Flexural strength, biocompatibility, and antimicrobial activity of a polymethyl methacrylate denture resin enhanced with graphene and silver nanoparticles
The study evaluates the effect of adding graphene-Ag nanoparticles (G-AgNp) to a PMMA auto-polymerizing resin, with focus on antibacterial activity, cytotoxicity, monomer release, and mechanical properties.
Materials and methods
Auto-polymerizing acrylic resin (M) was loaded with 1 wt% G-AgNp (P1) and 2 wt% G-AgNp (P2). Methyl methacrylate monomer release (MMA) was measured after immersion of the samples in chloroform and cell medium respectively. Cell viability was assessed on dysplastic oral keratinocytes (DOK) and dental pulp stem cells. Oxidative stress and inflammatory response following exposure of dysplastic oral keratinocytes to the experimental resins was evaluated. Antibacterial activity against Staphylococcus aureus, Streptococcus mutans and Escherichia coli and also flexural strength of the resins were assessed.
Residual monomer: For samples immersed in chloroform, MMA concentration reached high levels, 10.27 μg/g for sample P1; MMA increased at higher G-AgNp loading; 0.63 μg/g MMA was found in medium for P1, and less for sample P2. Cell viability: Both cell lines displayed a viability decrease, but remained above 75%, compared to controls, when exposed to undiluted samples. Inflammation: proinflammatory molecule TNF-α decreased when DOK cultures were exposed to G-AgNp samples. MDA levels indicated increased oxidative stress damage in cells treated with PMMA, confirmed by the antioxidant mechanism activation, while samples containing G-AgNp induced an antioxidant effect. All tested samples showed antibacterial properties against Gram-positive bacteria. Samples containing G-AgNp also exhibited bactericide action on E. coli. Mechanical properties: both samples containing G-AgNp improved flexural strength compared to the sample resin, measured through elastic strength parameters.
PMMA resin loaded with G-AgNp presents promising antibacterial activity associated with minimal toxicity to human cells, in vitro, as well as improved flexural properties.
These encouraging results obtained in vitro support further in vivo investigation, to thoroughly check whether the PMMA loaded with graphene-silver nanoparticles constitute an improvement over current denture materials.
KeywordsPMMA resin Graphene Silver nanoparticles Antibacterial action Biocompatibility
All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Cecilia Bacali, Ioana Baldea, Marioara Moldovan, Rahela Carpa and Diana Elena Olteanu. The first draft of the manuscript was written by Cecilia Bacali, Ioana Baldea, Marioara Moldovan and Rahela Carpa. All authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.
The work was supported by the University of Medicine and Pharmacy “Iuliu Hatieganu” Cluj-Napoca, Romania, grant number PCD 7690/76/15.04.2016.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
This article does not contain any studies with human participants or animals performed by any of the authors.
For this type of study, formal consent is not required.
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