Recent advances in the synthesis and applications of pH-responsive CaCO3

Abstract

The biocompatible calcium carbonate (CaCO3) dissociates at low pH, making it a safe pH-responsive building block. Many synthesis routes have been introduced to build CaCO3 based pH-responsive solutions, but there is a lack of detailed comparison. This review aims to compare synthesis routes and applications of pH-responsive CaCO3 based drug delivery systems, nondrug delivery systems, imaging techniques, sensors, and templates. The novelty and limitations in each synthesis and application were successfully identified. CaCO3 based drug delivery systems were extensively developed through impregnation or encapsulation for cancer treatment. The polymer coatings reduced burst release, while metal doping promoted therapeutic effects. Fe2O3 nanoparticles with magnetic properties could initiate Fenton reactions for destroying mitochondrial. Alginate further controlled drug loading and release, allowing dissociation at the reduced condition in the presence of glutathione. Poly(ethylene glycol) delayed release at low pH, and its copolymer micelles are the effective template to build CaCO3 drug delivery systems. Cholesterol-lowering drugs, insulin, and other biocompounds were also loaded into CaCO3 delivery systems. Due to the generation of carbon dioxide, ultrasound imaging could be enhanced. The release of Ca2+ ions triggered the alginate gelation, which enhances photoluminescent changes or electron transfer in sensors. CaCO3 was also utilized as the scarifying template in the drug delivery systems. Past works inspire more uses of CaCO3 for developing pH-responsive concrete, adsorbents, and membranes.