Photoluminescence intensity ratio of Eu‐conjugated lactates—A simple optical imaging technique for biomarker analysis for critical diseases

Instant measurement of elevated biomarkers such as lactic acid offers the most promising approaches for early treatment and prevention of many critical diseases including cardiac arrest, stroke, septic shock, trauma, liver dysfunction, as well as for monitoring lactic acid level during intense exercise. In the present study, a unique dependence of visible photoluminescence of Eu³⁺ ions resulting from ⁵D₀ to ⁷F_{J(J = 0,1,2,3,4)} transitions, which can be exploited for rapid detection of biomarkers, both in vitro and ex vivo, has been reported. It is observed that the integrated intensity ratio of photoluminescence signals dominating at 591 and 616 nm originating from ⁵D₀ to ⁷F₂ and ⁵D₀ to ⁷F₁ transitions in Eu³⁺ ions can be used as a biosensing and bioimaging tool for detection of biomarkers released at disease states. The Eu³⁺ integrated photoluminescence intensity ratio approach reported herein for optical detection of lactates in blood serum, plasma and confocal imaging of brain tissues has very high potential for exploitation of this technique in both in vitro monitoring and in vivo bioimaging applications for the detection of biomarkers in various diseases states.