Direct fluorescent measurement of blood potassium with polymeric optical sensors based on upconverting nanomaterials.

We proposed here a potassium selective optode incorporating NaYF4:Er,Yb upconverting nanorods and chromoionophore ETH 5294 together in hydrophobic polymer matrixes and the response of the optode is based on changes in the upconverting luminescence intensity induced from the absorption change of the proton sensitive chromoionophore. The optode was used for determination of the potassium content in the whole blood sample for the first time. Because the excitation source of 980 nm, as well as the emission wavelength, lies in the near-infrared region, the background absorption and autofluorescence of the biological sample could be eliminated, and ensure the sensitivity and selectivity of the sensor. The potassium levels of sheep plasma and whole blood samples obtained by the optode were comparable with the results obtained by ICPMS and ISE methods, providing possibilities for further application in clinical diagnosis.