Titanium Functionalized with Polylysine Homopolymers: In Vitro Enhancement of Cells Growth

Abstract

In oral implantology, the success and persistence of dental implants over time are guaranteed by the bone formation around the implant fixture and by the integrity of the peri-implant mucosa seal, which adheres to the abutment and becomes a barrier that hinders bacterial penetration and colonization close to the outer parts of the implant. Research is constantly engaged in looking for substances to coat the titanium surface that guarantees the formation and persistence of the peri-implant bone, as well as the integrity of the mucous perimeter surrounding the implant crown. The present study aimed to evaluate in vitro the effects of a titanium surface coated with polylysine homopolymers on the cell growth of dental pulp stem cells and keratinocytes to establish the potential clinical application. The results reported an increase in cell growth for both cellular types cultured with polylysine-coated titanium compared to cultures without titanium and those without coating. These preliminary data suggest the usefulness of polylysine coating not only for enhancing osteoinduction but also to speed the post-surgery mucosal healings, guarantee appropriate peri-implant epithelial seals, and protect the fixture against bacterial penetration, which is responsible for compromising the implant survival.

Keywords: biomaterials; cell growth; dental implants; epithelial growth; implantology; polylysine; titanium.

Figure 1

Schematic representation of a dental implant (a) and the oral structures (peri-implant mucosa and peri-implant bone) surrounding the fixture (b), surgically inserted in the bone. Original figures made by D.M. with SOLIDWORKS ^® (CSWP-MBD Version, 2021, SolidWorks, Dassault systems, Waltham, MA, USA).

Figure 2

On top, the machined clean titanium plate at SEM. FOV: 134 µm, Mode: 15 kV—Point, Detector: BSD Full. On bottom, the chemical composition analysis of the titanium surface, in spot 1, pointed by a cross in the figure.

Figure 3

Schematic representation of the experiments. (a) hDPSCs cultured alone, on titanium plates, and on titanium plates coated with poly-L-lyisine. (b) HaCaT cells cultured alone, on titanium plates, and on titanium plates coated with poly-L-lyisine.

Figure 4

Cell growth analyses. Although hDPSCs cultured in standard condition and on titanium with and without poly-L-lysine showed the same trend in growth, in the culture with titanium coated with poly-L-liysine, the cell growth was higher than the hDPSCs alone and hDPSCs with only titanium. ** p < 0.01, *** p < 0.001 compared to the hDPSCs.

Figure 5

MTT evaluation. Titanium did not show cytotoxicity, and the proliferation of cells seeded on titanium was similar to those of cultured in standard condition, but in titanium coated with poly-L-liysine, cell proliferation was higher at 24, 48, and 72 h. *** p < 0.001 compared to the hDPSCs.

Figure 6

(a) HaCat cells culture on the titanium plate coated with poly-L-lysine. (b) After a further 48 h, the titanium plate with the adherent HaCaT cells was placed in a new well with a fresh medium, where vital and growing cells were appreciated adhering on the bottom of the well, as shown in figure (b) (optical microscopy, original magnification ×10).