Slavomir Biedron

Femtosecond laser microstructuring and bioactive nanocoating of titanium surfaces in relation to chondrocyte growth.

Introduction: Titanium implants can be regarded as the current gold standard for restoration of sound transmission in the middle ear following destruction of the ossicular chain by chronic inflammation. Many efforts have been made to improve prosthesis design, while less attention had been given to the role of the interface. We present a study on chemical nanocoating on microstructured titanium contact surface with bioactive protein. Materials and Methods: Titanium samples of 5mm diameter and 0,25mm thickness were structured by means of a Ti:Sapphire femtosecond laser operating at 970nm with parallel lines of 5μm depth, 5μm width and 10μm inter-groove distance. In addition, various nanolayers were applied to titanium samples by aminosilanization, to which Star-Polyethylene glycole (Star-PEG) molecules plus biomarkers (e.g. RGD peptide sequence) were linked. Results: Chondrocytes could be cultured on microstructured surfaces without reduced rate of vital / dead cells compared to native surfaces. Chondrocytes also showed contact guidance by growing along ridges particularly on 5μm lines. On nanocoated titanium samples, first results showed a strong effect of Star-PEG suppressing unspecific protein absorption, while RGD peptide sequence did not promote chondrocyte cell growth. Discussion: According to these results, the idea of promoting cell growth on titanium prosthesis contact surfaces compared to non-contact surfaces (e.g. prosthesis shaft) by nanocoating is practicable. However, relative selectivity induced by microstructures for growth of chondrocytes compared to fibrocytes is subject to further evaluation.

From bench to bedside: stereoscopic imaging in experimental and clinical otology

Since operation microscopes have been introduced to otology in the early 1950s, surgical reconstruction of middle ear function has been developed further to restore sound transmission with lowest loss possible. Today, research focuses on material properties for prosthetic replacement of middle ear ossicles and long-term outcome of reconstructive middle ear surgery. This study shows how stereoscopy is used to evaluate tissue-material interaction and its clinical impact for future restoration of middle ear function.

Evaluation of the cochlear micro-morphology and the internal dimensions of the cochlear scalae with special reference to insertional trauma during cochlear implantation.

Cochlear implantation is a widely accepted treatment for deafness and profound sensorineural hearing loss. In the context of widening indications for cochlear implantation, implantation in patients with significant residual hearing and the decreasing age of cochlear recipients the procedure itself must prove absolutely reliable, and preservation of functional structures of the inner ear must be further improved. It is known that electrode insertion trauma can cause significant degeneration of spiral ganglion cells. Though efforts on improving electrode arrays and insertion techniques have been made, even with the best available devices and skilful insertion, complete loss of residual hearing occurs in up to 10–20 per cent of implantations (Roland & Wright, 2006). In addition, damage of inner ear structures is a frequent finding in histologic studies of temporal bones with inserted cochlear implants, even if only studies with precurved electrode arrays are taken into account (Tykocinski et al., 2001; Wardrop et al., 2005). Thus, we performed an examination of histologic temporal bone sections and measured the internal diameters of the cochlear scalae in order to obtain data on typical inner ear injuries caused by cochlear implantation.

Femtosecond Laser Microstructuring of Titanium Surfaces for Middle Ear Ossicular Replacement Prosthesis — Results of Preliminary Studies

The objective of this study was to optimize titanium surfaces by means of Ti:Sapphire femtosecond laser to improve the attachment of human cartilage cells on titanium prosthesis in middle ear surgery. The application of microstructures on titanium samples was evaluated and the influence of these microstructures on human auricular chondrocytes was studied in-vitro. After establishing the ear chondrocyte cell culture, cells were seeded on titanium platelets with selected microstructure patterns. Whereas the phenotype of cells seeded on unstructured titanium was similar to cells grown on standard tissue culture surfaces, the morphology of chondrocytes grown on structured titanium samples was influenced by the pattern. For future titanium middle ear prosthesis structural optimizations will be developed to promote chondrocyte growth and adhesion while impeding fibrocyte proliferation to avoid scarring on implant interfaces.

What every surgeon wants - Practical aspects on the use of stereoscopic applications in operative theatres

Introduction: Many operative specialties rely on the use of microscopes and endoscopes for visualizing operative fields in minimally invasive or microsurgical interventions. Conventional optical devices present relevant details only to the surgeon or one assisting professional. Advances in information technology have propagated stereoscopic visual information to all operative theatre personnel in real time, which, in turn, adds to the load of complex technical devices to be handled and maintained in operative theatres. Material and methods: In the last six years, we have been using conventional (SD, 720 x 576 pixels) and high definition (1280 x 720 pixels) stereoscopic video cameras attached to conventional operative microscopes either in parallel to direct visualization of the operative field or as all-digital processing of the operative image for the surgeon including all other staff. Aspects included the type of display used, image quality, time delay due to image processing, visual comfort, time consumption in set-up, ease of use as well as robustness of the system. Results: General acceptance of stereoscopic display technology is high as all staff members are able to share the same visual information. The use of stereo cameras in parallel to direct visualization or as only visualization device mostly depended on image quality and personal preference of the surgeon. Predominant general factors are robustness, ease of use and additional time consumption imposed by setup and handling. Visual comfort was noted as moderately important as there was wide variability between staff members. Type of display used and post-processing issues were regarded less important. Time delay induced by the video chain was negligible. Conclusion: The additional information given by stereoscopic video processing in real time outweighs the extra effort for handling and maintenance. However, further integration with existing technology and with the general workflow enhances acceptance especially in units with high turnover of operative procedures.

Femtosecond laser microstructuring of titanium surfaces for middle ear ossicular replacement prosthesis

Introduction: While a variety of materials has been evaluated for replacement of human middle ear ossicles following inflammation, titanium and its alloys have shown excellent sound transmission properties and biocompatibility. However, cartilage thickness at the tympanic membrane interface deteriorates over time, while fibrous tissue formation may dislodge the titanium prosthesis. This study was performed to evaluate the effect of microstructures on titanium surfaces in contact with adjacent biological tissue. Materials and Methods: Titanium samples of 5mm diameter and 0,25mm thickness were structured by means of a Ti:Sapphire femtosecond laser operating at 970nm. The structures applied were lines of parabolic shape (cross-sectional) of 5µm (parallel), 5µm (cross-hatch) and 10µm width (parallel). The inter-groove distance between two maxima was exactly twice the line width. Results: Lines smaller than 5µm were not feasible due to the natural irregularity of the basic material with pits and level changes of up to 2µm. The process showed little debris and constant microstructure shape over the whole structured area (2x2mm). The resulting debris was examined for toxic by-products on human fibrobcytes and chondrocytes. Discussion: The results show that microstructures can be applied on titanium surfaces for human implantation with reproducible and constant shapes. Further studies will focus on cell culture which has suggested a relative selectivity for chondrocyte compared to fibrocyte growth in earlier studies with selected microstructures.

Femtosecond Laser Microstructuring and Bioactivation of Titanium Surfaces for Middle Ear Ossicular Replacement Prosthesis

Introduction: While a variety of materials have been evaluated for replacement of human middle ear ossicles following inflammation, titanium and its alloys have shown excellent sound transmission properties and biocompatibility. However, cartilage thickness at the tympanic membrane interface deteriorates over time, while fibrous tissue formation may dislodge the titanium prosthesis. This study was performed to evaluate the effect of microstructures and biologically active nanolayers on titanium surfaces in contact with adjacent biological tissue. Materials and Methods: Titanium samples of 5mm diameter and 0,25mm thickness were structured by means of a Ti:Sapphire femtosecond laser operating at 970nm. The structures applied were lines of cross-sectional parabolic shape of 5μm (parallel), 5μm (cross-hatch) and 10μm width (parallel). The inter-groove distance between two maxima was twice the line width. Nanocoating was applied by means of chemical vapor deposition (CVD) in various layers: Polyethylene Glycol (PEG) only, PEG with RGD peptide sequence and PEG + RGD + Bone Matrix Protein (BMP)-7. Results: Lines smaller than 5μm were not feasible due to the natural irregularity of the basic material with pits and level changes of up to 2μm. Cell culture revealed that microstructures were able to generate oriented cell growth along structured lines. PEG did perform as “stealth” coating to avoid unspecific protein adsorption. Discussion: The results show that microstructures can be applied on titanium surfaces for human implantation with reproducible and constant shapes. Further studies will focus on relative promotion of chondrocyte compared to fibrocyte growth by various concentrations of BMP-7.