Inspired by the composition of adhesive proteins in mussel, a facile, low-cost, and green approach to construct robust polydopamine (PDA) microcapsules as carriers for insulin delivery is developed. The morphology and shell thickness of the capsules could be tuned by varying the concentration of dopamine or the pH of Tris-HCI buffer. The PDA capsules are stable enough for long-term storage and transportation in practical application. The fluorescent property of PDA capsules labeled with FITC is beneficial in monitoring the safety and efficacy of drug carriers. Furthermore, the PDA shell coated insulin particles exhibit pH-responsive release behavior, making them promising for the oral administration of insulin in diabetic patients. (C) 2016 Elsevier Inc. All rights reserved.