The Kinetic of Silver Ions Release from Hydroxyapatite-AgNPs

The difficulties in quantitative analysis of $\mathbf{Ag}^{+}$ ions are caused by their joined presence with AgNPs. In this work silver ions release from AgNPs and HA-AgNPs were investigated. The effect of ultrasound treatment on $\mathbf{Ag}^{+}$ ions release was estimated. The Ag nanoparticles with cubic shape and size from 80 to 800 nm were used for experiments. The incubation of AgNPs demonstrates slow $\mathbf{Ag}^{+}$ release that does not exceed $\mathbf{5} \ \boldsymbol{\mu}\mathbf{g}/\mathbf{mL}$ per 24 hours but ultrasound treatment increased ion release that could be used in the combined treatment of infected wounds. Hydroxyapatite (HA) obtained by three various syntheses was mixed with AgNPs to study $\mathbf{Ag}^{+}$ ions released in the presence of HA after ultrasound treatment. Centrifugation was used for separation of $\mathbf{Ag}^{+}$ containing supernatant solution from AgNPs precipitate. The amount of $\mathbf{Ag}^{+}$ ions was estimated in supernatant solution after centrifugation. The ability of HA to decrease the release of $\mathbf{Ag}^{+}$ ions from AgNPs due to adsorption was investigated at three kinds of hydroxyapatites that differed by the relation of components and types of synthesis. The highest $\mathbf{Ag}^{+}$ ion release ability was observed for calcium-deficient apatite which could be explained due to the vacancies in the Ca-deficient apatite crystal structure. The highest amount of released $\mathbf{Ag}^{+}$ ions was $\mathbf{1}.\mathbf{2}-\mathbf{1}.\mathbf{3}\ \boldsymbol{\mu} \mathbf{g}/\mathbf{mL}$ . Silver ions release from AgNPs into the solution was observed in the first hours as well as after 6 days of preservation. The average release was no more than $\mathbf{4}\ \boldsymbol{\mu} \mathbf{g}/\mathbf{mL}$ per 24 hours. After pretreatment of AgNPs in an ultrasound bath silver ions release is increased. The antibacterial properties of the AgNPs-HA composites were studied for concentrations of AgNPs in calcium deficient HA equal $\mathbf{5},\ \mathbf{10},\ \mathbf{20},\ \mathbf{50},\ \mathbf{100},\ \mathbf{200}\ \boldsymbol{\mu} \mathbf{g}/\mathbf{mL}$ . The result was evaluated by measuring the zone of bacterial growth inhibition. Both supernatant (containing $\mathbf{Ag}^{+}$ ions) and precipitate (AgNPs) have antibacterial properties, but their action is mainly by contact mechanism, so precipitate effectiveness is higher. The ultrasound didn't influence nanoparticles' effectiveness but decreased the amount of, $\mathbf{Ag}^{+}$ ion in the samples.