Page 165 - Clinical relevance of current materials for cranial implants
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                                Leachables from materials used for cranioplasties
All specimens were stored under standard laboratory climate conditions (22.0 ± 1.0 °C and 50 ± 10% humidity) in a dark environment for 20 ± 4 hours.
Twelve bottles with 200 mL of distilled water were prepared and stored in a stove with a continuous temperature of 37.0 ± 1.0 °C. The bottles were sealed airtight. When the temperature of the distilled water reached 37.0 ± 1.0 °C, the half cylinders were inserted into the bottles. Immediately after the cylinders were added (t=0), the first measurement was conducted by taking a 0.5 gram sample of the distilled water from each of the twelve bottles. Subsequent samples were taken after 1, 2, 4, 8, 12, 24, 48 and 72 hours, 7 and 14 days. During this time, no water was added to the bottles. All the samples were stored at 7.0 ± 1.0 °C in a dark environment until further analysis.
High-performance liquid chromatography (HPLC)
All samples were analyzed using a reversed-phase high-performance liquid chromatography (HPLC) system (Shimadzu LC-20AT) with Diode Array (DA) detectors and a ’Zorbax Eclipse Plus C18 Analytical Column’. MMA stock solutions (0.41, 1.03, 2.06, 4.13 and 8.25 μg/mL) in acetonitrile were measured on the HPLC to create a calibration curve relating the area under the curve [mV*s], at the peak locations, and the concentration [μg/mL].
Liquid Chromatography/Mass Spectrometry (LCMS) 8 LC/MS analyses of the different peaks in the HPLC samples were performed using
a ‘Waters XSelect HSS’ HPLC with a ’C18 2.1x50 mm, 3.5 μm’ column (Waters Chromatography B.V., The Netherlands) with a formic acid/acetonitrile/Milli-Q running
solution interfaced to a ‘Bruker Amazon 230 SL’ MS (Iontrap and Dionex Ultimate 3000 (HPLC)) using positive electrospray ionization. Spectra were scanned over a mass range of m/z 70-550, taking an average of 10 spectra and using an ion spray voltage of 4.5 kV, a source temperature of 325 °C, and a nebulizer gas flow rate of 50 L/min.
Statistical Analysis
Pseudo first order kinetics curves were fitted to the data in GraphPad Prism 5 (GraphPad Software, CA, USA) to investigate the influence of different compositions and fabrication methods on the amount of released residual monomers (a=0.05) using:
where M in the quantity of released monomer [μg/g] at time t [h], M0 is the quantity of released monomer at t = 0 [μg/g], and k is a constant [-].
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