Biocompatible antibiotic-loaded mesoporous silica/bioglass/collagen-based scaffolds as bone drug delivery systems.

Local delivery of antibiotics has gained increasing interest in the treatment of osteomyelitis due to its effectiveness and safety. Since the regeneration of bone tissue at the site of infection is as important as bacterial eradication, implantable drug delivery systems should not only release the drugs in a proper manner but also exert the osseointegration capability. Herein, we present an implantable drug delivery system in a scaffold form with a unique set of features for local treatment of osteomyelitis. For the first time, collagen type I, ciprofloxacin-loaded mesoporous silica, and bioglass were combined to obtain scaffolds using the molding method. Drug-loaded mesoporous silica was blended with polydimethylsiloxane to prolong the drug release, whereas bioglass served as a remineralization agent. Collagen-silica scaffolds were evaluated in terms of physicochemical properties, drug release rate, mineralization potential, osteoblast response in vitro, antimicrobial activity, and biological properties using an in vivo preclinical model - chick embryo chorioallantoic membrane (CAM). The desirable multifunctionality of the proposed collagen-silica scaffolds was confirmed. They released the ciprofloxacin for 80 days, prevented biofilm development, and induced hydroxyapatite formation. Moreover, the resulting macroporous structure of the scaffolds promoted osteoblast attachment, infiltration, and proliferation. Collagen-silica scaffolds were also biocompatible and effectively integrated with CAM.

Magnetic Bone Tissue Engineering: Reviewing the Effects of Magnetic Stimulation on Bone Regeneration and Angiogenesis.

Bone tissue engineering emerged as a solution to treat critical bone defects, aiding in tissue regeneration and implant integration. Mainly, this field is based on the development of scaffolds and coatings that stimulate cells to proliferate and differentiate in order to create a biologically active bone substitute. In terms of materials, several polymeric and ceramic scaffolds have been developed and their properties tailored with the objective to promote bone regeneration. These scaffolds usually provide physical support for cells to adhere, while giving chemical and physical stimuli for cell proliferation and differentiation. Among the different cells that compose the bone tissue, osteoblasts, osteoclasts, stem cells, and endothelial cells are the most relevant in bone remodeling and regeneration, being the most studied in terms of scaffold-cell interactions. Besides the intrinsic properties of bone substitutes, magnetic stimulation has been recently described as an aid in bone regeneration. External magnetic stimulation induced additional physical stimulation in cells, which in combination with different scaffolds, can lead to a faster regeneration. This can be achieved by external magnetic fields alone, or by their combination with magnetic materials such as nanoparticles, biocomposites, and coatings. Thus, this review is designed to summarize the studies on magnetic stimulation for bone regeneration. While providing information regarding the effects of magnetic fields on cells involved in bone tissue, this review discusses the advances made regarding the combination of magnetic fields with magnetic nanoparticles, magnetic scaffolds, and coatings and their subsequent influence on cells to reach optimal bone regeneration. In conclusion, several research works suggest that magnetic fields may play a role in regulating the growth of blood vessels, which are critical for tissue healing and regeneration. While more research is needed to fully understand the relationship between magnetism, bone cells, and angiogenesis, these findings promise to develop new therapies and treatments for various conditions, from bone fractures to osteoporosis.

Nanomaterials in cancer: Reviewing the combination of hyperthermia and triggered chemotherapy.

Nanoparticle mediated hyperthermia has been explored as a method to increase cancer treatment efficacy by heating tumours inside-out. With that purpose, nanoparticles have been designed and their properties tailored to respond to external stimuli and convert the supplied energy into heat, therefore inducing damage to tumour cells. Moreover, the combination of hyperthermia with chemotherapy has been described as a more effective strategy due to the synergy between the high temperature and the drug's effects, also associated with a remote controlled and on-demand drug release. In this review, the methods behind nanoparticle mediated hyperthermia, namely material design, external stimuli response and energy conversion will be discussed and critically analysed. We will address the most relevant studies on hyperthermia and temperature triggered drug release for cancer treatment. Finally, the advantages, difficulties and challenges of this therapeutic strategy will be discussed, while giving insight for future developments.

Magnetic mesoporous silica nanoparticles as a theranostic approach for breast cancer: Loading and release of the poorly soluble drug exemestane.

Exemestane has a limited aqueous solubility that leads to a very high variability in absorption when administrated orally. It is crucial to develop strategies to increase the solubility and bioavailability of this drug. To overcome these issues, the aim of the present work was the development of magnetic silica mesoporous nanoparticles (IOMSNs) to carry and release exemestane. Furthermore, these nanoparticles could be also used as Magnetic Resonance Imaging (MRI) contrast agents for treatment monitorization and tumor detection. MRI analysis showed that IOMSNs present a concentration dependent contrast effect, revealing their potential for MRI applications. Also, IOMSNs present a very good polydispersity (0.224) and nanometric range size (137.2 nm). It was confirmed that the nucleus is composed by magnetite and the silica coating presents tubes with MCM-41-like hexagonal structure. Both iron oxide nanoparticles and iron oxide mesoporous silica nanoparticles were not toxic in cell culture for 24 h. Exemestane was successful released for 72 h following a typical sustained release pattern, achieving a very high loading capacity (37.7%) and in vitro release of 98.8%. Taking into account the results it is possible to conclude that IOMSNs have a high potential to be used as theranostic for intravenous breast cancer treatment with exemestane.

Enhanced biosafety of silica coated gadolinium based nanoparticles.

One of the most important and novel approaches of biomedical engineering is the development of new, effective and non-invasive medical diagnosis abilities, and treatments that have such requirements as advanced technologies for tumor imaging. Gadolinium (Gd) compounds can be used as MRI contrast agents, however the release of Gd3+ ions presents some adverse side effects such as renal failure, pancreatitis or local necrosis. The main aim of the work was the development and optimization of Gadolinium based nanoparticles coated with silica to be used as bioimaging agent. Gd based nanoparticles were prepared through a precipitation method and afterwards, these nanoparticles were covered with silica, using Stöber method with ammonia and functionalized with 3-Aminopropyltriethoxysilane (APTES). Results showed that nanoparticles were homogeneous regarding chemical composition, silica layer thickness, total size and morphology. Also, silica coating was successfully not degraded after 4 weeks at pH 5.5, 6.0 and 7.4, contrary to GdOHCO3 nanoparticles that degraded. Regarding the in vitro cell tests, very good cell proliferation and viability were observed. In conclusion, the results showed that Gd based nanoparticles coated with silica for imaging applications were successfully obtained under a well-controlled method. Furthermore, silica coating may enhance magnetic nanoparticles biosafety because it avoids GdOHCO3 degradation into harmful products (such as Gd3+ ions) at physiological conditions.

Different hydroxyapatite magnetic nanoparticles for medical imaging: Its effects on hemostatic, hemolytic activity and cellular cytotoxicity.

Magnetic nanoparticles (MNPs) should be highly biocompatible, stable and safely eliminated from the body, and can therefore be successfully used in modern medicine. Synthetic hydroxyapatite (HAP) has well established biocompatible and non-inflammatory properties, as well as a highly stable and flexible structure that allows for an easy incorporation of magnetic ions. This study characterized and compared the in vitro cytotoxicity and hemocompatibility of hydroxyapatite MNPs doped with different ions (Gd(3+/)Fe(2+)/Fe(3+)/Co(2+)). HAP doped with 10% of Gd and Fe(III) presented the highest magnetic moments. Our results showed that Gd doped HAP nanoparticles are non-cytotoxic, hemocompatible, non-hemolytic and non-thrombogenic, in contrast with Fe(III) doped HAP that can be considered thrombogenic. For these reasons we propose that, Gd doped HAP nanoparticles have the most potential for application as a MRI contrast agents. However, use of Fe (III) doped HAP as MRI contrast agents should be further investigated.

Modulation of human dermal microvascular endothelial cell and human gingival fibroblast behavior by micropatterned silica coating surfaces for zirconia dental implant applications.

Dental ceramic implants have shown superior esthetic behavior and the absence of induced allergic disorders when compared to titanium implants. Zirconia may become a potential candidate to be used as an alternative to titanium dental implants if surface modifications are introduced. In this work, bioactive micropatterned silica coatings were produced on zirconia substrates, using a combined methodology of sol-gel processing and soft lithography. The aim of the work was to compare the in vitro behavior of human gingival fibroblasts (HGFs) and human dermal microvascular endothelial cells (HDMECs) on three types of silica-coated zirconia surfaces: flat and micropatterned (with pillars and with parallel grooves). Our results showed that cells had a higher metabolic activity (HGF, HDMEC) and increased gene expression levels of fibroblast-specific protein-1 (FSP-1) and collagen type I (COL I) on surfaces with pillars. Nevertheless, parallel grooved surfaces were able to guide cell growth. Even capillary tube-like networks of HDMEC were oriented according to the surface geometry. Zirconia and silica with different topographies have shown to be blood compatible and silica coating reduced bacteria adhesion. All together, the results indicated that microstructured bioactive coating seems to be an efficient strategy to improve soft tissue integration on zirconia implants, protecting implants from peri-implant inflammation and improving long-term implant stabilization. This new approach of micropatterned silica coating on zirconia substrates can generate promising novel dental implants, with surfaces that provide physical cues to guide cells and enhance their behavior.