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

Abstract 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, 1 H 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 .