Microfluidic radiolabeling of biomolecules with PET radiometals.
BACKGROUND
A robust, versatile and compact microreactor has been designed, fabricated and tested for the labeling of bifunctional chelate conjugated biomolecules (BFC-BM) with PET radiometals.


METHODS
The developed microreactor was used to radiolabel a chelate, either 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) or 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA) that had been conjugated to cyclo(Arg-Gly-Asp-DPhe-Lys) peptide, with both ⁶⁴Cu and ⁶⁸Ga respectively. The microreactor radiolabeling conditions were optimized by varying temperature, concentration and residence time.


RESULTS
Direct comparisons between the microreactor approach and conventional methods showed improved labeling yields and increased reproducibility with the microreactor under identical labeling conditions, due to enhanced mass and heat transfer at the microscale. More importantly, over 90% radiolabeling yields (incorporation of radiometal) were achieved with a 1:1 stoichiometry of bifunctional chelate biomolecule conjugate (BFC-BM) to radiometal in the microreactor, which potentially obviates extensive chromatographic purification that is typically required to remove the large excess of unlabeled biomolecule in radioligands prepared using conventional methods. Moreover, higher yields for radiolabeling of DOTA-functionalized BSA protein (Bovine Serum Albumin) were observed with ⁶⁴Cu/⁶⁸Ga using the microreactor, which demonstrates the ability to label both small and large molecules.


CONCLUSIONS
A robust, reliable, compact microreactor capable of chelating radiometals with common chelates has been developed and validated. Based on our radiolabeling results, the reported microfluidic approach overall outperforms conventional radiosynthetic methods, and is a promising technology for the radiometal labeling of commonly utilized BFC-BM in aqueous solutions.
Radiological Sciences Division, Mallinckrodt Institute of Radiology, Washington University School of Medicine, 510 South Kingshighway Blvd., St. Louis, MO 63110, USA.
Dexing
D
Zeng
Amit V
AV
Desai
David
D
Ranganathan
Tobias D
TD
Wheeler
Paul J A
PJ
Kenis
David E
DE
Reichert
D003301:Copper Radioisotopes / Q000737:chemistry*; D004129:Dimethylpolysiloxanes / Q000737:chemistry; D005710:Gallium Radioisotopes / Q000737:chemistry; D005898:Glass / Q000737:chemistry; D006571:Heterocyclic Compounds / Q000737:chemistry; D006573:Heterocyclic Compounds, 1-Ring / Q000737:chemistry; D007553:Isotope Labeling / Q000295:instrumentation*; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation*; D009842:Oligopeptides / Q000737:chemistry; D049268:Positron-Emission Tomography; D013696:Temperature; D013997:Time Factors
D003301:Copper Radioisotopes; D004129:Dimethylpolysiloxanes; D005710:Gallium Radioisotopes; D006571:Heterocyclic Compounds; D006573:Heterocyclic Compounds, 1-Ring; D009842:Oligopeptides; C084961:arginyl-glycyl-aspartyl-phenylalanine; C071349:1,4,7,10-tetraazacyclododecane- 1,4,7,10-tetraacetic acid; C048993:1,4,7-triazacyclononane-N,N',N''-triacetic acid; C013830:baysilon