2,065 research outputs found
Point-of-Need DNA Testing for Detection of Foodborne Pathogenic Bacteria
Foodborne pathogenic bacteria present a crucial food safety issue. Conventional diagnostic methods are time-consuming and can be only performed on previously produced food. The advancing field of point-of-need diagnostic devices integrating molecular methods, biosensors, microfluidics, and nanomaterials offers new avenues for swift, low-cost detection of pathogens with high sensitivity and specificity. These analyses and screening of food items can be performed during all phases of production. This review presents major developments achieved in recent years in point-of-need diagnostics in land-based sector and sheds light on current challenges in achieving wider acceptance of portable devices in the food industry. Particular emphasis is placed on methods for testing nucleic acids, protocols for portable nucleic acid extraction and amplification, as well as on the means for low-cost detection and read-out signal amplification
Trends of biosensing: plasmonics through miniaturization and quantum sensing
Despite being extremely old concepts, plasmonics and surface plasmon
resonance-based biosensors have been increasingly popular in the recent two
decades due to the growing interest in nanooptics and are now of relevant
significance in regards to applications associated with human health.
Plasmonics integration into point-of-care devices for health surveillance has
enabled significant levels of sensitivity and limit of detection to be achieved
and has encouraged the expansion of the fields of study and market niches
devoted to the creation of quick and incredibly sensitive label-free detection.
The trend reflects in wearable plasmonic sensor development as well as
point-of-care applications for widespread applications, demonstrating the
potential impact of the new generation of plasmonic biosensors on human
well-being through the concepts of personalized medicine and global health. In
this context, the aim here is to discuss the potential, limitations, and
opportunities for improvement that have arisen as a result of the integration
of plasmonics into microsystems and lab-on-chip over the past five years.
Recent applications of plasmonic biosensors in microsystems and sensor
performance are analyzed. The final analysis focuses on the integration of
microfluidics and lab-on-a-chip with quantum plasmonics technology prospecting
it as a promising solution for chemical and biological sensing. Here it is
underlined how the research in the field of quantum plasmonic sensing for
biological applications has flourished over the past decade with the aim to
overcome the limits given by quantum fluctuations and noise. The significant
advances in nanophotonics, plasmonics and microsystems used to create
increasingly effective biosensors would continue to benefit this field if
harnessed properly
Silicon nanowire field-effect transistors for the detection of proteins
In this dissertation I present results on our efforts to increase the sensitivity and selectivity of silicon nanowire ion-sensitive field-effect transistors for the detection of biomarkers, as well as a novel method for wireless power transfer based on metamaterial rectennas for their potential use as implantable sensors. The sensing scheme is based on changes in the conductance of the semiconducting nanowires upon binding of charged entities to the surface, which induces a field-effect. Monitoring the differential conductance thus provides information of the selective binding of biological molecules of interest to previously covalently linked counterparts on the nanowire surface.
In order to improve on the performance of the nanowire sensing, we devised and fabricated a nanowire Wheatstone bridge, which allows canceling out of signal drift due to thermal fluctuations and dynamics of fluid flow. We showed that balancing the bridge significantly improves the signal-to-noise ratio. Further, we demonstrated the sensing of novel melanoma biomarker TROY at clinically relevant concentrations and distinguished it from nonspecific binding by comparing the reaction kinetics. For increased sensitivity, an amplification method was employed using an enzyme which catalyzes a signal-generating reaction by changing the redox potential of a redox pair. In addition, we investigated the electric double layer, which forms around charges in an electrolytic solution. It causes electrostatic screening of the proteins of interest, which puts a fundamental limitation on the biomarker detection in solutions with high salt concentrations, such as blood. We solved the coupled Nernst-Planck and Poisson equations for the electrolyte under influence of an oscillating electric field and discovered oscillations of the counterion concentration at a characteristic frequency.
In addition to exploring different methods for improved sensing capabilities, we studied an innovative method to supply power to implantable biosensors wirelessly, eliminating the need for batteries. A metamaterial split ring resonator is integrated with a rectifying circuit for efficient conversion of microwave radiation to direct electrical power. We studied the near-field behavior of this rectenna with respect to distance, polarization, power, and frequency. Using a 100 mW microwave power source, we demonstrated operating a simple silicon nanowire pH sensor with light indicator
Optical Fiber, Nanomaterial, and THz-Metasurface-Mediated Nano-Biosensors: A Review
The increasing use of nanomaterials and scalable, high-yield nanofabrication process are revolutionizing the development of novel biosensors. Over the past decades, researches on nanotechnology-mediated biosensing have been on the forefront due to their potential application in healthcare, pharmaceutical, cell diagnosis, drug delivery, and water and air quality monitoring. The advancement of nanoscale science relies on a better understanding of theory, manufacturing and fabrication practices, and the application specific methods. The topology and tunable properties of nanoparticles, a part of nanoscale science, can be changed by different manufacturing processes, which separate them from their bulk counterparts. In the recent past, different nanostructures, such as nanosphere, nanorods, nanofiber, core–shell nanoparticles, nanotubes, and thin films, have been exploited to enhance the detectability of labelled or label-free biological molecules with a high accuracy. Furthermore, these engineered-materials-associated transducing devices, e.g., optical waveguides and metasurface-based scattering media, widened the horizon of biosensors over a broad wavelength range from deep-ultraviolet to far-infrared. This review provides a comprehensive overview of the major scientific achievements in nano-biosensors based on optical fiber, nanomaterials and terahertz-domain metasurface-based refractometric, labelled and label-free nano-biosensors
Ultra-sensitive and multiplex detection of clinical biomarkers using a SPRi-based sensor
Reliable and reproducible biomarker analysis is the main focus of current clinical diagnostic approaches being developed for the sensitive detection and quantification of biomarkers in bodily fluids. Currently used tools are being revised for better analytical performance that overcomes the drawbacks of inaccurate results. Surface plasmon resonance imaging is rising quickly as an affinity-based optical biosensor that demonstrates numerous improvements to the sensor surface design and sensitivity for label-free and real-time biomarker analysis. In this work, our goal is to develop a more sensitive analytical method for the enhanced detection of the human growth hormone (hGH) in serum, multiplex detection of disease biomarkers (KIM-1 and HMGB-1) simultaneously in buffer using a sandwich-amplification assay, and small molecule- progesterone sensing using a novel aptasensor. Our goals were met by ensuring a homogenous and specific immunosensor for detecting hGH at very low concentrations (> 9.1 pg/mL), substituting random antibody attachment with a site directed immobilization to the sensor surface for multiplex detection of two disease biomarkers down to 5 pg/mL levels in buffer, and further increasing the sensitivity of progesterone biosensor by exploiting x-aptamer technology for highly selective detection of progesterone (> 1 nM) in buffer
Plasmonic microstructured optical fibres: an efficient platform towards biosensing
Detecting life-threatening diseases is a major challenge in biomedicine, as it requires pathogen identication on the molecular level. One promising detection strategy relies on attaching molecular probes to nanoparticles (NPs), which support localised surface plasmon resonance (LSPR). Probe-functionalised NPs can then detect molecular DNA-binding events via a macroscopic change in their optical response. Until now, NP-sensing schemes have been primarily implemented using planar substrates, requiring complex launching techniques and cost-intensive microscopy. An alternative approach adopted in this work involves inltrating optical bres with NPs allowing LSPR excitation and spectral multiplexing within one device. The principle idea relies on probing deposited plasmonic NPs by propagating optical fibre modes, leading to hybrid plasmonic-photonic fibres for biosensing. An important class of innovative bres exploited in this work are microstructured optical bres (MOFs) containing longitudinally invariant microstructures. These structures enable unprecedented adjustment of light matter interaction resulting in a high degree of sensitivity and an optofluidic environment ideally suited for biochemical application. In this thesis optofluidic channels are integrated in direct proximity to the light guiding core, boosting the light-analyte interaction length by orders of magnitude. This concept thus represents a multiscale approach, fundamentally connecting the microscopic level via LSPR-mediated sensing with the macroscopic world using MOFs leading to a novel and unexplored sensor platform. This study shows that combining plasmonic-bre waveguides with microuidics yields a highly integrated, reusable, optouidic interface for efcient refractive index sensing with outlook for DNA diagnostics. This unique combination is extremely attractive from both device and clinical point of view, as the flexible handling of optical fibres principally enables in-vivo application
Space life sciences: A status report
The scientific research and supporting technology development conducted in the Space Life Sciences Program is described. Accomplishments of the past year are highlighted. Plans for future activities are outlined. Some specific areas of study include the following: Crew health and safety; What happens to humans in space; Gravity, life, and space; Sustenance in space; Life and planet Earth; Life in the Universe; Promoting good science and good will; Building a future for the space life sciences; and Benefits of space life sciences research
Development of a low-cost graphene-based impedance biosensor
PhD ThesisThe current applicability and accuracy of point-of-care devices is limited, with
the need of future technologies to simultaneously target multiple analytes in complex
human samples. Graphene’s discovery has provided a valuable opportunity towards
the development of high performance biosensors. The quality and surface properties
of graphene devices are critical for biosensing applications with a preferred low contact
resistance interface between metal and graphene. However, each graphene
production method currently results in inconsistent properties, quality and defects thus
limiting its application towards mass production. Also, post-production processing,
patterning and conventional lithography-based contact deposition negatively impact
graphene properties due to chemical contamination.
The work of this thesis focuses on the development of fully-functional,
label-free graphene-based biosensors and a proof-of-concept was established for the
detection of prostate specific antigen (PSA) in aqueous solution using graphene
platforms. Extensive work was carried out to characterize different graphene family
nanomaterials in order to understand their potential for biosensing applications. Two
graphene materials, obtained via a laser reduction process, were selected for further
investigations: reduced graphene oxide (rGO) and laser induced graphene from
polyimide (LIG). Electrically conductive, porous and chemically active to an extent,
these materials offer the advantage of simultaneous production and patterning as
capacitive biosensing structures, i.e. interdigitated electrode arrays (IDE). Aiming to
enhance the sensitivity of these biosensors, a novel, radio-frequency (RF) detection
method was investigated and compared with conventional electrochemical impedance
spectroscopy (EIS) on a well-known biocompatible material: gold (standard). It was
shown that the RF detection methods require careful design and testing setup, with
conventional EIS performing better in the given conditions. The method was further
used on rGO and LIG IDE devices for the electrochemical impedance detection of PSA
to assess the feasibility of the graphene based materials as biosensors.
The graphene-based materials were successfully functionalized via the
available carboxylic groups, using the EDC-NHS chemistry. Despite the difficulty of
producing reproducible graphene-based electrodes, highly required for biosensor
development, extensive testing was carried out to understand their feasibility. The
calibration curves obtained via successive PSA addition showed a moderate-to-high
ii
sensitivity of both rGO and LIG IDE. However, further adsorption and drift testing
underlined some major limitations in the case of LIG, due to its complex morphology
and large porosity. To enable low contact resistance to these biosensors, the
electroless nickel coating process is shown to be compatible with various
graphene-based materials. This was demonstrated by tuning the chemical nickel bath
and method conditions for pristine graphene and rGO for nickel contacts deposition
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