Molecular-engineered polymeric microcapsules assembled from Concanavalin A and glycogen with specific responses to carbohydrates

Abstract

Hollow polymeric microcapsules with specific responses to mannose, fructose, glucose and its corresponding polysaccharide, dextran, at the physiological pH range were fabricated from Concanavalin A, a plant lectin, and glycogen, a polysaccharide, based on the lectin–carbohydrate interaction in a layer-by-layer fashion. The growth pattern of the multilayer film was largely influenced by the environmental pH condition. Hollow capsules with variable size and wall thickness were obtained by assembly on CaCO₃ microparticles and subsequent template removal. The as-prepared capsules remained stable in the pH range 6–9 for 1 h and could survive 3 M urea treatment for at least 1 h. They could specifically respond to or even be destroyed by mannose, fructose, glucose and dextran (M_w 20 kDa and 40 kDa) at the physiological pH condition, but not by other types of carbohydrates such as lactose and galactose. The responses were dependent on both the molecular weight and the concentration of the carbohydrates regardless of the environmental pH condition (pH 6–9). Finally, the capsules were employed as delivery vehicles for poly(styrene-b-acrylic acid) (PS-b-PAA) micelles, which could be partly released under the triggering of glucose or dextran (M_w 20 kDa). With the combination of good stability and specific responsiveness to various carbohydrates, as well as the possibility of loading and releasing functional nano-objects, these microcapsules could be promising candidates as advanced drug delivery carriers and micro-reactors.