Gadolinium-Conjugated Lipoic Acid Hydrogels for Magnetic Resonance Imaging

Area of Science:

• Biomedical Engineering
• Materials Science
• Radiology

Background:

• Gadolinium-based contrast agents (GBCAs) are crucial for MRI.
• Developing stable and effective GBCA delivery systems is essential for advanced imaging.
• Lipoic acid (LA) hydrogels offer potential as biocompatible scaffolds.

Purpose of the Study:

• To synthesize and characterize a lipoic acid hydrogel incorporating a gadolinium-based contrast agent (Gd³⁺SS) for enhanced MRI.
• To evaluate the magnetic properties, stability, and *in vitro* behavior of the Gd³⁺-conjugated hydrogel (Gd³⁺Gel).
• To assess the potential of Gd³⁺Gel for tracking internal injuries and targeted imaging applications.

Main Methods:

• Conjugation of Gd³⁺SS to a lipoic acid hydrogel.
• Measurement of relaxivity (r₁) and rotational correlation time (τ_r) at varying magnetic field strengths.
• In vitro retention studies comparing covalent and noncovalent binding.
• Cell viability assays (PC3-PIP, RAW 264.7) and cellular uptake studies (ICP-MS, confocal microscopy).
• Rheological analysis to determine hydrogel viscosity.

Main Results:

• Gd³⁺Gel demonstrated a 2.8-fold enhancement in relaxivity (r₁) at 1.4 T due to increased rotational correlation time (τ_r).
• Covalent retention of Gd³⁺SS within the hydrogel was significantly higher (64.7%) compared to noncovalently bound gadoterate (14.0%).
• Hydrogel relaxation rate increased significantly with Gd³⁺Gel concentration.
• Cell viability was maintained with Gd³⁺SS, but reduced with Gd³⁺Gel, consistent with LA effects; cellular uptake was limited by the hydrogel structure.
• Rheology confirmed the injectable nature of the LA hydrogel.

Conclusions:

• The lipoic acid hydrogel effectively enhances MRI contrast agent performance.
• Gd³⁺Gel exhibits excellent retention, minimizing GBCA leaching.
• The injectable and stable nature of Gd³⁺Gel makes it a promising candidate for targeted internal injury tracking and controlled imaging during healing.