Mercaptoundecanoic acid, self-assembled monolayer

Fig. 14. Hyperbranched polymer grafts prepared on a mercaptoundecanoic acid (MUA) self assembled monolayer confined to a gold substrate. PAAM-c-PAA represents a random copolymer of poly(acrylamide) and poly(acrylic acid) prepared from the poly(acrylic acid) carboxylic acid groups and an amine [129]...

In this part we will describe recent achievements in the development of biosensors based on DNA/RNA aptamers. These biosensors are usually prepared by immobilization of aptamer onto a solid support by various methods using chemisorption (aptamer is modified by thiol group) or by avidin-biotin technology (aptamer is modified by biotin) or by covalent attachment of amino group-labeled aptamer to a surface of self-assembly monolayer of 11-mercaptoundecanoic acid (11-MUA). Apart from the method of aptamer immobilization, the biosensors differ in the signal generation. To date, most extensively studied were the biosensors based on optical methods (fluorescence, SPR) and acoustic sensors based mostly on thickness shear mode (TSM) method. However, recently several investigators reported electrochemical sensors based on enzyme-labeled aptamers, electrochemical indicators and impedance spectroscopy methods of detection. 

Characterization of Self Assembled Monolayer Formation of 11-Mercaptoundecanoic Acid on Gold Surfaces... 

Banno et al. studied the enantioselective crystal growth of leucine on self assembled monolayers with covalently attached D or L-leucine molecules (Banno et at, 2004). The monolayers were formed in the following way gold substrates were prepared by vapour deposition of gold on quartz crystals. The substrates were flame annealed and subsequently immersed in 2 mM ethanolic solutions of 11-mercaptoundecanoic acid (MAU). Leucine was then covalently attached to the MAU monolayer. The crystals on the SAM were grown by immersing the substrates in saturated solutions of D, L or DL-leudne. 

Ahma A, Moore E (2012) Electrochemical immunosensor modified with self-assembled monolayer of 11-mercaptoundecanoic acid on gold electrodes for detection of benzo [a pyrene in water. Analyst 137 5839-5844... 

MIP films, applied to a QCM transducer, have been employed for chiral recognition of the R- and 5-propranolol enantiomers [107]. MIP films were prepared for that purpose by surface grafted photo-radical polymerization. First, a monolayer of 11-mercaptoundecanoic acid was self-assembled on a gold electrode of the quartz resonator. Then, a 2,2 -azobis(2-amidinopropane) hydrochloride initiator (AAPH), was attached to this monolayer. Subsequently, this surface-modified resonator was immersed in an ACN solution containing the MAA functional monomer, enantiomer template and trimethylolpropane trimethacrylate (TRIM) cross-linker. Next, the solution was irradiated with UV light for photopolymerization. The resulting MIP-coated resonator was used for enantioselective determination of the propranolol enantiomers under the batch [107] conditions and the FIA [107] conditions with an aqueous-ACN mixed solvent solution as the carrier. The MIP-QCM chemosensor was enantioselective to 5-propranolol at concentrations exceeding 0.38 mM [107]. 

Chemicals and solvents, reagent grade or better, were used as received (Alfa, Aldrich, or Fisher). Prior to monolayer self assembly, SAW devices were silanized using ClSi(CH3)3 (Petrarch) to prevent interactions between polar compounds (particularly the organophosphonates) and the quartz substrate from complicating interpretation of the response. SAMs of mercaptoundecanoic acid (MUA, HS(CH2)iqCOOH Aldrich) were produced by soaking Au-coated SAW devices in a dilute solution of the thiol in ethanol overnight... 

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