Electrogenerated chemiluminescence (ECL) of water-soluble core/shell CdSe/ZnS quantum dots (QDs) coated with carboxylated polyethylene glycol polymers ("Qdot 625") was investigated in aqueous solutions using 2-(dibutylamino)ethanol (DBAE) and tri-n-propylamine (TPrA) as ECL coreactants. In both cases, ECL emissions at glassy carbon (GC) electrode appeared at the same potential of approximately 0.80 V vs. Ag/AgCl (3.0 M KCl), which was approximately 200 and approximately 150 mV more positive compared with the oxidation potentials for DBAE (approximately +0.60 V vs. Ag/AgCl) and TPrA (approximately +0.65 V vs. Ag/AgCl), respectively. The ECL intensity, however, was significantly affected by the type and the concentration of the ECL coreactant used as well as the nature of the working electrode. Under the present experimental conditions, ECL from DBAE was approximately 17 times stronger than that from TPrA. The maximum ECL was obtained at GC electrode when [DBAE] approximately = 53 mM, where a ratio of 11:3:1 in ECL intensity was evaluated for GC, Au, and Pt electrodes, respectively. The ECL emission of the Qdot 625/DBAE system had an apparent peak value of approximately 625 nm that matched well the fluorescence data. The QD as a label for ECL-based immunoassays of C-reactive protein (CRP) was realized by covalent binding of avidin on its surface, which allowed biotinylated anti-CRP to be attached and interacted with solution-phase CRP and the anti-CRP linked to micro-sized magnetic beads. The newly formed sandwich type aggregates were separated magnetically from the solution matrix, followed by the ECL generation at partially transparent Au nanoparticle-coated ITO electrode or Au/CD electrode in the presence of DBAE. Much stronger ECL responses were observed from the Au/CD electrode, at which a dynamic range of 1.0-10.0 microg mL(-1) CRP and a limit of detection of 1.0 microg mL(-1) CRP were obtained, respectively.

Persistent luminescence materials (PLMs) have been capturing more and more attention in biosensing, which is ascribed to the autoluminescence-free background, no requirement of illumination in situ, and high signal-to-noise ratio. PLMs with tunable persistent luminescence and desired decay patterns are still required to meet the demands of multiple bioassays and time-resolved fluoroimmunoassays. Herein, persistent luminescence nanorods with distinct decay patterns are prepared by doping Mn2+, Mo6+, Cr3+, and Sr2+ in the Zn2GeO4 (ZGO) host material, and persistent luminescence nanoparticles are synthesized by doping Cr3+ in the ZnGa2O4 (ZGC) host material. Green-emitted ZGO:Mn NRs and NIR-emitted ZnGa2O4:Cr (ZGC) NPs show slow luminescence decay rates and noninterfered colors and are alternative probes for the dual detection of prostate specific antigens and carcinoembryonic antigens (CEAs). The limits of detection are as low as 8.9 fg mL–1 PSA and 72 fg mL–1 CEA. The nanoprobes are capable of monitoring the CEA level in the human serum matrix. This work provides a new window for the fabrication of multiplex colored PLMs with desired decay patterns, which were used in high throughput cancer early screening, cancer diagnostics, and time-resolved fluoroimmunoassay.

Methylation of flavonoids appears to be a simple and effective way to improve metabolic resistance and transport of flavonoids. Serum albumins are major soluble proteins serving as transport proteins for many exogenous compounds. This work in here mainly concerns about the effect of methylation of flavonoids on the affinity for human serum albumin (HSA) and ovalbumin. One isoflavone (genistein) and one flavonol (kaempferol) and their monomethylated derivatives at position 4' (biochanin A and kaempferide) were studied for their affinities for ovalbumin and HSA. The methylation of flavonoids significantly affects the binding process. In general, the methylation of flavonoids improved the affinities for proteins by 2-16 times. This result supports that the methylation of genistein and kaempferol enhanced the transporting ability, which leads to facilitated absorption and greatly increased bioavailability. The methylation increases the hydrophobicity of genistein and kaempferol, and the hydrophobic interaction plays an important role in binding flavonoids to HSA and ovoalbumin.

Staphylococcus aureus enterotoxins (SEs, involving SEA, SEB, SEC, SED, and SEE) are considered to be the common toxins causing food poisoning and are not allowed to be detected in food. Accurate and anti-interfering SE detection in a complex food matrix is urgently required for food safety. Dual-modal optical sensors are able to avoid mutual interference of optical signals and possess the advantages of high accuracy and sensitivity. Herein, Au nanobipyramids (Au NBPs) and persistent luminescence ZnGeGaO:Cr,Er,Yb nanoparticle (ZGGO NP) nanocomposites are fabricated using the SEC antibody/antigen as templates, which display enhanced persistent luminescence (PL) and surface-enhanced Raman scattering (SERS) strength. The enhanced PL of Au NBP-ZGGO NP nanocomposites is ascribed to plasmon-enhanced radiative transitions. It is first found that ZGGO NPs display unique upconversion fluorescence, which can be absorbed by Au NBPs and that they largely excite the intensive electromagnetic field for SERS enhancement. Dual-model optical immunoassay achieved anti-interfering and specific SEC detection with a limit of detection of 7.5 pg/mL for the PL signal and 8.9 pg/mL for the SERS signal in the range of 10 pg/mL–100 ng/mL. Depending on the plasmon-enhanced PL mechanism and upconversion fluorescence-enhanced SERS principle, plasmonic NP-semiconductor composites show potential prospects in the establishment of multimodal optical biosensors for the quantitative and accurate evaluation of analytes in a complex food matrix.