TY - JOUR
T1 - Surface plasmon resonance instrument as a refractometer for liquids and ultrathin films
AU - Liang, Huamin
AU - Miranto, Heini
AU - Granqvist, Niko
AU - Sadowski, Janusz W.
AU - Viitala, Tapani
AU - Wang, Bochu
AU - Yliperttula, Marjo
N1 - Funding Information:
The authors want to thank China Scholarship Council (CSC) for funding the Huamin Liang's study overseas. We are grateful to Jussi Tuppurainen from BioNavis for his valuable help and comments concerning our work. We also would like to thank Arto Urtti for his valuable opinions concerning our manuscript.
PY - 2010/8/6
Y1 - 2010/8/6
N2 - A surface plasmon resonance (SPR) setup in Kretschmann configuration is being utilized as a refractometer for both liquids as well as ultrathin films. The SPR signal detection technology used is based on a goniometer approach providing a wide angular scan range which facilitates highly accurate liquid and gas phase measurements. Attention was paid to improve sample handling and preparation. In order to avoid cross-contamination between measurements an easily removable and exchangeable molded PDMS flow cell was used during the measurements. By careful choice of components for liquid handling the dead volume of the system could be reduced down to some microliters. The angular change and thus the refractive index for sucrose, ethylene glycol (EG) and ethanol solutions with different concentrations, the thickness and refractive index of deposited Langmuir-Blodgett (LB) films, and the interaction kinetics between a biotin containing self-assembled monolayer (SAM) and streptavidin were determined. The measured refractive indices of sucrose, EG and ethanol solutions corresponded well with literature values. LB films were characterized by measuring the complete SPR curve in an angular scan range from 40 to 78°. A two-color SPR approach combined with two-media measurements was successfully employed for simultaneous and unambiguous determination of both refractive index and thickness of stearic acid monolayers. The thickness obtained for the stearic acid monolayer was 2.66 nm, and the refractive indices at 635 and 670 nm were 1.5800 and 1.4138, respectively. The developed sensor-plate holder enabled functionalization of the SPR gold chip outside the instrument, therefore making the sample handling more flexible. The affinity constant obtained for the streptavidin-biotin interaction was 1.01 × 10-8 M. The total angle SPR method used in this study clearly shows its potential to be used as a refractometer for both liquids and ultrathin films, as well as for traditional liquid phase biomolecular kinetic studies.
AB - A surface plasmon resonance (SPR) setup in Kretschmann configuration is being utilized as a refractometer for both liquids as well as ultrathin films. The SPR signal detection technology used is based on a goniometer approach providing a wide angular scan range which facilitates highly accurate liquid and gas phase measurements. Attention was paid to improve sample handling and preparation. In order to avoid cross-contamination between measurements an easily removable and exchangeable molded PDMS flow cell was used during the measurements. By careful choice of components for liquid handling the dead volume of the system could be reduced down to some microliters. The angular change and thus the refractive index for sucrose, ethylene glycol (EG) and ethanol solutions with different concentrations, the thickness and refractive index of deposited Langmuir-Blodgett (LB) films, and the interaction kinetics between a biotin containing self-assembled monolayer (SAM) and streptavidin were determined. The measured refractive indices of sucrose, EG and ethanol solutions corresponded well with literature values. LB films were characterized by measuring the complete SPR curve in an angular scan range from 40 to 78°. A two-color SPR approach combined with two-media measurements was successfully employed for simultaneous and unambiguous determination of both refractive index and thickness of stearic acid monolayers. The thickness obtained for the stearic acid monolayer was 2.66 nm, and the refractive indices at 635 and 670 nm were 1.5800 and 1.4138, respectively. The developed sensor-plate holder enabled functionalization of the SPR gold chip outside the instrument, therefore making the sample handling more flexible. The affinity constant obtained for the streptavidin-biotin interaction was 1.01 × 10-8 M. The total angle SPR method used in this study clearly shows its potential to be used as a refractometer for both liquids and ultrathin films, as well as for traditional liquid phase biomolecular kinetic studies.
KW - Ethylene glycol
KW - LB film
KW - LB monolayer thickness
KW - Refractive index
KW - Refractometer
KW - Stearic acid
KW - Sucrose
KW - Surface plasmon resonance
UR - http://www.scopus.com/inward/record.url?scp=77955468509&partnerID=8YFLogxK
U2 - 10.1016/j.snb.2010.05.048
DO - 10.1016/j.snb.2010.05.048
M3 - Article
AN - SCOPUS:77955468509
SN - 0925-4005
VL - 149
SP - 212
EP - 220
JO - Sensors and Actuators, B: Chemical
JF - Sensors and Actuators, B: Chemical
IS - 1
ER -