Electrophoretic deposition, microstructure and selected properties of zein/cloves coatings on 316L stainless steel

In the present study, we develop zein coatings containing cloves (flower buds of the Syzygium aromaticum tree, a well-known aromatic natural herb) on stainless steel substrates via electrophoretic deposition. The antibacterial activity, drug release, surface (morphology, roughness, and wettability), corrosion, and adhesion properties of the produced zein/cloves coatings were elucidated in detail. The coatings deposited an applied electric field of 20 V/cm with a deposition time of 5 min yielded uniform zein/cloves coatings with a thickness of ~9 μm, which was confirmed by scanning electron microscopy. Fourier transformation infrared spectroscopy analysis confirmed the presence of zein and cloves functional groups in the zein/cloves coatings. The results of tape tests exhibited that the adhesion between the coatings and the substrate was rated as ‘5B’ (Excellent) according to the ASTM-D3359 standard. The zein/cloves coatings exhibited an average roughness of 0.8 ± 0.05 and a contact angle of 60° ± 2°, making them appropriate for orthopedic applications. The antibacterial studies exhibited that the zein/cloves coatings developed zone of inhibition against Staphylococcus aureus and Escherichia coli, confirming the strong antibacterial potential of the coatings. UV–Vis Spectroscopy elucidated that after one week of immersion in phosphate buffer saline, ~65 % of eugenol was released from the zein/cloves coatings. Furthermore, the zein/cloves coatings improved the corrosion resistance by ~3 orders of magnitude compared to bare 316L stainless steel. Antimicrobial and drug release studies confirmed that the zein/cloves coatings can provide a targeted drug delivery system with a potent antimicrobial effect.