Osteoarthritis (OA) is the most common degenerative joint disease and a major cause of pain and disability in adult individuals. The etiology of OA includes joint injury, obesity, aging, and heredity. However, the detailed molecular mechanisms of OA initiation and progression remain poorly understood and, currently, there are no interventions available to restore degraded cartilage or decelerate disease progression. The diathrodial joint is a complicated organ and its function is to bear weight, perform physical activity and exhibit a joint-specific range of motion during movement. During OA development, the entire joint organ is affected, including articular cartilage, subchondral bone, synovial tissue and meniscus. A full understanding of the pathological mechanism of OA development relies on the discovery of the interplaying mechanisms among different OA symptoms, including articular cartilage degradation, osteophyte formation, subchondral sclerosis and synovial hyperplasia, and the signaling pathway(s) controlling these pathological processes.

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The evolution of photoelectrochemical (PEC) bioanalysis has resulted in substantial progress in its analytical performance and biodetection applications. The aim of this review is to provide a panoramic snapshot of the state of the art in this dynamically developing field, with special emphasis on PEC DNA analysis, immunoassay, enzymatic biosensing and cell-related detection. The future prospects in this area are also evaluated and discussed. This work will serve as a useful source to inform the interested audience of the latest developments and applications in the field of PEC bioanalysis.

Interactions between surface plasmons (SP) of metallic surfaces and photoluminescence (PL) of semiconductor nanocrystal (S-NC) surfaces have been extensively investigated, and SP-induced PL enhancement has been used as a sensitive analytical technique. However, this SP induced electrochemiluminescence (ECL) enhancement is rarely studied. In this work, we report greatly enhanced ECL of CdS thin films by gold nanoparticles (Au NPs) for ultrasensitive detection of thrombin. The system was composed of a CdS NC film on glassy carbon electrode (GCE) as ECL emitter attached an aptamer of thrombin. Then, ssDNA-AuNP conjugates hybridized with the aptamer to form a separation length of ca. 12 nm between CdS NCs and Au NPs. The system showed 5-fold enhancement of ECL intensity as compared to that without Au NPs, which might be attributed to the long-distance interaction between the S-NCs and SPR field of noble metal nanoparticles (MNPs).We also found that the enhanced ECL could be influenced by the involving factors such as the separation distance, spectral overlap, and magnetic field. Such enhancement in combination with smart recognition of aptamer and target protein allowed us to construct an ultrasensitive aptasensor for attomolar detection of thrombin. The presence of target protein was reflected by the ECL signal decrease caused by the target-induced removal of ssDNA-AuNP conjugates. The decrease of ECL signal was logarithmically linear with the concentration of thrombin in a wide range from 100 aM to 100 fM. The principle described in this work could be also applied to many other bioassays.

In this Feature, electrochemiluminescent (ECL) and photoelectrochemical (PEC) properties and mechanisms of semiconductor quantum dots (QDs) are reviewed, with emphasis on their specific fundamentals and concise comparison on their similarities and differences. With recent illustrative examples of bioanalytical applications, the main signaling strategies for QDs-based ECL and PEC bioanalysis are then highlighted. The future prospects in this field are also discussed.

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With DNA as a rigid spacer, Ag nanoparticles (NPs) were bridged to CdS quantum dots (QDs) for the stimulation of exciton-plasmon interactions (EPI) in a photoelectrochemical (PEC) system. Due to their natural absorption overlap, the exciton of the QDs and the plasmon of Ag NPs could be induced simultaneously. The EPI resonant nature enabled manipulating photoresponse of the QDs via tuning interparticle distances. Specifically, the photocurrent of the QDs could be greatly attenuated and even be completely damped by the generated EPI. The work opens a different horizon for EPI investigation through an engineered PEC nanosystem, and provides a viable mechanism for new DNA sensing protocol.

Herein we demonstrate the protocol of a biocatalytic precipitation (BCP)-based sandwich photoelectrochemical (PEC) horseradish peroxidase (HRP)-linked immunoassay on the basis of their synergy effect for the ultrasensitive detection of mouse IgG (antigen, Ag) as a model protein. The hybrid film consisting of oppositely charged polyelectrolytes and CdS quantum dots (QDs) is developed by the classic layer by layer (LbL) method and then employed as the photoactive antibody (Ab) immobilization matrix for the subsequent sandwich-type Ab-Ag affinity interactions. Improved sensitivity is achieved through using the bioconjugates of HRP-secondary antibodies (Ab(2)). In addition to the much enhanced steric hindrance compared with the original one, the presence of HRP would further stimulate the BCP onto the electrode surface for signal amplification, concomitant to a competitive nonproductive absorption that lowers the photocurrent intensity. As a result of the multisignal amplification in this HRP catalyzed BCP-based PEC immunoassay, it possesses excellent analytical performance. The antigen could be detected from 0.5 pg/mL to 5.0 ng/mL with a detection limit of 0.5 pg/mL.