Novel polymer–polyphenol beads for encapsulation and microreactor applications

Abstract

Novel structures with controllable morphology made from natural materials hold promise for several applications in pharmaceuticals, foods and biotechnology field. In this paper, we utilized the strong interactions between epigallocatechin gallate (EGCG), a polyphenol obtained from green tea, and water soluble cellulose ethers like methyl cellulose (MCE) and hydroxyl propyl methylcellulose (HPMC) to fabricate novel beads with controllable core–shell morphology. The novel polymer–polyphenol beads were prepared by simply adding polymer solution dropwise into an aqueous solution of polyphenol. Effect of process variables like concentration and viscosity grades of polymer, reaction time and concentration of EGCG on bead formation was evaluated. Spherical milky white beads with average diameters ranging from 600–2500 µm were obtained that retained shape after freeze drying. Internal structure of beads was studied using automated light microscopy and cold stage scanning electron microscopy (Cryo-SEM). Percent loading of EGCG in the beads was above 25% w/w in all the cases. The release study in simulated intestinal fluid revealed burst release of EGCG (20% in first 5 minutes) followed by sustained release with more than 90% release at the end of 300 minutes. The antioxidant power of EGCG in the beads was effectively maintained in the alkaline conditions with 5–6 fold activity as compared to free EGCG. Further, the temperature triggered release characteristic of beads was explored by encapsulating eucalyptus oil and studying the release of oil using hot stage microscopy. Enzyme immobilisation application of beads was demonstrated by immobilising α-amylase onto the beads and studying its enzyme activity after several washings.