Abstract
Recent years have seen the dynamic development of methods for functionalizing the surface of implants using biomaterials that can mimic the physical and mechanical nature of native tissue, prevent the formation of bacterial biofilm, promote osteoconduction, and have the ability to sustain cell proliferation. One of the concepts for achieving this goal, which is presented in this work, is to functionalize the surface of NiTi shape memory alloy by an atypical glass-like nanocomposite that consists of SiO2-TiO2 with silver nanoparticles. However, determining the potential medical uses of bio(nano)coating prepared in this way requires an analysis of its surface roughness, tribology, or wettability, especially in the context of the commonly used reference coat-forming hydroxyapatite (HAp). According to our results, the surface roughness ranged between (112 ± 3) nm (Ag-SiO2)—(141 ± 5) nm (HAp), the water contact angle was in the range (74.8 ± 1.6)° (Ag-SiO2)—(70.6 ± 1.2)° (HAp), while the surface free energy was in the range of 45.4 mJ/m2 (Ag-SiO2)—46.8 mJ/m2 (HAp). The adhesive force and friction coefficient were determined to be 1.04 (Ag-SiO2)—1.14 (HAp) and 0.247 ± 0.012 (Ag-SiO2) and 0.397 ± 0.034 (HAp), respectively. The chemical data showed that the release of the metal, mainly Ni from the covered NiTi substrate or Ag from Ag-SiO2 coating had a negligible effect. It was revealed that the NiTi alloy that was coated with Ag-SiO2 did not favor the formation of E. coli or S. aureus biofilm compared to the HAp-coated alloy. Moreover, both approaches to surface functionalization indicated good viability of the normal human dermal fibroblast and osteoblast cells and confirmed the high osteoconductive features of the biomaterial. The similarities of both types of coat-forming materials indicate an excellent potential of the silver-silica composite as a new material for the functionalization of the surface of a biomaterial and the development of a new type of functionalized implants.
Highlights
Nickel-titanium alloys (NiTi), which have a near-equiatomic chemical composition, have the superelasticity and shape memory effects that are associated with a reversible phase transformation
The deposition and post-heat-treatment parameters of a silver-silica coating on the surface of a NiTi alloy and its impact on the morphology and structure were previously studied using X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) that was equipped with an energy dispersive spectrometer (EDS) [62]
As a result of the structural analysis, it was determined that the temperature led to the formation of a complex structure consisting of SiO2 -TiO2 glass with silver that stabilized the network of such a structure
Summary
Nickel-titanium alloys (NiTi), which have a near-equiatomic chemical composition, have the superelasticity and shape memory effects that are associated with a reversible phase transformation These features result in NiTi alloys being widely used in many biomedical applications [1,2]. NiTi alloys are commonly used as maxillofacial and dental implants, lumbar vertebral replacements, joint replacements, bone plates, bone tissue engineering, spine fracture fixation, anchorage, and repair [6,7,8,9,10,11] Their long-term use in vivo revealed some disadvantages of NiTi alloys, which causes the release of toxic nickel ions into the body, and limits the full acceptance of an implant by the organism [12,13,14]. This is one of the most problematic issues that has to be resolved in order to develop a durable implant material
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