Smart paper-based chip sensor based on Mn-CeO₂@ persistent-luminescence nanomaterials for tri-modality detection of sarcosine

First synthesis of Mn-CeO 2 @ZnGa₂O₄:Cr³⁺, Eu³⁺ composite. • Trimodal sarcosine detection using phosphorescence, peroxidase mimicry, and photothermal TMB. • Smartphone-based mobile tool enables on-site sarcosine detection. • Paper-based chip sensor simplifies sarcosine detection, making it facile and convenient. Prostate cancer (PCa) is the second most common cancer in men, while sarcosine levels have profound implications for the state of prostate cancer. Herein, we have designed a smart paper-chip sensor based on Mn-CeO₂ nanozyme@persistent luminescent nanoparticles (PLNPs) for trimodality fluorescence, colorimetric, and photothermal detection of sarcosine. The PLNPs were prepared as ZnGa₂O₄: 0.5% Cr 3+ , 1.5% Eu 3+ and then integrating Mn-CeO₂ nanozyme. The composite was integrated onto a polypropylene (PP) substrate as the paper chip. In pa1rticular, PLNPs exhibited the afterglow emission for eliminating the interference from the autofluorescence of biological samples; In the presence of both sarcosine and sarcosine oxidase, red phosphorescence is restored, for phosphorescence detection. The nanozyme of Mn-doped CeO₂ exhibit enhanced peroxidase activity, rapidly converting colorless 3,3′,5,5′-tetramethylbenzidine (TMB) into a blue form as oxidized TMB, which also possesses photothermal conversion capabilities, enabling both colorimetric and photothermal detection. Using a smartphone, this sensor enables on-site detection of sarcosine in serum with a detection range of 0–10 μM with extremely low limits of detection (LOD) as 1.88 μM for fluorescence; 0.08 μM for colorimetry; and 1.88 μM for photothermal mode, with all RSD below 5%. Overall, we have successfully designed for the detection of sarcosine in serum. The sensor's low cost, high sensitivity, and portability have been validated, thereby improving treatment success rates and survival rates for patients with early-stage prostate cancer. Scheme 1. Schematic illustration of a smartphone-based Mn-CeO₂@persistent luminescence nanoparticles (PLNPs) paper-based sensor for triple-mode detection of sarcosine. ZnGa₂O₄: Cr 3+ , Eu 3+ (ZCEGO) was fabricated as PLNPs featuring red emission at 700 nm. The PLNPs were surface-functionalized with Mn-CeO₂ nanozymes as peroxidase mimics, and the resultant nanocomposite was further incorporated onto a paper-based substrate. In the presence of sarcosine and sarcosine oxidase (SOX), H₂O₂ is generated. In Zone 1 (yellow section), the PLNPs are exposed, enabling phosphorescence detection. Meanwhile, in the presence of TMB, TMB in Zone 2 (white section) is oxidized to oxTMB, enabling colorimetric detection. The oxTMB can be used for photothermal detection upon irradiation with an 808 nm laser. Quantitative analysis of sarcosine is achieved using a smartphone. Download: Download high-res image (102KB) Download: Download full-size image