A container closure system that allows for greater recovery of radiolabeled peptide compared to the standard borosilicate glass system

• We examined the adhesion of 68Ga-DOTATOC to glass and CZ CCS.
• The adhesion of the 68Ga-DOTATOC was 10% less in CZ CCS compared to glass CCS.
• Overall recovery of 68Ga-DOTATOC reaction solution is higher in CZ CCS than glass CCS.
• Adhesion to the CCS is due to 68Ga-DOTATOC, not 68Ga-chloride.

ObjectivesOften peptides used in synthesis of radiopharmaceutical PET tracers are lipophilic and adhere to the walls of container closure systems (CCS) such that costly peptide and product are not fully recoverable after synthesis occurs. This investigation compares a standard United States Pharmacopeia (USP) Type I borosilicate glass CCS to a cyclic polyolefin copolymer Crystal Zenith® (CZ) CCS, for 68Ga-chloride and 68Ga-DOTATOC ([68Ga] Ga-DOTA-d-Phe1-Tyr3-octreotide) retention in the reaction vial after labeling.Methods68Gallium labeling of DOTATOC was conducted by adding 68Ga-chloride, 2 M HEPES (4-(2-hydroxyethyl)piperazine-1-ethanesulfonic acid) or 0.75 M sodium acetate, and 1–30 µg of DOTATOC into the CZ or glass CCS. The reaction mixture was heated for 15 min and cooled to room temperature. The crude reaction mixture was then withdrawn via syringe, for final processing. The CCS was then assayed using a dose calibrator to determine the amount of retained 68Ga-DOTATOC. Statistical significance was assessed using an unpaired Student's t-test.ResultsIn all experiments (n=72) with various amounts of peptide and different buffering systems, the CZ CCS retained less activity than the glass CCS. Using 2 M HEPES and 15 µg or 30 µg of DOTATOC, the CZ CCS retained approximately 10% less of the labeled DOTATOC compared to the glass CCS (p<0.05). Utilizing either a sodium acetate or a HEPES buffering system with 15 µg or 30 µg of DOTATOC, the CZ CCS retained approximately 2.5% less of the total reaction activity compared to the glass CCS (p<0.05). Product yield was equivalent in glass and CZ CCS under the same reaction conditions. Both the CZ and glass vials showed no retention of 68Ga-chloride.ConclusionFor applications involving the labeling of peptides such as 68Ga-DOTATOC, the CZ CCS compared to the glass CCS, results in an improved recovery of product.