Saccharide Sensor

James, T. D., Sandanayike, K. E A. S., and Shinktl, S., 1994. Novel dwUHnduced electton transfor sensor saccharides based (m the tnteracti(mofbc Dide acid and amine,/. Outn. See, Chem. Ctmunm. 1994 477-478. 

James TD (2007) Saccharide-Selective Boronic Acid Based Photoinduced Electron Transfer (PET) Fluorescent Sensors. 277 107-152... 

Arimori S, Bell ML, Oh CS et al (2001) Molecular fluorescence sensors for saccharides. Chem Commun 18 1836—1837... 

Bosch LI, Mahon MF, James TD (2004) The B-N bond controls the balance between locally excited (LE) and twisted internal charge transfer (TICT) states observed for aniline based fluorescent saccharide sensors. Tetrahedron Lett 45(13) 2859-2862... 

Arimori S, Bosch LI, Ward CJ, James TD (2001) Fluorescent internal charge transfer (ICT) saccharide sensor. Tetrahedron Lett 42(27) 4553-4555... 

It is worth noting that TTF-based sensors for species other than metals, particularly organic species, have been well studied. The principle is, of course, the same a host group capable of recognising a guest molecule is tethered to the signaller TTF, which displays an altered physical response when a guest is bound and when the receptor is free. Systems of this type are of particular interest as biosensors, for example, in the detection of saccharides for disease... 

Shinkai et al. described the synthesis of dendritic saccharide sensors based on a PAMAM dendrimer labeled with eight boronic acid residues [183]. The dendritic compound showed enhanced binding affinity for D-galactose and d-fructose. The fact that the dendritic boronic acid functions as a saccharide sponge is ascribed primarily to the cooperative action of two boronic acids to form an intramolecular 2 1 complex. When one boronic acid binds a saccharide, its counterpart cannot participate in dimer formation and seeks a guest. 

James TD, Sandanayake KRAS, Iguchi R et al (1995) Novel saccharide-photoinduced electron-transfer sensors based on the interaction of boronic acid and amine. J Am Chem... 

Appropriate combinations of boronic acid and fluorophores lead to a remarkable class of fluorescent sensors of saccharides (Shinkai et ah, 1997, 2000, 2001). The concept of PET (photoinduced electron transfer) sensors (see Section 10.2.2.5 and Figure 10.7) has been introduced successfully as follows a boronic acid moiety is combined intramolecularly with an aminomethylfluorophore consequently, PET from the amine to the fluorophore causes fluorescence quenching of the latter. In the presence of a bound saccharide, the interaction between boronic acid and amine is intensified, which inhibits the PET process (Figure 10.42). S-l is an outstanding example of a selective sensor for glucose based on this concept (see Box 10.4). 

Fig. 10.42. Fluorescent sensors of saccharides based on boronic acids (adapted from James T. D. et al. (1996) Chem.

Carbohydrate detection is important for applications such as glucose monitors these are arguably one of the most successful and relevant biosensors. An interesting fluorescence recovery-type saccharide sensor based on the reactivity of carbohydrates with boronic acids was reported in 2002 [36]. Specifically, modification of the cationic viologen-linked boronic acid derivative 40 to a zwitterionic species 41 upon covalent and reversible reaction of boronic acid with monosaccharides (Scheme 1) can cause the dissociation of the ion-pair in-... 

A new PET-based chemosensor for uronic and sialic acids utilizing the cooperative action of boronic acid and metal chelate was reported by Shinkai and co-workers. This group synthesized a novel fluorescent chemosensor molecule bearing both an o-aminomethylphenylboronic acid group for diol binding to a saccharide and a l,10-phenanthroline-Zn(II)chelate moiety for the carboxylate binding, which enables this sensor to discriminate between neutral monosaccharides and acidic compounds [110],... 

Lumophore-spacer-receptor systems are not by any means limited to the ami-noalkyl aromatic family even if we focus on the receptor unit. Still, the latter family is likely to remain a major provider of ionically switchable luminescent devices. Aminoalkyl aromatics also serve as the platform for the development of luminescent PET sensors for a whole class of nonionic saccharides. While aliphatic amines, either singly or in arrays, can serve as receptors for a variety of cationic... 

Fluorescence sensors for saccharides are of particular interest in a practical sense. This is in part due to the inherent sensitivity of the fluorescence technique. Only small amounts of a sensor are required (typically 10-6 M), offsetting the synthetic costs of such sensors. Also, fluorescence spectrometers are widely available and inexpensive. Fluorescence sensors have also found applications in continuous monitoring using an optical fiber and intracellular mapping using confocal microscopy. 

The first fluorescence PET sensors for saccharides were based on fluorophore boronic acids. Czarnik and Yoon showed that 2- and 9-anthryboronic acid [50] 19 and 20 could be used to detect saccharides. However, the fluorescence change was small [/ (in the presence of saccharide)// (in the absence of saccharide) = ca. 0.7], The pA/a of the fluorophore boronic acids are shifted by saccharide present in the medium. The extent of the effect is in line with the inherent selectivity of phenylboronic acid [49], The PET from the boronate anion is believed to be the source of the fluorescence quenching. Although... 

A more recent approach to designing direct fluorescent indicators for glucose involves two-component boronic acid sensors, where the fluorophore—usually anionic in nature—is quenched by a physically separate boronic acid-substituted viologen receptor. As the saccharide binds with the receptor, the quenching efficiency of the viologen is reduced, resulting in an increased emission intensity of the fluorophore (Figure 10.8). 

---