Self-assembled hyaluronic acid nanoparticles for controlled release of agrochemicals and diosgenin

Commercial sodium hyaluronate (HA) and synthetic hydrazide-modified HA were functionalized with diosgenin and two agrochemicals (brassinosteroids DI31 and S7) with degree of substitution ranging from 5.6 to 13.1%. The HA-steroid conjugates were studied with FTIR, 1H NMR and differential scanning calorimetry. Dynamic light scattering revealed self-assembly of the HA-steroid conjugates into stable negatively charged nanoparticles of around 159 nm-441 nm in water, which after drying appeared as 140 nm-370 nm spherically shaped nanoparticles according to transmission electron microscopy. These nanoparticles exhibited almost constant release rates of steroids for the first 8 h, demonstrating sustained steroids delivery for 72 h in acidic medium. The nanoparticles formed from HA-steroid conjugates were not cytotoxic to human microvascular endothelial cells (HMVEC), while the HA- brassinosteroid nanoparticles showed in vitro agrochemical activity that was superior to the activity observed for the parent brassinosteroids DI31 and S7 at 10−5 to 10−7 mg mL−1.