Colloidal stability under different challenging conditions is essential for many applications of nanoparticles. To achieve this, HLNPs originating from HL60 and HL85 were subjected to hydrothermal curing at 150 °C (Figure ). The resulting particles were colloidally stable at room temperature without any sign of precipitation or aggregation for at least two months (Figure ). The cured HLNPs were dried and studied using FTIR to reveal chemical changes due to the aromatic ring crosslinking reactions via condensation of the hydroxymethyl groups.