Adsorption Capacity Of Hydroxyapatite Research Articles

In English

Microspheres of hydroxyapatite (HA) in alginate (Alg) shell can be successfully used for controlled release of drugs, growth factors, and antibacterial compounds. Hydroxyapatite is a perfect material for biomaterials production due to its high sorption capacity to metal ions, low solubility in water, high stability to oxidisers and reducers, low cost and biocompatibility. Sodium alginate used for microspheres formation due to its cross-linking capability with divalent cations (Cu 2+ , Ca 2+ etc.). Microspheres HA/Alg-Cu were obtained by 2 variants of synthesis and showed more rough surface than that of microspheres HA/Alg-Ca what is better for cell proliferation. XRD results show that HA is the main crystalline phase in obtained microspheres. According to the results of adsorption kinetics study, HA has the main contribution in process of Cu 2+ ions adsorption. The temperature, increasing the rate of the adsorption process, has negligible effect on the adsorption capacity of HA due to the saturation of energetically heterogeneous active sites on the microspheres surface with Cu 2+ ions. Adsorption index of HA/Alg microspheres to Cu 2+ ions was calculated to be above 60 mg/g. Adsorption of Cu 2+ ions on HA/Alg microspheres has an ion-exchange character. Due to the Cu 2+ ions release obtained microspheres showed antibacterial effect on S. aureus and E. coli in concentration 6 mg/mL.

Bioinspired Peptide-Decorated Tannic Acid for in Situ Remineralization of Tooth Enamel: In Vitro and in Vivo Evaluation.

Tooth enamel can be eroded by the local cariogenic bacteria in plaque or nonbacterial factors in the oral environment. The damage is irreversible in most situations. For the etched human tooth enamel to be restored in situ, a salivary-acquired pellicle (SAP) bioinspired tannic acid (SAP-TA) is synthesized. Statherin is one of the SAP proteins that can selectively adsorb onto enamel surface. Peptide sequence DDDEEKC is a bioinspired sequence of statherin and has the adsorption capacity of hydroxyapatite (HAP). TA has abundant polyphenol groups that can grasp Ca2+ in saliva to induce the regeneration of HAP crystal. Hence, SAP-TA not only enhances the binding force at the interface of remineralization but also mimics the biomineralization process of tooth enamel. Moreover, ferric ion can coordinate with SAP-TA to form a compact coating that increases the adsorbed amounts of SAP-TA on tooth enamel. Compared with SAP-TA alone, the etched enamels treated with SAP-TA/Fe(III) have a better remineralization effect and mechanical properties (surface microhardness recovery >80% and binding force of 64.85 N) when being incubated in artificial saliva for 2 weeks. In vivo remineralization performance is evaluated in a classical rat caries model. The polarizing microscope and micro-CT results show that SAP-TA/Fe(III) has a good effect on the remineralization process in a real oral environment, indicating that it is a promising repair material for in situ remineralization of enamel.

Cadmium removal from single- and multi-metal ( [formula omitted]) solutions by sorption on hydroxyapatite

Heavy metal contamination of waters and soils is particularly dangerous to the living organisms. Different studies have demonstrated that hydroxyapatite has a high removal capacity for divalent heavy metal ions in contaminated waters and soils. The removal of Cd from aqueous solutions by hydroxyapatite was investigated in batch conditions at 25 ± 2 ° C . Cadmium was applied both as single- or multi-metal ( Cd + Pb + Zn + Cu ) systems with initial concentrations from 0 to 8 mmol L −1. The adsorption capacity of hydroxyapatite in single-metal system ranged from 0.058 to 1.681 mmol of Cd/g of hydroxyapatite. In the multi-metal system competitive metal sorption reduced the removal capacity by 63–83% compared to the single-metal system. The sorption of Cd by hydroxyapatite follows the Langmuir model. Cadmium immobilization occurs through a two-step mechanism: rapid surface complexation followed by partial dissolution of hydroxyapatite and ion exchange with Ca resulting in the formation of a cadmium-containing hydroxyapatite.