Surface functionalization of bioactive glasses and hydroxyapatite with polyphenols from organic red grape pomace

Abstract

An extract of polyphenols was obtained from organic red grape pomace, chemically analyzed and used for functionalization of two bioactive glasses and porous hydroxyapatite. Functionalization is effective on hydroxyapatite and on the bioactive glass with higher surface reactivity with a different grafting mechanism.Grafting does not inhibit redox and radical scavenging activity of polyphenols. The grafted polyphenols make a continuous layer with an almost complete surface coverage. Polyphenols are released with different kinetics Accepted ArticleThis article is protected by copyright. All rights reserved according to the mechanism of grafting and maintain their redox activity. A homogeneous thin layer of polyphenols is still firmly grafted on both substrates after 28 days of soaking and it still maintains radical scavenging activity. The functionalized samples can be sterilized by gamma irradiation.

Polyphenols from Grape Pomace: Functionalization of Chitosan-Coated Hydroxyapatite for Modulated Swelling and Release of Polyphenols

“… 68 The spectrum indicates that calcium is not involved in the chemical bond of the polyphenols with the chitosan coating as it was when direct functionalization of HAp was performed without any coating. 25 In the case described here, the link occurs between the negative-charged polar groups of polyphenols (carboxylic and/or phenols) and the positive amide groups of the chitosan coating; substitution of TPP as a crosslinker by the polyphenols can also be supposed, as discussed later on.…”

“…In the freeze-dried polyphenols, high percentages of carbon and oxygen are detected, as expected. 25 Low amount of nitrogen and calcium can be considered as contaminants in the case of polyphenols.…”

“…The TRIS and HCl buffer pH was at 7.4. 25 , 35 , 36 The freeze-dried polyphenols were added to the aqueous solution reaching a concentration of 5 mg/mL with magnetic stirring for 1 h at room temperature. Polyphenols are photosensitive and could be damaged or degraded by exposition to light; thus, the whole procedure was carried out under dark condition.…”

Synthesis of hybrid polyphenol/hydroxyapatite nanomaterials: adsorption vs. in situ incorporation

“…For instance, antibiotics such as gentamicin or tobramycin but also polyphenols, as extracts or single molecules, have been adsorbed on hydroxyapatite nanoparticles or coatings. 36,[43][44][45][46][47][48] The adsorption of bisphosphonates, such as alendronate, tiludronate or risendronate, 24,49 on hydroxyapatite nanoparticles was described, adding osteogenic properties to the materials.…”

“…23,24 Other functional groups like carboxylic acids or phenols have also been shown to bind hydroxyapatite surfaces, 34,35 allowing for the efficient adsorption of natural and synthetic antibiotics or anti-inflammatory molecules. 25,36 Synthesis of HAp in the presence of polyphenols, such as gallic acid or tannic acid, 37,38 has also been reported but led to a partial or complete inhibition of hydroxyapatite crystallization, which was attributed either to complexation of Ca 2+ or adsorption on the surface of hydroxyapatite seeds. However, to our knowledge, these two approaches were never compared using same polyphenols at comparable concentrations and, in particular, their relative benefits in terms of hydroxyapatite formation and molecule loading were not studied so far.…”