Surface Functionalization of a Silica-Based Bioactive Glass with Compounds from Rosa canina Bud Extracts.

Bud extracts are a new category of vegetal products, which are used in gemmotherapy. These products are liquid preparation sources of bioactive molecules (phytochemicals) and are used in medicine as health-promoting agents. Rosa canina is a medicinal plant belonging to the family Rosaceae. The R. canina bud extracts, in particular, possess anti-inflammatory and antioxidant activities due to the presence of flavonoids and other phenolic compounds. The combination of R. canina bud extracts with biomaterials can be promising for obtaining multifunctional materials carrying both inorganic and biological properties. In this work, a protocol of functionalization has been properly designed, for the first time in the literature, in order to graft various bud extracts of R. canina to a silica-based bioactive glass (CEL2). The Folin-Ciocalteu method was used to determine the redox capacity of total polyphenols in the extracts and on functionalized solid samples. X-ray photoelectron spectroscopy analysis and fluorescence microscopy were employed to investigate the presence of phenol substances on the material surface. Bioactivity (in terms of ability of inducing hydroxyapatite precipitation) has been investigated by soaking the samples, with or without functionalization, in simulated body fluid. The presence of the polyphenols from bud extracts not only preserved glass bioactivity but even enhanced it. In particular, the solution obtained from the byproducts of primary extraction in glycerol macerate showed the best performances. Moreover, the presence and antioxidant activity of bud extract compounds on the material surface after grafting demonstrate the possibility of combining the glass inorganic bioactivity with the biomolecule-specific properties, making possible a local action at the implant site. The promising results reported in this work pave the way for the realization of new multifunctional materials with a green approach.

Controlling porous titanium/soft tissue interactions with an innovative surface chemical treatment: Responses of macrophages and fibroblasts.

In order to create a stable interface with the host tissue, porous implants are widely used to ensure the in-growth of the cells and the colonization of the implant. An ideal porous implant should have a 3D architecture that enables fast migration of incoming cells while not inducing a significant pro-inflammatory response by the immune cells. Moreover, in patients where the healing is impeded (patients with co-morbidities and metabolic diseases), porosity by itself is not enough for fast colonization, and the surface properties of the implant should also be controlled. In this study, we present a controlled oxidation-based surface treatment of microbead-based porous titanium implants which not only increases the colonization by connective tissue cells but also decreases the macrophage attachment. The treatment created a nanotextured surface on the implants with an acidic shift of isoelectric point (from 4.09 to 3.09) without endangering implant's mechanical integrity. The attachment and metabolic activity of activated macrophages were significantly lower on treated surfaces with an increase in the secretion of anti-inflammatory IL-1RA and a decrease in pro-fibrotic CCL-18. Human fibroblasts proliferated faster on the treated surfaces over 14 days with near complete colonization of the whole thickness of the implant with an accompanying an increase in the secretion of TGF-beta. The surface treated samples demonstrated partial filling of the entire pores. We demonstrated that the use of nanoscale surface treatments that can be applied to the whole internal surface of porous titanium implants can significantly alter both the immune response and the colonization of the implants and can be used to fine-tune and personalize implant interfaces according to patient needs.

Innovative Coatings Based On Peppermint Essential Oil on Titanium and Steel Substrates: Chemical and Mechanical Protection Ability.

A coating that was made of peppermint essential oil was obtained on different metal substrates: Ti6Al4V alloy (mechanically polished and chemically etched) and 316L stainless steel (mechanically polished and mechanically ground). The final aim is to get a multifunctional (chemical and mechanical) protection of metal surfaces in contact with water media. The coatings were characterized by means of fluorescence microscopy, contact angle measurements, and Fourier Transformed Infrared spectroscopy (FTIR) spectroscopy. The chemical stability of the coatings was tested by means of soaking in water for different times (up to seven days) and washing with different alkaline or acidic solutions. The mechanical adhesion of the coating was tested by tape adhesion test (before and after soaking) and scratch tests to verify whether it has protection ability with respect to the metal substrate. All of the performed characterizations show that the coatings are chemically stable on all of the substrates and are nor dissolved or removed by water during soaking or by alkaline solutions during washing. The adhesion is high and classified as 4B or 5B (on the chemically etched or mechanically ground substrates) according to ASTM D3359-97, depending on the substrate roughness, both before and after soaking. In the case of scratch test (up to 10 N), the coating is not removed and it has a protection action that is able to avoid the surface damage, even if the substrate has a plastic deformation.

Cytocompatible and Anti-bacterial Adhesion Nanotextured Titanium Oxide Layer on Titanium Surfaces for Dental and Orthopedic Implants.

It is widely recognized that surface nanotextures applied on a biomaterial can affect wettability, protein absorption and cellular and/or bacterial adhesion; accordingly, they are nowadays of great interest to promote fast osseointegration and to maintain physiological healing around biomedical implants. In order to be suitable for clinical applications, surface nanotextures must be not only safe and effective, but also, they should be produced through industrial processes scalable to real devices with sustainable processes and costs: this is often a barrier to the market entry. Based on these premises, a chemical surface treatment designed for titanium and its alloys able to produce an oxide layer with a peculiar sponge like nanotexture coupled with high density of hydroxyl group is here presented. The modified Ti-based surfaces previously showed inorganic bioactivity intended as the ability to induce apatite precipitation in simulated body fluid. Physicochemical properties and morphology of the obtained layers have been characterized by means of FESEM, XPS, and Zeta-potential. Biological response to osteoblasts progenitors and bacteria has been tested. The here proposed nanotextured surfaces successfully supported osteoblasts progenitors' adhesion, proliferation and extracellular matrix deposition thus demonstrating good biocompatibility. Moreover, the nanotexture was able to significantly reduce bacteria surface colonization when the orthopedic and the periodontal pathogens Staphylococcus aureus and Aggregatibacter actinomycetemcomitans strains were applied for a short time. Finally, the applicability of the proposed surface treatment to real biomedical devices (a 3D acetabular cup, a dental screw and a micro-sphered laryngeal implant) has been here demonstrated.

Green Tea Polyphenols Coupled with a Bioactive Titanium Alloy Surface: In Vitro Characterization of Osteoinductive Behavior through a KUSA A1 Cell Study.

A chemically-treated titanium alloy (Ti6Al4V) surface, able to induce hydroxyapatite precipitation from body fluids (inorganic mineralization activity), was functionalized with a polyphenolic extract from green tea (tea polyphenols, TPH). Considering that green tea polyphenols have stimulating effects on bone forming cells (biological mineralization), the aim was to test their osteoinductive behavior due to co-operation of inorganic and biological mineralization on mesenchymal stem cells KUSA A1. The functionalized surfaces were characterized by using the Folin⁻Ciocalteu method and X-ray photoelectron spectroscopy to confirm the successful outcome of the functionalization process. Two cell cultures of mesenchymal stem cells, KUSA A1 were performed, with or without osteoinductive factors. The cells and surfaces were characterized for monitoring cell viability and hydroxyapatite production: Fourier Transform Infrared Spectroscopy and Raman spectroscopy analyses showed deposition of hydroxyapatite and collagen due to the cell activity, highlighting differentiation of KUSA A1 into osteoblasts. A higher production of extracellular matrix was highlighted on the functionalized samples by laser microscope and the fluorescence images showed higher viability of cells and greater presence of osteocalcin in these samples. These results highlight the ability of polyphenols to improve cell differentiation and to stimulate biological mineralization, showing that surface functionalization of metal implants could be a promising way to improve osteointegrability.

Zeta Potential Measurements on Solid Surfaces for in Vitro Biomaterials Testing: Surface Charge, Reactivity Upon Contact With Fluids and Protein Absorption.

Surface properties of biomaterials (e.g., roughness, chemical composition, charge, wettability, and hydroxylation degree) are key features to understand and control the complex interface phenomena that happens upon contact with physiological fluids. Numerous physico-chemical techniques can be used in order to investigate in depth these crucial material features. Among them, zeta potential measurements are widely used for the characterization of colloidal suspensions, but actually poorly explored in the study of solid surfaces, even if they can give significant information about surface charge in function of pH and indirectly about surface functional groups and reactivity. The aim of the present research is application of zeta potential measurements of solid surfaces for the in vitro testing of biomaterials. In particular, bare and surface modified Ti6Al4V samples have been compared in order to evaluate their isoelectric points (IEPs), surface charge at physiological pH, in vitro bioactivity [in simulated body fluid (SBF)] and protein absorption. Zeta potential titration was demonstrated as a suitable technique for the surface characterization of surface treated Ti6Al4V substrates. Significant shift of the isoelectric point was recorded after a chemical surface treatment (because of the exposition of hydroxyl groups), SBF soaking (because of apatite precipitation IEP moves close to apatite one) and protein absorption (IEP moves close to protein ones). Moreover, the shape of the curve gives information about exposed functional groups (e.g., a plateau in the basic range appears due to the exposition of acidic OH groups and in the acidic range due to exposition of basic NH2 groups).