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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]

Calcium phosphate coatings were electrochemically deposited on titanium from the aqueous solution of Ca(NO3)2 and NH4H2PO4 with the current density of 10 mA cm-2 for deposition time of 15 min. The obtained brushite coatings, (CaHPO4·2H2O), were converted to hydroxyapatite (HA) by soaking in simulated body fluid (SBF) for 2, 7 and 14 days. The brushite and hydroxyapatite coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). It was shown that the increase in soaking time increases the porosity, roughness and crystallite domain size of HA coatings and decreases the unit cell parameters and unit cell volume, while does not affect the HA mean pore area. The calcium and phosphorus ions concentrations in SBF were determined by atomic absorption spectroscopy (AAS) and UV-Vis spectroscopy, respectively and the mechanism of HA growth based on dissolution-precipitation was proposed. [Projekat Ministarstva nauke Republike Srbije, br. III 45019, br. III 45015 i br. OI 72004]

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 .

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]

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]

INTRODUCTION: Tissue engineering strives for innovative solutions in addressing challenges associated with contemporary bone tissue implants. This study focuses on the electrophoretic deposition (EPD) of hydroxyapatite-based bioceramic composites containing antibacterial agents onto titanium surfaces. Two composite coatings, hydroxyapatite/chitosan (HAP/CS) and hydroxyapatite/chitosan/gentamicin (HAP/CS/Gent) were developed to combat issues such as poor adhesion, limited antibacterial potential, limited bioactivity, and potential toxicity of implant materials. EXPERIMENTAL: EPD was performed at constant voltage (5 V, 12 min) on pure Ti plates from aqueous (HAP/CS and HAP/CS/Gent) suspensions. The uniformity and functionality of the deposited coatings were assessed through comprehensive physico-chemical characterization using X-ray diffraction (XRD) (Philips PW 1710, Netherlands) and scanning electron microscopy (SEM, Hitachi S-4700, J) equipped with energy dispersive X-Ray spectroscopy (EDS, X-Max, Oxford Instruments, UK). Antibacterial activity was evaluated against Staphylococcus aureus TL and Escherichia coli ATCC 25922 by quantitatively monitoring changes in the viable number of bacterial cells in suspension. Cytotoxicity against MRC-5 and L929 cell lines was investigated using trypan blue dye-exclusion test (DET) and MTT assay for assessing cell metabolic activity. Statistical significance was determined for antibacterial and cytotoxicity results by one-way analysis of variance (ANOVA), followed by multiple comparisons post-hoc test. RESULTS AND DISCUSSION: XRD revealed broadened diffraction maximums corresponding to fine HAP crystallites. Porous surface with homogeneously distributed spherical HAP agglomerates embedded in wax-like polymers' matrix of CS was observed for both coatings by SEM. The addition of gentamicin significantly enhanced the antibacterial activity of the HAP/CS/Gent coating – complete reduction of S. aureus bacterial cells was achieved within 1 h of exposure. MTT and DET tests indicated low cytotoxicity against MRC-5 and L929 tested cell line for both samples. Slightly decreased cell percentage viability due to gentamicin presence was observed for HAP/CS/Gent. CONCLUSIONS: Single-step EPD yielded antibacterial composite coatings with potential for biomedical applications. HAP/CS/Gent showed successful gentamicin loading, favorable crystalline structure, and strong antibacterial effects. The presence of fine HAP crystallites yielded a larger surface area, favorable for new bone growth and improved osseointegration. HAP/CS/Gent exhibited good antibacterial activity against both tested bacteria (especially pronounced against S. aureus – bactericidal effect), while preserving low cytotoxicity, indicating the high potential for biomedical applications. [ABSTRACT FROM AUTHOR]

INTRODUCTION: Electrochemical methods were employed for synthesizing composites intended for applications in medicine as antibacterial coatings on titanium bone implants or as highly efficient antibacterial hydrogels for accelerated wound healing. EXPERIMENTAL: Hydroxyapatite-based coatings were single-step electrophoretically deposited from fourcomponent aqueous suspension containing 1 wt% hydroxyapatite powder (HAP, particles < 200 nm particle size, SigmaAldrich), 0.1 wt% poly(vinyl alcohol) (PVA, medium molecular weight, Sigma-Aldrich), 0.05 wt% chitosan powder (CS, medium molecular weight, 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 collection-FTM, University of Belgrade, Serbia) and Escherichia coli ATCC 25922. For poly(vinyl alcohol)/chitosan (PVA/CHI) hydrogel synthesis poly(vinyl alcohol) powder (PVA, Sigma Aldrich, USA), chitosan powder (CHI, Sigma Aldrich, USA), graphene (Graphene Supermarket, USA), glacial acetic acid (Beta Hem), silver nitrate (MP Hemija), potassium nitrate (Centrohem, Serbia) were used. For antibacterial properties evaluation, monobasic and dibasic (Sigma Aldrich, USA) potassium phosphates were used. Cell culture suspensions for cytotoxicity tests were prepared using MTT tetrazolium salt, EDTA, fetal calf serum and antibiotic-antimycotic solution (Sigma Aldrich, USA). RESULTS AND DISCUSSION: Surface modification of titanium with innovative bioactive coatings enhances biomineralization and reduces post-operation pain and infection risk. Using powerful single-step electrophoretic deposition (EPD) at a constant voltage we have produced various hydroxyapatite-based composite bioceramic coatings in combination with polymers (lignin, chitosan), graphene, and antibacterial agents (silver, gentamicin). Electrochemical methods enable in situ synthesis of AgNPs inside polymer matrices, with the main advantage being the complete absence of any chemical reducing agents that are often toxic and difficult to remove from the material. The electrochemical reduction of Ag+ ions is achieved only using electrical current or pure hydrogen gas that is generated at the cathode in aqueous electrolytes, which allows for obtaining completely green and non-toxic product. Modifications in the synthesis process also enable the control of AgNPs properties, such as size and concentration. CONCLUSIONS: Composite antibacterial coatings were obtained on titanium plates using EPD. Strong antibacterial activity against E. coli and S. aureus was found. Biocompatibility was confirmed using in vitro MTT testing since a noncytotoxic effect was shown towards healthy human peripheral blood mononuclear cells PBMC, fibroblast cell lines MRC-5 and L929, suggesting high potential for bone tissue engineering and medical applications. Hydrogels composed of physically cross-linked poly(vinyl alcohol)/chitosan with embedded AgNPs were successfully developed for applications as antibacterial wound dressings due to their highly favorable properties of silver release, antibacterial activity, and non-toxicity. [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]

Electrophoretic deposition (EPD) was employed to fabricate composite coatings aimed for orthopedic implants. Hydroxyapatite (HAP), poly(vinyl alcohol) (PVA) and chitosan (CS) coatings, with or without antibiotic gentamicin (Gent) were deposited in a single-step process from aqueous suspension, using EPD. Polymer/mineral composite coatings were formed with the aim to mimic the natural composition of bone tissue, along with improved coatings antibacterial properties, at the same time serving as a drug carrier, allowing local administration of antibiotic. Structural and morphological characterization of HAP/PVA/CS and HAP/PVA/CS/Gent coatings was investigated by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TG/DTG), and scanning electron microscopy (SEM) proving carbonate-substituted HAP. The presence of gentamicin contributed to the bactericidal activity of composite HAP/PVA/CS/Gent coating against Staphylococcus aureus and Escherichia coli. Cytotoxicity studies were performed towards human MRC-5 and mice L929 fibroblast cell lines, and both investigated samples (HAP/PVA/CS and HAP/PVA/CS/Gent) expressed good biocompatibility, without causing toxic effect on tested cells. Biomineralization potential was investigated by measuring the alkaline phosphatase activity, demonstrating high potential of HAP/PVA/CS/Gent to induce the growth of new HAP layer. Therefore, the present investigation proposes the production of composite coatings from non-toxic (aqueous) suspensions, consisting of biocompatible and bioactive components, along with antibiotic gentamicin, improving the antibacterial coatings' properties. [Display omitted] • Single-step electrophoretic deposition of HAP/PVA/CS and HAP/PVA/CS/Gent coatings on Ti substrate. • Complete reduction of S. aureus and E.coli in the first hour-exposure to HAP/PVA/CS/Gent coating. • High cell MRC-5 and L929 viabilities (>90%) in the presence of HAP/PVA/CS and HAP/PVA/CS/Gent coatings. • HAP/PVA/CS and HAP/PVA/CS/Gent coatings induced doubled ALP expression levels in MRC-5 cell lines compared to the control. [ABSTRACT FROM AUTHOR]

Abstract: Silver doped hydroxyapatite (HAP) [Ca9.95Ag0.05(PO4)6(OH)2] composite coatings with natural polymer organosolv lignin (Lig) were produced by electrophoretic deposition (EPD) on titanium. Coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The corrosion stability of electrodeposited coatings was evaluated in vitro in Kokubo's simulated body fluid (SBF) at 37 °C using electrochemical impedance spectroscopy (EIS). Antimicrobial properties are directly proportional to the rate of silver ions release from the coatings, determined from inductively coupled plasma spectrometry (ICP-AES). The obtained results are in good agreement with viability of pathogenic bacteria strain Staphylococcus aureus TL in suspension, which had completely disappeared after 24 h. Composite Ag/HAP/Lig coatings were confirmed as non-toxic for healthy immunocompetent peripheral blood mononuclear cells (PBMC). [Copyright &y& Elsevier]