Synthesis of biopolymeric particles loaded with phosphorus and potassium: Characterisation and release tests

The authors synthesised nanoparticles (NPs) loaded with P and K from KH₂PO₄ using gelatin type-A and type-B, and sodium alginate as carriers. Using type-A and type-B gelatin, quasi-spherical particles were obtained, with average sizes of 682 and 856 nm, respectively; with sodium alginate, the resulting NPs exhibited spherical shapes and 600 nm particle average size. The authors found an interaction between KH₂PO₄ and alginate via the hydrogen bonds existent among the carboxylic groups of the carbohydrate and the OH-groups of the H₂PO₄-; interactions among gelatin types with the OH-groups and the H₂PO₄-ion were also observed. Adding trypsin to the distilled water solutions of the NPs coated with type-A gelatin increased the concentration of P in the solution by threefold, while increasing that of K increased by 2.6-fold. Conversely, adding α-amylase to the water solutions with sodium alginate increased the P and K concentrations in the solution by nearly 1.3- and 1.1-fold, respectively. Thus, sodium alginate resulted in NPs with smaller sizes and better spherical formations, though with a high polydispersity index and lower release rate of P and K. This low release rate represents an advantage since plants demand nutrients for long periods, and conventional fertilisers display low use efficiency.