Fabrication of Biocompatible Potassium Sodium Niobate Piezoelectric Ceramic as an Electroactive Implant

Abstract

The discovery of piezoelectricity in natural bone has attracted extensive research in emulating biological electricity for various tissue regeneration. Here, we carried out experiments to build biocompatible potassium sodium niobate (KNN) ceramics. Then, influence substrate surface charges on bovine serum albumin (BSA) protein adsorption and cell proliferation on KNN ceramics surfaces was investigated. KNN ceramics with piezoelectric constant of ~93 pC/N and relative density of ~93% were fabricated. The adsorption of protein on the positive surfaces (Ps) and negative surfaces (Ns) of KNN ceramics with piezoelectric constant of ~93 pC/N showed greater protein adsorption capacity than that on non-polarized surfaces (NPs). Biocompatibility of KNN ceramics was verified through cell culturing and live/dead cell staining of MC3T3. The cells experiment showed enhanced cell growth on the positive surfaces (Ps) and negative surfaces (Ns) compared to non-polarized surfaces (NPs). These results revealed that KNN ceramics had great potential to be used to understand the effect of surface potential on cells processes and would benefit future research in designing piezoelectric materials for tissue regeneration.

Keywords: biological; electroactive; implant; piezoelectric; potassium sodium niobate.

Figure 1

Particle size distribution, thermal gravimetric (TG), and differential thermal analysis (DTA) curves of the mixtures ball-milled for different time. (a) Particle size distribution of the mixtures ball-milled for 4, 8 and 16 h, respectively; (b) TG and (c) DTA curves of the mixtures ball-milled for 4, 8 and 16 h. The insert of 1,2,3,4 and 5 in Figure 1b show weight loss peaks associated with endothermic peaks of inserted 1,2,3 and 4 in Figure 1c.

Figure 2

Scanning electron microscopy (SEM) images of mixture powder calcined at different temperature from 600 to 900 °C after ball milled for 4 and 8 h, respectively. When ball-milled for 8 h under the same temperature, particle size was smaller and more uniform.

Figure 3

X-ray diffraction (XRD) patterns of raw material and mixture powder calcined at different temperature from 600 to 900 °C after ball milling for 8 h.

Figure 4

Relative density and piezoelectric constant (d₃₃) of the polarized ceramic prepared from corresponding potassium sodium niobate (KNN) powder. The relationship between relative density (a); piezoelectric constant (d₃₃) (b) and calcination temperature (from 600 to 900 °C) after ball-milled for 4 and 8 h, respectively.

Figure 5

(a) SEM image of KNN ceramic with energy-dispersive X-ray spectroscopy (EDS) results inserted; (b) XRD pattern of the KNN ceramic including the insert of detail in the 2θ from 44.2° to 47°, which were fitted to the sum of four peaks indexed as two tetragonal peaks (in red) plus two orthorhombic peaks (in blue) of the perovskite phase; the surface potential by scanning Kelvin probe microscopy (SKPM) and protein adsorption behavior on three different KNN ceramic surfaces: (c) on positive surface (Ps); (d) on negative surface (Ns) and (e) on non-polarized surface (NPs); (f) the results of bovine serum albumin (BSA) protein adsorption.

Figure 5

(a) SEM image of KNN ceramic with energy-dispersive X-ray spectroscopy (EDS) results inserted; (b) XRD pattern of the KNN ceramic including the insert of detail in the 2θ from 44.2° to 47°, which were fitted to the sum of four peaks indexed as two tetragonal peaks (in red) plus two orthorhombic peaks (in blue) of the perovskite phase; the surface potential by scanning Kelvin probe microscopy (SKPM) and protein adsorption behavior on three different KNN ceramic surfaces: (c) on positive surface (Ps); (d) on negative surface (Ns) and (e) on non-polarized surface (NPs); (f) the results of bovine serum albumin (BSA) protein adsorption.

Figure 6

Schematic drawing of the interaction among three different surfaces of KNN and the environmental species. (a) On the positive KNN, anions and negatively charged proteins are actively adsorbed, forming a protein layer; (b) On the negative KNN, cations, particularly Ca²⁺, are selectively adsorbed ,leading to the presence of positively charged ion layer, which in turn promote prot ein adsorption and proliferation cells on this surface; (c) On non-polarized KNN surface, inorganic ions, amino acids and proteins float and attach to non-polarized KNN.

Figure 7

Cell viability on the surfaces of KNN piezoelectric ceramics: Calcein AM to detect live cells, propidium iodide to detect dead cells. (a) non-polarized surfaces (NPs); (b) positive surfaces (Ps) and (c) negative surfaces (Ns); (d) Cell proliferation on NPs, Ps and Ns was determined by CCK-8 assay on days 1, 4 and 7 days. The ** indicated significant difference (p < 0.01).