The effect on stem cell proteins through laser surface treatment of biomaterials
Creators: name: Cosgrove, Daniel George
Publisher: name: University of Lincoln
Year: 2024
Subjects: C910 - Applied biological sciences
H831 - Bioprocess engineering

description: The objectives of this project were to assess the effect of laser surface modificationon the biocompatibility of polymeric biomaterials when used as a substrate for stemcell culture. Human mesenchymal stem cells were cultured on a pair of polymericmaterial substrates with varied incubation times and surface parameters. Poly etherether ketone was selected due to its chemical and physical robustness as well as itsuse in load bearing implants as well as the potential to improve its efficacy viaimproved osteogenicity. The second material was Nylon 6’6 a common member ofthe Nylon family that is regularly used in a number of medical instruments and hasbeen shown in literature to have potential in tissue engineering applications.Samples of both materials were cleaned and prepared for processing. The wattageof laser power used, the traverse speed, the pattern and the spacing between linesof the pattern were modify the material surface were all varied to produce differingsurface patterns. A number of the surface characteristics of the processed sampleswere assessed in order to evaluate the effect of the individual processing parametersmodified. These included:• Material Wettability• Surface Roughness• Surface Chemistry• Surface topography via SEMAnother objective of this project was to assess the effect of laser modified materialsurfaces on the growth rate of hMSCs. Alongside this, a proteomic assay asperformed to assess if any differentiational bias enforced upon hMSC's by materialsthat have undergone processing. The was assessed via the expression of BoneDaniel George Cosgrove University of Lincoln Student ID: COS1017549715Morphogenic Protein 7 (BMP-7). Alongside this, the effect of laser surfacemodification was assessed using a cytotoxicity assay to assess cell growth ratesusing an incubation time course. The results of this study showed that PEEK wasfound to be the more hydrophobic material post processing though lower levels oflaser energy per mm2 squared were found to be more hydrophobic than samplesthat received higher amounts of laser energy. Nylon 6’6 samples on the other handwas much more hydrophilic in comparison to PEEK. Surface roughness was variedin both material, though the highest level of roughness was seen in PEEK asopposed to Nylon 6’6. That being said, PEEK generally was more difficult to producea pattern on, this resulted in the some of the rougher surfaces as the surface simplyvaporised at higher laser energy per mm2. Both materials that underwent surfaceprocessing had totally different responses. When laser energy was applied to Nylon6’6 it resulted in liquefaction which allowed for greater infiltration of atmosphericgasses. This resulted in an increase in an improved ration of nitrogen to carbon.PEEK on the other hand scorched as opposed to liquefying which resulted in a largeincrease in the level of carbon present. Cell response to modified surfaces wasassessed using stem cell incubation followed by a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cytotoxicity assay to assess growth rates ofhMSCs. Cells were incubated at 24 hours, 48 hours and 4 days to assess the effectover time. A statistically significant difference was found between the 24 hour and 48hours and the 24 hours and 4 days. Cell growth rates were higher on samples thathad undergone modification as opposed to unmodified control samples. Finally, theproteomic assay ELISA assay performed showed that there was no statisticallysignificant difference between unmodified and modified material samples.