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Electrophoretic deposition (EPD) was used to apply bioactive multifunctional composite coatings with antibacterial substances on stainless steel AISI 316L (SS). Tetracycline hydrochloride (TCN) loaded halloysite nanotubes were co-deposited with chitosan and bioactive glass (BG) particles to produce composite coatings. SEM/EDX, XRD, and FTIR analyses were performed to characterize the composition and microstructure of coatings. The release of tetracycline hydrochloride (TCN) in phosphate buffered saline (PBS) was investigated by UV spectrometry, and measurements indicated the release of around 54% of the drug within 14 days of immersion in PBS. Furthermore, to determine that the bioactivity of coatings had not been adversely influenced, simulated body fluid (SBF) bioactivity tests were performed. The formation of hydroxyl carbonate apatite on the surface of the coatings was confirmed after 3 days. The ability of coatings to prevent bacterial growth was tested using E . coli as gram-negative and S . aureus as gram-positive bacteria. Results showed improved bactericidal effect of TCN-containing coatings compared to non-TCN loaded coatings. The corresponding amount of TCN loaded in EPD coatings supported cell viability and proliferation of MG-63 cells for up to 3 days. Fluorescence images of MG-63 cells showed evidence of cell growth in islands on the coated surface. The surface roughness of the coating loaded with halloysite nanotubes supported cell adhesion and proliferation. Additionally, the wettability value of the coatings confirmed a moderately hydrophilic surface, which is suitable for bone regenerative applications. Improved corrosion resistance compared to the pure stainless steel (SS) substrate was confirmed. The adhesion between coatings and substrates was tested by the tape test, and the result showed sufficient adhesion of the coatings to be handled without detachment. In all, the new coating system has potential for applications in orthopedics.

To address one of the serious problems associated with permanent implants, namely bacterial infections, novel organic/inorganic coatings containing zinc oxide nanoparticles (nZnO) are proposed. Coatings were obtained by electrophoretic deposition (EPD) on stainless steel 316L. Different deposition conditions namely: deposition times in the range 60–300 s and applied voltage in the range 5–30 V as well as developing a layered coating approach were studied. Antibacterial tests against gram-positive Staphylococcus aureus and gram-negative Salmonella enteric bacteria confirmed the activity of nZnO to prevent bacterial growth. Coatings composition and morphology were analyzed by thermogravimetric analysis, Fourier transform infrared spectroscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. Moreover, the corrosion resistance was analyzed by evaluation of the polarization curves in DMEM at 37 °C, and it was found that coatings containing nZnO increased the corrosion resistance compared to the bare substrate. Considering all results, the newly developed coatings represent a suitable alternative for the surface modification of metallic implants., by Joanna Karbowniczek, Luis Cordero-Arias, Sannakaisa Virtanen, Superb K. Misra, Eugenia Valsami-Jones, Lorena Tuchscherr, Bogdan Rutkowski, Kamil Górecki, Piotr Bała, Aleksandra Czyrska-Filemonowicz and A. R. Boccaccini

Novel chondroitin sulfate (CS) based coatings were produced by electrophoretic deposition (EPD). CS was used as matrix and combined with bioactive glass (BG) particles to produce a series of bioactive composite coatings with potential for orthopedic and dental applications. Furthermore multilayer systems incorporating chitosan were designed and developed to tailor coating composition, bioactivity and degradation. Solutions and suspensions based on CS were developed, and their stability analyzed by means of ζ–potential measurements. EPD conditions (concentration, potential and deposition time) were investigated and determined for CS and BG/CS coatings, as well as for a variety of multilayer systems. Coating morphology, microstructure and composition were studied using SEM, XRD, FTIR spectroscopy and TG-DTA techniques which confirmed the formation of a variety of homogeneous CS based multilayered coatings. Finally, immersion test in simulated body fluid was carried out demonstrating the bioactive behavior of some of the new systems developed after 2 days of immersion. CS containing coatings are of interest for applications where the combined effects of CS and BG can lead to enhanced tissue regeneration effects.

Two organic/inorganic composite coatings based on alginate, as organic matrix, and zinc oxide nanoparticles (n-ZnO) with and without bioactive glass (BG), as inorganic components, intended for biomedical applications, were developed by electrophoretic deposition (EPD). Different n-ZnO (1–10 g/L) and BG (1–1.5 g/L) contents were studied for a fixed alginate concentration (2 g/L). The presence of n-ZnO was confirmed to impart antibacterial properties to the coatings against gram-negative bacteria Escherichia coli, while the BG induced the formation of hydroxyapatite on coating surfaces thereby imparting bioactivity, making the coating suitable for bone replacement applications. Coating composition was analyzed by thermogravimetric analysis (TG), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS) analyses. Scanning electron microscopy (SEM) was employed to study both the surface and the cross section morphology of the coatings. Polarization curves of the coated substrates made in cell culture media at 37 °C confirmed the corrosion protection function of the novel organic/inorganic composite coatings., by Luis Cordero-Arias, S. Cabanas-Polo, O. M. Goudouri, Superb K. Misra, J. Gilabert, E. Valsami-Jones, E. Sanchez, S. Virtanen and A. R. Boccaccini

An alginate (Alg) based coating containing nanoparticles of titania (nTiO2) and bioactive glass 45S5 (nBG) was deposited on stainless steel substrates by electrophoretic deposition (EPD). The composite nTiO2-nBG/Alg coating developed for potential biomedical applications, was produced from a stable ethanol/water suspension (ζ–potential of-53±13mV) using 7V of deposition potential and 1min of deposition time as optimal conditions. Morphology and composition of the coatings were studied by FTIR, EDX, SEM and XRD, showing that all components were successfully deposited on the final coating. According to TG analysis the coatings presents a 62.4wt% of ceramic phase and 37.6wt% polymer. The coating shows corrosion protection properties compared with the bare uncoated material when analyzed via polarization curves in Dulbecco ́s MEM.

Two alginate (Alg) based composite coatings on stainless steel AISI 316L substrates, one containing titania nanoparticles (n-TiO2) and another one a mixture (50/50 wt-%) of n-TiO2 and bioactive glass (BG), intended for biomedical applications, were developed by electrophoretic deposition (EPD) from ethanol/water suspensions. Different n-TiO2 (2–10 g L−1) and BG (1–5 g L−1) contents were studied for a fixed alginate concentration (2 g L−1), and the properties of the electrophoretically obtained coatings were characterised. Coatings with high ceramic content (up to 67 vol.-%) were obtained. The presence of BG particles improves the mechanical properties of the coatings by increasing the adhesion to the substrate and also accelerates the formation of hydroxyapatite after immersion of the coatings in simulated body fluid. The electrochemical behaviour of the coated substrates, evaluated by polarisation curves in Dulbecco’s modified eagle medium at 37°C, confirmed the corrosion protection function of the novel EPD coatings. The present polymer–ceramic composite coatings belong to an emerging family of bioactive, compliant coatings that are promising for a range of biomedical applications.

Direct current (DC) and alternating current (AC) electrophoretic deposition (EPD) approaches involving different number of EPD cycles were developed for the fabrication of alginate/Bioglass® composite coatings from water-based suspensions. The high stability of the colloidal suspension was confirmed by zeta-potential assessment and the properties of coatings deposited from both DC-EPD and AC-EPD were quantitatively compared by using a range of characterization methods. The deposition yield and coating composition were determined by mass and thermogravimetric analysis. Coatings with different microstructure and thickness were observed by scanning electron microscopy. Significant differences in surface roughness and hydrophilicity (determined by water contact angle measurement) of coatings obtained by DC-EPD and AC-EPD were identified and discussed. The coating adhesion strength and corrosion resistance were evaluated by standard tape test and electrochemical method, respectively, and the experimental data showed the superior adhesion and corrosion resistance of AC-EPD coatings compared to DC-EPD coatings. In order to investigate the in vitro bioactivity, all coatings were immersed in simulated body fluid for 7 days. Results from Fourier transform infrared spectroscopy (FTIR) analysis showed the typical characteristic peaks of hydroxyapatite formed on both DC- and AC-EPD coatings. Based on the results of this study, bioactive alginate/Bioglass® coatings are proposed as suitable candidates for applications in dental and orthopedic metallic implants and for bone tissue scaffolds.

Among the different approaches to overcome the common infections and loosening problems of orthopaedic metallic implants, the surface modification of the implant with bioactive coatings is gaining increasing attention, because the presence of a bioactive layer can enhance the bone-to-implant contact and reduce possible problems arising from infections. Furthermore, the combination of bioactive glasses (or ceramics) with biopolymers (so-called ‘soft-coatings’) leads to an improvement in the mechanical properties of the coatings, because the biopolymer acts as a glue, and therefore the sintering process that would lead to a loss in the bioactivity is avoided. A suitable technique to create these organic/inorganic composite coatings is electrophoretic deposition (EPD), which allows the co-deposition of inorganic particles with polymeric molecules and controls the thickness of the deposit by controlling the deposition voltage and time. Considering the similarities in the chemical composition of the mineral phase of the bone and calcium phosphate compounds, many different systems based on this material and in combination with biopolymers have been developed. A description on the EPD process and a compilation of these relevant systems are summarized in this chapter.

45S5 bioactive glass powders with the composition of 45 SiO2, 6 P2O5, 24.5 CaO and 24.5 wt% Na2O were melted and quenched in water to obtain a frit. The frit was milled using two different routes: dry milling followed by sieving to obtain glass particles and wet milling followed by spray drying to obtain a powder comprising porous agglomerates. All feedstocks showed adequate characteristics that make them suitable to be deposited by atmospheric plasma spraying. The powders and coatings were characterised by field-emission gun environmental scanning electron microscope and X-ray diffraction. The roughness and the contact angle of the coatings were also determined. The bioactivity of the powders and coatings was assessed by immersion in simulated body fluid. It was found that bioactive glass prepared from bioglass frit by dry milling exhibited similar bioactivity as that of a commercial bioactive glass. All coatings produced showed good adhesion to the substrate as well as suitable surface properties to ensure efficient contact with body fluid. Regardless of the characteristics of the feedstocks or plasma spray conditions used, all coatings were exclusively made up of an amorphous phase. On the other hand, micrographs revealed that the characteristics of the feedstock strongly impact on the final coating microstructure. The most homogeneous microstructure was obtained when the feedstock was prepared by fine dry grinding of the frit. For this coating, the formation of a bioactive layer was also proved by Fourier transform infrared spectroscopy and X-ray diffraction.

Well dispersed 45S5 Bioglass(®) (BG)-graphene nanoplatelets (GNP) composites were prepared after optimising the processing conditions. Fully dense BG nanocomposites with GNP loading of 1, 3 and 5 vol% were consolidated using Spark plasma sintering (SPS). SPS avoided any structural damage of GNP as confirmed using Raman spectroscopy. GNP increased the viscosity of BG-GNP composites resulting in an increase in the sintering temperature by ~50 °C compared to pure BG. Electrical conductivity of BG-GNP composites increased with increasing concentration of GNP. The highest conductivity of 13 S/m was observed for BG-GNP (5 vol%) composite which is ~9 orders of magnitude higher compared to pure BG. For both BG and BG-GNP composites, in vitro bioactivity testing was done using simulated body fluid for 1 and 3 days. XRD confirmed the formation of hydroxyapatite for BG and BG-GNP composites with cauliflower structures forming on top of the nano-composites surface. GNP increased the electrical conductivity of BG-GNP composites without affecting the bioactivity thus opening the possibility to fabricate bioactive and electrically conductive scaffolds for bone tissue engineering.