Coating of Titanium with Polyelectrolyte Multilayer Films Accelerates Bone Formation

Objective: The aim of this study was to fabricated poly(4-styrenesulfonic acid-co-maleic acid) sodium salt (PSS-co-MA)  polyelectrolyte multilayer (PEM) films on the titanium and examined the osteoblast responses both in vitro and in vivo.

Methods: PEM films were constructed by forming 9 layers of poly(diallyldimethylammonium chloride) (PDADMAC) and poly(sodium 4-styrene sulfonate) (PSS) with a stop layer of PSS-co-MA resulting in generated {(PDADMAC/PSS)₄/PDADMAC}PSS-co-MA PEM films on grade 2 titanium disks and titanium pins (All chemicals were obtained from Sigma-Aldrich, Germany). Physical characteristics of titanium disks, such as roughness and hydrophilicity were examined using atomic force microscopy and contact angle measurement, respectively.  Gene expressions of MC3T3E1-osteoblast cells line were determined by quantitative reverse transcription polymerase chain reaction (qRT-PCR) and in vitro calcifications were judged by alizarin red-S staining.  Titanium pins were implanted into the Wistar rat femurs (n=4) and the new bone formations were studied by histomorphometric analysis. The data were test with normal distribution test, and then use t test or Mann-Whitney U test.

Results: PSS-co-MA coated titanium surface showed a better hydrophilicity, however, no change in surface roughness was observed compared to uncoated titanium disks (p<0.05).  The expressions of type I collagen were significantly increased at day-5 while the expressions of osteopontin, bone sialoprotein and osteocalcin increased at day-10 after seeded on coated titanium surfaces compared to control (p<0.05).  At day-15, more alizarin red-S staining was observed in cell cultured on PSS-co-MA coated titanium surfaces when compared to uncoated disks.  The bone-to-implant contact (BIC) around the PSS-co-MA coated titanium pins significantly increased compared to those around the uncoated pins in the rats at 2 weeks (p<0.05).

Conclusions: The surface modification of titanium by PSS-co-MA PEM films accelerates the bone formations. This technique may be a good candidate to improve surface properties of dental implant for supporting osseointegration.