One-pot hydrothermal synthesis of orange fluorescent silver nanoclusters as a general probe for sulfides.

Water-soluble fluorescent silver nanoclusters (AgNCs) with almost seven and nine silver atoms and a quantum yield (QY) of 5.38 ± 0.25% were successfully prepared via one-pot hydrothermal synthesis using polymethacrylic acid sodium salt (PMAA-Na) as a template. The as-prepared PMAA-AgNCs displayed a mono-distribution, they were uniform in size and the color of the fluorescence, emitting at 579 nm, was orange when excited at 502 nm. What is more, we found that the as-prepared PMAA-AgNCs could be quenched by sulfides based on the formation of a metal-ligand bond Ag-S, and thus sulfides could be sensitively detected by spectrofluorometry. As proof of concept, thiourea (TU) and other sulfides including cysteine (Cys), glutathione (GSH) and dl-methionine could be detected. For example, the color of the orange fluorescent AgNCs solutions darkened upon the addition of TU and the fluorescence of PMAA-AgNCs was quenched. The detection limit for TU was 6.10 µM in the linear range from 8.57 µM to 2.29 mM.

Facile one-pot synthesis of folic acid-modified graphene to improve the performance of graphene-based sensing strategy.

A convenient and environment-friendly method is reported to synthesize the reduced graphene oxide (rGO) sheets in aqueous solution using folic acid (FA) as both a reducing and stabilizing agent, to improve the performance of graphene-based sensing strategy. The as-prepared FA-rGO sheets were characterized by transmission electron microscopy (TEM), UV-vis absorption spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy, X-ray diffraction (XRD) and thermogravimetric analysis (TGA), which provided the clear identification of the removal of oxygen-containing functional groups from the graphene oxide (GO) to form FA-rGO sheets. Further, it was found that the obtained FA-rGO sheets exhibited better biocompatibility and could act as the more efficient energy acceptor in long range resonance energy transfer (LrRET) process than that of graphene. Additionally, the FA-rGO can also catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by H2O2, and compared with GO sheets, they exhibited the more prominent intrinsic peroxidase-like activity, thus providing the more sensitive approach for colorimetric detection of H2O2.

Highly selective colorimetric detection of spermine in biosamples on basis of the non-crosslinking aggregation of ssDNA-capped gold nanoparticles.

The selective adsorption of single-stranded oligonucleotides (ssDNA) on gold nanoparticles (AuNPs) is well known for stabilizing the AuNPs against aggregation even at high salt concentrations. Our investigation shows that the non-crosslinking aggregation of arbitrary ssDNA-capped AuNPs occurs due to their interaction with the cationic polyamine, spermine (Spm), even without any addition of NaCl. The non-crosslinking aggregation mechanism is that the Spm, served as multivalent counterions, plays the dual roles of charge shielding and ion bridging among the ssDNA-capped AuNPs, which jointly result in the aggregation of the ssDNA-capped AuNPs. Therefore, a sensitive and highly selective colorimetric method for the detection of Spm was developed. To the best of our knowledge, it is the first successful case as to the efforts towards the development of optical assays for cationic polyamine, showing neither natural UV absorption nor fluorescence. Compared with the traditional methods of chromatography and capillary electrophoresis, the approach described here would provide a convenient alternative and new train of thought for the specific detection of Spm in both biological fluid and fermented products.

Obstruction of photoinduced electron transfer from excited porphyrin to graphene oxide: a fluorescence turn-on sensing platform for iron (III) ions.

A comparative research of the assembly of different porphyrin molecules on graphene oxide (GO) and reduced graphene oxide (RGO) was carried out, respectively. Despite the cationic porphyrin molecules can be assembled onto the surfaces of graphene sheets, including GO and RGO, to form complexes through electrostatic and π-π stacking interactions, the more obvious fluorescence quenching and the larger red-shift of the Soret band of porphyrin molecule in RGO-bound states were observed than those in GO-bound states, due to the difference of molecular flattening in degree. Further, more interesting finding was that the complexes formed between cationic porphyrin and GO, rather than RGO sheets, can facilitate the incorporation of iron (III) ions into the porphyrin moieties, due to the presence of the oxygen-contained groups at the basal plane of GO sheets served as auxiliary coordination units, which can high-efficiently obstruct the electron transfer from excited porphyrin to GO sheets and result in the occurrence of fluorescence restoration. Thus, a fluorescence sensing platform has been developed for iron (III) ions detection in this contribution by using the porphyrin/GO nanohybrids as an optical probe, and our present one exhibited rapid and sensitive responses and high selectivity toward iron (III) ions.

Carbon nanotube-DNA hybrid used for activity monitoring and inhibitor screening of nuclease.

Carbon nanotubes (CNTs) can efficiently quench the fluorescence of the adsorbed fluorophores and nonconvalently interact with soft single-stranded DNA (ssDNA). Upon disruption of CNTs-fluorescent oligonucleotides hybrid by nuclease S1, fluorescence turn-on was observed. Using this strategy, a platform based on fluorescence signal for monitoring the activity of nuclease with advantages of high sensitivity and commonality was established, and a linear relationship between initial cleavage reaction rate and nuclease S1 concentration is found in the range of 0.6-8.0 U mL(-1) with a detection limit of 0.08 U mL(-1). Furthermore, by taking pyrophosphate as an example, we use the assay to evaluate the prohibition effect on nuclease, and the extent of fluorescence recovery decreased linearly with increasing the concentration of pyrophosphate in the range of 0.2-1.4 mM, implying that the cleavage reaction by nuclease S1 was prohibited, and therefore this fluorescence assay can also be conveniently utilized for inhibitor screening of nuclease.

Highly selective detection of phosphate in very complicated matrixes with an off-on fluorescent probe of europium-adjusted carbon dots.

A simple method for phosphate (Pi) detection is established by developing an off-on fluorescence probe of europium-adjusted carbon dots (CDs), which has been successfully applied to the detection of Pi in very complicated matrixes such as artificial wetlands system.

A localized surface plasmon resonance light-scattering assay of mercury (II) on the basis of Hg(2+)-DNA complex induced aggregation of gold nanoparticles.

It is known that localized surface plasmon resonance (LSPR) is responsible for the surface-enhanced spectroscopic processes of metallic nanoparticles and thus LSPR spectroscopy has become a powerful technique for chemical and biological purposes. In this contribution, we present a simple homogeneous Hg2+ assay by measuring enhanced LSPR scattering signals resulted from Hg(2+)-DNA complex induced aggregation of gold nanoparticles (AuNPs). In a medium of pH 7.4 tris-HCl buffer containing 0.05 M NaCl, single-stranded oligonucletides with the sequence of 5'-d(T6)-3' (poly-T6 ssDNA), can be selectively adsorbed onto the surface of gold colloids, stabilizing the AuNPs against aggregation. If Hg(2+)-DNA complex via Hg(2+)-mediated thymine-Hg(2+)-thymine (T-Hg(2+)-T) is formed, however, the adsorption of poly-T6 ssDNA onto the surface of gold colloids gets reduced, and then aggregation of the AuNPs occurs owing to the decrease of the electrostatic repulsion between AuNPs. Consequently, strong LSPR scattering signals resulting from the aggregates of AuNPs could be visually observed under a dark field microscope and easily be measured with a common spectrofluorometer. The LSPR scattering intensities characterized at 556.0 nm were found to be proportional to the concentration of Hg2+ ions in the range of 4.0 x 10(-8) to 6.0 x 10(-7) M with the limit of determination (3sigma) of 1.0 nM. Compared with reported colorimetric methods, our present approaches display the advantages of higher sensitivity.

Light scattering sensing detection of pathogens based on the molecular recognition of immunoglobulin with cell wall-associated protein A.

In this contribution, we report a rapid optical detection method of pathogens using Staphylococcus aureus (S. aureus) as the model analyte based on the molecular recognition of immunoglobulin with cell wall-associated Protein A (SpA). It was found that the molecular recognition of human immunoglobulin (IgG) with protein A on the cell wall of S. aureus on glass slide sensing area could result in strong surface enhanced light scattering (SELS) signals, and the SELS intensity (deltaI) increases proportionally with the concentration of S. aureus over the range of 2.5x10(5)-1.0x10(8) CFU mL(-1) with right angle light scattering (RALS) signals detection mode. In order to identify the solid support based molecular recognition between IgG with SpA, we also employed water-soluble CdS quantum dots (CdS-QDs) as a fluorescent marker for IgG by immobilizing the IgG onto the surfaces of CdS-QDs through covalent binding in order to generate recognition probes for SpA on the cell wall of S. aureus. Consequently, the fluorescent method also showed that the detection for pathogens with solid supports is reliable based on the molecular recognition of IgG with SpA.

Increased inflammatory factors activity in model rats with experimental autoimmune prostatitis.

Male rats were immunized with prostate tissue homogenate supernate (PTHS) of male rats with complete Freund's adjuvant (CFA) intra dermal in the multiple points and simultaneously immunized with 0.5 ml Pertussis-Diphtheria-Tetanus (PDT) vaccine intra peritonea on 0 and 30th day. At the 45th day after first immunization, animals were sacrificed and a series of examinations such as HE stain, assay of TNF-alpha by ELISA and assay of inducible nitric oxide synthase (iNOS) mRNA by in-situ hybridization (ISH) were taken. We observed that there was a remarkable up-regulation of TNF-alpha expression in the high dosage model group. The results of macropathology, histopathology and iNOS ISH also revealed the same tendency. This experimental procedure is effective to induce chronic abacterial prostatitis (CAP).

[Morphological and molecular biological peculiarities of the experimental autoimmune prostatitis rat model].

OBJECTIVE: To observe the morphological and molecular biological peculiarities of the experimental autoimmune prostatitis (EAP) rat model made by SC purified prostate protein twice with immune adjuvant. METHODS: Male rats were intradermally immunized with a saline extract of male rat prostate glands (RPG) in Freund's complete adjuvant (FCA) and Pertussis-Diphtheria-Tetanus vaccine 0.5 ml i.p. at the 0 and 30th day, and the concentrations of the extract were respectively 5 mg/ml, 10 mg/ml and 15 mg/ml. At the 45th day, the rats were sacrificed and the morphological and molecular biological changes of the prostate specimens were observed to determine the effective concentration of RPG for a successful model. RESULTS: The expression of inflammation genes such as TNF-alpha, IL-1beta, IL-2 and iNOS obviously increased in the high-dosage model group; LM, EM and in situ hybridization revealed appearant chronic inflammation response, but this was not the case in the other two dosage groups. CONCLUSION: 15 mg/ml RPG mixed with FCA (1:1) 1.0 ml SC with Pertussis-Diphtheria-Tetanus vaccine 0.5 ml i.p. was an effective dosage for the successful model in our experiment.