Effect of linearly polarized microwaves on nanomorphology of calcium carbonate mineralization using peptides

Abstract

Microwaves are used for diverse applications such as mobile phones, ovens, and therapy devices. However, there are few reports on the effects of microwaves on diseases other than cancer, and on physiological processes. Here, we focused on CaCO3 mineralization as a model of biomineralization and attempted to elucidate the effect of microwaves on CaCO3 mineralization using peptides. We conducted AFM, ζ potential, HPLC, ICP-AES, and relative permittivity measurements. Our findings show that microwaves alter the nanomorphology of the CaCO3 precipitate, from sphere-like particles to string-like structures. Furthermore, microwaves have little effect on the mineralization when the mineralization ability of a peptide is high, but a large effect when the precipitation ability is low. Our findings may be applicable to not only the treatment of teeth and bones but also the development of organic–inorganic nanobiomaterials. This methodology can be expanded to other molecular/atomic reactions under various microwave conditions to alter reaction activity parameters.

Development of a CaCO3 Precipitation Method Using a Peptide and Microwaves Generated by a Magnetron

“…A thermocouple thermometer (Card Logger MR5300, MR9302, CHINO Corp., Tokyo, Japan) was used to measure the temperature changes in Milli-Q water (1 mL) in a microtube upon MW irradiation from one direction at 10, 30, and 200 W or from two directions at 10 and 200 W. In the previous study, we already confirmed that the effect of MWs on the thermometer was negligible [26].…”

“…We recently reported the effect of MWs generated by a semiconductor oscillator that outputted a narrow frequency band of 2450 ± 3 MHz on CaCO 3 mineralization using peptides with different net charges. Our results showed that the nanomorphology of the CaCO 3 precipitates was dependent on the MW output (10-60 W) and the ability of the peptide to induce CaCO 3 precipitation [26]. Investigating the effects of MWs on the CaCO 3 mineralization with peptides enabled the elucidation of the molecular behavior of organic and inorganic compounds.…”

“…The effects of MWs on CaCO 3 mineralization were previously investigated using four peptides that had different net charges owing to structural modification at the C-terminal core sequence of the calcification-associated peptide (CAP-1) [15]. We showed that MWs generated from a semiconductor oscillator altered the nanomorphology of the CaCO 3 precipitates [26]. MWs barely affected the morphology of the CaCO 3 precipitates when using the peptide with high mineralization ability, whereas they significantly affected the precipitate morphology when using the peptide with low mineralization ability.…”

“…In this study, among the four peptides, we selected the peptide that exhibited the lowest precipitating ability and large MW effect (Figure 1). When the selected CaCO 3 -precipitating peptide was used at a concentration of 100 µM, the CaCO 3 precipitates showed stringlike morphology upon irradiation with 60 W of MWs generated by the semiconductor oscillator [26].…”

“…The distribution of the E-field strength was non-uniform, thus necessitating that the device measuring the E-field strength had a spatial resolution equal to or less than the microtube size. We used an optical E-field sensor that was composed of an optical waveguide and a dipole antenna, similar to that used in the previous study [26]. The E-field strength increased with the MW output (Figure S2), and the polarizing direction was vertical to the antenna major axis.…”