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Increasing need for improved, compatible bone tissue implants led to the intensive research of novel biomaterials, especially hydroxyapatite (HAP)- -based composite materials on titanium and titanium alloy surfaces. Owing to its excellent biocompatibility and osteoinductivity properties, hydroxyapatite is often used as part of composite biomaterials aimed for orthopedic implant applications. In order to overcome persistent problems of bacterial infection, various antimicrobial agents and materials and their incorporation in such medical devices were investigated. This paper represents a comprehensive review of single-step electrodeposition on titanium of hydroxyapatite/chitosan/graphene composite coatings loaded with silver and antibiotic gentamicin as antibacterial agents. The improvement of mechanical and adhesive properties of deposited composite coatings was achieved by graphene and chitosan addition, while desirable antibacterial properties were introduced by including antibiotic gentamicin and silver. The biocompatibility of electrodeposited HAP and HAP-based composite coatings was evaluated by MTT testing, indicating a non-cytotoxic effect and high potential for future medical use as orthopedic implant coating. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. II45019]

Titanium is a key biomedical material due its good biocompatibility, mechanical properties and corrosion stability, but infections of the implantation site still pose serious threat. One approach to prevent infection is to improve antimicrobial ability of the coating material. Silver doped hydroxyapatite (Ag/HAP) nanoparticles were synthesized by new modified precipitation method. The synthesized powder was used for preparation of Ag/HAP coating on titanium by electrophoretic deposition. The coating was characterized in terms of phase composition and structure by Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray diffraction (XRD); surface morphology and chemical composition was assessed using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Research focused on evaluation of the corrosion behaviour of Ag/HAP coating in simulated body fluid (SBF) at 37 ºC during prolonged immersion time by electrochemical impedance spectroscopy (EIS). Silver doped HAP coating provided good corrosion protection in SBF solution. [Acknowledgements. This research was financed by the Ministry of Education, Science and Technological Development of the Republic of Serbia, contracts No. III 45019 and by National Sciences and Engineering Research Council of Canada (NSERC). Dr Ana Jankovic was financed by the FP7 Nanotech FTM Grant Agreement 245916]

In order to improve corrosion stability and biocompatibility of titanium surfaces, hydroxyapatite (Ca10(PO4)6(OH)2, HAP) has been used as coating material due to the fact that it possess similar chemical composition as bone tissue. Lignin’s (Lig) usage in medical applications could be interesting because it could lead to thermal stability, hydrophilicity, biocompatibility and biodegradability of different materials. Bioceramic hydroxyapatite/lignin (HAP/Lig) coatings on titanium were obtained from ethanol suspension by electrophoretic deposition method. The uniform and compact HAP/Lig coatings were deposited at constant voltage of 60 V for 45 s and sintered at 900°C in argon atmosphere. The corrosion stability of sintered HAP/Lig coatings in simulated body fluid (SBF) at 37°C was investigated by open circuit potential-time measurements and electrochemical impedance spectroscopy (EIS). The greater values of open circuit potential, as well as EIS results, indicated improved corrosion resistance and good corrosion stability of HAP/Lig coatings in simulated body fluid at 37°C .

An aqueous boehmite sol was prepared by the peptization of Al(OH)3. The electrophoretic deposition of boehmite coatings on titanium from the aqueous sol was performed at a constant voltage (from 1.0 to 10 V) and for a constant deposition time (from 10 to 30 min). Increasing the applied voltage and deposition time increased the mass of the boehmite coating. It was shown that boehmite coatings of maximum thickness, low porosity and good adhesion can be formed at lower deposition voltages and longer deposition times. The boehmite powder, obtained by drying the prepared aqueous sol, and the boehmite coatings were thermally treated at 1000 °C and 1300 °C with a holding period of 1 h at the maximum temperature. X-Ray diffraction analysis of the thermally treated samples confirmed the existence of -Al2O3 and Al2O3 phases, respectively, while scanning electron microscopy revealed the graininess of the structure of the -Al2O3 coatings treated at 1300 °C, indicating a significantly lower sintering temperature of the boehmite coating obtained by electrophoretic deposition.

Electrophoretic deposition process (EPD) was successfully used for obtaining graphene (Gr)‐reinforced composite coating based on hydroxyapatite (HAP), chitosan (CS), and antibiotic gentamicin (Gent), from aqueous suspension. The deposition process was performed as a single step process at a constant voltage (5 V, deposition time 12 min) on pure titanium foils. The influence of graphene was examined through detailed physicochemical and biological characterization. Fourier transform infrared spectroscopy, field emission scanning electron microscopy, thermogravimetric analysis, X‐ray diffraction, Raman, and X‐ray photoelectron analyses confirmed the formation of composite HAP/CS/Gr and HAP/CS/Gr/Gent coatings on Ti. Obtained coatings had porous, uniform, fracture‐free surfaces, suggesting strong interfacial interaction between HAP, CS, and Gr. Large specific area of graphene enabled strong bonding with chitosan, acting as nanofiller throughout the polymer matrix. Gentamicin addition strongly improved the antibacterial activity of HAP/CS/Gr/Gent coating that was confirmed by antibacterial activity kinetics in suspension and agar diffusion testing, while results indicated more pronounced antibacterial effect against Staphylococcus aureus (bactericidal, viable cells number reduction >3 logarithmic units) compared to Escherichia coli (bacteriostatic, <3 logarithmic units). MTT assay indicated low cytotoxicity (75% cell viability) against MRC‐5 and L929 (70% cell viability) tested cell lines, indicating good biocompatibility of HAP/CS/Gr/Gent coating. Therefore, electrodeposited HAP/CS/Gr/Gent coating on Ti can be considered as a prospective material for bone tissue engineering as a hard tissue implant. [ABSTRACT FROM AUTHOR]

INTRODUCTION: Following orthopedic surgery, bacterial infection may lead to significant complications related to inflammation in the peri-implant region, including the potential for implant loosening. To address this concern, the surface of metallic implants was modified through the application of bioactive and antibacterial coatings, aiming to mitigate these issues. EXPERIMENTAL: HAP/PVA/CS/Gent coatings was single-step electrophoretically deposited from four-component aqueous suspension containing 1 wt.% hydroxyapatite powder (HAP, particles < 200 nm particle size, Sigma-Aldrich), 0.1 wt.% poly(vinyl alcohol) (PVA, medium molecular weight 89 to 98 kDa, 99 % hydrolysed, Sigma-Aldrich), 0.05 wt% chitosan powder (CS, medium molecular weight, 190 to 310kDa with 75 to 85 % deacetylation degree, Sigma-Aldrich), and aqueous gentamicin sulfate solution (Gent, concentration 50 mg/ml, Sigma-Aldrich) on titanium plates (Sigma-Aldrich). Antibacterial activity of HAP/PVA/CS/Gent coating was evaluated against Staphylococcus aureus TL (culture collectionFTM, University of Belgrade, Serbia) and Escherichia coli ATCC 25922, while kinetics of antibacterial activity was monitored according to our previously published data. In vitro cytotoxicity assay was performed towards two fibroblast cell lines of different origin-mouse origin cell line (L929 (ATCC CRL-6364)) and human lung origin cell line (MRC-5 (ATCC CCL-171)). To evaluate the statistical significance of the biological assay results (antibacterial activity, cytotoxicity and ALP activity), one-way analysis of variance (ANOVA) followed by a multiple comparisons posthoc test was used. RESULTS AND DISCUSSION: HAP/PVA/CS/Gent coating exhibited strong antibacterial effect against both S. aureus and E. coli, especially pronounced against S. aureus, causing bactericidal effect. Cytotoxic effect of HAP/PVA/CS/Gent coating was not pronounced in investigated MRC-5 and L929 cell lines. MRC-5 fibroblast cells in contact with HAP/PVA/CS/Gent doubled alkaline phosphatase levels compared to their contact with the control samples (HAP/PVA/CS), indicating good osteogenic properties. CONCLUSIONS: Electrophoretically deposited HAP/PVA/CS/Gent bioceramic coatings on titanium, demonstrated significant potential as implants in orthopedic practice, functioning as drug carriers. Not only do they possess antibacterial properties, but they also exhibit no adverse effects on living tissue. [ABSTRACT FROM AUTHOR]

Electrophoretic deposition (EDP) is gaining increasing attention both in science and industry, due to novel applications in the processing of advanced ceramic materials and ceramic coatings. Electrophoretic deposition has become very interesting because this method has allowed the formation of thin films or multilayer films of controlled thickness and morphology, enabling the formation of films on substrates of complex geometry, aimed for different applications. This review paper represents the mechanism of electrodeposition of ceramic coatings (alumina and boehmite coatings) on metal surfaces, as well as the determination of the optimal deposition parameters (applied voltage, deposition time, electrodeposition bath temperature, suspension concentration) in order to control the thickness and morphology of deposited films. It was shown that coatings of maximum thickness, low porosity and good adhesion were obtained at lower deposition voltages and for longer deposition times. [ABSTRACT FROM AUTHOR]

An aqueous boehmite sol was prepared by the peptization of Al(OH)3. The electrophoretic deposition of boehmite coatings on titanium from the aqueous sol was performed at a constant voltage (from 1.0 to 10 V) and for a constant deposition time (from 10 to 30 min). Increasing the applied voltage and deposition time increased the mass of the boehmite coating. It was shown that boehmite coatings of maximum thickness, low porosity and good adhesion can be formed at lower deposition voltages and longer deposition times. The boehmite powder, obtained by drying the prepared aqueous sol, and the boehmite coatings were thermally treated at 1000 °C and 1300 °C with a holding period of 1 h at the maximum temperature. X-Ray diffraction analysis of the thermally treated samples confirmed the existence of γ-Al2O3 and α-Al2O3 phases, respectively, while scanning electron microscopy revealed the graininess of the structure of the α-Al2O3 coatings treated at 1300 °C, indicating a significantly lower sintering temperature of the boehmite coating obtained by electrophoretic deposition. [ABSTRACT FROM AUTHOR]

Current trends in biomaterials science address the issue of integrating artificial materials as orthopedic or dental implants with biological materials, e.g., patients' bone tissue. Problems arise due to the simple fact that any surface that promotes biointegration and facilitates osteointegration may also provide a good platform for the rapid growth of bacterial colonies. Infected implant surfaces easily lead to biofilm formation that poses a major healthcare concern since it could have destructive effects and ultimately endanger the patients' life. As of late, research has centered on designing coatings that would eliminate possible infection but neglected to aid bone mineralization. Other strategies yielded surfaces that could promote osseointegration but failed to prevent microbial susceptibility. Needless to say, in order to assure prolonged implant functionality, both coating functions are indispensable and should be addressed simultaneously. This review summarizes progress in designing multifunctional implant coatings that serve as carriers of antibacterial agents with the primary intention of inhibiting bacterial growth on the implant-tissue interface, while still promoting osseointegration. [ABSTRACT FROM AUTHOR]

Biocomposite hydroxyapatite/poly(vinyl alcohol)/chitosan/gentamicin coatings were fabricated on titanium by an electrophoretic deposition process (EPD) from an aqueous suspension using the constant voltage method. Characterization of the deposited coatings was performed by scanning electron microscopy with field emission (FE-SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD) after immersion in simulated body fluid (SBF) at 37 °C. The concentration of the released gentamicin was determined using high-performance liquid chromatography (HPLC) coupled with a mass spectrometer (MS). The release profile confirmed an initial "burst-release effect" with ~ 30 % of the gentamicin released in the first 48 h, which could be of assistance in the prevention of biofilm formation. Antibacterial activity was proven by the agar diffusion method on Staphylococcus aureus TL and Escherichia coli ATCC 25922 bacterial strains. Cytotoxicity was tested by the dye exclusion test (DET) on MRC-5 and L929 fibroblast cell lines, with both coatings expressing nontoxicity. The results showed the high applicability potential of a poly(vinyl alcohol)-based biocomposite coating for medical purposes. [ABSTRACT FROM AUTHOR]

The graphene based silver/hydroxyapatite/graphene (Ag/HAP/Gr) composite coatings were produced by electrophoretic deposition (EPD) on titanium to assemble porous bioactive homogenous coatings, with improved corrosion stability in simulated body fluid (SBF). Novel composite coatings were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), Raman spectroscopy, X-ray photoelectron analysis (XPS) and electrochemical impedance spectroscopy (EIS). The improved properties of graphene based coatings in respect to the graphene-free coatings, as a consequence of toughening action of graphene, were demonstrated: reduced surface cracks, better mechanical resistance (hardness and elastic modulus increased by 10%) and enhanced thermal stability, while the Ca/P ratio was closer to the stoichiometric value. The bioactivity of Ag/HAP/Gr composite coatings was proved by a newly formed apatite layer in SBF with enhanced corrosion stability, while antibacterial activity against Staphylococcus aureus and Escherichia coli and noncytotoxicity against healthy peripheral blood mononuclear cells (PBMC) indicate the high potential for biomedical applications. [ABSTRACT FROM AUTHOR]

Hydroxyapatite is the most suitable biocompatible materialforbone implant coatings. However, its brittleness is a major obstacle,and that is why, recently, research focused on creating compositeswith various biopolymers. In this study, hydroxyapatite coatings weremodified with lignin in order to attain corrosion stability and surfaceporosity that enables osteogenesis. Incorporating silver, well knownfor its antimicrobial properties, seemed the best strategy for avoidingpossible infections. The silver/hydroxyapatite (Ag/HAP) and silver/hydroxyapatite/lignin(Ag/HAP/Lig) coatings were cathaphoretically deposited on titaniumfrom ethanol suspensions, sintered at 900 °C in Ar, and characterizedby X-ray diffraction, scanning electron microscopy, field emissionscanning electron microscopy, attenuated total reflection Fouriertransform infrared, and X-ray photoelectron spectroscopy. The corrosionstability of electrodeposited coatings was evaluated in vitro in Kokubo’ssimulated body fluid (SBF) at 37 °C using electrochemical impedancespectroscopy. Bioactivity was estimated by immersion in SBF to evaluatethe formation of hydroxyapatite on the coating surface. A microcrystallinestructure of newly formed plate-shaped carbonate-hydroxyapatite wasdetected after only 7 days, indicating enhanced bioactive behavior.Both coatings had good corrosion stability during a prolonged immersiontime. Among the two, the Ag/HAP/Lig coating had a homogeneous surface,less roughness, and low values of contact angle. [ABSTRACT FROM AUTHOR]