Dynamic modelling and optimisation of carbon management strategies in gold processing

This thesis presents the development and application of a dynamic model of gold adsorption onto activated carbon in gold processing. The primary aim of the model is to investigate different carbon management strategies of the Carbon in Pulp (CIP) process. This model is based on simple film-diffusion mass transfer and the Freundlich isotherm to describe the equilibrium between the gold in solution and gold adsorbed onto carbon. A major limitation in the development of a dynamic model is the availability of accurate plant data that tracks the dynamic behaviour of the plant. This limitation is overcome by using a pilot scale CIP gold processing plant to obtain such data. All operating parameters of this pilot plant can be manipulated and controlled to a greater degree than that of a full scale plant. This enables a greater amount of operating data to be obtained and utilised. Two independent experiments were performed to build the model. A series of equilibrium tests were performed to obtain parameter values for the Freundlich isotherm, and results from an experimental run of the CIP pilot plant were used to obtain other model parameter values. The model was then verified via another independent experiment. The results show that for a given set of operating conditions, the simulated predictions were in good agreement with the CIP pilot plant experimental data. The model was then used to optimise the operations of the pilot plant. The evaluation of the plant optimisation simulations was based on an objective function developed to quantitatively compare different simulated conditions. This objective function was derived from the revenue and costs of the CIP plant. The objective function costings developed for this work were compared with published data and were found to be within the published range. This objective function can be used to evaluate the performance of any CIP plant from a small scale laboratory plant to a full scale gold plant. The model, along with its objective function, was used to investigate different carbon management strategies and to determine the most cost effective approach. A total of 17 different carbon management strategies were investigated. An additional two experimental runs were performed on the CIP pilot plant to verify the simulation model and objective function developed. Finally an application of the simulation model is discussed. The model was used to generate plant data to develop an operational classification model of the CIP process using machine learning algorithms. This application can then be used as part of an online diagnosis tool

Internal Structure Evaluation of Three-Dimensional Calcium Phosphate Bone Scaffolds: A Micro-Computed Tomographic Study

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66317/1/j.1551-2916.2006.01143.x.pd

Segmental mandibular bone reconstruction with a carbonate‐substituted hydroxyapatite‐coated modular endoprosthetic poly(ɛ‐caprolactone) scaffold in Macaca fascicularis

A bio‐degradable scaffold incorporating osteoinductive factors is one of the alternative methods for achieving the regeneration of a mandibular bone defect. The current pilot study addressed such a bone reconstruction in a non‐human primate model, Macaca fascicularis monkeys, with an engineered poly(ɛ‐caprolactone) (PCL) scaffold, provided with a carbonate‐substituted hydroxyapatite coating. The scaffolds were implanted into unilaterally created mandibular segmental defects in 24 monkeys. Three experimental groups were formed: (1) scaffolds with rhBMP‐2 ( n = 8), (2) scaffolds with autologous mixed bone marrow cells ( n = 8), and (3) empty scaffolds as a control group ( n = 8). Evaluation was based on clinical observation as well as micro‐CT, mechanical, and histological analyses. Despite a high infection rate, the overall results showed that the currently designed PCL scaffolds had insufficient load‐bearing capability, and complete bone union was not achieved after 6 months of implantation. Nevertheless, the group of PCL scaffolds loaded with rhBMP‐2 showed evidence of bone‐regenerative potential, in contrast to PCL with autologous mixed bone marrow cells and the control group. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 102B: 962–976, 2014.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/107529/1/jbmb33077.pd

Bacterial cellulose modified using recombinant proteins to improve neuronal and mesenchymal cell adhesion

A wide variety of biomaterials and bioactive molecules have been applied as scaffolds in neuronal tissue engineering. However, creating devices that enhance the regeneration of nervous system injuries is still a challenge, due the difficulty in providing an appropriate environment for cell growth and differentiation and active stimulation of nerve regeneration. In recent years, bacterial cellulose (BC) has emerged as a promising biomaterial for biomedical applications due its properties, such as high crystallinity, an ultrafine fiber network, high tensile strength and biocompatibility. The small signaling peptides found in the proteins of extracellular matrix are described in the literature as promoters of adhesion and proliferation for several cell lineages on different surfaces. In this work, the peptide IKVAV was fused to a carbohydrate-binding module (CBM3) and used to modify BC surfaces, with the goal of promoting neuronal and mesenchymal stem cell (MSC) adhesion. The recombinant proteins IKVAV-CBM3 and (19)IKVAV-CBM3 were successfully expressed in E. coli, purified through affinity chromatography and stably adsorbed to the BC membranes. The effect of these recombinant proteins, as well as RGD-CBM3, on cell adhesion was evaluated by MTS colorimetric assay. The results showed that the (19)IKVAV-CBM3 was able to significantly improve the adhesion of both neuronal and mesenchymal cells and had no effect on the other cell lineages tested. The MSC neurotrophin expression in cells grown on BC membranes modified with the recombinant proteins was also analyzed.Renata A. N. Pertile gratefully acknowledges support by the Programme Al beta an, the European Union Programme of High Level Scholarships for Latin America (Scholarship No. E07D401931BR). The author Susana Moreira is recipient of a SFRH/BPD/64726/2009 fellowship from Fundacao para a Ciencia e a Tecnologia (FCT, Portugal). Fabia K. Andrade is the recipient of a fellowship from Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES, Brazil)

Alginate-nanohydroxyapatite hydrogel system: Optimizing the formulation for enhanced bone regeneration

Ceramic/polymer-based biocomposites have emerged as potential biomaterials to fill, replace, repair or regenerate injured or diseased bone, due to their outstanding features in terms of biocompatibility, bioactivity, injectability, and biodegradability. However, these properties can be dependent on the amount of ceramic component present in the polymer-based composite. Therefore, in the present study, the influence of nanohydroxyapatite content (30 to 70 wt%) on alginate-based hydrogels was studied in order to evaluate the best formulation for maximizing bone tissue regeneration. The composite system was characterized in terms of physic-chemical properties and biological response, with in vitro cytocompatibility assessment with human osteoblastic cells and ex vivo functional evaluation in embryonic chick segmental bone defects. The main morphological characteristics of the alginate network were not affected by the addition of nanohydroxyapatite. However, physic-chemical features, like water-swelling rate, stability at extreme pH values, apatite formation, and Ca2+ release were nanoHA dose-dependent. Within in vitro cytocompatibility assays it was observed that hydrogels with nanoHA 30% content enhanced osteoblastic cells proliferation and expression of osteogenic transcription factors, while those with higher concentrations (50 and 70%) decreased the osteogenic cell response. Ex vivo data underlined the in vitro findings, revealing an enhanced collagenous deposition, trabecular bone formation and matrix mineralization with Alg-nanoHA30 composition, while compositions with higher nanoHA content induced a diminished bone tissue response. The outcomes of this study indicate that nanohydroxyapatite concentration plays a major role in physic-chemical properties and biological response of the composite system and the optimization of the components ratio must be met to maximize bone tissue regeneration.This work was financed by FEDER – Fundo Europeu de Desenvolvimento Regional funds through the COMPETE 2020 – Operacional Programme for Competitiveness and Internationalisation (POCI), Portugal 2020, by Portuguese funds through FCT/MCTES in the framework of the project “institute for Research and Innovation in Health Sciences” (POCI-01-0145-FEDER-007274), by Project Biotherapies (NORTE-01-0145-FEDER-000012) and by Joana Barrosʼ PhD grant (SFRH/BD/102148/2014). The authors would also like to acknowledge Rui Rocha (CEMUP), Rui Fernandes (HEMS), Rossana Correia (HEMS) and Liliana Grenho (FMDUP).info:eu-repo/semantics/publishedVersio

Calcium phosphate scaffolds for bone tissue engineering and self -association PEG-PLLA diblock copolymer for controlled drug delivery system.

In scaffold-based bone tissue engineering, the existing three-dimensional scaffolds have proved less than ideal for actual applications, not only because they lack mechanical strength, but also because they do not guarantee interconnected channels. In this work, complex three-dimensional porous dicalcium phosphate dihydrate cement (DCPD) scaffolds with control interconnected pores were successfully manufactured by combining a computationally designed using an image-based approach and a fabrication technique by indirect solid freeform fabrication (ISFF) or 'lost mold' method via casting. The scaffold fabrication can be done at physiological temperatures; the macroporosity and interconnected pore network are incorporated while the microporosity is maintained. Therefore, it is possible for any biological factor such as growth factor or bone cell to be added during scaffold manufacturing. Calcium phosphate cement is a bioceramic with potential applications for bone-tissue engineering because of its excellent biocompatibility and bone-replacement behavior over long periods. Cement must be cast in complex molds to achieve specific design of macropores with chosen size and connectivity. Unlike the fluid ceramic slurries, the DCPD cement was a more viscous paste before setting. The thorough characterization of cement slip is investigated and optimized. The complex calcium phosphate cement scaffolds (macroporosity between 33%--70%) were thoroughly examined using a non-destructive micro-computed tomography. The effects of void variance and fabrication defects on mechanical properties of the scaffolds were evaluated and compared. Image-based finite element analysis was applied to predict the mechanical behavior of the designed and the fabricated scaffolds. The latter was subsequently mechanically tested. The computational prediction of effective stiffness constants and stress distribution of the scaffolds correlated well with the experiments and showed that the calcium phosphate cement scaffolds have mechanical properties that lie within the range of human trabecular bone. By employing an ex vivo gene therapy, scaffolds were then implanted subcutaneously to demonstrate tissue in-growth. The implanted scaffolds were evaluated histologically, mechanically, and using micro-computed tomography. The implant was found to be surrounded by a large amount of bone as well as within the scaffold pores at the four weeks time point. Almost the entire implant was enveloped by new bone after eight weeks of implantation. These techniques allow us to investigate the bone formation and the scaffold degradation both qualitatively and quantitatively. These results show that by integrating the computationally designed, biodegradable osteoconductive DCPD matrix, and ex vivo gene therapy, have potential for engineering of biomimetic scaffolds and scaffolds for complex biomechanical applications.Ph.D.Applied SciencesBiomedical engineeringMaterials scienceUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/125671/2/3208474.pd

Self-aggregation and thermo-responsive properties of biodegradable poly(ethylene glycol)-poly(L-lactide) amphiphilic diblock copolymers

Transactions - 7th World Biomaterials Congress1034

Screening for 3D Environments That Support Human Mesenchymal Stem Cell Viability Using Hydrogel Arrays

In this study we generated 3D poly(ethylene glycol) (PEG) hydrogel arrays to screen for the individual and combinatorial effects of extracellular matrix (ECM) degradability, cell adhesion ligand type, and cell adhesion ligand density on human mesenchymal stem cell (hMSC) viability. In particular, we explored the influence of two well-characterized ECM-derived cell adhesion ligands: the fibronectin-derived Arg-Gly-Asp-Ser-Pro (RGDSP) sequence, and the laminin-derived Ile-Lys-Val-Ala-Val (IKVAV) sequence. PEG network degradation, the RGDSP ligand, and the IKVAV ligand each individually increased hMSC viability in a dose-dependent manner. The RGDSP ligand also improved hMSC viability in a dose-dependent manner in degradable PEG hydrogels, while the effect of IKVAV was less pronounced in degradable hydrogels. Combinations of RGDSP and IKVAV promoted high viability of hMSCs in nondegradable PEG networks, while the combined effects of the ligands were not significant in degradable PEG hydrogels. Although hMSC spreading was not commonly observed within PEG hydrogels, we qualitatively observed hMSC spreading after 5 days only in degradable PEG hydrogels prepared with 2.5 mM of both RGDSP and IKVAV. These results suggest that the enhanced throughput approach described herein can be used to rapidly study the influence of a broad range of ECM parameters, as well as their combinations, on stem cell behavior

Self-association and micelle formation of biodegradable poly(ethylene glycol)-poly(L-lactic acid) amphiphilic di-block co-polymers

10.1163/156856206777656553Journal of Biomaterials Science, Polymer Edition177747-763JBSE

Subcutaneous tissue response to titanium, poly(epsilon-caprolactone), and carbonate-substituted hydroxyapatite-coated poly(epsilon-caprolactone) plates: a rabbit study

Contains fulltext : 119196.pdf (Publisher’s version ) (Closed access)The aim of this study was to evaluate the soft tissue response to poly(epsilon-caprolactone) (PCL) implants with and without carbonate-substituted hydroxyapatite (CHA) coating compared to the commonly used titanium alloy (Ti-6Al-4V)-machined surface. Experimental materials were implanted subcutaneously in New Zealand white rabbits for 5 weeks. The tissue attachment strength, as evaluated by a tissue peel test, histological and histomorphology analysis, as well as scanning electron microscopy were compared between groups. The peel test result revealed no statistically significant difference between groups. Histological analysis found fibrous capsule formation around all implant materials. The fibrous capsule around PCL implants with and without CHA coating was significantly thinner compared with the capsule thickness around the titanium implants. However, the inflammatory cells, as present at the fibrous capsule-implant interface, were found to be significantly lower in the Ti-group. In conclusion, the current data do not prove that PCL or PCL with a CHA coating results in a superior soft tissue response compared with a machined titanium implant