A Supramolecular Biosensor for Rapid and High-Throughput Quantification of a Disease-Associated Niacin Metabolite

Metabolic abnormalities play a pivotal role in various
pathological
conditions, necessitating the quantification of specific metabolites
for diagnosis. While mass spectrometry remains the primary method
for metabolite measurement, its limited throughput underscores the
need for biosensors capable of rapid detection. Previously, we reported
that pillar[6]arene with 12 carboxylate groups (P6AC) forms host–guest
complexes with 1-methylnicotinamide (1-MNA), which is produced in
vivo by nicotinamide N-methyltransferase (NNMT).
P6AC acts as a biosensor by measuring the fluorescence quenching caused
by photoinduced electron transfer upon 1-MNA binding. However, the
low sensitivity of P6AC makes it impractical for detecting 1-MNA in
unpurified biological samples. In this study, we found that P6A with
12 sulfonate groups (P6AS) is a specific and potent supramolecular
host for 1-MNA interactions even in biological samples. The 1-MNA
binding affinity of P6AS in water was found to be (5.68 ± 1.02)
× 106 M–1, which is approximately
700-fold higher than that of P6AC. Moreover, the 1-MNA detection limit
of P6AS was determined to be 2.84 × 10–7 M,
which is substantially lower than that of P6AC. Direct addition of
P6AS to culture medium was sufficient to quantify 1-MNA produced by
cancer cells. Furthermore, this sensor was able to specifically detect
1-MNA even in unpurified human urine. P6AS therefore enables rapid
and high-throughput quantification of 1-MNA, and further improvement
of our strategy will contribute to the establishment of high-throughput
screening of NNMT inhibitors, diagnosis of liver diseases, and imaging
of human cancer cells in vivo.