Bioengineering

7100 KiB

Open AccessArticle

Finite Element Simulation and Additive Manufacturing of Stiffness-Matched NiTi Fixation Hardware for Mandibular Reconstruction Surgery

by Ahmadreza Jahadakbar, Narges Shayesteh Moghaddam, Amirhesam Amerinatanzi, David Dean, Haluk E. Karaca and Mohammad Elahinia

Bioengineering 2016, 3(4), 36; https://doi.org/10.3390/bioengineering3040036 - 19 Dec 2016

Cited by 62 | Viewed by 13686

Abstract

Process parameters and post-processing heat treatment techniques have been developed to produce both shape memory and superelastic NiTi using Additive Manufacturing. By introducing engineered porosity, the stiffness of NiTi can be tuned to the level closely matching cortical bone. Using additively manufactured porous [...] Read more.

Process parameters and post-processing heat treatment techniques have been developed to produce both shape memory and superelastic NiTi using Additive Manufacturing. By introducing engineered porosity, the stiffness of NiTi can be tuned to the level closely matching cortical bone. Using additively manufactured porous superelastic NiTi, we have proposed the use of patient-specific, stiffness-matched fixation hardware, for mandible skeletal reconstructive surgery. Currently, Ti-6Al-4V is the most commonly used material for skeletal fixation devices. Although this material offers more than sufficient strength for immobilization during the bone healing process, the high stiffness of Ti-6Al-4V implants can cause stress shielding. In this paper, we present a study of mandibular reconstruction that uses a dry cadaver mandible to validate our geometric and biomechanical design and fabrication (i.e., 3D printing) of NiTi skeletal fixation hardware. Based on the reference-dried mandible, we have developed a Finite Element model to evaluate the performance of the proposed fixation. Our results show a closer-to-normal stress distribution and an enhanced contact pressure at the bone graft interface than would be in the case with Ti-6Al-4V off-the-shelf fixation hardware. The porous fixation plates used in this study were fabricated by selective laser melting. Full article

(This article belongs to the Special Issue Advances in 3D Printing of Biomaterials)

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5394 KiB

Open AccessArticle

Biosilica from Living Diatoms: Investigations on Biocompatibility of Bare and Chemically Modified Thalassiosira weissflogii Silica Shells

by Stefania Roberta Cicco, Danilo Vona, Roberto Gristina, Eloisa Sardella, Roberta Ragni, Marco Lo Presti and Gianluca Maria Farinola

Bioengineering 2016, 3(4), 35; https://doi.org/10.3390/bioengineering3040035 - 16 Dec 2016

Cited by 55 | Viewed by 9578

Abstract

In the past decade, mesoporous silica nanoparticles (MSNs) with a large surface area and pore volume have attracted considerable attention for their application in drug delivery and biomedicine. Here we propose biosilica from diatoms as an alternative source of mesoporous materials in the [...] Read more.

In the past decade, mesoporous silica nanoparticles (MSNs) with a large surface area and pore volume have attracted considerable attention for their application in drug delivery and biomedicine. Here we propose biosilica from diatoms as an alternative source of mesoporous materials in the field of multifunctional supports for cell growth: the biosilica surfaces were chemically modified by traditional silanization methods resulting in diatom silica microparticles functionalized with 3-mercaptopropyl-trimethoxysilane (MPTMS) and 3-aminopropyl-triethoxysilane (APTES). Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses revealed that the –SH or –NH₂ were successfully grafted onto the biosilica surface. The relationship among the type of functional groups and the cell viability was established as well as the interaction of the cells with the nanoporosity of frustules. These results show that diatom microparticles are promising natural biomaterials suitable for cell growth, and that the surfaces, owing to the mercapto groups, exhibit good biocompatibility. Full article

(This article belongs to the Special Issue Mesoporous Materials in Drug Delivery and Regenerative Engineering 2016)

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2470 KiB

Open AccessArticle

Biodegradable Polymeric Substances Produced by a Marine Bacterium from a Surplus Stream of the Biodiesel Industry

by Sourish Bhattacharya, Sonam Dubey, Priyanka Singh, Anupama Shrivastava and Sandhya Mishra

Bioengineering 2016, 3(4), 34; https://doi.org/10.3390/bioengineering3040034 - 30 Nov 2016

Cited by 36 | Viewed by 7248

Abstract

Crude glycerol is generated as a by-product during transesterification process and during hydrolysis of fat in the soap-manufacturing process, and poses a problem for waste management. In the present approach, an efficient process was designed for simultaneous production of 0.2 g/L extracellular ε-polylysine [...] Read more.

Crude glycerol is generated as a by-product during transesterification process and during hydrolysis of fat in the soap-manufacturing process, and poses a problem for waste management. In the present approach, an efficient process was designed for simultaneous production of 0.2 g/L extracellular ε-polylysine and 64.6% (w/w) intracellular polyhydroxyalkanoate (PHA) in the same fermentation broth (1 L shake flask) utilizing Jatropha biodiesel waste residues as carbon rich source by marine bacterial strain (Bacillus licheniformis PL26), isolated from west coast of India. The synthesized ε-polylysine and polyhydroxyalkanoate PHA by Bacillus licheniformis PL26 was characterized by thermogravimetric analysis (TGA), differential scanning colorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and ¹H Nuclear magnetic resonance spectroscopy (NMR). The PHA produced by Bacillus licheniformis was found to be poly-3-hydroxybutyrate-co-3-hydroxyvalerate (P3HB-co-3HV). The developed process needs to be statistically optimized further for gaining still better yield of both the products in an efficient manner. Full article

(This article belongs to the Special Issue Advances in Polyhydroxyalkanoate (PHA) Production)

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Graphical abstract

2770 KiB

Open AccessArticle

An Investigation into Spent Coffee Waste as a Renewable Source of Bioactive Compounds and Industrially Important Sugars

by Damhan S. Scully, Amit K. Jaiswal and Nissreen Abu-Ghannam

Bioengineering 2016, 3(4), 33; https://doi.org/10.3390/bioengineering3040033 - 21 Nov 2016

Cited by 77 | Viewed by 9502

Abstract

Conventional coffee brewing techniques generate vast quantities of spent espresso grounds (SEGs) rich in lignocellulose and valuable bioactives. These bioactive compounds can be exploited as a nutraceutical or used in a range of food products, while breakdown of lignocellulose generates metabolizable sugars that [...] Read more.

Conventional coffee brewing techniques generate vast quantities of spent espresso grounds (SEGs) rich in lignocellulose and valuable bioactives. These bioactive compounds can be exploited as a nutraceutical or used in a range of food products, while breakdown of lignocellulose generates metabolizable sugars that can be used for the production of various high-value products such as biofuels, amino acids and enzymes. Response surface methodology (RSM) was used to optimize the enzymatic saccharification of lignocellulose in SEGs following a hydrothermal pretreatment. A maximum reducing sugar yield was obtained at the following optimized hydrolysis conditions: 4.97 g of pretreated SEGs, 120 h reaction time, and 1246 and 250 µL of cellulase and hemicellulase, respectively. Industrially important sugars (glucose, galactose and mannose) were identified as the principal hydrolysis products under the studied conditions. Total flavonoids (p = 0.0002), total polyphenols (p = 0.03) and DPPH free-radical scavenging activity (p = 0.004) increased significantly after processing. A 14-fold increase in caffeine levels was also observed. This study provides insight into SEGs as a promising source of industrially important sugars and polyphenols. Full article

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2890 KiB

Open AccessArticle

Fluorometric In Situ Monitoring of an Escherichia coli Cell Factory with Cytosolic Expression of Human Glycosyltransferase GalNAcT2: Prospects and Limitations

by Karen Schwab, Jennifer Lauber and Friedemann Hesse

Bioengineering 2016, 3(4), 32; https://doi.org/10.3390/bioengineering3040032 - 21 Nov 2016

Cited by 3 | Viewed by 6030

Abstract

The glycosyltransferase HisDapGalNAcT2 is the key protein of the Escherichia coli (E. coli) SHuffle^® T7 cell factory which was genetically engineered to allow glycosylation of a protein substrate in vivo. The specific activity of the glycosyltransferase requires time-intensive analytics, but [...] Read more.

The glycosyltransferase HisDapGalNAcT2 is the key protein of the Escherichia coli (E. coli) SHuffle^® T7 cell factory which was genetically engineered to allow glycosylation of a protein substrate in vivo. The specific activity of the glycosyltransferase requires time-intensive analytics, but is a critical process parameter. Therefore, it has to be monitored closely. This study evaluates fluorometric in situ monitoring as option to access this critical process parameter during complex E. coli fermentations. Partial least square regression (PLS) models were built based on the fluorometric data recorded during the EnPresso^® B fermentations. Capable models for the prediction of glucose and acetate concentrations were built for these fermentations with rout mean squared errors for prediction (RMSEP) of 0.19 g·L⁻¹ and 0.08 g·L⁻¹, as well as for the prediction of the optical density (RMSEP 0.24). In situ monitoring of soluble enzyme to cell dry weight ratios (RMSEP 5.5 × 10⁻⁴ µg w/w) and specific activity of the glycosyltransferase (RMSEP 33.5 pmol·min⁻¹·µg⁻¹) proved to be challenging, since HisDapGalNAcT2 had to be extracted from the cells and purified. However, fluorescence spectroscopy, in combination with PLS modeling, proved to be feasible for in situ monitoring of complex expression systems. Full article

(This article belongs to the Special Issue Hybrid Modelling and Multi-Parametric Control of Bioprocesses)

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3295 KiB

Open AccessArticle

Focused Screening of ECM-Selective Adhesion Peptides on Cellulose-Bound Peptide Microarrays

by Kei Kanie, Yuto Kondo, Junki Owaki, Yurika Ikeda, Yuji Narita, Ryuji Kato and Hiroyuki Honda

Bioengineering 2016, 3(4), 31; https://doi.org/10.3390/bioengineering3040031 - 19 Nov 2016

Cited by 5 | Viewed by 6952

Abstract

The coating of surfaces with bio-functional proteins is a promising strategy for the creation of highly biocompatible medical implants. Bio-functional proteins from the extracellular matrix (ECM) provide effective surface functions for controlling cellular behavior. We have previously screened bio-functional tripeptides for feasibility of [...] Read more.

The coating of surfaces with bio-functional proteins is a promising strategy for the creation of highly biocompatible medical implants. Bio-functional proteins from the extracellular matrix (ECM) provide effective surface functions for controlling cellular behavior. We have previously screened bio-functional tripeptides for feasibility of mass production with the aim of identifying those that are medically useful, such as cell-selective peptides. In this work, we focused on the screening of tripeptides that selectively accumulate collagen type IV (Col IV), an ECM protein that accelerates the re-endothelialization of medical implants. A SPOT peptide microarray was selected for screening owing to its unique cellulose membrane platform, which can mimic fibrous scaffolds used in regenerative medicine. However, since the library size on the SPOT microarray was limited, physicochemical clustering was used to provide broader variation than that of random peptide selection. Using the custom focused microarray of 500 selected peptides, we assayed the relative binding rates of tripeptides to Col IV, collagen type I (Col I), and albumin. We discovered a cluster of Col IV-selective adhesion peptides that exhibit bio-safety with endothelial cells. The results from this study can be used to improve the screening of regeneration-enhancing peptides. Full article

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1359 KiB

Open AccessReview

Microbial Enzyme Production Using Lignocellulosic Food Industry Wastes as Feedstock: A Review

by Rajeev Ravindran and Amit K. Jaiswal

Bioengineering 2016, 3(4), 30; https://doi.org/10.3390/bioengineering3040030 - 16 Nov 2016

Cited by 124 | Viewed by 26028

Abstract

Enzymes are of great importance in the industry due to their substrate and product specificity, moderate reaction conditions, minimal by-product formation and high yield. They are important ingredients in several products and production processes. Up to 30% of the total production cost of [...] Read more.

Enzymes are of great importance in the industry due to their substrate and product specificity, moderate reaction conditions, minimal by-product formation and high yield. They are important ingredients in several products and production processes. Up to 30% of the total production cost of enzymes is attributed to the raw materials costs. The food industry expels copious amounts of processing waste annually, which is mostly lignocellulosic in nature. Upon proper treatment, lignocellulose can replace conventional carbon sources in media preparations for industrial microbial processes, such as enzyme production. However, wild strains of microorganisms that produce industrially important enzymes show low yield and cannot thrive on artificial substrates. The application of recombinant DNA technology and metabolic engineering has enabled researchers to develop superior strains that can not only withstand harsh environmental conditions within a bioreactor but also ensure timely delivery of optimal results. This article gives an overview of the current complications encountered in enzyme production and how accumulating food processing waste can emerge as an environment-friendly and economically feasible solution for a choice of raw material. It also substantiates the latest techniques that have emerged in enzyme purification and recovery over the past four years. Full article

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4228 KiB

Open AccessArticle

Longitudinal Stretching for Maturation of Vascular Tissues Using Magnetic Forces

by Timothy R. Olsen, Megan Casco, Austin Herbst, Grace Evans, Taylor Rothermel, Lauren Pruett, Jared Reid, Kelly Barry, Michael P. Jaeggli, Dan T. Simionescu, Richard P. Visconti and Frank Alexis

Bioengineering 2016, 3(4), 29; https://doi.org/10.3390/bioengineering3040029 - 16 Nov 2016

Cited by 8 | Viewed by 5740

Abstract

Cellular spheroids were studied to determine their use as “bioinks” in the biofabrication of tissue engineered constructs. Specifically, magnetic forces were used to mediate the cyclic longitudinal stretching of tissues composed of Janus magnetic cellular spheroids (JMCSs), as part of a post-processing method [...] Read more.

Cellular spheroids were studied to determine their use as “bioinks” in the biofabrication of tissue engineered constructs. Specifically, magnetic forces were used to mediate the cyclic longitudinal stretching of tissues composed of Janus magnetic cellular spheroids (JMCSs), as part of a post-processing method for enhancing the deposition and mechanical properties of an extracellular matrix (ECM). The purpose was to accelerate the conventional tissue maturation process via novel post-processing techniques that accelerate the functional, structural, and mechanical mimicking of native tissues. The results of a forty-day study of JMCSs indicated an expression of collagen I, collagen IV, elastin, and fibronectin, which are important vascular ECM proteins. Most notably, the subsequent exposure of fused tissue sheets composed of JMCSs to magnetic forces did not hinder the production of these key proteins. Quantitative results demonstrate that cyclic longitudinal stretching of the tissue sheets mediated by these magnetic forces increased the Young’s modulus and induced collagen fiber alignment over a seven day period, when compared to statically conditioned controls. Specifically, the elastin and collagen content of these dynamically-conditioned sheets were 35- and three-fold greater, respectively, at seven days compared to the statically-conditioned controls at three days. These findings indicate the potential of using magnetic forces in tissue maturation, specifically through the cyclic longitudinal stretching of tissues. Full article

(This article belongs to the Special Issue Vascularized Tissue Models in Regenerative Engineering)

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1632 KiB

Open AccessArticle

Preparation and Biocompatible Surface Modification of Redox Altered Cerium Oxide Nanoparticle Promising for Nanobiology and Medicine

by Himansu Sekhar Nanda

Bioengineering 2016, 3(4), 28; https://doi.org/10.3390/bioengineering3040028 - 3 Nov 2016

Cited by 13 | Viewed by 6386

Abstract

The biocompatible surface modification of metal oxide nanoparticles via surface functionalization technique has been used as an important tool in nanotechnology and medicine. In this report, we have prepared aqueous dispersible, trivalent metal ion (samarium)-doped cerium oxide nanoparticles (SmCNPs) as model redox altered [...] Read more.

The biocompatible surface modification of metal oxide nanoparticles via surface functionalization technique has been used as an important tool in nanotechnology and medicine. In this report, we have prepared aqueous dispersible, trivalent metal ion (samarium)-doped cerium oxide nanoparticles (SmCNPs) as model redox altered CNPs of biological relevance. SmCNP surface modified with hydrophilic biocompatible (6-{2-[2-(2-methoxy-ethoxy)-ethoxy]-ethoxy}-hexyl) triethoxysilane (MEEETES) were prepared using ammonia-induced ethylene glycol-assisted precipitation method and were characterized using a variety of complementary characterization techniques. The chemical interaction of functional moieties with the surface of doped nanoparticle was studied using powerful ¹³C cross polarization magic angle sample spinning nuclear magnetic resonance spectroscopy. The results demonstrated the production of the extremely small size MEEETES surface modified doped nanoparticles with significant reduction in aggregation compared to their unmodified state. Moreover, the functional moieties had strong chemical interaction with the surface of the doped nanoparticles. The biocompatible surface modification using MEEETES should also be extended to several other transition metal ion doped and co-doped CNPs for the production of aqueous dispersible redox altered CNPs that are promising for nanobiology and medicine. Full article

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1771 KiB

Open AccessCommunication

A Simple Picaxe Microcontroller Pulse Source for Juxtacellular Neuronal Labelling

by Anthony J. M. Verberne

Bioengineering 2016, 3(4), 27; https://doi.org/10.3390/bioengineering3040027 - 19 Oct 2016

Viewed by 5061

Abstract

Juxtacellular neuronal labelling is a method which allows neurophysiologists to fill physiologically-identified neurons with small positively-charged marker molecules. Labelled neurons are identified by histochemical processing of brain sections along with immunohistochemical identification of neuropeptides, neurotransmitters, neurotransmitter transporters or biosynthetic enzymes. A microcontroller-based pulser [...] Read more.

Juxtacellular neuronal labelling is a method which allows neurophysiologists to fill physiologically-identified neurons with small positively-charged marker molecules. Labelled neurons are identified by histochemical processing of brain sections along with immunohistochemical identification of neuropeptides, neurotransmitters, neurotransmitter transporters or biosynthetic enzymes. A microcontroller-based pulser circuit and associated BASIC software script is described for incorporation into the design of a commercially-available intracellular electrometer for use in juxtacellular neuronal labelling. Printed circuit board construction has been used for reliability and reproducibility. The current design obviates the need for a separate digital pulse source and simplifies the juxtacellular neuronal labelling procedure. Full article

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2527 KiB

Open AccessCommunication

A Proof-of-Concept Study: Simple and Effective Detection of P and T Waves in Arrhythmic ECG Signals

by Mohamed Elgendi, Marianna Meo and Derek Abbott

Bioengineering 2016, 3(4), 26; https://doi.org/10.3390/bioengineering3040026 - 17 Oct 2016

Cited by 50 | Viewed by 10414

Abstract

A robust and numerically-efficient method based on two moving average filters, followed by a dynamic event-related threshold, has been developed to detect P and T waves in electrocardiogram (ECG) signals as a proof-of-concept. Detection of P and T waves is affected by the [...] Read more.

A robust and numerically-efficient method based on two moving average filters, followed by a dynamic event-related threshold, has been developed to detect P and T waves in electrocardiogram (ECG) signals as a proof-of-concept. Detection of P and T waves is affected by the quality and abnormalities in ECG recordings; the proposed method can detect P and T waves simultaneously through a unique algorithm despite these challenges. The algorithm was tested on arrhythmic ECG signals extracted from the MIT-BIH arrhythmia database with 21,702 beats. These signals typically suffer from: (1) non-stationary effects; (2) low signal-to-noise ratio; (3) premature atrial complexes; (4) premature ventricular complexes; (5) left bundle branch blocks; and (6) right bundle branch blocks. Interestingly, our algorithm obtained a sensitivity of 98.05% and a positive predictivity of 97.11% for P waves, and a sensitivity of 99.86% and a positive predictivity of 99.65% for T waves. These results, combined with the simplicity of the method, demonstrate that an efficient and simple algorithm can suit portable, wearable, and battery-operated ECG devices. Full article

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1746 KiB

Open AccessReview

Microfluidics for Antibiotic Susceptibility and Toxicity Testing

by Jing Dai, Morgan Hamon and Sachin Jambovane

Bioengineering 2016, 3(4), 25; https://doi.org/10.3390/bioengineering3040025 - 9 Oct 2016

Cited by 38 | Viewed by 9735

Abstract

The recent emergence of antimicrobial resistance has become a major concern for worldwide policy makers as very few new antibiotics have been developed in the last twenty-five years. To prevent the death of millions of people worldwide, there is an urgent need for [...] Read more.

The recent emergence of antimicrobial resistance has become a major concern for worldwide policy makers as very few new antibiotics have been developed in the last twenty-five years. To prevent the death of millions of people worldwide, there is an urgent need for a cheap, fast and accurate set of tools and techniques that can help to discover and develop new antimicrobial drugs. In the past decade, microfluidic platforms have emerged as potential systems for conducting pharmacological studies. Recent studies have demonstrated that microfluidic platforms can perform rapid antibiotic susceptibility tests to evaluate antimicrobial drugs’ efficacy. In addition, the development of cell-on-a-chip and organ-on-a-chip platforms have enabled the early drug testing, providing more accurate insights into conventional cell cultures on the drug pharmacokinetics and toxicity, at the early and cheaper stage of drug development, i.e., prior to animal and human testing. In this review, we focus on the recent developments of microfluidic platforms for rapid antibiotics susceptibility testing, investigating bacterial persistence and non-growing but metabolically active (NGMA) bacteria, evaluating antibiotic effectiveness on biofilms and combinatorial effect of antibiotics, as well as microfluidic platforms that can be used for in vitro antibiotic toxicity testing. Full article

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8229 KiB

Open AccessArticle

Purification of Monoclonal Antibodies Using a Fiber Based Cation-Exchange Stationary Phase: Parameter Determination and Modeling

by Jan Schwellenbach, Steffen Zobel, Florian Taft, Louis Villain and Jochen Strube

Bioengineering 2016, 3(4), 24; https://doi.org/10.3390/bioengineering3040024 - 2 Oct 2016

Cited by 9 | Viewed by 7102

Abstract

Monoclonal antibodies (mAb) currently dominate the market for protein therapeutics. Because chromatography unit operations are critical for the purification of therapeutic proteins, the process integration of novel chromatographic stationary phases, driven by the demand for more economic process schemes, is a field of [...] Read more.

Monoclonal antibodies (mAb) currently dominate the market for protein therapeutics. Because chromatography unit operations are critical for the purification of therapeutic proteins, the process integration of novel chromatographic stationary phases, driven by the demand for more economic process schemes, is a field of ongoing research. Within this study it was demonstrated that the description and prediction of mAb purification on a novel fiber based cation-exchange stationary phase can be achieved using a physico-chemical model. All relevant mass-transport phenomena during a bind and elute chromatographic cycle, namely convection, axial dispersion, boundary layer mass-transfer, and the salt dependent binding behavior in the fiber bed were described. This work highlights the combination of model adaption, simulation, and experimental parameter determination through separate measurements, correlations, or geometric considerations, independent from the chromatographic cycle. The salt dependent binding behavior of a purified mAb was determined by the measurement of adsorption isotherms using batch adsorption experiments. Utilizing a combination of size exclusion and protein A chromatography as analytic techniques, this approach can be extended to a cell culture broth, describing the salt dependent binding behavior of multiple components. Model testing and validation was performed with experimental bind and elute cycles using purified mAb as well as a clarified cell culture broth. A comparison between model calculations and experimental data showed a good agreement. The influence of the model parameters is discussed in detail. Full article

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3531 KiB

Open AccessArticle

Horizontally Aligned Carbon Nanotube Based Biosensors for Protein Detection

by Hu Chen, Jingfeng Huang, Derrick Wen Hui Fam and Alfred Iing Yoong Tok

Bioengineering 2016, 3(4), 23; https://doi.org/10.3390/bioengineering3040023 - 29 Sep 2016

Cited by 17 | Viewed by 6858

Abstract

A novel horizontally aligned single-walled carbon nanotube (CNT) Field Effect Transistor (FET)-based biosensing platform for real-time and sensitive protein detections is proposed. Aligned nanotubes were synthesized on quartz substrate using catalyst contact stamping, surface-guided morphological growth and chemical vapor deposition gas-guided growth methods. [...] Read more.

A novel horizontally aligned single-walled carbon nanotube (CNT) Field Effect Transistor (FET)-based biosensing platform for real-time and sensitive protein detections is proposed. Aligned nanotubes were synthesized on quartz substrate using catalyst contact stamping, surface-guided morphological growth and chemical vapor deposition gas-guided growth methods. Real-time detection of prostate-specific antigen (PSA) using as-prepared FET biosensors was demonstrated. The kinetic measurements of the biosensor revealed that the drain current (I_d) decreased exponentially as the concentration of PSA increased, indicating that the proposed FET sensor is capable of quantitative protein detection within a detection window of up to 1 µM. The limit of detection (LOD) achieved by the proposed platform was demonstrated to be 84 pM, which is lower than the clinically relevant level (133 pM) of PSA in blood. Additionally, the reported aligned CNT biosensor is a uniform sensing platform that could be extended to real-time detections of various biomarkers. Full article

(This article belongs to the Special Issue Nanoparticle Interaction with the Biological Milieu)

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1309 KiB

Open AccessCommunication

Eventogram: A Visual Representation of Main Events in Biomedical Signals

by Mohamed Elgendi

Bioengineering 2016, 3(4), 22; https://doi.org/10.3390/bioengineering3040022 - 22 Sep 2016

Cited by 12 | Viewed by 6557

Abstract

Biomedical signals carry valuable physiological information and many researchers have difficulty interpreting and analyzing long-term, one-dimensional, quasi-periodic biomedical signals. Traditionally, biomedical signals are analyzed and visualized using periodogram, spectrogram, and wavelet methods. However, these methods do not offer an informative visualization of main [...] Read more.

Biomedical signals carry valuable physiological information and many researchers have difficulty interpreting and analyzing long-term, one-dimensional, quasi-periodic biomedical signals. Traditionally, biomedical signals are analyzed and visualized using periodogram, spectrogram, and wavelet methods. However, these methods do not offer an informative visualization of main events within the processed signal. This paper attempts to provide an event-related framework to overcome the drawbacks of the traditional visualization methods and describe the main events within the biomedical signal in terms of duration and morphology. Electrocardiogram and photoplethysmogram signals are used in the analysis to demonstrate the differences between the traditional visualization methods, and their performance is compared against the proposed method, referred to as the “eventogram” in this paper. The proposed method is based on two event-related moving averages that visualizes the main time-domain events in the processed biomedical signals. The traditional visualization methods were unable to find dominant events in processed signals while the eventogram was able to visualize dominant events in signals in terms of duration and morphology. Moreover, eventogram-based detection algorithms succeeded with detecting main events in different biomedical signals with a sensitivity and positive predictivity >95%. The output of the eventogram captured unique patterns and signatures of physiological events, which could be used to visualize and identify abnormal waveforms in any quasi-periodic signal. Full article

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540 KiB

Open AccessArticle

Optimal Signal Quality Index for Photoplethysmogram Signals

by Mohamed Elgendi

Bioengineering 2016, 3(4), 21; https://doi.org/10.3390/bioengineering3040021 - 22 Sep 2016

Cited by 224 | Viewed by 15655

Abstract

A photoplethysmogram (PPG) is a noninvasive circulatory signal related to the pulsatile volume of blood in tissue and is typically collected by pulse oximeters. PPG signals collected via mobile devices are prone to artifacts that negatively impact measurement accuracy, which can lead to [...] Read more.

A photoplethysmogram (PPG) is a noninvasive circulatory signal related to the pulsatile volume of blood in tissue and is typically collected by pulse oximeters. PPG signals collected via mobile devices are prone to artifacts that negatively impact measurement accuracy, which can lead to a significant number of misleading diagnoses. Given the rapidly increased use of mobile devices to collect PPG signals, developing an optimal signal quality index (SQI) is essential to classify the signal quality from these devices. Eight SQIs were developed and tested based on: perfusion, kurtosis, skewness, relative power, non-stationarity, zero crossing, entropy, and the matching of systolic wave detectors. Two independent annotators annotated all PPG data (106 recordings, 60 s each) and a third expert conducted the adjudication of differences. The independent annotators labeled each PPG signal with one of the following labels: excellent, acceptable or unfit for diagnosis. All indices were compared using Mahalanobis distance, linear discriminant analysis, quadratic discriminant analysis, and support vector machine with leave-one-out cross-validation. The skewness index outperformed the other seven indices in differentiating between excellent PPG and acceptable, acceptable combined with unfit, and unfit recordings, with overall

F_{1}

scores of 86.0%, 87.2%, and 79.1%, respectively. Full article

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Bioengineering, Volume 3, Issue 4 (December 2016) – 16 articles

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