Reduction of animal testing - Influence of the orientation of constructed blood vessels during the 3D printing on the measurement of the pseudo-oxygen saturation of an artificial blood substitute using conventional oxygen sensors: a test series

Abstract

Background The development of phantoms to reduce animal testing or to validate new instruments or operation techniques is of increasing importance. On this account, a blood circulation-phantom was developed and used to evaluate conventional oxygen sensors for a newly developed spatula for direct measurement of the blood oxygen saturation at the parenchyma. Methods A solution of copper and nickel sulfate was used as blood substitute. A total of seven different solutions with a pseudo-saturation between 50% and 100% were created. To evaluate the solution as a suitable blood substitute, a two-stage feasibility study was conducted. This study consisted of capturing the absorption spectra of the two sulfate solutions and calibrating the used oxygen sensor. Additionally, blood vessels with a simplified geometry were designed and manufactured using an elastic material (Elastic 50A) with a 3D printer (Formlabs Form 2). To determine the orientation during the printing process, various vessels were printed. Measurements to assess the effects of disturbance (rotation of the vessels during measurements) on the sensor readouts were prepared. Results Upon analyzing the absorption spectra of the blood substitute and ordinary blood, it was observed that the components of the solution behaved similarly to oxygenated and deoxygenated blood, confirming the suitability of copper and nickel sulfate as a blood substitute. The impact of disturbances was also verified through the rotation of the 3D-printed vessels. It was shown that a measurement directly on the disturbances led to outliers and higher values. An optimal orientation was determined to be a lateral placement (90° or 270°) of the sensor. Regarding the orientation of the vessels within the printing space, an orientation of 45° yielded the best results, as the individual layers least affected the light emitted and received by the oxygen sensor. All results pertain to constructed vessels developed using a Formlabs Form 2 printer and Elastic 50A material by Formlabs. Conclusion The achieved results demonstrate the influence of the orientation of the vessel during 3D printing as well as the influence of the position of the vessel during the measurement using a conventional oxygen sensor.