Dual pO₂/pCO₂ fibre optic sensing film

A fibre optic multi-sensor has been developed for biomedical sensing applications using a tip coating solution sensitive to both oxygen and carbon dioxide. An oxygen sensitive phosphorescence quenching complex based on platinum octaethylporphyrin (PtOEP) was combined with a carbon dioxide sensitive phosphorescence compound based on 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS). When excited by blue light (470 nm), the resultant coating had two fluorescent peaks at 515 nm (green) and 645 nm (red) which responded to partial pressure of CO₂ and O₂ respectively. The sensor was tested in vitro and shown to be able to measure CO₂ and O₂ simultaneously and in real time, with calibration constants of 0.0384 kPa^-1 and 0.309 kPa^-1 respectively. The O₂ sensitive peak received some overlap from the 515 nm peak (0.38% of peak intensity) as well as some cross-sensitivity (maximum, 5.1 kPa pCO₂ gave a measurement equivalent to 0.43 kPa of O₂, a ratio of 0.08 : 1). However, these effects can be subtracted from measurements and no significant cross-sensitivity or overlap was seen in CO₂ measurements from O₂. This novel compound presents great potential for use in medical sensors and we expect it to be important to a wide range of future applications.