Dipyridamole-Coated 3D-Printed β-Tricalcium Phosphate Scaffolds: Spectrophotometric Characterization, Drug Release Kinetics, and In Vitro Evaluation to Guide Critical-Sized Bone Defect Repair Studies

Critical-sized bone defects remain a significant clinical challenge, and dipyridamole (DIPY)-coated 3D-tricalcium phosphate (β-TCP) scaffolds have shown promising osteogenic efficacy in preclinical models. However, the literature on the systematic physicochemical characterization of this scaffold system, including optimization of DIPY loading parameters, release kinetics, and surface properties, is lacking. This study addresses these gaps by characterizing DIPY-loaded 3D-printed β-TCP scaffolds across solid and porous architectures, three coating concentrations (10, 100, and 1000 µM), and three coating volumes (250, 500, and 1000 µL). Under static PBS conditions, drug release over 21 days was quantifiable only at 1000 µM, and release-kinetics modeling (zero-order, Higuchi, and Korsmeyer–Peppas) was therefore restricted to this highest concentration. At 1000 µM, both scaffold types showed biphasic release profiles, with standard empirical models reasonably approximating the overall kinetics, while not fully capturing the biphasic behavior over the entire duration. Porous scaffolds showed significant volume-dependent release (p = 0.002, η2 = 0.88), attributable to drug penetration into the interconnected macropore network, whereas solid scaffolds displayed volume-independent release confined to external surfaces. Scanning electron microscopy revealed concentration-dependent needle-shaped DIPY crystal deposition while contact angle measurements indicated no significant changes in surface hydrophilicity. MTT assay demonstrated biocompatibility at all concentrations, with viability influenced by coating volume rather than drug concentration. These findings establish a foundational physicochemical framework for DIPY-loaded β-TCP scaffolds, providing the baseline data necessary to guide subsequent biological evaluation and translational efforts toward critical-sized craniofacial and orthopedic bone defect repair.