TGF-β1/BSA coating modulates multi-phasic scaffolds for osteochondral tissue regeneration

Bioinspired scaffolds, designed to replicate distinct regions and mimic stratified anatomical architecture, have emerged as a promising approach for addressing osteochondral defects (a joint injury affecting both cartilage and underlying bone). Despite extensive preclinical research, the challenge of integrating newly formed bone and cartilage has hindered clinical adoption, driving the continuous development of more effective constructs. To address this issue, we propose an approach centred on a protein-modified stratified multi-phasic scaffolds. In this investigation, we developed a bottom layer composed of polydopamine-modified 3D printed poly (lactic-co-glycolic acid) (PLGA) scaffolds loaded with simvastatin, complemented by an upper layer consisting of electrospun PLGA-gelatine fibres obtained by a green strategy, e.g., using a benign solvent. Scaffolds were then coated with transforming growth factor-β1 (TGF-β1)- bovine serum albumin (BSA). The multi-phasic scaffolds exhibited a hierarchical interconnected porous microstructure with hydrophilicity characterized by a contact angle of 24° and a swelling rate of 467 % over 24 h (n = 5), contributing to <i>in-vitro</i> hydrolytic degradation under controllable degradation rates of 49 % over 4 weeks (n = 5). Scaffolds were also shown to undergo hydroxyapatite mineralization. The multi-phasic scaffolds exhibited a cytocompatible support for adhesion and proliferation (3.5-fold increase from day 2 to day 7) of sheep bone marrow mesenchymal stem cells along with alkaline phosphatase (ALP) secretion (1.4-fold increase from day 14 to day 21) and biomineralization (n = 5). Additionally, the expression of collagen type II (COL2A1) and SRY-Box transcription factor 9 (SOX9) biomarkers increased over 28 days of cultivating human chondrocytes. Similarly, osteopontin (SPP1) and collagen type I (COL1A1) biomarkers showed increased expression over a 28-day period following the culture of human osteoblasts. These findings demonstrate the enhanced osteogenic and chondrogenic performance of the multi-phasic scaffold, intensified by the synergistic influence of the TGF-β1/BSA complex, potentially augmenting growth factor bioavailability for cells. In conclusion, the hierarchical multi-phasic scaffolds introduced in this work represent a highly promising strategy for the regeneration of osteochondral defects.