Photoinduced electron transfer from polymer-templated Ag nanoclusters to G-quadruplex-hemin complexes for the construction of versatile biosensors and logic gate applications.

In this paper, fluorescent Ag nanoclusters (Ag NCs) templated by hyperbranched polyethyleneimine (PEI) are utilized as a versatile probe through the photoinduced electron transfer (PET) between PEI-Ag NCs and G-quadruplex-hemin complexes. In the presence of hemin and target molecule, the specific conjugation with its aptamer induces the conformational change of the DNA sequence, releasing the G-quadruplex sequence part. Once the G-quadruplex-hemin complexes are introduced, electron transfer from the PEI-Ag NCs to G-quadruplex-hemin complexes occurs, resulting in fluorescence quenching. Through changing the sensing DNA sequence, this novel PET system enables the specific detection of target DNA and adenosine triphosphate (ATP) with the wide linear range of 1-200 nM and 5-500 nM, respectively, and the corresponding limit of detection as low as 0.3 nM for target DNA and 1.5 nM for ATP. In addition, the proposed method is successfully applied to the determination of ATP in human serum samples with satisfactory recoveries, and a logic gate is fabricated using target molecules and hemin as inputs and the fluorescence signal of PEI-Ag NCs as an output.

Combination of pipette tip solid phase extraction and high performance liquid chromatography for determination of plant growth regulators in food samples based on the electrospun covalent organic framework/polyacrylonitrile nanofiber as highly efficient sorbent.

Facile and sensitive determination of plant growth regulators (PGRs) in food samples is important but still remains great challenge. Herein, a pipette tip solid phase extraction (PT-SPE) method was developed for fast and sensitively detecting PGRs. The PT-SPE adsorbent was prepared by integrating a novel covalent organic framework (COF) of schiff base network 3 (SNW-3) and polyacrylonitrile (PAN) through electrospinning. The SNW-3 can easily adsorb PGRs with high special affinity through electrovalent bands between the ammonium ions of SNW-3 and the carboxy groups of PGRs. The polymer of PAN acts as scaffold material for SNW-3, which can lower seepage pressure hence accelerates adsorption/desorption kinetics. By combination with HPLC-DAD, a satisfactory method was successfully developed for simultaneous determination of ten PGRs in watermelon. Good analytical performances were achieved with this proposed method, including good linearity (5-500 ng/mL) with high correlation coefficients (R ≥ 0.9981), low limits of detection (S/N = 3, 0.24-3.19 ng/mL) and limits of quantification (S/N = 10, 1.65-5.72 ng/mL), satisfactory precision (intra-day RSDs ≤ 2.7%, inter-day RSDs ≤ 3.7%), and high accuracy (recovery: 82.8-113.0%). The method developed in this study shows high potential for design of high target-affinity adsorbents for food sample preparing.

[Separation and purification of flavonoids from Smilax glabra by macroporous adsorption resin].

OBJECTIVE: To investigate the process of separating and purifying flavonoids from Smilax glabra. METHOD: With the yield of flavonoids as index, the optimum process of separating and purifying flavonoids from S. glabra Roxb was screened by static and dynamic adsorption tests. RESULT: The static saturated adsorption capacity of D101 macroporous resin to flavonoids of S. glabra was 45.6 mg x g(-1) (dry resin). The optimum conditions of dynamic adsorption and elution were as that the pH, the concentration, the adsorption velocity of the extracting solution, and the adsorption capacity were 6.00 +/- 0.20, 4.2 mg x mL(-1), 2 mL x min(-1) and 15 mL, respectively. The adsorbed resin column was washed by 100 mL 60% ethanol with pH value of 8.00 +/- 0.20 at the eluting velocity of 3 mL x min(-1) after washed by 100 mL distilled water. CONCLUSION: The flavonoids of S. glabra was able to be easily separated and purified by D101 macroporous resin under the optimum conditions above, and the recovery rate was higher than 90%. The content of obtained flavonoids reached 62.6%, which was 2 times of the content before purification.

Analysis of 2 novel mutations of PHEX gene inducing X-linked dominant hypophosphatemia rickets in 2 families: Two case reports.

RATIONALE: X-linked dominant hypophosphatemia rickets (XLH, OMIM 307800) is the most common hereditary hypophosphatemic rickets and characterized by growth retardation, skeletal malformations, dental dysplasia, spontaneous fractures and osteomalacia. PHEX gene was identified for XLH and novel mutations were consistent with loss of function. PATIENT CONCERNS: Case1: the proband 1 III3 in family 1 was a fourteen-year-old boy with bowing of bilateral legs, obviously enlarged joints, tooth absence and difficulty in walking; X-rays showed bilateral femoral multiple fractures with sclerosis at the fracture edge. Case 2: the proband 2 III2, a five-year-old boy in family 2, showed growth retardation, dental dysplasia, gingiva abscess and bilateral legs malformations; X-rays showed low bone density, delayed bone age, bowing of legs, frayed and widened metaphyses of the distal femurs and proximal tibias. Both of their mothers suffered from skeletal malformations, tooth absence and were performed with osteotomy due to fractures of lower limb. Their biochemical parameters showed hypophosphatemia, elevated alkaline phosphatase. DIAGNOSES: X-linked dominant hypophosphatemia rickets (XLH). INTERVENTIONS AND OUTCOMES: Treatment with high doses of phosphate and 1,25-dihydroxyvitamin D3, the height of proband 2 increased 10 cm and femoral Multiple fracture of proband1 almost healed after treatment for 6 months and the patients's PHEX gene was investigated. LESSONS: Two novel pathogenic PHEX mutations were found: c.497delG in family 1 and c.388G> T in family 2, both of which caused early termination of translation and produced truncated protein. Serum FGF23 concentration in our XLH patients were obviously higher than the normal and may be related to age to some extent. Early initiation of treatment produces better effect.

Cascade enzymatic catalysis in poly(acrylic acid) brushes-nanospherical silica for glucose detection.

The ultrasensitive monitoring of glucose with a fast and accurate method is significant in potential therapeutics and optimizes protein biosynthesis. Incorporation of enzyme into matrix is considered as promising candidates for constructing highly sensitive glucose-responsive systems. In this study, three-dimensional poly(acrylic acid) brushes-nanospherical silica (PAA-nano silica) with high amplification capability and stability were used to covalently immobilize bienzymes for cascade enzymatic catalysis. The major advantages of PAA-nano silica-bienzyme co-incorporation is that the enzymes are proximity distribution, and such close confinement both minimized the diffusion of intermediates among the enzymes in the consecutive reaction and improve the utilization efficiency of enzymes, thereby enhancing the overall reaction efficiency and specificity. Thus, this present bienzymatic biosensor shows robust signal amplification and ultrasensitivity of glucose-responsive properties with a detection limit of 0.04µM.

Ultrasensitive electrochemical immunosensor based on horseradish peroxidase (HRP)-loaded silica-poly(acrylic acid) brushes for protein biomarker detection.

We report an ultrasensitive electrochemical immunosensor designed for the detection of protein biomarkers using horseradish peroxidase (HRP)-loaded silica-poly(acrylic acid) brushes (SiO2-SPAABs) as labels. HRP could be efficiently and stably accommodated in the three-dimensional architecture of the SiO2-SPAABs and the SiO2-SPAABs-HRP exhibited high catalytic performance towards o-phenylenediamine (OPD) oxidation in the presence of H2O2, which resulted in significant differential pulse voltammetric (DPV) response change and color change. Using human IgG (HIgG) as a model analyte, a sandwich-type immunosensor was constructed. In particular, graphene oxide (GO) and SiO2-SPAABs-HRP were used to immobilize capture antibody (Ab1) and bind a layer of detection antibody (Ab2), respectively. The current biosensor exhibited a good linear response of HIgG from 100pg/mL to 100µg/mL with a detection limit of 50pg/mL (S/N=5). The sensitivity was 6.70-fold higher than the conventional enzyme-linked immunosorbent assays. The immunosensor results were validated through the detection of HIgG in serum samples.