Synthesis of a new NIR fluorescent Nd complex labeling agent

Area of Science:

• Biochemistry
• Analytical Chemistry
• Biotechnology

Background:

• Fluorescent analysis is crucial in biological and chemical research.
• Effective fluorescent labeling agents require NIR emission, large Stoke's shift, and minimal interference with the labeled compound's properties.

Purpose of the Study:

• To develop a novel NIR fluorescent labeling agent, M-AMF-DOTA(Nd), with desirable characteristics.
• To synthesize and characterize M-AMF-DOTA(Nd) and its avidin conjugate (Avidin-AMF-DOTA(Nd)).
• To evaluate the biological and physicochemical properties of the avidin conjugate.

Main Methods:

• Synthesis of M-AMF-DOTA(Nd) from 4-amino-fluorescein.
• Conjugation of M-AMF-DOTA(Nd) to avidin via Lys-side chains using 2-iminothiolane.
• Comparative evaluation of fluorescent features.
• Binding assay with D-biotin and tumor cell-uptake study.

Main Results:

• M-AMF-DOTA(Nd) was synthesized with a 22% overall yield.
• The agent exhibited typical NIR fluorescence (880 nm, 900 nm) from the Nd ion upon 488 nm excitation.
• Avidin-AMF-DOTA(Nd) retained fluorescent intensity and binding affinity to D-biotin, similar to native avidin.
• The avidin conjugate showed comparable tumor cell uptake to established fluorescent avidin.

Conclusions:

• M-AMF-DOTA(Nd) is a promising NIR fluorescent labeling agent.
• The developed agent fulfills key requirements for effective fluorescent labeling.
• Avidin-AMF-DOTA(Nd) demonstrates preserved biological and physicochemical properties post-conjugation.