Graphene nanoplatelets (GNPs) are added as reinforcement to ultrahigh molecular weight polyethylene (UHMWPE) with an intended application for orthopedic implants. Electrostatic spraying is established as a potential fabrication method for synthesizing large-scale UHMWPE-GNP composite films. At a low concentration of 0.1 wt % GNP, the composite film shows highest improvement in fracture toughness (54%) and tensile strength (71%) as compared to UHMWPE. Increased GNP content of 1 wt % leads to improvement in elastic modulus and yield strength but fracture toughness and tensile strength are reduced significantly at higher GNP content. The strengthening mechanisms of the UHMWPE-GNP system are highly influenced by the GNP concentration, which dictates its degree of dispersion and extent of polymer wrapping. The fraction of GNPs oriented along the tensile axis influences the elastic deformation, whereas the wrapping of polymer and GNP-polymer interfacial strength determines the deformation behavior in the plastic regime. The cytotoxicity of GNP to osteoblast is dependent on its concentration and is also influenced by agglomeration of particles. Lowering the concentration of GNPs in UHMWPE improves the biocompatibility of the composite surface to bone cells. The survivability of osteoblasts deteriorates up to 86% on 1 wt % GNP containing surface, whereas much smaller (6-16%) reduction is observed for 0.1 wt % GNP over 5 days of incubation.

3916 wileyonlinelibrary.com such as high elastic modulus (1 TPa [ 7 ] ) and yield strength (≈130 GPa [ 6 ] ) which have been utilized in polymer, metal, and ceramic matrix composites in order to enhance their mechanical performance. One of the critical challenges for effective graphene-based composites is the uniform distribution of graphene in the composite matrix. The effective dispersion of graphene has been the subject of signifi cant research, with the most effective methods being limited by material systems or cost. The recent development of 3-D graphene foams (GrF) [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] represents a solution for providing uniform distributions of graphene in composites. 3-D graphene foams form an interconnected continuous network of graphene thus eliminating the need for expensive and/or ineffective dispersion methods.In this study we propose the use of a 3-D graphene foam/polymer composite as a fl exible high strength biocompatible scaffolding material for tissue engineering purposes. Graphene has been shown to be a biocompatible material in recent studies. [30][31][32] Human stem cells (neural and mesenchymal) survive and experience accelerated differentiation on a graphene surface. While several studies [11][12][13][14][15][16]23,27,28 ] have utilized the high surface area and macroporous structure of 3-D graphene foambased composites for energy storage applications, only a few studies to date [ 25,33 ] have exploited the inherent advantages of this unique structure for cell support, proliferation, and extracellular matrix (ECM) deposition. Studies on the biocompatibility of 3-D graphene foams have found that neural stem cells (NSCs) successfully proliferated and differentiated on the 3-D graphene structure. The porous 3-D graphene structure provides a microenvironment for the cells to grow within a 3-D biomimetic framework, while simultaneously enhancing the functionality of the electro-active neural cells by providing highly conductive pathways for charge transport. [ 33 ] Furthermore, 3-D graphene foams cultured with microglial cells exhibited antiinfl ammatory behavior not seen in 2-D graphene foams. [ 25 ] A few recent studies have also investigated the mechanical properties of graphene foam reinforced polymer composites. [34][35][36][37] Graphene foam/polymer composites exhibit superb fl exibility as evidenced by their recovery after compressive strains of up to 80% [ 36,37 ] and cyclic bending tests of nearly 180°. [ 34 ] The Three Dimensional Graphene Foam/Polymer Hybrid as a High Strength Biocompatible ScaffoldAndy Nieto , Rupak Dua , Cheng Zhang , Benjamin Boesl , Sharan Ramaswamy , and Arvind Agarwal * Graphene foam (GrF)/polylactic acid-poly-ε-caprolactone copolymer (PLC) hybrid (GrF-PLC) scaffold is synthesized in order to utilize both the desirable properties of graphene and that of foams such as excellent structural characteristics and a networked 3-D structure for cells to proliferate in. The hybrid scaffold is synthesized by a...

Articular cartilage injuries occur frequently in the knee joint. Photopolymerizable cartilage tissue engineering approaches appear promising; however, fundamentally, forming a stable interface between the subchondral bone and tissue engineered cartilage components remains a major challenge. We investigated the utility of hydroxyapatite (HA) nanoparticles to promote controlled bone-growth across the bone-cartilage interface in an in vitro engineered tissue model system using bone marrow derived stem cells. Samples incorporated with HA demonstrated significantly higher interfacial shear strength (at the junction between engineered cartilage and engineered bone) compared with the constructs without HA (p < 0.05), after 28 days of culture. Interestingly, this increased interfacial shear strength due to the presence of HA was observed as early as 7 days and appeared to have sustained itself for an additional three weeks without interacting with strength increases attributable to subsequent secretion of engineered tissue matrix. Histological evidence showed that there was ∼7.5% bone in-growth into the cartilage region from the bone side. The mechanism of enhanced engineered cartilage to bone integration with HA incorporation appeared to be facilitated by the deposition of calcium phosphate in the transition zone. These findings indicate that controlled bone in-growth using HA incorporation permits more stable anchorage of the injectable hydrogel-based engineered cartilage construct via augmented integration between bone and cartilage.

Polyether ether ketone (PEEK) is an organic polymer that has excellent mechanical, chemical properties and can be additively manufactured (3D-printed) with ease. The use of 3D-printed PEEK has been growing in many fields. This article systematically reviews the current status of 3D-printed PEEK that has been used in various areas, including medical, chemical, aerospace, and electronics. A search of the use of 3D-printed PEEK articles published until September 2021 in various fields was performed using various databases. After reviewing the articles, and those which matched the inclusion criteria set for this systematic review, we found that the printing of PEEK is mainly performed by fused filament fabrication (FFF) or fused deposition modeling (FDM) printers. Based on the results of this systematic review, it was concluded that PEEK is a versatile material, and 3D-printed PEEK is finding applications in numerous industries. However, most of the applications are still in the research phase. Still, given how the research on PEEK is progressing and its additive manufacturing, it will soon be commercialized for many applications in numerous industries.

We investigated the effectiveness of integrating tissue engineered cartilage derived from human bone marrow derived stem cells (HBMSCs) to healthy as well as osteoarthritic cartilage mimics using hydroxyapatite (HA) nanoparticles immersed within a hydrogel substrate. Healthy and diseased engineered cartilage from human chondrocytes (cultured in agar gels) were integrated with human bone marrow stem cell (HBMSC)-derived cartilaginous engineered matrix with and without HA, and evaluated after 28 days of growth. HBMSCs were seeded within photopolymerizable poly (ethylene glycol) diacrylate (PEGDA) hydrogels. In addition, we also conducted a preliminary in vivo evaluation of cartilage repair in rabbit knee chondral defects treated with subchondral bone microfracture and cell-free PEGDA with and without HA. Under in vitro conditions, the interfacial shear strength between tissue engineered cartilage derived from HBMSCs and osteoarthritic chondrocytes was significantly higher (p < 0.05) when HA nanoparticles were incorporated within the HBMSC culture system. Histological evidence confirmed a distinct spatial transition zone, rich in calcium phosphate deposits. Assessment of explanted rabbit knees by histology demonstrated that cellularity within the repair tissues that had filled the defects were of significantly higher number (p < 0.05) when HA was used. HA nanoparticles play an important role in treating chondral defects when osteoarthritis is a co-morbidity. We speculate that the calcified layer formation at the interface in the osteoarthritic environment in the presence of HA is likely to have attributed to higher interfacial strength found in vitro. From an in vivo standpoint, the presence of HA promoted cellularity in the tissues that subsequently filled the chondral defects. This higher presence of cells can be considered important in the context of accelerating long-term cartilage remodeling. We conclude that HA nanoparticles play an important role in engineered to native cartilage integration and cellular processes.