Biomimetic synthesis of titania nanoparticles induced by protamine

Abstract

Protamine, a kind of cationic protein extracted from sperm nuclei, was employed for the first time in vitro to induce the formation of a titania/protamine nanoparticle composite from a water-stable titanium precursor, titanium(IV) bis(ammonium lactato) dihydroxide (Ti-BALDH). The resulting titania/protamine nanoparticle composite was extensively characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The titania/protamine nanoparticle composite was of amorphous structure, and exhibited a different morphology from those prepared by an alkali-catalyzed approach. The catalyzing and templating function of protamine involved in the synthesis of the nanoparticle composite is discussed, and a mechanism tentatively proposed. In addition, the effects of pH and temperature on the amount and size of as-prepared titania/protamine nanoparticle composite were systematically investigated.

Preparation of Protamine–Titania Microcapsules Through Synergy Between Layer‐by‐Layer Assembly and Biomimetic Mineralization

“…The broad band at around 450-700 cm À1 could be attributed to the absorption of Ti-O-Ti, which indicated the formation of titania. [40] Furthermore, with the increase of layer number, the peaks discussed above displayed an increasing trend, further confirming the successive growth of multilayer in the LbL assembly. X-ray photoelectron spectroscopy (XPS) was conducted to investigate the surface element composition of (protamine/titania) 5 .…”

“…This clearly revealed that the titanium elements were in the oxidation state IV, corresponding to Ti 4þ (TiO 2 ). [40] These results further suggested that these microcapsules assuredly comprised of protamine and titania.…”

“…Next, the protamine layer with positive charges could adsorb the titanium precursor with negative charges, Ti-BALDH, and induce the formation of titania layer. [40] The titania layer with negative charges allowed a new cycle of protamine deposition. The above cycle was repeated, and the multilayer with defect-free structure formed.…”

“…It was reported that the presence of protamine could induce a rapid polycondensation of Ti-BALDH with the formation of titania particles and eventually a compact titania layer. [40] Therefore, the protamine layer could serve as not only the ''electrostatic glue'' for LbL assembly, but also the catalyst for the formation of titania layer. Since its pI value was about 5.5, the surface of titania layer was negatively charged at pH 7.0.…”

“…[35][36][37][38] In our previous reports, it was found that protamine could induce the formation of silica and titania nanoparticles from water-soluble precursors in a facile way. [39,40] However, only inorganic spheres or particles have been in vitro synthesized to date using biomimetic method. Thereby, it constitutes a great challenge to find a general and facile method to synthesize organic-inorganic hybrid materials with structure and performance competent to natural biomaterials.…”