Dendrimers, amino-terminated, immobilization

Fig. 13 Schematic of immobilization of amino-terminated PAMAM dendrimers to NHS reactive ester SAMs on gold via covalent bond formation reaction from solution provides homogeneously covered layers that can be labeled in order to determine the number of retained primary amino groups of the dendrimers. Micro and nanometer-scale patterning is possible via xCP and DPN...

In many instances, the enzyme shows reduced activity when in close proximity to the slide surface. To address this problem, a molecule, bearing amino groups, can be used as a spacer. Possible candidates are arginine, polylysine, 1,12-diaminododecane, and similar molecules or amino-terminated dendrimers such as those of the PAMAM family which afford a greater density of amino residues. The protocol presented here is effective for the immobilization of glucose oxidase, organophosphorus hydrolase, acetylcholinesterase, and butyrylcholinesterase. An alternate protocol was developed for the immobilization of carbonic anhydrase. 

Physical or electrochemical adsorption uses non-covalent forces to affix the nucleic acid to the solid support and represents a relatively simple mechanism for attachment that is easy to automate. Adsorption was favoured and described in some chapters as suitable immobilization technique when multisite attachment of DNA is needed to exploit the intrinsic DNA oxidation signal in hybridization reactions. Dendrimers such as polyamidoamine with a high density of terminal amino groups have been reported to increase the surface coverage of physically adsorbed DNA to the surface. Furthermore, electrochemical adsorption is described as a useful immobihzation strategy for electrochemical genosensor fabrication. 

Composite monolayers of PAMAM dendrimers and n-alkanethiols immobilized on a Au surface were used as ion gates for [Ru(NH3)6] + and [Fe(CN)6] based on electrostatic interactions [102, 103]. It should be emphasized that in this case the PAMAM dendrimers were not functionalized with redox-active moieties. In aqueous solution, containing [Ru(NH3)6] and [Fe(CN)6] and at pH 6.3 where the terminal amino groups of the dendrimers are... 

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