In this work three new macrocyclic gadolinium complexes (Gd-DO3A-ADA, Gd-DO3A-MAD and Gd-DO3A-APP) have been syntesised. This was done in order to study how the introduction of hydrophobic groups on DO3A affected the albumin binding and hence the T1-relaxivity. Gd-DTPA was used as a control in the study.
Gd-DO3A-MAD showed the highest degree of albumin binding (60%). Gd-DO3A-ADA did also have some affinity for albumin (19%) while Gd-DO3A-APP did not have any degree of albumin binding at all.
The T1-relaxivity for all substances was close to 4.0mM-1 s-1 in a phosphate buffer solution (pH 7.4). In a 4% BSA solution the T1-relaxivity increased for Gd-DO3A-MAD and Gd-DO3A-ADA. Gd-DO3A-APP did not show any significant increase in the T1-relaxivity.
It was attempt to displace Gd-DO3A-MAD from albumin by adding oxazepam, warfarin and caprylic acid to the solution. By adding caprylic acid to albumin before Gd-DO3A-MAD, a decrease in the T1-relaxivity was observed compared to the solution of only Gd-DO3A-MAD in albumin.