An alkaline phosphatase-induced immunosensor for SARS-CoV-2 N protein and cardiac troponin I based on the in situ fluorogenic self-assembly between N-heterocyclic boronic acids and alizarin red S

A sensitive electrochemical biosensor based on Pd@PdPtCo mesoporous nanopolyhedras as signal amplifiers for assay of cardiac troponin I

Cardiac troponin I (cTnI) has been widely used in clinical diagnosis of acute myocardial infarction (AMI). Herein, a sensitive electrochemical biosensor for cTnI analysis was designed, in which the simple synthesized Pd@PdPtCo mesoporous nanopolyhedras (MNPs) were utilized as signal amplifiers. The mesoporous polyhedral structure of Pd@PdPtCo MNPs endows them with more specific surface area and more active sites, as well as the synergistic effect between multiple metal elements, all of which increase the electrocatalytic performance of Pd@PdPtCo MNPs in efficiently oxidizing hydroquinone (HQ) to benzoquinone (BQ). Experimental results showed that Pd@PdPtCo MNPs had better performance in oxidation of HQ to BQ compared with their corresponding monometallic and bimetallic nanomaterials. With the aid of the interaction between antigens and antibodies, the peak current of HQ to BQ showed an upward trend with increasing concentration of cTnI, thus the quantitative detection of cTnI could be achieved. Under optimal conditions, the biosensor prepared in this work has a wider linear range (1.0 × 10-4-200 ng mL-1) and a lower detection limit (0.031 pg mL-1) than other sensors reported in literatures, coupled by good stability and high sensitivity. More importantly, it also performed well in complex serum environment, proving that the electrochemical sensor has a practical application potential in this field.

An in situ ratiometric fluorescence immunosensor via Mn2+-triggered aggregation-induced emission transformation of levodopa fluorescent copolymer nanoparticles

Herein, a direct in situ alkaline phosphatase (ALP)-labeled luminescent nanoimmunoassay platform was constructed using Mn2+-triggered aggregation-induced emission transformation of levodopa fluorescent copolymer (LFC) nanoparticles. Using cardiac troponin I (cTn I) as the model antigen, the proposed nanoimmunosensor has been applied to detect cTn I in clinical samples with satisfactory results.

Europium nanospheres based ultrasensitive fluorescence immunosensor for aflatoxin B1 determination in feed

In this work, a new competitive immunosensor for aflatoxin B1 (AFB1) detection was developed using europium (Eu) fluorescent nanospheres and magnetic beads. Firstly, Eu nanospheres were synthesized through two steps including carboxylated polystyrene nanospheres and Eu-doped polystyrene nanospheres preparation. Then Eu nanospheres were covalently tagged to anti-AFB1 monoclonal antibody (anti-AFB1 mAb) through an EDC coupling method. Carboxylated Fe3O4 magnetic beads were conjugated to AFB1-BSA through EDC/NHS crosslinking to obtain AFB1-BSA-Fe3O4. In the absence of AFB1, Eu-anti-AFB1 mAb were incubated with AFB1-BSA-Fe3O4 to form Eu-anti-AFB1 mAb-AFB1-BSA-Fe3O4 in PBS buffer. However, in the presence of AFB1, the competitive interaction of AFB1 and AFB1-BSA-Fe3O4 to bind with Eu-anti-AFB1 mAb occurred. With the increasing concentration of AFB1, less Eu-anti-AFB1 mAb-AFB1-BSA-Fe3O4 formed. So the fluorescence intensity of Eu-anti-AFB1 mAb-AFB1-BSA-Fe3O4 was gradually decreased after magnetic separation. The degree of fluorescence decrease was linear with respect to the logarithm of AFB1 concentration in the range of 0.01-2 ng/mL in both buffer solution and feed samples and the detection limit was 0.003 ng/mL. What's more, the immunosensor showed excellent specificity for AFB1 without being interfered by other mycotoxins. In consideration of the excellent performance of this immunosensor, we can speculate that the proposed method could be widely used in detecting food contaminants.

Overview on the Development of Alkaline-Phosphatase-Linked Optical Immunoassays

The drive to achieve ultrasensitive target detection with exceptional efficiency and accuracy requires the advancement of immunoassays. Optical immunoassays have demonstrated significant potential in clinical diagnosis, food safety, environmental protection, and other fields. Through the innovative and feasible combination of enzyme catalysis and optical immunoassays, notable progress has been made in enhancing analytical performances. Among the kinds of reporter enzymes, alkaline phosphatase (ALP) stands out due to its high catalytic activity, elevated turnover number, and broad substrate specificity, rendering it an excellent candidate for the development of various immunoassays. This review provides a systematic evaluation of the advancements in optical immunoassays by employing ALP as the signal label, encompassing fluorescence, colorimetry, chemiluminescence, and surface-enhanced Raman scattering. Particular emphasis is placed on the fundamental signal amplification strategies employed in ALP-linked immunoassays. Furthermore, this work briefly discusses the proposed solutions and challenges that need to be addressed to further enhance the performances of ALP-linked immunoassays.