Programmable Y-Shaped Probes with Proximity Bivalent Recognition for Rapid Electrochemiluminescence Response of Acute Myocardial Infarction

Photoelectrochemical immunoassay of cardiac troponin I based on ZnTCPP/CdIn2S4 type-II heterojunction and co-catalyzed precipitation biolabeling

CdIn2S4 and zinc tetrakis(4-carboxyphenyl)porphyrin (ZnTCPP) were synthesized by hydrothermal method, and an organic dye-sensitized inorganic semiconductor ZnTCPP/CdIn2S4 type II heterojunction was constructed on a fluorine-doped tin oxide (FTO) substrate electrode. A sandwich immunostructure for signal-attenuation photoelectrochemical (PEC) detection of cardiac troponin I (cTnI) was constructed using the ZnTCPP/CdIn2S4/FTO photoanode and a horseradish peroxidase (HRP)-ZnFe2O4-Ab2-bovine serum albumin (BSA) immunolabeling complex. The bioenzyme HRP and the HRP-like nanozyme ZnFe2O4 can co-catalyze the oxidation of 4-chloro-1-naphthol (4-CN) by H2O2 to produce an insoluble precipitate on the photoanode, thus notably reducing the anodic photocurrent for quantitative determination of cTnI. Under the optimal conditions, the photocurrent at 0 V vs. SCE in 0.1 M phosphate buffer solution (pH 7.40) containing 0.1 M ascorbic acid was linear with the logarithm of cTnI concentration from 500 fg mL-1 to 50.0 ng mL-1, and the limit of detection (LOD, S/N = 3) is 0.15 pg mL-1. Spiked recoveries were 95.1% ~ 104% for assay of cTnI in human serum samples.

Molecularly imprinted electrochemiluminescence sensor based on a novel luminol derivative for detection of human serum albumin via click reaction

A novel luminol derivative of N-(1,4-dioxo-1,2,3,4-tetrahydrophthalazin-5-yl)acrylamide (DTA) with excellent luminescence efficiency was designed and synthesized. Furthermore, a molecularly imprinted electrochemiluminescence sensor (MIECLS) was fabricated to detect ultratrace levels of human serum albumin (HSA) with high sensitivity and selectivity via a click reaction. The molecularly imprinted polymers (MIPs) were formed on the electrode surface via electropolymerization with HSA as a template molecule and catechol as a monomer. In the detection process, the -SH group of HSA on the electrode and the C = C bond of acryloyl group in DTA formed a new C-S bond via the Michael addition reaction to construct the MIECLS. The higher the concentration of HSA, the greater electrochemiluminescence (ECL) intensity measured. Taking advantage of MIECLS for ECL detection (scanning potential, - 0.4 to 0.5 V), there was a good linear relationship between ECL intensity and the logarithm of HSA concentration in the range 5 × 10-9 to 1 × 10-13 mg mL-1. The limit of detection (LOD) of the sensor was 1.05 × 10-15 mg mL-1. The sensor exhibited outstanding selectivity and stability. The sensor was applied to detect HSA in human serum with good recoveries of 97.7-105.2%. The concentration of HSA was detected by electrochemical method using the gating effect of MIP.

Identifying tumor cell-released extracellular vesicles as biomarkers for breast cancer diagnosis by a three-dimensional hydrogel-based electrochemical immunosensor

Tumor cell-released LC3+ extracellular vesicles (LC3+ EVs) participate in immunosuppression during autophagy and contribute to the occurrence and development of breast cancer. In view of the strong association between the LC3+ EVs and breast cancer, developing an effective strategy for the quantitative detection of LC3+ EVs levels with high sensitivity to identify LC3+ EVs as new biomarkers for accurate diagnosis of breast cancer is crucial, but yet not been reported. Herein, an ultrasensitive electrochemical immunosensor is presented for the quantitative determination of LC3+ EVs using a three-dimensional graphene oxide hydrogel-methylene blue composite as a redox probe, showing a low detection limit and a wide linear range. With this immunosensor, the expression levels of LC3+ EVs in various practical sample groups including different cancer cell lines, the peripheral blood of tumor-bearing mice before and after immunotherapy, and the peripheral blood from breast cancer patients with different subtypes and stages were clearly distinguished. This study demonstrated that LC3+ EVs were superior as biomarkers for the accurate diagnosis of breast cancer compared to traditional biomarkers, particularly for cancer subtype discrimination. This work would provide a new noninvasive detection tool for the early diagnosis and prognosis assessment of breast cancer in clinics.

Bifunctional TiO2 Nanoflower-Induced H4TCBPE Aggregation Enhanced Electrochemiluminescence for an Ultrasensitive Assay of Organophosphorus

In this work, the aggregation-induced emission ligand 1,1,2,2-tetra(4-carboxylbiphenyl)ethylene (H4TCBPE) was rigidified in the Ti-O network to form novel electrochemiluminescence (ECL) emitter H4TCBPE-TiO2 nanospheres, which acted as an effective ECL emitter to construct an "on-off" ECL biosensor for ultrasensitive detection of malathion (Mal). H4TCBPE-TiO2 exhibited excellent ECL responses due to the Ti-O network that can restrict the intramolecular free motions within H4TCBPE and then reduce the nonradiative relaxation. Moreover, TiO2 can act as an ECL co-reaction accelerator to promote the generation of sulfate radical anion (SO4•-), which interacts with H4TCBPE in the Ti-O network to produce enhanced ECL response. In the presence of Mal, numerous ligated probes (probe 1 to probe 2, P1-P2) were formed and released by copper-free click nucleic acid ligation reaction, which then hybridized with hairpin probe 1 (H1)-modified H4TCBPE-TiO2-based electrode surface. The P1-P2 probes can initiate the target-assisted terminal deoxynucleoside transferase (TdTase) extended reaction to produce long tails of deoxyadenine with abundant biotin, which can load numerous streptavidin-functionalized ferrocenedicarboxylic acid polymer (SA-PFc), causing quenching of the ECL signal. Thus, the ultrasensitive ECL biosensor based on H4TCBPE-TiO2 ECL emitter and click chemistry-actuated TdTase amplification strategy presents a desirable range from 0.001 to 100 ng/mL and a detection limit low to 9.9 fg/mL. Overall, this work has paved an avenue for the development of novel ECL emitters, which has opened up new prospects for ECL biosensing.

MOF-Enhanced Chiral ECL Recognition System: Dual-Function in Phenylalanine Enantiomer Detection and Coreaction Acceleration

The accurate discernment and separation of chiral isomers with high precision remain a significant challenge in various industries and biological fields. In this investigation, an electrochemiluminescent (ECL) chiral recognition platform was devised to ascertain the presence of phenylalanine (Phe). Notably, a homochiral [Ni2(l-asp)2(bipy)] (Ni-LAB) was established as a dual-function coreactant accelerator and chiral recognition substrate. Ni-LAB facilitates the reaction between the coreactant (K2S2O8) and the luminescent entity 3,4,9,10-perylenetetracar-boxylic-l-cysteine (PTCA-cys), thereby enhancing the ECL luminescence efficiency and improving the sensitivity of the chiral sensor. The chiral recognition potential of Ni-LAB was assessed to differentiate between Phe chiral isomers, and the underlying mechanism was comprehensively elucidated. This system exhibited remarkable proficiency in detecting Phe enantiomers and precisely differentiating a single Phe enantiomer within a mixture, showcasing exceptional levels of selectivity, stability, and reproducibility. This study paves the way for the development of advanced chiral recognition systems, potentially revolutionizing the field of chiral sensing and discrimination.

Aggregation-Induced Electrochemiluminescence Based on a Zinc-Based Metal-Organic Framework and a Double Quencher Au@UiO-66-NH2 for the Sensitive Detection of Amyloid β 42 via Resonance Energy Transfer

A novel sandwich electrochemiluminescence (ECL) biosensor based on aggregation-induced electrochemiluminescence resonance energy transfer (AIECL-RET) was designed for the sensitive detection of amyloid β42 (Aβ42). The synthesized silver nanoparticle-functionalized zinc metal-organic framework (Ag@ZnPTC) and gold nanoparticle-functionalized zirconium organic framework (Au@UiO-66-NH₂) were used as the ECL donor and acceptor, respectively. AgNPs were generated in situ on the surface of ZnPTC, which further improved the ECL intensity and the loading of antibody 1 (Ab1). Under the optimized experimental conditions, the linear detection range of Aβ42 concentration was 10 fg/mL to 100 ng/mL, and the detection limit was 2.4 fg/mL (S/N = 3). The recoveries of Aβ42 were 99.5-104%. The method has good stability, repeatability, and specificity. Ag@ZnPTC/Au@UiO-66-NH₂ provides an assay for the sensitive detection of disease biomarkers.