Reversible Ratiometric NADH Sensing Using Semiconducting Polymer Dots

Abstract

Reduced nicotinamide adenine dinucleotide (NADH) is a key coenzyme in living cells due to its role as an electron carrier in redox reactions, and its concentration is an important indicator of cell metabolic state. Abnormal NADH levels are associated with age‐related metabolic diseases and neurodegenerative disorders, creating a demand for a simple, rapid analytical method for point‐of‐care NADH sensing. Here we develop a series of NADH‐sensitive semiconducting polymer dots (Pdots) as nanoprobes for NADH measurement, and test their performance in vitro and in vivo. NADH sensing is based on electron transfer from semiconducting polymer chains in the Pdot to NADH upon UV excitation, quenching Pdot fluorescence emission. In polyfluorene‐based Pdots, this mechanism resulted in an on‐off NADH sensor; in DPA‐CNPPV Pdots, UV excitation resulted in NADH‐sensitive emission at two wavelengths, enabling ratiometric detection. Ratiometric NADH detection using DPA‐CNPPV Pdots exhibits high sensitivity (3.1 μM limit of detection), excellent selectivity versus other analytes, reversibility, and a fast response (less than 5 s). We demonstrate applications of the ratiometric NADH‐sensing Pdots including smartphone‐based NADH imaging for point‐of‐care use.

Conjugated polymer-based luminescent probes for ratiometric detection of biomolecules

“…112,113 Besides, the design principles of oxygen-sensitive probes have been further employed in the ratiometric measurement and sensing of tyrosinase activity 114 and NADH. 115,116…”

Biomimetic semiconducting polymer dots for highly specific NIR-II fluorescence imaging of glioma

“…There is a great interest in developing novel semiconducting polymers for biomedical applications [ 45 , 46 ]. The band gap of semiconducting polymers can be effectively tuned by a design approach through donor-acceptor (D-A) interactions ( Fig.…”

Nanomaterials‐assisted metabolic analysis toward in vitro diagnostics

“…For fluorescence detection, metabolic signals are measured by spectrum variation, with nanomaterials serving as a contributor in fluorescence quenching and enhancement. [ 64,65 ] In particular, QDs [ 66–70 ] as zero‐dimensional (0D) nanomaterials have been explored as the fluorescence probes due to the unique FRET process, stable photoluminescence, and biocompatibility. [ 71 ] A typical fluorescence‐based metabolite sensing process with the introduction of nanomaterials is illustrated in Figure 4A.…”

“…combined the NAD(P)H‐sensitive polymer dots (Pdots) with the metabolite‐specific NAD(P)H‐dependent enzyme (Figure 4B). [ 65 ] Under ultraviolet (UV) illumination, the NAD(P)H generated from the metabolite oxidation led to the fluorescence quenching emitted at 627 nm and fluoresced at 458 nm by Pdots. The ratio of blue‐to‐red channel emission intensities was further applied for detecting and quantifying the phenylalanine with LOD of 3.5 µmol.…”