Functionalization of Hydroxyapatite Scaffolds with ZnO

3-D Cell Culture Systems in Bone Marrow Tissue and Organoid Engineering, and BM Phantoms as In Vitro Models of Hematological Cancer Therapeutics-A Review

We review the state-of-the-art in bone and marrow tissue engineering (BMTE) and hematological cancer tissue engineering (HCTE) in light of the recent interest in bone marrow environment and pathophysiology of hematological cancers. This review focuses on engineered BM tissue and organoids as in vitro models of hematological cancer therapeutics, along with identification of BM components and their integration as synthetically engineered BM mimetic scaffolds. In addition, the review details interaction dynamics of various BM and hematologic cancer (HC) cell types in co-culture systems of engineered BM tissues/phantoms as well as their relation to drug resistance and cytotoxicity. Interaction between hematological cancer cells and their niche, and the difference with respect to the healthy niche microenvironment narrated. Future perspectives of BMTE for in vitro disease models, BM regeneration and large scale ex vivo expansion of hematopoietic and mesenchymal stem cells for transplantation and therapy are explained. We conclude by overviewing the clinical application of biomaterials in BM and HC pathophysiology and its challenges and opportunities.

3D construct of hydroxyapatite/zinc oxide/palladium nanocomposite scaffold for bone tissue engineering

The purpose of this study was to produce and characterize Hydroxyapatite/Zinc Oxide/Palladium (HA/0.05 wt% ZnO/0.1 wt% Pd) nanocomposite scaffolds and study their mechanical and antibacterial properties, biocompatibility and bioactivity. The initial materials were developed using sol-gel and precipitation methods. Scaffolds were characterized using atomic absorption analysis (AA), scanning electron microcopy (SEM), energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM), atomic force microscopy (AFM) and Brunauer-EmmeS-Teller (BET) method. Furthermore, the bioactivity of scaffolds in simulated body fluid (SBF) and the interaction of dental pulp stem cells (DPSCs) with the nanocomposite scaffolds were assessed. Our results showed that the HA/ZnO/Pd (H1), HA/ZnO/Pd coated by 0.125 g chitosan (H2) and HA/ZnO/Pd coated by 0.25 g chitosan (H3) scaffolds possess higher compressive strength and toughness and lower microhardness and density compared to the pure HA (H0) scaffolds. Immersion of samples in SBF showed the deposition of apatite on the surface of the scaffolds. The biocompatibility assay indicated lower cell proliferation on the H1, H2 and H3 in comparison to the H0. The antibacterial results obtained show a significant impact by loading Pd/ZnO on HA in the deactivation of microorganisms in vitro.

Multifunctional hydroxyapatite with potential for application in theranostic nanomedicine

Although several materials are being studied for the development of theranostic systems, factors such as high costs, low yield, stability of nanoparticles (NPs) and toxicity-related issues hinder their application in medicine. Thus, this paper introduces the synthesis of a theranostic system composed of hydroxyapatite (HAp) functionalized with europium (Eu³⁺) and zinc oxide (ZnO) NPs, resulting in a low-cost material that presents biocompatibility, luminescence, antibacterial activity and whose synthesis method is simple. The Eu³⁺ - doped HAp was obtained through the precipitation method and the functionalization with ZnO occurred in the subsequent stage through the solid-state reaction method. The resulting material, [Ca_9.5Eu_0.5(PO₄)₆(OH)₂@ZnO], was characterized by several techniques where the photoluminescence spectrum exhibited sharp peaks at the 4f^N → 4f^N transitions typical of Eu³⁺ ions, while tests with bacteria proved its antibacterial property. The crystal structure obtained by X-ray diffraction confirmed HAp as the major phase. The multifunctional HAp (HAp:Eu@ZnO) was considered as hemocompatible, exhibiting an in vitro hemolysis ratio of 1.85 (±0.2) %, and its loading potential, tested for two antitumor drugs, showed an adsorption capacity of 43.0 ± 3.6% for 5-Fluorouracil and 84.0 ± 4.0% for curcumin. The cytotoxicity of the system as well as its use as a support for drugs was analyzed through in vitro assays with tumor cells from sarcoma 180 in mice. The results confirmed that HAp:Eu@ZnO is non-toxic to cells and its potential for antineoplastic vectorization is increased by cell internalization due to endocytosis, with up to 39.0% of cancer cell deaths having been observed at the concentrations and period evaluated.

Biodegradable zinc oxide composite scaffolds promote osteochondral differentiation of mesenchymal stem cells

Osteoarthritis (OA) involves the degeneration of articular cartilage and subchondral bone. The capacity of articular cartilage to repair and regenerate is limited. A biodegradable, fibrous scaffold containing zinc oxide (ZnO) was fabricated and evaluated for osteochondral tissue engineering applications. ZnO has shown promise for a variety of biomedical applications but has had limited use in tissue engineering. Composite scaffolds consisted of ZnO nanoparticles embedded in slow degrading, polycaprolactone to allow for dissolution of zinc ions over time. Zinc has well-known insulin-mimetic properties and can be beneficial for cartilage and bone regeneration. Fibrous ZnO composite scaffolds, having varying concentrations of 1-10 wt.% ZnO, were fabricated using the electrospinning technique and evaluated for human mesenchymal stem cell (MSC) differentiation along chondrocyte and osteoblast lineages. Slow release of the zinc was observed for all ZnO composite scaffolds. MSC chondrogenic differentiation was promoted on low percentage ZnO composite scaffolds as indicated by the highest collagen type II production and expression of cartilage-specific genes, while osteogenic differentiation was promoted on high percentage ZnO composite scaffolds as indicated by the highest alkaline phosphatase activity, collagen production, and expression of bone-specific genes. This study demonstrates the feasibility of ZnO-containing composites as a potential scaffold for osteochondral tissue engineering.