Ultrasensitive fluorescence microRNA biosensor by coupling hybridization-initiated exonuclease I protection and tyramine signal amplification.

Tyramine signal amplification (TSA) has made its mark in immunoassay due to its excellent signal amplification ability and short reaction time, but its application in nucleic acid detection is still very limited. Herein, an ultrasensitive microRNA (miRNA) biosensor by coupling hybridization-initiated exonuclease I (Exo I) protection and TSA strategy was established. Target miRNA is complementarily hybridized to the biotin-modified DNA probe to form a double strand, which protects the DNA probe from Exo I hydrolysis. Subsequently, horseradish peroxidase (HRP) is attached to the duplex via the biotin-streptavidin reaction and catalyzes the deposition of large amounts of biotin-tyramine in the presence of hydrogen peroxide (H2O2), followed by the conjugation of signal molecule streptavidin-phycoerythrin (SA-PE), which generates an intense fluorescence signal upon laser excitation. This method gave broad linearity in the range of 0.1 fM - 10 pM, yielding a detection limit as low as 74 aM. An increase in sensitivity of 4 orders of magnitude was observed compared to the miRNA detection without TSA amplification. This biosensor was successfully applied to the determination of miR-21 in breast cancer cells and human serum. By further design of specific DNA probes and coupling with the Luminex xMAP technology, it could be easily extended to multiplex miRNA assay, which possesses great application potential in clinical diagnosis.

A chemiluminescent sensor for imaging endogenous hydrogen polysulfides in a living system.

By constructing 2-(benzoylthio)benzoate and a 2-fluoro-4-nitrobenzoate structure in an adamantylidene-dioxetane system, we designed and synthesized two novel chemiluminescent probes for the detection of H2Sn from other RSS. Under the same conditions, the maximum luminescence emission intensity of the probe CL-HP2 could reach 150 times that of the probe CL-HP1, and the chemiluminescence signal still existed at low concentrations. Therefore, CL-HP2 was more suitable for H2Sn detection as a chemiluminescent probe. The probe CL-HP2 exhibited a good linear relationship with Na2S4 in a wide range (0.025-10 mM). Interestingly, a good linear relationship (R2 = 0.997) was also observed at low concentrations (0-100 µM) with a LOD as low as 0.23 µM. CL-HP2 has been effectively employed to visualize endogenous H2Sn within living cells. Moreover, it has been applied for live imaging of bacterially infected murine models and the ferroptosis process in tumor-bearing mouse models.

Structural Characterization, Antioxidant and Antitumor Activities of the Two Novel Exopolysaccharides Produced by Debaryomyces hansenii DH-1.

Exopolysaccharides produced by edible microorganisms exhibit excellent constructive physicochemical and significant biological activity, which provide advantages for the food or pharmaceutical industries. Two novel exopolysaccharides produced by Debaryomyces hansenii DH-1 were characterized, named S1 and S2, respectively. S1, with a molecular weight of 34.594 kDa, primarily consisted of mannose and glucose in a molar ratio of 12.19:1.00, which contained a backbone fragment of α-D-Manp-(1→4)-α-D-Manp-(1→2)-α-D-Glcp-(1→3)-α-D-Manp-(1→3)-ß-D-Glcp-(1→4)-ß-D-Manp-(1→. S2, with a molecular weight of 24.657 kDa, was mainly composed of mannose and galactose in a molar ratio of 4.00:1.00, which had a backbone fragment of α-D-Manp-(1→6)-ß-D-Manp-(1→2)-α-D-Manp-(1→4)-α-D-Galp-(1→3)-ß-D-Manp-(1→6)-α-D-Manp-(1→. Both S1 and S2 exhibited good thermal stability and potent hydroxyl radical scavenging activity, with ~98%. Moreover, S1 possessed an additional strong iron-reducing capacity. In vitro antitumor assays showed that S1 and S2 significantly inhibited the proliferation of Hela, HepG2, and PC-9 cancer cells. Moreover, PC-9 was more sensitive to S1 compared with S2. The above results indicate that S1 and S2 have great potential to be utilized as natural antioxidants and candidates for cancer treatment in the food and pharmaceutical industries.

Insect anal droplets contain diverse proteins related to gut homeostasis.

BACKGROUND: Insects share similar fundamental molecular principles with mammals in innate immunity. For modulating normal gut microbiota, insects produce phenoloxidase (PO), which is absent in all vertebrates, and reactive nitrogen species (ROS) and antimicrobial proteins (AMPs). However, reports on insect gut phagocytosis are very few. Furthermore, most previous studies measure gene expression at the transcription level. In this study, we provided proteomic evidence on gut modulation of normal microorganisms by investigating the anal droplets from a weevil, Cryptorhynchus lapathi. RESULTS: The results showed that the anal droplets contained diverse proteins related to physical barriers, epithelium renewal, pattern recognition, phenoloxidase activation, oxidative defense and phagocytosis, but AMPs were not detected. According to annotations, Scarb1, integrin ßν, Dscam, spondin or Thbs2s might mediate phagocytosis. As a possible integrin ßν pathway, ßν activates Rho by an unknown mechanism, and Rho induces accumulation of mDia, which then promotes actin polymerization. CONCLUSIONS: Our results well demonstrated that insect anal droplets can be used as materials to investigate the defense of a host to gut microorganisms and supported to the hypothesis that gut phagocytosis occurs in insects.