A novel soluble aminocellulose derivative type: its transparent film-forming properties and its efficient coupling with enzyme proteins for biosensors

Abstract

By means of the reaction of 6-tosylcellulose derivatives with diamino compounds, it has been possible to provide a new soluble and film-forming aminocellulose-derivative type with a diamine residue at C-6 of the anhydroglucose unit (AGU) and with so-called solubilizing groups, such as acetate, benzoate, carbanilate, methoxy and/or tosylate groups at C-2/C-3. For example, aminocellulose derivatives were synthesized with aliphatic diamine residues of different alkyl chain lengths ((CH2)m with m = 2, 4, 6, 8, 12) at C-6. Other new aminocellulose derivatives were those with an aromatic diamine residue, e.g., 1,4-phenylenediamine or benzidine residue and others, at C-6. Depending on the structure of the diamine residue at C-6 and of the substituents at C-2/C-3, the aminocellulose derivatives were soluble in various solvents, mostly in N,N-dimethylacetamide (DMA) or dimethylsulfoxide (DMSO). Aminocelluloses with a diaminoethane or diaminobutane residue at C-6 and methoxy groups at C-2/C-3 were soluble in water. All the amino celluloses synthesized formed transparent films from their solutions. These aminocelluloses apparently form superstructures or so-called supramolecular architectures according to a structure-inherent organization principle, which became visible, for example, in the case of PDA cellulose tosylates (in DMA) as gel-like aggregates after approx. 1 week of storage at 4°C. The superstructures or aggregates could be imaged on the aminocellulose film surface by atomic force microscopy (AFM) in the form of characteristic topographic structures, e. g. as “hole” structures. In this way, structural and environment-induced factors influencing the aggregate formation were found. The transparent aminocellulose films were excellently suited for covalent coupling with oxidoreductase enzymes such as glucose oxidase (GOD), lactate oxidase (LOD), peroxidase (POD) via bifunctional compounds. A number of new bifunctional enzyme coupling reactions, e. g. via L-ascorbic acid or benzenedisulfonic dichlorides forming amide or sulfonamide coupling structures led to functionally stable nanostructure building blocks with recognition patterns in the case of GOD and POD coupling to PDA cellulose tosylate films. The PDA cellulose derivatives proved to be promising cellulose structural units because the redox-chromogenic PDA residue at C-6 provides the derivatives with a wide range of reaction possibilities, e.g. diazo coupling reactions, NH2-reactive coupling reactions and oxidative coupling reactions to redox dyes.