Cannabinoid sensing
in biofluids provides great insight into the
effects of medicinal cannabis on the body. The prevalence of cannabis
for pain management and illicit drug use necessitates knowledge translation
in cannabinoids. In this Review, we provide an overview of the current
detection methods of cannabinoids in bodily fluids emphasizing electrochemical
sensing. First, we introduce cannabinoids and discuss the structure
and metabolism of Δ9-THC and its metabolites in relation
to blood, urine, saliva, sweat, and breath. Next, we briefly discuss
lab based techniques for cannabinoids in biofluids. While these techniques
are highly sensitive and specific, roadside safety requires a quick,
portable, and cost-effective sensing method. These needs motivated
a comprehensive review of advantages, disadvantages, and future directions
for electrochemical sensing of cannabinoids. The literature shows
the lowest limit of detection to be 3.3 pg of Δ9-THC/mL
using electrochemical immunosensors, while electrodes fabricated with
low cost methods such as screen-printing and carbon paste can detect
as little as 25 and 1.26 ng of Δ9-THC/mL, respectively.
Future research will include nanomaterial modified working electrodes,
for simultaneous sensing of multiple cannabinoids. Additionally, there
should be an emphasis on selectivity for cannabinoids in the presence
of interfering compounds. Sensors should be fully integrated on biocompatible
substrates with control electronics and intelligent components for
wearable diagnostics. We hope this Review will prove to be the seminal
work in the electrochemical sensing of cannabinoids.
Electrochemical sensing guidelines for glutamate in biofluids, associated with different diseases, providing knowledge translation among science, engineering, and medical professionals.
Heavy metal pollution is a severe environmental problem affecting many water resources. The nonbiodegradable nature of the heavy metals such as lead (Pb) causes severe human health issues, so their cost-effective, sensitive and rapid detection is needed. In this work, we describe a simple, facile and low cost modifications of multiwalled carbon nanotubes (MWCNT) and β-cyclodextrin (βCD) through non-covalent/physical (Phys) and a covalent Steglich esterification (SE) approaches. The Phys modification approach resulted Pb detection with a limit-of-detection (LoD) of 0.9 ppb, while the SE approach showed an LoD of 2.3 ppb, both of which are well below the WHO Pb concentration guideline of 10 ppb. The MWCNT-βCD (Phys) based electrodes show negligible interference with other common heavy metal ions such as Cd 2+ and Zn 2+ . The MWCNT-βCD based electrodes were of low-cost owing to their simple synthesis approaches, exhibited good selectivity and reusability. The proposed MWCNT-βCD based electrodes is a promising technology in developing a highly affordable and sensitive electrochemical sensing system of Pb in drinking water.3 Accessibility to potable water is increasingly challenging in developing and in some developed countries due to contamination of their source waters with heavy metal ion and other pollutants. 1 Heavy metals such as lead (Pb) are non-biodegradable and widely distributed and its presence in drinking water causes greater risks to human health. 2 The effects of Pb include behavioral disorder and neurodevelopmental problems in children; increased blood pressure and renal dysfunction in adults;and even cancer in kidneys, lung, or brain due to its long-term presence in source and drinking water. [3][4][5][6][7] According to World Health Organization (WHO) guidelines, the maximum acceptable concentration of Pb in drinking water should be 10 µg/L or 10 ppb. 6 However, drinking water authorities such as in Canada are proposing an even stricter limit (e.g., 5 ppb) for Pb in drinking water. 6 Major challenges in implementing the stricter limit include the lack of on-site monitoring techniques, and detecting contaminant levels across distributed water sources. Therefore, a simple, low-cost and easy to use sensor for the detection of a heavy metal such as Pb is necessary to maintain water safety in resourcelimited areas.Conventional analytical techniques such as inductively coupled plasma mass spectrometry and atomic absorption spectroscopy require qualified testing laboratories and trained personnel. 8,9 Recently, electrochemical methods have made considerable progress towards simple, on-site and low-cost detection capabilities to allow adequate time for taking safety measures in case of a contamination. 10The electrochemical sensors, commonly referred to as "electrodes", are ideal candidates as they can be fabricated with low-cost to detect Pb with higher precision and accuracy. The material system of a sensing electrode is the key ingredient in maximizing overall performance of an electrochemical analysis in...
Sequential plasma activated bonding (SPAB) process consisting of oxygen reactive ion etching (RIE) and nitrogen microwave radical plasma was developed for silicon direct bonding at room temperature. A strong influence of plasma time and gas pressure on voids was found both in the SPAB and O2 RIE processes. Tensile strength and surface roughness are functions of oxygen RIE, nitrogen radical time and gas pressure. Improved tensile strength was achieved in the SPAB process. High resolution transmission electron microscope (HRTEM) observations showed a thicker silicon oxide interfacial layer from the SPAB process than that from the O2 RIE process. The increase in thickness of interfacial oxide layers in both processes after annealing at 600{degree sign}C for 2 h in air is attributed to the oxygen concentration of silicon bulk wafers. The SPAB process can be explained by the reaction between two metastable surfaces, which allows water removal from interface, resulting in covalent Si-O-Si bonding.
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