Sterilization of PAN/Gelatine Nanofibrous Mats for Cell Growth

Abstract

Nanofi brous mats can be used as a substrate for eukaryotic cell growth in biotechnology, tissue engineering, etc. Several adherent cells (e.g. human fi broblasts) have been shown to grow well on fi ne fi bres. For most applications, it is necessary to sterilize nanofi brous mats before adding the cells. Another possibility would be the addition of antibiotics and antimycotics to the cell culture medium to prevent microbial infection. However, antibiotics are disadvantageous since they might promote the growth of resistant bacteria in possible future medical applications of nanofi brous mats. Possible sterilization techniques include autoclaving, UV-sterilization, ozone treatment, heat sterilization and other techniques which usually necessitate more expensive equipment, such as gamma irradiation. Systematic examinations of the infl uence of diff erent sterilization techniques on the cell growth on nanofi brous mats have not yet been reported in the literature. Here, we report on the fi rst experimental investigations of the eff ect of sterilization with diff erent methods on the properties of polyacrylonitrile (PAN)/gelatine nanofi brous mats, and the resulting growth and adhesion of Chinese hamster ovary cells. While all techniques under investigation yielded sterile nanofibrous mats, autoclaving and heat sterilization change the PAN/gelatine fi bre morphology. Ozone, on the other hand, modifi es the pH value of the culture medium and partly impedes cell adhesion. UV sterilization also suggests a chemical modifi cation of the nanofi brous mat. Unexpectedly, heat sterilization resulted in the highest amount of adherent Chinese hamster ovary cells grown on PAN/gelatine nanofi brous mats in spite of gelatine melting.

Increased Mechanical Properties of Carbon Nanofiber Mats for Possible Medical Applications

“…While in most applications, the nanofibers used have a very high surface-to-volume ratio, here the increase of the nanofiber diameter is not critical. Earlier investigations of the growth of Chinese hamster ovary (CHO) cells on different nanofiber mats revealed that growing on pure PAN nanofiber mats with their typical thin fiber diameters was impossible, while the cells grew well on PAN/gelatin nanofiber mats [36] with average fiber diameters of 490 ± 130 nm [37].…”

“…This effect may be based on the increased nanofiber diameter, impeding sufficient heat supply to the fiber core. In other thicker nanofibers, like PAN/gelatin or PAN/poly(vinylidene fluoride), this problem may not occur since the blend partners are typically dissolved at temperatures below 500 • C [36,47], while PAN/TiO 2 nanofibers do not show an increased fiber diameter and thus behave similar to pure PAN fibers during carbonization [38]. The same effect of incomplete carbonization under identical conditions was already found for the carbonization of pure PAN nanofibers electrospun with a low voltage of 50 kV, resulting in thicker fibers, where no chemical difference to the usual PAN nanofibers electrospun with 80 kV, as done here, can be expected (to be published).…”

“…It is known to be non-cytotoxic, but shows high antibacterial activity against Staphylococcus aureus and Escherichia. coli [34], making such fibers well suited for medical applications such as wound dressings [35] or as a substrate for cell growth in tissue engineering [36].…”

Chemical and Morphological Modification of PAN Nanofibrous Mats with Addition of Casein after

“…We showed that carefully optimising the PAN : casein ratio results in straight, relatively thick nanofibres which can be unambiguously stabilised and carbonised, off ering another route to prepare carbon nanofi bres, or desired dimensions and morphology. While this eff ect could also be reached with PAN/ ZnO and PAN/gelatine blends [25,28], the second aim of our study was to fi nd new blends without the cytotoxicity of ZnO to prepare new substrates for tissue engineering or generally cell growth besides PAN/gelatine, which is partly molten during sterilisation by autoclaving at 121 °C [33]. Casein is relatively stable in this temperature range [34] and may thus be an interesting blend for PAN, possibly supporting cell growth similar to gelatine [33] without losing the nanofi brous structure.…”

“…While this eff ect could also be reached with PAN/ ZnO and PAN/gelatine blends [25,28], the second aim of our study was to fi nd new blends without the cytotoxicity of ZnO to prepare new substrates for tissue engineering or generally cell growth besides PAN/gelatine, which is partly molten during sterilisation by autoclaving at 121 °C [33]. Casein is relatively stable in this temperature range [34] and may thus be an interesting blend for PAN, possibly supporting cell growth similar to gelatine [33] without losing the nanofi brous structure. Combined with the aforementioned material-related approach, another aim was using suffi ciently mechanically stable carbon nanofi brous mats as conductive substrates for tissue engineering, which has oft en been reported in the literature as advantageous for diverse cell types [35].…”