A dual-functional single-atom Fe nanozyme-based sensitive colorimetric sensor for tannins quantification in brandy

Traditional methods of tannins detection suffer from complex pretreatment, long detection time, and limited sensitivity. Modern techniques like liquid chromatography require expertise, involve tedious result processing, and lack effective data visualization. Therefore, there is a need for an alternative detection method that simplifies pretreatment and detection steps, reduces analysis time, and provides visualized results. In this study, a novel colorimetric sensor based on single-atom Fe nanozyme (Fe@CN-20) was developed for tannins detection. Fe@CN-20 exhibited laccase-like and oxidase-like activities, enabling simultaneous oxidation of tannins and a substrate called TMB. Tannins competed with TMB, allowing quantification of tannins content. The Fe@CN-20/TMB system provided a detection range of 5-100 mg/L tannic acid, with a detection limit of 0.13 mg/L (S/N = 3). Analysis time was approximately 30 min. The platform successfully quantified tannins in brandy, showing less than 5% deviation compared to the standard method. The sensor was simple, sensitive, rapid, and provided strong visualization.

Bioadhesive injectable hydrogel with phenolic carbon quantum dot supported Pd single atom nanozymes as a localized immunomodulation niche for cancer catalytic immunotherapy

Immunotherapy is a powerful way to treat cancer, however, systemic treatment-associated adverse effects remain a major concern. In this study, a bioadhesive injectable hydrogel is developed to provide localized immune niches for tumor microenvironment immunomodulation and cancer catalytic immunotherapy. First, a phenolic single atom nanozyme (SAN) was developed by in situ synthesis of Pd single atom on catechol-grafted carbon-quantum-dot (DA-CQD@Pd) templates. Then, the bioadhesive injectable hydrogel consisting of DA-CQD@Pd SAN and immune adjuvant CpGODN was formed through SAN-catalyzed free-radical polymerization. The SAN exhibited peroxidase-like activity to generate ROS and kill tumor cells through catalytic therapy. The hydrogel locally released CpGODN in a sustained manner, which limited the risk of systemic exposure, reducing the impact of CpGODN toxicity, and protecting CpGODN from degradation. The bioadhesive hydrogel immobilized around solid tumor to provide an immune response site after injection. When combined it with the administration of immune checkpoint inhibitor anti-PD-L1, the hydrogel realized localized immunomodulation, maximized therapeutic efficacy and prevents tumor metastasis via a catalytic immunotherapy.

Peroxidase-like activity of Fe-N-C single-atom nanozyme based colorimetric detection of galactose

Single atom nanozymes are the artificial enzymes with enzyme-like activity, which have attracted a great deal attention in recent years due to their unique merits such as remarkable stability, excellent atom utilization and low cost. Herein, a convenient and sensitive colorimetric strategy was developed for the sensing of galactose based on Fe-N-C single-atom nanozyme (Fe-SAzyme). The Fe-SAzyme was prepared through "isolation-pyrolysis" method that exhibited intrinsic peroxidase mimicking activity, which can quickly catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to produce blue-colored oxTMB in the presence of hydrogen peroxide (H₂O₂). Galactose can be oxidized by galactose oxidase (Gal Ox) to generate H₂O₂, and Fe-SAzyme can be utilized for quantitative colorimetric detection of galactose. A good linearity between absorbance and the galactose concentration in the range of 50-500 μM was obtained with a detection limit of (LOD) 10 μM. The Fe-SAzyme based colorimetric strategy offered a rapid, convenient and economic way for galactose quantification detection, which could be used as an alternative method for galactosemia diagnosis.