Release of Insulin from Calcium Carbonate Microspheres with and without Layer-by-Layer Thin Coatings

Katsuhiko Sato,Masaru Seno,Jun-Ichi Anzai

doi:10.3390/polym6082157

Abstract

The release of insulin from insulin-containing CaCO3 microspheres was investigated. The microspheres were prepared by mixing aqueous solutions of CaCl2 and Na2CO3 in the presence of insulin. The surface of the insulin-containing CaCO3 microspheres was coated with a layer-by-layer thin film consisting of poly(allylamine hydrochloride) and poly(styrene sulfonate) to regulate the release kinetics of insulin. The release rate of insulin from the coated CaCO3 microspheres was significantly suppressed compared with that of uncoated CaCO3 microspheres, and depended on the thickness of the films. Rhombohedral calcite crystals of CaCO3 formed from the microspheres during the release of insulin, suggesting that the CaCO3 microspheres dissolved and recrystallized during the release of insulin.

Highlights

Organic and inorganic nano- and micro-particles have been extensively studied for the development of catalysts, biosensors, reagents for imaging, and drug delivery systems [1,2,3,4,5,6,7,8]
The release profile of DOX depended on the temperature and pH of the solution owing to the stimuli-sensitive nature of the polymer coatings, showing that CaCO3 microspheres are useful as vehicles for controlled drug delivery
The release of insulin from the microspheres depended on the pH of the medium and the thickness of the polymer film coating on the surface

Summary

Introduction

Organic and inorganic nano- and micro-particles have been extensively studied for the development of catalysts, biosensors, reagents for imaging, and drug delivery systems [1,2,3,4,5,6,7,8]. The amount of proteins loaded in CaCO3 microspheres depends on the preparation conditions, including the concentration of proteins and salts in the solutions, the relative volume of the solutions, and the reaction time. These parameters must be optimized to obtain CaCO3 microspheres containing the desired amount of proteins. The release of drugs and proteins from CaCO3 microspheres and polymer microcapsules has been studied for developing controlled delivery systems. The release profile of DOX depended on the temperature and pH of the solution owing to the stimuli-sensitive nature of the polymer coatings, showing that CaCO3 microspheres are useful as vehicles for controlled drug delivery. We report the effects of solution pH and LbL film coatings on the release profile of insulin

Materials

Preparation of Uncoated and LbL Film-Coated CaCO3 Microspheres

Release of Insulin from Microspheres

Results and Discussion

Conclusions