Sustained Release from Injectable Composite Gels Loaded with Silver Nanowires Designed to Combat Bacterial Resistance in Bone Regeneration Applications

Abstract

One-dimensional nanostructures such as silver nanowires (AgNWs) have attracted considerable attention owing to their outstanding electrical, thermal and antimicrobial properties; however, their application in the prevention of infections linked to bone tissue regeneration interventions has not yet been explored. Here we report on the development of an innovative scaffold prepared from chitosan, composite hydroxyapatite and AgNWs (CS-HACS-AgNWs) having both bioactive and antibacterial properties. In vitro results highlighted the antibacterial potential of AgNWs against both gram-positive and gram-negative bacteria. The CS-HACS-AgNWs composite scaffold demonstrated suitable Ca/P deposition, improved gel strength, reduced gelation time, and sustained Ag + release within therapeutic concentrations. Antibacterial studies showed that the composite formulation was capable of inhibiting bacterial growth in suspension and of completely preventing biofilm formation on the scaffold in the presence of resistant strains. The hydrogels were also shown to be biocompatible, allowing cell proliferation. In summary, the developed CS-HACS-AgNWs composite hydrogels demonstrated significant potential as a scaffold material to be employed in bone regenerative medicine, as they present enhanced mechanical strength combined with the ability to allow calcium salts deposition, while efficiently decreasing the risk of infections. The results presented justify further investigations into potential clinical applications of these materials.to the bulk materials due to their reduced dimensions, controlled structure and large surface-tovolume ratio [3].One, two, and three-dimensional silver nanostructures have been previously reported, with many studies focusing on silver nanowires (AgNWs). AgNWs are anisotropically grown to obtain an aspect ratio higher than 10 and are typically 10-200 nm in diameter and 5-100 µm in length [2]. To date, silver nanoparticles (AgNPs) have been much more extensively studied than AgNWs, and their distinctive high thermal and electrical conductivity, surface-enhanced Raman scattering, chemical stability, catalytic activity and non-linear optical behavior have been highlighted; as well as their antibacterial activity that has extended their usage into several biomedical fields [4]. They are promising agents against a wide range of fungi, viruses and bacterial species; even though the mechanism of action is still not entirely understood, it is believed that nanosilver serves as a source for Ag + ions that can rupture microbial cell walls, denature proteins, block cell respiration and eventually induce cell death [5]. AgNPs have been used as antimicrobial agents in wound dressing [6], coating of catheters [7] and of cardiovascular implants [8], bone cements [9] and dental materials [10]. Currently literature on biomedical applications of AgNWs is still limited [2]; emerging applications include textiles [11], wound coatings [12], drug release and tissue regeneration [13].In this work, we explore for the first time the...

Antibacterial PMMA Composite Cements with Tunable Thermal and Mechanical Properties

“…11 Chitosan and AgNW combinations in the PMMA cements, similarly to our previous study on composite hydrogels, show that the activity of AgNWs is potentiated by the presence of chitosan due to a synergic activity. 14 The same combination provides good cell viability when the concentration of chitosan is lower than 20% w/w.…”

“…AgNWs were synthetized using the polyol method, as previously described. 14 AgNWs, with an average length of 5 μm and an average diameter of 99 nm, were obtained. 14 Preparation of Composite PMMA Cements.…”

“…14 AgNWs, with an average length of 5 μm and an average diameter of 99 nm, were obtained. 14 Preparation of Composite PMMA Cements. Cement formulations with different concentrations of additives and/or powder to liquid monomer ratio (Table 1) have been prepared and tested.…”

“…In the present work, we report the preparation and characterization of novel PMMA composites containing chitosan (CS) or methacryloyl chitosan (CSMCC) to reduce polymerization temperature, modify mechanical behavior, and favor the formation of pores, and AgNWs that can offer a prolonged antibacterial effected by a controlled silver ion release, more sustained than spherical nanoparticles. 13,14 We further investigated the cytocompatibility, antibacterial, and mechanical properties of the composites.…”

Local treatment of experimental mandibular osteomyelitis with an injectable biomimetic gentamicin hydrogel using a new rabbit model

“…As a subtype of these biomaterials, injectable biomimetic hydrogels could be an attractive option in the local treatment of OM. Bioactive hydrogels have been investigated for local treatment of bone infection and bone regeneration 23‐25 but not for the treatment of mandible OM to date.…”