The responses to surface wettability gradients induced by chitosan nanofilms on microtextured titanium mediated by specific integrin receptors

Abstract

Microtexture and chemistry of implant surfaces are important variables for modulating cellular responses. Surface chemistry and wettability are connected directly. While each of these surface properties can influence cell response, it is difficult to decouple their specific contributions. To address this problem, the aims of this study were to develop a surface wettability gradient with a specific chemistry without altering micron scale roughness and to investigate the role of surface wettability on osteoblast response. Microtextured sandblasted/acid-etched (SLA, Sa = 3.1 μm) titanium disks were treated with oxygen plasma to increase reactive oxygen density on the surface. At 0, 2, 6, 10, and 24 h after removing them from the plasma, the surfaces were coated with chitosan for 30 min, rinsed and dried. Modified SLA surfaces are denoted as SLA/h in air prior to coating. Surface characterization demonstrated that this process yielded differing wettability (SLA0 < SLA2 < SLA10 < SLA24) without modifying the micron scale features of the surface. Cell number was reduced in a wettability-dependent manner, except for the most water-wettable surface, SLA24. There was no difference in alkaline phosphatase activity with differing wettability. Increased wettability yielded increased osteocalcin and osteoprotegerin production, except on the SLA24 surfaces. mRNA for integrins α1, α2, α5, β1, and β3 was sensitive to surface wettability. However, surface wettability did not affect mRNA levels for integrin α3. Silencing β1 increased cell number with reduced osteocalcin and osteoprotegerin in a wettability-dependent manner. Surface wettability as a primary regulator enhanced osteoblast differentiation, but integrin expression and silencing β1 results indicate that surface wettability regulates osteoblast through differential integrin expression profiles than microtexture does. The results may indicate that both microtexture and wettability with a specific chemistry have important regulatory effects on osseointegration. Each property had different effects, which were mediated by different integrin receptors.

Bioactive treatment promotes osteoblast differentiation on titanium materials fabricated by selective laser melting technology

“…However, it is usually difficult to evaluate the specific contribution of wettability because wettability is strongly affected by the surface roughness and chemistry. Recent attempts to modify wettability without changing the surface microstructure and chemistry have revealed that hydrophilic surfaces modulated the expression profile of integrin subunits and enhanced osteogenic cell differentiation 50,51) . The hypothetical mechanism of the effects of hydrophilic surfaces on cell attachment and subsequent reactions is that the hydrophilicity influences the protein absorption to the material surface and prevents the entrapment of air bubbles within the surface architecture, which could interfere with protein absorption and materialcell interaction 49) .…”

Development of hybrid coatings for osseointegration improvement of metal dental implants

“…In vitro studies reveal that metal ions released from the electrochemical corrosion, even detected at sublethal doses, can affect the osteoblasts and osteoclasts differentiation 27,29,28 . Metal implants can degrade through corrosion and wear process, nevertheless, synthetic hardware as polyethylene degrades only through wear process 28 .…”

“…According , the selected experimental times were 1 and 2 weeks since previous works showed that in vivo experiments for up to 8 weeks exhibited significant modifications at implantations on this periods 28 .…”

“…EXAKT ® thin section cutting technology allows the cutting of samples up to 100 μm thick without affecting the composition, surface or structure during samples' processing, which explains the choise of that methodology for preparing the in vivo extracted samples for histological studies. 30 Dye processing of the samples is described elsewhere 28 . Briefly, the cut samples were rehydrated with decreasing alcohol content on several alcohol-water dissolutions.…”

“…implants, several studies demonstrate that surface stabilization is not always achieved and also the presence of some elements as Ca, P and S can affect the chemical composition of protective oxide films of metallic prosthesis 27,28 . In vitro studies reveal that metal ions released from the electrochemical corrosion, even detected at sublethal doses, can affect the osteoblasts and osteoclasts differentiation 27,29,28 .…”