Deposition of Antioxidant and Cytocompatible Caffeic Acid-Based Thin Films onto Ti6Al4V Alloys through Hexamethylenediamine-Mediated Crosslinking

Abstract

A promising approach for advanced bone implants is the deposition on titanium surfaces of organic thin films with improved therapeutic performances. Herein, we reported the efficient dip-coating deposition of caffeic acid (CA)-based films on both polished and chemically pre-treated Ti6Al4V alloys by exploiting hexamethylenediamine (HMDA) crosslinking ability. The formation of benzacridine systems, resulting from the interaction of CA with the amino groups of HMDA, as reported in previous studies, was suggested by the yellow/green color of the coatings. The coated surfaces were characterized by means of the Folin–Ciocalteu method, fluorescence microscopy, water contact angle measurements, X-ray photoelectron spectroscopy (XPS), zeta-potential measurements, and Fourier transform infrared spectroscopy, confirming the presence of a uniform coating on the titanium surfaces. The optimal mechanical adhesion of the coating, especially on the chemically pre-treated substrate, was also demonstrated by the tape adhesion test. Interestingly, both films exhibited marked antioxidant properties (2,2-diphenyl-1-picrylhydrazyl and ferric reducing antioxidant power assays) that persisted over time and were not lost even after prolonged storage of the material. The feature of the coatings in terms of the exposed groups (XPS and zeta potential titration evidence) was apparently dependent on the surface pre-treatment of the titanium substrate. Cytocompatibility, scavenger antioxidant activity, and antibacterial properties of the developed coatings were evaluated. The most promising results were obtained in the case of the chemically pre-treated CA/HMDA-based coated surface that showed good cytocompatibility and high reactive oxygen species’ scavenging ability, preventing their intracellular accumulation under pro-inflammatory conditions; moreover, an anti-fouling effect preventing the formation of 3D biofilm-like bacterial aggregates was observed by scanning electron microscopy. These results open new perspectives for the development of innovative titanium surfaces with thin coatings from naturally occurring phenols for bone contact implants.

Development, Analytical Characterization, and Bioactivity Evaluation of Boswellia serrata Extract-Layered Double Hydroxide Hybrid Composites

“…A specific role of boswellic acids has been also clarified regarding their antioxidant properties, as they are involved in the inhibition of the pro-inflammatory NF-κB activator and in the modulation of other relevant inflammatory molecular targets, such as AP-1 and β-catenin, as well as enzymes like COX-2 and pro-inflammatory cytokines (TNF-α, IL-1β) [ 45 ]. Accordingly, a pro-inflammatory condition was induced by oxidative stress chemically generated by hydrogen peroxide addition into the culture medium; afterwards, supernatants were collected and used to cultivate cells, as previously reported by the authors [ 46 , 47 , 48 ]. In such a pro-inflammatory scenario, the well-known scavenger ability of the boswellic acids [ 49 , 50 ] was expected to significantly reduce the amount of the cytotoxic oxygen- and nitrogen-derived (ROS) active species, thus protecting cells from intracellular accumulation.…”

“…The composites’ ability to act as antioxidants via scavenging activity was evaluated regarding their ability to protect cells from the intracellular accumulation of toxic active species in a pro-inflammatory scenario. Accordingly, oxidative stress was chemically induced by adding hydrogen peroxide (H 2 O 2 , 3 h/day, 300 μM) into the medium to generate oxygen-derived toxic active species (ROS), as previously shown by the authors [ 46 , 47 , 48 ]. Accordingly, H 2 O 2 was added to the medium in the presence of the composites and agitated (100 rpm) at room temperature for 3 days.…”

PHYTOCHEMICAL SCRINING AND DETERMINATION OF SECONDARY METABOLITICAL CAPACITY OF BUTTERFLY LEAVES (Bauhinia Purpurea L) AS A GUIDE FOR WOUND HEALING IN WOMEN AFTER PREGNANCY

“…The Folin-Ciocelteau technique, which is based on the principles of reduction and oxidation, is used to determine the total phenol concentration (Tursiman, 2013). When phenol group chemicals react with the Folin-Ciocelteau reagent, a yellow hue results; when 1% NaOH is added, a blue color results (Alfieri et al, 2023). The proton dissociation of phenolic compounds into phenolic ions causes phenolic group compounds to react with the Folin-Ciocelteau reagent in an alkaline environment.…”

Multifunctional coatings hinging on the catechol/amine interplay

“…Relevant examples include the use of caffeic acid and HMDA to coat a variety of substrates including titanium surfaces for bone implants. [117][118][119] UV-Vis, mass spectrometric, and NMR analysis indicated covalent incorporation of the amine during caffeic acid polymerization to produce adhesive trioxybenzacridinium scaffolds (Figure 4D). [119] Finally, a series of papers reported also the possibility to implement tunable and robust coatings on different substrates by using polymeric systems functionalized with both catechol and amine moieties in different proportions.…”

“…Caffeic acid is another plant‐derived catecholic compound whose interesting biological and functional properties have been transferred to different substrates by exploitation of the catechol‐amine interplay. Relevant examples include the use of caffeic acid and HMDA to coat a variety of substrates including titanium surfaces for bone implants [117‐119] . UV‐Vis, mass spectrometric, and NMR analysis indicated covalent incorporation of the amine during caffeic acid polymerization to produce adhesive trioxybenzacridinium scaffolds (Figure 4D).…”