Bone injuries and fractures are often associated with post-surgical failures, extended healing times, infection, a lack of return to a normal active lifestyle, and corrosion associated allergies. In this regard, this review presents a comprehensive report on advances in nanotechnology driven solutions for bone tissue engineering. The fabrication of metals such as copper, gold, platinum, palladium, silver, strontium, titanium, zinc oxide, and magnetic nanoparticles with tunable physico-chemical and opto-electronic properties for osteogenic scaffolds is discussed here in detail. Furthermore, the rational selection of a polymeric base such as chitosan, collagen, poly (L-lactide), hydroxyl-propyl-methyl cellulose, poly-lactic-co-glycolic acid, polyglucose-sorbitol-carboxymethy ether, polycaprolactone, natural rubber latex, and silk fibroin for scaffold preparation is also discussed. These advanced materials and fabrication strategies not only provide for appropriate mechanical strength but also render integrity, making them appealing for orthopedic applications. Further, such scaffolds can be functionalized with ligands or biomolecules such as hydroxyapatite, polypyrrole (PPy), magnesium, zinc dopants, and growth factors to stimulate osteogenic differentiation, mineralization, and neovascularization to aid in rapid healing. Future directions to co-incorporate bioceramics, biogenic nanoparticles, and fourth generation biomaterials to enhance biocompatibility, mechanical properties, and rapid recovery are also included in this review. Hence, the further development of such biomimetic metal-based nano-scaffolds at a lower cost with reduced risks and greater efficacy at regrowing bone can revolutionize the future of orthopedics.

Metallic Nanoscaffolds as Osteogenic Promoters: Advances, Challenges and Scope

Modern biomedicine aims to develop integrated solutions that use medical, biotechnological, materials science, and engineering concepts to create functional alternatives for the specific, selective, and accurate management of medical conditions. In the particular case of tissue engineering, designing a model that simulates all tissue qualities and fulfills all tissue requirements is a continuous challenge in the field of bone regeneration. The therapeutic protocols used for bone healing applications are limited by the hierarchical nature and extensive vascularization of osseous tissue, especially in large bone lesions. In this regard, nanotechnology paves the way for a new era in bone treatment, repair and regeneration, by enabling the fabrication of complex nanostructures that are similar to those found in the natural bone and which exhibit multifunctional bioactivity. This review aims to lay out the tremendous outcomes of using inorganic nanoparticles in bone healing applications, including bone repair and regeneration, and modern therapeutic strategies for bone-related pathologies.

https://www.mdpi.com/1999-4923/14/4/770/pdf?version=1648809437

Inorganic Nanoparticles in Bone Healing Applications

To imitate the composition of natural bone and further improve the biological property of the materials, ZnO/hydroxyapatite/chitosan-polyethylene oxide@gelatin (ZnO/HAP/CS-PEO@GEL) composite scaffolds were developed. The core-shell structured chitosan-polyethylene oxide@gelatin (CS-PEO@GEL) nanofibers which could form the intramolecular hydrogen bond and achieve an Arg-Gly-Asp (RGD) polymer were first prepared by coaxial electrospinning to mimic the extracellular matrix. To further enhance biological activity, hydroxyapatite (HAP) was grown on the surface of the CS-PEO@GEL nanofibers using chemical deposition and ZnO particles were then evenly distributed on the surface of the above composite materials using RF magnetron sputtering. The SEM results showed that chemical deposition and magnetron sputtering did not destroy the three-dimensional architecture of materials, which was beneficial to cell growth. The cell compatibility and proliferation of MG-63 cells on ZnO/HAP/CS-PEO@GEL composite scaffolds were superior to those on CS-PEO@GEL and HAP/CS-PEO@GEL composite scaffolds. An appropriate amount of ZnO sputtering could promote the adhesion of cells on the composite nanofibers. The structure of bone tissue could be better simulated both in composition and in the microenvironment, which provided a suitable environment for cell growth and promoted the proliferation of MG-63 cells. The biomimetic ZnO/HAP/CS-PEO@GEL composite scaffolds were promising materials for bone tissue engineering.

Preparation and biological properties of ZnO/hydroxyapatite/chitosan-polyethylene oxide@gelatin biomimetic composite scaffolds for bone tissue engineering

The use of elastomer-based skins in morphing wings has become increasingly popular due to their remarkable stretchability and mechanical properties. However, the possibility of the skin fracturing during multiaxial stretching remains a significant design challenge. The propagation of cracks originating from flaws or notches in the skin can lead to the specimen breaking into two parts. This paper presents an experimental study aimed at comprehensively evaluating crack propagation direction, stretchability, and fracture toughness of silicone-based elastomeric skin (Ecoflex) for morphing wing applications, using varying Shore hardness values (10, 30, and 50). The findings show that the lower Shore hardness value of 10 exhibits a unique Sideways crack propagation characteristic, which is ideal for morphing skins due to its high stretchability, low actuation load, and high fracture toughness. The study also reveals that the Ecoflex 10 is suitable for use in span morphing, with a fracture toughness of approximately 1.1 kJ/m2 for all thicknesses at a slower strain rate of 0.4 mm/min. Overall, this work highlights the superior properties of Ecoflex 10 and its potential use as a morphing skin material, offering a groundbreaking solution to the challenges faced in this field.

/pdf/a-multiaxial-fracture-of-ecoflex-skin-with-different-shore-2o5ttctq.pdf

A Multiaxial Fracture of Ecoflex Skin with Different Shore Hardness for Morphing Wing Application

Biomimetic materials for better bone graft substitutes are a thrust area of research among researchers and clinicians. Autografts, allografts, and synthetic grafts are often utilized to repair and regenerate bone defects. Autografts are still considered the gold-standard method/material to treat bone-related issues with satisfactory outcomes. It is important that the material used for bone tissue repair is simultaneously osteoconductive, osteoinductive, and osteogenic. To overcome this problem, researchers have tried several ways to develop different materials using chitosan-based nanocomposites of silver, copper, gold, zinc oxide, titanium oxide, carbon nanotubes, graphene oxide, and biosilica. The combination of materials helps in the expression of ideal bone formation genes of alkaline phosphatase, bone morphogenic protein, runt-related transcription factor-2, bone sialoprotein, and osteocalcin. In vitro and in vivo studies highlight the scientific findings of antibacterial activity, tissue integration, stiffness, mechanical strength, and degradation behaviour of composite materials for tissue engineering applications.

Biomimetic chitosan with biocomposite nanomaterials for bone tissue repair and regeneration

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.

Reza Bazargan Lari

Papers

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