Adaptation mechanisms of microalgal-bacterial granular sludge to outdoor light-limited conditions.

Microalgal-bacterial granular sludge (MBGS) has attached attention for sustainable wastewater treatment, but it remains elusive whether it can adapt to outdoor light-limited conditions. This paper investigated the biological adaptation mechanisms of MBGS to outdoor light-limited diel conditions using real municipal wastewater. The results indicated that MBGS still had excellent pollutants removal performance, and that both the extracellular polymeric substances and glycogen content of MBGS increased significantly. The main functional microalgae and bacteria were revealed to be Leptolyngbyaceae and Rhodanobacteria, respectively. Further analyses indicated that the abundance of genes encoding PsbA, PsbD, PsbE, PsbJ, PsbP, Psb27, Psb28-2, PsaC, PsaE, PsaL, PsbX, PetB, PetA, and PetE increased in photosystem. Meanwhile, the abundance of gene encoding Rubisco decreased but the gene abundance regarding to crassulacean acid metabolism cycle increased. These suggested that MBGS could adjust the photosynthetic pathway to ensure the completion of photosynthesis. This study is anticipated to add fundamental insights for the MBGS process operated under outdoor light-limited conditions.

Efficient Protein-Protein Couplings Mediated by Small Molecules under Mild Conditions.

Protein-protein coupling reactions under physiological conditions that do not impact the three-dimensional structures of the proteins are in high demand. Owing to the combination of phenylsulfonyl and aldehyde groups in 5-fluoro-4-(phenylsulfonyl)picolinaldehyde (FPPA), the fluorine substituent shows high reactivity toward free thiols. In FPPA, the fluorine is more reactive than phenylsulfonyl for free thiols. Thus the first quantitative nucleophilic substitution can be followed by selective substitution of phenylsulfonyl by an additional thiol or cyclization of aldehyde with a 1,2-aminothiol molecule. The FPPA mediated protein-protein coupling proceeds efficiently under mild conditions, resulting in stable protein conjugates. This coupling method has negligible 3D structural perturbations on the target proteins, and it produces overall intact, nearly traceless, and native structural folds of proteins. It is highly suitable for reconstruction of proteins that are difficult to make and segmental isotopic labeling of multidomain proteins.

Peroxidase-Like Activity of Ethylene Diamine Tetraacetic Acid and Its Application for Ultrasensitive Detection of Tumor Biomarkers and Circular Tumor Cells.

Ethylene diamine tetraacetic acid (EDTA) is such a powerful chelating agent that it may form stable complexes with most metal ions, which has wide applications in industry, agriculture, environment, and pharmaceutical technology. Recently, EDTA was found to enhance the photocatalytic property of some materials. Inspired by this fact of EDTA in the photocatalytic role, we further investigated the photocatalytic property of EDTA and found much the same as that of natural horseradish peroxidase (HRP). This significant discovery of peroxidase-like property may extend the applications of conventional EDTA in life science. A novel and colorimetric sensor based on the peroxidase-like EDTA and unique gold nanorods (GNRs) was designed. Under light irradiation, EDTA may catalyze decomposition of hydrogen peroxide and in situ regulate the longitudinal plasmon wavelength (LPW) of GNRs, displaying various color solution as a read-out means. This colorimetric nanosensor has a great potential to develop into a platform to quantitatively determine analytes as long as the specific antibodies against them were available. Biomarkers of different diseases, such as breast cancer and prostate cancer, were detected with high accuracy. Moreover, combined with immunomagnetic separation of circulating tumor cells (CTCs) from blood, a visual read-out for detection of CTCs was established, which has promising applications in clinical diagnosis, environmental monitoring, and food quality control only using naked eyes.

Strategy To Fabricate Naked-Eye Readout Ultrasensitive Plasmonic Nanosensor Based on Enzyme Mimetic Gold Nanoclusters.

It is broadly interesting but remains a big challenge to explore nanomaterials-based methods to enable naked-eye observation and determination of ultratrace biomarkers and drugs. In this study, we developed a straightforward and extendable plasmonic nanosensor to enable visually quantitative determination of ultratrace target molecules through combining the use of enzyme-mimetic gold nanoclusters (AuNCs). Starting from sandwiched antibody-antigen (i.e., an analyte)-antibody structure, we conjugated AuNCs on the outer layer antibody to catalyze the decomposition of hydrogen peroxide used to reduce HAuCl4 into gold nanopartilces (AuNPs) for naked eye readout. This strategy is in theory applicable to all immunoreactions available and the protocol proposed to attach AuNCs onto an antibody is suitable to all proteins. The applicability of this type of nanosensor was validated by the determination of various ultratrace analytes such as protein avidin, breast cancer antigen, thyroid hormone, and even methamphetamine (MA), giving a naked-eye-readout limit of detection (LOD), down to 1.0 × 10(-20) M protein avidin, 7.52 × 10(-14) U/mL breast cancer antigen 15-3, 2.0 × 10(-15) mg/mL 3,5,3'-L-triiodothyronine and 2.3 × 10(-18) mg/mL MA. This strategy is thus considered an ultrasensitive way to fabricate plasmonic nanosensors, having wide and invaluable application potential in clinical, biological, and environmental studies, and in food quality control.

Colorimetric and ultra-sensitive fluorescence resonance energy transfer determination of H2O2 and glucose by multi-functional Au nanoclusters.

Ultra-sensitive colorimetric determination of H2O2 is accomplished based on the intrinsic peroxidase-like activity of Au nanoclusters (AuNCs) stabilized by glutathione (GSH). The color change of 3,3,5,5-tetramethylbenzidine (TMB) catalyzed by AuNCs offers an indirect method to measure glucose. This sensing platform makes use of a dual optical signal change, including the color change in an aqueous solution under visible light illumination and an ultra-sensitive fluorescent assay arising from efficient fluorescence resonance energy transfer (FRET) between the AuNCs and oxidized TMB. The detection limits of H2O2 and glucose are 4.9 × 10(-13) M and 1.0 × 10(-11) M, respectively. In addition, enhanced fluorescence is observed from the AuNCs due to the use of ethanol which produces clear changes in the quantum yield and lifetime of the AuNCs. The quantum yield of AuNCs is enhanced from ∼12.5% as an isolated fluorophore to 38.9% in an AuNCs-ethanol complex. The enhanced fluorescence lowers the detection limits of H2O2 and glucose by 2 orders of magnitude compared to those attained from the original AuNCs.

Research progress in tumor therapy of carrier-free nanodrug.

Carrier-free nanodrugs are a novel type of drug constructed by the self-assembly of drug molecules without carrier involvement. They have the characteristics of small particle size, easy penetration of various barriers, targeting tumors, and efficient release. In recent years, carrier-free nanodrugs have become a hot topic in tumor therapy as they solve the problems of low drug loading, poor biocompatibility, and low uptake efficiency of carrier nanodrugs. A series of recent studies have shown that carrier-free nanodrugs play a vital role in the treatment of various tumors, with similar or better effects than carrier nanodrugs. Based on the literature published in the past decades, this paper first summarizes the recent progress in the assembly modes of carrier-free nanodrugs, then describes common therapeutic modalities of carrier-free nanodrugs in tumor therapy, and finally depicts the existing challenges along with future trends of carrier-free nanodrugs. We hope that this review can guide the design and application of carrier-free nanodrugs in the future.

Alternate release of different target species based on the same gold nanorods and monitored by cell imaging.

In this study, a strategy for load and release of different kinds of molecules on the same gold nanorods (GNRs) was developed. An anticancer drug, doxorubicin hydrochloride (DOX), was firstly chemically conjugated on the GNRs. To efficiently load another type of target molecules DNA on the same GNRs, a polyelectrolyte Poly (ethylene imine) (PEI) was adsorbed on the GNR@DOX to form GNR@DOX@PEI. Then, the positive charge GNR@DOX@PEI allows the GNR conjugates to interact with negative charged DNA by an electrostatic interaction, enabling their full conjugation. A platform to load two kinds of target molecules conjugated on the same GNRs was fabricated. On the other hand, selective and sequential release of the different target species may be triggered by chemical reaction and near infrared (NIR) laser. The release of DOX was achieved by Na2S2O3 reacting with GNRs and the discharge of DNA conjugated on the GNR@DOX@PEI was accomplished by local-heating using NIR laser triggered release. Furthermore, the selective and alternate release of different target species from the GNRs inside MCF-7 cells was monitored by fluorescent imaging, providing a potential synergistic cancer treatment.

Preparation of Gold-Carbon Dots and Ratiometric Fluorescence Cellular Imaging.

In this study, we synthesized novel gold-carbon dots (GCDs) with unique properties by microwave-assisted method. The characterization of high-resolution transmission electron microscope (HRTEM), XRD, high-angle annular dark field scanning transmission electron microscope (HAADF-STEM), and energy dispersive spectrometer demonstrates that GCDs are composed of carbon and Au. Tiny Au clusters are dispersed in a 2 nm-size carbon skeleton, which integrates the properties of typical CDs and gold nanoclusters (AuNCs), displaying fascinating peroxidase-like activity and single excitation/dual emission. Dual emission of the GCDs exhibits different fluorescent response to the target species and enables the GCDs to be exploited for sensing and bioimaging. The highly photostable and biocompatible GCDs were applied to dual fluorescent imaging for breast cancer cells and normal rat osteoblast cells under a single excitation. Moreover, ratiometric fluorescence imaging was used to monitor Fe(3+) level in normal rat osteoblast cells.

Carbon dots as a fluorescent probe for label-free detection of physiological potassium level in human serum and red blood cells.

A unique photoluminescence carbon dots (CDs) with larger size were prepared by microwave-assisted method. Complex functional groups on the surface of the CDs facilitate the nanoparticles to form affinity with some metal ions. Taking advantage of the effective fluorescence quenching effect of K(+), a highly sensitive CD-based fluorescence analytical system for label-free detection of K(+) with limit of detection (LOD) 1.0×10(-12) M was established. The concentrations of potassium ion in biological samples such as human serum are usually found at millimolar levels or even higher. The proposed method begins with a substantial dilution of the sample to place the K(+) concentration in the dynamic range for quantification, which covers 3 orders of magnitude. This offers some advantages: the detection of K(+) only needs very small quantities of biological samples, and the dilution of samples such as serum may effectively eliminate the potential interferences that often originate from the background matrix. The determined potassium levels were satisfactory and closely comparable with the results given by the hospital, indicating that this fluorescent probe is applicable to detection of physiological potassium level with high accuracy. Compared with other relative biosensors requiring modified design, bio-molecular modification or/and sophisticated instruments, this CD-based sensor is very simple, cost-effective and easy detection, suggesting great potential applications for successively monitoring physiological potassium level and the change in biological system.

Multiplex sensor for detection of different metal ions based on on-off of fluorescent gold nanoclusters.

In this study, a multiplex fluorescence sensor for successive detection of Fe(3+), Cu(2+) and Hg(2+) ions based on "on-off" of fluorescence of a single type of gold nanoclusters (Au NCs) is described. Any of the Fe(3+), Cu(2+) and Hg(2+) ions can cause quenching fluorescence of Au NCs, which established a sensitive sensor for detection of these ions respectively. With the introduction of ethylene diamine tetraacetic acid (EDTA) to the system of Au NCs and metal ions, a restoration of fluorescence may be found with the exception of Hg(2+). A highly selective detection of Hg(2+) ion is, thus, achieved by masking Fe(3+) and Cu(2+). On the other hand, the masking of Fe(3+) and Cu(2+) leads to the enhancement of fluorescence of Au NCs, which in turn provides an approach for successive determination of Fe(3+) and Cu(2+) based on "on-off" of fluorescence of Au NCs. Moreover, this assay was applied to the successful detection of Fe(3+), Cu(2+) and Hg(2+) in fish, a good linear relationship was found between these metal ions and the degree of quenched fluorescent intensity. The dynamic ranges of Hg(2+), Fe(3+) and Cu(2+) were 1.96×10(-10)-1.01×10(-9), 1.28×10(-7)-1.27×10(-6) and 1.2×10(-7)-1.2×10(-6) M with high sensitivity (the limit of detection of Fe(3+) 2.0×10(-8) M, Cu(2+) 1.9×10(-8) M and Hg(2+) 2×10(-10) M). These results indicate that the assay is suitable for sensitive detection of these metal ions even under the coexistence, which can not only determine all three kinds of metal ions successively but also of detecting any or several kinds of metal ions.