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Processes, Volume 2, Issue 3 (September 2014), Pages 526-693

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Research

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Open AccessArticle A Novel Seeding and Conditioning Bioreactor for Vascular Tissue Engineering
Processes 2014, 2(3), 526-547; doi:10.3390/pr2030526
Received: 10 February 2014 / Revised: 21 May 2014 / Accepted: 20 June 2014 / Published: 8 July 2014
Cited by 1 | PDF Full-text (11168 KB) | HTML Full-text | XML Full-text
Abstract
Multiple efforts have been made to develop small-diameter tissue engineered vascular grafts using a great variety of bioreactor systems at different steps of processing. Nevertheless, there is still an extensive need for a compact all-in-one system providing multiple and simultaneous processing. The [...] Read more.
Multiple efforts have been made to develop small-diameter tissue engineered vascular grafts using a great variety of bioreactor systems at different steps of processing. Nevertheless, there is still an extensive need for a compact all-in-one system providing multiple and simultaneous processing. The aim of this project was to develop a new device to fulfill the major requirements of an ideal system that allows simultaneous seeding, conditioning, and perfusion. The newly developed system can be actuated in a common incubator and consists of six components: a rotating cylinder, a pump, a pulse generator, a control unit, a mixer, and a reservoir. Components that are in direct contact with cell media, cells, and/or tissue allow sterile processing. Proof-of-concept experiments were performed with polyurethane tubes and collagen tubes. The scaffolds were seeded with fibroblasts and endothelial cells that were isolated from human saphenous vein segments. Scanning electron microscopy and immunohistochemistry showed better seeding success of polyurethane scaffolds in comparison to collagen. Conditioning of polyurethane tubes with 100 dyn/cm2 resulted in cell detachments, whereas a moderate conditioning program with stepwise increase of shear stress from 10 to 40 dyn/cm2 induced a stable and confluent cell layer. The new bioreactor is a powerful tool for quick and easy testing of various scaffold materials for the development of tissue engineered vascular grafts. The combination of this bioreactor with native tissue allows testing of medical devices and medicinal substances under physiological conditions that is a good step towards reduction of animal testing. In the long run, the bioreactor could turn out to produce tissue engineered vascular grafts for human applications “at the bedside”. Full article
(This article belongs to the Special Issue Design of Bioreactor Systems for Tissue Engineering)
Open AccessArticle Mathematical Modeling and Analysis of Crosstalk between MAPK Pathway and Smad-Dependent TGF-β Signal Transduction
Processes 2014, 2(3), 570-595; doi:10.3390/pr2030570
Received: 6 June 2014 / Revised: 15 July 2014 / Accepted: 21 July 2014 / Published: 4 August 2014
Cited by 1 | PDF Full-text (1251 KB) | HTML Full-text | XML Full-text
Abstract
Broad evidence exists for cross talk between the Mitogen-activated protein kinases (MAPK) pathway and Smad-dependent TGF-β signal transduction. A variety of studies, oftentimes involving different cell types, have identified several potential mechanisms for the crosstalk. However, there is no clear consensus on [...] Read more.
Broad evidence exists for cross talk between the Mitogen-activated protein kinases (MAPK) pathway and Smad-dependent TGF-β signal transduction. A variety of studies, oftentimes involving different cell types, have identified several potential mechanisms for the crosstalk. However, there is no clear consensus on the actual mechanism(s) responsible for the crosstalk. This work develops a model of the pathway, including several hypothesized crosstalk mechanisms, and discusses which of the potential mechanisms can appropriately describe observed behaviors. Simulation results show a good agreement of the findings with results reported in the literature. Full article
Open AccessArticle Light-Induced Production of An Antibody Fragment and Malaria Vaccine Antigen from Chlamydomonas reinhardtii
Processes 2014, 2(3), 625-638; doi:10.3390/pr2030625
Received: 31 May 2014 / Revised: 19 July 2014 / Accepted: 21 July 2014 / Published: 7 August 2014
Cited by 1 | PDF Full-text (683 KB) | HTML Full-text | XML Full-text
Abstract
The eukaryotic green alga, Chlamydomonas reinhardtii, is a unique expression platform that can efficiently express complex therapeutic proteins. However, demonstrating that therapeutic molecules can be produced in quantifiable levels is essential to establish the potential of the C. reinhardtii expression system. [...] Read more.
The eukaryotic green alga, Chlamydomonas reinhardtii, is a unique expression platform that can efficiently express complex therapeutic proteins. However, demonstrating that therapeutic molecules can be produced in quantifiable levels is essential to establish the potential of the C. reinhardtii expression system. Thus, the objective of this investigation was to determine the process conditions that could maximize C. reinhardtii biomass accumulation and induced-production of the two recombinant proteins, a single chain fragment antibody molecule (αCD22 scFv) and malaria vaccine antigen (Pfs25), produced in the chloroplast of C. reinhardtii. To achieve a higher production of recombinant proteins, cultivation variables of C. reinhardtii, such as mixing, light-induction time and intensity, nutrient depletion and culture age, were investigated and optimized. The optimal light-induction time was 24 h at a light intensity of 300 μmol m−2 s−1. Replacement of the culture media in the late exponential growth with fresh media was beneficial to the accumulation of recombinant proteins. Optimization led to increases in the accumulation of recombinant proteins by six-fold and the recombinant protein fraction in the extracted soluble protein by two-fold. Full article
(This article belongs to the Special Issue Advances in Bioseparation Engineering)
Open AccessArticle Analysis of Gene Expression Signatures for Osteogenic 3D Perfusion-Bioreactor Cell Cultures Based on a Multifactorial DoE Approach
Processes 2014, 2(3), 639-657; doi:10.3390/pr2030639
Received: 14 February 2014 / Revised: 9 May 2014 / Accepted: 9 July 2014 / Published: 8 August 2014
Cited by 1 | PDF Full-text (1240 KB) | HTML Full-text | XML Full-text
Abstract
The use of multifactorial design of experiments (DoE) in tissue engineering bioprocess development will contribute to the robust manufacturing of tissue engineered constructs by linking their quality characteristics to bioprocess operating parameters. In this work, perfusion bioreactors were used for the in [...] Read more.
The use of multifactorial design of experiments (DoE) in tissue engineering bioprocess development will contribute to the robust manufacturing of tissue engineered constructs by linking their quality characteristics to bioprocess operating parameters. In this work, perfusion bioreactors were used for the in vitro culture and osteogenic differentiation of human periosteum-derived cells (hPDCs) seeded on three-dimensional titanium (Ti) alloy scaffolds. A CaP-supplemented medium was used to induce differentiation of the cultured hPDCs. A two-level, three-factor fractional factorial design was employed to evaluate a range of bioreactor operating conditions by changing the levels of the following parameters: flow rate (0.5–2 mL/min), cell culture duration (7–21 days) and cell seeding density (1.5 × 103–3 × 103 cells/cm2). This approach allowed for evaluating the individual impact of the aforementioned process parameters upon a range of genes that are related to the osteogenic lineage, such as collagen type I, alkaline phosphatase, osterix, osteopontin and osteocalcin. Furthermore, by overlaying gene-specific response surfaces, an integrated operating process space was highlighted within which predetermined values of the six genes of interest (i.e., gene signature) could be minimally met over the course of the bioreactor culture time. Full article
(This article belongs to the Special Issue Design of Bioreactor Systems for Tissue Engineering)
Open AccessArticle A Novel Through-Thickness Perfusion Bioreactor for the Generation of Scaffold-Free Tissue Engineered Cartilage
Processes 2014, 2(3), 658-674; doi:10.3390/pr2030658
Received: 16 February 2014 / Revised: 2 May 2014 / Accepted: 30 July 2014 / Published: 13 August 2014
Cited by 4 | PDF Full-text (2598 KB) | HTML Full-text | XML Full-text
Abstract
The objective of this study was to characterize our designed through-thickness perfusion bioreactor which could generate large scaffold-free tissue engineered cartilage constructs. The hypothesis being that through-thickness perfusion could accelerate maturation of scaffold-free tissue engineered cartilage, grown in transwell culture inserts large [...] Read more.
The objective of this study was to characterize our designed through-thickness perfusion bioreactor which could generate large scaffold-free tissue engineered cartilage constructs. The hypothesis being that through-thickness perfusion could accelerate maturation of scaffold-free tissue engineered cartilage, grown in transwell culture inserts large enough to repair typical size chondral lesions in the human knee. Internal cell culture media temperature and pH were examined over time, upon implementation of the bioreactor perfusion system inside a CO2 incubator, to ensure adequate regulation conducive to cell viability. Results indicate that temperature and pH both equilibrate within approximately 3 h. The bioreactor was tested for its efficacy to support formation of 4.5 cm2 constructs by porcine neonatal chondrocytes. Tests were conducted under three conditions: immediate perfusion with flow from bottom to top, immediate perfusion with media flow from top to bottom, and bottom to top perfusion after four weeks of static culture, giving the cells time to self-aggregate into a consolidated construct prior to perfusion. The best cell culture results were obtained when perfusion was delayed for four weeks relative to the immediate perfusion of the other methods, and this should be further investigated. Full article
(This article belongs to the Special Issue Design of Bioreactor Systems for Tissue Engineering)
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Open AccessArticle An MINLP Model that Includes the Effect of Temperature and Composition on Property Balances for Mass Integration Networks
Processes 2014, 2(3), 675-693; doi:10.3390/pr2030675
Received: 29 May 2014 / Revised: 14 July 2014 / Accepted: 30 July 2014 / Published: 18 August 2014
PDF Full-text (15006 KB) | HTML Full-text | XML Full-text
Abstract
The synthesis of water networks based on properties has commonly ignored the effect of temperature on the property balances that are part of the formulation. When wide differences of temperatures are observed within the process, such an effect might yield significant errors [...] Read more.
The synthesis of water networks based on properties has commonly ignored the effect of temperature on the property balances that are part of the formulation. When wide differences of temperatures are observed within the process, such an effect might yield significant errors in the application of conventional property balances. In this work, a framework for the development of water networks that include temperature effects on property balances is presented. The approach is based on the inclusion of constants in the property operators that are commonly used to carry out the property balances. An additional term to take care of composition effects is also included. The resulting approach is embedded into a formulation based on a mixed-integer nonlinear programming model for the design of water networks. A case study is presented that shows that the proposed approach yields an improvement in the prediction of the resulting properties for the integrated network, thus affecting the optimal solution. Full article

Review

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Open AccessReview Design Criteria for Generating Physiologically Relevant In Vitro Models in Bioreactors
Processes 2014, 2(3), 548-569; doi:10.3390/pr2030548
Received: 21 May 2014 / Revised: 17 June 2014 / Accepted: 2 July 2014 / Published: 25 July 2014
Cited by 5 | PDF Full-text (4367 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we discuss the basic design requirements for the development of physiologically meaningful in vitro systems comprising cells, scaffolds and bioreactors, through a bottom up approach. Very simple micro- and milli-fluidic geometries are first used to illustrate the concepts, followed [...] Read more.
In this paper, we discuss the basic design requirements for the development of physiologically meaningful in vitro systems comprising cells, scaffolds and bioreactors, through a bottom up approach. Very simple micro- and milli-fluidic geometries are first used to illustrate the concepts, followed by a real device case-study. At each step, the fluidic and mass transport parameters in biological tissue design are considered, starting from basic questions such as the minimum number of cells and cell density required to represent a physiological system and the conditions necessary to ensure an adequate nutrient supply to tissues. At the next level, we consider the use of three-dimensional scaffolds, which are employed both for regenerative medicine applications and for the study of cells in environments which better recapitulate the physiological milieu. Here, the driving need is the rate of oxygen supply which must be maintained at an appropriate level to ensure cell viability throughout the thickness of a scaffold. Scaffold and bioreactor design are both critical in defining the oxygen profile in a cell construct and are considered together. We also discuss the oxygen-shear stress trade-off by considering the levels of mechanical stress required for hepatocytes, which are the limiting cell type in a multi-organ model. Similar considerations are also made for glucose consumption in cell constructs. Finally, the allometric approach for generating multi-tissue systemic models using bioreactors is described. Full article
(This article belongs to the Special Issue Design of Bioreactor Systems for Tissue Engineering)
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Open AccessReview The Impact of Harvesting, Storage and Processing Factors on Health-Promoting Phytochemicals in Berries and Fruits
Processes 2014, 2(3), 596-624; doi:10.3390/pr2030596
Received: 16 April 2014 / Revised: 14 July 2014 / Accepted: 22 July 2014 / Published: 5 August 2014
Cited by 4 | PDF Full-text (630 KB) | HTML Full-text | XML Full-text
Abstract
Increasing epidemiological and experimental data now emphasize that a diet rich in vegetables and fruits confers many health benefits. Functional products containing elevated levels of bioactive compounds are attracting considerable attention due to their potential to lower the risk of chronic diseases [...] Read more.
Increasing epidemiological and experimental data now emphasize that a diet rich in vegetables and fruits confers many health benefits. Functional products containing elevated levels of bioactive compounds are attracting considerable attention due to their potential to lower the risk of chronic diseases and their associated huge healthcare costs. On a global scale, there is an increasing demand for berries and fruits, since they are natural polyphenol-rich raw material to be incorporated into functional foods, nutraceuticals and pharmaceuticals. This is a major challenge for both industry and horticultural experts, because the content of health-promoting compounds in plants varies widely not only in different plant species, but also between cultivars. The content is also significantly affected by harvesting, storage and processing factors. This review summarizes the recent data and clarifies the main contributors of harvesting time, various storage conditions and post-harvest procedures, such as temperature management, controlled atmosphere, 1-MCP, calcium and plant activators, as ways to influence health-promoting compounds in fruits. Furthermore, the ways processing factors, e.g., enzymatic treatment, pressing, clarification, temperature, pressure and fermentation, can influence the levels of polyphenols and vitamins in berries and soft fruits will be discussed. Finally, strategies for preventing the decline of health-promoting compounds in fruits during long-term storage will be assessed in light of recent scientific progress and modern methods, which preserve the levels of polyphenols, will be highlighted. Full article

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