High testosterone is associated with increased physical performance in sports due to its stimulation with body-muscle ratio, lean mass (muscle and bone), and bone density. Several studies show athletes with better explosive strength and sprint running performances in football, have a higher basal level of testosterone. The results suggest a relationship between testosterone production and the development of fast-twitch muscle fibers, endurance training, lean mass, resistance training in athletes as well as motivation for competition. Thus, monitoring testosterone levels is gaining attention to evaluate athletic performance of one's physical performance in sport, fitness, and bodybuilding as well as prevent health risk factors for low levels of testosterone. There have been attempts using optical, electrical and biochemical sensors to monitor testosterone but are difficult to reproduce in large quantities and suffer from limitations of sensitivity, and detection limits. This can be addressed using Molecularly Imprinted Polymers (MIPs) in a point of care (POC) system. Molecularly Imprinted Polymers (MIPs) are a synthetic polymer with cavities in the polymer matrix serve as recognition sites for a specific template molecule, which are detected using electrochemical amperometry. In this paper, we have used MIPs in conjunction with cyclic voltammetry, to produce a viable, ultrasensitive electrochemical sensor for the detection of testosterone from a human sweat sample. This combination of MIPs and cyclic voltammetry allows for a simple, low-cost, mass-producible, and non-invasive method for detecting testosterone in human males. This method is extremely simple and cheap, allowing for consistent measurement of Testosterone levels in humans and allows for the detection of Testosterone in a POC. In our work, a Screen-printed carbon electrode (SPCE) using polypropylene fabric was used as the base working electrode in a three-electrode system. The screen-printing technique was implemented to layer a carbon paste over both sides of the fabric and was air-dried for one hour at 75⁰C. The SPCE was immersed into an acetate buffer solution that contains a 2.0mM monomer called o-phenylenediamine and with a 0.1mM testosterone template. Electropolymerization was carried out with cyclic voltammetry from a range of 0V to 1.0V, at a scan rate of 50 mV/s, a sensitivity (A/V) of 1e-5A, and for a total of 30 cycles. The set concentration tested was 100-1600 ng/ml of testosterone. The electrochemical characterization will have a potential sweep of -1.2 V to 1.2 V, a scan rate of 0.05 (V/s), a sensitivity (A/V) of 1e-5A, and a singular cycle. The wearable biosensor showed a detection range for testosterone from 100ng to 1600ng, electrochemical results also showed a clear and measurable result with an R-square value of 0.9417 which proves the accuracy of the developed sensor. Although this is not the complete saturation point and theoretically maximum limit of 28,842ng/ml can be achieved although this was not tested. The detectable lowest concentration of testosterone was found to be ~100ng/ml, and it was noted that lower than 100ng gives a weaker signal, In conclusion a novel electrochemical sensor based on a molecularly imprinted polymer used as the extended gate of a field effect transistor was developed for the ultrasensitive detection of sweat Testosterone. This sensing technology paves the way for the low cost, label-free, and point of care detection which can be used for evaluating ang monitoring athletic performance.
more »
« less
Sense–Analyze–Respond–Actuate (SARA) Paradigm: Proof of Concept System Spanning Nanoscale and Macroscale Actuation for Detection of Escherichia coli in Aqueous Media
Foodborne pathogens are a major concern for public health. We demonstrate for the first time a partially automated sensing system for rapid (~17 min), label-free impedimetric detection of Escherichia coli spp. in food samples (vegetable broth) and hydroponic media (aeroponic lettuce system) based on temperature-responsive poly(N-isopropylacrylamide) (PNIPAAm) nanobrushes. This proof of concept (PoC) for the Sense-Analyze-Respond-Actuate (SARA) paradigm uses a biomimetic nanostructure that is analyzed and actuated with a smartphone. The bio-inspired soft material and sensing mechanism is inspired by binary symbiotic systems found in nature, where low concentrations of bacteria are captured from complex matrices by brush actuation driven by concentration gradients at the tissue surface. To mimic this natural actuation system, carbon-metal nanohybrid sensors were fabricated as the transducer layer, and coated with PNIPAAm nanobrushes. The most effective coating and actuation protocol for E. coli detection at various temperatures above/below the critical solution temperature of PNIPAAm was determined using a series of electrochemical experiments. After analyzing nanobrush actuation in stagnant media, we developed a flow through system using a series of pumps that are triggered by electrochemical events at the surface of the biosensor. SARA PoC may be viewed as a cyber-physical system that actuates nanomaterials using smartphone-based electroanalytical testing of samples. This study demonstrates thermal actuation of polymer nanobrushes to detect (sense) bacteria using a cyber-physical systems (CPS) approach. This PoC may catalyze the development of smart sensors capable of actuation at the nanoscale (stimulus-response polymer) and macroscale (non-microfluidic pumping).
more »
« less
- NSF-PAR ID:
- 10301150
- Date Published:
- Journal Name:
- Actuators
- Volume:
- 10
- Issue:
- 1
- ISSN:
- 2076-0825
- Page Range / eLocation ID:
- 2
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Evaluating surface bacterial growth at buried interfaces can be problematic due to the difficulties associated with obtaining samples. In this work, we present a new method to detect signals from microorganisms at buried interfaces that is nondestructive and can be conducted continuously. Inspired by vascular systems in nature that permit chemical communication between the surface and underlying tissues of an organism, we created a system in which an inert carrier fluid could be introduced into an empty vascular network embedded in a polymer matrix. When a microorganism layer was grown on top, small molecules produced by the growth process would diffuse down into the carrier fluid, which could then be collected and analyzed. We used this system to nondestructively detect signals from a surface layer of Escherichia coli using conductivity, ultraviolet–visible (UV–vis) absorbance spectroscopy, and high-performance liquid chromatography (HPLC) for organic acids, methods that ranged in sensitivity, time-to-result, and cost. Carrier fluid from sample vascularized polymers with surface bacterial growth recorded significantly higher values in both conductivity and absorbance at 350 nm compared to controls with no bacteria after 24 h. HPLC analysis showed three clear peaks that varied between the samples with bacteria and the controls without. Tests tracking the change in signals over 48 h showed clear trends that matched the bacterial growth curves, demonstrating the system’s ability to monitor changes over time. A 2D finite element model of the system closely matched the experimental results, confirming the predictability of the system. Finally, tests using clinically relevant Staphylococcus aureus and Pseudomonas aeruginosa yielded differences in conductivity, absorbance, and HPLC peak areas unique to each species. This work lays the foundation for the use of vascularized polymers as an adaptive system for the continuous, nondestructive detection of surface microorganisms at buried interfaces in both industry and medicine.more » « less
-
null (Ed.)Irrigation water is a primary source of fresh produce contamination by bacteria during the preharvest, particularly in hydroponic systems where the control of pests and pathogens is a major challenge. In this work, we demonstrate the development of a Listeria biosensor using platinum interdigitated microelectrodes (Pt-IME). The sensor is incorporated into a particle/sediment trap for the real-time analysis of irrigation water in a hydroponic lettuce system. We demonstrate the application of this system using a smartphone-based potentiostat for rapid on-site analysis of water quality. A detailed characterization of the electrochemical behavior was conducted in the presence/absence of DNA and Listeria spp., which was followed by calibration in various solutions with and without flow. In flow conditions (100 mL samples), the aptasensor had a sensitivity of 3.37 ± 0.21 kΩ log-CFU−1 mL, and the LOD was 48 ± 12 CFU mL−1 with a linear range of 102 to 104 CFU mL−1. In stagnant solution with no flow, the aptasensor performance was significantly improved in buffer, vegetable broth, and hydroponic media. Sensor hysteresis ranged from 2 to 16% after rinsing in a strong basic solution (direct reuse) and was insignificant after removing the aptamer via washing in Piranha solution (reuse after adsorption with fresh aptamer). This is the first demonstration of an aptasensor used to monitor microbial water quality for hydroponic lettuce in real time using a smartphone-based acquisition system for volumes that conform with the regulatory standards. The aptasensor demonstrated a recovery of 90% and may be reused a limited number of times with minor washing steps.more » « less
-
ABSTRACT Soil bacteria adapt to diverse and rapidly changing environmental conditions by sensing and responding to environmental cues using a variety of sensory systems. Two-component systems are a widespread type of signal transduction system present in all three domains of life and typically are comprised of a sensor kinase and a response regulator. Many two-component systems function by regulating gene expression in response to environmental stimuli. The bacterial chemotaxis system is a modified two-component system with additional protein components and a response that, rather than regulating gene expression, involves behavioral adaptation and results in net movement toward or away from a chemical stimulus. Soil bacteria generally have 20 to 40 or more chemoreceptors encoded in their genomes. To simplify the identification of chemoeffectors (ligands) sensed by bacterial chemoreceptors, we constructed hybrid sensor proteins by fusing the sensor domains of Pseudomonas putida chemoreceptors to the signaling domains of the Escherichia coli NarX/NarQ nitrate sensors. Responses to potential attractants were monitored by β-galactosidase assays using an E. coli reporter strain in which the nitrate-responsive narG promoter was fused to lacZ . Hybrid receptors constructed from PcaY, McfR, and NahY, which are chemoreceptors for aromatic acids, tricarboxylic acid cycle intermediates, and naphthalene, respectively, were sensitive and specific for detecting known attractants, and the β-galactosidase activities measured in E. coli correlated well with results of chemotaxis assays in the native P. putida strain. In addition, a screen of the hybrid receptors successfully identified new ligands for chemoreceptor proteins and resulted in the identification of six receptors that detect propionate. IMPORTANCE Relatively few of the thousands of chemoreceptors encoded in bacterial genomes have been functionally characterized. More importantly, although methyl-accepting chemotaxis proteins, the major type of chemoreceptors present in bacteria, are easily identified bioinformatically, it is not currently possible to predict what chemicals will bind to a particular chemoreceptor. Chemotaxis is known to play roles in biodegradation as well as in host-pathogen and host-symbiont interactions, but many studies are currently limited by the inability to identify relevant chemoreceptor ligands. The use of hybrid receptors and this simple E. coli reporter system allowed rapid and sensitive screening for potential chemoeffectors. The fusion site chosen for this study resulted in a high percentage of functional hybrids, indicating that it could be used to broadly test chemoreceptor responses from phylogenetically diverse samples. Considering the wide range of chemical attractants detected by soil bacteria, hybrid receptors may also be useful as sensitive biosensors.more » « less
-
Rapid, simple, inexpensive, accurate, and sensitive point-of-care (POC) detection of viral pathogens in bodily fluids is a vital component of controlling the spread of infectious diseases. The predominant laboratory-based methods for sample processing and nucleic acid detection face limitations that prevent them from gaining wide adoption for POC applications in low-resource settings and self-testing scenarios. Here, we report the design and characterization of an integrated system for rapid sample-to-answer detection of a viral pathogen in a droplet of whole blood comprised of a 2-stage microfluidic cartridge for sample processing and nucleic acid amplification, and a clip-on detection instrument that interfaces with the image sensor of a smartphone. The cartridge is designed to release viral RNA from Zika virus in whole blood using chemical lysis, followed by mixing with the assay buffer for performing reverse-transcriptase loop-mediated isothermal amplification (RT-LAMP) reactions in six parallel microfluidic compartments. The battery-powered handheld detection instrument uniformly heats the compartments from below, and an array of LEDs illuminates from above, while the generation of fluorescent reporters in the compartments is kinetically monitored by collecting a series of smartphone images. We characterize the assay time and detection limits for detecting Zika RNA and gamma ray-deactivated Zika virus spiked into buffer and whole blood and compare the performance of the same assay when conducted in conventional PCR tubes. Our approach for kinetic monitoring of the fluorescence-generating process in the microfluidic compartments enables spatial analysis of early fluorescent “bloom” events for positive samples, in an approach called “Spatial LAMP” (S-LAMP). We show that S-LAMP image analysis reduces the time required to designate an assay as a positive test, compared to conventional analysis of the average fluorescent intensity of the entire compartment. S-LAMP enables the RT-LAMP process to be as short as 22 minutes, resulting in a total sample-to-answer time in the range of 17–32 minutes to distinguish positive from negative samples, while demonstrating a viral RNA detection as low as 2.70 × 10 2 copies per μl, and a gamma-irradiated virus of 10 3 virus particles in a single 12.5 μl droplet blood sample.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3390/act10010002
