Abstract
The inhibition of the corrosion of metal implants is still a challenge. This study aimed to increase the corrosion resistance of Ti6Al7Nb alloy implants through surface modification, including grinding, sandblasting, and anodic oxidation followed by the deposition of a polymer coating. The aim of the work was to determine the influence of biodegradable polymer coatings on the physico-chemical properties of a Ti6Al7Nb alloy used for short-term implants. Biodegradable coatings prepared from poly(glycolide-caprolactone) (P(GCap)), poly(glycolide ε-caprolactone-lactide) (P(GCapL)), and poly(lactide-glycolide) (PLGA) were applied in the studies. The dip-coating method with three cycles of dipping was applied. Corrosion resistance was assessed on the basis of potentiodynamic studies. The studies were carried out on samples after 30, 60, and 90 days of exposure to Ringer’s solution. Surface topography, wettability, and cytotoxicity studies were also carried out. The degradation process of the base material was evaluated on the basis of the mass density of the metal ions released to the solution. The results indicated the influence of the coating type on corrosion resistance. In addition, a beneficial effect of the polymer coating on the reduction of the density of the released metal ions was found, as compared to the samples without polymer coatings. The obtained results provide basic knowledge for the development of polymer coatings enriched with an active substance. The presence of ciprofloxacin in the coating did not reduce the corrosion resistance of the metal substrate. Moreover, the cytotoxicity test using the extract dilution method demonstrated that the implants’ coatings are promising for further in vitro and in vivo studies.
Highlights
In the last few decades, dynamic research on a variety of polymer biomaterials has been observed.This was mainly caused by the satisfactory biocompatibility of biopolymers and their dedicated functionality
The determined parameters of the polymer coating roughness obtained after one dip not exposed to Ringer’s solution (0 month—NoE) regardless of the type of polymer—PLGA, P(GCap), or P(GCapL)—were slightly lower than the roughness of the metal substrate (Sa = 0.47 ± 0.02 m); see Table 1
In the case of the PLGA and P(GCap) coatings obtained as a result three times immersion in PLGA, P(GCap), and P(GCapL) at the initial state (NoE) and after of a single immersion and P(GCapL) obtained as a result of triple immersions was prolonged exposure to Ringer's solution are summarized in Table 2 and Figure 3
Summary
In the last few decades, dynamic research on a variety of polymer biomaterials has been observed.This was mainly caused by the satisfactory biocompatibility of biopolymers and their dedicated functionality. The basic limitation of the use of biodegradable polymers relates to the mechanical properties that change over time This feature may be disadvantageous in some applications, e.g., orthopedic implants. Despite the continuous development of material science and engineering, which is fundamental for the development of a wide range of biomaterials, metal materials are still the primary group Their biological performance and universality are the result of long-term clinical outcomes and relatively low manufacturing and use costs. Based on recent research, it is needed to be mentioned that, despite being the first choice material in orthopedic applications, the alloy often causes allergic reactions due to the presence of vanadium, aluminum, and titanium [9,10,11]. The basic direction of current research on improving the biocompatibility of metal biomaterials, including titanium alloys, is to modify their surface layers [10,12]. Interesting results have been obtained by applying SiO2 or TiO2 coatings produced by the sol–gel and atomic layer deposition (ALD) methods [1,9,14,15,16,17,18]
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