Isocyanate surface, immobilization

All the specific immobilization methods listed above require a certain functional group to be present in the immobilized compounds. These methods are desirable for combinatorial libraries where the required functionality may be introduced but lend themselves poorly to immobihze natural products or known drugs that do not have a single common functionality that can be targeted. Two methods have been reported to address immobilization of natural products or libraries lacking a common functionality photo crosslinking, and reaction with an isocyanate surface (Fig. 6). 

The functionalization of silica with PPM and the subsequent immobilization of [Rh(COD)2]BF4 has been achieved by Pugin and Blaser [49]. The PPM ligand was immobilized by grafting the linker, 3-trimethoxysilylpropyl isocyanate, to the silica surface (the silicas used include Grace 332, Merck 100, Merck 60, Merck 40). The isocyanate moiety then reacts with the amine functionality of the PPM ligand to afford an amide linkage (35, Figure 5.17). Introduction of a solution of [Rh(COD)2]... 

Since all proteins contain both of these reactive groups, if there were a possibility of producing a polyurethane, and particularly a reticulated polyurethane, with excess isocyanate groups, it would be possible to produce an enzymatically active surface on a high-surface-area, high-void-volume reticulated struemre. This is possible and in fact is easier than the most common methods used currently to immobilize enzymes. 

A different approach to surface functionalization involves direct activation of the silanol groups by reaction with cyanogen bromide. The resulting isocyanate groups can be immediately exploited for covalent immobilization of biomolecules.32... 

Delair et al. [121] immobilized DNA on the surface of PNIPAAm microgels. The amino groups integrated into PNIPAAm microgels were reacted with single-stranded DNA containing a terminal isocyanate groups. 

Schematic illustration of functionalization of a glass substrate by HMDIC followed by immobilization of the 11-HUDA surface-modified CdSe nanoparticles on the isocyanate-bearing substrate through the carbamate-bond forming reaction. Dalton Transactions, 43, 9426 (2009). Reproduced by permission ofThe Royal Society of Chemistry. 

The grafted polymer poly[(ethylene-co-vinyl acetate-co-carbon monoxide)-graft-vinyl chloride] (PVC/EVACO) known in medical applications as plasticized poly(vinyl chloride) was apphed as a carrier polymer for the covalent immobilization of fibronectin. The surface modifications were carried out on foils both with closed surface structure and with microporous surfaces produced by a phase-inversion technique. The vinyl acetate groups of the carrier polymer were saponified and then reacted with hexamethylene diisocyanate (HDI) as a spacer. Fibronectin is immobilized upon reaction of the free isocyanate group with an amino group of the protein (Fig. 33). The saponification of the carrier polymer was verified by IR-ATR and XPS [149]. The presence of hydroxyhc groups after hydrophihzation is demonstrated by a contact angle of 61° while that of the basic polymer is 110°. 

The covalent immobilization of enzymes usuahy begins with a surface modificahon or activation step. The immobilization of enzymes carried out by bifunchonal spedes proceeds by formation of inter- and intramolecular crosslinkages between the enzyme molecules. Isocyanate derivatives and glutaraldehyde (GA) are used as crosslinkers for the immobilization of enzymes in this reaction the amino groups of a protein form Schiff bases with glutaraldehyde [88, 89]. In experiments HMDI and GA served as achvating agents for immobilization of lipase 42. 

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