Skin Interstitial Fluid-Based SERS Tags Labeled Microneedles for Tracking of Peritonitis Progression and Treatment Effect

Hydrogel-Coated SERS Microneedles for Drug Monitoring in Dermal Interstitial Fluid

In vivo drug monitoring is crucial for evaluating the effectiveness and safety of drug treatment. Blood sampling and analysis is the current gold standard but needs professional skills and cannot meet the requirements of point-of-care testing. Dermal interstitial fluid (ISF) showed great potential to replace blood for in vivo drug monitoring; however, the detection was challenging, and the drug distribution behavior in ISF was still unclear until now. In this study, we proposed surface-enhanced Raman spectroscopy (SERS) microneedles (MNs) for the painless and real-time analysis of drugs in ISF after intravenous injection. Using methylene blue (MB) and mitoxantrone (MTO) as model drugs, the innovative core-satellite structured Au@Ag SERS substrate, hydrogel coating over the MNs, rendered sensitive and quantitative drug detection in ISF of mice within 10 min. Based on this technique, the pharmacokinetics of the two drugs in ISF was investigated and compared with those in blood, where the drugs were analyzed via liquid chromatography-mass spectrometry. It was found that the MB concentration in ISF and blood was comparable, whereas the concentration of MTO in ISF was 2-3 orders of magnitude lower than in blood. This work proposed an efficient tool for ISF drug monitoring. More importantly, it experimentally proved that the penetration ratio of blood to ISF was drug-dependent, providing insightful information into the potential of ISF as a blood alternative for in vivo drug detection.

Swellable microneedle-coupled light-addressable photoelectrochemical sensor for in-situ tracking of multiple pesticides pollution in vivo

In vivo monitoring of multiple pesticide contamination is of great significance for evaluating the health risks of different pesticides, agricultural production safety, and ecological and environmental assessment. Here, we report a hydrogel microneedle array coupled light-addressable photoelectrochemical sensor for tracking multiple pesticide uptake and elimination in living animals and plants, holding three prominent merits: i) enables in-situ detection of in vivo pesticides, avoiding cumbersome and complex sample transportation and handling processes; ii) allows repeated in vivo sampling of the same organism, improving tracking test controllability and accuracy; iii) avoids lethal sampling, providing a better understanding of the pesticides fate in living organisms. The coupled sensor is mechanically robust for withstanding more than 0.35 N per needle and highly swellable (800 %) for timely extraction of sufficient in vivo solution for analysis. For proof-of-concept, it achieves in-situ detection of atrazine, acetamiprid, and carbendazim efficiently and quantitatively in artificial agarose skin models, mouse skin interstitial fluids, and plant leaves with little inflammatory reaction. This simple, highly integrated, minimally invasive, and high-throughput in vivo monitoring method is ideal for future field environmental monitoring and plant and animal disease diagnosis.

Enhancing charge transfer in a W18O49/g-C3N4 heterostructure via band structure engineering for effective SERS detection and flexible substrate applications

Chemical mechanism (CM)-related surface-enhanced Raman spectroscopy (SERS) has received tremendous interest due to its exceptional stability and excellent uniformity. Nevertheless, there remains a demand for ingenious methodologies for promoting effective charge transfer (CT) to improve SERS sensitivity further. Herein, a band structure engineered W18O49/g-C3N4 heterostructure (WCN) was first employed as a CM-based SERS substrate with remarkable enhancement and sensitivity. To investigate the Raman enhancement properties of the substrate, malachite green (MG) was employed as the Raman probe with the excitation of a 633 nm laser. The WCN substrate exhibits a Raman enhancement factor (EF) of 2.6 × 107, achieving a limit of detection (LOD) of 1.9 × 10-10 M for MG. The outstanding Raman amplification behavior can be attributed to the heterojunction-induced efficient CT process, energy band matching resonance due to minor doping with g-C3N4 serving as a band gap modifier, and improved photo-induced charge transfer (PICT) efficiency via the oxygen vacancies in the W18O49 units. Additionally, a flexible SERS substrate based on WCN was constructed using a vacuum filtration method and utilized to detect prohibited pharmaceutical residues on fish skin. The integration of this WCN and a nylon membrane not only preserves the Raman activity of the WCN for sensitive detection but also endows the Raman substrate with high flexibility and good mechanical durability, making it a potential candidate for in situ detection in particular environments.

A ratiometric SERS sensor with one signal probe for ultrasensitive and quantitative monitoring of serum xanthine

Xanthine can be converted into uric acid, and a high concentration of xanthine in the human body can cause many diseases. Therefore, it is important to develop a sensitive, simple, and reliable approach for measuring xanthine in biological liquids. Hence, a ratiometric surface-enhanced Raman spectroscopy (SERS) sensing strategy with one signal probe was exploited for reliable, sensitive, and quantitative monitoring of serum xanthine. 3-Mercaptophenylboronic acid (3-MPBA) was used as a typical reference with a Raman peak at 996 cm-1. First, 3-MPBA was bound to gold nanoflowers@silica (GNFs@Si) through Au-S bonds. Xanthine oxidase (XOD) catalyzed the oxidation of xanthine into H2O2 on GNFs@Si. Afterward, the obtained H2O2 further reduced 3-MPBA to 3-hydroxythiophenol (3-HTP) accompanied by the emergence of a new Raman peak at 883 cm-1. Meanwhile, the Raman intensity at 996 cm-1 remained constant. Therefore, the ratio of I883/I996 increased with the increasing of xanthine concentration, thus realizing quantitative detection of xanthine. As a result, a ratiometric SERS sensor for the detection of xanthine was proposed with a detection limit of 5.7 nM for xanthine. The novel ratiometric SERS sensor provides a new direction for analyzing other biomolecules with high sensitivity and reliability.

Research Progress of SERS Sensors Based on Hydrogen Peroxide and Related Substances

Hydrogen peroxide (H2O2) has an important role in living organisms, and its detection is of great importance in medical, chemical, and food safety applications. This review provides a comparison of different types of Surface-enhanced Raman scattering (SERS) sensors for H2O2 and related substances with respect to their detection limits, which are of interest due to high sensitivity compared to conventional sensors. According to the latest research report, this review focuses on the sensing mechanism of different sensors and summarizes the linear range, detection limits, and cellular applications of new SERS sensors, and discusses the limitations in vivo and future prospects of SERS technology for the detection of H2O2.

Optical Methods for Non-Invasive Determination of Skin Penetration: Current Trends, Advances, Possibilities, Prospects, and Translation into In Vivo Human Studies

Information on the penetration depth, pathways, metabolization, storage of vehicles, active pharmaceutical ingredients (APIs), and functional cosmetic ingredients (FCIs) of topically applied formulations or contaminants (substances) in skin is of great importance for understanding their interaction with skin targets, treatment efficacy, and risk assessment-a challenging task in dermatology, cosmetology, and pharmacy. Non-invasive methods for the qualitative and quantitative visualization of substances in skin in vivo are favored and limited to optical imaging and spectroscopic methods such as fluorescence/reflectance confocal laser scanning microscopy (CLSM); two-photon tomography (2PT) combined with autofluorescence (2PT-AF), fluorescence lifetime imaging (2PT-FLIM), second-harmonic generation (SHG), coherent anti-Stokes Raman scattering (CARS), and reflectance confocal microscopy (2PT-RCM); three-photon tomography (3PT); confocal Raman micro-spectroscopy (CRM); surface-enhanced Raman scattering (SERS) micro-spectroscopy; stimulated Raman scattering (SRS) microscopy; and optical coherence tomography (OCT). This review summarizes the state of the art in the use of the CLSM, 2PT, 3PT, CRM, SERS, SRS, and OCT optical methods to study skin penetration in vivo non-invasively (302 references). The advantages, limitations, possibilities, and prospects of the reviewed optical methods are comprehensively discussed. The ex vivo studies discussed are potentially translatable into in vivo measurements. The requirements for the optical properties of substances to determine their penetration into skin by certain methods are highlighted.

Fluid-based wearable sensors: a turning point in personalized healthcare

Nowadays, it has become very popular to develop wearable devices that can monitor biomarkers to analyze the health status of the human body more comprehensively and accurately. Wearable sensors, specially designed for home care services, show great promise with their ease of use, especially during pandemic periods. Scientists have conducted many innovative studies on new wearable sensors that can noninvasively and simultaneously monitor biochemical indicators in body fluids for disease prediction, diagnosis, and management. Using noninvasive electrochemical sensors, biomarkers can be detected in tears, saliva, perspiration, and skin interstitial fluid (ISF). In this review, biofluids used for noninvasive wearable sensor detection under four main headings, saliva, sweat, tears, and ISF-based wearable sensors, were examined in detail. This report analyzes nearly 50 recent articles from 2017 to 2023. Based on current research, this review also discusses the evolution of wearable sensors, potential implementation challenges, and future prospects.