An Endoscope-like SERS Probe Based on the Focusing Effect of Silica Nanospheres for Tyrosine and Urea Detection in Sweat

Abstract

In this work, we developed a new type of SERS probe, which was composed of glass-SiO2-Au@MBN@Ag nanoparticles (NPs) three-dimensional Surface-enhanced Raman spectroscopy (SERS) substrate. When the laser passed through the quartz glass sheet, on the one hand, the SiO2 NPs supporting the Au@MBN@Ag NPs increase the roughness of the substrate surface, resulting in a large number of hot spots among nanoparticles. On the other hand, based on the focusing effect of silicon dioxide nanospheres, the laser can better focus on the surface of nanoparticles in the inverted SERS probe, thus showing better SERS enhancement. Furthermore, the Au@MBN@Ag NPs core-shell structure was used with 4-mercaptobenzoonitrile (MBN) as an internal standard molecule, and the quantitative determination of tyrosine and urea was realized by internal standard correction method. The standard working curves of the two had good linear correlation with R2 above 0.9555. The detection limits of tyrosine and urea were in the range of 2.85 × 10−10 M~7.54 × 10−6 M, which confirms that this design can be used for quantitative and specific detection of biological molecules, demonstrating great practical significance for the research of diseases such as skin lesions and endocrine disorders.

Direct Laser Writing of the Porous Graphene Foam for Multiplexed Electrochemical Sweat Sensors

“…Drugs detection in sweat (e.g., acetaminophen (APAP) and caffeine (CAF) can help avoid liver failure from excessive use of APAP or other health problems (e.g., coronary syndrome, hypertension, and depression) from chronic overdoses of CAF. , The lead and chromium in sweat were used for noninvasive monitoring of heavy metal poisoning . A wearable glove-embedded sensor was developed for the noninvasive and selective determination of biomarkers in therapeutic drugs and sweat samples. , As a result, diverse wearable electrochemical sensors have been developed to monitor the metabolites and electrolytes in the sweat on-body (e.g., Glu, ,− lactate, , ion, ,− UA, , and Tyr − sensors). As the enzyme-based wearable sweat sensors are often expensive with sensitivity susceptible to temperature and pH, − enzyme-free sweat sensors relying on diverse sensing materials (e.g., graphene, − laser-induced graphene (LIG), , and PEDOT/PSS hydrogel) have been developed with excellent stability in harsh environment. − Compared with graphene prepared by the complicated fabrication process, , the 3D porous graphene comes from the low-cost, rapid, and scalable direct laser writing, which also exhibits fast electron mobility, high current density, and ultra-large surface area. ,, Benefiting from large surface areas and rich surface defects induced during the laser scribing process, pristine LIG-based devices have been widely explored for the detection of small molecules. ,− However, the resulting electrochemical sensors based on the porous graphene still show limited peak response and are greatly affected by background current.…”

Optical urea sensing in sweat for kidney healthcare by sensitive and selective non-enhanced Raman spectroscopy

“…For sensitively recording lower molecular concentrations in the ranges of hundreds of micromolar, such as sweat uric acid (not urea) or sweat creatinine, Raman enhancement is required 22 . Nevertheless, until now, only the enhanced Raman spectroscopy mechanism has shown the possibility of quantitative sweat urea monitoring [23][24][25] . The fabrication of plasmonic surfaces to enable such enhancements comes with challenges, such as limited reusability, tedious clean-room fabrication requirements, limited shelf-life of the enhancement substrate, and interference from the plasmonic materials 26 .…”

The Study and Application of Nanosilica Biosensor for Sweat Detection

“…The capacitive sweat sensor based on mesoporous nanosilica can be used as a potential candidate for the rate test of human sweating [9] . A Surface-enhanced Raman scattering (SERS) probe based on the silica nanospheres' concentrating effect achieves the quantitative and specific detection of tyrosine and urea in sweat [10] . Nevertheless, there are several problems among the applications above in sweat detection, such as the dependence on precision instruments, the complexity of the preparation process, and the high cost of detection, which may limit their practical applications in sweat detection.…”