Fabrication and Evaluation of Layered Double Hydroxide-Enriched ß-Tricalcium Phosphate Nanocomposite Granules for Bone Regeneration: In Vitro Study

Layered Double Hydroxides: A Novel Promising 2D Nanomaterial for Bone Diseases Treatment

Bone diseases including bone defects, bone infections, osteoarthritis, and bone tumors seriously affect life quality of the patient and bring serious economic burdens to social health management, for which the current clinical treatments bear dissatisfactory therapeutic effects. Biomaterial-based strategies have been widely applied in the treatment of orthopedic diseases but are still plagued by deficient bioreactivity. With the development of nanotechnology, layered double hydroxides (LDHs) with adjustable metal ion composition and alterable interlayer structure possessing charming physicochemical characteristics, versatile bioactive properties, and excellent drug loading and delivery capabilities arise widespread attention and have achieved considerable achievements for bone disease treatment in the last decade. However, to the authors' best knowledge, no review has comprehensively summarized the advances of LDHs in treating bone disease so far. Herein, the advantages of LDHs for orthopedic disorders treatment are outlined and the corresponding state-of-the-art achievements are summarized for the first time. The potential of LDHs-based nanocomposites for extended therapeutics for bone diseases is highlighted and perspectives for LDHs-based scaffold design are proposed for facilitated clinical translation.

Surface modification of two-dimensional layered double hydroxide nanoparticles with biopolymers for biomedical applications

Layered double hydroxides (LDHs) are appealing nanomaterials for (bio)medical applications and their potential is threefold. One can gain advantage of the structure of LDH frame (i.e., layered morphology), anion exchanging property towards drugs with acidic character and tendency for facile surface modification with biopolymers. This review focuses on the third aspect, as it is necessary to evaluate the advantages of polymer adsorption on LDH surfaces. Beside the short discussion on fundamental and structural features of LDHs, LDH-biopolymer interactions will be classified in terms of the effect on the colloidal stability of the dispersions. Thereafter, an overview on the biocompatibility and biomedical applications of LDH-biopolymer composite materials will be given. Finally, the advances made in the field will be summarized and future research directions will be suggested.

The effect of LDHs nanoparticles on the cellular behavior of stem cell-laden 3D-bioprinted scaffold

Three-dimensional (3D)-bioprinting as an emerging approach for tissue engineering possesses the promise to create highly mimicked organs or tissues by using computer-aided design. For biomedical applications in tissue engineering in our previous work, we developed an optimized nanocomposite bioink based on methylacrylated gelatin (GelMA), methylacrylated chitosan (ChitMA), and double-layered hydroxide (LDHs) nanoparticles by using 3D-bioprinting technology. Herein, we used the previous formulation to fabricate human bone marrow mesenchymal stem cells (hBMMSCs)-laden nanocomposite bioinks. The effect of LDHs nanoparticles on the cellular behaviors of the encapsulated-hBMMSCs in the scaffolds was evaluated for the first time. Live/Dead, PrestoBlue, and DAPI/Actin analysis were carried out to assess the cell viability, proliferation rate, and cellular morphology of encapsulated hBMMSCs within the scaffolds. In addition, osteogenic differentiation studies were performed culturing the scaffolds for up to 21 days. Results show that LDHs nanoparticles in the GelMA/ChitMA scaffold formulation increased the viability of hBMMSCs, did not cause any adverse effect on the proliferation rate, cell morphology of the hBMMSCs, and increased the Runx2 protein expression of the encapsulated-hBMMSCs in the scaffolds. This study progresses the LDHs containing nanocomposite bioink for cell printing applications in tissue engineering.

Preparation and characterization of electrospun polycaprolactone/brushite scaffolds to promote osteogenic differentiation of mesenchymal stem cells

Bone tissue engineering aims to develop effective strategies for repairing or replacing damaged bone tissue. In this study, composite scaffolds consisting of dicalcium phosphate dihydrate (DCDP, brushite) as a bone phase mineral precursor with different weight percentages (0%, 1%, 3%, 5%, and 10%) in combination with polycaprolactone (PCL) were fabricated by electrospinning technique. The morphology and mechanical behavior of scaffolds were characterized using scanning electron microscopy and tensile strength test, respectively. The bioactivity of scaffolds was assessed in simulated body fluid. Adhesion, viability, proliferation, and differentiation of mesenchymal stem cells derived from the human bone marrow on scaffolds were investigated using electron microscopy, MTT assay, live-dead assay, alizarin red staining, alkaline phosphatase activity and, gene expression analysis by real-time PCR. The results showed that the scaffold containing 3 wt. % of DCDP had the highest tensile strength (15.35 MPa). Furthermore, cells seeded on scaffolds showed over 80% viability after 1, 3, 7 days of incubation. Also, the results showed that the addition of DCDP to the PCL significantly increased the alkaline phosphatase activity. The osteocalcin gene expression in the composite scaffold showed a 6.1-fold increase compared to the pure PCL scaffold. It is concluded that electrospun PCL scaffolds containing DCDP with optimum concentration can be a proper candidate for bone tissue engineering applications.

Calcined Hydroxyapatite with Collagen I Foam Promotes Human MSC Osteogenic Differentiation

Collagen I-based foams were modified with calcined or noncalcined hydroxyapatite or calcium phosphates with various particle sizes and pores to monitor their effect on cell interactions. The resulting scaffolds thus differed in grain size, changing from nanoscale to microscopic, and possessed diverse morphological characteristics and resorbability. The materials' biological action was shown on human bone marrow MSCs. Scaffold morphology was identified by SEM. Using viability test, qPCR, and immunohistochemical staining, we evaluated the biological activity of all of the materials. This study revealed that the most suitable scaffold composition for osteogenesis induction is collagen I foam with calcined hydroxyapatite with a pore size of 360 ± 130 µm and mean particle size of 0.130 µm. The expression of osteogenic markers RunX2 and ColI mRNA was promoted, and a strong synthesis of extracellular protein osteocalcin was observed. ColI/calcined HAP scaffold showed significant osteogenic potential, and can be easily manipulated and tailored to the defect size, which gives it great potential for bone tissue engineering applications.

In vivo evaluation of bone regeneration behavior of novel β-tricalcium phosphate/layered double hydroxide nanocomposite granule as bone graft substitutes

This study was based on in vivo assessment of bone regeneration capacity of synthesized porous β-tricalcium phosphate (β-TCP) nanocomposite granules and aimed to explore the effects of fabricated β-TCP granules reinforced with layered double hydroxides (LDH) nanoclay compared to β-TCP granules, in terms of osteoconductivity and biodegradability. Granules with diameters of 2-3 mm were implanted into cavities drilled in rabbit distal femur and were left in situ for up to 3 months. The mechanical study demonstrated that the presence of LDH nanoparticles in β-TCP granules resulted in a significant increase in compressive modulus from 174.4 to 231.4 MPa, while the porosity was constant at 76%-80%. The results revealed that the obtained granules showed no cytotoxicity. In this study, x-ray radiographic, micro-computed tomography, and histological staining analysis were taken to evaluate the percentage of bone ingrowth and biodegradability of the porous granules. The results exhibited that both granules support bone regeneration and also the amount of new bone formation in the bone defect filled with both granules was almost six times higher than the empty defects. Although no significant difference in bone formation for two different granules was observed, a higher biodegradability was detected in β-TCP granules in comparison to β-TCP/LDH granules. Overall, the addition of LDH nanoclay (10%) enhanced the physicochemical and mechanical properties of β-TCP granules while it is biological and osteoconductity properties have been maintained and its biodegradation rate has been decreased.