Calcium level-responsive in-vitro zinc release from zinc containing tricalcium phosphate (ZnTCP)

Area of Science:

• Biomaterials Science
• Materials Chemistry
• Biomineralization

Background:

• Tricalcium phosphate (TCP) is a widely used biomaterial.
• Incorporating zinc (Zn) into TCP can enhance its properties for biomedical applications.
• Understanding Zn release kinetics is crucial for predicting the behavior of Zn-containing biomaterials in physiological environments.

Purpose of the Study:

• To investigate the in vitro zinc (Zn) release from tricalcium phosphate containing varying concentrations of Zn (ZnTCP).
• To determine the effect of calcium (Ca) concentration in simulated body fluid (SBF) on Zn release rates.
• To analyze the dissolution kinetics and identify factors influencing Zn release from ZnTCP.

Main Methods:

• Zn release from ZnTCP powders (0.63, 6.17, and 12.05 Zn w/w%) was measured in SBF with varying Ca concentrations (SBF/H, SBF/L, SBF/-) at pH 7.25 and 37°C.
• Dissolution kinetics were modeled using the Hixon-Crowell equation.
• Initial dissolution rate (IDR) was calculated using the least-squares method.
• X-ray diffraction (XRD) was used to characterize the ZnTCP samples.

Main Results:

• Zn release from 6% and 12% ZnTCP was initially very rapid.
• Increased Ca concentration in SBF decreased Zn release rates, while increased Zn concentration in TCP enhanced release.
• Zn release from 0.6% ZnTCP was significantly higher than from 6% or 12% ZnTCP, correlating with lower Ca precipitation.
• 0.6% ZnTCP contained hydroxyapatite, potentially acting as seed crystals during dissolution.

Conclusions:

• The concentration of Zn in ZnTCP and Ca in the surrounding fluid significantly influence in vitro Zn release.
• The dissolution behavior of ZnTCP is complex and depends on its composition and the ionic environment.
• 0.6% ZnTCP exhibits distinct release characteristics, possibly due to the presence of hydroxyapatite, suggesting potential for tailored applications.