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267 KiB

Open AccessArticle

Analysis of Electromyographic Signals from Rats’ Stomaches for Detection and Classification of Motility

by Laura Ivoone Garay Jiménez, Pablo Rogelio Hernández Rodríguez, Roberto Muñoz Guerrero and Emma Gloria Ramos Ramírez

Sensors 2008, 8(5), 2974-2985; https://doi.org/10.3390/s8052974 - 6 May 2008

Viewed by 11945

Abstract

This paper presents the analysis of the electromyographic signals from rat stomaches to identify and classify contractions. The results were validated with both visual identification and an ultrasonic system to guarantee the reference. Some parameters were defined and associated to the energy of [...] Read more.

This paper presents the analysis of the electromyographic signals from rat stomaches to identify and classify contractions. The results were validated with both visual identification and an ultrasonic system to guarantee the reference. Some parameters were defined and associated to the energy of the signal in frequency domain and grouped in a P vector. The parameters were statistically analyzed and according to the results, an artificial neuronal network was designed to use the P vectors as inputs to classify the electrical signals related to the contraction conditions. A first approach classification was performed with and without contraction classes (CR and NCR), then the same database were subdivided in four classes: with induced contraction (ICR), spontaneous contraction (SCR), without contraction due a post mortem condition (PMR) or under physiological conditions (PNCR). In a two-class classifier, performance was 86%, 93% and 91% of detections for each electrogastromyografic (EGMG) signal from each of three pairs of electrodes considered. Because in the four-class classifier, enough data was not collected for the first pair, then a three-class classifier with 82% of performance was used. For the other two EGMG signals electrode pairs, performance was of 76% and 86% respectively. Based in the results, the analysis of P vectors could be used as a contraction detector in motility studies due to different stimuli in a rat model. Full article

(This article belongs to the Special Issue Physiological Sensing)

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237 KiB

Open AccessArticle

Determination of DPPH Radical Oxidation Caused by Methanolic Extracts of Some Microalgal Species by Linear Regression Analysis of Spectrophotometric Measurements

by Kai Marxen, Klaus Heinrich Vanselow, Sebastian Lippemeier, Ralf Hintze, Andreas Ruser and Ulf-Peter Hansen

Sensors 2007, 7(10), 2080-2095; https://doi.org/10.3390/s7102080 - 3 Oct 2007

Cited by 180 | Viewed by 22043

Abstract

The demonstrated modified spectrophotometric method makes use of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and its specific absorbance properties. Theabsorbance decreases when the radical is reduced by antioxidants. In contrast to otherinvestigations, the absorbance was measured at a wavelength of 550 nm. This wavelengthenabled the [...] Read more.

The demonstrated modified spectrophotometric method makes use of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and its specific absorbance properties. Theabsorbance decreases when the radical is reduced by antioxidants. In contrast to otherinvestigations, the absorbance was measured at a wavelength of 550 nm. This wavelengthenabled the measurements of the stable free DPPH radical without interference frommicroalgal pigments. This approach was applied to methanolic microalgae extracts for twodifferent DPPH concentrations. The changes in absorbance measured vs. the concentrationof the methanolic extract resulted in curves with a linear decrease ending in a saturationregion. Linear regression analysis of the linear part of DPPH reduction versus extractconcentration enabled the determination of the microalgae’s methanolic extractsantioxidative potentials which was independent to the employed DPPH concentrations. Theresulting slopes showed significant differences (6 - 34 μmol DPPH g^-1 extractconcentration) between the single different species of microalgae (Anabaena sp.,Isochrysis galbana, Phaeodactylum tricornutum, Porphyridium purpureum, Synechocystissp. PCC6803) in their ability to reduce the DPPH radical. The independency of the signal on the DPPH concentration is a valuable advantage over the determination of the EC50 value. Full article

(This article belongs to the Special Issue Physiological Sensing)

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285 KiB

Open AccessArticle

Mechanosensor Channels in Mammalian Somatosensory Neurons

by Matthieu Raoux, Lise Rodat-Despoix, Nathalie Azorin, Aurélie Giamarchi, Jizhe Hao, François Maingret, Marcel Crest, Bertrand Coste and Patrick Delmas

Sensors 2007, 7(9), 1667-1682; https://doi.org/10.3390/s7091667 - 3 Sep 2007

Cited by 13 | Viewed by 12451

Abstract

Mechanoreceptive sensory neurons innervating the skin, skeletal muscles andviscera signal both innocuous and noxious information necessary for proprioception, touchand pain. These neurons are responsible for the transduction of mechanical stimuli intoaction potentials that propagate to the central nervous system. The ability of these [...] Read more.

Mechanoreceptive sensory neurons innervating the skin, skeletal muscles andviscera signal both innocuous and noxious information necessary for proprioception, touchand pain. These neurons are responsible for the transduction of mechanical stimuli intoaction potentials that propagate to the central nervous system. The ability of these cells todetect mechanical stimuli impinging on them relies on the presence of mechanosensitivechannels that transduce the external mechanical forces into electrical and chemical signals.Although a great deal of information regarding the molecular and biophysical properties ofmechanosensitive channels in prokaryotes has been accumulated over the past two decades,less is known about the mechanosensitive channels necessary for proprioception and thesenses of touch and pain. This review summarizes the most pertinent data onmechanosensitive channels of mammalian somatosensory neurons, focusing on theirproperties, pharmacology and putative identity. Full article

(This article belongs to the Special Issue Physiological Sensing)

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439 KiB

Open AccessArticle

Development of a Molecularly Imprinted Biomimetic Electrode

by Lisa M. Kindschy and Evangelyn C. Alocilja

Sensors 2007, 7(8), 1630-1642; https://doi.org/10.3390/s7081630 - 27 Aug 2007

Cited by 20 | Viewed by 10043

Abstract

The technique of molecular imprinting produces artificial receptor sites in apolymer that can be used in a biomimetic sensor. This research extends previous studies ofa molecularly imprinted polymer (MIP) biomimetic sensor for the small drug theophylline.The presence of theophylline in the biomimetic sensor [...] Read more.

The technique of molecular imprinting produces artificial receptor sites in apolymer that can be used in a biomimetic sensor. This research extends previous studies ofa molecularly imprinted polymer (MIP) biomimetic sensor for the small drug theophylline.The presence of theophylline in the biomimetic sensor was monitored by analyzing thepeak currents from cyclic voltammetry experiments. The functional working range of theMIP modified electrode was 2 - 4 mM theophylline. The concentration of theophyllinethat resulted in the best signal was 3 mM. The MIP sensor showed no response to thestructurally related molecule caffeine, and therefore was selective to the target analytetheophylline. This research will provide the foundation for future studies that will result indurable biomimetic sensors that can offer a viable alternative to current sensors. Full article

(This article belongs to the Special Issue Physiological Sensing)

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987 KiB

Open AccessArticle

Chemomechanical Polymers as Sensors and Actuators for Biological and Medicinal Applications

by Hans-Jörg Schneider, Kazuaki Kato and Robert M. Strongin

Sensors 2007, 7(8), 1578-1611; https://doi.org/10.3390/s7081578 - 27 Aug 2007

Cited by 59 | Viewed by 16503

Abstract

Changes in the chemical environment can trigger large motions in chemomechanical polymers. The unique feature of such intelligent materials, mostly in the form of hydrogels, is therefore, that they serve as sensors and actuators at the same time, and do not require any [...] Read more.

Changes in the chemical environment can trigger large motions in chemomechanical polymers. The unique feature of such intelligent materials, mostly in the form of hydrogels, is therefore, that they serve as sensors and actuators at the same time, and do not require any measuring devices, transducers or power supplies. Until recently the most often used of these materials responded to changes in pH. Chemists are now increasingly using supramolecular recognition sites in materials, which are covalently bound to the polymer backbone. This allows one to use a nearly unlimited variety of guest (or effector) compounds in the environment for a selective response by automatically triggered size changes. This is illustrated with non-covalent interactions of effectors comprising of metal ions, isomeric organic compounds, including enantiomers, nucleotides, aminoacids, and peptides. Two different effector molecules can induce motions as functions of their concentration, thus representing a logical AND gate. This concept is particularly fruitful with effector compounds such as peptides, which only trigger size changes if, e.g. copper ions are present in the surroundings. Another principle relies on the fast formation of covalent bonds between an effector and the chemomechanical polymer. The most promising application is the selective interaction of covalently fixed boronic acid residues with glucose, which renders itself not only for sensing, but eventually also for delivery of drugs such as insulin. The speed of the responses can significantly increase by increasing the surface to volume ratio of the polymer particles. Of particular interest is the sensitivity increase which can be reached by downsizing the particle volume. Full article

(This article belongs to the Special Issue Physiological Sensing)

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2900 KiB

Open AccessArticle

Proposal for an Ultrasonic Tool to Monitor the Osseointegration of Dental Implants

by Marina Storani De Almeida, Carlos Dias Maciel and José Carlos Pereira

Sensors 2007, 7(7), 1224-1237; https://doi.org/10.3390/s7071224 - 16 Jul 2007

Cited by 45 | Viewed by 13864

Abstract

The longevity of dental implants depends on osseointegration, which providesload-bearing capacity without putting the prosthesis at risk from micromotions at theimplant-bone interface. This research involved an analysis of the viability of an ultrasonicevaluation tool to quantify osseointegration. Ultrasonic transmission is directly dependenton the [...] Read more.

The longevity of dental implants depends on osseointegration, which providesload-bearing capacity without putting the prosthesis at risk from micromotions at theimplant-bone interface. This research involved an analysis of the viability of an ultrasonicevaluation tool to quantify osseointegration. Ultrasonic transmission is directly dependenton the difference between the acoustic impedance of materials in intimate contact witheach other. The closer their acoustic impedances the more intense their transmission.Therefore, an analysis of the ultrasonic echoes would presumably allow for a quantitativeevaluation of the bone tissue that has grown into the pores of the implant. In addition, theliterature reports that bone fracture healing can be accelerated by the application of acontrolled low-amplitude mechanical stimulus on the site of the lesion. In fact, acousticpressure waves of low-intensity pulsed ultrasound are reportedly a secure technique forpromoting mechanical stimulus without impairing the healing process. Many experimentaland clinical trials have confirmed that daily transcutaneous ultrasound applications on theinjured site are beneficial to the enhancement of fractured bone. This proposal aims tobring together the characteristics of ultrasound propagation and the positive effect ofultrasound on bone growth into a single tool that quantitatively monitors the evolution ofthe osseointegration process. The viability of a device with these features was investigatedthrough simulations and experimentally. The initial simulations were conducted to explorethe influence of waveguide shapes on the tool’s sensitivity to changes in the implantsupporting media. The waveguides were designed in two parts, one consisting of a screw-shaped part to attach to the implant and the other a conical or step-shaped part to which the ultrasonic source was fixed in the first simulations. The step-shaped waveguide proved to be the more sensitive; intermediate stages of the osseointegration process were simulated and experiments were conducted with the step-shaped aluminum waveguide attached to a cylindrical aluminum nut embedded at different depths, so that the results obtained were only due to lateral attachment of the parts. These devices indicated that the transmission of ultrasound through the lateral surface of the implant by dilatational waves could render this tool suitable for monitoring the osseointegration of dental implants. Full article

(This article belongs to the Special Issue Physiological Sensing)

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137 KiB

Open AccessArticle

Step Prediction During Perturbed Standing Using Center Of Pressure Measurements

by Xavier Tortolero, Kei Masani and Milos R. Popovic

Sensors 2007, 7(4), 459-472; https://doi.org/10.3390/s7040459 - 18 Apr 2007

Cited by 5 | Viewed by 9922

Abstract

The development of a sensor that can measure balance during quiet standing and predict stepping response in the event of perturbation has many clinically relevant applica- tions, including closed-loop control of a neuroprothesis for standing. This study investigated the feasibility of an algorithm [...] Read more.

The development of a sensor that can measure balance during quiet standing and predict stepping response in the event of perturbation has many clinically relevant applica- tions, including closed-loop control of a neuroprothesis for standing. This study investigated the feasibility of an algorithm that can predict in real-time when an able-bodied individual who is quietly standing will have to make a step to compensate for an external perturbation. Anterior and posterior perturbations were performed on 16 able-bodied subjects using a pul- ley system with a dropped weight. A linear relationship was found between the peak center of pressure (COP) velocity and the peak COP displacement caused by the perturbation. This result suggests that one can predict when a person will have to make a step based on COP velocity measurements alone. Another important feature of this finding is that the peak COP velocity occurs considerably before the peak COP displacement. As a result, one can predict if a subject will have to make a step in response to a perturbation sufficiently ahead of the time when the subject is actually forced to make the step. The proposed instability detection algorithm will be implemented in a sensor system using insole sheets in shoes with minitur- ized pressure sensors by which the COPv can be continuously measured. The sensor system will be integrated in a closed-loop feedback system with a neuroprosthesis for standing in the near future. Full article

(This article belongs to the Special Issue Physiological Sensing)

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166 KiB

Open AccessArticle

Colorimetric and Fluorescent Sensing of SCN- Based on meso-Tetraphenylporphyrin/meso-Tetraphenylporphyrin Cobalt(II) System

by Ying Zhang, Hua Wang and Rong H. Yang

Sensors 2007, 7(3), 410-419; https://doi.org/10.3390/s7030410 - 30 Mar 2007

Cited by 38 | Viewed by 12484

Abstract

An approach for colorimetric and fluorescent sensing of thiocyanate (SCN-) hasbeen proposed based on the competitive-displacement strategy betweenmeso-tetraphenylporphyrin (TPP) and meso-tetraphenylporphyrin cobalt(II) (CoTPP). InTHF-water solution, TPP emits strong fluorescence at 651 nm; however, the fluorescence wasquenched stepwise by CoTPP, and then restored by [...] Read more.

An approach for colorimetric and fluorescent sensing of thiocyanate (SCN-) hasbeen proposed based on the competitive-displacement strategy betweenmeso-tetraphenylporphyrin (TPP) and meso-tetraphenylporphyrin cobalt(II) (CoTPP). InTHF-water solution, TPP emits strong fluorescence at 651 nm; however, the fluorescence wasquenched stepwise by CoTPP, and then restored by SCN-, the detection limit is 6.0 × 10^-4 M.The recognition of SCN- could also be easily achieved by visual way since the assemblysystem showed significant color change by the anion. Both the fluorescence and the colorchange of the system exhibits remarkably high selectivity to SCN- over a large series ofanions. The interaction mechanisms among TPP, CoTPP and SCN- were primarilyinvestigated by fluorescence lifetime. The quenching of TPP fluorescence is attributed to theformation of TPP/CoTPP aggregates, and the fluorescence restoration is due to the binding ofCoTPP with SCN-, releasing the free TPP. This simple system has the potential to be used asa latent fluorescent sensing approach for SCN- for environmental analysis. Full article

(This article belongs to the Special Issue Physiological Sensing)

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107 KiB

Open AccessArticle

A Non-invasive and Real-time Monitoring of the Regulation of Photosynthetic Metabolism Biosensor Based on Measurement of Delayed Fluorescence in Vivo

by Lingrui Zhang, Da Xing and Junsheng Wang

Sensors 2007, 7(1), 52-66; https://doi.org/10.3390/s7010052 - 24 Jan 2007

Cited by 17 | Viewed by 10466

Abstract

In this paper, a new principle biosensor for non-invasive monitoring of theregulation of photosynthetic metabolism based on quantitative measurement of delayedfluorescence (DF) is developed. The biosensor, which uses light-emitting diode lattice asexcitation light source and a compact Single Photon Counting Module to collect [...] Read more.

In this paper, a new principle biosensor for non-invasive monitoring of theregulation of photosynthetic metabolism based on quantitative measurement of delayedfluorescence (DF) is developed. The biosensor, which uses light-emitting diode lattice asexcitation light source and a compact Single Photon Counting Module to collect DF signal,is portable and can evaluate plant photosynthesis capacity in vivo. Compared with itsprimary version in our previous report, the biosensor can better control environmentalfactors. Moreover, the improved biosensor can automatically complete the measurements oflight and CO₂ response curves of DF intensity. In the experimental study, the testing of theimproved biosensor has been made in soybean (Glycine max Zaoshu No. 18) seedlingstreated with NaHSO₃ to induce changes in seedlings growth and photosynthetic metabolism.Contrast evaluations of seedlings photosynthesis were made from measurements of netphotosynthesis rate (Pn) based on consumption of CO₂ in tested plants. Current testingresults have demonstrated that the improved biosensor can accurately determine theregulatory effects of NaHSO₃ on photosynthetic metabolism. Therefore, the biosensorpresented here could be potential useful for real-time monitoring the regulatory effects ofplant growth regulators (PGRs) and other exogenous chemical factors on plant growth andphotosynthetic metabolism. Full article

(This article belongs to the Special Issue Physiological Sensing)

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