In the current study, we designed four cyclic peptide analogues by incorporating two cysteine residues in a BMP-2 linear knuckle epitope in such a way that the active region of the peptide could be either inside or outside the cyclic ring. Bone morphogenetic protein receptor BMPRII was immobilized on the chip surface, and the interaction of the linear and cyclic peptide analogues was studied using surface plasmon resonance (SPR). From the affinity data, the peptides with an active region inside the cyclic ring had a higher binding affinity in comparison to the other peptides. To confirm that our affinity data are in line in vitro, we studied the expression levels of RUNX2 (runt-related transcription factor) and conducted an osteogenic marker alkaline phosphatase (ALP) assay and staining. Based on the affinity data and the in vitro experiments, peptide P-05 could be a suitable candidate for osteogenesis, with higher binding affinity and increased RUNX2 and ALP expression in comparison to the linear peptides
