Tracking Mineral Growth on Bioorganic Coatings in Real Time at Nanoscale

Researchers compare calcium phosphate mineralization on titanium dioxide nanoparticles coated with two widely used bioorganic coatings

Bioorganic coatings are being increasingly used to promote mineralization on inorganic nanoparticles for bone repair, sensing, and environmental technologies. Researchers at Jeonbuk National University studied how two coating materials, zein and polydopamine, affect calcium phosphate formation on titanium dioxide nanoparticles in real time. They found that the coating's surface chemistry significantly affects initial nucleation and subsequent crystal growth, with polydopamine-coated particles accumulating about 37 percent more mineral mass than zein-coated particles.

Title: Tracking mineral growth on zein- and polydopamine-coated titanium dioxide nanoparticles

Caption: Polydopamine-coated nanoparticles accumulated about 37% more mineral mass than zein-coated ones, indicating faster nucleation and sustained crystal growth. The findings show how the surface chemistry of coatings can influence mineralization rates.

Credit: Professor Chan Hee Park from Jeonbuk National University

License type: Original content

Usage restrictions: Cannot be reused without permission.

Materials that encourage mineralization, mimicking the process in the human body, are becoming increasingly important in medicine and technology. This process, which occurs at the interface between inorganic materials and organic coatings, can facilitate the formation of biological tissue, aid in detecting specific ions, and even assist in removing contaminants from water. The process performance depends largely on the material's ability to trigger nucleation, the initial step where minerals begin to form, and to support continued crystal growth.

Among the various bioorganic coatings (eco-friendly surface coverings made from renewable biological sources) currently being investigated, zein and polydopamine (PDA) are among the more popular options. Zein, a naturally derived protein from maize, forms uniform films and can form bonds with potential mineral ions via its amino acid residues. PDA, a synthetic polymer inspired by adhesive proteins found on mussels, exhibits strong adhesive properties and reactivity, which provides an interactive surface that can promote rapid mineralization. Although both coatings have been individually investigated for their biomineralization potential, a real-time comparison of their mineralization efficiencies on identical nanoparticle systems has not yet been explored. 

In a study made available online on 8 November 2025 and published in Volume 720, Part A of the journal Applied Surface Science on 28 February 2026, a research team led by Professor Chan Hee Park from Jeonbuk National University, Republic of Korea, compared the mineralization of calcium phosphate (CaP) using two widely used bioorganic coatings, zein and PDA, on titanium dioxide (TiO2) nanoparticles in real time.

“By monitoring mineral growth on zein and PDA coated TiO2 nanoparticles in real time at the nanogram scale, we identified kinetic differences that would have likely remained unnoticed with conventional endpoint analysis,” says Prof. Park.

To carry out this comparison, the researchers used a quartz crystal microbalance (QCM). This highly sensitive instrument can detect tiny changes in mass as materials build up on a surface. TiO2 nanoparticles with an average diameter of about 300 nanometers were first coated with either zein or PDA. The coated particles were then immersed in simulated body fluid, a solution that contains mineral components similar to those in human blood plasma and can trigger calcium phosphate formation on the surface.

Mineralization began with calcium ions attaching to surface functional groups, followed by phosphate binding and the formation of CaP crystals. The mineralized PDA-coated TiO2 developed flower-like structures with petal-shaped CaP crystals, indicating efficient nucleation and directed crystal growth. In comparison, the zein-coated particles showed more scattered deposits with less defined crystal structures.

According to Prof. Park, “QCM measurements revealed that PDA-coated samples accumulated about 7,780 nanograms of mineral mass during the measurement period, while zein-coated samples reached about 5,641 nanograms under the same conditions–about 37 percent greater mineral accumulation with PDA.”

Researchers attribute this behavior to the surface chemistry of PDA, which contains polar groups such as catechols and amines that can strongly bind calcium ions and promote nucleation. Zein contains fewer polar functional groups and includes hydrophobic regions, which can make it harder for calcium and phosphate ions to reach the surface and slow the overall mineralization process.

These findings show that differences in surface chemistry influence mineralization and understanding this process could help guide the design of better implants, more effective water purification materials, and improved sensing technologies.

[Reference]

Title of original paper: Nanogram-scale real-time monitoring of bioorganic interfaces as mineralization platforms on titanium dioxide via quartz crystal microbalance

Journal: Applied Surface Science

DOI: 10.1016/j.apsusc.2025.165183 

[About Professor Chan Hee Park] PURE Author Profile

Dr. Chan Hee Park is a Professor at Jeonbuk National University (JBNU) and leads the Biomaterials and Mechanobiology (BMB) Lab. His research focuses on biomaterials, tissue regeneration, mechanobiology, and biosensor platform development. He serves as the Director of the JBNU Non-Clinical Center for Innovative Medical Devices and Vice Director of the Interventional Mechanobio Technology Convergence Research Center.