Venkatesan Renugopalakrishnan - Academia.edu (original) (raw)
Papers by Venkatesan Renugopalakrishnan
International Journal of Molecular Sciences
In nature, solar energy is captured by different types of light harvesting protein–pigment comple... more In nature, solar energy is captured by different types of light harvesting protein–pigment complexes. Two of these photoactivatable proteins are bacteriorhodopsin (bR), which utilizes a retinal moiety to function as a proton pump, and photosystem I (PSI), which uses a chlorophyll antenna to catalyze unidirectional electron transfer. Both PSI and bR are well characterized biochemically and have been integrated into solar photovoltaic (PV) devices built from sustainable materials. Both PSI and bR are some of the best performing photosensitizers in the bio-sensitized PV field, yet relatively little attention has been devoted to the development of more sustainable, biocompatible alternative counter electrodes and electrolytes for bio-sensitized solar cells. Careful selection of the electrolyte and counter electrode components is critical to designing bio-sensitized solar cells with more sustainable materials and improved device performance. This work explores the use of poly (3,4-ethyle...
The aquaporin superfamily of hydrophobic integral membrane proteins constitutes water channels es... more The aquaporin superfamily of hydrophobic integral membrane proteins constitutes water channels essential to the movement of water across the cell membrane, maintaining homeostatic equilibrium. During the passage of water between the extracellular and intracellular sides of the cell, aquaporins act as ultra-sensitive filters. Owing to their hydrophobic nature, aquaporins self-assemble in phospholipids. If a proper choice of lipids is made then the aquaporin biomimetic membrane can be used in the design of an artificial kidney. In combination with graphene, the aquaporin biomimetic membrane finds practical application in desalination and water recycling using mostly <i>Escherichia coli</i> AqpZ. Recently, human aquaporin 1 has emerged as an important biomarker in renal cell carcinoma. At present, the ultra-sensitive sensing of renal cell carcinoma is cumbersome. Hence, we discuss the use of epitopes from monoclonal antibodies as a probe for a point-of-care device for sensi...
MRS Communications, 2020
<jats:p> <jats:fig position="anchor"> <jats:graphic xmlns:xlink="ht... more <jats:p> <jats:fig position="anchor"> <jats:graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" mimetype="image" xlink:href="S2159685920000750_figAb.png" /> </jats:fig> </jats:p>
Bulletin of the American Physical Society, 2020
The aquaporin superfamily of hydrophobic integral membrane proteins constitutes water channels es... more The aquaporin superfamily of hydrophobic integral membrane proteins constitutes water channels essential to the movement of water across the cell membrane, maintaining homeostatic equilibrium. During the passage of water between the extracellular and intracellular sides of the cell, aquaporins act as ultra-sensitive filters. Owing to their hydrophobic nature, aquaporins self-assemble in phospholipids. If a proper choice of lipids is made then the aquaporin biomimetic membrane can be used in the design of an artificial kidney. In combination with graphene, the aquaporin biomimetic membrane finds practical application in desalination and water recycling using mostly <i>Escherichia coli</i> AqpZ. Recently, human aquaporin 1 has emerged as an important biomarker in renal cell carcinoma. At present, the ultra-sensitive sensing of renal cell carcinoma is cumbersome. Hence, we discuss the use of epitopes from monoclonal antibodies as a probe for a point-of-care device for sensing renal cell carcinoma. This device works by immobilizing the antibody on the surface of a single-layer graphene, that is, as a microfluidic device for sensing renal cell carcinoma.
MRS Communications, 2018
Nanomaterials have been proposed as key components in biosensing, imaging, and drug-delivery sinc... more Nanomaterials have been proposed as key components in biosensing, imaging, and drug-delivery since they offer distinctive advantages over conventional approaches. The unique chemical and physical properties of graphene make it possible to functionalize and develop protein transducers, therapeutic delivery vehicles, and microbial diagnostics. In this study we evaluate reduced graphene oxide (rGO) as a potential nanomaterial for quantification of microRNAs including their structural differentiation in vitro in solution and inside intact cells. Our results provide evidence for the potential use of graphene nanomaterials as a platform for developing devices that can be used for microRNA quantitation as biomarkers for clinical applications.
Biosensors and Bioelectronics, 2019
Existing at the interface of biology and electronics, living cells have been in use as biorecogni... more Existing at the interface of biology and electronics, living cells have been in use as biorecognition elements (bioreceptors) in biosensors since the early 1970s. They are an interesting choice of bioreceptors as they allow flexibility in determining the sensing strategy, are cheaper than purified enzymes and antibodies and make the fabrication relatively simple and cost-effective. And with advances in the field of synthetic biology, microfluidics and lithography, many exciting developments have been made in the design of cell-based biosensors in the last about five years. 3D cell culture systems integrated with electrodes are now providing new insights into disease pathogenesis and physiology, while cardiomyocyte-integrated microelectrode array (MEA) technology is set to be standardized for the assessment of druginduced cardiac toxicity. From cell microarrays for high-throughput applications to plasmonic devices for anti-microbial susceptibility testing and advent of microbial fuel cell biosensors, cellbased biosensors have evolved from being mere tools for detection of specific analytes to multiparametric devices for real time monitoring and assessment. However, despite these advancements, challenges such as regeneration and storage life, heterogeneity in cell populations, high interference and high costs due to accessory instrumentation need to be addressed before the full potential of cell-based biosensors can be realized at a larger scale. This review summarizes results of the studies that have been conducted in the last five years toward the fabrication of cell-based biosensors for different applications with a comprehensive discussion on the challenges, future trends, and potential inputs needed for improving them.
MRS Communications, 2018
The inefficiencies of the current pipeline from discovery to clinical approval of drugs demand a ... more The inefficiencies of the current pipeline from discovery to clinical approval of drugs demand a surrogate method to indicate adverse drug reactions, e.g. liver damage. Organ-on-chip (OOC) models would be an ideal, rapid, and human-specific alternate, which would render animal testing obsolete. The ground-breaking ability of OOCs and Multi-OOC constructs is the accurate simulation of the in vivo conditions of human organs leading to precise drug screens for cytotoxicity and/or drug efficacy at a faster pace and lesser cost. Here we discuss the innovation, architecture, and the progress of OOCs towards human body-on-a-chip.
Condensed Matter, 2018
We study excitations and quantum optical properties of hybrid networks made up of metal nanoparti... more We study excitations and quantum optical properties of hybrid networks made up of metal nanoparticles, semiconductor quantum dots and molecules. Such processes can be used for the localization and the guiding of the electromagnetic field. Localized modes occurring in these networks and the generation of confined fields are also connected to the enhancement of Raman-scattering occurring in these systems. We review some recent theoretical and computational studies of optical properties in hybrid nano-systems to gain control of light-matter interactions at the quantum level for efficient energy transport and sensing applications.
Biophysical Journal, 2019
Royal Society Open Science, 2018
We herein report a simple chemical route to prepare Au–Ag and Ag–Au core–shell bimetallic nanostr... more We herein report a simple chemical route to prepare Au–Ag and Ag–Au core–shell bimetallic nanostructures by reduction of two kinds of noble metal ions in the presence of a water-soluble polymer such as poly(vinyl alcohol) (PVA). PVA was intentionally chosen as it can play a dual role of a supporting matrix as well as stabilizer. The simultaneous reduction of metal ions leads to an alloy type of structure. Ag(c)–Au(s) core–shell structures display tendency to form prismatic nanostructures in conjunction with nanocubes while Au(c)–Ag(s) core–shell structures show formation of merely nanocubes. Although UV–visible spectroscopy and X-ray photoelectron spectroscopy analyses of the samples typically suggest the formation of both Ag(c)–Au(s) and Au(c)–Ag(s) bimetallic nanostructures, the definitive evidence comes from high-resolution transmission electron microscopy–high-angle annular dark field elemental mapping in the case of Au(c)–Ag(s) nanomorphs only. The resultant nanocomposite mater...
Interface focus, Jan 6, 2018
The aquaporin superfamily of hydrophobic integral membrane proteins constitutes water channels es... more The aquaporin superfamily of hydrophobic integral membrane proteins constitutes water channels essential to the movement of water across the cell membrane, maintaining homeostatic equilibrium. During the passage of water between the extracellular and intracellular sides of the cell, aquaporins act as ultra-sensitive filters. Owing to their hydrophobic nature, aquaporins self-assemble in phospholipids. If a proper choice of lipids is made then the aquaporin biomimetic membrane can be used in the design of an artificial kidney. In combination with graphene, the aquaporin biomimetic membrane finds practical application in desalination and water recycling using mostly AqpZ. Recently, human aquaporin 1 has emerged as an important biomarker in renal cell carcinoma. At present, the ultra-sensitive sensing of renal cell carcinoma is cumbersome. Hence, we discuss the use of epitopes from monoclonal antibodies as a probe for a point-of-care device for sensing renal cell carcinoma. This device...
Journal of Materials Research, 2017
This article features the recent developments in fluorographene (FG) and its other functional for... more This article features the recent developments in fluorographene (FG) and its other functional forms such as fluorographene oxide—their synthesis, fluorination, defluorination, and applications. FG is identified as an important functional derivative of graphene, and FG’s multifunctionalities make it as an ideal candidate for diverse fields, say from photovoltaic to bio-medical diagnosis, imaging, sensing, and therapy. Here the possibilities of FG as a biomedical sensing platform is discussed in detail and the potentials of FG based electrochemical and conductometric sensing platforms are unraveled. The importance of fluorine control as well as the other key factors need to be considered while choosing FG based bio-sensing platforms are also discussed.
Journal of Materials Research, 2015
Bionanotechnology
... Generally organic materials (molecular crystals and polymers) are composed of weakly interact... more ... Generally organic materials (molecular crystals and polymers) are composed of weakly interacting molecules ... losses due to scattering and slow, of the order of minutes, photorefractive dynamics. ... and it is widely accepted that light could impose molecular reorientation through ...
MRS Proceedings, 2015
Using all-atom molecular dynamics simulations in water environment, it was possible to demonstrat... more Using all-atom molecular dynamics simulations in water environment, it was possible to demonstrate spontaneous and tight encapsulation of glucose oxidase (GOx) dimer by graphene 7 nm x 7 nm sheets linked together by linkers of different width and forming a flower-like or cross-like shapes. The partially overlapping graphene sheets compacted the structure of GOx dimer, bringing the monomers much closer to one another. We found that the most complete wrapping of the enzyme was achieved for the cross-like graphene. Encapsulation can be a useful way to obtain a large contact surface. However, an exceptionally tight binding by the graphene can also influence the positions of amino acids in the enzyme binding site resulting in less efficient catalytic reaction. Furthermore, such extensive encapsulation could block the access of the substrate to the active site of the enzyme. Contrary, a partial encapsulation by graphene using nano-sheets caused only small distortions of GOx structure while the contact surface with graphene was high.
MRS Proceedings, 2015
ABSTRACTThe need for improved medical sensors based on lab-on-a-chip technologies has increased s... more ABSTRACTThe need for improved medical sensors based on lab-on-a-chip technologies has increased significantly because of the dramatic growth in the number of people with chronic diseases and the associated costs for their healthcare. Development and initial results of a hybrid plastic microfluidic device with an integrated graphene-protein biosensor chip for use in point-of-care (POC) is described. The initial prototype is a glucometer that uses optimized glucose oxidase bound to a graphene field effect sensor. Technologies required for development of the prototype include modification of the glucose oxidase for improved performance by protein engineering, methods to bind the enzyme to the graphene attached to the silicon oxide surface of sensor chip, and integration into a thermoplastic microfluidic device. Initial results indicate the prototype glucometer can measure glucose concentrations from low physiological levels to molar concentrations.
Life Sciences, 1986
The FT-IR (Fourier Transform Infrared) Spectrum of [Met 5]-enkephalinamide in aqueous solution sh... more The FT-IR (Fourier Transform Infrared) Spectrum of [Met 5]-enkephalinamide in aqueous solution shows the presence of both the beta-turn and beta-sheet conformations. The beta-turn and beta-sheet conformations of enkephalins have been proposed to play a role in receptor selectivity. Addition of ethanol alters these secondary structural features and hence the effect of ethanol on ligand-receptor interaction may be mediated primarily through conformational changes of the ligand rather than those of the receptor.
International Journal of Molecular Sciences
In nature, solar energy is captured by different types of light harvesting protein–pigment comple... more In nature, solar energy is captured by different types of light harvesting protein–pigment complexes. Two of these photoactivatable proteins are bacteriorhodopsin (bR), which utilizes a retinal moiety to function as a proton pump, and photosystem I (PSI), which uses a chlorophyll antenna to catalyze unidirectional electron transfer. Both PSI and bR are well characterized biochemically and have been integrated into solar photovoltaic (PV) devices built from sustainable materials. Both PSI and bR are some of the best performing photosensitizers in the bio-sensitized PV field, yet relatively little attention has been devoted to the development of more sustainable, biocompatible alternative counter electrodes and electrolytes for bio-sensitized solar cells. Careful selection of the electrolyte and counter electrode components is critical to designing bio-sensitized solar cells with more sustainable materials and improved device performance. This work explores the use of poly (3,4-ethyle...
The aquaporin superfamily of hydrophobic integral membrane proteins constitutes water channels es... more The aquaporin superfamily of hydrophobic integral membrane proteins constitutes water channels essential to the movement of water across the cell membrane, maintaining homeostatic equilibrium. During the passage of water between the extracellular and intracellular sides of the cell, aquaporins act as ultra-sensitive filters. Owing to their hydrophobic nature, aquaporins self-assemble in phospholipids. If a proper choice of lipids is made then the aquaporin biomimetic membrane can be used in the design of an artificial kidney. In combination with graphene, the aquaporin biomimetic membrane finds practical application in desalination and water recycling using mostly <i>Escherichia coli</i> AqpZ. Recently, human aquaporin 1 has emerged as an important biomarker in renal cell carcinoma. At present, the ultra-sensitive sensing of renal cell carcinoma is cumbersome. Hence, we discuss the use of epitopes from monoclonal antibodies as a probe for a point-of-care device for sensi...
MRS Communications, 2020
<jats:p> <jats:fig position="anchor"> <jats:graphic xmlns:xlink="ht... more <jats:p> <jats:fig position="anchor"> <jats:graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" mimetype="image" xlink:href="S2159685920000750_figAb.png" /> </jats:fig> </jats:p>
Bulletin of the American Physical Society, 2020
The aquaporin superfamily of hydrophobic integral membrane proteins constitutes water channels es... more The aquaporin superfamily of hydrophobic integral membrane proteins constitutes water channels essential to the movement of water across the cell membrane, maintaining homeostatic equilibrium. During the passage of water between the extracellular and intracellular sides of the cell, aquaporins act as ultra-sensitive filters. Owing to their hydrophobic nature, aquaporins self-assemble in phospholipids. If a proper choice of lipids is made then the aquaporin biomimetic membrane can be used in the design of an artificial kidney. In combination with graphene, the aquaporin biomimetic membrane finds practical application in desalination and water recycling using mostly <i>Escherichia coli</i> AqpZ. Recently, human aquaporin 1 has emerged as an important biomarker in renal cell carcinoma. At present, the ultra-sensitive sensing of renal cell carcinoma is cumbersome. Hence, we discuss the use of epitopes from monoclonal antibodies as a probe for a point-of-care device for sensing renal cell carcinoma. This device works by immobilizing the antibody on the surface of a single-layer graphene, that is, as a microfluidic device for sensing renal cell carcinoma.
MRS Communications, 2018
Nanomaterials have been proposed as key components in biosensing, imaging, and drug-delivery sinc... more Nanomaterials have been proposed as key components in biosensing, imaging, and drug-delivery since they offer distinctive advantages over conventional approaches. The unique chemical and physical properties of graphene make it possible to functionalize and develop protein transducers, therapeutic delivery vehicles, and microbial diagnostics. In this study we evaluate reduced graphene oxide (rGO) as a potential nanomaterial for quantification of microRNAs including their structural differentiation in vitro in solution and inside intact cells. Our results provide evidence for the potential use of graphene nanomaterials as a platform for developing devices that can be used for microRNA quantitation as biomarkers for clinical applications.
Biosensors and Bioelectronics, 2019
Existing at the interface of biology and electronics, living cells have been in use as biorecogni... more Existing at the interface of biology and electronics, living cells have been in use as biorecognition elements (bioreceptors) in biosensors since the early 1970s. They are an interesting choice of bioreceptors as they allow flexibility in determining the sensing strategy, are cheaper than purified enzymes and antibodies and make the fabrication relatively simple and cost-effective. And with advances in the field of synthetic biology, microfluidics and lithography, many exciting developments have been made in the design of cell-based biosensors in the last about five years. 3D cell culture systems integrated with electrodes are now providing new insights into disease pathogenesis and physiology, while cardiomyocyte-integrated microelectrode array (MEA) technology is set to be standardized for the assessment of druginduced cardiac toxicity. From cell microarrays for high-throughput applications to plasmonic devices for anti-microbial susceptibility testing and advent of microbial fuel cell biosensors, cellbased biosensors have evolved from being mere tools for detection of specific analytes to multiparametric devices for real time monitoring and assessment. However, despite these advancements, challenges such as regeneration and storage life, heterogeneity in cell populations, high interference and high costs due to accessory instrumentation need to be addressed before the full potential of cell-based biosensors can be realized at a larger scale. This review summarizes results of the studies that have been conducted in the last five years toward the fabrication of cell-based biosensors for different applications with a comprehensive discussion on the challenges, future trends, and potential inputs needed for improving them.
MRS Communications, 2018
The inefficiencies of the current pipeline from discovery to clinical approval of drugs demand a ... more The inefficiencies of the current pipeline from discovery to clinical approval of drugs demand a surrogate method to indicate adverse drug reactions, e.g. liver damage. Organ-on-chip (OOC) models would be an ideal, rapid, and human-specific alternate, which would render animal testing obsolete. The ground-breaking ability of OOCs and Multi-OOC constructs is the accurate simulation of the in vivo conditions of human organs leading to precise drug screens for cytotoxicity and/or drug efficacy at a faster pace and lesser cost. Here we discuss the innovation, architecture, and the progress of OOCs towards human body-on-a-chip.
Condensed Matter, 2018
We study excitations and quantum optical properties of hybrid networks made up of metal nanoparti... more We study excitations and quantum optical properties of hybrid networks made up of metal nanoparticles, semiconductor quantum dots and molecules. Such processes can be used for the localization and the guiding of the electromagnetic field. Localized modes occurring in these networks and the generation of confined fields are also connected to the enhancement of Raman-scattering occurring in these systems. We review some recent theoretical and computational studies of optical properties in hybrid nano-systems to gain control of light-matter interactions at the quantum level for efficient energy transport and sensing applications.
Biophysical Journal, 2019
Royal Society Open Science, 2018
We herein report a simple chemical route to prepare Au–Ag and Ag–Au core–shell bimetallic nanostr... more We herein report a simple chemical route to prepare Au–Ag and Ag–Au core–shell bimetallic nanostructures by reduction of two kinds of noble metal ions in the presence of a water-soluble polymer such as poly(vinyl alcohol) (PVA). PVA was intentionally chosen as it can play a dual role of a supporting matrix as well as stabilizer. The simultaneous reduction of metal ions leads to an alloy type of structure. Ag(c)–Au(s) core–shell structures display tendency to form prismatic nanostructures in conjunction with nanocubes while Au(c)–Ag(s) core–shell structures show formation of merely nanocubes. Although UV–visible spectroscopy and X-ray photoelectron spectroscopy analyses of the samples typically suggest the formation of both Ag(c)–Au(s) and Au(c)–Ag(s) bimetallic nanostructures, the definitive evidence comes from high-resolution transmission electron microscopy–high-angle annular dark field elemental mapping in the case of Au(c)–Ag(s) nanomorphs only. The resultant nanocomposite mater...
Interface focus, Jan 6, 2018
The aquaporin superfamily of hydrophobic integral membrane proteins constitutes water channels es... more The aquaporin superfamily of hydrophobic integral membrane proteins constitutes water channels essential to the movement of water across the cell membrane, maintaining homeostatic equilibrium. During the passage of water between the extracellular and intracellular sides of the cell, aquaporins act as ultra-sensitive filters. Owing to their hydrophobic nature, aquaporins self-assemble in phospholipids. If a proper choice of lipids is made then the aquaporin biomimetic membrane can be used in the design of an artificial kidney. In combination with graphene, the aquaporin biomimetic membrane finds practical application in desalination and water recycling using mostly AqpZ. Recently, human aquaporin 1 has emerged as an important biomarker in renal cell carcinoma. At present, the ultra-sensitive sensing of renal cell carcinoma is cumbersome. Hence, we discuss the use of epitopes from monoclonal antibodies as a probe for a point-of-care device for sensing renal cell carcinoma. This device...
Journal of Materials Research, 2017
This article features the recent developments in fluorographene (FG) and its other functional for... more This article features the recent developments in fluorographene (FG) and its other functional forms such as fluorographene oxide—their synthesis, fluorination, defluorination, and applications. FG is identified as an important functional derivative of graphene, and FG’s multifunctionalities make it as an ideal candidate for diverse fields, say from photovoltaic to bio-medical diagnosis, imaging, sensing, and therapy. Here the possibilities of FG as a biomedical sensing platform is discussed in detail and the potentials of FG based electrochemical and conductometric sensing platforms are unraveled. The importance of fluorine control as well as the other key factors need to be considered while choosing FG based bio-sensing platforms are also discussed.
Journal of Materials Research, 2015
Bionanotechnology
... Generally organic materials (molecular crystals and polymers) are composed of weakly interact... more ... Generally organic materials (molecular crystals and polymers) are composed of weakly interacting molecules ... losses due to scattering and slow, of the order of minutes, photorefractive dynamics. ... and it is widely accepted that light could impose molecular reorientation through ...
MRS Proceedings, 2015
Using all-atom molecular dynamics simulations in water environment, it was possible to demonstrat... more Using all-atom molecular dynamics simulations in water environment, it was possible to demonstrate spontaneous and tight encapsulation of glucose oxidase (GOx) dimer by graphene 7 nm x 7 nm sheets linked together by linkers of different width and forming a flower-like or cross-like shapes. The partially overlapping graphene sheets compacted the structure of GOx dimer, bringing the monomers much closer to one another. We found that the most complete wrapping of the enzyme was achieved for the cross-like graphene. Encapsulation can be a useful way to obtain a large contact surface. However, an exceptionally tight binding by the graphene can also influence the positions of amino acids in the enzyme binding site resulting in less efficient catalytic reaction. Furthermore, such extensive encapsulation could block the access of the substrate to the active site of the enzyme. Contrary, a partial encapsulation by graphene using nano-sheets caused only small distortions of GOx structure while the contact surface with graphene was high.
MRS Proceedings, 2015
ABSTRACTThe need for improved medical sensors based on lab-on-a-chip technologies has increased s... more ABSTRACTThe need for improved medical sensors based on lab-on-a-chip technologies has increased significantly because of the dramatic growth in the number of people with chronic diseases and the associated costs for their healthcare. Development and initial results of a hybrid plastic microfluidic device with an integrated graphene-protein biosensor chip for use in point-of-care (POC) is described. The initial prototype is a glucometer that uses optimized glucose oxidase bound to a graphene field effect sensor. Technologies required for development of the prototype include modification of the glucose oxidase for improved performance by protein engineering, methods to bind the enzyme to the graphene attached to the silicon oxide surface of sensor chip, and integration into a thermoplastic microfluidic device. Initial results indicate the prototype glucometer can measure glucose concentrations from low physiological levels to molar concentrations.
Life Sciences, 1986
The FT-IR (Fourier Transform Infrared) Spectrum of [Met 5]-enkephalinamide in aqueous solution sh... more The FT-IR (Fourier Transform Infrared) Spectrum of [Met 5]-enkephalinamide in aqueous solution shows the presence of both the beta-turn and beta-sheet conformations. The beta-turn and beta-sheet conformations of enkephalins have been proposed to play a role in receptor selectivity. Addition of ethanol alters these secondary structural features and hence the effect of ethanol on ligand-receptor interaction may be mediated primarily through conformational changes of the ligand rather than those of the receptor.