A new issue of this journal has just
been published. To see abstracts of the papers it contains (with links through
to the full papers) click here:
Selected
papers from the latest issue:
Synergizing nucleic acid aptamers with 1-dimensional nanostructures as label-free field-effect transistor biosensors
23 July 2013,
22:30:57
Publication date: 15 December
2013
Source:Biosensors and Bioelectronics, Volume 50
Author(s): Yit Lung Khung , Dario Narducci
Since the introduction by Gold et al. in 1990, nucleic acid aptamers had evolved to become a true contender in biosensors for protein and cell detections. Aptamers are short strands of synthetically designed DNA or RNA oligonucleotides that can be self-assembled into unique 3-dimensional structures and can bind to different proteins, cells or even small molecules at a high level of specificity and affinity. In recent years, there had been many reports in literature in using aptamers in place of conventional antibodies as capture biomolecules on the surface. This is mainly due to the better thermal stability properties and ease in production. Consequently, also these characteristics allowed the aptamers to find use in field effect transistors (FETs) based upon 1D nanostructured (1D-NS) as label-free biosensing. In terms of designing label-free platforms for biosensors applications, 1D-NS FET had been an attractive option due to reported high sensitivities toward protein targets arising from the large surface area for detection as well as to their label-free nature. Since the first aptamer-based 1D-NS FET biosensor had surfaced in 2005, there had been many more improvements in the overall design and sensitivity in recent years. In this review, the latest developments in synergizing these two interesting areas of research (aptamers and 1D-NS FET) will be discussed for a range of different nanowire types as well as for the detection results.
Source:Biosensors and Bioelectronics, Volume 50
Author(s): Yit Lung Khung , Dario Narducci
Since the introduction by Gold et al. in 1990, nucleic acid aptamers had evolved to become a true contender in biosensors for protein and cell detections. Aptamers are short strands of synthetically designed DNA or RNA oligonucleotides that can be self-assembled into unique 3-dimensional structures and can bind to different proteins, cells or even small molecules at a high level of specificity and affinity. In recent years, there had been many reports in literature in using aptamers in place of conventional antibodies as capture biomolecules on the surface. This is mainly due to the better thermal stability properties and ease in production. Consequently, also these characteristics allowed the aptamers to find use in field effect transistors (FETs) based upon 1D nanostructured (1D-NS) as label-free biosensing. In terms of designing label-free platforms for biosensors applications, 1D-NS FET had been an attractive option due to reported high sensitivities toward protein targets arising from the large surface area for detection as well as to their label-free nature. Since the first aptamer-based 1D-NS FET biosensor had surfaced in 2005, there had been many more improvements in the overall design and sensitivity in recent years. In this review, the latest developments in synergizing these two interesting areas of research (aptamers and 1D-NS FET) will be discussed for a range of different nanowire types as well as for the detection results.
Highly sensitive and selective phosphorescent chemosensors for hypochlorous acid based on ruthenium(II) complexes
23 July 2013,
22:30:57
Publication date: 15 December
2013
Source:Biosensors and Bioelectronics, Volume 50
Author(s): Run Zhang , Bo Song , Zhichao Dai , Zhiqiang Ye , Yunna Xiao , Yan Liu , Jingli Yuan
Microbicidal activity of hypochlorous acid (HOCl) plays pivotal roles in many biological processes, and suitable methods for the in vivo detection of HOCl are highly desirable. Herein we report the development of two novel ruthenium(II) complex-based phosphorescent chemosensors for HOCl, [Ru(bpy)2(DNCA-bpy)](PF6)2 (bpy: 2,2′-bipyridine; DNCA-bpy: 4-N-(2,4-dinitrophenyl)carboxamide-4′-methyl-2,2′-bipyridine) and [Ru(bpy)2(DNCH-bpy)](PF6)2 (DNCH-bpy: 4-N′-(2,4-dinitrophenyl)carbohydrazide-4′-methyl-2,2′-bipyridine). The two sensors are almost non-luminescent due to the intramolecular photoinduced electron transfer (PET) process from the Ru(II)-bpy moiety to dinitrophenyl group, but specific reaction of the sensors with HOCl in aqueous media can afford a highly luminescent derivative, [Ru(bpy)2(COOH-bpy)](PF6)2 (COOH-bpy: 4-carboxylic acid-4′-methyl-2,2′-bipyridine), accompanied by 190-fold and 1100-fold turn-on luminescence signal enhancement for [Ru(bpy)2(DNCA-bpy)](PF6)2 and [Ru(bpy)2(DNCH-bpy)](PF6)2, respectively. By taking advantage of high specificity and sensitivity of the chemosensor and excellent photophysical property of Ru(II) complex, [Ru(bpy)2(DNCH-bpy)](PF6)2 was applied for visualizing the endogenous HOCl generation in living macrophage cells during the processes of stimulation and phagocytosis via the red-emitting luminescence.
Source:Biosensors and Bioelectronics, Volume 50
Author(s): Run Zhang , Bo Song , Zhichao Dai , Zhiqiang Ye , Yunna Xiao , Yan Liu , Jingli Yuan
Microbicidal activity of hypochlorous acid (HOCl) plays pivotal roles in many biological processes, and suitable methods for the in vivo detection of HOCl are highly desirable. Herein we report the development of two novel ruthenium(II) complex-based phosphorescent chemosensors for HOCl, [Ru(bpy)2(DNCA-bpy)](PF6)2 (bpy: 2,2′-bipyridine; DNCA-bpy: 4-N-(2,4-dinitrophenyl)carboxamide-4′-methyl-2,2′-bipyridine) and [Ru(bpy)2(DNCH-bpy)](PF6)2 (DNCH-bpy: 4-N′-(2,4-dinitrophenyl)carbohydrazide-4′-methyl-2,2′-bipyridine). The two sensors are almost non-luminescent due to the intramolecular photoinduced electron transfer (PET) process from the Ru(II)-bpy moiety to dinitrophenyl group, but specific reaction of the sensors with HOCl in aqueous media can afford a highly luminescent derivative, [Ru(bpy)2(COOH-bpy)](PF6)2 (COOH-bpy: 4-carboxylic acid-4′-methyl-2,2′-bipyridine), accompanied by 190-fold and 1100-fold turn-on luminescence signal enhancement for [Ru(bpy)2(DNCA-bpy)](PF6)2 and [Ru(bpy)2(DNCH-bpy)](PF6)2, respectively. By taking advantage of high specificity and sensitivity of the chemosensor and excellent photophysical property of Ru(II) complex, [Ru(bpy)2(DNCH-bpy)](PF6)2 was applied for visualizing the endogenous HOCl generation in living macrophage cells during the processes of stimulation and phagocytosis via the red-emitting luminescence.
A dual-template imprinted polymer-modified carbon ceramic electrode for ultra trace simultaneous analysis of ascorbic acid and dopamine
23 July 2013,
22:30:57
Publication date: 15 December
2013
Source:Biosensors and Bioelectronics, Volume 50
Author(s): Bhim Bali Prasad , Darshika Jauhari , Mahavir Prasad Tiwari
A dual-template imprinted polymer film containing dispersed multiwalled carbon nanotubes was exploited in the fabrication of a typical, reproducible, and rugged carbon ceramic electrode, adopting “surface grafting from” approach for the growth of a nanometer thin coating on its surface. For this, chloro groups were first introduced at the exterior surface of silica-carbon composite electrode through sol–gel modification using (3-chloropropyl)-trimethoxysilane, followed by an iniferter (sodium diethyl dithiocarbamate) initiated photopolymerization of functional monomer (2,4,6-trisacrylamido-1,3,5-triazine), mixed templates (ascorbic acid and dopamine), and cross-linker (ethylene glycol dimethacrylate), in the presence of multiwalled carbon nanotubes. The modified sensor was validated for the simultaneous analysis of ascorbic acid and dopamine in aqueous, blood serum, cerebrospinal fluid, and pharmaceutical samples, using differential pulse anodic stripping voltammetric technique. The oxidation peak potentials for both analytes were found to be well apart approximately by 300mV, which was large enough to allow selective and sensitive analysis of one in the presence of other, without any cross reactivity, interferences and false-positives. The detection limits realized by the proposed sensor, under optimized conditions, were found to be as low as 2.24ngmL−1 for ascorbic acid and 0.21ngmL−1 for dopamine (S/N=3). Such stringent limits could be considered suitable for the primitive diagnosis of several chronic diseases, in clinical settings.
Source:Biosensors and Bioelectronics, Volume 50
Author(s): Bhim Bali Prasad , Darshika Jauhari , Mahavir Prasad Tiwari
A dual-template imprinted polymer film containing dispersed multiwalled carbon nanotubes was exploited in the fabrication of a typical, reproducible, and rugged carbon ceramic electrode, adopting “surface grafting from” approach for the growth of a nanometer thin coating on its surface. For this, chloro groups were first introduced at the exterior surface of silica-carbon composite electrode through sol–gel modification using (3-chloropropyl)-trimethoxysilane, followed by an iniferter (sodium diethyl dithiocarbamate) initiated photopolymerization of functional monomer (2,4,6-trisacrylamido-1,3,5-triazine), mixed templates (ascorbic acid and dopamine), and cross-linker (ethylene glycol dimethacrylate), in the presence of multiwalled carbon nanotubes. The modified sensor was validated for the simultaneous analysis of ascorbic acid and dopamine in aqueous, blood serum, cerebrospinal fluid, and pharmaceutical samples, using differential pulse anodic stripping voltammetric technique. The oxidation peak potentials for both analytes were found to be well apart approximately by 300mV, which was large enough to allow selective and sensitive analysis of one in the presence of other, without any cross reactivity, interferences and false-positives. The detection limits realized by the proposed sensor, under optimized conditions, were found to be as low as 2.24ngmL−1 for ascorbic acid and 0.21ngmL−1 for dopamine (S/N=3). Such stringent limits could be considered suitable for the primitive diagnosis of several chronic diseases, in clinical settings.
Microfluidic chip-based C. elegans microinjection system for investigating cell–cell communication in vivo
23 July 2013,
22:30:57
Publication date: 15 December
2013
Source:Biosensors and Bioelectronics, Volume 50
Author(s): Xingfu Zhao , Fei Xu , Lichun Tang , Wei Du , Xiaojun Feng , Bi-Feng Liu
The propagation of intercellular calcium wave (ICW) is essential for coordinating cellular activities in multicellular organisms. However, the limitations of existing analytical methods hamper the studies of this biological process in live animals. In this paper, we demonstrated for the first time a novel microfluidic system with an open chamber for on-chip microinjection of C. elegans and investigation of ICW propagations in vivo. Worms were long-term immobilized on the side wall of the open chamber by suction. Using an external micro-manipulator, localized chemical stimulation was delivered to single intestinal cells of the immobilized worms by microinjection. The calcium dynamics in the intestinal cells expressing Ca2+ indicator YC2.12 was simultaneously monitored by fluorescence imaging. As a result, thapsigargin injection induced ICW was observed in the intestinal cells of C. elegans. Further analysis of the ICW propagation was realized in the presence of heparin (an inhibitor for IP3 receptor), which allowed us to investigate the mechanism underlying intercellular calcium signaling. We expect this novel microfluidic platform to be a useful tool for studying cell–cell communication in multicellular organisms in vivo.
Source:Biosensors and Bioelectronics, Volume 50
Author(s): Xingfu Zhao , Fei Xu , Lichun Tang , Wei Du , Xiaojun Feng , Bi-Feng Liu
The propagation of intercellular calcium wave (ICW) is essential for coordinating cellular activities in multicellular organisms. However, the limitations of existing analytical methods hamper the studies of this biological process in live animals. In this paper, we demonstrated for the first time a novel microfluidic system with an open chamber for on-chip microinjection of C. elegans and investigation of ICW propagations in vivo. Worms were long-term immobilized on the side wall of the open chamber by suction. Using an external micro-manipulator, localized chemical stimulation was delivered to single intestinal cells of the immobilized worms by microinjection. The calcium dynamics in the intestinal cells expressing Ca2+ indicator YC2.12 was simultaneously monitored by fluorescence imaging. As a result, thapsigargin injection induced ICW was observed in the intestinal cells of C. elegans. Further analysis of the ICW propagation was realized in the presence of heparin (an inhibitor for IP3 receptor), which allowed us to investigate the mechanism underlying intercellular calcium signaling. We expect this novel microfluidic platform to be a useful tool for studying cell–cell communication in multicellular organisms in vivo.
Mediator and label free estimation of stress biomarker using electrophoretically deposited Ag@AgO–polyaniline hybrid nanocomposite
23 July 2013,
22:30:57
Publication date: 15 December
2013
Source:Biosensors and Bioelectronics, Volume 50
Author(s): Ajeet Kaushik , Abhay Vasudev , Sunil K. Arya , Shekhar Bhansali
Cortisol, a steroid hormone, is an important biomarker for psychological stress and its detection is gaining prominence for personalized health monitoring. In present work, electrophoretically deposited nanocomposite films of polyaniline (PANI) and core–shell Ag@AgO nanoparticles (NP~5nm) have been explored as an electro-active nanostructured platform for Anti-cortisol antibody (Anti-Cab) immobilization for electrochemical immunosensing of cortisol. Covalent binding of Anti-Cab onto Ag@AgO–PANI nanocomposite was achieved using EDC/NHS chemistry, which results in the amide bond formation between amino groups of PANI and COOH groups of anti-Cab. Nonspecific binding sites on the immunosensing electrodes were blocked using bovine serum albumin (BSA). The uniform distribution of electro-active and surface charged Ag@AgO NP in PANI matrix results in a nanoporous granular morphology (roughness~10nm) that provides a functionalized conductive microenvironment for Anti-Cab immobilization. The BSA/Anti-Cab/Ag@AgO–PANI/Au bioelectrodes have been characterized using electrochemical impedance technique (EIS), cyclic voltammetric (CV) technique and atomic force microscopic (AFM) technique, respectively. In CV studies nanocomposite exhibited characteristic response current peak corresponding to AgO NP (0.25V) with large magnitude of current response and resulted in high electron transport at the electrode–electrolyte interface without a mediator. Electrochemical response studies via CV for the fabricated BSA/Anti-Cab/Ag@AgO–PANI/Au immunosensor as a function of cortisol concentration exhibited a wide linear detection range of 1pM–1µM, a detection limit of 0.64pMmL−1(lower than ELISA), and high sensitivity 66µAM−1 with a regression coefficient of 0.998. The findings of present work may explore the application of Ag@AgO–PANI hybrid nanocomposite to detect cortisol and other biomarkers for point-of-care application.
Source:Biosensors and Bioelectronics, Volume 50
Author(s): Ajeet Kaushik , Abhay Vasudev , Sunil K. Arya , Shekhar Bhansali
Cortisol, a steroid hormone, is an important biomarker for psychological stress and its detection is gaining prominence for personalized health monitoring. In present work, electrophoretically deposited nanocomposite films of polyaniline (PANI) and core–shell Ag@AgO nanoparticles (NP~5nm) have been explored as an electro-active nanostructured platform for Anti-cortisol antibody (Anti-Cab) immobilization for electrochemical immunosensing of cortisol. Covalent binding of Anti-Cab onto Ag@AgO–PANI nanocomposite was achieved using EDC/NHS chemistry, which results in the amide bond formation between amino groups of PANI and COOH groups of anti-Cab. Nonspecific binding sites on the immunosensing electrodes were blocked using bovine serum albumin (BSA). The uniform distribution of electro-active and surface charged Ag@AgO NP in PANI matrix results in a nanoporous granular morphology (roughness~10nm) that provides a functionalized conductive microenvironment for Anti-Cab immobilization. The BSA/Anti-Cab/Ag@AgO–PANI/Au bioelectrodes have been characterized using electrochemical impedance technique (EIS), cyclic voltammetric (CV) technique and atomic force microscopic (AFM) technique, respectively. In CV studies nanocomposite exhibited characteristic response current peak corresponding to AgO NP (0.25V) with large magnitude of current response and resulted in high electron transport at the electrode–electrolyte interface without a mediator. Electrochemical response studies via CV for the fabricated BSA/Anti-Cab/Ag@AgO–PANI/Au immunosensor as a function of cortisol concentration exhibited a wide linear detection range of 1pM–1µM, a detection limit of 0.64pMmL−1(lower than ELISA), and high sensitivity 66µAM−1 with a regression coefficient of 0.998. The findings of present work may explore the application of Ag@AgO–PANI hybrid nanocomposite to detect cortisol and other biomarkers for point-of-care application.
Fluorescent imaging of acidic compartments in living cells with a high selective novel one-photon ratiometric and two-photon acidic pH probe
23 July 2013,
22:30:57
Publication date: 15 December
2013
Source:Biosensors and Bioelectronics, Volume 50
Author(s): Fang Miao , Guofen Song , Yuming Sun , Yong Liu , Fuqiang Guo , Weijia Zhang , Minggang Tian , Xiaoqiang Yu
Fluorescent imaging of acidic compartments in living cells was carried out successfully by a novel molecule (CAE) that contained a pyridine unit and a carbazole core. As the protonation of the pyridine N atom of CAE, pH-dependent absorption and fluorescence properties were shown with a pK a of 5.47 which matches the pH range of intracellular acidic compartments. Moreover, a large Stokes shift, a significant enhancement in ratios of I 544nm/I 460nm and a distinct two-photon turn-on character were exhibited in spectral analysis. Meanwhile, direct intracellular imaging and standard double-staining experiments of CAE and LTR (co-localization coefficient: 0.83) revealed that CAE is an effective one-photon ratiometric and two-photon acidic pH probe for imaging intracellular acidic compartments. The pH distribution pattern of intracellular acidic compartments can be obtained facilely by CAE. In especial, CAE possessed well membrane-permeability, brilliant selectivity among various bioanalyte and excellent counterstain compatibility with Hoechst 33342, MTR and LTR.
Source:Biosensors and Bioelectronics, Volume 50
Author(s): Fang Miao , Guofen Song , Yuming Sun , Yong Liu , Fuqiang Guo , Weijia Zhang , Minggang Tian , Xiaoqiang Yu
Fluorescent imaging of acidic compartments in living cells was carried out successfully by a novel molecule (CAE) that contained a pyridine unit and a carbazole core. As the protonation of the pyridine N atom of CAE, pH-dependent absorption and fluorescence properties were shown with a pK a of 5.47 which matches the pH range of intracellular acidic compartments. Moreover, a large Stokes shift, a significant enhancement in ratios of I 544nm/I 460nm and a distinct two-photon turn-on character were exhibited in spectral analysis. Meanwhile, direct intracellular imaging and standard double-staining experiments of CAE and LTR (co-localization coefficient: 0.83) revealed that CAE is an effective one-photon ratiometric and two-photon acidic pH probe for imaging intracellular acidic compartments. The pH distribution pattern of intracellular acidic compartments can be obtained facilely by CAE. In especial, CAE possessed well membrane-permeability, brilliant selectivity among various bioanalyte and excellent counterstain compatibility with Hoechst 33342, MTR and LTR.
Ultrasensitive thrombin detection based on direct electrochemistry of highly loaded hemoglobin spheres-encapsulated platinum nanoparticles as labels and electrocatalysts
23 July 2013,
22:30:57
Publication date: 15 December
2013
Source:Biosensors and Bioelectronics, Volume 50
Author(s): Yongmei Wu , Wenju Xu , Lijuan Bai , Yali Yuan , Huayu Yi , Yaqin Chai , Ruo Yuan
For the first time, a sandwich-type electrochemical method was proposed for ultrasensitive thrombin (TB) detection based on direct electrochemistry of highly loaded hemoglobin spheres-encapsulated platinum nanoparticles (PtNPs@Hb) as labels and electrocatalysts. The prepared PtNPs@Hb not only exhibited good biocompatibility, excellent electrocatalytic activity, but also presented redox activity of Hb. Thus, it was employed for the fabrication of aptasensor without any extraneous redox mediators, leading to a simple preparation process for the aptasensor. The high loading of Hb spheres as redox mediators could enhance the electrochemical signal. Importantly, the synergetic electrocatalytic behavior of Hb and PtNPs toward H2O2 reduction greatly amplified the electrochemical signal, resulting in the high sensitivity of aptasensor. Consequently, under optimal conditions, the designed aptasensor exhibited a lower detection limit of 0.05pM and wide dynamic linear range from 0.15pM to 40nM for TB detection. Additionally, the proposed mediator-free and signal-amplified electrochemical aptasensor showed great potential in portable and cost-effective TB sensing devices.
Source:Biosensors and Bioelectronics, Volume 50
Author(s): Yongmei Wu , Wenju Xu , Lijuan Bai , Yali Yuan , Huayu Yi , Yaqin Chai , Ruo Yuan
For the first time, a sandwich-type electrochemical method was proposed for ultrasensitive thrombin (TB) detection based on direct electrochemistry of highly loaded hemoglobin spheres-encapsulated platinum nanoparticles (PtNPs@Hb) as labels and electrocatalysts. The prepared PtNPs@Hb not only exhibited good biocompatibility, excellent electrocatalytic activity, but also presented redox activity of Hb. Thus, it was employed for the fabrication of aptasensor without any extraneous redox mediators, leading to a simple preparation process for the aptasensor. The high loading of Hb spheres as redox mediators could enhance the electrochemical signal. Importantly, the synergetic electrocatalytic behavior of Hb and PtNPs toward H2O2 reduction greatly amplified the electrochemical signal, resulting in the high sensitivity of aptasensor. Consequently, under optimal conditions, the designed aptasensor exhibited a lower detection limit of 0.05pM and wide dynamic linear range from 0.15pM to 40nM for TB detection. Additionally, the proposed mediator-free and signal-amplified electrochemical aptasensor showed great potential in portable and cost-effective TB sensing devices.
Fabrication of electrochemical NO sensor based on nanostructured film and its application in drug screening
23 July 2013,
22:30:57
Publication date: 15 December
2013
Source:Biosensors and Bioelectronics, Volume 50
Author(s): Li Wang , Peiyu Hu , Xiaocui Deng , Fang Wang , Zilin Chen
As a transcellular messenger molecule, nitric oxide (NO) is involved in many physiological and pathological processes. The accurate quantitative detection of NO in vivo is particularly important. In this work, a novel electrochemical NO sensor was fabricated via electro-polymerization of ethylenediamine (EDA) on multi-walled carbon nanotubes (MWNTs) film. The sensor combined the porous structure and good conductivity of MWNTs with the good electro-catalytic ability of p-EDA film. For the detection of NO, it has a linear range from 95nM to 11μM and the limit of detection reaches 95nM with excellent reproducibility. So it was successfully applied to monitor NO release from rat liver sample for investigating the inhibition or promotion effect of drugs including oleanolic acid (OA), baicalin and Nω-nitro-l-arginine methyl ester (l-NAME) on nitric oxide synthase (NOS). The results showed that OA could promote NO release and the amount of NO increases about 1.9 times, but baicalin and l-NAME could inhibit the release of NO and the amount of NO decreased by two-thirds and 37.5%, respectively.
Source:Biosensors and Bioelectronics, Volume 50
Author(s): Li Wang , Peiyu Hu , Xiaocui Deng , Fang Wang , Zilin Chen
As a transcellular messenger molecule, nitric oxide (NO) is involved in many physiological and pathological processes. The accurate quantitative detection of NO in vivo is particularly important. In this work, a novel electrochemical NO sensor was fabricated via electro-polymerization of ethylenediamine (EDA) on multi-walled carbon nanotubes (MWNTs) film. The sensor combined the porous structure and good conductivity of MWNTs with the good electro-catalytic ability of p-EDA film. For the detection of NO, it has a linear range from 95nM to 11μM and the limit of detection reaches 95nM with excellent reproducibility. So it was successfully applied to monitor NO release from rat liver sample for investigating the inhibition or promotion effect of drugs including oleanolic acid (OA), baicalin and Nω-nitro-l-arginine methyl ester (l-NAME) on nitric oxide synthase (NOS). The results showed that OA could promote NO release and the amount of NO increases about 1.9 times, but baicalin and l-NAME could inhibit the release of NO and the amount of NO decreased by two-thirds and 37.5%, respectively.
Genetically encoded FRET-based nanosensor for in vivo measurement of leucine
23 July 2013,
22:30:57
Publication date: 15 December
2013
Source:Biosensors and Bioelectronics, Volume 50
Author(s): Mohd Mohsin , M.Z. Abdin , Lata Nischal , Hemant Kardam , Altaf Ahmad
Besides fundamental role in protein synthesis, leucine has metabolic roles as energy substrates, precursors for synthesis of other amino acids and as a modulator of muscle protein synthesis via the insulin-signaling pathway. Leucine concentration in cell and tissue is temporally dynamic as the metabolism of leucine is regulated through multiple enzymes and transporters. Assessment of cell-type specific activities of transporters and enzymes by physical fractionation is extremely challenging. Therefore, a method of reporting leucine dynamics at the cellular level is highly desirable. Given this, we developed a series of genetically encoded nanosensors for real-time in vivo measurement of leucine at cellular level. A leucine binding periplasmic binding protein (LivK) of Escherichia coli K12 was flanked with CFP (cyan fluorescent protein) and YFP (yellow fluorescent protein) at N-terminus and C-terminus, respectively. The constructed nanosensors allowed in vitro determination of fluorescence resonance energy transfer (FRET) changes in a concentration-dependent manner. These sensors were found to be specific to leucine, and stable to pH-changes within a physiological range. Genetically encoded sensors can be targeted to a specific cell type, and allow dynamic measurement of leucine concentration in bacterial and yeast cells.
Source:Biosensors and Bioelectronics, Volume 50
Author(s): Mohd Mohsin , M.Z. Abdin , Lata Nischal , Hemant Kardam , Altaf Ahmad
Besides fundamental role in protein synthesis, leucine has metabolic roles as energy substrates, precursors for synthesis of other amino acids and as a modulator of muscle protein synthesis via the insulin-signaling pathway. Leucine concentration in cell and tissue is temporally dynamic as the metabolism of leucine is regulated through multiple enzymes and transporters. Assessment of cell-type specific activities of transporters and enzymes by physical fractionation is extremely challenging. Therefore, a method of reporting leucine dynamics at the cellular level is highly desirable. Given this, we developed a series of genetically encoded nanosensors for real-time in vivo measurement of leucine at cellular level. A leucine binding periplasmic binding protein (LivK) of Escherichia coli K12 was flanked with CFP (cyan fluorescent protein) and YFP (yellow fluorescent protein) at N-terminus and C-terminus, respectively. The constructed nanosensors allowed in vitro determination of fluorescence resonance energy transfer (FRET) changes in a concentration-dependent manner. These sensors were found to be specific to leucine, and stable to pH-changes within a physiological range. Genetically encoded sensors can be targeted to a specific cell type, and allow dynamic measurement of leucine concentration in bacterial and yeast cells.
Graphical abstract
Label-free electrical quantification of amplified nucleic acids through nanofluidic diodes
23 July 2013,
22:30:57
Publication date: 15 December
2013
Source:Biosensors and Bioelectronics, Volume 50
Author(s): Yifan Liu , Levent Yobas
A label-free method of quantifying nucleic acids in polymerase chain reaction (PCR) is described and could be the basis for miniaturized devices that can amplify and detect target nucleic acids in real time. The method takes advantage of ionic current rectification effect discovered in nanofluidic channels exhibiting a broken symmetry in electrochemical potential – nanofluidic diodes. Nanofluidic diodes are prototyped here on nanopipettes readily pulled from individual thin-walled glass capillaries for a proof of concept demonstration yet the basic concept would be applicable to ionic rectifiers constructed through other means. When a nanopipette modified in the tip region with cationic polyelectrolytes is presented with an unpurified PCR product, the tip surface electrostatically interacts with the amplicons and modulates its ionic rectification direction in response to the intrinsic charge of those adsorbed. Modulations are gradual and correlate well with the mass concentration of the amplicons above 2.5ng/μL, rather than their sizes, with adequate discrimination against the background. Moreover, the tip surface, following a measurement, is regenerated through a layer-by-layer assembly of cationic polyelectrolytes and amplicons. The regenerated tips are capable of measuring distinct mass concentrations without signs of noticeable degradation in sensitivity. Further, the tips are shown capable of reproducing the amplification curve of real-time PCR through sequential steps of surface regeneration and simple electrical readout during the intermediate reaction stages. This suggests that nanopipettes as nanofluidic diodes are at a capacity to be employed for monitoring the PCR progress.
Source:Biosensors and Bioelectronics, Volume 50
Author(s): Yifan Liu , Levent Yobas
A label-free method of quantifying nucleic acids in polymerase chain reaction (PCR) is described and could be the basis for miniaturized devices that can amplify and detect target nucleic acids in real time. The method takes advantage of ionic current rectification effect discovered in nanofluidic channels exhibiting a broken symmetry in electrochemical potential – nanofluidic diodes. Nanofluidic diodes are prototyped here on nanopipettes readily pulled from individual thin-walled glass capillaries for a proof of concept demonstration yet the basic concept would be applicable to ionic rectifiers constructed through other means. When a nanopipette modified in the tip region with cationic polyelectrolytes is presented with an unpurified PCR product, the tip surface electrostatically interacts with the amplicons and modulates its ionic rectification direction in response to the intrinsic charge of those adsorbed. Modulations are gradual and correlate well with the mass concentration of the amplicons above 2.5ng/μL, rather than their sizes, with adequate discrimination against the background. Moreover, the tip surface, following a measurement, is regenerated through a layer-by-layer assembly of cationic polyelectrolytes and amplicons. The regenerated tips are capable of measuring distinct mass concentrations without signs of noticeable degradation in sensitivity. Further, the tips are shown capable of reproducing the amplification curve of real-time PCR through sequential steps of surface regeneration and simple electrical readout during the intermediate reaction stages. This suggests that nanopipettes as nanofluidic diodes are at a capacity to be employed for monitoring the PCR progress.
No comments:
Post a Comment