Porous Bone Research Articles

Shape memory PLLA-TMC/CSH-dPA microsphere scaffolds with mechanical and bioactive enhancement for bone tissue engineering

Porous biodegradable bone scaffold is a remarkable strategy for bone-tissue engineering. It is well known that some basic requirements such as the biodegradabilty, biocompatibility, porous structure, surface properties, mechanical properties and plasticity of the scaffolds are vital for new bone formation. In this article, we adopted a low temperature method and poly (dopamine) coating strategy to fabricate porous shape-memory poly (L-lactide-co-trimethlyene carbonate)/calcium sulfate hemihydrate-poly (dopamine) microsphere scaffolds with uniform microstructure. Compared with PLLA-TMC microspheres, PLLA-TMC/CSH and PLLA-TMC/CSH-dPA microspheres have rougher surface and increased Tg. The mechanical properties and biodegradability of scaffolds were also tested in vitro, and the biocompatibility and osteoconductivity were monitored by CCK-8 and ALP activity assay using MC3T3-E1 cells. Strikingly, compared with PLLA-TMC scaffolds, PLLA-TMC/20CSH scaffolds possessed an enhanced initial compression modulus and higher degradation rate. Meanwhile, the compression modulus of all P/CSH scaffolds matched the cancellous bone during degradation period (103.04–623.75 MPa). Moreover, the PLLA-TMC/CSH-dPA microsphere scaffolds were non-toxic and contributed to cell adhesion. In summary, the prepared PLLA-TMC/CSH-dPA microsphere scaffold in this work is a promising approach for bone-tissue engineering.

Marginal sealing around integral bilayer scaffolds for repairing osteochondral defects based on photocurable silk hydrogels

Osteochondral repair remains a major challenge in current clinical practice despite significant advances in tissue engineering. In particular, the lateral integration of neocartilage into surrounding native cartilage is a difficult and inadequately addressed problem that determines the success of tissue repair. Here, a novel design of an integral bilayer scaffold combined with a photocurable silk sealant for osteochondral repair is reported. First, we fabricated a bilayer silk scaffold with a cartilage layer resembling native cartilage in surface morphology and mechanical strength and a BMP-2-loaded porous subchondral bone layer that facilitated the osteogenic differentiation of BMSCs. Second, a TGF-β3-loaded methacrylated silk fibroin sealant (Sil-MA) exhibiting biocompatibility and good adhesive properties was developed and confirmed to promote chondrocyte migration and differentiation. Importantly, this TGF-β3-loaded Sil-MA hydrogel provided a bridge between the cartilage layer of the scaffold and the surrounding cartilage and then guided new cartilage to grow towards and replace the degraded cartilage layer from the surrounding native cartilage in the early stage of knee repair. Thus, osteochondral regeneration and superior lateral integration were achieved in vivo by using this composite. These results demonstrate that the new approach of marginal sealing around the cartilage layer of bilayer scaffolds with Sil-MA hydrogel has tremendous potential for clinical use in osteochondral regeneration.

3D printing and osteogenesis of loofah-like hydroxyapatite bone scaffolds

Repair of metabolic function in large bone defect remains a critical challenge, which largely depends on the osteogenic property of bone scaffold. Furthermore, microporous structure is one of the most critical factors that influence the osteogenic performance of bone scaffold. Therefore, it is an effective method to explore porous structures aiming at promoting osteogenesis. In this work, hydroxyapatite, the most abundant inorganic substance in bone tissue, was considered the research material. Furthermore, a natural loofah with high porosity and connectivity was selected as the bionic structure to reconstruct a porous bone scaffold based on 3D printing. Four types of loofah-like bone scaffolds were reconstructed and fabricated, and they all have an appropriate pore size and complex internal structure with a desirable porosity. According to the osteogenic ability analyses of micro-CT and histological morphometric, the BV/TV data of Type Ⅱ could reach 33%. The bone formation was found in pores and deep, rugged surfaces of scaffolds. The bionic bone scaffolds can promote in vivo osteogenesis, confirming the utility of our designed bionic scaffolds for bone regeneration.

Preparation and biological assessment of a ZrO2-based bone scaffold coated with hydroxyapatite and bioactive glass composite

Zirconia (ZrO2) bioceramics has superior stiffness, prominent fracture toughness and fracture strength. However, ZrO2 is almost bioinert material as an alternative scaffolds for repairing bone defects. In this paper, we prepared a porous ZrO2-based bone scaffold coated with hydroxyapatite (HA) and bioactive glass (BG) composite and optimized the quality hybrid proportion of HA and BGs composite coating and sintering temperature. The scaffold has a dense composite coating at the coating sintering temperature of 950 °C and HA content of 70% with Ca2SiO4 and β-TCP, HA and Ca10(PO4)6CO3 phases. The ZrO2 composite scaffold with HA-BG coating was capable of forming rich calcium and phosphorus deposits in the simulated body fluids. Its compression strength was superior to that of the porous ZrO2 scaffold. And the scaffold can promote proliferation of cultured mesenchymal stem cells and the adhesion and propagation of osteosarcoma MG-63 cells. The results exhibited that the excellent mechanical properties, biological activities and good cytocompatibility of the scaffold. Therefore, The composite scaffold represents a potential bone implant for future clinical applications.

AN AYURVEDIC APPROACH TOWARDS POSTMENOPAUSAL OSTEOPOROSIS - A REVIEW

India is the second largest country in the world regarding population. As the life expectancy has increased, the population of postmenopausal women is also increased. Hence the problems associated with increasing age are increased. The studies of last two decades suggest that women in menopausal age report more phys-iological and psychological problems. Osteoporosis is one among them. Osteoporosis or porous bone is a worldwide problem, characterized by low bone mass and structural deterioration of bone tissue, leading to bone fragility and an increased risk of fractures. In modern science treatment available for menopausal symptoms is mainly symptomatic and has some adverse effects too. In Ayurveda we cannot find the name of this disease, but signs and symptoms of Asthi- Kshaya are found quite similar to osteoporosis. The func-tion of dhatu is dharaṇa (To maintain the structure) of the body. Among all dhatus, asthidhatu is responsi-ble for maintenance of structural framework of the body. It shapes the body and protects the vital organs. Acharya Charaka in Sutra Sthan has explained the concept of osteoporosis. Aggravation of Vata is a main cause of Asthi- Kshaya and so it is mentioned as a Vata related disorder in Samhitas. Principle of treatment mentioned in Charak Samhita is as, “Samanagunabhyaso Hi Dhatunaam Vruddhi Karanam”. According to it, things, which contain similar properties to a particular Dhatu of body, can be helpful to increase that one Dhatu. So Vatashamak medicines, diet, exercise having similar properties to Asthi Dhatu, Panchakarma, Rasayana can be very effective to promote bone cells in body. This study is an attempt to understand Ni-dana panchaka of this disease, and its holistic management in context of Ayurveda. Keywords: Menopause, Rajonivrutti, Osteoporosis, Asthikshaya

Treatment of periodontal intrabony defects using bovine porous bone mineral and guided tissue regeneration with/without platelet-rich fibrin: A randomized controlled clinical trial.

To investigate the regenerative effect of adjunctive use of guided tissue regeneration (GTR), bovine porous bone mineral (BPBM), and platelet-rich fibrin (PRF) in intrabony defects. Fourteen participants were enrolled, and for each patient their left and right two sides were randomized to the test group or control group. Only the worst intrabony defect on each side was analyzed. The test group received GTR, BPBM, and PRF, whereas the control group received only GTR and BPBM. The PRF used in the trial was fluid PRF, which combined with the BPBM to form a BPBM-PRF complex. The patients were followed up by clinical and radiographic evaluation for 24 months after surgery. Probing depth (PD) in the test group was significantly less than that in the control group at 12 and 24 months after surgery, and the mean difference was ≈ 0.5 to 0.7mm. Clinical attachment level (CAL) gain in the test group was ≈ 0.9mm higher than that in the control group at 6 months after surgery, and the difference reached 1.0 to 1.1mm 12 and 24 months after surgery. None of the other clinical or radiographic parameters differed significantly between the two groups at any time-point after the surgery. Compared with GTR and BPBM, the combination of GTR and BPBM-PRF complex is more effective clinically, and results in better clinical outcomes.

Immunohistochemical characteristics of lateral bone augmentation using different biomaterials around chronic peri-implant dehiscence defects: An experimental in vivo study.

To investigate the immunohistochemical characteristics of a highly porous synthetic bone substitute and a cross-linked collagen membrane for guided bone regeneration. Three experimental groups were randomly allocated at chronic peri-implant dehiscence defect in 8 beagle dogs: (i) biphasic calcium phosphate covered by a cross-linked collagen membrane (test group), (ii) deproteinized bovine bone mineral covered by a natural collagen membrane (positive control) and (iii) no treatment (negative control). After 8 and 16weeks of submerged healing, dissected tissue blocks were processed for immunohistochemical analysis. Seven antibodies were used to detect the remaining osteogenic and angiogenic potential, and quantitative immunohistochemical analysis was done by software. The antigen reactivity of alkaline phosphatase was significantly higher in the test group compared to the positive and negative controls, and it maintained till 16weeks. The intensity of osteocalcin was significantly higher in the positive control at 8weeks than the other groups, but significantly decreased at 16weeks and no difference was found between the groups. A significant large number of TRAP-positive cells were observed in the test group mainly around the remaining particles at 16weeks. The angiogenic potential was comparable between the groups showing no difference in the expression of transglutaminase II and vascular endothelial growth factor. Guided bone regeneration combining a highly porous biphasic calcium phosphate synthetic biomaterial with a crosslinked collagen membrane, resulted in extended osteogenic potential when compared to the combination of deproteinized bovine bone mineral and a native collagen membrane.

An exploration on human compatible artificial bone placement through cell culture

The artificial bone replacement material showed significantly higher retention forces than actual bone samples. Trauma, cancer, ageing and genetic diseases, and tissue reconstruction causes bone defects and bone lesions. Providing mechanical and functional integrity is an important step for the bone regeneration. Using autogenic or allogeneic bone grafts conventionally accelerates bone regeneration with minimal autograft and allograft capital. While autogenous graft is considered the golden standard in restoring bone defects, the harvest may impact patients. The aim of this study was to elucidate the ability of a newly developed, high porosity unidirectional porous b-TCP artificial bone to induce regeneration of bones. The capacity of a commercially available b-TCP drug to cause bone regeneration was contrasted.Implantation in bony defects left after fibula harvesting for spinal fusion surgery as well. Innovative biomaterials with osteoinductive potential have emerged as candidates for bone repair since the discovery of osteoinduction in the early 20th century. Recently, models of artificial protocell have shown great potential for tissue regeneration. Hydroxyapatite (HAP) nanocrystallites of all forms of bones are characterized by their ultrathine properties, which are uniaxially aligned with fibrillar collagen to reveal the (100) faces in a special way. We speculate that living organisms prefer the specific crystal morphology and HAP's orientation due to interactions at the mineral-cell interface between cells and crystals. To investigate the ultrathine mineral modulating effect on cell bioactivity and bone generation, bone-like platy HAP (p-HAP) and two different rod-like HAPs have been synthesized here. The platy HAP with (100) faces significantly promoted cell viability and osteogenic differentiation of mesenchymal stem cells ( MSCs) as compared to rod-like HAPs with (001) faces as the dominant crystal orientation, indicating that MSCs could recognize the crystal face and prefer the (100) HAP faces.
 Mediscope Vol. 8, No. 1: January 2021, Page 7-18

Use of a novel Screen-Enrich-Combine(-biomaterials) Circulating System to fill a 3D-printed open Ti6Al4V frame with mesenchymal stem cells/β-tricalcium phosphate to repair complex anatomical bone defects in load-bearing areas.

BackgroundRepairing complex anatomical load-bearing bone defects is difficult because it requires the restoration of the load-bearing function, reconstructing the anatomical shape, and repair by regenerated bone. We previously developed a Screen–Enrich–Combine(-biomaterials) Circulating System (SECCS) for rapid intraoperative enrichment of autologous bone marrow mesenchymal stem cells (MSCs) to enhance the osteogenic ability of porous bone substitutes. In this study, we prepared a 3D-printed Ti6A14V macroporous frame matching the defect shape to provide early load-bearing support and evaluated the efficacy of filling the frame with SECCS-processed MSCs/beta tricalcium phosphate (β-TCP) for long-term bone growth.MethodsFifteen 2-year-old goats were involved in this study, and the lateral part of their distal femur was removed by an electric saw and was fitted by a matching electron beam melting technology-prepared (EBM) Ti6Al4V frame. Three types of frames, filled with nothing, pure porous β-TCP, or SECCS-processed MSCs/β-TCP, were fixed onto the defect site. Repair efficacy was evaluated by X-ray radiography, computed tomography (CT), histology, and histomorphometry.ResultsIn the basic regular hexagon printing unit, the combined side width (w) and the inscribed circle diameter (d) determines the printing frame’s mechanical strength. The compressive load was significantly higher for w=1.9 mm, d=4.4 mm than for w=1.7 mm, d=4.0 mm or w=2.0 mm, d=5.0 mm (P<0.05). The EBM-prepared Ti6Al4V defect-matched frame was well maintained 9 months after implantation. The MSCs successfully adhered to the wall of the porous β-TCP in the SECCS-processed group and had spread fully in the test samples. Each goat in the MSCs/β-TCP–the filled group, had approximately 31,321.7±22,554.7 of MSCs and a larger area of new bone growth inside the frame than the control and blank areas groups.ConclusionsFilling the 3D-printed Ti6Al4V large-aperture frame with osteogenic materials achieved biological reconstruction over a larger area of regenerated bone to repair complex anatomical weight-bearing bone defects under the condition of early frame-supported load bearing. MSCs/β-TCP prepared by SECCS can be used as a filling material for this type of bone defect to obtain more efficacious bone repair.

Porous Biphasic Calcium Phosphate for Biomedical Application

Excellent osteoconductivity and resorbability achieved when porous bioceramics have highsurface area that providing fast bone ingrowth. Porous samples were fabricated by using biphasic calcium phosphate BCP (achieved from HA heat treated at 850 oC) with 10 and 20 wt% of ovalbumin binder powder and mixture of carrot fibers and ovalbumin powders (1:1) then dried at 60oC and fired at 1300 oC. Structural, physical and mechanical properties of the prepared porous bioceramic were determined involved X-ray diffraction, Fourier transform infrared spectroscopy FTIR, apparent porosity, water absorption, apparent solid density and compressive strength. The results of X-ray and FTIR showed that the heat treatment of HA was succeeded in forming biphasic calcium phosphate. The apparent porosity values increased with increasing of the binder and carrot fibers content and the growths density of bacteria on bioceramics are less than natural bone. The effect of pathogenic bacteria (Pseudomonas &amp; Staphylococcus) that cause pollution on porous calcium phosphate and natural bone (Albino mice) has been studied.

Process parameter optimization for porosity and compressive strength of calcium sulfate based 3D printed porous bone scaffolds

Purpose This study aims to optimize the process parameters of ZPrinter® 450 for measured porosity (MP) and compressive strength (CS) of calcium sulfate-based porous bone scaffold using Taguchi approach. Design/methodology/approach Initially, a porous scaffold with smallest pore size that can be de-powdered completely is identified through a pilot study. Five printing parameters, namely, layer thickness (LT), build orientation (BO), build position (BP), delay time (DT) and binder saturation (BS), each at three levels have been optimized for MP and CS of the fabricated scaffolds using L27 orthogonal array (OA), signal-to-noise ratio and analysis of variance (ANOVA). Findings The scaffolds with 600 µm pores could be de-powdered completely. Optimum levels of parameters are LT2, BO1, BP2, DT1 and BS1 for MP and LT1, BO1, BP2, DT1 and BS2 for CS. The ANOVA reveals that the BS (49.12%) is the most and BP (8.34%) is the least significant parameter for MP. LT (50.84%) is the most, BO (33.79%) is second most and DT (2.59%) is the least significant parameter for CS. Taguchi confirmation test and linear regression models indicate a good agreement between predicted and experimental values of MP and CS. The experimental values of MP and CS at the optimum levels of parameters are found 38.12% and 1.29 MPa, respectively. Originality/value The paper presents effect of process parameters of ZPrinter® 450 on MP and CS of calcium sulfate-based porous scaffolds. Results may be used as guideline for powder bed binder jetting three-dimensional printing of ceramic scaffolds.

3D printed bone tissue regenerative PLA/HA scaffolds with comprehensive performance optimizations

Polylactic acid/Hydroxyapatite (PLA/HA) composite was widely studied and applied in the field of biomaterials for its good processability, bioactivity, and mechanical properties. In addition to traditional preparation methods, additive manufacturing has also been adopted to prepare PLA/HA composites with customized geometries. This work combined the comprehensive optimized PLLA (L-polylactic acid)/nano-HA (nHA) composite with the low-cost and stable Fused deposition modeling (FDM) technology to successfully prepare PLLA/nHA porous bone repair scaffolds. The results showed that PLLA/nHA composite ink satisfied the smoothness of printing, and the accuracy also met the requirements of personalized bone repair application. The high loaded nHA scaffold had suitable compressive strength was significantly higher than those of pure HA ceramic scaffold and cancellous bone. Besides, in vitro bone-like apatite formation on the surface in the degradation process and in vivo evaluations further verified its good osteogenic property. Compared with other complex and cutting-edge 3D printing technologies, this study provides a low-cost, stable, simple and fast way to realize personalized printing of bone repair scaffolds, which is undoubtedly conductive to the improvement and rapid deployment of personalized biomaterials in clinical applications.

Use of unidirectional and spherical porous β-tricalcium phosphate in opening-wedge high tibial osteotomy: a case series.

Introduction: Unidirectional porous β-tricalcium phosphate (UDPTCP) consists of a novel porous artificial bone that is structurally different from conventional artificial bone comprised of spherical porous β-tricalcium phosphate (SPTCP).Case presentation: We present our first four clinical cases of opening-wedge high tibial osteotomy (OWHTO) using UDPTCP and SPTCP together. The patients’ mean age was 54.5 ± 5.9 years, and the mean observation period was 20.8 ± 2.8 months. In OWHTO, two wedge shaped pieces of UDPTCP and SPTCP were cut to fit the gap and implanted parallel to each other in the anterior and posterior parts, respectively. We evaluated the correction loss and bone remodeling for UDPTCP and SPTCP over time using radiography and computed tomography, and evaluated the clinical outcomes.Conclusion: There was no correction loss reported in any case, and early bone remodeling was observed with UDPTCP. All patients achieved satisfactory clinical results with no adverse events.

Development of highly porous calcium phosphate bone cements applying nonionic surface active agents

A novel way of obtaining highly porous cements is foaming them with the use of nonionic surface active agents (surfactants). In this study, foamed calcium phosphate cements (fCPCs) intended for in situ use were fabricated by a surfactant-assisted foaming process. Three different surface active agents, Tween 20, Tween 80 and Tetronic 90R4, were used. The amount of surfactant, based on its critical micelle concentration and cytotoxicity as well as foaming method, was determined. It has been established that in order to avoid cytotoxic effects the concentration of all applied surfactants in the cement liquid phases should not exceed 1.25 g L−1. It was found that Tetronic 90R4 had the lowest cytotoxicity whereas Tween 20 had the highest. The influence of the type of surfactant used in the fabrication process of bioactive macroporous cement on the physicochemical and biological properties of fCPCs was studied. The obtained materials reached higher than 50 vol% open porosity and possessed compressive strength which corresponds to the values for cancellous bone. The highest porosity and compressive strength was found for the material with the addition of Tween 80. In vitro investigations proved the chemical stability and high bioactive potential of the examined materials.

Process Study on Surface Modification of Coral Hydroxyapatite

Objective: To explore process of modifying coral hydroxyapatite by nmZnO under different conditions, the final plan is to develop a porous artificial bone composite that combines the antibacterial properties of nano zinc oxide with the porous biodegradability of coral hydroxyapatite. Methods: Coral hydroxyapatite was modified by zinc nitrate sol-gel method at 70°C in weak acid environment. White granular porous composite materials were obtained by ultrasonic, rotary stirring, drying and calcination. The composition of the composite material is analyzed using X-ray diffractomer (XRD), using scanning electron microscopy (SEM) to observe and analyze changes in the surface appearance of composite materials, using energy dispersive X-ray spectroscopy (EDX) to observe and analyze the composition of the composite surface, the results of thermogravimetric analysis were used to study the decomposition temperature and other characteristics of the composite. Results: The sol-gel method can be used for antibacterial modification on CHA surface. When the mass ratio of coral hydroxyapatite, zinc nitrate and PEG-6000 is 48:4:5, the particle size and distribution of nano-zinc oxide particles are ideal, and uniformly distributed spherical ZnO nanoparticles can be observed under scanning electron microscopy. Conclusion: Coral hydroxyapatite surface could be modified by zinc nitrate sol-gel method. The particle size of nano zinc oxide is less than 100 nanometers. The agglomeration problem of nano-particles is solved; the porous structure of CHA are not destroyed.

Progenitor cell-derived exosomes endowed with VEGF plasmids enhance osteogenic induction and vascular remodeling in large segmental bone defects.

Large segmental bone regeneration remains a great challenge due to the lack of vascularization in newly formed bone. Conventional strategies primarily combine bone scaffolds with seed cells and growth factors to modulate osteogenesis and angiogenesis. Nevertheless, cell-based therapies have some intrinsic issues regarding immunogenicity, tumorigenesis, bioactivity and off-the-shelf transplantation. Exosomes are nano-sized (50-200 nm) extracellular vesicles with a complex composition of proteins, nucleic acids and lipids, which are attractive as therapeutic nanoparticles for disease treatment. Exosomes also have huge potential as desirable drug/gene delivery vectors in the field of regenerative medicine due to their excellent biocompatibility and efficient cellular internalization.Methods: We developed a cell-free tissue engineering system using functional exosomes in place of seed cells. Gene-activated engineered exosomes were constructed by using ATDC5-derived exosomes to encapsulate the VEGF gene. The specific exosomal anchor peptide CP05 acted as a flexible linker and effectively combined the engineered exosome nanoparticles with 3D-printed porous bone scaffolds.Results: Our findings demonstrated that engineered exosomes play dual roles as an osteogenic matrix to induce the osteogenic differentiation of mesenchymal stem cells and as a gene vector to controllably release the VEGF gene to remodel the vascular system. In vivo evaluation further verified that the engineered exosome-mediated bone scaffolds could effectively induce the bulk of vascularized bone regeneration.Conclusion: In our current work, we designed specifically engineered exosomes based on the requirements of vascularized bone repair in segmental bone defects. This work simultaneously illuminates the potential of functional exosomes in acellular tissue engineering.

Attachment and migration of cells on porous bone graft

AbstractPorous bone graft is prepared using a gel‐foaming and sintering technique. The porosity of the bone graft is 70 vol%; the size of pores is around 130 µm. The pores are interconnected through opening of around 40 µm. The interactions between preosteoblast cells and the bone graft are then investigated. Although the pores are interconnected, most the cells are attached to the surface of bone graft. Only a few cells migrate into the cross‐section within a time span of 28 days. Such observation provides key information on pore structure design of bone graft.

Three-dimensional biofabrication of an aragonite-enriched self-hardening bone graft substitute and assessment of its osteogenicity in vitro and in vivo.

ABSTRACTA self-hardening three-dimensional (3D)-porous composite bone graft consisting of 65 wt% hydroxyapatite (HA) and 35 wt% aragonite was fabricated using a 3D-Bioplotter®. New tetracalcium phosphate and dicalcium phosphate anhydrous/aragonite/gelatine paste formulae were developed to overcome the phase separation of the liquid and solid components. The mechanical properties, porosity, height and width stability of the end products were optimised through a systematic analysis of the fabrication processing parameters including printing pressure, printing speed and distance between strands. The resulting 3D-printed bone graft was confirmed to be a mixture of HA and aragonite by X-ray diffraction, Fourier transform infrared spectroscopy and energy dispersive X-ray spectroscopy. The compression strength of HA/aragonite was between 0.56 and 2.49 MPa. Cytotoxicity was assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay in vitro. The osteogenicity of HA/aragonite was evaluated in vitro by alkaline phosphatase assay using human umbilical cord matrix mesenchymal stem cells, and in vivo by juxtapositional implantation between the tibia and the anterior tibialis muscle in rats. The results showed that the scaffold was not toxic and supported osteogenic differentiation in vitro. HA/aragonite stimulated new bone formation that bridged host bone and intramuscular implants in vivo. We conclude that HA/aragonite is a biodegradable and conductive bone formation biomaterial that stimulates bone regeneration. Since this material is formed near 37°C, it will have great potential for incorporating bioactive molecules to suit personalised application; however, further study of its biodegradation and osteogenic capacity is warranted. The study was approved by the Animal Ethical Committee at Tongji Medical School, Huazhong University of Science and Technology (IACUC No. 738) on October 1, 2017.

A highly porous animal bone-derived char with a superiority of promoting nZVI for Cr(VI) sequestration in agricultural soils

Paddy soil and irrigation water are commonly contaminated with hexavalent chromium [Cr(VI)] near urban industrial areas, thereby threatening the safety of agricultural products and human health. In this study, we develop a porous and high specific area bone char (BC) to support nanoscale zero-valent iron (nZVI) and apply it to remediate Cr(VI) pollution in water and paddy soil under anaerobic conditions. The batch experiments reveal that BC/nZVI exhibits a higher removal capacity of 516.7 mg/(g•nZVI) for Cr(VI) than nZVI when normalized to the actual nZVI content, which is 2.8 times that of nZVI; moreover, the highest nZVI utilization is the nZVI loading of 15% (BC/nZVI15). The Cr(VI) removal efficiency of BC/nZVI15 decreases with increasing pH (4 – 10). Coexisting ions (phosphate and carbonate) and humic acid can inhibit the removal of Cr(VI) with BC/nZVI15. Additionally, BC exhibits a strong advantage in promoting Cr(VI) removal by nZVI compared to the widely used biochar and activated carbon. Our results demonstrate that reduction and coprecipitation are the dominant Cr(VI) removal mechanisms. Furthermore, BC/nZVI15 shows a significantly higher reduction and removal efficiency as well as a strong anti-interference ability for Cr(VI) in paddy soil, as compared to nZVI. These findings provide a new effective material for remediating Cr(VI) pollution from water and soil.

Process capability analysis of binder jetting 3D printing process for fabrication of calcium sulphate based porous bone scaffolds

ABSTRACT This study aims at investigating the process capability of a 3D printer for the fabrication of porous bone scaffolds. Initially, a suitable material is identified by optimising process parameters of a 3D printer using a full factorial design approach. Then, dimensional deviation and tolerance grades of the scaffold samples are calculated. Finally, process capability indices are evaluated and the process is recentred. Out of two materials under study, VisiJet PXL Core powder is found to provide better dimensional accuracy. Tolerance grades of the samples are found to be ranged from IT3 to IT10. Maximum dimensional deviation before and after centring the process is found to be 0.47% and 0.44%, respectively. Process capability indices Cp and Cpk are greater than 1 and close to industry benchmark (Cpk ≥1.33). This indicates the process is under statistical control and capable of fabricating porous bone scaffolds suitable for in vitro or in vivo bone tissue engineering applications.