Antibacterial copper−hydroxyapatite (Cu−HA) composite coatings on titanium were synthesized using a novel process consisting of two consecutive electrochemical reactions. In the first stage, HA nanocrystals were grown on titanium using the cathodic electrolytic synthesis. The HAcoated titanium was then used as the cathode in a second reaction stage to electrochemically reduce Cu 2+ ions in solution to metallic Cu nanoparticles. Reaction conditions were found that result in nanoscale Cu particles growing on the surface of the HA crystals. The two-stage synthesis allows facile control of copper content in the HA coatings. Antibacterial activity was measured by culturing Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) in the presence of coatings having varying copper contents. The coatings displayed copper concentration-dependent antibacterial activity against both types of bacteria, likely due to the slow release of copper ions from the coatings. The observation of antibacterial activity from a relatively low loading of copper on the bioactive HA support suggests that multifunctional implant coatings can be developed to supplement or supplant prophylactic antibiotics used in implant surgery that are responsible for creating resistant bacteria strains.

A novel process is demonstrated that produces patterns of electrically conductive copper on a flexible polyimide film substrate using standard desktop laser printed toner and near room temperature aqueous chemistry. The laser toner acts as a mask to selectively block the ion exchange self‐metallization (IESM) reduction reaction that forms nanoscale silver or palladium coatings at the polyimide surface. The silver or palladium IESM coating is then used as a catalyst for electroless deposition of copper. Under appropriate conditions, the copper is deposited selectively on top of the catalyst layer. The resulting copper layer has a measured sheet resistance as low as 0.3 Ohms/sq. Electrical isolation is measured between copper traces spaced as close as 300 microns, and high conductivity is measured along traces with widths as low as 200 microns. The minimum pattern size appears to be limited primarily by the resolution of the laser toner pattern, as the IESM metal layer is observed to follow the contours of individual toner particles. The process avoids the use of high temperature, vacuum, and organic solvents and is thus suitable for very low cost prototyping or distributed manufacturing of simple electronic devices.

A two-stage electrochemical synthesis method was developed to deposit copper nanoparticles onto hydroxyapatite-coated titanium. During the first-stage of electrochemical reaction, a submicron thick hydroxyapatite coating was deposited on the titanium cathode followed by electrochemical reduction of copper ions to form copper nanoparticles on the surface of the hydroxyapatite coating. Reaction parameters, including reaction time, deposition current density, copper ion precursor, and concentration were optimized to uniformly deposit nanosized copper particles. The size of the nanoparticles and overall copper content were controlled by adjusting reaction parameters in the second synthesis stage. This method, therefore, offers a route to adjust copper content in electrolytically deposited hydroxyapatite coatings independently from the hydroxyapatite coating reaction. The morphology and composition of the coatings were examined using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), respectively. The crystalline structure and the surface composition of the material were studied using X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. The topography and surface roughness of the coatings were measured using atomic force microscopy (AFM). The quantity of copper ions released in the bacterial growth medium was measured using inductively coupled plasma mass spectrometry (ICP-MS) and was associated with the antimicrobial activity of copper-hydroxyapatite coating. Antibacterial properties of these materials were investigated by culturing Escherichia coli (Gram-negative bacteria) and Staphylococcus aureus (Gram-positive bacteria) in the presence of the coatings. The antibacterial effect of the copper-hydroxyapatite coatings was enhanced by increasing the copper content. The data further suggested that the antibacterial activity was a result of the elution of copper ions from the coatings. The copper nanoparticles acted as a reservoir for copper ions, providing sustained antibacterial activity. The incorporation of nanosized copper into bioactive hydroxyapatite coatings will offer protection against post-surgical infection of orthopedic and dental implants, to reduce or eliminate the use of prophylactic antibiotics that are known to cause antibiotic-resistant bacteria strains to develop.