ABSTRACT
Phytochemical analysis of the fruits of Cyclocodon lancifolius led to the isolation of two new phenylpropanoid-derived glycosides (1-2), two new geranyl glucosides (3-4), and nine known compounds (5-13). Their chemical structures were elucidated by extensive spectroscopic data. The absolute configuration of the sugar moiety was determined by hydrolysis and derivatization. All compounds were evaluated for their xanthine oxidase (XO) and α-glucosidase inhibitory activities, and four compounds showed weak inhibitory activity towards XO.
ABSTRACT
A novel strategy is developed for the fabrication of graphene-CdS (G-CdS) nanocomposites by in situ growth of CdS nanoparticles onto simultaneously reduced graphite oxide, which is noncovalently functionalized by sodium 1-pyrene sulfonate through strong π-π stacking interactions. Subsequently, cobalt 2,9,16,23-tetraaminophthalocyanine (CoTAPc) is self-assembled on the G-CdS nanocomposites through electrostatic interactions to produce phthalocyanine-sensitized G-CdS nanocomposites. The photoactive superstructure enhances the photocurrent generation capability, and presents an efficient photoelectrochemical immunosensing platform for the ultrasensitive detection of the prostate-specific antigen (PSA). The quantitative measurement of PSA is based on the decrease in the photocurrent intensity of the phthalocyanine-sensitized G-CdS nanocomposites, which results from an increase in the steric hindrance due to the formation of the immunocomplex. A linear relationship between the photocurrent decrease and the PSA concentration is obtained in the wide range from 1 pgmL(-1) to 5 µgmL(-1) with a detection limit of 0.63 pgmL(-1). The proposed sensor shows high sensitivity, stability, reproducibility, and can become a promising platform for other biomolecular detection.
Subject(s)
Graphite/chemistry , Indoles/chemistry , Nanocomposites/chemistry , Biosensing Techniques/methods , Humans , Isoindoles , Limit of Detection , Male , Photochemical Processes , Prostate-Specific Antigen/analysis , Reproducibility of ResultsABSTRACT
An ultrasensitive photoelectrochemical immunoassay of cancer biomarker α-fetoprotein (AFP) is proposed that uses titanium dioxide (TiO(2)) coupled with AFP-CdTe-GOx bioconjugate, which featured AFP antigen and glucose oxidase (GOx) labels linked to CdTe quantum dots (QDs) for signal amplification. The synthesized CdTe QDs yielded a homogeneous and narrow size distribution, which allowed the binding of AFP and GOx on CdTe QDs. Greatly enhanced sensitivity for AFP came from a dual signal amplification strategy. First, an effective matching of energy levels between the conduction bands of CdTe QDs and TiO(2) allowed for fast electron injection from excited CdTe QDs to TiO(2) upon irradiation, which reduced the recombination process of electron-hole pairs and prompted photoelectrochemical performance. Second, GOx enzyme could catalyze glucose to produce H(2)O(2), which acted as a sacrificial electron donor to scavenge the photogenerated holes in the valence band of CdTe QDs, further causing an enhanced photocurrent. Thus, on the basis of the dual signal amplification strategy, the competitive immunosensor based on the specific binding of anti-AFP antibodies to AFP and AFP-CdTe-GOx bioconjugates was achieved. This proposed biosensor for AFP possessed largely increased linear detection range from 0.5 pg/mL to 10 µg/mL with a detection limit of 0.13 pg/mL. The proposed amplification strategy shows high sensitivity, stability, and reproducibility and can become a promising platform for other protein detection.
