Hongxia Chen

Enhancement of BSA Binding on Au Surfaces by calix(4)bisazacrown Monolayer

Effective investigation of biomolecular structure and function with chip-based modern instruments often requires reliable and steady attachment of designated biomolecules on substrate. Here, we investigated the formation of self-assembled monolayer (SAM) with a new calix[4]arene derivative containing bisazacrown ether at the lower rim (calix[4]bisazacrown) where ammonium moieties of proteins can mainly be interacted with. Immobilization process of protein using bovine serum albumin (BSA) on the Au surface modified with calix[4]bisazacrown monolyer as an artificial linker system was monitored by surface plasmon resonance (SPR) technique. The surface concentration of BSA calculated by the simulation of SPR experimental data was higher than that of a well-known similar commercial protein linker. These results can help in modeling and understanding of protein immobilization on solid surface as well as further development lab-on-a-chip (LOC) devices for biomedical diagnosis kit of certain protein related diseases as biomarkers.

Building a novel vitronectin assay by immobilization of integrin on calixarene monolayer

Membrane proteins possess significant hydrophobic domains and are likely to deplete their native activity immobilized on the solid surface relative to those occurring in a membrane environment. To investigate an efficient immobilization method, calix[4]crown-ether monolayer as an artificial protein linker system was constructed on the gold surface and characterized by Fourier transform infrared reflection absorption spectroscopy (FTIR-RAS), atomic force microscopy (AFM) and cyclic voltammetry (CV). Integrin alpha(v)beta3 was functionally immobilized onto the monolayer and the integrin-vitronectin interaction was investigated by surface plasmon resonance (SPR). It was found that calix[4]crown-ether was assembled as a monolayer on the gold surface. Orientation and accessibility of integrin alpha(v)beta3 was assessed by sensitive binding of its natural ligand, vitronectin at pg mL(-1) level. Moreover, surface coverage of integrin layer and thickness calculated through SPR curve simulation verified that integrin layer was a monolayer in activated form. In combination with the SPR method, this calix[4]crown monolayer provided a reliable and simple experimental platform for the investigation of isolated membrane proteins under experimental conditions resembling those of their native properties.

Polymeric waveguide biosensors with calixarene monolayer for detecting potassium ion concentration

Biophotonic sensors based on a polymer waveguide with Bragg reflection gratings are proposed in this work. For developing low-cost disposable sensors, UV curable polymer materials are utilized to demonstrate the waveguide sensors. The grating pattern is formed on the core layer of a polymer waveguide by exposing a laser interference pattern on a photoresist. To detect a small amount of analyte molecule through a specific binding, a calixarene crown molecule is immobilized on a sensing interface. Bragg reflection peak movement is observed depending on the potassium ion concentration dissolved in phosphate buffered saline solution. It has been confirmed experimentally that the sensor could detect the potassium ion concentration on the order of 1pM.

Surface plasmon resonance spectroscopic chiral discrimination using self-assembled leucine derivative monolayer

Pirkle-type chiral stationary phases (CSPs) showed excellent enantiomeric separation for amino acid derivatives by forming energetically different two transient diastereomeric pi-pi donor-acceptor complexes with two enantiomers. A CSP derived from N-(3,5-dinitrobenzoyl) leucine with a thiol ending group for immobilization on Au was synthesized and self-assembled on Au surface as chiral sensing layer. The monolayer characterized by spectroscopic and microscopic methods such as AFM, FTIR reflection absorption spectroscopy (FTIR-RAS) and cyclic voltammetry (CV). The enantiospecific detection onto CSP of the leucine derivative was studied by surface plasmon resonance (SPR). (S)-CSP SAM showed high chiral differential detection for (S)-analyte in a range of 1.0x10(-9) to 1.0x10(-4) M. In combination with the SPR method, the leucine derivative monolayer provided a reliable and simple experimental platform for enantiospecific detection.

Ammonium Ion Optical Sensor Formation and Characterization of a Self‐Assembled Thiazole Containing Dibenzo‐18‐Crown‐6 Monolayer toward Developing Ammonium Ion‐Sensing Interface

Abstract This letter demonstrates a selective NH4 + detection using a synthesized thiazole benzo crownether ethylamine‐lipoic acid conjugate (1) monolayer. A self‐assembled monolayer (SAM) of 1 was formed on Au surface and well characterized by atomic‐force microscopy, Fourier transform infrared reflection absorption spectroscopy and cyclic voltammetry (CV). A good selectivity for NH4 + sensing was observed in a range of 1.0×10−1 to 1.0×10−6 M by surface plasmon resonance.