Functionalization with Polyphenols of a Nano-Textured Ti Surface through a High–Amino Acid Medium: A Chemical–Physical and Biological Characterization

Abstract

The study aimed to identify an effective mechanism of adsorption of polyphenols on a nano-textured Ti surface and to evaluate the osteogenic differentiation on it. The source of polyphenols was a natural extract from red grape pomace. A chemical etching was used to form an oxide layer with a nanoscale texture on Ti; this layer is hydrophilic, but without hydroxyl groups with high acidic–basic chemical reactivity. The samples were characterized by electron and fluorescence microscopies, UV–Vis spectroscopy, contact angle measurements, zeta potential titration curves, and Folin–Ciocâlteu test. The presence of an adsorbed layer of polyphenols on the functionalized surface, maintaining redox ability, was confirmed by several tests. Consistent with the surface features, the adsorption was maximized by dissolving the extract in a high–amino acid medium, with respect to an inorganic solution, exploiting the high affinity of amino acids for polyphenols and for porous titanium surfaces. The osteogenic differentiation was assessed on an osteoblastic cell line by immunofluorescence, cell viability, expression of key osteoblast markers, and extracellular matrix mineralization. The surfaces functionalized with the extract diluted in the range 1 × 10−5–1 mg/mL resulted in having a greater osteogenic activity for the highest concentration, with lower values of cell viability; higher expression of alkaline phosphatase, bone sialoprotein, and collagen; and lower levels of osteopontin. In conclusion, the functionalization of a nano-textured Ti surface with polyphenols can potentially favor the osteogenic activity of osseointegrated implants.

Influence of a Physiologically Formed Blood Clot on Pre-Osteoblastic Cells Grown on a BMP-7-Coated Nanoporous Titanium Surface

“…Epifluorescence and SEM imaging show that structurally, the clot consists of a three-dimensional fibrin network embedding variable amounts of platelets, leukocytes, and erythrocytes, distributed inhomogeneously throughout the surface. Although the combination of nanotopography and hydrophilicity (two surface characteristics of Nano-Ti) [ 20 , 21 ] might contribute to pronounced blood coagulation [ 29 ], it has been shown that implant surfaces structured at the micro-scale are more efficient at retaining the fibrin clot, an event that is crucial for bone repair to occur at the tissue–implant interface [ 30 ]. Therefore, considering the only occasional occurrence of microtopographic features on the Nano-Ti surface (not shown) and the inhomogeneity of the blood clot on it, it may be more appropriate to hierarchically structure the Ti surface at the micro- and nanoscale [ 31 ], or to even functionalize it with a molecule that could contribute to the formation of a more homogenous blood clot/fibrin clot in vivo.…”

“…To obtain Nano-Ti, commercially pure grade 2 Ti discs (Realum, São Paulo, Brazil), modified to exhibit a hollowed surface ( Figure S1 ), were cleaned by sonication and etched in a solution consisting of equal volumes of concentrated 30% H 2 O 2 and H 2 SO 4 (95–97%) for 4 h (10 mL/disc) at room temperature (RT) [ 12 , 20 ]. Then, they were rinsed in distilled water, air dried, and autoclaved.…”

“…The present study goes further by including the formation of a physiological blood clot using the surgical approach proposed elsewhere [ 18 ] and adapted to our conditions to ensure the implant placement in a mouse dorsal dermal tissue model. The implant Ti discs were chemically treated with a mixture of sulfuric acid (H 2 SO 4 ) and hydrogen peroxide (H 2 O 2 ) to create a highly hydrophilic, biomimetic TiO 2 nanotopography [ 19 ] supportive of (i) functionalization with organic molecules by physisorption [ 20 ] and (ii) osteogenic differentiation [ 12 , 21 ]. The average roughness of Nano-Ti has been reported to be on the order of 9 nm, with nanopore depths ranging from 5 to 25 nm [ 22 , 23 ].…”

Anticorrosion and Antimicrobial Tannic Acid-Functionalized Ti-Metallic Glass Ribbons for Dental Abutment

“…The here-reported surface modification is a functionalization that produces the grafting of a thin (molecular) layer of TA without any modification of the surface roughness and morphology, as previously observed by the authors on different titanium substrates. 31,32 3.3. Compositional and Chemical State Analysis.…”

“…Chemisorption allows a controlled and pH-dependent release that is beneficial for targeted effects. 31 In the present study, we used tannic acid polyphenols from a natural extract for functionalization, as they possess multifunctional properties, 32 for example, antibacterial, anti-inflammatory, antitumor, antiviral, and cytocompatible characterizations that were proved thanks to the presence of high amounts of phenolic compounds and pyrogallol groups. 33 Therefore, there has been increased interest in the implementation of tannic acid to chemically modify the surface of materials in terms of their application as implant biomaterials.…”