Bioengineering

Biolelectrode Models with Fractional Calculus

by Emmanuel Gonzalez

Published in the International Journal of Intelligent Control and Systems (IJICS)
Co-authored with L'ubomir Dorcak (Technical University of Kosice, Slovak Republic) and Celso Co (Ateneo De Manila University)

The introduction of fractional calculus has spurred a lot of possibilities in biomedical engineering and... more The introduction of fractional calculus has spurred a lot of possibilities in biomedical engineering and bioengineering research and development, especially in the modeling, design, and analysis of bioelectrodes. With the advent of memristors and fractional calculus, it is seen that these concepts would have several advantages and applications in such fields. In this short note, we present various bioelectrode equivalent circuit models including their impulse and frequency responses. The equivalent models presented utilize the concepts of memristors and fractional calculus.

Producción Biotecnológica de Hidrógeno y Uso de Foto Bioreactores

by Reinhardt Acuña Torres

Biotecnología Práctica y Aplicada

Producción Biotecnológica de Hidrógeno y Uso de Foto Bioreactores: Biofotólisis, Foto Bioreactor, Microalgas,... more Producción Biotecnológica de Hidrógeno y Uso de Foto Bioreactores: Biofotólisis, Foto Bioreactor, Microalgas, Bacterias, Fotosíntesis, Bioprocesos.

Capture of Rare Cells in Suspension with Antibody‐Coated Polystyrene Beads

by Norman Kabir

Electroffusion of individual animal cells directly to intact corneal epithelial tissue

by Edward Haller

Nanobiotechnology: Scaling up synthetic gene circuits.

by Guilhem Chalancon

A-magnetic optic-mechanical device to quantify finger kinematics for fMRI studies of bimanual coordination

by Maurizio Bertollo

“Bioethics” 10,000 words

by Byron Kaldis

SAGE Encyclopedia of Green Technology

Volumetric wear assessment of failed metal-on-metal hip resurfacing prostheses

by James Lord

J. Wear. Volume 272, Issue 1, 3 October 2011, Pages 79-87

Recent advancements in hip arthroplasty have allowed the operation to boast excellent results and high survivorship.... more Recent advancements in hip arthroplasty have allowed the operation to boast excellent results and high survivorship. However, failures do still occur and a major cause is complications arising from wear debris. It is essential therefore that debris is minimized by reducing wear at the bearing surface. One proposed method of achieving this wear reduction is through the use of metal-on-metal articulations. One of the latest manifestations of this biomaterial combination is in designs of hip resurfacing which are aimed at younger, more active patients who might wear out a conventional metal-on-polymer hip prosthesis. However, do these metal-on-metal hip resurfacings show less wear when implanted into patients?

Using a co-ordinate measuring machine and a bespoke computer program, volumetric wear measurements for retrieved Articular Surface Replacements (ASR™, DePuy) metal-on-metal hip resurfacings were undertaken. Thirty-two femoral heads and twenty-two acetabular cups were measured. Acetabular cups exhibited mean volumetric wear of 29.00 mm3 (range 1.35–109.72 mm3) and a wear rate of 11.02 mm3/year (range 0.30–63.59 mm3/year). Femoral heads exhibited mean wear of 22.41 mm3 (range 0.72–134.22 mm3) and a wear rate of 8.72 mm3/year (range 0.21–31.91 mm3/year). In the 22 cases where both head and cup from the same prosthesis were available, mean total wear rates of 21.66 mm3/year (range 0.51–95.50 mm3/year) were observed. Compared with in many vitro tests, these are significantly higher than those expected in a well functioning metal-on-metal hip resurfacing prosthesis and are of concern.

Deformation And Stress Of Cells In Turbulent Vortices

by Stefan Radl

Evaluating Factors That Influence Microbial Synthesis Yields by Linear Regression with Numerical and Ordinal Variables

by Yogesh Goyal

Biotechnology and Bioengineering, Wiley Publications 2011

In the production of chemicals via microbial fermentation, achieving a high yield is one of the most important... more In the production of chemicals via microbial fermentation, achieving a high yield is one of the most important objectives. We developed a statistical model to analyze influential factors that determine product yield by compiling data obtained from engineered Escherichia coli developed within last 10 years. Using both numerical and ordinal variables (e.g., enzymatic steps, cultivation conditions, and genetic modifications) as input parameters, our model revealed that cultivation modes, nutrient supplementation, and oxygen conditions were the three significant factors for improving product yield. Generally, the model showed that product yield decreases as the number of enzymatic steps in the biosynthesis pathway increases (7–9% loss of yield per enzymatic step). Moreover, overexpression of enzymes or removal of competitive pathways (e.g., knockout) does not necessarily result in an amplification of product yield (P-value >0.1), possibly because of limited capacity in the biosynthesis pathway to accommodate an increase in flux. The model not only provides general guidelines for metabolic engineering and fermentation processes, but also allows a priori estimation and comparison of product yields under designed cultivation conditions. Biotechnol. Bioeng. 2011; 108:893–901. © 2010 Wiley Periodicals, Inc.

The effect of sustained compression on oxygen metabolic transport in the intervertebral disc decreases with degenerative changes

by Jerome Noailly

Andrea Malandrino, Jérôme Noailly, Damien Lacroix

PLoS Computational Biology (2011) 7(8): e1002112. doi:10.1371/journal.pcbi.1002112
[Original Paper]

Intervertebral disc metabolic transport is essential to the functional spine and provides the cells with the nutrients... more Intervertebral disc metabolic transport is essential to the functional spine and provides the cells with the nutrients necessary to tissue maintenance. Disc degenerative changes alter the tissue mechanics, but interactions between mechanical loading and disc transport are still an open issue. A poromechanical finite element model of the human disc was coupled with oxygen and lactate transport models. Deformations and fluid flow were linked to transport predictions by including strain-dependent diffusion and advection. The two solute transport models were also coupled to account for cell metabolism. With this approach, the relevance of metabolic and mechano-transport couplings were assessed in the healthy disc under loading-recovery daily compression. Disc height, cell density and material degenerative changes were parametrically simulated to study their influence on the calculated solute concentrations. The effects of load frequency and amplitude were also studied in the healthy disc by considering short periods of cyclic compression. Results indicate that external loads influence the oxygen and lactate regional distributions within the disc when large volume changes modify diffusion distances and diffusivities, especially when healthy disc properties are simulated. Advection was negligible under both sustained and cyclic compression. Simulating degeneration, mechanical changes inhibited the mechanical effect on transport while disc height, fluid content, nucleus pressure and overall cell density reductions affected significantly transport predictions. For the healthy disc, nutrient concentration patterns depended mostly on the time of sustained compression and recovery. The relevant effect of cell density on the metabolic transport indicates the disturbance of cell number as a possible onset for disc degeneration via alteration of the metabolic balance. Results also suggest that healthy disc properties have a positive effect of loading on metabolic transport. Such relation, relevant to the maintenance of the tissue functional composition, would therefore link disc function with disc nutrition.

Cultivation of filamentous cyanobacteria (blue-green algae) in agro-industrial wastes and wastewaters

by Marwa Eldalatony

Recently research interest has focused on the production of biofuel from microalgae. Microalgae are photosyntheticmore Recently research interest has focused on the production of biofuel from microalgae. Microalgae are photosynthetic
microorganisms that grow utilizing solar energy, nevertheless, the quantities of fertilizers
that should be used for their production are enormous. One alternative to the use of synthetic fertilizers
is to employ wastes and wastewaters (W&WWs), especially from the agro-industrial sector which are
rich in inorganic pollutants such as nitrogen and phosphorus, which can be recovered. Simultaneously
with the cultivation of microalgae using wastes and wastewaters for biomass production, treatment of
the wastes and wastewaters occur through removal of the pollutants. Filamentous cyanobacteria appear
to be suitable candidates for cultivation in wastes and wastewaters because they produce biomass in satisfactory
quantity and can be harvested relatively easily due to their size and structure. In addition their
biomass composition can be manipulated by several environmental and operational factors in order to
produce biomass with concrete characteristics. Herein we review the factors that affect the biomass composition
of cyanobacteria and present several studies that discuss the culture of filamentous cyanobacteria
in agro-industrial wastes and wastewaters, with special emphasis on Spirulina

Effect of nitrogen and phosphorous deficiency on lipid content

by Marwa Eldalatony

Restoration of compressive loading properties of lumbar discs with a nucleus implant--a finite element analysis study

by Daniel Strange

Background Context
Discectomy is a common procedure for treating sciatica. However, both the operation and... more Background Context
Discectomy is a common procedure for treating sciatica. However, both the operation and preceding herniated disc alter the biomechanical properties of the spinal segment. The disc mechanics are also altered in patients with chronic contained herniation. The biomechanical properties of the disc can potentially be restored with an elastomeric nucleus replacement implanted via minimally invasive surgery.

Purpose
The purpose of this study was to determine whether the compressive characteristics of the intervertebral disc after a nucleotomy can be restored with an elastomeric nucleus replacement.

Study Design
A finite element model of the L4–L5 intervertebral disc was created to investigate the effect of the implantation of an elastomeric nucleus replacement on the biomechanical properties of the disc under axial loading.

Method
A L4–L5 physiologic intervertebral disc model was constructed and then modified to contain a range by volume of nucleotomies and nucleus replacements. The material properties of the nucleus replacement were based on experimental data for an elastomeric implant. The compressive stiffness, radial annular bulge, and stress distribution of the nucleotomy and nucleus replacement models were investigated under displacement-controlled loading.

Results
Removal of nucleus pulposus from the physiologic disc reduced the force necessary to compress the disc 2 mm by 50%, altered the von Mises stress distribution, and reduced the outward radial annular bulge. Replacing the natural nucleus pulposus of the physiologic disc with an artificial nucleus reduced the force required to compress the disc 2 mm by 10%, indicating a restoration of disc compressive stiffness. The von Mises stress distribution and annular bulge observed in the disc with an artificial nucleus were similar to that observed in the physiologic disc.

Conclusion
This study demonstrates that despite having different material properties, a nucleus replacement implant can restore the axial compressive mechanical properties of a disc after a discectomy. The implant carries compressive load and transfers the load into annular hoop stress.

Finite Element Study of a Novel Intervertebral Disc Substitute

by Jerome Noailly

Jérôme Noailly, Damien Lacroix, Josep A. Planell
Spine (2005), 30, 2257-2264
[Original Paper]

STUDY DESIGN: A new type of composite device with a similar structure to a natural lumbar intervertebral disc was... more STUDY DESIGN: A new type of composite device with a similar structure to a natural lumbar intervertebral disc was modeled, and its mechanical interaction with a L3-L5 lumbar spine segment was studied by a finite element analysis.
OBJECTIVE: To identify the influence of the prosthesis on the biomechanical changes induced in a L3-L4 lumbar spine segment model after having substituted the physiologic L4-L5 intervertebral disc by the implant.
SUMMARY OF BACKGROUND DATA: In our societies, the large number of back pain cases highly motivates the investigation of intervertebral disc prostheses. Postoperative complications induced by spinal fusion showed that the mechanical properties of the novel components and its interactivity with the rest of the spine are a critical point.
METHODS: The prosthesis replaced the L4-L5 intervertebral disc within a previously developed L3-L5 lumbar spine segment physiologic model. The effect of loads in compression, flexion, extension, and axial rotation was simulated, and two types of vertebrae-implant contact were compared to the physiologic model.
RESULTS: Models with disc substitute are much stiffer than the physiologic model. In case of perfect contact with the adjacent vertebrae, the implant behaves like a physiologic intervertebral disc and respects the surrounding motion segment biomechanics. Although no traumatic loads were calculated within the adjacent vertebrae, bone remodeling would be expected in the trabecular bone.
CONCLUSION: By using numerical methods, this study allows prediction of the static mechanical behavior of a new device within a lumbar spine structure, which appears very useful for preclinical study.

The effect of bone graft geometry on spinal fusion vertebral stresses

by Jerome Noailly

Damien Lacroix, Jérôme Noailly, Guillem Saló, Enric Cáceres, Josep A. Planell
Journal of Applied Biomaterials & Biomechanics (2006), 4, 135-142
[Original Article]

Spinal fusion is a frequent surgical technique in which the success is uncertain due to post-operative changes in the... more Spinal fusion is a frequent surgical technique in which the success is uncertain due to post-operative changes in the biomechanics of the spine. Bone grafts are good candidates for disc and vertebra substitutes due to their similar bone properties and their good osteogenic properties. However, the effect of the anatomic harvest location of the bone graft on the load transfer is unknown. A physiologic three-dimensional (3D) finite element model of a lumbar spine was modified to model spinal fusion with a fixator and a bone graft. Bone grafts were taken either from the femur, the tibia, or from the fibula in a configuration of three or six fragments. The configurations were submitted to physiological loadings, and strain and stress distributions were calculated within the vertebrae, the fixator and the bone grafts. Quantitative differences were found from one type of bone graft to another. It was found that fibula bone grafts provided better stability by carrying a large part of the load. However, femoral and tibial bone grafts provided a more similar strain distribution within the vertebrae compared to the physiologic model. For tibial bone grafts, load transfer was found to be sensitive to the orientation used during the surgery. The use of a femoral bone graft to replace one vertebra and two intervertebral discs was found to give a better biomechanical function than using a tibial or fibula bone graft. This surgical technique is proposed to be beneficial in the case of severe spinal trauma providing good interface is obtained between the bone graft and the vertebrae.

How Does the Geometry Affect the Internal Biomechanics of a Lumbar Spine Bi-Segment Finite Element Model? Consequences on the Validation Process.

by Jerome Noailly

Jérôme Noailly, Hans-Joachim Wilke, Josep A. Planell, Damien Lacroix
Journal of Biomechanics (2007), 40, 2414-2425
[Original Paper]

Numerical modelling can provide a thorough understanding of the mechanical influence on the spinal tissues and may... more Numerical modelling can provide a thorough understanding of the mechanical influence on the spinal tissues and may offer explanations to mechanically linked pathologies. Such objective might be achieved only if the models are carefully validated. Sensitivity study must be performed in order to evaluate the influence of the approximations inherent to modelling. In this study, a new geometrically accurate L3-L5 lumbar spine bi-segmental finite-element model was acquired by modifying a previously existing model. The effect of changes in bone geometry, ligament fibres distribution, nucleus position and disc height was investigated in flexion and extension by comparison of the results obtained from the model before and after the geometrical update. Additional calculations were performed in axial rotation and lateral bending in order to compare the computed ranges of motion (ROM) with experimental results. It was found that the geometrical parameters affected the stress distribution and strain energy in the zygapophysial joints, the ligaments, and the intervertebral disc, changing qualitatively and quantitatively their relative role in resisting the imposed loads. The predicted ROM were generally in good agreement with the experimental results, independently of the geometrical changes. Hence, although the model update affected its internal biomechanics, no conclusions could be drawn from the experimental data about the validation of a particular geometry. Hence the validation of the lumbar spine model should be based on the relative role of its structural components and not only on its global mobility.

A Poroviscoelastic Description of Fibrin Gels

by Jerome Noailly

Jérôme Noailly, Hans Van Oosterwyck, Wouter Wilson, Thomas M. Quinn, Keita Ito
Journal of Biomechanics (2008), 41, 3265-3269
[Technical Note]

The mechanical induction of specific cell phenotypes can only be properly controlled if the local stimuli applied to... more The mechanical induction of specific cell phenotypes can only be properly controlled if the local stimuli applied to the cells are known as a function of the external applied loads. Finite element analysis of the cell carriers would be one method to calculate these local conditions. Furthermore, the constitutive model of the construct material should be able to describe mechanical events known to be responsible for cell stimulation, such as interstitial fluid flow. The aim of this study was to define a biphasic constitutive model for fibrin, a natural hydrogel often used for tissue engineering but not yet thoroughly characterized. Large strain poroelastic and poroviscoelastic constitutive equations were implemented into a finite element model of a fibrin gel. The parameter values for both formulations were found by either analytically solving equivalent low strain equations, or by optimizing directly the large strain equations based on experimental stress relaxation data. No poroelastic parameters that satisfactorily described the fibrin carrier behaviour could be found, suggesting that network viscoelasticity and fluid-flow time-dependent behaviour must be separately accounted for. It was demonstrated that fibrin can be described as a poroviscoelastic material, but a large strain characterization of the parameter values was necessary. The analytical resolution of the low strain poroviscoelastic equations was, however, accurate enough to serve as a reliable initial condition for further optimization of the parameter values with the large strain formulation.

Influencing Biophysical Properties of Fibrin With Buffer Solutions

by Jerome Noailly

Esther Potier, Jérôme Noailly, Christoph M. Sprecher, Keita Ito
Journal of Materials Science (2010), 45, 2494-2503
[Original Paper]

Fibrin has been proposed as cell scaffold for numerous tissue engineering applications. While most of the studies have... more Fibrin has been proposed as cell scaffold for numerous tissue engineering applications. While most of the studies have focused on fibrinogen and thrombin, other components of fibrin can also affect its properties. The present study aimed to evaluate the effects of buffer solution composition on fibrin biophysical properties. Fibrin scaffolds were synthesized with different calcium, chloride, and factor XIII (FXIII) final concentrations. Light transmission was determined as a relative, semi-quantitative estimator of fiber structure differences, and two compositions, resulting in translucent and opaque gels, were tested for mechanical and biological properties. Gels were seeded with mouse mesenchymal cells, C3H10T1/2, or bovine bone marrow-derived mesenchymal stromal cells and cultured up to 10 or 24 days, before cell number, morphology and distribution were evaluated. Calcium increased gel opacity (i.e., fiber thickness), while chloride and FXIII decreased it. Opaque gels displayed a fluid-like viscous behavior while translucent gels showed improved elastic properties. Both compositions supported survival of both cell types with opaque gels leading to better proliferation, but significant scaffold shrinkage after 17 days of culture. These results demonstrated that calcium, chloride, and FXIII modulate the biophysical properties of fibrin, and can be used to adjust mechanical and biological properties for tissue engineering applications.

Directing bone marrow-derived stromal cell function with mechanics

by Jerome Noailly

Esther Potier, Jérôme Noailly, Keita Ito
Journal of Biomechanics (2010), 43, 807-817
[Review]

Because bone marrow-derived stromal cells (BMSCs) are able to generate many cell types, they are envisioned as source... more Because bone marrow-derived stromal cells (BMSCs) are able to generate many cell types, they are envisioned as source of regenerative cells to repair numerous tissues, including bone, cartilage, and ligaments. Success of BMSC-based therapies, however, relies on a number of methodological improvements, among which better understanding and control of the BMSC differentiation pathways. Since many years, the biochemical environment is known to govern BMSC differentiation, but more recent evidences show that the biomechanical environment is also directing cell functions. Using in vitro systems that aim to reproduce selected components of the in vivo mechanical environment, it was demonstrated that mechanical loadings can affect BMSC proliferation and improve the osteogenic, chondrogenic, or myogenic phenotype of BMSCs. These effects, however, seem to be modulated by parameters other than mechanics, such as substrate nature or soluble biochemical environment. This paper reviews and discusses recent experimental data showing that despite some knowledge limitation, mechanical stimulation already constitutes an additional and efficient tool to drive BMSC differentiation.