Double hydrophilic polyphosphoester containing copolymers as efficient templating agnets for calcium carbonate microparticles

The design of drug delivery systems (DDS) often requires biodegradable and biocompatible materials that allow safe retention and controlled drug release. In this respect, CaCO3 particles are appropriate drug carriers that have excellent properties such as low density, high specific surface areas and porosity for drugs and proteins encapsulation. Here, degradable synthetic copolymers based on polyphosphoester (PPE) were used to template CaCO3 particles. PPE is a promising candidate due to its biocompatibility, biodegradability and low toxicity of its degradation products such as phosphates. In particular, PPE copolymers with carboxylic acid pendant groups and negatively charged polyphosphodiester-based copolymers were prepared by organocatalyzed ring opening polymerization (ROP) initiated from poly(ethylene oxide). The moieties introduced along the polymer chains enhance the calcium affinity and so the ability of the copolymers to tune the morphology of the CaCO3 particles. The copolymers were tested as templating agents for the preparation of CaCO3 particles by the classical chemical pathway and the supercritical CO2 (Sc-CO2) route. The morphology of the resulting particles was then compared to the one of particles obtained using hyaluronic acid (HA) as a templating agent. The synthesis involving Sc-CO2 and the copolymer with pendant carboxylic groups was particularly interesting and led to smaller (~1.5 µm) and non-aggregated particles. In the future, the impact of the copolymer structure and of the particle size on the encapsulation and release processes will be investigated.