Confined space-controlled hydroperoxidation of trisubstituted alkenes adsorbed on pentasil zeolites

Photosensitized oxidation of trialkylalkenes 2-methyl-2-pentene (1), 1-methylcyclohexene (2), trans-3-methyl-2-pentene (3), cis-3-methyl-2-pentene (4), and 2-methyl-2-butene (5) included in the internal framework of Na-ZSM-5 zeolites was investigated. The zeolite samples having adsorbed the alkenes were suspended in isooctane, and the sensitizer, tetraphenylporphyrin (TPP), was dissolved in the solution. Singlet oxygen produced in the solution diffused into the internal framework of the zeolites and reacted with alkenes. For all the substrates studied, the ene-type allylic hydroperoxides were obtained in a highly regioselective manner. The regiochemistry for 1-4 in favor of the allylic hydrogen abstraction from the largest substituents is in contrast to their photooxidation within the dye-supported zeolite Na-Y, where the secondary hydroperoxides are preferentially produced. The tight confinement of the alkenes within the narrow channels of the ZSM-5 zeolites is likely to be responsible for this selectivity.     

Liquid-phase microextraction of protein-bound drugs under non-equilibrium conditions

Recently, we introduced an inexpensive and disposable hollow fiber-based device for liquid-phase microextraction (LPME) where ionic analytes typically were extracted and preconcentrated from 1-4 mL aqueous samples (such as plasma and urine) through an organic solvent immobilized in the pores of a polypropylene hollow fiber and into a 10-25 microL volume of acceptor phase present inside the lumen of the hollow fiber. Subsequently, the acceptor phase was directly subjected to the final analysis by a chromatographic or electrophoretic method. In the present work, attention was focused on LPME of the basic drugs amphetamine, pethidine, promethazine, methadone and haloperidol characterized by substantial differences in the degree of protein binding. Drug-protein interactions in plasma resulted in reduced recoveries and substantially increased extraction times compared with extraction of the drugs from a pure water matrix. However, by addition of 5-50% methanol to the plasma samples, recoveries were comparable with LPME from water samples and ranged between 75 and 100%. The addition of methanol was found not to speed up the LPME process and extractions from plasma were performed in 45 min to reach equilibrium. Because approximately 55-70% of the final analyte concentrations were achieved within the initial 10 min of the LPME process, validation was accomplished after 10 and 45 min of LPME. In general, the results with 10 and 45 min were almost comparable, with precision data in the range 1.2-11.1% (RSD) and with linearity in the concentration range 20-1000 ng mL(-1) (r = 0.999). In conclusion, excellent LPME results may be achieved in a short time under non-equilibrium conditions with a minor loss of sensitivity. In cases of drug-protein interactions, methanol may be added to ensure a high extraction recovery.     

Ligand‐Functionalization of BPEI‐Coated YVO4:Bi3+,Eu3+ Nanophosphors for Tumor‐Cell‐Targeted Imaging Applications

In this study, surface‐functionalized, branched polyethylenimine (BPEI)‐modified YVO₄:Bi³⁺,Eu³⁺ nanocrystals (NCs) were successfully synthesized by a simple, rapid, solvent‐free hydrothermal method. The BPEI‐coated YVO₄:Bi³⁺,Eu³⁺ NCs with high crystallinity show broad‐band excitation in the λ=250 to 400 nm near‐ultraviolet (NUV) region and exhibit a sharp‐line emission band centered at λ=619 nm under excitation at λ=350 nm. The surface amino groups contributed by the capping agent, BPEI, not only improve the dispersibility and water/buffer stability of the BPEI‐coated YVO₄:Bi³⁺,Eu³⁺ NCs, but also provide a capability for specifically targeted biomolecule conjugation. Folic acid (FA) and epidermal growth factor (EGF) were further attached to the BPEI‐coated YVO₄:Bi³⁺,Eu³⁺ NCs and exhibited effective positioning of fluorescent NCs toward the targeted folate receptor overexpressed in HeLa cells or EGFR overexpressed in A431 cells with low cytotoxicity. These results demonstrate that the ligand‐functionalized, BPEI‐coated YVO₄:Bi³⁺, Eu³⁺ NCs show great potential as a new‐generation biological luminescent bioprobe for bioimaging applications. Moreover, the unique luminescence properties of BPEI‐coated YVO₄:Bi³⁺,Eu³⁺ NCs show potential to combine with a UVA photosensitizing drug to produce both detective and therapeutic effects for human skin cancer therapy.     

Monochromophore-Based Phosphorescence and Fluorescence from Pure Organic Assemblies for Ratiometric Hypoxia Detection

Hypoxia is a parameter related to many diseases. Ratiometric hypoxia probes often rely on a combination of an O₂-insensitive fluorophore and an O₂-sensitive phosphor in a polymer matrix, which require high cost and multi-step synthesis of transition metal complexes. The two-chromophore hypoxia probes encounter unfavorable energy transfer processes and different stabilities of the chromophores. Reported herein is a pure organic ratiometric hypoxia nanoprobe, assembled by a monochromophore, naphthalimide ureidopyrimidinone (BrNpA-UPy), bridged by a bis-UPy-functionalized benzyl skeleton. The joint factors of quadruple hydrogen bonding, the rigid backbone of UPy, and bromine substitution of the naphthalimide derivative facilitate bright phosphorescence (Φ_P=7.7 %, τ_P=3.2 ms) and fluorescence of the resultant nanoparticles (SNPs) at room temperature, which enable accurate, ratiometric, sensitive oxygen detection (K_sv=189.6 kPa⁻¹) in aqueous solution as well as in living HeLa cells.