Phosphazene immobilized

The next two examples illustrate more complex surface reaction chemistry that brings about the covalent immobilization of bioactive species such as enzymes and catecholamines. Poly [bis (phenoxy)-phosphazene] (compound 1 ) can be used to coat particles of porous alumina with a high-surface-area film of the polymer (23). A scanning electron micrograph of the surface of a coated particle is shown in Fig. 3. The polymer surface is then nitrated and the arylnitro groups reduced to arylamino units. These then provided reactive sites for the immobilization of enzymes, as shown in Scheme III. 

FIGURE 3 Scanning electron micrograph (1200x magnification) of the surface of a porous alumina particle coated with poly(diphenoxy-phosphazene). Surface nitration, reduction, and glutaric dialdehyde coupling immobilized enzyme molecules to the surface. (From Ref. 23.)... 

Third, a poly[bis(phenoxy)phosphazene] has been coated on porous alumina particles, surface nitrated, reduced to the amino-derivative, and then coupled to the enzyme glucose-6-phosphate dehydrogenase or trypsin by means of glutaric dialdehyde. The immobilized enzymes were more stable than their counterparts in solution, and they could be used in continuous flow enzyme reactor equipment (25). 

Schwesingefs phosphazene base 2-tert-butylamino-2-diethylamino-l,3-dimethyl-perhydro-l,3,2-diazaphosphorine (PS-BEMP has a pKb = 27.5 in MeCN) has been immobilized and shown to have immense utility in the N- and O-alkylation of many weakly acidic heterocycles. Kim et al. has made extensive use of this reagent in the multi-step synthesis of a small collection of guanines possessing potential antiviral activity [90]. The generic procedure involved the direct alkylation of the purine moiety (20) (Scheme 2.64), promoted by PS-BEMP, resulting in a mixture... 

In this paper we consider two specific challenges. First, how might transition metals be linked to phosphazene high polymers Such systems are of interest as immobilized catalysts or materials with unusual electrical properties. Second, how can bioactive agents be attached to polyphosphazenes to prepare, for example, targeted, slow release chemotherapeutic agents ... 

Figure 25 Immobilization of enzymes by covalent linkage with poly [ (organo)phosphazenes].

Phosphazene coordination complexes ean aet as faeilitators for probes of the eleetronie structure of metal centers. Gadolinium (III) eomplexes with hexa(diphenylphosphine oxide)cyclotriphosphazene, (41), ean be stabilized and immobilized into a silieate xerogel matrix and studied using Eleetron Paramagnetie Resonanee (EPR) at X (9.4 GHz) and W (94 GHz) band frequeneies, which revealed the first reported information eoneerning the phase ehange that oeeurs at approximately 5.4... 

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