Biomedical Research

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In-vitro bacterial adhesion study on stainless steel 316L subjected to magneto rheological abrasive flow finishing

Objective: To study the effect of Magneto rheological abrasive flow finishing (MRAFF) of stainless steel 316L (SS316L) on bacterial adhesion.

Methods: In the MRAFF process, four different SS316L samples were obtained by varying the magnetic flux density from 0.06 tesla to 0.247 tesla by varying the electromagnetic current. In order to study the bacterial adhesion behavior on SS316L samples with respect to the surface roughness at nano level, three different medically significant bacteria such as Escherichia coli, Klebsiella pneumonia and Bacillus subtillis were used and bacterial adhesions were studied by means of Colony Forming Units (CFU) plate counting. In order to visualize the bacterial attachments with the metallic surface, epifluorescent images were used.

Results and Discussion: The average surface roughness of the samples was decreasing with the increase of magnetic flux density and they were analysed by means of Coherence Correlation Interferometer (CCI). The range of nano level surface roughness values obtained on the steel surface is 10.52 nm to 37.4 nm. With the same sample surface roughness of 37.4 nm, the bacteria Klebsiella pneumonia has got highest adherence of 47 × 108 CFU/ml and Escherichia coli has got least adherence of 28 × 108 CFU/ml. The inhibit nature of the 316L stainless steel towards the bacterial attachment was higher for Escherichia coli with 19 × 108 CFU/ml for the sample with the minimum average surface roughness, while for the other two bacteria, the inhibition were least and identical with 13 × 108 CFU/ml.

Conclusion: From the experimental results with respect to the bacterial Colony Forming Units (CFU), it was observed that the attitude of bacterial adhesion was more on higher surface roughness and less at the least surface roughness in the period of incubation of 18 h. It also depends on the type of the bacterial cell and its geometry.

Author(s): Kathiresan S, Mohan B