Mixed self-assembled monlayers (SAMs) for immunosensor construction

Morsaline Billah 1Henry Hays 1Sophie Weiss 1Tim Gibson 2Paul A. Millner 1

1. University of Leeds (UOL), Woodhouse Lane, Leeds ls2-9jt, United Kingdom
2. Scensive Technologies Ltd, Ripley Drive, Normanton WF61QT, United Kingdom

Abstract

Immunosensors detect and quantify analytes based on binding related to changes in mass, resistance or capacitance at sensor surfaces. Key to sensor development is the ability to immobilise antibodies and biological recognition elements, via procedures that allow binding affinity to be retained. Mixed self-assembled monolayers (SAMs) comprising long chain alkanethiols i.e. 16-mercaptohexadecanoic acid (MHDA) on gold with incorporated affinity lipids, i.e. 1,2-Dipalmitoyl-sn-Glycero-3-Phosphoethanolamine-N-Cap Biotinyl (Biotinyl cap PE) have been developed to allow antibody tethering via the biotin/Neutravidin interaction. Alternatively, mixed SAMs of 16-mercaptohexadecanoic acid (MHDA) and intercalated 1,2-Dioleoyl-sn-Glycero-3-[(N-(5-amino-1-carboxy- pentyl) iminodiacetic acid) succinyl] (Nickel salt) (DOGS-NTA) were used to immobilise His6-tagged recombinant proteins. Large analytes i.e. haemoglobin (Hb), myoglobin (Mb), prostate specific antigen (PSA) and small analytes, i.e. atrazine and digoxin were studied.

Partially constructed and fully functional immunosensors were characterized via physical techniques including quartz crystal microbalance (QCM) and atomic force microscopy (AFM). Sensor assembly and binding affinity of immobilised antibodies have been independently determined using [125I]-tagged components. Finally, the electrochemical properties of semi-constructed and functional electrodes have been analysed by impedance based measurements at 300 mV (10mV amplitude) at a frequency range between 100kKHz - 0.1 Hz and using a potassium hexacyanoferrate trihydrate mediator.

Furthermore, phospholipids on mercury (Hg) passivation using polyethylene glycol (PEG) incorporation in mixed SAM system was studied to suppress the non-specific binding of protein to the surface.

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Presentation: Poster at SMCBS'2005 Workshop, by Morsaline Billah
See On-line Journal of SMCBS'2005 Workshop

Submitted: 2005-07-29 13:53
Revised:   2009-06-07 00:44
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