Analysis of μ-Contact Printed Protein Patterns by SPR Imaging with a LED Light Source

Abstract

We demonstrate the characterization of mu-contact printed protein patterns and analysis of protein-protein interactions by two-dimensional (2-D) surface plasmon resonance imaging (SPRi). Advancements in SPRi image quality from employing a light emitting diode (LED) as the light source are described. We show that a LED offers an ideal point source that can eliminate interference artifacts and speckles found when using a laser source. The attainable thickness resolution in fixed-angle imaging is comparable to that of a monochromatic source, providing a solid foundation for quantitative analysis with the system. The SPR imaging technique reported here affords sub-nanometer thickness sensitivity and micrometer lateral resolution, allowing for convenient studies of biomolecular interactions and surface morphologies of ultrathin films. Spatially well-defined protein patterns of bacterial toxins were obtained by microcontact printing using a polydimethylsiloxane (PDMS) stamp on a functionalized self-assembled monolayer on Au. The influence of protein concentration in the inking solution on transfer efficiency was investigated, and a nonlinear correlation was observed between the solution concentration and the amount of protein immobilized on the surface. Quantitative analysis of protein interaction was performed with toxin-specific antibody, showing a concentration-dependent relationship that verifies the retention of biological activity of the protein after printing. The study demonstrates the feasibility and effectiveness of using LEDs as light sources in SPR imaging, opening doors for developing compact SPR instruments for direct, sensitive, and label-free detection of biohazardous molecules.

Plasmonic Optical Properties and Applications of Metal Nanostructures

“…[183] SPR has been further developed in an imaging technique that is sensitive and label free for visualizing the whole of the biochip via a video charge-coupled device camera. [204][205][206] The biochips can be prepared in an array format with each active site providing SPR information simultaneously. It captures all of the local changes at the surface of the biochip providing detailed information on molecular binding, biomolecular interactions, and kinetic processes.…”

Compact, high performance surface plasmon resonance imaging system

“…SPR imaging applications typically fall into the areas of genomics and proteomics. Some examples of genomics applications include DNA-DNA (Wark et al, 2005;He et al, 2000), DNA-RNA (Nelson et al, 2001), and DNA-drug (Wolf et al, 2005) interactions. For proteomics, the applications include determining protein thickness (Otsuki et al, 2005;Wilkop et al, 2004), conformational changes , and expression profiling (Usui-Aoki et al, 2005).…”

“…Some examples of genomics applications include DNA-DNA (Wark et al, 2005;He et al, 2000), DNA-RNA (Nelson et al, 2001), and DNA-drug (Wolf et al, 2005) interactions. For proteomics, the applications include determining protein thickness (Otsuki et al, 2005;Wilkop et al, 2004), conformational changes , and expression profiling (Usui-Aoki et al, 2005). Other diverse application areas for SPR imaging include toxin-binding inhibition in glycomics (Kanda et al, 2005), self-assembled monolayers (Pyo et al, 2005), detection of human choriogonadotropin (Piliarik et al, 2005), and fabrication of electrochemical switches (Arena et al, 2004).…”

“…Since then, researchers have worked on simplifying and improving various aspects of the technique. Some examples include use of multi-spectral scanning (Otsuki et al, 2005;Yuk et al, 2006), use of an incoherent light source, such as an LED, in place of a laser to eliminate speckle (Wilkop et al, 2004), and use of a liquid crystal variable retarder to reduce spatial and temporal fluctuations from the light source (Wolf et al, 2005). SPR imagers designed for laboratory use are beginning to be commercially available, including the SPRimager II (GWC Technologies, USA) and FlexChip (Biacore, Sweden).…”

Detection of arsenic in groundwater using a surface plasmon resonance sensor

“…SPR-based technology is an accepted and established tool for investigation of biological processes, adsorption phenomena, characterization of binding properties of antibodies and other biological molecules, gene analysis and drug discovery [17][18][19][20][21][22][23][24]. Recently, we have shown that a high resolution SPR can be used to detect and quantify heavy metal ions in drinking water [25].…”