Subramanian Sundarrajan
NUS, Mechanical Engineering, Post-Doc
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Water, among the most valuable natural resources available on earth, is under serious threat as a result of undesirable human activities: for example, marine dumping, atmospheric deposition, domestic, industrial and agricultural... more
Water, among the most valuable natural resources available on earth, is under serious threat as a result of undesirable human activities: for example, marine dumping, atmospheric deposition, domestic, industrial and agricultural practices. Optimizing current methodologies and developing new and effective techniques to remove contaminants from water is the current focus of interest, in order to renew the available water resources. Materials like nanoparticles, polymers, and simple organic compounds, inorganic clay materials in the form of thin film, membrane or powder have been employed for water treatment. Among these materials, membrane technology plays a vital role in removal of contaminants due to its easy handling and high efficiency. Though many materials are under investigation, nanofibers driven membrane are more valuable and reliable. Synthetic methodologies applied over the modification of membrane and its applications in water treatment have been reviewed in this article.
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Myocardial infarction (MI) is characterized by heart-wall thinning, myocyte slippage, and ventricular dilation. The injury to the heart-wall muscle after MI is permanent, as after an abundant cell loss the myocardial tissue lacks the... more
Myocardial infarction (MI) is characterized by heart-wall thinning, myocyte slippage, and ventricular dilation. The injury to the heart-wall muscle after MI is permanent, as after an abundant cell loss the myocardial tissue lacks the intrinsic capability to regenerate. New therapeutics are required for functional improvement and regeneration of the infarcted myocardium, to overcome harmful diagnosis of patients with heart failure, and to overcome the shortage of heart donors. In the past few years, myocardial tissue engineering has emerged as a new and ambitious approach for treating MI. Several left ventricular assist devices and epicardial patches have been developed for MI. These devices and acellular/cellular cardiac patches are employed surgically and sutured to the epicardial surface of the heart, limiting the region of therapeutic benefit. An injectable system offers the potential benefit of minimally invasive release into the myocardium either to restore the injured extracellular matrix or to act as a scaffold for cell delivery. Furthermore, intramyocardial injection of biomaterials and cells has opened new opportunities to explore and also to augment the potentials of this technique to ease morbidity and mortality rates owing to heart failure. This review summarizes the growing body of literature in the field of myocardial tissue engineering, where biomaterial injection, with or without simultaneous cellular delivery, has been pursued to enhance functional and structural outcomes following MI. Additionally, this review also provides a complete outlook on the tissue-engineering therapies presently being used for myocardial regeneration, as well as some perceptivity into the possible issues that may hinder its progress in the future.
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ABSTRACT Activated carbon and fiberglass are widely used in air filtration industry. Nanotechnology field is booming in an exceptionally impressive manner. Nanofibers are one of the unique materials which have one order of magnitude... more
ABSTRACT Activated carbon and fiberglass are widely used in air filtration industry. Nanotechnology field is booming in an exceptionally impressive manner. Nanofibers are one of the unique materials which have one order of magnitude smaller than conventional fibers. The high surface-to-volume ratio, low resistance and enhanced filtration performance make nanofibers an attractive material for many applications such as healthcare, energy and air filtration. Recent advancements in the removal of volatile organic compounds (VOC), nanoparticles and airborne bacterial contaminates in the air are highlighted. The aerosol filtration performances of nanofibers are also presented. The enhanced activity of nanofibers due to the nanosize and their applications such as in protective clothing are highlighted.
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In recent decades, engineered membranes have become a viable separation technology for a wide range of applications in environmental, food and biomedical fields. Membranes are now competitive compared to conventional techniques such as... more
In recent decades, engineered membranes have become a viable separation technology for a wide range of applications in environmental, food and biomedical fields. Membranes are now competitive compared to conventional techniques such as adsorption, ion exchangers and sand filters. The main advantage of membrane technology is the fact that it works without the addition of any chemicals, with relatively high efficiency and low energy consumption with well arranged process conductions. Hence they are widely utilized in biotechnology, food and drink manufacturing, air filtration and medical uses such as dialysis for kidney failure patients. Membranes from nanofibrous materials possess high surface area to volume ratio, fine tunable pore sizes and their ease of preparation prompted both industry and academic researchers to study their use in many applications. In this paper, modern concepts and current research progress on various nanofibrous membranes, such as water and air filtration media, are presented.
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Abstract The paper presents experimental results of electrospray deposition of nanopowder onto microfibers. The process is designed to form fibrous filters with an enhanced collection efficiency in the submicron range by covering the... more
Abstract The paper presents experimental results of electrospray deposition of nanopowder onto microfibers. The process is designed to form fibrous filters with an enhanced collection efficiency in the submicron range by covering the fabric with a catalytic material. ...
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The electrospinning technique has been used to fabricate 1D inorganic-organic composite nanofibers from solutions containing poly(vinyl alcohol) (PVA) and suitable aqueous precursors of nickel and zirconium ions. Upon calcination, nickel... more
The electrospinning technique has been used to fabricate 1D inorganic-organic composite nanofibers from solutions containing poly(vinyl alcohol) (PVA) and suitable aqueous precursors of nickel and zirconium ions. Upon calcination, nickel oxide/zirconia nanofibers retained the original morphological features of as-spun nanofibers. X-ray diffraction was used to identify the crystalline nature of the final product and analytical tools such as Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM) were employed to elucidate the pathway of ceramic phase formation and the systematic evolution of morphological features in the as-spun and calcined fibers. These fibers will find potential applications in biomedical field.
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Heart failure remains the leading cause of death in many industrialized nations owing to the inability of the myocardial tissue to regenerate. The main objective of this work was to develop a cardiac patch that is biocompatible and... more
Heart failure remains the leading cause of death in many industrialized nations owing to the inability of the myocardial tissue to regenerate. The main objective of this work was to develop a cardiac patch that is biocompatible and matches the mechanical properties of the heart muscle for myocardial infarction. The present study was to fabricate poly (glycerol sebacate)/gelatin (PGS/gelatin) core/shell fibers and gelatin fibers alone by electrospinning for cardiac tissue engineering. PGS/gelatin core/shell fibers, PGS used as a core polymer to impart the mechanical properties and gelatin as a shell material to achieve favorable cell adhesion and proliferation. These core/shell fibers were characterized by scanning electron microscopy, contact angle, Fourier transform infrared spectroscopy, and tensile testing. The cell-scaffold interactions were analyzed by cell proliferation, confocal analysis for the expression of marker proteins like actinin, troponin-T, and platelet endothelial cell adhesion molecule, and scanning electron microscopy to analyze cell morphology. Dual immunofluorescent staining was performed to further confirm the cardiogenic differentiation of mesenchymal stem cells by employing mesenchymal stem cell-specific marker protein CD 105 and cardiac-specific marker protein actinin. The results observed that PGS/gelatin core/shell fibers have good potential biocompatibility and mechanical properties for fabricating nanofibrous cardiac patch and would be a prognosticating device for the restoration of myocardium.
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ABSTRACT
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Biologically important pyrazolylpyridines were synthesized in excellent yield by the oxidation of pyrazolyl 1,4-dihydropyridines (pyrazolyl 1,4-DHPs) using tetrapropylammonium perruthenate/N-methylmorpholine-N-oxide (TPAP/NMO) under mild... more
Biologically important pyrazolylpyridines were synthesized in excellent yield by the oxidation of pyrazolyl 1,4-dihydropyridines (pyrazolyl 1,4-DHPs) using tetrapropylammonium perruthenate/N-methylmorpholine-N-oxide (TPAP/NMO) under mild conditions at 0 °C.
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ABSTRACT The increased global demand for low-cost renewable energy sources has motivated scientists and engineers to derive and explore novel methods for converting solar energy into electricity. Among those methods, solar cell is one of... more
ABSTRACT The increased global demand for low-cost renewable energy sources has motivated scientists and engineers to derive and explore novel methods for converting solar energy into electricity. Among those methods, solar cell is one of the clean technologies that has been adopted to produce electricity. However, low efficiency, high cost associated with the preparation of materials and subsequent device fabrication prevented their extensive use to satisfy the growing demand. Hence the technologies based on silicon, organic solar cells, dye-sensitised solar cells or a combination of these two (hybrid solar cells) were developed, where the latter has gathered advantages from both inorganic and organic materials. In this article, the potential of hybrid solar cells over the other types are reviewed. Nanostructured morphologies with high surface area offer significant energy conversion efficiency. In this direction, industrially applicable electrospun nanofibers are more appropriate when compared to the other nano-fabrication technologies. Furthermore the ability of aligned nanofibers to provide higher solar conversion efficiency is discussed. We have also highlighted the fabrication of various nanostructures such as thin films, quantum dots, nanoparticles and composite nanofibers and juxtaposed their morphology with efficiency. (C) 2014 Published by Elsevier Ltd.
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A multicomponent membrane based on polysulfone nanofibers and titanium dioxide nanoparticles is produced by the coupling of electrospinning and electrospraying techniques. The manufactured product can satisfy a number of conflicting... more
A multicomponent membrane based on polysulfone nanofibers and titanium dioxide nanoparticles is produced by the coupling of electrospinning and electrospraying techniques. The manufactured product can satisfy a number of conflicting requirements begetting its technical and functional versatility as well as the reliability of the process. As nanoparticle dispersion is a critical issue in nanoparticle technology, their distribution and morphology have been extensively studied before and after electrospraying, and process optimization has been carried out to obtain nanoparticles uniformly spread over electrospun nanofibers. These membranes have been proved to be a good candidate for supported catalysis due to the photocatalytic activity of TiO(2), tested for degradation of CEPS, a mustard agent simulant. At the same time, an effective improvement in filtering properties in terms of pressure drop has also been studied.
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Myocardial infarction is caused after impairment of heart wall muscle following an immense cell loss and also when the myocardial tissue is lacking the inherent capacity to regenerate for normal functioning of myocardium. An immediate... more
Myocardial infarction is caused after impairment of heart wall muscle following an immense cell loss and also when the myocardial tissue is lacking the inherent capacity to regenerate for normal functioning of myocardium. An immediate challenge in cardiac regeneration is to devise a strategy that leads to a reproducible degree of cardiac differentiation. We have speculated that ex vivo pretreatment of adipose-derived stem cells (ADSCs) using 5-azacytidine and a suitable patterned nanofibrous construct could lead to cardiomyogenic differentiation and results in superior biological and functional effects on cardiac regeneration of infarcted myocardium. Polyglycerol sebacate/gelatin fibers were fabricated by core/shell electrospinning with polyglycerol sebacate as the core material and gelatin as the shell material. Patterning of the core/shell fibers to form orthogonal and looped buckled nanostructures was achieved. Results demonstrated that the buckled fibers showing an orthogonal orientation and looped pattern had a Young's modulus of approximately 3.59 ± 1.58 MPa and 2.07 ± 0.44 MPa, respectively, which was comparable to that of native myocardium. The ADSCs cultured on these scaffolds demonstrated greater expression of the cardiac-specific marker proteins actinin, troponin and connexin 43, as well as characteristic multinucleation as shown by immunocytochemical and morphological analysis, indicating complete cardiogenic differentiation of ADSCs. In the natural milieu, cardiomyogenic differentiation probably involves multiple signaling pathways and we have postulated that a buckled structure combination of chemical treatment and environment-driven strategy induces cardiogenic differentiation of ADSCs. The combination of patterned buckled fibrous structures with stem cell biology may prove to be a productive device for myocardial infarction.
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Research Interests: Biomedical Engineering, Water, Nanofibers, Cell Adhesion, Cell Differentiation, and 14 moreHumans, Porosity, Collagen, Peptides, Osteocalcin, Alkaline phosphatase, Fourier transform infrared spectroscopy, Osteogenesis, Cell Proliferation, Bone Substitutes, Durapatite, Polyesters, Tensile Strength, and Mesenchymal Stromal Cells
The characteristics of tissue engineered scaffolds are major concerns in the quest to fabricate ideal scaffolds for tissue engineering applications. The polymer scaffolds employed for tissue engineering applications should possess... more
The characteristics of tissue engineered scaffolds are major concerns in the quest to fabricate ideal scaffolds for tissue engineering applications. The polymer scaffolds employed for tissue engineering applications should possess multifunctional properties such as biocompatibility, biodegradability and favorable mechanical properties as it comes in direct contact with the body fluids in vivo. Additionally, the polymer system should also possess biomimetic architecture and should support stem cell adhesion, proliferation and differentiation. As the progress in polymer technology continues, polymeric biomaterials have taken characteristics more closely related to that desired for tissue engineering and clinical needs. Stimuli responsive polymers also termed as smart biomaterials respond to stimuli such as pH, temperature, enzyme, antigen, glucose and electrical stimuli that are inherently present in living systems. This review highlights the exciting advancements in these polymeric systems that relate to biological and tissue engineering applications. Additionally, several aspects of technology namely scaffold fabrication methods and surface modifications to confer biological functionality to the polymers have also been discussed. The ultimate objective is to emphasize on these underutilized adaptive behaviors of the polymers so that novel applications and new generations of smart polymeric materials can be realized for biomedical and tissue engineering applications.
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ABSTRACT The paper presents investigations of a method of the production of non-woven polymer fabrics with incorporated metal oxide nanoparticles based on electrospinning and electrospraying. Two main configurations of... more
ABSTRACT The paper presents investigations of a method of the production of non-woven polymer fabrics with incorporated metal oxide nanoparticles based on electrospinning and electrospraying. Two main configurations of electrospraying/electrospinning systems have been tested: two-step process of electrospinning of polymer solution followed by electrospraying of nanoparticle suspension, and simultaneous electrospinning of polymer solution and electrospraying of nanoparticle suspension. By this method TiO2, MgO, or Al2O3 nanoparticles of the size from 20 to 100 nm were deposited onto electrospun PVC nanofibers.
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The present scenario is that neutral or uncharged polymers are electrospun first followed by surface modification to introduce the functional groups onto the nanofibers surface. These groups improve the adhesion between the nanofibers and... more
The present scenario is that neutral or uncharged polymers are electrospun first followed by surface modification to introduce the functional groups onto the nanofibers surface. These groups improve the adhesion between the nanofibers and materials to be coated. The surface modification involves significant steps to get desired functional groups on the nanofibers surface and also time consuming. This paper deals with one step fabrication of nanofibers with hydroxyl functional groups. Nanofibers were fabricated by electrospinning of poly(ethylene terephthalate) (PET) with cellulose acetate (CA) or cellulose (C). Deposition of various metal oxide nanoparticles on these nanofiber surfaces was carried out using liquid phase deposition (LPD) and electrospraying techniques. Distribution of the nanoparticles and aggregation minimization were obtained by optimization of electrospraying technique. The nucleation density and the morphology of coated nanoparticles by LPD technique on PET surface were lower amount, whereas they are higher on PET/CA and PET/C blended surface, due to hydroxyl functional groups on the blended nanofiber surface, which is a novel. This study is helpful to understand about the complimentary information of the process based on the adoption of these two techniques. The characterizations of these nanofibers were carried out by using SEM, contact angle analysis, tensile, porosity measurements, and EDAX analysis. These membranes find potential applications as filter media in protective clothing and air filter applications.
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The combination of electrospinning and electrospraying techniques for the deposition of inorganic nanoparticles over polymeric nanofibers to create novel multifunctional nanomaterials has been carried out. The combination of these two... more
The combination of electrospinning and electrospraying techniques for the deposition of inorganic nanoparticles over polymeric nanofibers to create novel multifunctional nanomaterials has been carried out. The combination of these two techniques is essential because by conventional mixing of nanoparticles with polymers and then electrospinning resulted in nanoparticles covered by the polymer and thereby nanoparticles are unavailable for the catalysis applications. This technique is also useful to exploit the application of nanofibers for various applications. Based on the materials chosen, this technology can be applied to various applications such as protective suits, biological applications, catalysis, etc. Here the challenging task is to avoid the aggregation of nanoparticles and improve the distribution of nanoparticles over nanofibers. This was achieved by optimizing various electrospraying parameters (such as feed rate, voltage) and the dispersion properties. The dispersion in solution has been achieved by using a surfactant and optimization of silane modifier concentration and sonication time. Hydrolysis of paraoxon, a nerve agent stimulant was tested for these nanocomposite membranes by UV analysis. Decrease in absorbance was observed for these membranes with time suggesting the detoxification of nerve agent. Hence these membranes can be used as filter media in protective clothing (to detoxify chemical warfare agents to replace the existing charcoal based protection suits wherein the warfare agents are not detoxified rather adsorbed) and air filter applications.
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Currently, electrospun nanofibrous membrane (ENM) is classified as a microfiltration (MF) membrane, which upon further modification is used for nanofiltration (NF) applications. The objective of this study was to investigate the... more
Currently, electrospun nanofibrous membrane (ENM) is classified as a microfiltration (MF) membrane, which upon further modification is used for nanofiltration (NF) applications. The objective of this study was to investigate the suitability of ENM for water treatment ...
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Every year, millions of people suffer from dermal wounds caused by heat, fire, chemicals, electricity, ultraviolet radiation or disease. Tissue engineering and nanotechnology have enabled the engineering of nanostructured materials to... more
Every year, millions of people suffer from dermal wounds caused by heat, fire, chemicals, electricity, ultraviolet radiation or disease. Tissue engineering and nanotechnology have enabled the engineering of nanostructured materials to meet the current challenges in skin treatments owing to such rising occurrences of accidental damages, skin diseases and defects. The abundance and accessibility of adipose derived stem cells (ADSCs) may prove to be novel cell therapeutics for skin regeneration. The nanofibrous PVA/gelatin/azide scaffolds were then fabricated by electrospinning using water as solvent and allowed to undergo click reaction. The scaffolds were characterized by SEM, contact angle and FTIR. The cell-scaffold interactions were analyzed by cell proliferation and the results observed that the rate of cell proliferation was significantly increased (P ≤ 0.05) on PVA/gelatin/azide scaffolds compared to PVA/gelatin nanofibers. In the present study, manipulating the biochemical cues by the addition of an induction medium, in combination with environmental and physical factors of the culture substrate by functionalizing with click moieties, we were able to drive ADSCs into epidermal lineage with the development of epidermis-like structures, was further confirmed by the expression of early and intermediate epidermal differentiation markers like keratin and filaggrin. This study not only provides an insight into the design of a site-specific niche-like microenvironment for stem cell lineage commitment, but also sheds light on the therapeutic application of an alternative cell source-ADSCs, for wound healing and skin tissue reconstitution.
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