Electrophoretic deposition of hydroxyapatite–CaSiO3–chitosan composite coatings

Electrophoretic deposition of collagen/chitosan films with copper-doped phosphate glasses for orthopaedic implants

Coatings with bioactive properties play a key role in the success of orthopaedic implants. Recent studies focused on composite coatings incorporating biocompatible elements that can increase the nucleation of hydroxyapatite (HA), the mineral component of bone, and have promising bioactive and biodegradable properties. Here we report a method of fabricating composite collagen, chitosan and copper-doped phosphate glass (PG) coatings for biomedical applications using electrophoretic deposition (EPD). The use of collagen and chitosan (CTS) allows for the co-deposition of PG particles at standard ambient temperature and pressure (1 kPa, 25 °C), and the addition of collagen led to the steric stabilization of PG in solution. The coating composition was varied by altering the collagen/CTS concentrations in the solutions, as well as depositing PG with 0, 5 and 10 mol% CuO dopant. A monolayer of collagen/CTS containing PG was obtained on stainless steel cathodes, showing that deposition of PG in conjunction with a polymer is feasible. The mass of the monolayer varied depending on the polymer (collagen, CTS and collagen/CTS) and combination of polymer + PG (collagen-PG, CTS-PG and collagen/CTS-PG), while the presence of copper led to agglomerates during deposition at higher concentrations. The deposition yield was studied at different time points and showed a profile typical of constant voltage deposition. Increasing the concentration of collagen in the PG solution allows for a higher deposition yield, while pure collagen solutions resulted in hydrogen gas evolution at the cathode. The ability to deposit polymer-PG coatings that can mimic native bone tissue allows for the potential to fabricate orthopaedic implants with tailored biological properties with lower risk of rejection from the host and exhibit increased bioactivity.

Anodizing/Anaphoretic Electrodeposition of Nano-Calcium Phosphate/Chitosan Lactate Multifunctional Coatings on Titanium with Advanced Corrosion Resistance, Bioactivity, and Antibacterial Properties

The aim of this work was to investigate corrosion resistivity, bioactivity, and antibacterial activity of novel nano-amorphous calcium phosphate (ACP) potentially multifunctional composite coatings with and without chitosan oligosaccharide lactate (ChOL), ACP + ChOL/TiO₂ and ACP/TiO₂ ACP + ChOL/TiO₂, respectively, on the titanium substrate. The coatings were obtained by new single-step in situ anodization of the substrate to generate TiO₂ and the anaphoretic electrodeposition process of ACP and ChOL. The obtained coatings were around 300 ± 15 μm thick and consisted of two phases, namely, TiO₂ and hybrid composite phases. Both ACP/TiO₂ and ACP + ChOL/TiO₂ have improved corrosion stability, whereas the ACP + ChOL/TiO₂ coating showed better corrosion stability. It was shown that at the very start of the deposition process, the formation of the ChOL/TiO₂ layer takes place predominantly, which is followed by the inclusion of ChOL into ACP with simultaneous growth of TiO₂. This deposition mechanism resulted in the formation of strongly bonded uniform stable coating with high corrosion resistance. In vitro bioactivity was investigated by immersion of the samples in simulated body fluid (SBF). There is in-bone-like apatite formation on both ACP/TiO₂ and ACP + ChOL/TiO₂ surfaces upon immersion into SBF, which was proven by X-ray diffraction and Fourier transform infrared spectroscopy. While ACP/TiO₂ shows no antibacterial activity, ACP + ChOL/TiO₂ samples exhibited three- to fourfold decreases in the number of Staphylococcus aureus and Pseudomonas aeruginosa, respectively, after 420 min. The probable mechanism is binding ChOL with the bacterial cell wall, inhibiting its growth, altering the permeability of the cell membrane, and leading to bacterial death.

Surface functionalization of chitosan as a coating material for orthopaedic applications: A comprehensive review

Metallic implants have dominated the biomedical implant industries for the past century for load-bearing applications, while the polymeric implants have shown great promise for tissue engineering applications. The surface properties of such implants are critical as the interaction of implant surfaces, and the body tissues may lead to unfavourable reactions. Desired implant properties are biocompatibility, corrosion resistance, and antibacterial activity. A polymer coating is an efficient and economical way to produce such surfaces. A lot of research has been carried out on chitosan (CS)-modified metallic and polymer scaffolds in the last decade. Different methods such as electrophoretic deposition, sol-gel methods, dip coating and spin coating, electrospinning, etc. have been utilized to produce CS coatings. However, a systematic review of chitosan coatings on scaffolds focussing on widely employed techniques is lacking. This review surveys literature concerning the current status of orthopaedic applications of CS for the purpose of coatings. In this review, the various preparation methods of coating, and the role of the surface functionalities in determining the efficiency of coatings are discussed. Effect of nanoparticle additions on the polymeric interfaces and in regulating the properties of surface coatings are also investigated in detail.

Electrophoretic deposition of polymers and proteins for biomedical applications

This review is focused on new electrophoretic deposition (EPD) mechanisms for deposition biomacromolecules, such as biopolymers, proteins and enzymes. Among the rich literature sources of EPD of biopolymers, proteins and enzymes for biomedical applications we selected papers describing new fundamental deposition mechanisms. Such deposition mechanisms are of critical importance for further development of EPD method and its emerging biomedical applications. Our goal is to emphasize innovative ideas which have enriched colloid and interface science of EPD during recent years. We describe various mechanisms of cathodic and anodic EPD of charged biopolymers. Special attention is focused on in-situ chemical modification of biopolymers and crosslinking techniques. Recent innovations in the development of natural and biocompatible charged surfactants and film forming agents are outlined. Among the important advances in this area are the applications of bile acids and salts for EPD of neutral polymers. Such innovations allowed for the successful EPD of various electrically neutral functional polymers for biomedical applications. Particularly important are biosurfactant-polymer interactions, which facilitate dissolution, dispersion, charging, electrophoretic transport and deposit formation. Recent advances in EPD mechanisms addressed the problem of EPD of proteins and enzymes related to their charge reversal at the electrode surface. Conceptually new methods are described, which are based on the use of biopolymer complexes with metal ions, proteins, enzymes and other biomolecules. This review describes new developments in co-deposition of biomacromolecules and future trends in the development of new EPD mechanisms and strategies for biomedical applications.

Electrokinetic transport and distribution of antibacterial nanoparticles for endodontic disinfection

AIM

To assess a novel, noninvasive intervention capable of mobilizing charged antibacterial nanoparticles to the apical portions of the root canal system, utilizing the principles of electrokinetics.

METHODS

Experiments were conducted in three stages. Stage-1: A computer model was generated to predict and visualize the electric field and current density distribution generated by the proposed intervention. Stage-2: Transport of chitosan nanoparticles (CSnp) was evaluated qualitatively using a transparent microfluidic model with fluorescent-labelled CSnp. Stage-3: An ex vivo model was utilized to study the antimicrobial efficacy of the proposed treatment against 3-week-old monospecies E. faecalis biofilms. Scanning electron microscopy (SEM) was also utilized in this stage to confirm the deposition of CSnp.

RESULTS

The results of the computer simulations predicted an electric field and current density that reach their maxima at the apical constriction of the root canal. Correspondingly, the microfluidic experiments demonstrated rapid, controlled CSnp transport throughout the simulated root canal anatomy with subsequent distribution and deposition in the apical constriction as well as periapical regions. Infected root canals when subjected to the novel treatment method resulted in a mean bacterial reduction of 2.1 log CFU. SEM analysis revealed electrophoretic deposition of chitosan nanoparticles onto the root canal dentine walls in the apical region.

CONCLUSION

The findings from this study demonstrate that the combination of cationic antibacterial nanoparticles with a low-intensity electric field results in particle transportation (electrophoresis) and deposition within the root canal. This results in a synergistic antibiofilm efficacy and has the potential to enhance root canal disinfection.

Electrophoretic deposition of chitosan coatings on the Ti15Mo biomedical alloy from a citric acid solution

Chitosan biocoatings were successfully deposited on the Ti15Mo alloy surface via cataphoretic deposition from a solution of 1 g dm⁻³ of chitosan in 4% (aq) citric acid. The influence of the cataphoretic deposition parameters on quality and morphology of the obtained coatings were investigated using fluorescence and scanning electron microscopy. The functional groups' presence in chitosan chine were confirmed by ATR-FTIR methods. X-ray analysis revealed the amorphous structure of the chitosan coatings on the Ti15Mo alloy surface. The conducted studies also include assessing the abrasion resistance and adhesion to the substrate of the obtained chitosan coatings. The results show that utilizing the citric acid as a solvent results in the formation of pore free coatings. The yield of the electrophoretic deposition process was in the range of 2–10 mg of deposited chitosan per 1 cm². The obtained coatings through the unique properties of chitosan are a promising biomaterial for application in medicine.

Chitosan biocoatings were successfully deposited on the Ti15Mo alloy surface via cataphoretic deposition from a solution of 1 g dm⁻³ of chitosan in 4% (aq) citric acid.

Electrodeposition of Polysaccharide and Protein Hydrogels for Biomedical Applications

In the last few decades, polysaccharide and protein hydrogels have attracted significant attentions and been applied in various engineering fields. Polysaccharide and protein hydrogels with appealing physical and biological features have been produced to meet different biomedical applications for their excellent properties related to biodegradability, biocompatibility, nontoxicity, and stimuli responsiveness. Numerous methods, such as chemical crosslinking, photo crosslinking, graft polymerization, hydrophobic interaction, polyelectrolyte complexation and electrodeposition have been employed to prepare polysaccharide and protein hydrogels. Electrodeposition is a facile way to produce different polysaccharide and protein hydrogels with the advantages of temporal and spatial controllability. This paper reviews the recent progress in the electrodeposition of different polysaccharide and protein hydrogels. The strategies of pH induced assembly, Ca2+ crosslinking, metal ions induced assembly, oxidation induced assembly derived from electrochemical methods were discussed. Pure, binary blend and ternary blend polysaccharide and protein hydrogels with multiple functionalities prepared by electrodeposition were summarized. In addition, we have reviewed the applications of these hydrogels in drug delivery, tissue engineering and wound dressing.

HA Coating on Ti6Al7Nb Alloy Using an Electrophoretic Deposition Method and Surface Properties Examination of the Resulting Coatings

Ti and its alloys, which are commonly used in biomedical applications, are often preferred due to their proximity to the mechanical properties of bone. In order to increase the biocompatibility and bioactivities of these materials, biomaterials based on ceramic are used in coating operations. In this study, by using an electrophoretic deposition method, instead of on the Ti6Al4V alloy which is commonly used in the literature, a hydroxyapatite (HA) coating operation was applied on the surface of the Ti6Al7Nb alloy, and the surface properties of the coatings were examined. Ti6Al7Nb is a new-generation implant on which there have not been many studies. The voltage values which were used in the coating operation were 50, 100, 150 and 200 V, and the time parameter was stabilized at 1 min. In our method, when preparing the solution, HA, ethanol, and polyvinyl alcohol (PVA) were used. At the end of the study, by using an electron microscope (SEM) the microstructures of the coatings were examined; elemental analyses (EDS) of the coating surfaces were performed; and by using an X-radiation diffraction (XRD) method, the phases which the coatings contained and the concentration of these phases were determined, and the coating thickness, roughness, and hardness values were also determined. Also, by conducting a Scratch test, the strength of the surface combination was examined. At the end of the study, in each parameter, a successful HA coating was seen. By comparing parameters with each other, the ideal voltage value in this coating was determined. It was determined that the most suitable coating was obtained at 100 V voltage and 1 min deposition time.

Nanostructured akermanite glass-ceramic coating on Ti6Al4V for orthopedic applications

Glass ceramics are widely used to enhance the functionality of inert metallic materials typically used for hard-tissue engineering. Biofunctionality of glass ceramics can in turn be significantly boosted with the addition of trace element dopants. Herein, we synthesized a nanostructured glass ceramic and used magnesium (Mg), which is known to promote osteoblast adhesion and proliferation, for further functionalization. The nanostructured akermanite glass ceramic (Ca₂MgSi₂O₇) was used to coat Ti6Al4V substrates by the sol-gel method. Scanning and transmission electron microscopy as well as X-ray diffraction were used to assess the structural morphology and phase composition of the coating, respectively. The micrographs showed a uniform and crack-free coating structure. Atomic force microscopy observation revealed a disordered surface roughness for coated samples. In vitro cytocompatibility tests revealed that Saos-2 cells cultured on bare samples adopted a rounded morphology, whereas cells cultured on the coated samples represented a more spread out configuration and also increased proliferation. The characterizing tests confirmed the efficiency of the synthesis method and the in vitro biocompatibility of the synthesized coating, indicating its suitability to be used for bone implants.

316L Stainless Steel Manufactured by Selective Laser Melting and Its Biocompatibility with or without Hydroxyapatite Coating

To fabricate metallic 316L/HA (hydroxyapatite) materials which meet the requirements of an implant’s mechanical properties and bioactivity for its function as human bone replacement, selective laser melting (SLM) has been employed in this study to prepare a 316L stainless steel matrix, which was subsequently covered with a hydroxyapatite (HA) coating using the sol-gel method. High density (98.9%) as-printed parts were prepared using a laser power of 230 W and a scanning speed of 800 mm/s. Austenite and residual acicular ferrite existed in the microstructure of the as-printed 316L stainless steel, and the sub-grain was uniform, whose primary dendrite spacing was around 0.35 μm. The as-printed 316L stainless steel showed the highest Vickers hardness, elastic modulus, and tensile strength at ~ (~ means about; same applies below unless stated otherwise) 247 HV, ~214.2 GPa, and ~730 MPa, respectively. The elongation corresponding to the highest tensile strength was ~38.8%. The 316L/HA structure, measured by the Relative Growth Rate (RGR) value, exhibited no cell cytotoxicity, and presented better biocompatibility than the uncoated as-printed and as-cast 316L samples.

Vancomycin incorporated chitosan/gelatin coatings coupled with TiO2-SrHAP surface modified cp-titanium for osteomyelitis treatment

Commercially pure Titanium (Cp-Ti) was electrophoretically modified using double layer coatings consisting of TiO₂-SrHAP as the first layer (TH) followed by vancomycin incorporated Chitosan/Gelatin as the second layer (THV). The nano crystalline phase of coated Strontium incorporated hydroxyapatite (Sr-HAP) confirmed through X-ray diffraction studies (XRD). The polyelectrolyte complex formation between chitosan and gelatin, the stability of the drug, the bonding between chitosan and Sr-HAP were confirmed through infra-red spectroscopic studies (IR). The average roughness (R_a) value calculated from atomic force microscopy (AFM) corroborates with the water contact angle data, which clearly confirms the tuning property of the surface in relation to the surface energy and roughness of the coated samples. The total amount of vancomycin encapsulated was calculated to be 11.5 μg. Antibacterial activity was found against both Staphylococcus aureus strains methicillin resistant Staphylococcus aureus (MRSA) and methicillin sensitive Staphylococcus aureus (MRSA) for a drug concentration of 2.74 μg released after 12 h of immersion. The in-vitro cell culture studies showed enhanced cellular activity for THV samples. Thus, THV samples have a dual action at the surface, by resisting the bacterial adhesion and enhancing cellular interaction at the bio-interface, making it a promising candidate to treat osteomyelitis infection.

Review of Electrochemically Triggered Macromolecular Film Buildup Processes and Their Biomedical Applications

Macromolecular coatings play an important role in many technological areas, ranging from the car industry to biosensors. Among the different coating technologies, electrochemically triggered processes are extremely powerful because they allow in particular spatial confinement of the film buildup up to the micrometer scale on microelectrodes. Here, we review the latest advances in the field of electrochemically triggered macromolecular film buildup processes performed in aqueous solutions. All these processes will be discussed and related to their several applications such as corrosion prevention, biosensors, antimicrobial coatings, drug-release, barrier properties and cell encapsulation. Special emphasis will be put on applications in the rapidly growing field of biosensors. Using polymers or proteins, the electrochemical buildup of the films can result from a local change of macromolecules solubility, self-assembly of polyelectrolytes through electrostatic/ionic interactions or covalent cross-linking between different macromolecules. The assembly process can be in one step or performed step-by-step based on an electrical trigger affecting directly the interacting macromolecules or generating ionic species.

Colloidal methods for the fabrication of carbon nanotube-manganese dioxide and carbon nanotube-polypyrrole composites using bile acids

Nature inspired strategies have been developed for the colloidal processing of advanced composites for supercapacitor applications. New approach was based on the use of commercially available bile acid salts, such as sodium cholate (ChNa) and taurocholic acid sodium salt (TChNa). It was demonstrated that cholic acid (ChH) films can be obtained by electrophoretic deposition (EPD) from ChNa solutions. The analysis of deposition yield, quartz crystal microbalance and cyclic voltammetry data provided an insight into the anodic deposition mechanism. The outstanding suspension stability of multiwalled carbon nanotubes (MWCNT), achieved using bile acids as anionic dispersants, allowed the fabrication of MWCNT films by EPD. The use of ChNa for EPD offered advantages of binding and film forming properties of this material. Composite MnO2-MWCNT films, prepared using ChNa as a dispersant and film forming agent for EPD, showed promising capacitive behavior. In another colloidal strategy, TChNa was used as a dispersant for MWCNT for the fabrication of polypyrrole (PPy) coated MWCNT. The use of PPy coated MWCNT allowed the fabrication of electrodes with high active mass loading, high capacitance and excellent capacitance retention at high charge-discharge rates.

Coding for hydrogel organization through signal guided self-assembly

Complex structured soft matter may have important applications in the field of tissue engineering and biomedicine. However, the discovery of facile methods to exquisitely manipulate the structure of soft matter remains a challenge. In this report, a multilayer hydrogel is fabricated from the stimuli-responsive aminopolysaccharide chitosan by using spatially localized and temporally controlled sequences of electrical signals. By programming the imposed cathodic input signals, chitosan hydrogels with varying layer number and thickness can be fabricated. The inputs of electrical signals induce the formation of hydrogel layers while short interruptions create interfaces between each layer. The thickness of each layer is controlled by the charge transfer (Q = ∫idt) during the individual deposition step and the number of multilayers is controlled by the number of interruptions. Scanning electron micrographs (SEMs) reveal organized fibrous structures within each layer that are demarcated by compact orthogonal interlayer structures. This work demonstrates for the first time that an imposed sequence of electrical inputs can trigger the self-assembly of multilayered hydrogels and thus suggests the broader potential for creating an electrical "code" to generate complex structures in soft matter.

Electrodeposition of a biopolymeric hydrogel: potential for one-step protein electroaddressing

The electrodeposition of hydrogels provides a programmable means to assemble soft matter for various technological applications. We report an anodic method to deposit hydrogel films of the aminopolysaccharide chitosan. Evidence suggests the deposition mechanism involves the electrolysis of chloride to generate reactive chlorine species (e.g., HOCl) that partially oxidize chitosan to generate aldehydes that can couple covalently with amines (presumably through Schiff base linkages). Chitosan's anodic deposition is controllable spatially and temporally. Consistent with a covalent cross-linking mechanism, the deposited chitosan undergoes repeated swelling/deswelling in response to pH changes. Consistent with a covalent conjugation mechanism, proteins could be codeposited and retained within the chitosan film even after detergent washing. As a proof-of-concept, we electroaddressed glucose oxidase to a side-wall electrode of a microfabricated fluidic channel and demonstrated this enzyme could perform electrochemical biosensing functions. Thus, anodic chitosan deposition provides a reagentless, single-step method to electroaddress a stimuli-responsive and biofunctionalized hydrogel film.

Electrophoretic deposition of biomaterials

Electrophoretic deposition (EPD) is attracting increasing attention as an effective technique for the processing of biomaterials, specifically bioactive coatings and biomedical nanostructures. The well-known advantages of EPD for the production of a wide range of microstructures and nanostructures as well as unique and complex material combinations are being exploited, starting from well-dispersed suspensions of biomaterials in particulate form (microsized and nanoscale particles, nanotubes, nanoplatelets). EPD of biological entities such as enzymes, bacteria and cells is also being investigated. The review presents a comprehensive summary and discussion of relevant recent work on EPD describing the specific application of the technique in the processing of several biomaterials, focusing on (i) conventional bioactive (inorganic) coatings, e.g. hydroxyapatite or bioactive glass coatings on orthopaedic implants, and (ii) biomedical nanostructures, including biopolymer-ceramic nanocomposites, carbon nanotube coatings, tissue engineering scaffolds, deposition of proteins and other biological entities for sensors and advanced functional coatings. It is the intention to inform the reader on how EPD has become an important tool in advanced biomaterials processing, as a convenient alternative to conventional methods, and to present the potential of the technique to manipulate and control the deposition of a range of nanomaterials of interest in the biomedical and biotechnology fields.

Chitosan composites for bone tissue engineering--an overview

Bone contains considerable amounts of minerals and proteins. Hydroxyapatite [Ca₁₀(PO₄)₆(OH)₂] is one of the most stable forms of calcium phosphate and it occurs in bones as major component (60 to 65%), along with other materials including collagen, chondroitin sulfate, keratin sulfate and lipids. In recent years, significant progress has been made in organ transplantation, surgical reconstruction and the use of artificial protheses to treat the loss or failure of an organ or bone tissue. Chitosan has played a major role in bone tissue engineering over the last two decades, being a natural polymer obtained from chitin, which forms a major component of crustacean exoskeleton. In recent years, considerable attention has been given to chitosan composite materials and their applications in the field of bone tissue engineering due to its minimal foreign body reactions, an intrinsic antibacterial nature, biocompatibility, biodegradability, and the ability to be molded into various geometries and forms such as porous structures, suitable for cell ingrowth and osteoconduction. The composite of chitosan including hydroxyapatite is very popular because of the biodegradability and biocompatibility in nature. Recently, grafted chitosan natural polymer with carbon nanotubes has been incorporated to increase the mechanical strength of these composites. Chitosan composites are thus emerging as potential materials for artificial bone and bone regeneration in tissue engineering. Herein, the preparation, mechanical properties, chemical interactions and in vitro activity of chitosan composites for bone tissue engineering will be discussed.