A method to attach lectins to the surface of spermine alginate microcapsules based on the avidin biotin interaction

Abstract

To serve as model cell or tissue specific drug delivery systems spermine alginate capsules were surface modified by attachment of proteins with carbohydrate specific binding properties, i.e. lectins. In the first of a two step process avidin was covalently bound to the capsule surfaces using a hydroxy-succinimide catalysed carbodiimide reagent. Surface bound avidin was quantitated by lysing the capsules in hypertonic phosphate buffered saline (PBS) and measuring the change in absorbance at 500 nm in the interaction with 2-(4'hydroxyazobenzene) benzoic acid. A time course study of the avidin-binding reaction showed avidin surface concentrations averaged 5.4 nM/cm2 after 16h. In the second step avidin-coated capsules were incubated in aqueous solutions of biotinylated-lectin derivatives. To quantitate lectin uptake, avidin-coated capsules were lysed in PBS and titrated to the turbidance endpoint with ten different biotinylated lectins. Lectin surface concentrations ranged from 2.0 to 6.8 nm/cm2, well below the theoretical limit of 4 biotinylated ligands per molecule of avidin. Individual lectins bound to capsular surfaces retained their respective ligand specific binding properties as demonstrated by measurement of the selective saturable uptake of radiolabeled ligands when incubated with variously lectin coated capsules. The presence of porcine gastric mucin in concentrations up to 4% w/v did not inhibit binding of 14C-labelled mannose or galactose by concanavalin A-coated capsules.

Alginate in Drug Delivery Systems

“…Attachment of lectins to the surface of spermine-modified alginate beads allows for adhesion to epithel rather than mucosa (82). Adhesion to surfaces is important in the development of nonparenteral vaccines, e.g., oral, intranasal, or vaccines to the upper respiratory tract.…”

Alginate graft copolymers and alginate–co-excipient physical mixture in oral drug delivery

“…It is envisaged to promote drug release. Lectin-alginate conjugate [144,145] Lectin is a protein or glycoprotein of non-immunological origin which specifically recognizes sugar molecules and capable of binding to glycosylated membrane components at mammalian mucosa. Examples of non-toxic lectins of plant origin are tomato lectin and wheat germ agglutinin.…”

“…Hazardous process -methanol, pyridine, acetone, p-toluenesulfonyl chloride, cyanogen bromide, carbodiimide, sodium periodate, chloroform, azobisisobutyronitrile, hexane and sodium cyanoborohydride are some chemicals employed in the graft copolymerization processes as free radical initiator, solvent, linker or washing agent. [9,14,135,136,138,139,142,[145][146][147]149,150] The residual content of these substances poses an additional threat in medication safety. The patient safety issue is aggravated by drugs consumed on a long-term basis.…”

Chemoselective Cross-Linking and Functionalization of Alginate via Staudinger Ligation

“…If the capacity of the alginate to form ionic hydrogels following chemical modification is retained, agents can be subsequently immobilized within the cross-linked matrix. For example, functionalization of alginate with biotin can provide for the affinity entrapment of agents such as enzymes, proteins, and peptides within the resulting hydrogel 10, 11, 28…”