Comparative study of superhydrophilic and superhydrophobic TiO2/epoxy coatings on AISI 316L stainless steel: surface properties and biocompatibility

Abstract

TiO2/epoxy coatings were successfully applied to the surface of AISI 316L stainless steel to change the wetting properties, with the aim being to improve the biocompatibility of the superhydrophobic/superhydrophilic surfaces. Contact-angle measurements were used to evaluate the wetting properties of the non-coated, epoxy-coated, as-received TiO2/epoxy-coated and fluoroalkylsilane (FAS)-TiO2/epoxy-coated substrates. The as-received TiO2/epoxy coating and FAS-TiO2/epoxy coating showed superhydrophilic and superhydrophobic characteristics, respectively. The average surface roughness (Sa) of the superhydrophobic surface was higher compared to the superhydrophilic surface due to the formation of agglomerates. The biocompatibility evaluated by cell attachment showed that AISI 316L stainless steel with a hydrophilic nature and low Sa is the most favourable surface for bone osteosarcoma cells (MG-63) growth. On the other hand, the two limiting cases of surfaces, superhydrophilic and superhydrophobic coatings with increased roughness compared to AISI 316L, showed lower biocompatibility. Keywords: stainless steel, epoxy coating, TiO 2, wetting properties, biocompatibility Na povr{ino nerjavnega jekla tipa AISI 316L smo uspe{no nanesli TiO2/epoksi prevleke z namenom regulacije omo~itvenih lastnosti, ki vplivajo na izbolj{anje biokompatibilnosti superhidrofobnih/superhidrofilnih povr{in. Z meritvami kontaktnih kotov smo dolo~ili omo~itvene lastnosti~iste jeklene povr{ine ter jeklene povr{ine prevle~ene z epoksidno smolo, s TiO2/epoksi prevleko in fluoroalkilsilan (FAS)-TiO2/epoksi prevleko. TiO2/epoksi prevleka je pokazala superhidrofilno, FAS-TiO2/epoksi prevleka superhidrofobno naravo. Povpre~na hrapavost povr{ine (Sa) superhidrofobne povr{ine je bila vi{ja kot na superhidrofilni povr{ini zaradi opa`ene tvorbe aglomeratov. Analiza biokompatibilnosti je pokazala, da je nerjavno jeklo AISI 316L s hidrofilno naravo in nizko Sa najprimernej{a povr{ina za rast kostnega osteosarkoma (MG-63). Po drugi strani pa sta oba mejna primera prevlek s superhidrofilno in superhidrofobno naravo z ve~jo hrapavostjo v primerjavi z AISI 316L, pokazala manj{o stopnjo biokompatibilnosti.