A Theranostic Agent Combining a Two-Photon-Absorbing Photosensitizer for Photodynamic Therapy and a Gadolinium(III)...

Area of Science:

• Medicinal Chemistry
• Biomedical Imaging
• Photodynamic Therapy

Background:

• Development of theranostic agents for combined diagnosis and therapy is crucial.
• Existing agents often lack efficiency or specificity.
• Need for agents with enhanced two-photon properties for deeper tissue penetration.

Purpose of the Study:

• To synthesize and characterize a novel theranostic agent, [DPP-ZnP-GdDOTA](-).
• To evaluate its potential for photodynamic therapy (PDT) and magnetic resonance imaging (MRI).
• To assess its two-photon absorption properties and singlet oxygen generation.

Main Methods:

• Convergent synthesis of the [DPP-ZnP-GdDOTA](-) conjugate.
• Characterization using Nuclear Magnetic Relaxation Dispersion (NMRD) to determine relaxivity.
• Measurement of two-photon absorption cross-sections and singlet oxygen quantum yields.
• In vitro cellular studies to assess dark toxicity and phototoxicity.

Main Results:

• The [DPP-ZnP-GdDOTA](-) conjugate exhibited high longitudinal water proton relaxivity (19.94 mm⁻¹ s⁻¹).
• Significant two-photon absorption cross-sections (approx. 1000 GM) were observed between 910-940 nm.
• Efficient singlet oxygen generation (quantum yields of 0.42-0.68) was confirmed.
• The conjugate showed low dark toxicity and induced significant one-photon and moderate two-photon phototoxicity in cancer cells.

Conclusions:

• The synthesized [DPP-ZnP-GdDOTA](-) conjugate is a promising theranostic agent.
• Its properties support applications in both MRI and two-photon PDT.
• Further investigation is warranted for its clinical translation.