Abstract

Copper (Cu) ions have a variety of advantageous biological functionalities, such as proangiogenic and bactericidal activities. Given the intrinsic biodegradability and biocompatibility, silicate-based mesoporous bioactive glass nanoparticles (MBGNs) are considered as promising platforms for the delivery of Cu ions. However, effective incorporation of Cu into MBGNs still faces challenges, e.g., particle aggregation, the formation of insoluble crystalline Cu-based nanoparticles, and a low loading amount of Cu. We report a novel method to synthesize chemically homogenous and highly dispersed Cu-containing MBGNs (Cu-MBGNs) with tunable Cu concentration by using ascorbic acid/Cu complexes as the precursor of Cu in a microemulsion-assisted sol-gel approach. Cu-MBGNs exhibited a sphere-like shape with a particle size between 100 and 300 nm while their pore size varied from 2 to 10 nm. The inclusion of Cu, regardless of the incorporated concentration, did not significantly affect the morphology of particles. ICP-AES results indicated that the concentration of Cu in the particles could be conveniently tuned from 0 to ~6 mol% by controlling the amount of ascorbic acid/Cu complexes added, while the formation of crystalline Cu-based nanoparticles was avoided. The amorphous feature of Cu-MBGNs was proved by XRD, while the predominant oxidation state of Cu was evidenced to be Cu2+ by XPS. The incorporation of Cu did not inhibit the apatite-forming ability (bioactivity) of the particles in contact with simulated body fluid. Cu-MBGNs exhibited the capability of releasing Cu, Si, and Ca ions over time in the physiological fluid. The concentration of released Cu ions could be controlled by selecting specific Cu-MBGNs of different Cu contents. The dissolution products of most Cu-MBGNs at the dosage of 1, 0.1, and 0.01 mg/mL did not exhibit cytotoxicity, while only 7Cu-MBGN was cytotoxic at the dosage of 1 mg/mL. This study provided a feasible strategy to synthesize highly dispersed amorphous Cu-MBGNs with high Cu concentrations for biomedical applications. The particles exhibit great potential as building blocks for developing composite 3D scaffolds, coatings, and drug carriers, particularly when a large amount of particles incorporated may compromise the properties of (polymer) matrix materials while a relatively high concentration of released Cu ions is still required.

Highlights

  • Mesoporous bioactive glass nanoparticles (MBGNs) are preferable biomaterials in a variety of biomedical applications, due to their tailorable morphology and favorable physicochemical properties (Vichery and Nedelec, 2016; Zheng and Boccaccini, 2017)

  • The morphology is in good agreement with that of particles synthesized by using similar approaches reported in the literature (Liang et al, 2015; Nawaz et al, 2018). 1Cu-MBGN exhibited similar morphology to other Cu-MBGNs (Figure S1)

  • Smaller nanoparticles clustering on larger mesoporous particles could be observed in 10CuMBGN (Figure 1a) while no such particles were seen in other Cu-MBGNs and MBGN

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Summary

Introduction

Mesoporous bioactive glass nanoparticles (MBGNs) are preferable biomaterials in a variety of biomedical applications (e.g., bone regeneration, drug delivery), due to their tailorable morphology (e.g., size, pore structure) and favorable physicochemical properties (e.g., bone bonding ability, biodegradability) (Vichery and Nedelec, 2016; Zheng and Boccaccini, 2017). Their ionic dissolution products, depending on the composition and concentration, can induce a series of beneficial biological responses toward enhanced therapeutic activity (Hoppe et al, 2011). Being able to control the Cu concentration in a broad spectrum is critical to the application of Cu-containing BG for specific purposes (e.g., antibacterial or pro-angiogenic)

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