Molecular printboard

Fe2(III,III)2+ states. By considering that organometallic dendrimers based on conjugated ferrocene units are of special importance since mixed-valence states have interesting electrical, redox, and magnetic properties, recently three generations of polypropylene amine) dendrimers, decorated at their periphery with 4, 8, and 16 (compound 6, Fig. 6.6a) BFc units, respectively, have been synthesized and the electrochemical behavior of the dendrimers complexed with (3-cyclodextrins ([3-CD) and adsorbed at self-assembled monolayers (SAMs) of heptathioether-functionalized [3-CD on gold (molecular printboard) has been studied.40... 

Different cyclodextrin monolayers have been synthesized and their surface properties have been characterized. Kaifer et al. prepared per-6-thiol-cyclodextrins, and described the interfacial monovalent ferrocene complexation at the monolayer.55 Mittler-Neher et al. studied the kinetics of the adsorption of mono- and multithiolate-functionalized CD SAMs.56,57 Beulen et al.,58 Huskens et al.,59 Auletta et al.,60 and Nijhuis et al.61 reported on the concept of molecular printboards, that is, (3-cyclodextrin ((3-CD) SAMs on gold or silicon oxide substrates, onto which complementary multivalent guest-functionalized dendrimer molecules were adsorbed, resulting in the formation of kinetically stable supramolecular assemblies. With the... 

Reversible attachment of nanostructures at molecular printboards was exemplified by the adsorption and desorption of CD-functionalized nanoparticles onto and from stimuli-responsive pre-adsorbed ferrocenyl-dendrimers at a CD SAM (Fig. 13.7).65 Electrochemical oxidation of the ferrocenyl endgroups was employed to induce desorption of the nanostructure from the CD SAM. An in situ adsorption and desorption of ferrocenyl dendrimers and CD-functionalized Au nanoparticles (d 3 nm) onto and from the molecular printboard was observed by a combination of surface plasmon resonance spectroscopy (SPR) and electrochemistry. Similar behavior was observed when larger CD-functionalized silica nanoparticles (d 60 nm) were desorbed from the surface with the aid of ultrasonication. 

Ludden MJW, Reinhoudt DN, Huskens J (2006) Molecular printboards versatile platforms for the creation and positioning of supramolecular assemblies and materials. Chem Soc Rev 35 1122-1134... 

Onclin, S. Mulder, A. Huskens, J. Ravoo, B. J. Reinhoudt, D. N. Molecular Printboards Monolayers of Beta-Cyclodextrins on Silicon Oxide Surfaces. Langmuir 2004, 20, 5460-5466... 

Fig. 2 Atomic force microscopy (AFM) friction images and schematic illustrations of the patterning processes of a microcontact printed SAMs (mercaptoethanol dots in oc-tadecanethiol matrix, scale bar 10 xm) b patterned molecular printboards fabricated by supramolecular dip-pen nanolithography (DPN) (reprinted with permission from [92] Copyright 2004. WUey VCH) e locally hydrolyzed tert-butyl acrylate-terminated polymer film on oxidized silicon (soft lithography scale bar 3 xm) (Feng CL, Vancso GJ, SchOn-herr H, manuscript submitted to Langmuir) d photopatterned bilayer of diacetylene lipid (scale bar 10 xm). Reprinted in part with permission from [93], copyright (1999), American Chemical Society...

Nijhnis, C. A., Oncel, N., et al. Room-Temperature Single-Electron Tnrmeling in Den-drimer-StabiUzed Gold Nanoparticles Anchored at a Molecular Printboard. SmalL2(12), 1422-1426 (2006). 

Reinhoudt and Huskens further pursued CD-funrtional molecular printboards on gold, demonstrating that a variety of Ad-fimcti onali zed substtates indnding calix[n]arenes and... 

Nijhuis, C.A., Dolatowska, K.A., Ravoo, B.J., Huskens, J., Reinhoudt, D.N. Redox-controlled interaction of biferrocenyl-terminated dendrimers with / -cyclodextrin molecular printboards. Chem. Eur. J. 13, 69-80 (2007). doi 10.1002/chem.200600777... 

Interestingly, tetraguanidinium calix[4]arene was anchored, by Reinhoudt and coworkers, to a /I-cyclodextrin (fi-CU) SAM on An surface (molecular printboard) through hydrophobic interactions of the adamantyl units with the surface-confined fi-CD cavities [48]. The subsequent self-assembly of the molecular capsule with tetrasulfonate calix[4]arene on surface through ionic interactions was monitored by SPR spectroscopy. The tetrasulfonate calix[4]arene could be removed by rinsing of the surface with a high ionic strength aqueous solution, while the complete... 

Onclin S, Mulder A, Huskens J, Ravoo BJ, Reinhoudt DN (2004) Molecular printboards monolayers of beta-cyclodextrins on silicon oxide surfaces. Langmuir 20 5460-5466... 

Nijhuis CA, Huskens J, Reinhoudt DN (2004) Binding control and stoichiometry of ferrocenyl dendrimers at a molecular printboard. J Am Chem Soc 126 12266-12267... 

There are different methods to prevent the nonspecific adsorption of proteins onto surfaces, for example by adding surfactants or bovine serum albumin (BSA) to protein solutions, or by the widely applied method using self-assembled monolayers (SAMs) that are protein-resistant , such as SAMs with oUgo(ethylene glycol), l.e. OEG chains. These SAMs prevent nonspecific interactions due to their loose packing and the weU-hydrated nature. Such molecularly imprinted P-CD polymers, i.e. the P-CD molecular printboards were used as a platform for the immobilization of proteins through small multivalent orthogonal linker molecules. 

The modification of P-CD with seven thioether chains affording 37 was made to obtain ordered and densely packed SAMs on gold. The existence of multivalent host-guest interactions enables the formation of kinetically stable assemblies, and the complex formation by patterning, therefore such surfaces may be considered as molecular printboards . 

The monovalent blocking agent 38 was used to form a dynamic supramolecularly controlled OEG layer on P-CD molecular printboards. This process prevents nonspecific protein adsorption. Moreover it allows replacement by multivalent linker molecules, since multivalent interactions are stronger than monovaient ones. The above method was used for two proteins, namely for the typical test protein streptavidin 39a and for the bioengineered histidine-tagged, maltose binding protein (39b), i.e. HiseMBP [86],... 

Moreover, the possibility to exchange 38 onto proteins was found in this way the proteins can be attached to the surface by specific binding. This was shown for two proteins 39a and 39b, which are bound through differently functionalized linkers to p-CD SAMs in this way the versatility of this method was shown. The above inhibition of nonspecific protein adsorption demonstrates that the use of molecular printboards as a general platform for the immobilization of proteins is very promising. 

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