Developing reliable and facile approaches for alkaline phosphatase (ALP) sensing is important due to its role as a clinical biomarker for many diseases. In this study, we proposed a new and convenient colorimetric assay based on the pyrophosphate (PPi)-mediated oxidase-mimicking activity switching of nanosized MnFe 2 O 4 for the detection of ALP. The synthesized MnFe 2 O 4 exhibited high oxidase-like activity to catalyze the oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to its blue product TMBox in the presence of dissolved O 2 , leading to a color reaction rapidly and remarkably; PPi could significantly inhibit the activity of the MnFe 2 O 4 nanozyme via the strong interaction between PPi and the Fe(III) species in MnFe 2 O 4 , resulting in the suppression of the TMB color reaction; when ALP was added, it hydrolyzed the PPi substrate to phosphate (Pi) that had no obvious effect on the MnFe 2 O 4 activity, and such that the TMB color reaction catalyzed by the nanozyme could be observed again. With the above principle, linear colorimetric determination of ALP in the scope of 0.6–55 U L −1 was achieved, giving the limit of detection down to 0.27 U L −1 . Besides, the developed assay could provide selective response toward ALP against other co-existing biological species. Furthermore, reliable detection of ALP in human serum samples was verified by our assay, revealing its great promise as an effective and facile tool for ALP monitoring in clinical practice.
Yao Yu,Xiaolei Liu,Ning Xu,Lin Li,Yaming Yang,Mingyuan Liu,Lianjing Zhao,Xue Bai
Immunoassays are the primary method used for detection of foodborne parasitic infection. The nanomaterials used in these assays often present challenges such as complex preparation requirements and low stability during long-term storage and transport. Herein, based on cost-effective K 3 [Fe(CN) 6 ]-mediated in-situ generated CuFe Prussian blue analogues (CuFe-PBA) and quinoxaline derivatives with high fluorescence, a dual-mode immunoassay was proposed for foodborne parasitic infection. This platform is relied on the restoration of K 3 [Fe(CN) 6 ] by ascorbic acid (AA). In addition to this process, K 4 [Fe(CN) 6 ]-triggered the generation of CuFe-PBA, and the enhanced fluorogenic reaction of dehydrogenated AA and o -phenylenediamine (OPD) occur sequentially. Without complex probes preparation, the assay enabled the rapid on-site detection of ALP and foodborne parasitic infection through a colorimetric mode accessible via smartphone and offered enhanced sensitivity through a fluorescent mode. The method was used for the detection of ALP, achieving detection limits of 0.38 U/L and 0.03 U/L for colorimetric and fluorescence modes, respectively. Subsequently, the dual-mode immunoassay was applied to Trichinella spiralis infection. The sensitivity and specificity of both the colorimetric and fluorescence modes were 100 % in 950 pig serum samples. This immunosensor provides a universal analysis tool for the accurate, cost-effective and highly sensitive detection of foodborne parasitic infection.
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