Antimicrobial evaluation of metal microneedles made by local electrodeposition-based additive manufacturing on metal-coated substrates

Abstract

Abstract 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. 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 two hour and twenty four hour colonization at 37oC 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 twenty four hour 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.