Antimicrobial Evaluation of Metal Microneedles Made by Local Electrodeposition-Based Additive Manufacturing on Metal-Coated Substrates

Electrochemical-based additive manufacturing of metals has many potential uses for the manufacturing of medical devices with small-scale features. In this study, we examined the in vitro antimicrobial properties of metal microneedles made by local electrodeposition-based additive manufacturing called CERES (Exaddon AG, Switzerland) on metal substrates. Three-by-three arrays of copper microneedles were created on copper-coated silicon substrates. To understand the effect of a galvanic couple between gold microneedles and a copper substrate on the antimicrobial activity of the microneedle device, three-by-three arrays of copper microneedles were created on gold-coated silicon substrates. Scanning electron microscopy was used to understand the microstructure of the microneedles; the microneedles were shown to possess hollow bores and sharp tips. X-ray photoelectron spectroscopy indicated the presence of copper, carbon, oxygen, silicon, and nitrogen as well as the absence of toxic impurities for the copper microneedles on copper-coated silicon substrates. X-ray photoelectron spectroscopy indicated the presence of copper, carbon, oxygen, copper, gold, and silicon as well as the absence of toxic impurities for the copper microneedles on gold-coated silicon substrates. The copper surface was noted to have Cu (II) oxide or hydroxide. In vitro cell colonization studies involving the gram-positive bacterium Staphylococcus epidermidis, the gram-negative bacterium Escherichia coli, and the opportunistic fungal pathogen Candida albicans at 2 h and 24 h colonization at 37 degrees C showed generally stronger activity for copper microneedles on copper-coated silicon substrates than for copper microneedles on gold-coated silicon substrates and uncoated silicon substrates. The copper microneedles on gold-coated silicon substrates showed stronger antimicrobial activity than uncoated silicon substrates except for 24 h colonization with Escherichia coli. The results of this study show potential strategies for creating antimicrobial microneedles for medical applications via local electrodeposition-based additive manufacturing.