Abstract
Polyelectrolyte-doped microcapsules (PDM) was fabricated by coaxial electrospray of a mixture of glycerol and water containing 10 mg/mL cationic polyelectrolyte poly(allylamine hydrochloride) (PAH) fed as the core phase solution, and a N,N-dimethylacetylamide solution of 10 wt% polyurethane fed as the shell phase solution. Multi-enzyme system involving Candida Antarctica lipase B (CALB), glucose oxidase (GOD), and horseradish peroxidase (HRP) for cascade reaction was assembled in the PDM at three different places, namely, surface, shell, and lumen. Placing of enzyme inside aqueous lumen of the PDM was realized by in situ encapsulation through adding the enzyme in the core-phase solution for coaxial electrospray. By ion-pairing of enzyme with cationic surfactant CTAB, an organic soluble enzyme-CTAB complex was prepared, so that in situ embedding of enzyme in the shell of the PDM was realized by adding it into the shell phase solution. Surface attachment of enzymes was achieved by layer-by-layer (LbL) technology, which is based on the ion-exchange interactions between oppositely charged enzymes and PAH that was doped in PDM. The enzyme-decorated microcapsule was then studied as a micro-bioreactor, in which 1-Oxododecyla-α-glucopyranoside was converted by CALB to glucose, which was oxidised by GOD to gluconolactone in a second step. The hydrogen peroxide produced was then used by HRP to oxidize ABTS to form coloured radical cation ABTS• (+) for activity analysis. The successful fabrication of the PDM and precise localization of enzymes in the PDM by different strategies were fully characterized. By varying the immobilization strategy, totally six PDM bioreactors with three enzymes precisely positional assembled in different strategies were constructed and their activities for the cascade reaction were investigated and compared. The PDM micro-bioreactor prepared by novel electrospray technologies provide a smart platform for positional assembly of multi-enzyme cascade reaction in a precise and well-controlled manner.