The Kinetic of Silver Ions Release from Hydroxyapatite-AgNPs

Abstract

The difficulties in quantitative analysis of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{Ag}^{+}$</tex> 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 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{Ag}^{+}$</tex> 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 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{Ag}^{+}$</tex> release that does not exceed <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{5} \ \boldsymbol{\mu}\mathbf{g}/\mathbf{mL}$</tex> 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 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{Ag}^{+}$</tex> ions released in the presence of HA after ultrasound treatment. Centrifugation was used for separation of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{Ag}^{+}$</tex> containing supernatant solution from AgNPs precipitate. The amount of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{Ag}^{+}$</tex> ions was estimated in supernatant solution after centrifugation. The ability of HA to decrease the release of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{Ag}^{+}$</tex> 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 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{Ag}^{+}$</tex> 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 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{Ag}^{+}$</tex> ions was <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{1}.\mathbf{2}-\mathbf{1}.\mathbf{3}\ \boldsymbol{\mu} \mathbf{g}/\mathbf{mL}$</tex> . 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 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{4}\ \boldsymbol{\mu} \mathbf{g}/\mathbf{mL}$</tex> 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 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{5},\ \mathbf{10},\ \mathbf{20},\ \mathbf{50},\ \mathbf{100},\ \mathbf{200}\ \boldsymbol{\mu} \mathbf{g}/\mathbf{mL}$</tex> . The result was evaluated by measuring the zone of bacterial growth inhibition. Both supernatant (containing <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{Ag}^{+}$</tex> 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, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{Ag}^{+}$</tex> ion in the samples.