Direct evidence of ZnO morphology modification via the selective adsorption of ZnO-binding peptides

Abstract

Biomolecule-mediated ZnO synthesis has great potential for the tailoring of ZnO morphology for specific application in biosensors, window materials for display and solar cells, dye-sensitized solar cells (DSSCs), biomedical materials, and photocatalysts due to its specificity and multi-functionality. In this contribution, the effect of a ZnO-binding peptide (ZnO-BP, G-12: GLHVMHKVAPPR) and its GGGC-tagged derivative (GT-16: GLHVMHKVAPPRGGGC) on the growth of ZnO crystals expressing morphologies dependent on the relative growth rates of (0001) and (10 10) planes of ZnO have been studied. The amount of peptide adsorbed was determined by a depletion method using oriented ZnO films grown by Atomic Layer Deposition (ALD), while the adsorption behavior of G-12 and GT-16 was investigated using XPS and a computational approach. Direct evidence was obtained to show that (i) both the ZnO-BP identified by phage display and its GGGC derivative (GT-16) are able to bind to ZnO and modify crystal growth in a molecule and concentration dependent fashion, (ii) plane selectivity for interaction with the (0001) versus the (10 10) crystal planes is greater for GT-16 than G-12; and (iii) specific peptide residues interact with the crystal surface albeit in the presence of charge compensating anions. To our knowledge, this is the first study to provide unambiguous and direct quantitative experimental evidence of the modification of ZnO morphology via (selective and nonselective) adsorption-growth inhibition mechanisms mediated by a ZnO-BP identified from phage display libraries.

Thermodynamic Study of Interactions Between ZnO and ZnO Binding Peptides Using Isothermal Titration Calorimetry

“…The interactions were studied in aqueous media as in the synthesis studies. 1,6,8 Further information in support of the choice of media for ITC experiments is given in S1 of supporting information (SI). ITC experiments were designed to; (i) monitor heat effects of interaction between ZnO and the ZnO-BPs and identify the driving forces of interaction, (ii) determine if alanine mutants of G-12 had different thermodynamic signatures in their adsorption process compared to the original sequence, (iii) determine if differences in adsorption characteristics could be detected for different peptides with a single crystal morphology and an individual peptide with different crystal morphologies and (iv) possibly identify a direct link between thermodynamic changes that occur at the peptide-inorganic interface and the observed peptide directed structural modifications of ZnO.…”

“…8 ZnO particles were synthesized following a method using Zn(NO3)2·6H2O and HMTA to form elongated twinned rods and a modification of the method incorporating GT-16 peptide to form lower aspect ratio ZnO twinned platelets. 1,6,8 Synthesized ZnO particles had been characterized using several techniques; scanning electron microscopy (JEOL JSM-840A SEM), Energy dispersive X-ray (EDX) analysis, X-ray diffraction (X'Pert PRO XRD), Fourier transform infrared spectroscopy (Nicolet Magna IR-750), and Thermogramietric analysis (Mettler Toledo TGA/SDTA 851e). 8 Herein, additional characterization of the ZnO particles was carried out before ITC experiments.…”

“…[15][16][17] Of specific interest, in-house studies have been carried out to understand the fundamental principles through which ZnO binding peptides (ZnO-BPs) interact with and modify ZnO growth process and morphology. 6,8,18 In a recent contribution, the mechanisms through which specific ZnO binding peptides (ZnO-BPs) interact with and modify the growth process and morphology of ZnO during solution synthesis was described. 8 The peptides used in the study were PD identified G-12 (GLHVMHKVAPPR) peptide, its derivative GT-16 (GLHVMHKVAPPR-GGGC) and alanine mutants of the G-12 peptide.…”

“…The specificity between inorganic crystal surfaces and material binding peptides and the exact mechanisms of their interaction are however not clearly understood. 3,6,14 In biomineralization processes, where minerals are produced by living organisms, it is thought that biomolecules may control mineral formation by modification of the energy barriers at the interface. 3,15 Similarly, there may be a direct link between thermodynamic changes that occur at the peptide-inorganic interface and peptide-directed structural modification of inorganic materials.…”

“…[1][2][3][4][5][6][7][8][9][10][11] Peptides have also been shown to act as stabilizers, reducing agents, catalysts or inhibitors when incorporated in solution syntheses of inorganic materials. 10,12,13 Great prospects lie in the use of material binding peptides to improve artificial material formation processes following more environmentally sustainable bioinspired methods.…”