Studies on the Synthesis and Drug Release Behavior of Cross-Linked Poly(cyclotriphosphazene- co -fluorescein) Microspheres

Cross-linked polyphosphazene-based microspheres have great promise for their specific properties and uniform structures and have attracted much attention due to their potential applications. In this research, cross-linked poly(cyclotriphosphazene- co -fluorescein) (PCTPF) microspheres were synthesized and used as carriers for drug delivery applications. The successful preparation of the PCTPF microspheres was confirmed by Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscope (SEM). The new appeared bands in FT-IR spectra confirmed the successful polymerization between hexachlorocyclotriphosphazene (HCCP) and fluorescein (FLUS). While the SEM results showed that the size of the microspheres was strongly dependent on the mole ratio of HCCP to FLUS. The particle size distribution was determined by dynamic light scattering (DLS) and the results showed that the decreased mole ratio of HCCP to FLUS increases the size of the microspheres. The crystalline nature of PCTPF microspheres was checked by X-ray diffraction and the results showed the amorphous nature of PCTPF microspheres. The thermal properties of the PCTPF microspheres were examined by thermogravimetric analysis and the results exhibited that the increase in thermal properties was ascribed to the cross-linked covalently bonded structure of PCTPF microspheres. The cross-linking density of the prepared PCTPF microspheres was examined via electron paramagnetic resonance (EPR) spectroscopy and the obtained results suggested that the decreased HCCP:FLUS mole ratio could be more capable to cross-link with HCCP in high density. The prepared PCTPF-3 microspheres were used as drug carriers for the anti-cancer drug “Fluorouracil” (5-FU). 5-FU drug was loaded on the prepared microspheres and their in vitro drug release experiment was performed, in which the results showed that the drug released from the PCTPF-3/5-FU microspheres was in a controlled manner up to 336 h. According to the results, the PCTPF microspheres might be used in cancer therapy as drug carriers. Graphical Abstract