Biology subjects

Neethirajan, S.

Publications and source records attributed to Neethirajan, S..

10 recordsLinked to original sources

bioRxiv2018

Aptamer-based biosensor for food allergen determination using graphene oxide/gold nanocomposite on a paper-assisted analytical device

The detection of allergens in food are currently conducted by techniques that are time-consuming and complicated which can deter consistent sampling for allergens, which could potentially cause an anaphylactic shock in the consumer by cross-contamination. The need for a technique that is rapid, on-site, cost-effective, disposable, highly sensitive and accurate to identify these molecules urges the development of a point-of-care device. The aim of this work is to develop a microfluidic paper-assisted analytical device (PAD) using hydrophobic channels, set by a wax printer on filter paper, and functionalized gold nanoparticles (AuNP) to help identify the allergens arachin (Ara h 1) for peanuts, {beta}-lactoglobulin ({beta} LG) for milk, and tropomyosin (Pen a 1) for shrimp and other shellfish presence by a colorimetric test. Synthesized AuNP were conjugated with biotinylated aptamers, using the biotin-streptavidin interaction, to make the specific detection of target allergens. Functionalized AuNP are incubated with the sample and are absorbed by graphene oxide (GO), creating GO-AuNP complexes, if the aptamers have not become structured due to conjugation with allergenic proteins. The PAD device is used to filter the resultant mixture which provides superior sensitivity to detect the allergens present down to the nanogram range (allergens were measured from 25 nM - 1000 nM with a LOD of 7.8 nM, 12.4 nM and 6.2 nM for peanut, milk and shrimp allergens respectively), in contrast to the microgram range of commonly used enzymatic immunoassays. The simple color indicator, varying from clear to pink in the presences of allergens allows the readout to be utilized without the need for highly specific equipment or training. Alternatively, the results can be quantified by taking a picture and measuring the color. This presented PAD can provide results in real time and has the potential to become a rapid, low-cost, and accurate portable point-of-care device to avoid cross-reactivity of food-borne allergens.

bioengineering↗

bioRxiv2018

Direct immunosensing of avian influenza A virus in whole blood using hybrid nanocomposites

A sandwich-based electrochemical immunosensor was designed for detection of avian influenza virus (AIV) strains H5N1 and H4N6. This sensor was developed using gold-graphene nanocomposites, immobilized viral antibodies, and CdTe quantum dot electrochemical tagging. The nanocomposites were formed by the simultaneous reduction of a gold salt and graphene using hydroquinone as the reducing agent, thus producing non-spherical gold nanoparticles on graphene sheets. Viral antibodies were immobilized on nanocomposites and CdTe quantum dots through N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide and N-hydroxysuccinimide chemistry. Cyclic voltammetry studies were used to validate the detection of H5N1 surface protein and H4N6 inactivated virus. The immunosensor detected H5 protein in phosphate buffer solution (pH 7.4) with a limit of detection (LOD) of 10 fg/mL and a linear detection range was established for 10 ng/mL to 10 pg/mL. The biosensor detected H4N6 in three parts diluted whole chicken blood with a LOD of 1.28x10-7 hemagglutinating units (HAU). Commercial ELISA testing for H5N1 and H4N6 showed limits of detection of 10 ng/mL and 0.128 HAU, respectively. The sensor showed 106-fold increased detection of H4N6 virus in blood in comparison to its commercial ELISA kit counterpart. The developed immunosensor effectively change the way avian influenza is detected, monitored, and controlled; transforming time-consuming reactive methods, into rapid predictive technology.

bioengineering↗

bioRxiv2017

Rapid Detection of Norovirus Using Paper-based Microfluidic Device

Noroviruses (NoV) are the leading cause of outbreak of acute gastroenteritis worldwide. A substantial effort has been made in the development of analytical devices for rapid and sensitive food safety monitoring via the detection of foodborne bacteria, viruses and parasites. Conventional analytical approaches for noroviruses suffer from some critical weaknesses: labor-intensive, time-consuming, and relatively low sensitivity. In this study, we developed a rapid and highly sensitive biosensor towards point-of-care device for noroviruses based on 6-carboxyfluorescein (6-FAM) labeled aptamer and nanomaterials, multi-walled carbon nanotubes (MWCNTs) and graphene oxide (GO). In an assay, the fluorescence of 6-FAM labeled aptamer was quenched by MWCNTs or GO via fluorescence resonance energy transfer (FRET). In the presence of norovirus, the fluorescence would be recovered due to the release of the 6-FAM labeled aptamer from MWCNTs or GO. An easy-to-make paper-based microfluidic platform made by nitrocellulose membrane was used to conduct the assay. The quantitative detection of norovirus virus-like particles (NoV VLPs) was successfully performed. A linear range of 0-12.9 g/mL with a detection limit of 40 pM and 30 pM was achieved for the MWCNTs and GO based paper sensors, respectively. The results suggested the developed paper-based microfluidic device is simple, cost-effective and holds the potential of rapid in situ visual determination for noroviruses with remarkable sensitivity and specificity, which provides a new way for early identification of NoV and thereby an early intervention for preventing the spread of an outbreak.

bioengineering↗

bioRxiv2017

Self-assembled Star-shaped Chiroplasmonic Gold Nanoparticles for Ultrasensitive Chiro-immunosensor of Viruses

Near field optics and optical tunneling light-matter interaction in the superstructure of chiral nanostructures and semiconductor quantum dots exhibit strong optical rotation activity that may open a new window for chiral-based bioanalytes detection. Herein we report an ultrasensitive, chiro-immunosensor using superstructure of chiral gold nanohybrids (CAu NPs) and quantum dots (QDs). Self-assembling techniques were employed to create asymmetric plasmonic chiral nanostructures for extending the spectral range of circular dichroism (CD) response for obtaining superior plasmonic resonant coupling with the QDs excitonic state; this may help to achieve lower the limit of detection (LOD) values. As a result, the designed probe exhibited avian influenza A (H5N1) viral concentration at picomolar level, a significant improvement in sensitivity in comparison to a non-assembled CAu NPs based chiroassay. The practicability of the proposed sensing system was successfully demonstrated on several virus cultures including, avian influenza A (H4N6) virus, fowl adenovirus and coronavirus in blood samples. The results of our study highlights that exciton-plasmon interaction changes chirality and the self-assembled nanostructures are an efficient strategy for enhancing the sensitivity of plasmonic nanosensors.

bioengineering↗

bioRxiv2017

Paper based microfluidic aptasensor for food safety

Food analysis is requiring rapid, accurate, sensitive and cost-effective methods to monitor and guarantee the safety and quality to fulfill the strict food legislation and consumer demands. In our study, a nano-materials enhanced multipurpose paper based microfluidic aptasensor was demonstrated as a sensing tool for accurate detection of food allergens and food toxins. Graphene oxide (GO) and specific aptamer-functionalized quantum dots (QDs) were employed as probes, the fluorescence quenching and recovering of the QDs caused by the interaction among GO, aptamer-functionalized QDs and the target protein were investigated to quantitatively analyze the target concentration. The homogenous assay was performed on the paper based microfluidic chip, which significantly decreased the sample and reagent consumptions and reduced the assay time. Egg white lysozyme, {beta}-conglutin lupine and food toxins, okadaic acid and brevetoxin standard solutions and spiked food samples were successfully assayed by the presented aptasensor. Dual-target assay was completed within 5 min, and superior sensitivities were achieved when testing the samples with commercial ELISA kits side by side.

bioengineering↗

bioRxiv2017

Chitozyme: First Peroxidase-like Activity of Chitosan for Multiplexed Visual Detection of H2O2, Glucose and Lactate on Paper-based Device

Visual read-out diagnostics tools are promising candidates for field applicable medical devices. Current colorimetric biosensors require introduction of natural enzymes or nanozymes, which has some serious drawbacks for practical applications. Chitosan, a natural polymer, provides safe and efficient compound in medical and pharmaceutical technology. Herein, we report on a simple, cost-efficient, field-portable, environmental friendly and ultra-sensitive multiplex detection platform based on peroxidase-like activity of chitosan in the presence of 3,3,5,5-Tetramethylbenzidine (TMBZ) and H2O2. This straight forward signal amplification strategy was successfully applied to detect H2O2, glucose and lactate with the limit of detection (LOD) of 2.64 pM, 0.104 M and 2.8 nM respectively, represents the lowest LOD of H2O2, glucose and lactate with visual read-out. The chitosan-based assay performance was also retained in complex biological media for glucose and lactate detection. Furthermore, the proposed assay was successfully demonstrated as a paper-based colorimetric biosensor. Most importantly, the simplicity, biocompatibility and sensitivity of the proposed assay will open new doors for instrument free naked eye visual detection of H2O2, glucose and lactate detection.

bioengineering↗

bioRxiv2017

Nanoscale Imaging Approaches To Quantifying The Electrical Properties Of Pathogenic Bacteria

Biofilms are natural, resilient films formed when microorganisms adhere to a surface and form a complex three-dimensional structure that allows them to persist in a wide variety of environments. Readily forming in hospitals and on medical equipment, biofilms are frequent causes of infections and their subsequent complications. Due to the complexity of these structures, systematically studying individual bacterial cells and their interactions with their surrounding environment will provide a deeper understanding of the processes occurring within the biofilm as whole versus bulk population based methods that do not differentiate individual cells or species. Methods based on atomic force microscopy (AFM) are particularly suited to the study of individual cells, but are underutilized for the study of bacterial electrical properties. The ability of electrical currents to impair bacterial attachment is well documented, but to utilize electrical current as an effective antibacterial treatment, it is important to understand the electrical properties of bacteria. Therefore, we used AFM, Kelvin probe force microscopy, and ResiScope to measure the surface potential and conductance of Psuedomonas aeruginosa and methicillin resistance Staphylococcus aureus (MRSA) on gold and stainless steel. This is the first study to directly measure the electrical resistance of single bacterial cells using ResiScope. Our goal was to develop a framework for measuring biological molecules using conductive atomic force microscopy. We found that the average resistance for P. aeruginosa was 135.4{+/-}25.04 G{Omega}, while MRSA had an average of 173.4{+/-}16.28 G{Omega}. Using KPFM, the surface potential of MRSA shifted from -0.304 V to 0.153 V and from -0.280 V to 0.172 V for P. aeruginosa on gold versus stainless steel substrates, respectively. In an attempt to identify a potential charge carrier, peptidoglycan was also measured with the ResiScope module and shown to have a resistance of 105 G{Omega}.

bioengineering↗

bioRxiv2017

Recent Advancement in Biosensors Technology for Animal and Livestock Health Management

The term biosensors encompasses devices that have the potential to quantify physiological, immunological and behavioural responses of livestock and multiple animal species. Novel biosensing methodologies offer highly specialised monitoring devices for the specific measurement of individual and multiple parameters covering an animals physiology as well as monitoring of an animals environment. These devices are not only highly specific and sensitive for the parameters being analysed, but they are also reliable and easy to use, and can accelerate the monitoring process. Novel biosensors in livestock management provide significant benefits and applications in disease detection and isolation, health monitoring and detection of reproductive cycles, as well as monitoring physiological wellbeing of the animal via analysis of the animals environment. With the development of integrated systems and the Internet of Things, the continuously monitoring devices are expected to become affordable. The data generated from integrated livestock monitoring is anticipated to assist farmers and the agricultural industry to improve animal productivity in the future. The data is expected to reduce the impact of the livestock industry on the environment, while at the same time driving the new wave towards the improvements of viable farming techniques. This review focusses on the emerging technological advancements in monitoring of livestock health for detailed, precise information on productivity, as well as physiology and well-being. Biosensors will contribute to the 4th revolution in agriculture by incorporating innovative technologies into cost-effective diagnostic methods that can mitigate the potentially catastrophic effects of infectious outbreaks in farmed animals

bioengineering↗

bioRxiv2017

Amplified visual immunosensor integrated with nanozyme for ultrasensitive detection of avian influenza virus

Nanomaterial-based artificial enzymes or nanozymes exhibits superior properties such as stability, cost effectiveness and ease of preparation in comparison to conventional enzymes. However, the lower catalytic activity of nanozymes limits their sensitivity and thereby practical applications in the bioanalytical field. To overcome this drawback, herein we propose a very simple but highly sensitive, specific and low-cost dual enhanced colorimetric immunoassay for the detection of avian influenza virus A (H5N1) through facile in situ synthesis of gold nanoparticles and their peroxidase-like enzymatic activity. 3,3,5,5-Tetramethylbenzidine (TMBZ) was used as a reducing agent to produce gold nanoparticles (Au NPs) from a viral target-specific antibody-gold ion complex. The developed blue color from the sensing design was further amplified through catalytic activity of Au NPs in presence of TMBZ-hydrogen peroxide (H2O2) complex. The developed dual enhanced colorimetric immunosensor enables the detection of avian influenza virus A (H5N1) with a limit of detection (LOD) of 1.11 pg/mL. Our results further confirms that the developed assay has superior sensitivity than the conventional ELISA method, plasmonic-based bioassay and commercial flu diagnostic kits.

bioengineering↗

bioRxiv2016

Electroceutical disinfection strategies impair the motility of pathogenic Pseudomonas aeruginosa and Escherichia coli

Electrotaxis or galvanotaxis refers to the migration pattern of cells induced in response to electrical potential. Although it has been extensively studied in mammalian cells, electrotaxis has not been explored in detail in bacterial cells; information regarding the impact of current on pathogenic bacteria is severely lacking. Therefore, we designed a series of single and multi-cue experiments to assess the impact of varying currents on bacterial motility dynamics in pathogenic multi-drug resistant (MDR) strains of Pseudomonas aeruginosa and Escherichia coli using a microfluidic platform. Motility plays key roles in bacterial migration and the colonization of surfaces during the formation of biofilms, which are inherently recalcitrant to removal and resistant to traditional disinfection strategies (e.g. antibiotics). Use of the microfluidic platform allows for exposure to current, which can be supplied at a range that is biocidal to bacteria, yet physiologically safe in humans (single cue). This system also allows for multi-cue experiments where acetic acid, a relatively safe compound with anti-fouling/antimicrobial properties, can be combined with current to enhance disinfection. These strategies may offer substantial therapeutic benefits, specifically for the treatment of biofilm infections, such as those found in the wound environment. Furthermore, microfluidic systems have been successfully used to model the unique microfluidic dynamics present in the wound environment, suggesting that these investigations could be extended to more complex biological systems. Our results showed that the application of current in combination with acetic acid has profound inhibitory effects on MDR strains of P. aeruginosa and E. coli, even with brief applications. Specifically, E. coli motility dynamics and cell survival were significantly impaired starting at a concentration of 125 A DC and 0.31% acetic acid, while P. aeruginosa was impaired at 70 A and 0.31% acetic acid. As these strains are relevant wound pathogens, it is likely that this strategy would be effective against similar strains in vivo and could represent a new approach to hasten wound healing.

bioengineering↗