A crucial challenge to face in the treatment of biofilm-associated infection is the ability of bacteria to develop resistance to traditional antimicrobial therapies based on the administration of antibiotics alone. This study aims to apply magnetic hyperthermia together with controlled antibiotic delivery from a unique magnetic-responsive nanocarrier for a combination therapy against biofilm. The design of the nanosystem is based on antibiotic-loaded mesoporous silica nanoparticles (MSNs) externally functionalized with a thermo-responsive polymer capping layer, and decorated in the outermost surface with superparamagnetic iron oxide nanoparticles (SPIONs). The SPIONs are able to generate heat upon application of an alternating magnetic field (AMF), reaching the temperature needed to induce a change in the polymer conformation from linear to globular, therefore triggering pore uncapping and the antibiotic cargo release. The microbiological assays indicated that exposure of E. coli biofilms to 200 µg/mL of the nanosystem and the application of an AMF (202 kHz, 30 mT) decreased the number of viable bacteria by 4 log₁₀ units compared with the control. The results of the present study show that combined hyperthermia and antibiotic treatment is a promising approach for the effective management of biofilm-associated infections.

Despite the large number of synthesis methodologies described for superparamagnetic iron oxide nanoparticles (SPIONs), the search for their large-scale production for their widespread use in biomedical applications remains a mayor challenge. Flame Spray Pyrolysis (FSP) could be the solution to solve this limitation, since it allows the fabrication of metal oxide nanoparticles with high production yield and low manufacture costs. However, to our knowledge, to date such fabrication method has not been upgraded for biomedical purposes. Herein, SPIONs have been fabricated by FSP and their surface has been treated to be subsequently coated with dimercaptosuccinic acid (DMSA) to enhance their colloidal stability in aqueous media. The final material presents high quality in terms of nanoparticle size, homogeneous size distribution, long-term colloidal stability and magnetic properties. A thorough in vitro validation has been performed with peripheral blood cells and mesenchymal stem cells (hBM-MSCs). Specifically, hemocompatibility studies show that these functionalized FSP-SPIONs-DMSA nanoparticles do not cause platelet aggregation or impair basal monocyte function. Moreover, in vitro biocompatibility assays show a dose-dependent cellular uptake while maintaining high cell viability values and cell cycle progression without causing cellular oxidative stress. Taken together, the results suggest that the FSP-SPIONs-DMSA optimized in this work could be a worthy alternative with the benefit of a large-scale production aimed at industrialization for biomedical applications.

Nowadays, there is an ever-increasing interest in the development of systems able to guide and influence cell activities for bone regeneration. In this context, we have explored for the first time the combination of type-I collagen and superparamagnetic iron oxide nanoparticles (SPIONs) to design magnetic and biocompatible electrospun scaffolds. For this purpose, SPIONs with a size of 12 nm were obtained by thermal decomposition and transferred to an aqueous medium via ligand exchange with dimercaptosuccinic acid (DMSA). The SPIONs were subsequently incorporated into type-I collagen solutions to prove the processability of the resulting hybrid formulation by means of electrospinning. The optimized method led to the fabrication of nanostructured scaffolds composed of randomly oriented collagen fibers ranging between 100 and 200 nm, where SPIONs resulted distributed and embedded into the collagen fibers. The SPIONs-containing electrospun structures proved to preserve the magnetic properties of the nanoparticles alone, making these matrices excellent candidates to explore the magnetic stimuli for biomedical applications. Furthermore, the biological assessment of these collagen scaffolds confirmed high viability, adhesion, and proliferation of both pre-osteoblastic MC3T3-E1 cells and human bone marrow-derived mesenchymal stem cells (hBM-MSCs).

In this manuscript, we propose a simple and versatile methodology to design nanosystems based on biocompatible and multicomponent mesoporous silica nanoparticles (MSNs) for infection management. This strategy relies on the combination of antibiotic molecules and antimicrobial metal ions into the same nanosystem, affording a significant improvement of the antibiofilm effect compared to that of nanosystems carrying only one of these agents. The multicomponent nanosystem is based on MSNs externally functionalized with a polyamine dendrimer (MSN-G3) that favors internalization inside the bacteria and allows the complexation of multiactive metal ions (MSN-G3-Mⁿ⁺). Importantly, the selection of both the antibiotic and the cation may be done depending on clinical needs. Herein, levofloxacin and Zn²⁺ ion, chosen owing to both its antimicrobial and osteogenic capability, have been incorporated. This dual biological role of Zn²⁺ could have and adjuvant effect thought destroying the biofilm in combination with the antibiotic as well as aid to the repair and regeneration of lost bone tissue associated to osteolysis during infection process. The versatility of the nanosystem has been demonstrated incorporating Ag⁺ ions in a reference nanosystem. In vitro antimicrobial assays in planktonic and biofilm state show a high antimicrobial efficacy due to the combined action of levofloxacin and Zn²⁺, achieving an antimicrobial efficacy above 99% compared to the MSNs containing only one of the microbicide agents. In vitro cell cultures with MC3T3-E1 preosteoblasts reveal the osteogenic capability of the nanosystem, showing a positive effect on osteoblastic differentiation while preserving the cell viability. STATEMENT OF SIGNIFICANCE: A simple and versatile methodology to design biocompatible and multicomponent MSNs based nanosystems for infection management is proposed. These nanosystems, containing two antimicrobial agents, levofloxacin and Zn²⁺, have been synthetized by external functionalization of MSNs with a polycationic dendrimer (MSNs-G3), which favours its internalization inside the bacteria and lead the complexation with metal ions through the amines of the dendrimer. The nanosystems offer a notable improvement of the antibiofilm effect (above 99%) than both components separately as well as osteogenic capability with positive effect on the osteoblastic differentiation and preserved cell viability.

Background: Recently, magnetic composite biomaterials have raised attention in bone tissue engineering as the application of dynamic magnetic fields proved to modulate the proliferation and differentiation of several cell types. Methods: This study presents a novel method to fabricate biofunctional magnetic scaffolds by the deposition of superparamagnetic iron oxide nanoparticles (SPIONs) through thermal Drop-On-Demand inkjet printing on three-dimensional (3D) printed scaffolds. Firstly, 3D scaffolds based on thermoplastic polymeric composed by poly-L-lactic acid/poly-caprolactone/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) were fabricated by Fused Deposition Modelling. Then, in a second step, SPIONs were incorporated onto the surface of the scaffolds by inkjet printing following a designed 2D pattern. Results: A complete characterization of the resulting magnetic scaffolds was carried out attending to the surface SPIONs deposits, demonstrating the accuracy and versatility of the production technique, as well as the stability under physiological conditions and the magnetic properties. Biological evaluation with human bone marrow mesenchymal stems cells demonstrated biocompatibility of the scaffolds and increased osteogenic capability under the application of a magnetic field, due to the activation of mechanotransduction processes. Conclusion: These results show that the developed 3D magnetic biofunctional scaffolds can be a very promising tool for advanced and personalised bone regeneration treatments. Graphical