Carbon Nanotubes for Optical Detection of Quaternary Ammonium Compounds in Complex Media

Abstract

Quaternary ammonium compounds (QACs) are widely used in disinfectants, cleaners, preservatives, cosmetics, and agriculture. Recently, QACs have been detected in the human bloodstream, breast milk, and neonatal mouse brain, which shows that these compounds can cross biological barriers. In vivo studies showed that chronic low-level exposure to QACs causes developmental, reproductive, and immune dysfunctions, whereas in vitro studies indicate that QACs can affect reproductive systems, disrupt cholesterol biosynthesis, increase inflammatory cytokines, and decrease mitochondrial functions. Effects of QACs on health are gradually emerging, amid increased use of QAC disinfectants during the COVID-19 pandemic. Analysis of biological fluids including blood, urine, sweat, and saliva can provide vital information in determining the biological effects of analytes. Biofluid analysis is convenient yet crucial because of non-invasive/or minimally invasive procedures that can be performed outside hospital settings. Interest in optical detection methods for biofluid analysis has been growing due to recent advances in detection technologies and availability of tunable materials to aid the technologies. Detection in the near-infrared (NIR) spectral range is advantageous over the visible range mainly due to minimal autofluorescence, light-scattering, and absorption from native biological molecules in the NIR range. Photoluminescent single-walled carbon nanotubes (SWCNTs) are promising candidates for the development of NIR optical probes and sensors due to their non-photobleaching NIR fluorescence, tunable surface chemistry, and high sensitivity. Herein, we report optical detection of QACs in protein-rich media and a model biofluid. We functionalized photoluminescent SWCNTs with bile salt derivatives that enabled the detection of QACs in artificial sweat and serum-protein-enriched media. The QAC detection was significant at nanomolar concentrations, which is within the threshold that can affect various physiological processes. Thus, nanotube-based optical detection could be well suited for the analysis of QACs in biological fluids.

Rationally Designed Functionalization of Single‐Walled Carbon Nanotubes for Real‐Time Monitoring of Cholinesterase Activity and Inhibition in Plasma

“…[ 42–59 ] A compelling avenue involves the utilization of single‐walled carbon nanotubes (SWCNTs), which offer several advantageous features such as remarkable photostable fluorescence emission in the NIR range, biocompatibility, and ease of surface functionalization. [ 60–70 ] SWCNTs have been used for fluorometric detection of important analytes, including small molecules, [ 53,71–74 ] oncometalbolites, [ 75 ] proteins, [ 60,61,68,69,76–80 ] neurotransmitters, [ 42,81–83 ] pathogens, [ 84,85 ] metal ions, [ 86 ] endolysosomal pH, [ 87 ] disease biomarkers, [ 88,89 ] plant hormones, [90] sugars, [91] quaternary ammonium compounds, [ 92 ] microRNA [ 93–95 ] cytokines, [ 79 ] volatiles, [ 96,97 ] hormones, [ 90,98 ] and bacterial siderophores, [60] to name a few. In addition, SWCNTs have been utilized as a probe for the inactivation of tyrosinase enzyme by observing a bathochromic shift in their emission wavelength, induced by the generation of singlet oxygen during the enzyme inactivation process.…”

Understanding the Molecular Assemblies of Single Walled Carbon Nanotubes and Tailoring their Photoluminescence for the Next-Generation Optical Nanosensors

“…14 Thus, SWCNTs are considered to be valuable materials for developing optical sensors. As a result, nanotube-based fluorescent sensors have been developed for detection of reactive oxygen species, 22 pH, 23 quaternary ammonium compound disinfectants, 24 neurotransmitters, 25 glucose, 20 proteins, nucleic acids, and hydrogen peroxide 26 etc.…”

Development of Optical Nanosensors for Detection of Potassium Ions and Assessment of Their Biocompatibility with Corneal Epithelial Cells

“…Semiconducting single-walled carbon nanotubes (SWCNTs) possess unique optical properties including nonphotobleaching fluorescence in the NIR region, high optical sensitivity, and high stability. − To render SWCNTs soluble in aqueous media, nanotubes can be noncovalently functionalized with polymers, , oligonucleotides, small molecules, and surfactants . Such noncovalently functionalized SWCNT-based optical sensors have been developed for the detection of target analytes such as viruses like COVID-19 virus and human immunodeficiency virus, protein biomarkers, quaternary ammonium compounds, pH, glucose, and neurotransmitters . These studies provide a basis for the development of targeted molecular sensors based on photoluminescent SWCNTs.…”