In situ electrostatic assembly of porphyrin as enhanced PEC photosensitizer for bioassay of single HCT-116 cells via competitive reaction

Innovations in aptamer-based biosensors for detection of pathogenic bacteria: Recent advances and perspective

The rapid and accurate detection of pathogenic bacteria is a pressing concern in the fields of public health, food safety, and environmental monitoring. However, traditional methods often prove to be slow and difficult to quantify accurately. Thus, there is a pressing need to develop advanced methods that enable rapid detection which is sensitive and inexpensive. Aptamers, which are short nucleic acid sequences derived through a process called systematic evolution of ligands by exponential enrichment (SELEX), offer a promising alternative due to their unique binding characteristics. These properties confer several advantages over traditional antibodies, making aptamers effective and versatile bioreceptors for pathogen detection. Recent advancements have led to the development of various aptamer-based biosensors utilizing diverse signaling strategies, including optical, electrochemical, mass-based, paper-based and microchip capillary electrophoresis (MCE) methods. The integration of nanomaterials with aptamer technology has further enhanced biosensor performance by improving sensitivity and enabling real-time monitoring of bacterial contamination. In this review, the focus is on current developments in aptamer-based biosensors and their potential applications in clinical diagnostics, food safety and environmental monitoring. As research progresses, the customization of aptamer sequences for specific targets is expected to yield tailored diagnostic solutions, ultimately improving patient outcomes and public health responses. The continued exploration of aptamer technology marks a significant advancement in methodologies for detecting pathogenic bacteria, highlighting not only the promise of aptamers as effective detection tools but also the critical need for multidisciplinary collaboration, integrating molecular biology, materials science, and microfluidics, to overcome challenges in this field.

Porphyrin-Based Metal-Organic Frameworks for PD-L1 Detection via "Coordination Disaggregation-Induced Enhancement" Strategy

Porphyrins, known for their exceptional photoelectrochemical properties and high luminescence, are promising candidates for electrochemiluminescence (ECL) applications. However, their tendency to aggregate in aqueous solutions due to π-π stacking leads to luminescence quenching and reduced efficiency. To address this, we developed a "coordination disaggregation-induced enhancement" strategy, utilizing metal-organic frameworks (MOFs) as stable platforms for immobilizing porphyrin. These porphyrin-based MOFs not only increase the loading of luminescent groups and suppress the aggregation-caused quenching (ACQ) effect but also enhance electron transfer via uniform dispersion of pyrrole N in the porphyrin ligand, thereby improving ECL intensity. Additionally, they exhibit favorable biocompatibility and low toxicity, making them suitable for biomedical applications. By combining porphyrin-based MOFs as donors with PDA@MnO2 composites as quenchers, we constructed a quenching-type ECL immunosensor for detecting programmed death ligand 1 (PD-L1). This sensor achieves a detection range of 10 fg/mL to 100 ng/mL, with a limit of detection as low as 2.48 fg/mL, which demonstrates great potential for highly sensitive biomarker detection and promising applications in early cancer diagnosis and other medical diagnostics.

Operando Photoelectrochemical Surface-Enhanced Raman Spectroscopy: Interfacial Mechanistic Insights and Simultaneous Detection of Patulin

Comprehending the biosensing mechanism of the biosensor interface is crucial for sensor development, yet accurately reflecting interfacial interactions within actual detection environments remains an unsolved challenge. An operando photoelectrochemical surface-enhanced Raman spectroscopy (PEC-SERS) biosensing platform was developed, capable of simultaneously capturing photocurrent and SERS signals, allowing operando characterization of the interfacial biosensing behavior. Porphyrin-based MOFs (Zr-MOF) served as bifunctional nanotags, providing a photocurrent and stable Raman signal output under 532 nm laser irradiation. Aptamer was used to bridge the Zr-MOF and the silver-encased gold nanodumbbells (AuNDs@AgNPs). The simultaneous in situ acquisition of target-induced PEC and SERS signal responses facilitated the correlation of electron transfer information from the photocurrent with the distance information from the SERS signal. It revealed the biosensing mechanism in which target-induced aptamer conformational bending drove the Zr-MOF to approach the electrode. However, the increase in charge transfer observed through conventional electrochemical methods contradicts the conclusions drawn from the operando PEC-SERS analysis. Comprehensive analysis indicated that redox probes introduced during the non-in-situ measurement process became adsorbed within the MOF pores, potentially affecting the judgment of the biosensing mechanism. In addition, the operando PEC-SERS biosensor simultaneously obtained two independent signals, providing self-verification to improve the accuracy and reliability of patulin detection. The linear ranges were 1 pg mL-1-10 ng mL-1 for the PEC method and 1 pg mL-1-100 ng mL-1 for the SERS method, respectively. This work provides a powerful tool for determining the interface characteristics of biosensors.

Multipath collaboration-based signal amplification on Z-scheme In2O3/g-C3N4 heterojunction photoelectrode for sensitive photoelectrochemical immunoassay

The ideal photoelectrode and efficient signaling strategy are pivotal to achieve sensitive photoelectrochemical (PEC) analysis. Here, a multipath collaborative signal amplification-based PEC immunosensor was constructed for the ultrasensitive detection of cytokeratin 19 fragment 21-1. Specifically, the photoelectrode fabricated by Z-scheme In2O3/g-C3N4 heterojunction showed enhanced photocurrent intensity in response to visible light. Meanwhile, the signal probe, horseradish peroxidase functionalized dopamine-melanin nanosphere@Au nanoparticles (HRP-Dpa-melanin NS@AuNPs), were introduced into the system. When the target exists, the signal probe can induce multiple quenching of the photocurrent due to the competition of light absorption, steric hindrance and HRP-mediated biocatalytic precipitation, which effectively inhibit light, electron donor, and electron access to the photoelectrode. The fabricated immunosensor exhibits a wide linear range from 1.0 × 10-3 - 1.0 × 102 ng mL-1 with the detection limit of 0.35 pg mL-1 (S/N = 3) for cytokeratin 19 fragment 21-1 detection. The study enhances sensitivity for PEC detection by utilizing the superior Z-scheme heterojunction photoelectrode, providing a valuable method that combines multiple signal pathways for a synergistic effect in bioanalysis.