α-Ketoglutaric
acid (α-KA) is an important endogenous
metabolite in the Krebs cycle and considered a critical marker for
various diseases. Several approaches for identifying α-KA have
been reported. However, most of them are limited to single-signal
transduction modes in one assay and working in the suspension state,
which easily cause quantification errors and lead to false-positive
detection results. Herein, a multivalue-responsive and semi-solid
EuMOF-gel (EuMOG) logic biosensor is first designed and fabricated,
which can realize the specific, rapid, and easy-to-differentiate naked-eye
detection of the disease-associated marker of α-KA in serum
through implementing one-to-two logic operation with three multicolor
gates. The implementation of one-to-two logic operation can be rationally
achieved by assembling 2,6-naphthalenedicarboxylic acid as both the
energy donor and blue-colored output 1, photoactive Eu3+ ions as the red-emissive output 2, and α-KA stimuli as an
input and energy blocker between the dual spectrum-resolved outputs
into one unit. With the specific input of α-KA among various
analytes, the binary code of the logic decoder switches from (0,1)
to (1,0) with an obvious color change from red to cyan. Moreover,
by integrating the output chromaticity into the logical operations,
the concentration levels of α-KA could be easily evaluated with
the intelligent EuMOG detector, which has three multicolor gates in
parallel encoding low (0,1), normal (1,1), and danger (1,0) statuses.
Such multivalued logic biosensor provides a facile strategy to improve
the analysis reliability of disease-associated biomarkers.