Can Differently Stabilized Silver Nanoparticles Modify Calcium Phosphate Precipitation?

Abstract

Calcium phosphates (CaPs) composites with silver nanoparticles (AgNPs) attract attention as a possible alternative to conventional approaches to combating orthopedic implant-associated infections. Although precipitation of calcium phosphates at room temperatures was pointed out as an advantageous method for the preparation of various CaP-based biomaterials, to the best of our knowledge, no such study exists for the preparation of CaPs/AgNP composites. Motivated by this lack of data in this study we investigated the influence of AgNPs stabilized with citrate (cit-AgNPs), poly(vinylpyrrolidone) (PVP-AgNPs), and sodium bis(2-ethylhexyl) sulfosuccinate (AOT-AgNPs) in the concentration range 5–25 mg dm−3 on the precipitation of CaPs. The first solid phase to precipitate in the investigated precipitation system was amorphous calcium phosphate (ACP). The effect of AgNPs on ACP stability was significant only in the presence of the highest concentration of AOT-AgNPs. However, in all precipitation systems containing AgNPs, the morphology of ACP was affected, as gel-like precipitates formed in addition to the typical chain-like aggregates of spherical particles. The exact effect depended on the type of AgNPs. After 60 min of reaction time, a mixture of calcium-deficient hydroxyapatite (CaDHA) and a smaller amount of octacalcium phosphate (OCP) formed. PXRD and EPR data point out that the amount of formed OCP decreases with increasing AgNPs concentration. The obtained results showed that AgNPs can modify the precipitation of CaPs and that CaPs properties can be fine-tuned by the choice of stabilizing agent. Furthermore, it was shown that precipitation can be used as a simple and fast method for CaP/AgNPs composites preparation which is of special interest for biomaterials preparation.

Comparison of bovine serum albumin and chitosan effects on calcium phosphate formation in the presence of silver nanoparticles

“…52 However, in the presence of AgNPs alone, no additional regions in pH vs. time curves were observed. 26 Therefore, it appeared, that only certain combinations of macromolecules and AgNPs can lead to a change in the CaPs formation pathway. At all concentrations studied, both biomacromolecules prolonged the rate of ACP transformation to the crystalline phase compared to the control system, as evidenced by increased induction time for secondary precipitation of crystalline phase on already formed ACP (t i , Table 2).…”

“…SI 6 †), are in agreement with our previous study. 26 In the PXRD pattern characteristic OCP peaks at 2q 4.6°and 9.4°corresponding to (100) and ( 200) reections (JCPDS Card No. : 074-1301) were observed.…”

“…In our previous study, it was shown that at the applied AgNPs concentration OCP formation was inhibited in the presence of AOT-AgNPs and PVP-AgNPs. 26 It can be concluded that the effects on a composition of the precipitates formed depend on the specic combination of AgNPs and biomacromolecules. Smaller changes were observed in the FTIR spectra (Fig.…”

“…18,28 In addition, previous investigations have shown that these types of AgNPs are relatively stable in complex media. 26,29 BSA is commonly used as a model compound for drug delivery systems and also as a way of enhancing the bioactivity of CaPs. 7,[30][31][32] It is an abundant protein, very similar to human serum albumin, and inexpensive.…”

“…Recently, we have shown that agglomeration can be avoided if CaPs are precipitated in the presence of AgNPs. 26 Moreover, differently stabilized AgNPs, differing in antibacterial activity, 27 can be used for precipitation, which may have a different effect on CaPs properties. 26 Consequently, both the physico-chemical and biological properties of CaP/AgNPs can be tailored in a simple manner by using differently stabilized AgNPs as an additive in CaPs precipitation.…”