Self-Assembled O6-Succinyl Chitosan Nanoparticles for Controlled Release of Diosgenin and Agrochemicals

O6-succinyl chitosan was covalently linked to diosgenin and two synthetic brassinosteroid analogues with agrochemical and potential anticancer activity for their controlled release. FTIR and proton NMR spectroscopy confirmed functionalisation of chitosan matrix with the steroids. The prepared conjugates self-aggregated upon stirring and sonication in aqueous medium, as nanoparticles with 300 to 428 nm mean hydrodynamic diameters and steroid content between 5.8 and 13.4% (w/w). Scanning and transmission electron microscopy showed almost spherical 50-80 nm nanoparticles upon drying. Conjugates were also characterised by differential scanning calorimetry and wide-angle X-ray diffraction. In vitro steroid release studies performed in phosphate buffered saline solution at pH 6.0 indicated a drug release dependence on steroid content and hydrodynamic particles size. Almost constant release rates were observed for the first 8 hours and releases were extended for 96 hours. Brassinosteroid-modified nanoparticles showed better agrochemical activity in radish seeds bioassay than the parent brassinosteroids or O6-succinyl chitosan. The potential of these nanoparticles was also revealed by MMC cell proliferation bioassay and MB-MDA-231 cell cytotoxicity.