Characterization and bacterial anti-adherent effect on modified PMMA denture acrylic resin containing platinum nanoparticles

Abstract

Purpose: This study characterized the synthesis of a modified PMMA (Polymethyl methacrylate) denture acrylic loading platinum nanoparticles (PtN) and assessed its bacterial inhibitory efficacy to produce novel antimicrobial denture base material.

Materials and methods: Polymerized PMMA denture acrylic disc (20 mm × 2 mm) specimens containing 0 (control), 10, 50, 100 and 200 mg/L of PtN were fabricated respectively. The obtained platinum-PMMA nanocomposite (PtNC) was characterized by TEM (transmission electron microscopy), SEM/EDX (scanning electron microscope/energy dispersive X-ray spectroscopy), thermogravimetric and atomic absorption spectrophotometer analysis. In antimicrobial assay, specimens were placed on the cell culture plate, and 100 µL of microbial suspensions of S. mutans (Streptococcus mutans) and S. sobrinus (Streptococcus sobrinus) were inoculated then incubated at 37℃ for 24 hours. The bacterial attachment was tested by FACS (fluorescence-activated cell sorting) analysis after staining with fluorescent probe.

Results: PtN were successfully loaded and uniformly immobilized into PMMA denture acrylic with a proper thermal stability and similar surface morphology as compared to control. PtNC expressed significant bacterial anti-adherent effect rather than bactericidal effect above 50 mg/L PtN loaded when compared to pristine PMMA (P=.01) with no or extremely small amounts of Pt ion eluted.

Conclusion: This is the first report on the synthesis and its antibacterial activity of Pt-PMMA nanocomposite. PMMA denture acrylic loading PtN could be a possible intrinsic antimicrobial denture material with proper mechanical characteristics, meeting those specified for denture bases. For clinical application, future studies including biocompatibility, color stability and warranting the long-term effect were still required.

Keywords: Anti-adherent effect; Denture acrylic resin; Nanocomposite; Platinum nanoparticles.

Fig. 1

TEM micrograph of PtN prepared in this study. PtN are shown as spherically shaped particles measuring 3-5 nm in diameter.

Fig. 2

The SEM/EDX pattern of PtNC electrode. The spectrum shows the characteristic peaks of Pt representing successful loading of PtN into PMMA. Unassigned peaks originate from polymer or external contaminants.

Fig. 3

SEM image of 200 mg/L PtNC (A) reveals similar surface texture with slightly increasing surface cracking and blistering as compared to control (B)(×50).

Fig. 4

In comparative TG-DSC analysis, PtNC showed stable copolymerization phase and thermal property regardless of PtN added. As compared to control, PtNC (200 mg/L) expressed closely overlapped TG curves with that of control at weight loss temperature ranged from 350℃ to 400℃ (A). In DSC thermogram ranging from 30℃ to 600℃, the melting point of PtNC (389.2℃) is slightly higher to that of control (384.7℃), demonstrating improved thermal property (B).

Fig. 5

Microscopic image (×500) of fluorescent antibody-stained attached S. mutans with live/dead staining for adherent cell counting. Live (A: control, B: 200 mg/L PtNC) and dead (C: control, D: 200 mg/L PtNC) bacteria are expressed as green versus red stain (dots).

Fig. 6

Anti-adherent effect of PtNC agaisnst viable streptococci. As compared with control, PtNC above 50 mg/L of PtN loaded significantly reduced bacterial adhesion and there were no statistical differences between S. mutans and S. sobrinus (P=.01).