A comparative evaluation of green surfactant-assisted calcium phosphate (CaP) coatings developed through electrodeposition and biomimetic routes

This study compares the properties of green surfactant-assisted calcium phosphate (CaP) coatings developed on 316 L stainless steel (316 L SS) substrates using electrodeposition (ED) and biomimetic (BM) methods. The influence of biosurfactants (BS) on these coatings' properties, deposited through both processes, is also investigated. X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), and Fourier-transform infrared spectroscopy (FTIR) confirm the presence of brushite and hydroxyapatite (HAp) in the ED coatings, while BM coatings show only HAp without BS and both brushite and HAp phases with BS. The SEM analysis reveals distinct morphologies, with BS-assisted coatings showing more organized structures. The presence of BS results in more uniform coatings in both ED and BM methods. Atomic force microscopy (AFM) analysis indicates that BM coatings are smoother than ED coatings, and BS further reduces surface roughness. The comprehensive evaluations through nanoindentation, scratch testing, and corrosion studies reveal that BS- assisted ED coatings exhibit superior hardness (H), elastic modulus (E), adhesion strength, and corrosion resistance. Cytocompatibility studies using the MTT assay demonstrate that all coatings support cell attachment and proliferation without cytotoxic effects, with BM coatings showing slightly better cell viability. This study highlights the potential of green surfactant-assisted CaP coatings developed using ED and BM methods, for improving the biocompatibility and other biological properties of 316 L SS implants.