Mineralization of calcium phosphate controlled by biomimetic selfassembled peptide monolayers via surface electrostatic potentials

The functions of acidic-rich domains in non-collagenous protein during biomineralization are thought to induce nucleation and control the growth of hydroxyapatite.The tripeptide Asp-Ser-Ser(DSS)repeats are the most common acidic-rich repeated unit in non-collagenous protein of dentin phosphoprotein,the functions of which have aroused extensive interests.In this study,biomimetic peptides(DSS)n(n=2 or 3)were designed and fabricated into self-assembled monolayers(SAMs)on Au(111)surface as biomimetic organic templates to regulate hydroxyapatite(HAp)mineralization in 1.5 simulated body fluid(1.5 SBF)at 37°C.The early mineralization processes and minerals deposited on the SAMs were characterized by X-ray diffraction,scanning electron microscope,and Fourier transform infrared spectroscopy analyses.The SAM-DSS9/DSS9G showed the highest capacity to induce HAp nucleation and growth,followed by SAM-DSS6/DSS6G,SAM-COOH,and SAMOH.The SAM-(DSS)n had more negative zeta potentials than SAM-COOH surface,indicating that DSS repeats contributed to the biomineralization,which not only provided strong affinity with Ca2+ions through direct electrostatic bonds,but more importantly influence surface electrostatic potentials of the assembled organic template for nucleation.