate (NFP), 20 mg in 1.5 mL t-BuOH: acetonitrile (4:1) was added and labelling was achieved by heating to 100 °C for 5 minutes. The solvents (t-BuOH-MeCN) were evaporated to about half volume under vacuum and helium flow for 4 minutes and the residue was diluted with 60% Acetonitrile, 5 mL, and transferred to the injector loop. The crude reaction mixture was purified by the HPLC system with a Waters Symmetry Prep C18, 7μm, 10 x 300 mm column and a constant eluent flow at a speed of 8.0 mL/min. The 18F-NFP peak was collected at ~15 minutes, transferred via vacuum to the work-up frame where it was diluted in 80 mL of water and subsequently trapped on the preconditioned solid phase extraction cartridge. After drying that PS-RP under vacuum for 2 minutes, 18F-NFP was eluted to the second Synthera unit with 1 mL of DMSO and transferred to the reaction vessel. The IGF-1, 1 mg in 0.7 mL DMSO:TEA (100:1), was added and labelling was achieved by warming to 40 °C for 5 minutes. The reaction mixture was diluted with 7 mL of 1x PBS, pH 7, and transferred to the product vial. A portion of the crude 18F labeled IGF-1 protein was then filtered using the 0.5 mL capacity Amicon Ultra 3,000 MWCO regenerated cellulose membrane centrifugal filter units. A 7-minute filtering cycle at 12,000 g speed on an Eppendorf microcentrifuge was followed by two additional PBS washing cycles. produced a 54% decay corrected yield and 93% radiochemical yield (Figure 2). Results: 18F-IGF-1 was obtained in decay corrected radiochemical yields of 54 ± 0.5% (n = 3) and radiochemical purity of 93 ± 1%. Chemical purity was more than 99%. Specific radioactivity was determined to be ~5 GBq/µmol at the end of synthesis and the total synthesis plus dose preparation time was 120-minutes. Utilizing the high molecular weight of the protein, the crude was purified, and dose reconstituted in a single step by the centrifugal dialysis membrane filtering, which was time saving and more efficient than HPLC purification. Conclusions: The IGF-1 protein was radiolabeled in two-steps through the 18F labeled prosthetic group 4-nitrophenyl 2-18F-fluoropropanoate (18F-NFP). The first step prosthetic group radiosynthesis was done using an standard nucleophilic synthesizer equipped with a preparative-HPLC and a work-up frame. The (18F-NFP) was used in a second nucleophilic module for the labeling of IGF-1. The labeled product was then purified, and the dose reconstituted by a centrifugal filter membrane with excellent radiochemical purity and yield. Preliminary results confirmed their delivery efficacy as brain imaging agent via intranasal delivery of 18F IGF-1. Supporting Documentation: