In vitro investigation of electrophoretically deposited bioactive hydroxyapatite/chitosan coatings reinforced by graphene

Surface functionalization of hydroxyapatite nanoparticles for biomedical applications

This review completely covers the various aspects of hydroxyapatite (HAp) nanoparticles and their role in different biological situations, and provides the surface and interface contents on (i) hydroxyapatite nanoparticles and their hybridization with organic molecules, (ii) surface designing of hydroxyapatite nanoparticles to provide their biocompatibility and photofunction, and (iii) coating technology of hydroxyapatite nanoparticles. In particular, we summarized how the HAp nanoparticles interact with the different ions and molecules and highlighted the potential for hybridization between HAp nanoparticles and organic molecules, which is driven by the interactions of the HAp nanoparticle surface ions with several functional groups of biological molecules. In addition, we highlighted the studies focusing on the interfacial interactions between the HAp nanoparticles and proteins for exploring the enhanced biocompatibility. Such studies focus on how these interactions affect the hydration layers and protein adsorption. However, the hydration layer state involves diverse molecular interactions that can alter the shape of the adsorbed proteins, thereby affecting cell adhesion and spreading on the surfaces. We also summarized the relationship between the surface properties of the HAp nanoparticles and the hydration layer. Furthermore, we spotlighted the cytocompatible photoluminescent probes that can be developed by designing HAp/organic nanohybrid structures. We then emphasized the importance of photofunctionalization in theranostics, which involves the integration of diagnostics and therapy based on the surface design of the HAp nanoparticles. Furthermore, the coating techniques using HAp nanoparticles and HAp nanoparticle/polymer composites were outlined for fusing base biomaterials with biological tissues. The advantages of HAp/biocompatible polymer composite coatings include the ability to effectively cover porous or irregularly shaped surfaces while controlling the thickness of the coating layer, and the addition of HAp nanoparticles to the polymer matrix improves the mechanical properties, increases the roughness, and forms the morphologies that mimic bone nanostructures. Therefore, the fundamental design of hydroxyapatite nanoparticles and their surfaces was suggested from various aspects for biomedical applications.

Adjustable dielectric and bioactivity characteristics of chitosan-based composites via crosslinking approach and incorporation of graphene

This study explores the structural, electrical, dielectric, and bioactivity properties of chitosan (CS) composites incorporating graphene (G) nanoparticles. Characterization techniques, including Field Emission Scanning Electron Microscopy (FE-SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), dielectric spectroscopy, and in vitro testing in SBF, were employed to investigate the effects of G content and crosslinking. The XPS peak at 289.89 eV for CS-G10 indicates CC and CH bonds, suggesting significant interactions between chitosan's hydroxyl groups and graphene's carbon atoms, ensuring structural homogeneity. Dielectric constant (ε') gradually increased with G loading (0 %, 1 %, 5 %, and 10 %) for uncrosslinked composites, reaching 17.94, 18.92, 28.28, and 41.1, respectively. Crosslinked composites exhibited reduced ε' values (15.71, 15.42, 14.14, and 27.03) compared to non-crosslinked ones, with marginal increases post-percolation threshold (5 wt% G filling). XRD analysis revealed shifts in characteristic peaks of CS after SBF treatment, with new peaks at 28.9° and 48.5° indicating hydroxyapatite presence, confirming composite bioactivity. CS-G10/GA showed the highest bioactivity, suggesting promise for biomedical applications.

Electrochemical corrosion study of chitosan-hydroxyapatite coated dental implant

Chitosan (Ch) is a naturally occurring biocompatible and bio-degradable material with high corrosion protective capacities for metals in various corrosive media. Hydroxyapatite (HA) is a significant biodegradable and bioactive material. In the present work, chitosan-hydroxyapatite (Ch-HA) composite coatings with various concentrations of chitosan were made on 316L stainless steel (316L SS) using sol-gel dip coating technique. The coatings were characterized by X-ray diffraction (XRD), FTIR, SEM, and electrochemical measurements. The surface morphology results (SEM) of coated implants exposed the fairly dense microstructures having uniformity without cracks and pores indicating that coating was successfully deposited. From electrochemical analyses, it was observed that the value of corrosion current density and the corrosion rate decreased from 6.03 to 0.15 and 5.56-0.13 respectively indicating that 1.5gCh-HA is the best coating concentration. The electrochemical results demonstrated an improvement in the corrosion resistance of 316L SS than the bare one. The decrease in slope and loop area of cyclic voltammograms reveals about improvement in corrosion resistance. This increment in corrosion resistance of the Ch-HA coated SS implant in the artificial saliva is as 1.5gCh-HA > 2gCh-HA >1gCh-HA >0.5gCh-HA. Furthermore, Ch-HA coatings revealed appropriate adhesion with 316L SS substrate for its use in dental implants.

Electrophoretic deposition of hydroxyapatite/chitosan nanocomposites: the effect of dispersing agents on the coating properties

In this study, electrophoretic deposition (EPD) was used for the coating on titanium (Ti) substrate with a composite of hydroxyapatite (HA)-chitosan (CS) in the presence of dispersing agents such as polyvinyl butyral (PVB), polyethylene glycol (PEG), and triethanolamine (TEA). The materials were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), zeta potential, and Fourier transform infrared (FT-IR) spectroscopy. The addition of PVB, PEG, and TEA agents improved the development of Ti coating during the EPD process. These additives increased the suspension stability and promoted the formation of uniform and compact HA/CS nanocomposite coatings on Ti substrates. The electrochemical polarization tests (e.g., potentiodynamic test) of the substrate with and without coating were investigated. Data analysis showed high corrosion resistance of Ti substrate coated with the HA/CS NP composite. The corrosion potentials displayed a shift toward positive values indicating the increase in the corrosion resistance of Ti after coating. In addition to measuring calcium ion release at various pH values and contact times at a biological pH value of 5.5, the stabilities of Ti substrates coated with HA/CS and different dispersing agents were also evaluated. Ti substrates with high anticorrosion properties may have a new potential application in biomedicine.

Electrophoretic deposition was used for coating of titanium substrate with a composite of hydroxyapatite (HA)-chitosan (CS) in the presence of polyvinyl butyral (PVB), polyethylene glycol (PEG), and triethanolamine (TEA).

Recent progress in Tannic Acid-driven antimicrobial/antifouling surface coating strategies

Medical devices and surgical implants are a necessary part of tissue engineering and regenerative medicines. However, the biofouling and microbial colonization on the implant surface continues to be a major...

Electrophoretic Deposition of Biocompatible and Bioactive Hydroxyapatite-Based Coatings on Titanium

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.

Fabrication and applications of bioactive chitosan-based organic-inorganic hybrid materials: A review

Organic-inorganic hybrid materials like bone, shells, and teeth can be found in nature, which are usually composed of biomacromolecules and nanoscale inorganic ingredients. Synergy of organic-inorganic components in hybrid materials render them outstanding and versatile performance. Chitosan is commonly used organic materials in bionic hybrid materials since its bioactive properties and could be controllable tailored by various means to meet complex conditions in different applications. Among these fabrication means, hybridization was favored for its convenience and efficiency. This review discusses three kinds of chitosan-based hybrid materials: hybridized with hydroxyapatite, calcium carbonate, and clay respectively, which are the representative of phosphate, carbonate, and hydrous aluminosilicates. Here, we reported the latest developments of the preparation methods, composition, structure and applications of these bioactive hybrid materials, especially in the biomedical field. Despite the great progress was made in bioactive organic-inorganic hybrid materials based on chitosan, some challenges and specific directions are still proposed for future development in this review.

Animal models in bicompatibility assessments of implants in soft and hard tissues

The ethical dilemmas of using animals as in vivo models in preclinical and clinical examinations have been increasingly present in recent decades. Small laboratory animals (rats, rabbits) will continue to be used because they are cost-effective and permit the formation of statistically testable cohort groups; a task that, for financial, maintenance and care reasons, is almost prohibitive for larger animals. Technological advances in the production of new biomaterials for clinical use are enormous, but screening tests and methods used to assess biocompatibility lag behind these advances. The assessment of biological responses is slow and based on millennial recovery mechanisms in eukaryotic organisms. Therefore, the goal of researchers in this field is to re-evaluate old methods of biocompatibility assessment and introduce new methods of evaluation, especially for in vivo testing. In that sense, a revision of the ISO standards was planned and conducted in 2017, which insisted on cytotoxicity testing in cell lines and produced concrete proposals on how biocompatibility should be quantified. In vivo biocompatibility evaluation of biomaterials used for soft tissue recovery commonly utilises rats. Rabbits are recommended for implants used for hard tissues, because of the rabbit?s size, the possibility of implanting the biomaterials on a larger bone surface, and because of the peculiarities of rabbit bone tissue that favours rapid recovery after bone defects and enables easy reading of the results.

Assessing the Bioactivity of Gentamicin-Preloaded Hydroxyapatite/Chitosan Composite Coating on Titanium Substrate

The electrophoretic deposition process (EPD) was utilized to produce bioactive hydroxyapatite/chitosan (HAP/CS) and hydroxyapatite/chitosan/gentamicin (HAP/CS/Gent) coatings on titanium. The bioactivity of newly synthesized composite coatings was investigated in the simulated body fluid (SBF) and examined by X-ray diffraction, Fourier transform infrared spectroscopy, and field emission scanning electron microscopy. The obtained results revealed carbonate-substituted hydroxyapatite after immersion in SBF, emphasizing the similarity of the biomimetically grown HAP with the naturally occurring apatite in the bone. The formation of biomimetic HAP was confirmed by electrochemical impedance spectroscopy and polarization measurements, through the decrease in corrosion current density and coating capacitance values after 28-day immersion in SBF. The osseointegration ability was further validated by measuring the alkaline phosphatase activity (ALP) indicating the favorable osseopromotive properties of deposited coatings (significant increase in ALP levels for both HAP/CS (3.206 U mL-1) and HAP/CS/Gent (4.039 U mL-1) coatings, compared to the control (0.900 U mL-1)). Drug-release kinetics was investigated in deionized water at 37 °C by high-performance liquid chromatography coupled with mass spectrometry. Release profiles revealed the beneficial "burst-release effect" (∼21% of gentamicin released in the first 48 h) as a potentially promising solution against the biofilm formation in the initial period. When tested against human and mice fibroblast cells (MRC-5 and L929), both composite coatings showed a noncytotoxic effect (viability >85%), providing a promising basis for further medical application trials.

Antibacterial graphene-based hydroxyapatite/chitosan coating with gentamicin for potential applications in bone tissue engineering

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.

Investigating the mechanical behavior of hydroxyapatite-reduced graphene oxide nanocomposite under different loading rates

In this study, the hydroxyapatite (HA)-reduced graphene oxide (rGO) nanocomposite was investigated for its mechanical properties. The nanocomposite used in this study was made in two stages. The HA-rGO powders were first synthesized by hydrogen gas injected hydrothermal method, and then consolidated by spark plasma sintering. HA-rGO nanocomposite was subjected to Vickers indentation experiments with different loading rates. Various analyzes have been used in this study, including x-rays diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscopy, fast fourier transform, and inverse fast fourier transform. The findings of this study showed that the HA in this nanocomposite was reinforced with rGO sheets coated with HA. As the loading rate increased, the slope of the curves in the elastic region was increased, indicating that the elastic modulus was increased. Also, the contact depth at higher loading rates was increased. Plastic deformation was higher at higher loading rates and the hardness had increased. As the loading rate increased from 300 mN to 1 N, the hardness and elastic modulus increased with more slope than when the loading rate changed from 1 N to 2 N. The presence of rGO sheets had partially controlled the HA brittleness.

Surface Characterization of Electro-Assisted Titanium Implants: A Multi-Technique Approach

The understanding of chemical-physical, morphological, and mechanical properties of polymer coatings is a crucial preliminary step for further biological evaluation of the processes occurring on the coatings' surface. Several studies have demonstrated how surface properties play a key role in the interactions between biomolecules (e.g., proteins, cells, extracellular matrix, and biological fluids) and titanium, such as chemical composition (investigated by means of XPS, TOF-SIMS, and ATR-FTIR), morphology (SEM-EDX), roughness (AFM), thickness (Ellipsometry), wettability (CA), solution-surface interactions (QCM-D), and mechanical features (hardness, elastic modulus, adhesion, and fatigue strength). In this review, we report an overview of the main analytical and mechanical methods commonly used to characterize polymer-based coatings deposited on titanium implants by electro-assisted techniques. A description of the relevance and shortcomings of each technique is described, in order to provide suitable information for the design and characterization of advanced coatings or for the optimization of the existing ones.

Electrophoretic deposition of collagen-reinforced HA/CTS biocomposite coatings

In this study, the biomimetic approach described as reverse engineering by trying to copy the excellent concepts of nature and taking nature as a model has been used. In order to mimic the structure of natural bone, hydroxyapatite (HA), chitosan (CTS) and collagen have been combined as a novel type of biocomposite coating. HA/CTS/collagen biocomposite coatings have been successfully electrophoretically deposited on Ti6Al4V biomedical implants. A novel type of a polyelectrolyte consisting of ethanol, water and isopropyl alcohol has been used for the electrophoretic deposition process. The effect of collagen concentration on the structural and corrosion protection performance of the biocomposite coatings has been investigated by X-ray diffraction, field-emission scanning electron microscopy, Fourier transform infrared spectroscopy, potentiodynamic polarization (Tafel extrapolation) and electrochemical impedance spectroscopy techniques. The electrophoretically deposited HA/CTS/collagen biocomposite coatings have exhibited corrosion protection against simulated physiological body fluid up to five times better than that of bare Ti6Al4V alloy.

Electrophoretic Deposition of Hydroxyapatite–Chitosan–Titania on Stainless Steel 316 L

In this research, hydroxyapatite (HA)–chitosan–titania nanocomposite coatings were formed on 316 L stainless steel using electrophoretic deposition (EPD) from alcoholic (methanol and ethanol) suspensions containing 0.5 g/L chitosan and 2 and 5 g/L HA and 2 and 5 g/L Titania. The effect of different parameters on the deposition rate, morphology, and corrosion resistance of the coatings in simulated body fluid (SBF) at 37 °C has been studied. The coatings’ properties were investigated using Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM). Based on the results of this work, it was found that the deposition rate in ethanolic suspensions is lower than methanolic ones. Moreover, the coating surface was smoother when the ethanol was used as a solvent in suspensions in comparison to the ones where methanol was the solvent. The coating deposited from a suspension containing 0.5 g/L chitosan, 2 g/L HA, and 5 g/L titania with ethanol as solvent had the highest corrosion resistance in SBF at 37 °C.

Properties Investigation of GO/HA/Pt Composite Thin Film

Hydroxyapatite/graphene oxide/platinum (HA/GO/Pt) nanocomposite was synthesized and electrodeposited on a pure zirconium substrate. The coated zirconium was annealed at 200, 300, 400, and 600°C in vacuum furnace in presence of argon gas. The structure and morphology of the coated samples were characterized. Biocompatibility and wear and corrosion resistances of specimens were examined. The result of corrosion tests shows that the graphene into HA/Pt composites significantly improves their corrosion resistance. The wear tests results of uncoated and coated samples before and after annealing show that coated samples annealed at 300°C had better wear resistance compared with uncoated and coated samples at other temperatures. Furthermore, the biocompatibility test shows that the coatings improved the cell attachment and proliferation compared to the pure zirconium substrate.

Microbial Corrosion Resistance and Antibacterial Property of Electrodeposited Zn-Ni-Chitosan Coatings

Microbial corrosion is a universal phenomenon in salt water media such as seawater and wastewater environments. As a kind of efficient protective metal coating for steel, the damage of the Zn-Ni alloy coating was found to be accelerated under microbial corrosive conditions. To solve this problem, chitosan, which is considered a natural product with high antibacterial efficiency, was added to Zn-Ni electrolytes as a functional ingredient of electrodeposited Zn-Ni-chitosan coatings. It was found that the addition of chitosan significantly and negatively shifted the electrodeposition potentials and influenced the Ni contents, the phase composition, and the surface morphologies. By exposing the coatings in a sulfate-reducing bacteria medium, the microbial corrosion resistance was investigated. The results showed that compared to the Zn-Ni alloy coating, Zn-Ni-chitosan coatings showed obvious inhibiting effects on sulfate-reducing bacteria (SRB) and the corrosion rates of these coatings were mitigated to some degree. Further research on the coatings immersed in an Escherichia coli-suspended phosphate buffer saline medium showed that the bacteria attachment on the coating surface was effectively reduced, which indicated enhanced antibacterial properties. As a result, the Zn-Ni-chitosan coatings showed remarkably enhanced anticorrosive and antibacterial properties.

Cationic Substitutions in Hydroxyapatite: Current Status of the Derived Biofunctional Effects and Their In Vitro Interrogation Methods

High-performance bioceramics are required for preventing failure and prolonging the life-time of bone grafting scaffolds and osseous implants. The proper identification and development of materials with extended functionalities addressing socio-economic needs and health problems constitute important and critical steps at the heart of clinical research. Recent findings in the realm of ion-substituted hydroxyapatite (HA) could pave the road towards significant developments in biomedicine, with an emphasis on a new generation of orthopaedic and dentistry applications, since such bioceramics are able to mimic the structural, compositional and mechanical properties of the bone mineral phase. In fact, the fascinating ability of the HA crystalline lattice to allow for the substitution of calcium ions with a plethora of cationic species has been widely explored in the recent period, with consequent modifications of its physical and chemical features, as well as its functional mechanical and in vitro and in vivo biological performance. A comprehensive inventory of the progresses achieved so far is both opportune and of paramount importance, in order to not only gather and summarize information, but to also allow fellow researchers to compare with ease and filter the best solutions for the cation substitution of HA-based materials and enable the development of multi-functional biomedical designs. The review surveys preparation and synthesis methods, pinpoints all the explored cation dopants, and discloses the full application range of substituted HA. Special attention is dedicated to the antimicrobial efficiency spectrum and cytotoxic trade-off concentration values for various cell lines, highlighting new prophylactic routes for the prevention of implant failure. Importantly, the current in vitro biological tests (widely employed to unveil the biological performance of HA-based materials), and their ability to mimic the in vivo biological interactions, are also critically assessed. Future perspectives are discussed, and a series of recommendations are underlined.

An overview of graphene-based hydroxyapatite composites for orthopedic applications

Hydroxyapatite (HA) is an attractive bioceramic for hard tissue repair and regeneration due to its physicochemical similarities to natural apatite. However, its low fracture toughness, poor tensile strength and weak wear resistance become major obstacles for potential clinical applications. One promising method to tackle with these problems is exploiting graphene and its derivatives (graphene oxide and reduced graphene oxide) as nanoscale reinforcement fillers to fabricate graphene-based hydroxyapatite composites in the form of powders, coatings and scaffolds. The last few years witnessed increasing numbers of studies on the preparation, mechanical and biological evaluations of these novel materials. Herein, various preparation techniques, mechanical behaviors and toughen mechanism, the in vitro/in vivo biocompatible analysis, antibacterial properties of the graphene-based HA composites are presented in this review.

Electrophoretic deposition: a versatile tool against biomaterial associated infections

Biomaterial-associated infections (BAIs) are today considered as one of the most withering complications of orthopedic implant surgery. Even though BAIs occur relatively infrequently in primary joint replacement surgeries (incidence rates around 1-2%), revision arthroplasties carry up to 40% risk of infection recurrence, with devastating consequences for the patient and significant associated cost. Once the responsible pathogens, mainly bacteria, attach to the surface of the biomaterial, they start creating layers of extracellular matrix with complex architectures, called biofilms. These last mentioned, encapsulate and protect bacteria by hindering the immune response and impeding antibiotics from reaching the pathogens. To prevent such an outcome, the surface of the biomaterials, in particular implants, can be modified in order to play the role of inherent drug delivery devices or as substrates for antibacterial/multifunctional coating deposition. This paper presents an overview of novel electrochemically-triggered deposition strategies, with a focus on electrophoretic deposition (EPD), a versatile and cost-effective technique for organic and inorganic material deposition. Other than being a simple deposition tool, EPD has been recently employed to create novel micro/nanostructured surfaces for multi-purpose antibacterial approaches, presented in detail in this review. In addition, a thorough comparison and assessment of the latest antibacterial and multifunctional compounds deposited by means of EPD have been reported, followed by a critical reflection on current and future prospects of the topic. The relative simplicity of EPD's application, has, by some means, undermined the fundamental requirement of rationality of multifunctional coating design. The demanding practical needs for a successful clinical translation in the growing fields of tissue engineering and antibacterial/multifunctional implant coatings, calls for a more systematic in vitro experimental design rationale, in order to make amends for the scarcity of significant in vivo and clinical studies.