A Novel Dual-Functional quercetin carrier based on Gd-MOF for drug delivery and MR imaging

• An amine-functionalized Gd-MOF (N-Gd-MOF) was developed as a high-capacity quercetin carrier (284 mg g –1 ). • Soxhlet activation tailors physicochemical, magnetic, and biological properties without affecting structural stability. • Adsorption kinetics and isotherm analyses revealed a pseudo-second-order and Langmuir-type adsorption behavior. • MRI analysis reveals that the r 1 relaxivity of 5d-S is 1.35 times higher than that of Dotarem. Metal-organic frameworks (MOFs) have emerged as versatile nanomaterials for biomedical applications due to their tunable porosity, high surface area, and structural diversity. In this study, amine-functionalized gadolinium-based MOFs (N-Gd-MOFs) were designed as dual-function platforms for quercetin (Qu) delivery and magnetic resonance imaging (MRI) contrast enhancement. Among the synthesized samples, the 5-day Soxhlet-activated (5d-S) MOF exhibited the highest specific surface area (23.92 m 2 /g) and a maximum Qu adsorption capacity of 280 mg·g –1 . The adsorption followed a pseudo-second-order kinetic model and Langmuir isotherm, indicating monolayer chemisorption on a homogeneous surface. Thermodynamic parameters (ΔG° = –4.3 kJ·mol –1 ; ΔH° = +4.09 kJ·mol –1 ) confirmed that the process is endothermic and spontaneous. The r 1 relaxivity of 5d-S (6.21 mmol/L·s) exceeded that of the clinical contrast agent Dotarem (4.26 mmol/L·s), while maintaining excellent biocompatibility (>100 % cell viability at ≤ 80 µg/mL). The material exhibited pH-responsive drug release (∼16 % over 70 h), consistent with a quasi-Fickian diffusion mechanism. These findings demonstrate that the optimized N-Gd-MOF (5d-S) integrates efficient drug loading, MRI contrast enhancement, and biocompatibility, making it a promising smart theranostic nanocarrier for combined drug delivery and imaging applications.