Spatial Configuration of Extracellular Organic Substances Responsible for the Biogas Conversion of Sewage Sludge

The influence of the key structural features of sludge that are responsible for the low anaerobic conversion efficiency of sludge is poorly understood. In this study, sludge organic substances are reclassified into extracellular organic substances (EOSs) and cell biomass on the basis of sludge structure. The roles of EOSs in the biogas conversion of both sewage sludge (SS) and model sludge (MS) were investigated. It is observed that with increasing EOS content the net cumulative methane production (NCMP) of the sludge decreased by 36.4%, implying the crucial roles of EOSs in anaerobic sludge digestion. The experimental results showed that with increasing EOS content in sludge, the extracted EOS content decreased, indicating that the structural stability of EOSs in sludge was reinforced. Considering that the biodegradation of EOSs typically depends on structural stability, spatial configuration of EOSs has been hypothesized to account for the low anaerobic digestion efficiency. Further analyses of the spatial configuration of EOSs from the MS and SS revealed that the random-coil shape with extended chains in MS is more readily biodegradable than the dense globule shape with cross-linked chains in SS. These findings shed light on the underlying mechanism responsible for the low biogas conversion of sludge

Resolving Low-Expression Cell Surface Antigens by Time-Gated Orthogonal Scanning Automated Microscopy

We report a highly sensitive method for rapid identification and quantification of rare-event cells carrying low-abundance surface biomarkers. The method applies lanthanide bioprobes and time-gated detection to effectively eliminate both nontarget organisms and background noise and utilizes the europium containing nanoparticles to further amplify the signal strength by a factor of ∼20. Of interest is that these nanoparticles did not correspondingly enhance the intensity of nonspecific binding. Thus, the dramatically improved signal-to-background ratio enables the low-expression surface antigens on single cells to be quantified. Furthermore, we applied an orthogonal scanning automated microscopy (OSAM) technique to rapidly process a large population of target-only cells on microscopy slides, leading to quantitative statistical data with high certainty. Thus, the techniques together resolved nearly all false-negative events from the interfering crowd including many false-positive events

Facile Assembly of Functional Upconversion Nanoparticles for Targeted Cancer Imaging and Photodynamic Therapy

The treatment depth of existing photodynamic therapy (PDT) is limited because of the absorption of visible excitation light in biological tissue. It can be augmented by means of upconversion nanoparticles (UCNPs) transforming deep-penetrating near-infrared (NIR) light to visible light, exciting PDT drugs. We report here a facile strategy to assemble such PDT nanocomposites functionalized for cancer targeting, based on coating of the UCNPs with a silica layer encapsulating the Rose Bengal photosensitizer and bioconjugation to antibodies through a bifunctional fusion protein consisting of a solid-binding peptide linker genetically fused to <i>Streptococcus</i> Protein G′. The fusion protein (Linker-Protein G) mediates the functionalization of silica-coated UCNPs with cancer cell antibodies, allowing for specific target recognition and delivery. The resulting nanocomposites were shown to target cancer cells specifically, generate intracellular reactive oxygen species under 980 nm excitation, and induce NIR-triggered phototoxicity to suppress cancer cell growth in vitro

Facile Peptides Functionalization of Lanthanide-Based Nanocrystals through Phosphorylation Tethering for Efficient <i>in Vivo</i> NIR-to-NIR Bioimaging

Peptide modification of nanoparticles is a challenging task for bioapplications. Here, we show that noncovalent surface engineering based on ligand exchange of peptides for lanthanide based upconversion and downconversion near-infrared (NIR) luminescent nanoparticles can be efficiently realized by modifying the hydroxyl functional group of a side grafted serine of peptides into a phosphate group (phosphorylation). By using the phosphorylated peptide with the arginine-glycine-aspartic acid (RGD) targeting motifs as typical examples, the modification allows improving the selectivity, sensitivity, and signal-to-noise ratio for the cancer targeting and bioimaging and reducing the toxicity derived from nonspecific interactions of nanoparticles with cells. The <i>in vivo</i> NIR bioimaging signal could even be detected at low injection amounts down to 20 μg per animal