Facile synthesis of non-ionic dimeric molecular resonance imaging contrast agent: its relaxation and luminescence studies

Abstract

A bis-polyazamacrocycle, 10′-bis(acetamido)ethane-bis[1,4,7-tri(carboxymethane)-1,4,7,10-tetraazacyclododecane] (DO3A-AME-DO3A) was synthesized for application in magnetic resonance imaging. The efficacy of DO3A-AME-DO3A as non ionic magnetic contrast agent was tested by performing relaxometric studies on its gadolinium complex. The longitudinal relaxivity, r₁ and transverse relaxivity, r₂ values were found to be 5.84 mM⁻¹s⁻¹ and 6.82 mM⁻¹s⁻¹, per Gd(III) at pH 7.0, 37 °C. The luminescence properties of europium complex of DO3A-AME-DO3A were investigated in aqueous medium. The lifetime of Eu₂-DO3A-AME-DO3A in water was found to be 0.786 ms. Emission and luminescence lifetime measurements on the europium complex of DO3A-AME-DO3A gives a hydration number of q = 1.9. The reaction enthalpy and entropy were found to be, ΔH₀ = − (6.2 ± 2) kJ mol⁻¹, ΔS₀ = − (1.8 ± 0.4) kJ mol⁻¹K⁻¹, and K_Eu²⁹⁸ = (1.8 ± 0.1).