In the absence of other electrolytes, the isoelectric point of collagen is around 9.3. When pH approximates pI, the surface charge of collagen monomers is decreased resulting in minimized electrostatic repulsion and better fibril assembly. This is supported by our data where collagen fibrils loosely aligned at pH of 7 while they formed a dense layer of sheet at pH 9. As pH increased to 11, negatively charged collagen monomers could inhibit the nucleation of collagen fibril as well as the further attachment to Mg hydroxide layer. With the increase of incubation time to 8 h, small collagen fibrils could merge with adjacent fibrils forming thicker fibers. It is interesting to see that almost in all experiments spherical particles with different sizes were attached to collagen fibrils regardless of the diameters of collagen fibrils. The shape and size of those particles are very similar to the mineral nucleation reported by Ferreia et al. However, from the EDS elemental analysis, the particle structures are most likely magnesium compound instead of bone mineral. It is well documented that implant surface roughness alters osteoblast proliferation, differentiation, and extracellular matrix production. Mendonca et al. showed that rough surface topography can stimulate collagen biosynthesis and accumulation on titanium. Mg materials with RS have relative larger surface area that increases the chance of collagen molecules adsorption. This is probably why the amount of collagen absorbed on the RS and SR materials was significantly higher than that on materials with SS. Also, surface energy could affect collagen adsorption and structural rearrangement. It is noticeable that the amount of absorbed collagen decreased at 8 h on the materials with RS and SR. This phenomenon is most likely caused by severer pitting corrosion on rougher surface compared with smoother surface. In addition, surface roughness not only affected the amount of collagen absorbed but also the structure of the fibrils. The slightly morphological difference of collagen fibrils on Mg and AZ31 is likely caused by the presence of Zn2+ and Al3+, the AZ31 degradation products. Therefore, ion release rate, local pH change, hydrogen gas formation, surface energy and surface electrostatic properties can all affect the final fibril structure. We further studied how those materials affect cell attachment and proliferation. The better cell attachment on the materials with SS is consistent with previous studies. On AZ31 material, a lot of dead cells could be observed on the RS materials after the first day. This is most likely due to the failure of cell attachment or Staurosporine hampered cell attachment on the RS where cells could only anchor themselves at reduced area caused by the existence of the grooves and ridges. The grooves and ridges showed contact guidance effect on cell alignment. It was demonstrated before that the tip of filopodia most likely attaches to the top of the ridges. During cell migration, it would be much easier for cell to move the tip of the adhesion along the ridge than to move the tip of the adhesion perpendicular to the direction of ridges. That may be the reason why cells on the rough surface materials all aligned parallel to the direction of ridges. Cells showed similar proliferation results on AZ31 with different surface roughness indicating that surface roughness and collagen structure won’t affect cell proliferation. However, cells didn’t show similar proliferation result on pure Mg at 4th day and 7th day. Cell density significantly decreased at the Mg with RS and SR. Healthy spreading cells could hardly be found on the SS of pure Mg materials. At body temperature, melting time for human type I collagen is around several days.