This paper reports a method that simultaneously detects three food-borne pathogenic bacteria, Salmonella typhimurium, Shigella flexneri, and Escherichia coli O157:H7, via an approach that combines magnetic microparticles for the enrichment and antibody-conjugated semiconductor quantum dots (QDs) as fluorescence markers. Using the water-in-oil reverse microemulsions method, the gamma-Fe(2)O(3) magnetic nanoparticles were coated with silica to empower the particles with high dispersibility and broad compatibility to biomacromolecules. The magnetic beads were then modified with amino silane, which could immobilize antibodies by glutaraldehyde treatment. The immunized magnetic beads and pathogenic bacteria formed "bead-cell" complexes in the enrichment procedure. QDs with different emission wavelengths (620, 560, and 520 nm) were immobilized with anti-S. typhimurium antibody, anti-S. flexneri antibody, and anti-E. coli O157:H7 antibody, respectively. Fluorescence microscope images and the fluorescence intensity of QDs labeled "sandwich" complexes (conjungated with antibodies against S. typhimurium, S. flexneri, and E. coli O157:H7, respectively) demonstrated that antibody-conjugated QDs could attach to the surface of bacterial cells selectively and specifically. In our method, we could detect food-borne pathogen bacteria in a food matrix at 10(-3) cfu/mL. We determined that a high concentration of proteins in food matrix would decrease the sensitivity of this method. This method, of which the detection procedures are completed within 2 h, can be applied to the rapid and cost-effective monitoring of bacterial contamination in food samples.

As a powerful signal amplification tool, the DNA walker has been widely applied to detect rare microRNA (miRNA) in vivo. Despite the significant advances, a nearinfrared (NIR) light controllable DNA walker for signal amplification powered by an endogenous initiator has not been realized, which is crucial for spatiotemporal imaging of miRNA in living cells with high sensitivity. Herein, we constructed a NIR-photoactivatable DNA walker system, which was powered by endogenous adenosine triphosphate (ATP) for in situ miRNA imaging with spatial and temporal resolution. The system was very stable with an extremely low fluorescent background for the bioimaging in living cells. We employed upconversion nanoparticles (UCNPs) as the carriers of the DNA probe and transducers of converting NIR to UV light. Coupled with the DNA walker fueled by intracellular ATP, a smart system based on the NIR light initiated DNA walker was successfully developed for precise spatiotemporal control in living cells. Triggered by NIR light, the DNA walker could autonomously and progressively travel along the track with the assistance of intracellular ATP. The system has been successfully applied for in situ miRNA imaging in different cell lines with highly spatial and temporal resolution. This strategy can expand NIR photocontrol the DNA walker for precise imaging in a biological system.

A luminescence resonance energy transfer (LRET) system was successfully developed using near-infrared (NIR) Ag 2 S nanodots (NDs) as the energy acceptors and upconversion nanoparticles (UCNPs) as the energy donors. The system possessing the properties of NIR excitation (980 nm) and NIR emission (795 nm) was used for the ratiometric detection and bioimaging of pH in tumor cells and zebrafish. Glutathione and mercaptopropionic acid (MPA) co-modified Ag 2 S NDs (GM-Ag 2 S NDs) were prepared by ligand exchange with an excellent pH-responsive property over a pH range of 4.0 to 9.0. The NIR GM-Ag 2 S NDs were covalently grafted with silica coated UCNPs, and an efficient LRET platform was developed via modulation of the thickness of the silica coating. Due to the LRET process between UCNPs and GM-Ag 2 S NDs, a ratiometric luminescence nanoprobe with the properties of NIR excitation−NIR emission was constructed for pH biosensing and bioimaging. On the basis of high contrast bioimaging, the nanoplatform can distinguish between tumor and normal tissue in the zebrafish model.

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Antimicrobial peptides are small-molecule proteins that are usually encoded by multiple-gene families. They play crucial roles in the innate immune response, but reports on the functional divergence of antimicrobial peptide gene families are rare. In this study, 14 paralogs of antimicrobial peptides belonging to cecropin, moricin and gloverin families were recombinantly expressed in pET expression systems. By antimicrobial activity tests, peptides representing paralogs in the same family of cecropin and moricin families, displayed remarkable differences against 10 tested bacteria. The evolutionary rates were relatively fast in the two families, which presented obvious functional divergence among paralogs of each family. Four peptides of gloverin family had similar antimicrobial spectrum and activity against tested bacteria. The gloverin family showed similar antimicrobial function and slow evolutionary rates. By induced transcriptional activity, genes encoding active antimicrobial peptides were upregulated at obviously different levels when silkworm pupae were infected by three types of microbes. Association analysis of antimicrobial activities and induced transcriptional activities indicated that the antimicrobial activities might be positively correlated with induced transcriptional activities in the cecropin and moricin families. These results suggest that representative BmcecB6, BmcecD and Bmmor as the major effector genes have broad antimicrobial spectrum, strong antimicrobial activity and high microbe-induced expression among each family and maybe play crucial roles in eliminating microbial infection.

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The integrative bioplatform for capture, detection and release of circulating tumor cells (CTCs) is of great significance in clinical diagnosis and biomedical research. To fulfill this demand, we introduced a near-infrared (NIR) light-switched bioplatform for efficient isolation and downstream analysis of CTCs. The platform was created by first modifying the PEG-MoS2 nanoflakes (NFs)@gelatin nanocomposite on the ITO surface, and then introducing the MUC1 aptamer as a specific recognition element via coupling reaction between aptamer and gelatin to achieve the specific capture for CTCs. Subsequently, the captured cells are released under a NIR light irradiation (808 nm) by using MoS2 NFs as the NIR-regulated control element. Significantly, this platform could capture and release of CTCs with an excellent capture/release efficiency of 89.5% and 92.5%, respectively. Furthermore, the electrochemical bioplatform exhibited a wide linear range for the detection of CTCs from 50 to 1 × 106 cells mL–1 with a detection limit of 15 cells mL–1. After 5 days of reculture, the released cells still maintain good cell shape and proliferation capacity. Moreover, the bioplatfrom is a simple, versatile, and universal system for the recognition, capture, release, and detection of different types of CTCs. Therefore, this bioplatform shows potential applications on the early diagnosis of cancers.