The paper described a useful result, the impact of which could be enhanced by addressing the following points without running additional experiments.
1. While vascularization of large vessels in CAM is clear, vascularization through the scaffold (and its various degrees of enhancement with different-size SRIO particles) is not at all apparent. Any way to show it clearly, perhaps as an inset in MRI images?
2. The authors appear to argue in the Abstract and the Introduction that SPIO particles are preferable to Gd-DOTA in contrast-enhanced MRI of the vasculature because particles do not "leak" into extravascular compartment due to vascular permeability (SPIO particles provide "direct measure of vascularization" without an influence of other factors"). This point needs to be better supported by the results and the discussion.
3. The language could be made crisper. Too many adverbs, to my taste.