Surface modification of hydroxyapatite nanocrystals by grafting polymers containing phosphonic acid groups

Area of Science:

• Materials Science
• Nanotechnology
• Biomaterials

Background:

• Hydroxyapatite (HAp) nanocrystals are crucial in biomaterials.
• Controlling HAp nanocrystal surface properties is essential for applications.
• Aggregation of HAp nanocrystals limits their utility.

Purpose of the Study:

• To develop a novel surface modification method for hydroxyapatite nanocrystals.
• To graft vinyl phosphonic acid (VPA) onto HAp surfaces.
• To investigate the impact of surface modification on HAp colloidal stability.

Main Methods:

• Grafting polymerization of vinyl phosphonic acid (VPA) onto HAp using a redox initiating system in aqueous media.
• Characterization using Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), and Inductively coupled plasma mass spectroscopy (ICP-MS).
• Evaluation of colloidal stability through zeta potential measurements and Transmission electron microscopy (TEM).

Main Results:

• Successful surface modification of HAp nanocrystals with VPA confirmed by FT-IR and XRD.
• Decreased Ca/P molar ratio (from 1.67 to 1.36) with increasing VPA feed, indicating successful grafting.
• Enhanced colloidal stability of modified HAp in water, with TEM showing reduced aggregation and tendency towards single nanocrystals.

Conclusions:

• Grafting vinyl phosphonic acid onto hydroxyapatite nanocrystals is an effective surface modification strategy.
• The modification significantly improves the colloidal stability of HAp nanocrystals in aqueous environments.
• This approach offers potential for advanced applications of hydroxyapatite in biomaterials and nanotechnology.