Multifunctional Polyphenol Nanocoatings for Improved Tissue Integration of Dental Implants

Objectives: Flavonoids and other polyphenol-based surface coatings have recently attracted increasing interest as surface functionalisation strategies for bone-anchored dental implants due to their diverse functional properties: these coatings have been shown to possess antioxidant, anti-inflammatory, antibacterial, and antifibrotic properties. The objective of this study was to assess the antibacterial and osteogenic properties of nanocoatings formed using two different phenolic compounds, tannic acid (TA) and pyrogallol (PG).
Methods: Titanium surfaces were functionalised with TA and PG using two different coating times (2 h and 24 h). Osteogenic differentiation of human primary osteoblasts was assessed by measuring the gene expression of alkaline phosphatase (ALP) and osteocalcin using quantitative polymerase chain reaction. ALP activity and calcium content were also measured after 21 d. (n=6). Biofilm formation on the coated surfaces and antibacterial effect of phenolic compounds released from the coatings were assessed in a bacteria culture assay using bioluminescent S. epidermidis Xen43 (n=12).
Results: TA and PG formed homogeneous nanocoatings on titanium surfaces by auto-oxidation mediated polymerisation. Both coatings promoted osteogenic differentiation of osteoblasts adhered onto the sample surface, particularly on coatings formed at short deposition times resulting in thinner and more rigid phenolic coatings, which were found to increase the OC and ALP gene expression, calcium content and ALP activity in comparison to the corresponding 24 h polyphenol coatings. Neither TA nor PG coatings were shown to reduce biofilm formation on the functionalised titanium surfaces, but phenolic compounds released from the surfaces coated for 24 h reduced the growth and viability of planktonic bacteria.
Conclusions: Thinner and more rigid polyphenol nanocoatings deposited for 2 h were found to promote cell adhesion and osteogenic differentiation on titanium surfaces, while polyphenolic compounds released from coatings deposited for 24 h reduced the growth of S. epidermidis.