Comparative stability of hydroxyapatite nanoparticles: Poly(ethylene glycol) and pectin as stabilizers

Hydroxyapatite nanoparticles (HA NPs) are widely studied for biomedical applications such as drug delivery and bone regeneration owing to their biocompatibility and osteoconductivity. However, their colloidal instability in aqueous media leads to aggregation and sedimentation, limiting practical use. In this work, we systematically compared the stabilization of HA NPs using poly(ethylene glycol) (PEG) and pectin (Pec) under controlled sonication and centrifugation conditions. Key physicochemical parameters—particle size, zeta potential, pH, conductivity, and long-term dispersion stability—were evaluated, alongside structural and thermal characterization (Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, scanning electron microscopy, and thermal stability analysis). Results show that PEG at higher concentration (HG_0.2) reduced the hydrodynamic size from ∼2580 nm to ∼395 nm after sonication, with a low polydispersity index (0.19), indicating excellent steric stabilization. In contrast, Pec at lower concentration (HT_0.1) yielded a more negative zeta potential (−29.3 mV before and −15.4 mV after sonication), reflecting strong electrostatic stabilization, though higher Pec concentration induced aggregation. Stability studies confirmed that PEG maintained uniform dispersions over 14 days, while Pec promoted partial aggregation at higher loading. Structural analyses confirmed that HA crystallinity was preserved after stabilization. Thermal analysis revealed that PEG improved thermal resilience, while Pec enhanced surface interactions. This study provides the first systematic comparison of PEG- and Pec-stabilized HA NPs under identical processing conditions, demonstrating their distinct steric and electrostatic stabilization mechanisms. The findings highlight optimal conditions for tailoring HA NP dispersions for biomedical formulations requiring long-term stability.