Next Issue
Previous Issue

Table of Contents

Processes, Volume 2, Issue 2 (June 2014), Pages 333-525

  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Readerexternal link to open them.
View options order results:
result details:
Displaying articles 1-9
Export citation of selected articles as:

Research

Jump to: Review

Open AccessArticle Design and Validation of a Cyclic Strain Bioreactor to Condition Spatially-Selective Scaffolds in Dual Strain Regimes
Processes 2014, 2(2), 345-360; doi:10.3390/pr2020345
Received: 22 November 2013 / Revised: 31 January 2014 / Accepted: 21 February 2014 / Published: 31 March 2014
Cited by 1 | PDF Full-text (777 KB) | HTML Full-text | XML Full-text
Abstract
The objective of this study was to design and validate a unique bioreactor design for applying spatially selective, linear, cyclic strain to degradable and non-degradable polymeric fabric scaffolds. This system uses a novel three-clamp design to apply cyclic strain via a computer controlled
[...] Read more.
The objective of this study was to design and validate a unique bioreactor design for applying spatially selective, linear, cyclic strain to degradable and non-degradable polymeric fabric scaffolds. This system uses a novel three-clamp design to apply cyclic strain via a computer controlled linear actuator to a specified zone of a scaffold while isolating the remainder of the scaffold from strain. Image analysis of polyethylene terephthalate (PET) woven scaffolds subjected to a 3% mechanical stretch demonstrated that the stretched portion of the scaffold experienced 2.97% ± 0.13% strain (mean ± standard deviation) while the unstretched portion experienced 0.02% ± 0.18% strain. NIH-3T3 fibroblast cells were cultured on the PET scaffolds and half of each scaffold was stretched 5% at 0.5 Hz for one hour per day for 14 days in the bioreactor. Cells were checked for viability and proliferation at the end of the 14 day period and levels of glycosaminoglycan (GAG) and collagen (hydroxyproline) were measured as indicators of extracellular matrix production. Scaffolds in the bioreactor showed a seven-fold increase in cell number over scaffolds cultured statically in tissue culture plastic petri dishes (control). Bioreactor scaffolds showed a lower concentration of GAG deposition per cell as compared to the control scaffolds largely due to the great increase in cell number. A 75% increase in hydroxyproline concentration per cell was seen in the bioreactor stretched scaffolds as compared to the control scaffolds. Surprisingly, little differences were experienced between the stretched and unstretched portions of the scaffolds for this study. This was largely attributed to the conditioned and shared media effect. Results indicate that the bioreactor system is capable of applying spatially-selective, linear, cyclic strain to cells growing on polymeric fabric scaffolds and evaluating the cellular and matrix responses to the applied strains. Full article
(This article belongs to the Special Issue Design of Bioreactor Systems for Tissue Engineering)
Open AccessArticle A Novel Cell Seeding Chamber for Tissue Engineering and Regenerative Medicine
Processes 2014, 2(2), 361-370; doi:10.3390/pr2020361
Received: 14 February 2014 / Revised: 11 April 2014 / Accepted: 18 April 2014 / Published: 30 April 2014
Cited by 1 | PDF Full-text (605 KB) | HTML Full-text | XML Full-text
Abstract
There is an increasing demand for bone graft substitutes that are used as osteoconductive scaffolds in the treatment of bone defects and fractures. Achieving optimal bone regeneration requires initial cell seeding of the scaffolds prior to implantation. In order to achieve an efficient
[...] Read more.
There is an increasing demand for bone graft substitutes that are used as osteoconductive scaffolds in the treatment of bone defects and fractures. Achieving optimal bone regeneration requires initial cell seeding of the scaffolds prior to implantation. In order to achieve an efficient seeding of the scaffolds, a novel cell seeding chamber was developed. The cell seeding chamber is a closed assembly that works like an hourglass. The position of the scaffold is between two reservoirs containing the cell suspension (e.g., blood or autologous bone marrow). The cell suspension at the upper reservoir flows through the scaffold by gravitational force. The cell suspension is collected at the lower reservoir. When the upper reservoir is empty the whole assembly is turned and the process starts again. In this study, a new compact cell seeding chamber for initial cell seeding has been developed that can be used in situ. The basic functionality of the cell seeding chamber was demonstrated with a blood substitute. Full article
(This article belongs to the Special Issue Design of Bioreactor Systems for Tissue Engineering)
Open AccessArticle Stability Analysis of Reactive Multiphase Slug Flows in Microchannels
Processes 2014, 2(2), 371-391; doi:10.3390/pr2020371
Received: 5 December 2013 / Revised: 21 March 2014 / Accepted: 22 April 2014 / Published: 6 May 2014
Cited by 2 | PDF Full-text (1328 KB) | HTML Full-text | XML Full-text
Abstract
Conducting multiphase reactions in micro-reactors is a promising strategy for intensifying chemical and biochemical processes. A major unresolved challenge is to exploit the considerable benefits offered by micro-scale operation for industrial scale throughputs by numbering-up whilst retaining the underlying advantageous flow characteristics of
[...] Read more.
Conducting multiphase reactions in micro-reactors is a promising strategy for intensifying chemical and biochemical processes. A major unresolved challenge is to exploit the considerable benefits offered by micro-scale operation for industrial scale throughputs by numbering-up whilst retaining the underlying advantageous flow characteristics of the single channel system in multiple parallel channels. Fabrication and installation tolerances in the individual micro-channels result in different pressure losses and, thus, a fluid maldistribution. In this work, an additional source of maldistribution, namely the flow multiplicities, which can arise in a multiphase reactive or extractive flow in otherwise identical micro-channels, was investigated. A detailed experimental and theoretical analysis of the flow stability with and without reaction for both gas-liquid and liquid-liquid slug flow has been developed. The model has been validated using the extraction of acetic acid from n-heptane with the ionic liquid 1-Ethyl-3-methylimidazolium ethyl sulfate. The results clearly demonstrate that the coupling between flow structure, the extent of reaction/extraction and pressure drop can result in multiple operating states, thus, necessitating an active measurement and control concept to ensure uniform behavior and optimal performance. Full article
Open AccessArticle A Hybrid MPC-PID Control System Design for the Continuous Purification and Processing of Active Pharmaceutical Ingredients
Processes 2014, 2(2), 392-418; doi:10.3390/pr2020392
Received: 19 March 2014 / Revised: 15 April 2014 / Accepted: 18 April 2014 / Published: 23 May 2014
Cited by 1 | PDF Full-text (765 KB) | HTML Full-text | XML Full-text
Abstract
In this work, a hybrid MPC (model predictive control)-PID (proportional-integral-derivative) control system has been designed for the continuous purification and processing framework of active pharmaceutical ingredients (APIs). The specific unit operations associated with the purification and processing of API have been developed from
[...] Read more.
In this work, a hybrid MPC (model predictive control)-PID (proportional-integral-derivative) control system has been designed for the continuous purification and processing framework of active pharmaceutical ingredients (APIs). The specific unit operations associated with the purification and processing of API have been developed from first-principles and connected in a continuous framework in the form of a flowsheet model. These integrated unit operations are highly interactive along with the presence of process delays. Therefore, a hybrid MPC-PID is a promising alternative to achieve the desired control loop performance as mandated by the regulatory authorities. The integrated flowsheet model has been simulated in gPROMSTM (Process System Enterprise, London, UK). This flowsheet model has been linearized in order to design the control scheme. The ability to track the set point and reject disturbances has been evaluated. A comparative study between the performance of the hybrid MPC-PID and a PID-only control scheme has been presented. The results show that an enhanced control loop performance can be obtained under the hybrid control scheme and demonstrate that such a scheme has high potential in improving the efficiency of pharmaceutical manufacturing operations. Full article

Review

Jump to: Research

Open AccessReview Evaluation of Diffusive Transport and Cellular Uptake of Nutrients in Tissue Engineered Constructs Using a Hybrid Discrete Mathematical Model
Processes 2014, 2(2), 333-344; doi:10.3390/pr2020333
Received: 10 December 2013 / Revised: 20 February 2014 / Accepted: 28 February 2014 / Published: 28 March 2014
Cited by 1 | PDF Full-text (849 KB) | HTML Full-text | XML Full-text
Abstract
Tissue engineering systems for orthopedic tissues, such as articular cartilage, are often based on the use of biomaterial scaffolds that are seeded with cells and supplied with nutrients or growth factors. In such systems, relationships between the functional outcomes of the engineered tissue
[...] Read more.
Tissue engineering systems for orthopedic tissues, such as articular cartilage, are often based on the use of biomaterial scaffolds that are seeded with cells and supplied with nutrients or growth factors. In such systems, relationships between the functional outcomes of the engineered tissue construct and aspects of the initial system design are not well known, suggesting the use of mathematical models as an additional tool for optimal system design. This study develops a reaction-diffusion model that quantitatively describes the competing effects of nutrient diffusion and the cellular uptake of nutrients in a closed bioreactor system consisting of a cell-seeded scaffold adjacent to a nutrient-rich bath. An off-lattice hybrid discrete modeling framework is employed in which the diffusion equation incorporates a loss term that accounts for absorption due to nutrient uptake by cells that are modeled individually. Numerical solutions are developed based on a discontinuous Galerkin finite element method with high order quadrature to accurately resolve fine-scale cellular effects. The resulting model is applied to demonstrate that the ability of cells to absorb nutrients over time is highly dependent on both the normal distance to the nutrient bath, as well as the nutrient uptake rate for individual cells. Full article
(This article belongs to the Special Issue Design of Bioreactor Systems for Tissue Engineering)
Open AccessReview New Biosorbent Materials: Selectivity and Bioengineering Insights
Processes 2014, 2(2), 419-440; doi:10.3390/pr2020419
Received: 12 February 2014 / Revised: 18 April 2014 / Accepted: 12 May 2014 / Published: 27 May 2014
Cited by 6 | PDF Full-text (1133 KB) | HTML Full-text | XML Full-text
Abstract
Many researchers have studied the biosorption of different pollutants. However, a quite limited number of works focus on selectivity, which may be characterized as specific property for each biosorbent. Two main criteria need to be adopted for the selection and synthesis of modern
[...] Read more.
Many researchers have studied the biosorption of different pollutants. However, a quite limited number of works focus on selectivity, which may be characterized as specific property for each biosorbent. Two main criteria need to be adopted for the selection and synthesis of modern biosorbents, such as their rebinding capacity and selectivity for only one target, molecule, ion, etc. Selective biosorption could be achieved using in synthesis an innovative technique termed molecular imprinting; the idea applied through specific polymers (Molecular Imprinted Polymers (MIPs)) was used in many fields, mainly analytical. In the present work, also isotherm and kinetic models were reviewed highlighting some crucial parameters, which possibly affect selectivity. A critical analysis of the biosorption insights for biosorbents, mostly selective, describes their characteristics, advantages and limitations, and discusses various bioengineering mechanisms involved. Full article
(This article belongs to the Special Issue Advances in Bioseparation Engineering)
Open AccessReview Microreactor-Assisted Solution Deposition for Compound Semiconductor Thin Films
Processes 2014, 2(2), 441-465; doi:10.3390/pr2020441
Received: 7 January 2014 / Revised: 4 May 2014 / Accepted: 6 May 2014 / Published: 27 May 2014
Cited by 2 | PDF Full-text (4357 KB) | HTML Full-text | XML Full-text
Abstract
State-of-the-art techniques for the fabrication of compound semiconductors are mostly vacuum-based physical vapor or chemical vapor deposition processes. These vacuum-based techniques typically operate at high temperatures and normally require higher capital costs. Solution-based techniques offer opportunities to fabricate compound semiconductors at lower temperatures
[...] Read more.
State-of-the-art techniques for the fabrication of compound semiconductors are mostly vacuum-based physical vapor or chemical vapor deposition processes. These vacuum-based techniques typically operate at high temperatures and normally require higher capital costs. Solution-based techniques offer opportunities to fabricate compound semiconductors at lower temperatures and lower capital costs. Among many solution-based deposition processes, chemical bath deposition is an attractive technique for depositing semiconductor films, owing to its low temperature, low cost and large area deposition capability. Chemical bath deposition processes are mainly performed using batch reactors, where all reactants are fed into the reactor simultaneously and products are removed after the processing is finished. Consequently, reaction selectivity is difficult, which can lead to unwanted secondary reactions. Microreactor-assisted solution deposition processes can overcome this limitation by producing short-life molecular intermediates used for heterogeneous thin film synthesis and quenching the reaction prior to homogeneous reactions. In this paper, we present progress in the synthesis and deposition of semiconductor thin films with a focus on CdS using microreactor-assisted solution deposition and provide an overview of its prospect for scale-up. Full article
Open AccessReview Microreactors for Gold Nanoparticles Synthesis: From Faraday to Flow
Processes 2014, 2(2), 466-493; doi:10.3390/pr2020466
Received: 15 January 2014 / Revised: 15 March 2014 / Accepted: 1 April 2014 / Published: 5 June 2014
Cited by 6 | PDF Full-text (2866 KB) | HTML Full-text | XML Full-text
Abstract
The seminal work of Michael Faraday in 1850s transmuted the “Alchemy of gold” into a fascinating scientific endeavor over the millennia, particularly in the past half century. Gold nanoparticles (GNPs) arguably hold the central position of nanosciences due to their intriguing size-and-shape dependent
[...] Read more.
The seminal work of Michael Faraday in 1850s transmuted the “Alchemy of gold” into a fascinating scientific endeavor over the millennia, particularly in the past half century. Gold nanoparticles (GNPs) arguably hold the central position of nanosciences due to their intriguing size-and-shape dependent physicochemical properties, non-toxicity, and ease of functionalization and potential for wide range of applications. The core chemistry involved in the syntheses is essentially not very different from what Michael Faraday resorted to: transforming ions into metallic gold using mild reducing agents. However, the process of such reduction and outcome (shapes and sizes) are intricately dependent on basic operational parameters such as sequence of addition and efficiency of mixing of the reagents. Hence, irreproducibility in synthesis and maintaining batch-to-batch quality are major obstacles in this seemingly straightforward process, which poses challenges in scaling-up. Microreactors, by the virtue of excellent control over reagent mixing in space and time within narrow channel networks, opened a new horizon of possibilities to tackle such problems to produce GNPs in more reliable, reproducible and scalable ways. In this review, we will delineate the state-of-the-art of GNPs synthesis using microreactors and will discuss in length how such “flask-to-chip” paradigm shift may revolutionize the very concept of nanosyntheses. Full article
Open AccessReview Bioreactor Systems for Human Bone Tissue Engineering
Processes 2014, 2(2), 494-525; doi:10.3390/pr2020494
Received: 24 February 2014 / Revised: 19 April 2014 / Accepted: 24 April 2014 / Published: 11 June 2014
Cited by 6 | PDF Full-text (2334 KB) | HTML Full-text | XML Full-text
Abstract
Critical size skeletal defects resulting from trauma and pathological disorders still remain a major clinical problem worldwide. Bone engineering aims at generating unlimited amounts of viable tissue substitutes by interfacing osteocompetent cells of different origin and developmental stage with compliant biomaterial scaffolds, and
[...] Read more.
Critical size skeletal defects resulting from trauma and pathological disorders still remain a major clinical problem worldwide. Bone engineering aims at generating unlimited amounts of viable tissue substitutes by interfacing osteocompetent cells of different origin and developmental stage with compliant biomaterial scaffolds, and culture the cell/scaffold constructs under proper culture conditions in bioreactor systems. Bioreactors help supporting efficient nutrition of cultured cells and allow the controlled provision of biochemical and biophysical stimuli required for functional regeneration and production of clinically relevant bone grafts. In this review, the authors report the advances in the development of bone tissue substitutes using human cells and bioreactor systems. Principal types of bioreactors are reviewed, including rotating wall vessels, spinner flasks, direct and indirect flow perfusion bioreactors, as well as compression systems. Specifically, the review deals with: (i) key elements of bioreactor design; (ii) range of values of stress imparted to cells and physiological relevance; (iii) maximal volume of engineered bone substitutes cultured in different bioreactors; and (iv) experimental outcomes and perspectives for future clinical translation. Full article
(This article belongs to the Special Issue Design of Bioreactor Systems for Tissue Engineering)

Journal Contact

MDPI AG
Processes Editorial Office
St. Alban-Anlage 66, 4052 Basel, Switzerland
processes@mdpi.com
Tel. +41 61 683 77 34
Fax: +41 61 302 89 18
Editorial Board
Contact Details Submit to Processes
Back to Top