Multiple imaging techniques demonstrate the manipulation of surfaces to reduce bacterial contamination and corrosion

Abstract

SummarySurface imaging techniques were combined to determine appropriate manipulation of technologically important surfaces for commercial applications. The complementarity of the microscopy methods, scanning electron microscopy, electron probe microanalysis and atomic force microscopy assessed and correlated form and function of the surface modifications. Stainless steel disks (1 cm in diameter) were laser-cut from the same sheets of stainless steel and treated by electropolishing or left untreated for controls. Each treatment was analysed separately using each technique. First, the disks were examined by visual inspection and electron probe microanalysis for surface characteristics and elemental composition, respectively. Aliquots of bacterial suspensions (saline rinses of poultry carcasses from a commercial broiler processing plant) were then diluted in broth and monitored for growth by spectrophotometry. Stainless steel disks (1 cm in diameter) were added and the cultures were grown to sufficient density to allow attachment of bacterial cells to test surfaces. Relative differences in the surface morphology shown by atomic force microscopy, including Z ranges, roughness and other measurements, corresponded by treatment with the differences in reduction of bacterial counts shown by scanning electron microscopy. A model of wet-processing conditions tested the effects of corrosive treatment of surfaces. Less bacterial attachment occurred after corrosive treatment on controls and electropolished samples. Electropolishing significantly reduced bacterial numbers and the effects of corrosive action compared to the controls. Thus, the multiple imaging techniques showed that engineered changes on stainless steel surfaces improved the resistance of the surface finish to bacterial attachment, biofilm formation, and corrosive action.

Repeat cycles of drilling equine cortical bone and cleaning and sterilization change the surface characteristics of untreated and electrochemically polished surgical drill bits

“…The results were highly significant, namely independent from their group all 36 dUT drills showed a multitude of brownish spots on their surface whereas only 3 dEP out of 36 did. This shows that electrochemical polishing was successfully increasing the corrosion resistance of stainless steel as described in other studies (Hocheng et al 2001, Arnold et al 2004, Shahryari et al 2008. Corrosion signs were determined microscopically, and the visual identification of corrosion as characteristic brownish spots on the stainless steel surface has been successfully used in many studies.…”

“…Compared to modern three-dimensional methods as e.g. Atomic Force Microscopy (AFM) it is not as suitable for investigation of surface topographies in detail, but today Ra is still the most frequently used roughness parameter in material industry allowing easy comparison of the data obtained in our study (Ungersbock and Rahn 1994, Stout and Blunt 1995, Arnold and Bailey 2000, Arnold et al 2004). Measurements were completed by microscopic porosity counts.…”

“…Focussing on materials in every day clinical routine makes the results more relevant to the surgical field. As a surface modifying technique, electrochemical polishing was chosen as it is used to smoothen and improve the alloy surface, of metal surfaces used for surgical applications, semi-conductors and within the food processing industry (Beddoes and Bucci 1999, Stoodley et al 2005, Gellér et al 2008, Arnold and Bailey 2000, Arnold et al 2004, Lin and Hu 2008, Hocheng et al 2001, Chow et al 2008. In a follow up study to the present one, the influence of electrochemical polishing and its impact on the bacterial attachment will be studied.…”

“…Corrosion signs were determined microscopically, and the visual identification of corrosion as characteristic brownish spots on the stainless steel surface has been successfully used in many studies. (Sandrik und Wragg 1970, Shah und Bernardo 2002, O'Hoy et al 2003, Arnold et al 2004Wichelhaus et al 2004, Henkel et al 2007). Microscopic pictures of each drill were made and classified concerning the existence of such spots.…”

“…Also, electrochemically smoothened surfaces have a thicker and more uniform protective passive layer mostly consisting of chromium oxide compared to untreated surfaces. The corrosion resistance of such a thick passive layer increases the protection of the surface, and therefore smoothened passive stainless steel surfaces are less susceptible to corrosion attacks, resulting in an improved biocompatibility (Beddoes and Bucci 1999, Arnold and Bailey 2000, Arnold et al 2004, Gellér et al 2008 ).…”