The interplay of peptide sequence and local structure in TiO2 biomineralization

Using cyclic constrained TiO2 binding peptides STB1 (CHKKPSKSC), RSTB1 (CHRRPSRSC) and linear peptide LSTB1 (AHKKPSKSA), it was shown that while affinity of the peptide to TiO2 is essential to enable TiO2 biomineralization, other factors such as biomineralization kinetics and peptide local structure need to be considered to predict biomineralization efficacy. Cyclic and linear TiO2 binding peptides show significantly different biomineralization activities. Cyclic STB1 and RSTB1 could induce TiO2 precipitation in the presence of titanium(IV)-bis-ammonium-lactato-dihydroxide (TiBALDH) precursor in water or tris buffer at pH 8. In contrast, linear LSTB1 was unable to mineralize TiO2 under the same experimental conditions despite its high affinity to TiO2 comparable with STB1 and/or RSTB1. LSTB1 being a flexible molecule could not render the stable condensation of TiBALDH precursor to form TiO2 particles. However, in the presence of phosphate buffer ions, the structure of LSTB1 is stabilized, leading to efficient condensation of TiBALDH and TiO2 particle formation. This study demonstrates that peptide-mediated TiO2 mineralization is governed by a complicated interplay of peptide sequence, local structure, kinetics and the presence of mineralizing aider such as phosphate ions.

Graphical abstractCyclic constrained TiO2 binding peptide STB1 could induce TiO2 precipitation in the presence of TiBALDH while linearized STB1 (LSTB1) alone could not under the same mineralizing conditions. However, in the presence of phosphate ions, the structure of LSTB1 is stabilized, leading to efficient condensation of TiBALDH and TiO2 particle formation.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Affinity of peptide for TiO2 is critical for TiO2 biomineralization. ► Peptide local structure and reaction kinetics mediate TiO2 mineralization efficacy. ► Rigid peptide template is essential to trigger TiO2 mineralization.