Assessment of synergistic interactions on self-assembled sodium alginate/nano-hydroxyapatite composites: to the conception of new bone tissue dressings

Bone Tissue Engineering and Nanotechnology: A Promising Combination for Bone Regeneration

Large bone defects are the leading contributor to disability worldwide, affecting approximately 1.71 billion people. Conventional bone graft treatments show several disadvantages that negatively impact their therapeutic outcomes and limit their clinical practice. Therefore, much effort has been made to devise new and more effective approaches. In this context, bone tissue engineering (BTE), involving the use of biomaterials which are able to mimic the natural architecture of bone, has emerged as a key strategy for the regeneration of large defects. However, although different types of biomaterials for bone regeneration have been developed and investigated, to date, none of them has been able to completely fulfill the requirements of an ideal implantable material. In this context, in recent years, the field of nanotechnology and the application of nanomaterials to regenerative medicine have gained significant attention from researchers. Nanotechnology has revolutionized the BTE field due to the possibility of generating nanoengineered particles that are able to overcome the current limitations in regenerative strategies, including reduced cell proliferation and differentiation, the inadequate mechanical strength of biomaterials, and poor production of extrinsic factors which are necessary for efficient osteogenesis. In this review, we report on the latest in vitro and in vivo studies on the impact of nanotechnology in the field of BTE, focusing on the effects of nanoparticles on the properties of cells and the use of biomaterials for bone regeneration.

Phenolated alginate hydrogel induced osteogenic properties of mesenchymal stem cells via Wnt signaling pathway

Osteogenic properties of phenolated alginate (1.2 %) hydrogel containing collagen (0.5 %)/nano-hydroxyapatite (1 %) were studied on human mesenchymal stem cells in vitro. The phenolation rate and physical properties of the hydrogel were assessed using nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FTIR), Scanning electron microscope (SEM), swelling ratio, gelation time, mechanical assay, and degradation rate. The viability of encapsulated cells was monitored on days 7, 14, and 21 using an MTT assay. Osteoblast differentiation was studied using western blotting, and real-time PCR. Using PCR array analysis, the role of the Wnt signaling pathway was also investigated. Data showed that the combination of alginate/collagen/nanohydroxyapatite yielded proper mechanical features. The addition of nanohydroxyapatite, and collagen reduced degradation, swelling rate coincided with increased stiffness. Elasticity and pore size were also diminished. NMR and FTIR revealed suitable incorporation of collagen and nanohydroxyapatite in the structure of alginate. Real-time PCR analysis and western blotting indicated the expression of osteoblast-related genes such as Runx2 and osteocalcin. PCR array revealed the induction of numerous genes related to Wnt signaling pathways during the maturation of human stem cells toward osteoblast-like cells. In vivo data indicated that transplantation of phenolated alginate/collagen/nanohydroxyapatite hydrogel led to enhanced de novo bone formation in rats with critical-sized calvarial defects. Phenolated alginate hydrogel can promote the osteogenic capacity of human amniotic membrane mesenchymal stem cells in the presence of nanohydroxyapatite and collagen via engaging the Wnt signaling pathway.

Enhanced bone tissue regeneration with hydrogel-based scaffolds by embedding parathyroid hormone in mesoporous bioactive glass

OBJECTIVES

To evaluate hydrogel-based scaffolds embedded with parathyroid hormone (PTH)-loaded mesoporous bioactive glass (MBG) on the enhancement of bone tissue regeneration in vitro.

MATERIALS AND METHODS

MBG was produced via sol-gel technique followed by PTH solution imbibition. PTH-loaded MBG was blended into the hydrogels and submitted to a lyophilisation process associated with a chemical crosslinking reaction to the production of the scaffolds. Characterisation of the MBG and PTH-loaded MBG scaffolds, including the scanning electron microscope (SEM) connected with an X-ray detector (EDX), Fourier transform infrared (FTIR), compression strength, rheological measurements, swelling and degradation rates, and PTH release analysis, were performed. Also, bioactivity using simulated-body fluid (SBF), biocompatibility (MTT), and osteogenic differentiation analyses (von Kossa and Alizarin Red stainings, and μ-computed tomography, μCT) of the scaffolds were carried out.

RESULTS

SEM images demonstrated MBG particles dispersed into the hydrogel-based scaffold structure, which was homogeneously porous and well interconnected. EDX and FTIR revealed large amounts of carbon, oxygen, sodium, and silica in the scaffold composition. Bioactivity experiments revealed changes on sample surfaces over the analysed period, indicating the formation of carbonated hydroxyapatite; however, the chemical composition remained stable. PTH-loaded hydrogel-based scaffolds were biocompatible for stem cells from human-exfoliated deciduous teeth (SHED). A high quantity of calcium deposits on the extracellular matrix of SHED was found for PTH-loaded hydrogel-based scaffolds. μCT images showed MBG particles dispersed into the scaffolds' structure, and a porous, lamellar, and interconnected hydrogel architecture.

CONCLUSIONS

PTH-loaded hydrogel-based scaffolds demonstrated consistent morphology and physicochemical properties for bone tissue regeneration, as well as bioactivity, biocompatibility, and osteoinductivity in vitro. Thus, the scaffolds presented here are recommended for future studies on 3D printing.

CLINICAL RELEVANCE

Bone tissue regeneration is still a challenge for several approaches to oral and maxillofacial surgeries, though tissue engineering applying SHED, scaffolds, and osteoinductive mediators might help to overcome this clinical issue.

Adsorption/desorption study of antibiotic and anti-inflammatory drugs onto bioactive hydroxyapatite nano-rods

The use of high doses of antibacterial and anti-inflammatory drugs for patients with bone diseases, associated to implants or bone filling, can develop adverse effects; and consequently, it promotes to think new strategies to avoid this problem. In this work, it has been described the adsorption/release (or desorption) behavior of two drugs, ciprofloxacin (CIP) and ibuprofen (IBU), onto hydroxyapatite (nano-HA) at 37 °C. Through Ultraviolet-Visible (UV-Vis) spectroscopy, the concentrations of both drugs in adsorption, kinetic and desorption processes were obtained. The Fourier Transformed-Infrared (FT-IR) spectroscopy, Zeta-potential (ζ-potential), High-Resolution Transmission Electron Microscopy (H-TEM) and x-Ray Diffraction (xRD) were also used to characterize bared nanoparticles and those with adsorbed drugs. Five adsorption models (Langmuir, Freundlich, Sips, Temkin and Dubinin-Radushkevich) were used for describing the behavior of both active compounds. The adsorption processes (CIP/nano-HA and IBU/nano-HA) were better predicted by the Sips model than by the others. The kinetic adsorption data were processed, for both active agents, by application of Avrami's model. Desorption/release process (of both drugs) was evaluated though Korsmeyer-Peppas (K-P) model. Owing to the predictability of these systems, we propose the use of these active ceramics as potential bone filler for improving the treatment against bacterial bone infections and to avoid its associated inflammatory process.