Preliminary study on singlet oxygen production using CeF3:Tb3+@SiO2-PpIX

Luminescent properties and singlet oxygen production using CeF₃:Tb³⁺-based nanoparticles modified with SiO₂ and protoporphyrin IX (PpIX) were studied. CeF₃:Tb³⁺ nanopowder was prepared via sol–gel route, with subsequent surface coating by SiO₂ layer and the conjugation with photosensitive PpIX molecules. Radioluminescence spectra suggest an energy transfer from Ce³⁺ to Tb³⁺ ions and from Tb³⁺ to molecules of PpIX photosensitizer. The energy transfer was confirmed by photoluminescence decay curves. Singlet oxygen production was detected using a reaction of ¹O₂ with 3’-(p-aminophenyl) fluorescein (APF) chemical probe after X-Ray excitation. Qualitative changes in time resolved photoluminescence spectra in the region of 520 nm indicate ¹O₂ generation. Studied nanocomposites may be good candidates for the application in X-ray induced photodynamic therapy.     

Surface plasmon resonance immunosensor for bacteria detection

This work describes an approach for the development of two bacteria biosensors based on surface plasmon resonance (SPR) technique. The first biosensor was based on functionalized gold substrate and the second one on immobilized gold nanoparticles. For the first biosensor, the gold substrate was functionalized with acid-thiol using the self-assembled monolayer technique, while the second one was functionalized with gold nanoparticles immobilized on modified gold substrate. A polyclonal anti-Escherichia coli antibody was immobilized for specific (E. coli) and non-specific (Lactobacillus) bacteria detection. Detection limit with a good reproducibility of 10⁴ and 10³ cfu mL⁻¹ of E. coli bacteria has been obtained for the first biosensor and for the second one respectively. A refractive index variation below 5 × 10⁻³ due to bacteria adsorption is able to be detected. The refractive index of the multilayer structure and of the E. coli bacteria layer was estimated with a modeling software.     

Formation of amine groups on the surface of GaN: A method for direct biofunctionalization

Gallium nitride has attracted significant interest as a material for biosensors; however, techniques for biofunctionalizing GaN surfaces have received limited attention. Here, we present a method for producing amine groups directly on GaN surfaces through exposure to a glow discharge plasma fed with humidified air, thereby eliminating the need for complex organic functionalization chemistry. Amine formation is tracked via X-ray photoelectron spectroscopy (XPS) by labeling the plasma-formed surface groups with a fluorinated probe that binds specifically to primary amines. These amine groups can subsequently couple covalently to a wide range of biomolecules. The covalent immobilization of a NeutrAvidin layer is demonstrated using Fourier transform infrared spectroscopy (FT-IR) and fluorescent biotin-binding assays. Finally, we show that plasma exposure times sufficient for the formation of amine groups do not significantly alter the conductivity of the GaN substrate.     

New syntheses for 11-(mercaptoundecyl)triethylene glycol and mercaptododecyltriethyleneoxy biotin amide

Novel syntheses for mercaptododecyltriethyleneoxy biotin amide and 11-(mercaptoundecyl)triethylene glycol are presented here. Such alkyl thiols are popular components in creating monolayers capable of specifically binding proteins. The development of a variety of functionalized alkyl thiol compounds has a great impact on biosensor substrate design. In our synthesis of mercaptododecyltriethyleneoxy biotin amide, we couple aminotriethyleneoxydodecane disulfide to the NHS-activated biotin; this technique is amenable to attaching a carboxylated molecule of interest in order to create the functionalized alkyl thiol of choice. The 11-(mercaptoundecyl)triethylene glycol synthesis presented here is an alternative method easily completed in three steps.