Effect of Sr^(2+)on 3D gel-printed Sr_(3-x)Mg_(x)(PO_(4))_(2)composite scaffolds for bone tissue engineering

Porous magnesium strontium phosphate(Sr_(3-x)Mg_(x)(PO_(4))_(2))(x=2,2.5,3)composite scaffolds were successfully prepared by three dimension gel-printing(3DGP)method in this study.The results show that Sr_(0.5)Mg_(2.5)(PO_(4))_(2)scaffolds had good compressive strength,and Sr_(1.0)Mg_(2.0)(PO_(4))_(2)scaffolds had good degradation rate in vitro.The weight loss rate of Sr_(1.0)Mg_(2.0)(PO_(4))_(2)scaffolds soaked in simulated body fluid(SBF)or 6 weeks was 6.96%,and pH value varied between 7.50 and 8.61,which was within the acceptable range of human body.Preliminary biological experiment shows that MC3T3-E1 cells had good adhesion and proliferation on the surface of Sr_(3-x)Mg_(x)(PO_(4))_(2)scaffolds.Compared with pure Mg3(PO_(4))_(2)scaffolds,strontium doped scaffolds had excellent comprehensive properties,which explain that Sr_(3-x)Mg_(x)(PO_(4))_(2)composite scaffolds can be used for bone tissue engineering.

Mechanistic Insights of Cells in Porous Scaffolds via Integrated Culture Technologies

This research aimed to combine 3 cell and tissue culture technologies to obtain mechanistic insights of cells in porous scaffolds. When cultivated on 2D （2-dimensional） surfaces, HDFs （human dermal fibroblasts） behaved individually and had no strict requirement on seeding density for proliferation; while HaCat cells relied heavily on initial densities for proliferation and colony formation, which was facilitated when co-cultured with HDFs. Experiments using a 3D CCIS （3-dimensional cell culture and imaging system） indicated that HDFs colonised openpores of varying sizes （125-420 ~tm） on modular substrates via bridge structures; while HaCat cells formed aperture structures and only colonised small pores （125 txm）. When co-cultured, HDFs not only facilitated HaCat attachment on the substrates, but also coordinated with HaCat cells to colonise open pores of varying sizes via bridge and aperture structures. Based on these observations, a 2-stage strategy for the culture of HDFs and HaCat cells on porous scaffolds was proposed and applied successfully on a cellulosic scaffold. This research demonstrated that cell colonisation in scaffolds was dependent on multiple factors; while the integrated 2D＆3D culture technologies and the 3D CCIS was an effective and efficient approach to obtain mechanistic insights of their influences on tissue regeneration.

Early Clinical Outcomes with a 3-D Porous Titanium Acetabular Cup

Cementless acetabular components are associated with a significant incidence of polyethylene wear and secondary osteolysis. 3-dimentional (3-D) porous coating and enhanced shell to a liner fixation are expected to reduce the polyethylene wear and to increase the longevity of an acetabular cup. The authors report the early clinical outcome with a cementless acetabular cup, Regenerex Ringloc+ (Zimmer Biomet, Warsaw, IN) for total hip arthroplasty. Between 2007 and 2013, the registry with 476 hip joints was reviewed retrospectively. There were 210 (48.4%) female and 224 (51.6%) male patients. The average age of the patients at the surgery was 63.9 (± 12.0) years and the average follow-up period was 2.6 years [0.5, 6.5]. At the final follow-up, there was no loosening or cup failure. There were 2 infections, 1 dislocation and 1 liner fracture, resulting in revision hip surgery. Average Harris hip score improved from 53.9 preoperatively to 91.4 postoperatively. The survivorship of Regenerex Ring Loc+ cup and the low complication rate is comparable with previous studies using other 3-D porous metal prostheses. Although this short-term outcome from the institute is very encouraging, a longer follow-up study is required.

Fabrication and Characterization of Poly Lactic Acid Scaffolds by Fused Deposition Modeling for Bone Tissue Engineering

Three-dimensional porous poly-lactic acid(PLA) scaffold was fabricated using fused deposition modeling(FDM) method including 30%, 50% and 70% nominal porosity. Study of phases in initial polymeric material and printed scaffolds was done by X-ray diffraction(XRD), and no significant phase difference was observed due to the manufacturing process, and the poly-lactic acid retains its crystalline properties. The results of the mechanical properties evaluation by the compression test show that the mechanical properties of the scaffold have decreased significantly with increasing the porosity of scaffold. The microstructure of scaffolds were studied by scanning electron microscope(SEM), showing that the pores had a regular arrangement and their morphology changed with porosity change. The mechanical properties of the poly-lactic acid scaffolds printed using fused deposition modeling, can be adapted to the surrounding tissue, by porosity change.

Biomimetic hydroxyapatite coating on the 3D-printed bioactive porous composite ceramic scaffolds promoted osteogenic differentiation via PI3K/AKT/mTOR signaling pathways and facilitated bone regeneration in vivo

The architecture and surface modifications have been regarded as effective methods to enhance the bi-ological response of biomaterials in bone tissue engineering.The porous architecture of the implanta-tion was essential conditions for bone regeneration.Meanwhile,the design of biomimetic hydroxyap-atite(HAp)coating on porous scaffolds was demonstrated to strengthen the bioactivity and stimulate osteogenesis.However,bioactive bio-ceramics such asβ-tricalcium phosphate(β-TCP)and calcium sili-cate(CS)with superior apatite-forming ability were reported to present better osteogenic activity than that of HAp.Hence in this study,3D-printed interconnected porous bioactive ceramicsβ-TCP/CS scaf-fold was fabricated and the biomimetic HAp apatite coating were constructed in situ via hydrothermal reaction,and the effects of HAp apatite layer on the fate of mouse bone mesenchymal stem cells(mBM-SCs)and the potential mechanisms were explored.The results indicated that HAp apatite coating en-hanced cell proliferation,alkaline phosphatase(ALP)activity,and osteogenic gene expression.Further-more,PI3K/AKT/mTOR signaling pathway is proved to have an important impact on cellular functions.The present results demonstrated that the key molecules of phosphatidylinositol 3-kinase(PI3K),protein kinase B(AKT)and mammalian target of rapamycin(mTOR)were activated after the biomimetic hydrox-yapatite coating were constructed on the 3D-printed ceramic scaffolds.Besides,the activated influence on the protein expression of Runx2 and BMP2 could be suppressed after the treatment of inhibitor HY-10358.In vivo studies showed that the constructed HAp coating promoted bone formation and strengthen the bone quality.These results suggest that biomimetic HAp coating constructed on the 3D-printed bioac-tive composite scaffolds could strengthen the bioactivity and the obtained biomimetic multi-structured scaffolds might be a potential alternative bone graft for bone regeneration.

Three-dimensional oxygen-doped porous graphene:Sodium chloridetemplate preparation,structural characterization and supercapacitor performances

Supercapacitor is a new type of energy storage device,which has the advantages of high-power property and long cycle life.In this study,three-dimensional graphene(3 D-GN)with oxygen doping and porous structure was prepared from graphene oxide(GO)by an inexpensive sodium chloride(NaCl)template,as a promising electrode material for the supercapacitor.The structure,morphology,specific surface area,pore size,of the sample were characterized by XRD,SEM,TEM and BET techniques.The electrochemical performances of the sample were tested by CV and CDC techniques.The 3 D-GE product is a threedimensional nano material with hierarchical porous structures,its specific surface area is much larger than that of routine stacked graphene(GN),and it contains a large number of mesoporous and macropores,a small amount of micropores.The capacitance characteristics of the 3 D-GN electrode material are excellent,showing high specific capacitance(173.5 F·g^(-1)at 1 A·g^(-1)),good rate performance(109.2 F·g^(-1)at 8 A·g^(-1))and long cycle life(88%capacitance retention after 10,000 cycles at 8 A·g^(-1))

3D-printed bioactive ceramic scaffolds with biomimetic micro/nano-HAp surfaces mediated cell fate and promoted bone augmentation of the bone-implant interface in vivo

Calcium phosphate bio-ceramics are osteo-conductive,but it remains a challenge to promote the induction of bone augmentation and capillary formation.The surface micro/nano-topography of materials can be recognized by cells and then the cell fate are mediated.Traditional regulation methods of carving surface structures on bio-ceramics employ mineral reagents and organic additives,which might introduce impurity phases and affect the biological results.In a previous study,a facile and novel method was utilized with ultrapure water as the unique reagent for hydrothermal treatment,and a uniform hydroxyapatite(HAp)surface layer was constructed on composite ceramics(β-TCP/CaSiO_(3))in situ.Further combined with 3D printing technology,biomimetic hierarchical structure scaffolds were fabricated with interconnected porous composite ceramic scaffolds as the architecture and micro/nano-rod hybrid HAp as the surface layer.The obtained HAp surface layer favoured cell adhesion,alleviated the cytotoxicity of precursor scaffolds,and upregulated the cellular differentiation of mBMSCs and gene expression of HUVECs in vitro.In vivo studies showed that capillary formation,bone augmentation and new bone matrix formation were upregulated after the HAp surface layer was obtained,and the results confirmed that the fabricated biomimetic hierarchical structure scaffold could be an effective candidate for bone regeneration.

Hierarchical Micropore/Nanorod Apatite Hybrids In-Situ Grown from 3-D Printed Macroporous Ti6Al4V Implants with Improved Bioactivity and Osseointegration

The advent of three-dimensional （3-D） printed technique provides great possibility in the fabrication of customized porous titanium （Ti） implant. However, the bioinert property of the printed Ti poses an out- standing problem. Hybrid micro-arc oxidation and hydrothermal （MAO-HT） treatment on porous metals is able to produce multi-scaled hierarchical orthopedic implant, showing great potential for surface mod- ification of 3-D printed implant. In this study, cylindrical porous Ti6Al4V （Ti64） scaffolds with pore size of 640 lure, porosity of ？3% were 3-D printed by electron beam melting process, and their surfaces were left untreated or treated by a combined MAO-HT procedure. In vitro bioactivity was tested by immer- sion in simulated body fluid for different time points. Then, 12 scaffolds in each group were implanted into the femoral condyles of New Zealand rabbit for 8 weeks. Osseointegration was evaluated by qual- itative and quantitative histological analysis, and the bone ingrowth features were probed by sequential fluorescent labeling at 3 and 6 weeks post-surgery, Following the MAO-HT treatment, the porous Ti64 scaffold was endowed with multi-scaled micro/nano-topographies and high amounts of CaP on its surface. The treated scaffold exhibited drastically enhanced apatite forming ability compared with the un- treated one. In vivo test revealed significantly that a higher amount of bone ingrowth and bone implant contact at the treated scaffold. The 2 types of scaffolds had different patterns of bone ingrowth; the treated scaffold exhibited a pattern of contact osteogenesis, by which bone formed directly on the treated implant surface, whereas bone formed distal to the implant surface of the untreated scaffold. MAO-HT treat- ment can significantly enhance the in vitro apatite-inducing ability and in vivo osseointegration capacity of 3-D porous Ti64 scaffold and may provide as a viable approach for the fabrication of bioactive 3-D printed porous implant for orthopedic applications.

Two-stage degradation and novel functional endothelium characteristics of a 3-D printed bioresorbable scaffold

Bioresorbable scaffolds have emerged as a new generation of vascular implants for the treatment of atherosclerosis,and designed to provide a temporary scaffold that is subsequently absorbed by blood vessels over time.Presently,there is insufficient data on the biological and mechanical responses of blood vessels accompanied by bioresorbable scaffolds(BRS)degradation.Therefore,it is necessary to investigate the inflexion point of degradation,the response of blood vessels,and the pathophysiological process of vascular,as results of such studies will be of great value for the design of next generation of BRS.In this study,abdominal aortas of SD rats were received 3-D printed poly-l-actide vascular scaffolds(PLS)for various durations up to 12 months.The response of PLS implanted aorta went through two distinct processes:(1)the neointima with desirable barrier function was obtained in 1 month,accompanied with slow degradation,inflammation,and intimal hyperplasia;(2)significant degradation occurred from 6 months,accompanied with decreasing inflammation and intimal hyperplasia,while the extracellular matrix recovered to normal vessels which indicate the positive remodeling.These in vivo results indicate that 6 months is a key turning point.This“two-stage degradation and vascular characteristics”is proposed to elucidate the long-term effects of PLS on vascular repair and demonstrated the potential of PLS in promoting endothelium function and positive remodeling,which highlights the benefits of PLS and shed some light in the future researches,such as drug combination coatings design.

Fabrication of channeled scaffolds through polyelectrolyte complex (PEC) printed sacrificial templates for tissue formation

One of the pivotal factors that limit the clinical translation of tissue engineering is the inability to create large volume and complex three-dimensional (3D) tissues, mainly due to the lack of long-range mass transport with many current scaffolds. Here we present a simple yet robust sacrificial strategy to create hierarchical and per-fusable microchannel networks within versatile scaffolds via the combination of embedded 3D printing (EB3DP), tunable polyelectrolyte complexes (PEC), and casting methods. The sacrificial templates of PEC filaments (diameter from 120 to 500 μm) with arbitrary 3D configurations were fabricated by EB3DP and then incorpo-rated into various castable matrices (e.g., hydrogels, organic solutions, meltable polymers, etc.). Rapid disso-lution of PEC templates within a 2.00 M potassium bromide aqueous solution led to the high fidelity formation of interconnected channels for free mass exchange. The efficacy of such channeled scaffolds for in vitro tissue formation was demonstrated with mouse fibroblasts, showing continuous cell proliferation and ECM deposition. Subcutaneous implantation of channeled silk fibroin (SF) scaffolds with a porosity of 76% could lead to tissue ingrowth as high as 53% in contrast to 5% for those non-channeled controls after 4 weeks. Both histological and immunofluorescence analyses demonstrated that such channeled scaffolds promoted cellularization, vasculari-zation, and host integration along with immunoregulation.

A STUDY ON TRANSIENT FLUID FLOW OF HORIZONTAL WELLS IN DUAL-PERMEABILITY MEDIA

To adopt horizontal wells in dual media reservoirs, a good understanding of the related fluid flows is necessary. Most of the recent studies focus on dual porosity media instead of dual permeability media. In this article, through both integral transformation and sink-source superposition, a new Laplace-domain solution is obtained for the slightly-compressible fluid flow in the 3-D dual-permeability media in which the horizontal well is operating in a constant rate of production. Major asymptotic characteristics of diagnosis curves of dimensionless downhole pressure are analyzed by the limited analysis. Effects of parameters of dual-permeability media including mobility ratio k, storativity ratio ω and inter-porosity flow parameter k on the downhote pressure are studied by using the Laplace numerical inversion. The new solution obtained in this article includes and improves the previous results and then can be used as a basis for either pressure transient analysis or formation behavior evaluation for the typical reservoir with horizontal wells.

Additive manufactured metallic implants for orthopaedic applications

Metallic implants are commonly used in various orthopaedic surgeries, like fracture fixation, spinal instrumentation, joint replacement and bone tumour surgery.Patients may need to adapt to the fixed dimensions of the standard implants. It may result in suboptimal fit to the host bones and possible adverse clinical results. The standard traditional implants may not address the reconstructive challenges such as severe bone deformity or bone loss after implant loosening and bone tumour resection. With the advent of digital technologies in medical imaging, computer programming in three-dimensional（3 D） modelling and computer-assisted tools in precise placement of implants, patient-specific implants（PSI） have gained more attention in complex orthopaedic reconstruction. Additive manufacturing technology, in contrast to the conventional subtractive manufacturing, is a flexible process that can fabricate anatomically conforming implants that match the patients’ anatomy and surgical requirements. Complex internal structures with porous scaffold can also be built to enhance osseointegration for better implant longevity. Although basic studies have suggested that additive manufactured（AM） metal structures are good engineered biomaterials for bone replacement, not much peer-reviewed literature is available on the clinical results of the new types of implants. The article gives an overview of the metallic materials commonly used for fabricating orthopaedic implants, describes the metal-based additive manufacturing technology and the processing chain in metallic implants; discusses the features of AM implants;reports the current status in orthopaedic surgical applications and comments on the challenges of AM implants in orthopaedic practice.