Upconversion Nanoparticles Based Sensing: From Design to Point-of-Care Testing

Rare earth-doped upconversion nanoparticles (UCNPs) have achieved a wide range of applications in the sensing field due to their unique anti-Stokes luminescence property, minimized background interference, excellent biocompatibility, and stable physicochemical properties. However, UCNPs-based sensing platforms still face several challenges, including inherent limitations from UCNPs such as low quantum yields and narrow absorption cross-sections, as well as constraints related to energy transfer efficiencies in sensing systems. Therefore, the construction of high-performance UCNPs-based sensing platforms is an important cornerstone for conducting relevant research. This work begins by providing a brief overview of the upconversion luminescence mechanism in UCNPs. Subsequently, it offers a comprehensive summary of the sensors' types, design principles, and optimized design strategies for UCNPs sensing platforms. More cost-effective and promising point-of-care testing applications implemented based on UCNPs sensing systems are also summarized. Finally, this work addresses the future challenges and prospects for UCNPs-based sensing platforms.

Recent advances in the development of portable technologies and commercial products to detect Δ9-tetrahydrocannabinol in biofluids: a systematic review

BACKGROUND

The primary components driving the current commercial fascination with cannabis products are phytocannabinoids, a diverse group of over 100 lipophilic secondary metabolites derived from the cannabis plant. Although numerous phytocannabinoids exhibit pharmacological effects, the foremost attention has been directed towards Δ9-tetrahydrocannabinol (THC) and cannabidiol, the two most abundant phytocannabinoids, for their potential human applications. Despite their structural similarity, THC and cannabidiol diverge in terms of their psychotropic effects, with THC inducing notable psychological alterations. There is a clear need for accurate and rapid THC measurement methods that offer dependable, readily accessible, and cost-effective analytical information. This review presents a comprehensive view of the present state of alternative technologies that could potentially facilitate the creation of portable devices suitable for on-site usage or as personal monitors, enabling non-intrusive THC measurements.

METHOD

A literature survey from 2017 to 2023 on the development of portable technologies and commercial products to detect THC in biofluids was performed using electronic databases such as PubMed, Scopus, and Google Scholar. A systematic review of available literature was conducted using Preferred Reporting Items for Systematic. Reviews and Meta-analysis (PRISMA) guidelines.

RESULTS

Eighty-nine studies met the selection criteria. Fifty-seven peer-reviewed studies were related to the detection of THC by conventional separation techniques used in analytical laboratories that are still considered the gold standard. Studies using optical (n = 12) and electrochemical (n = 13) portable sensors and biosensors were also identified as well as commercially available devices (n = 7).

DISCUSSION

The landscape of THC detection technology is predominantly shaped by immunoassay tests, owing to their established reliability. However, these methods have distinct drawbacks, particularly for quantitative analysis. Electrochemical sensing technology holds great potential to overcome the challenges of quantification and present a multitude of advantages, encompassing the possibility of miniaturization and diverse modifications to amplify sensitivity and selectivity. Nevertheless, these sensors have considerable limitations, including non-specific interactions and the potential interference of compounds and substances existing in biofluids.

CONCLUSION

The foremost challenge in THC detection involves creating electrochemical sensors that are both stable and long-lasting while exhibiting exceptional selectivity, minimal non-specific interactions, and decreased susceptibility to matrix interferences. These aspects need to be resolved before these sensors can be successfully introduced to the market.

Rapid electrochemical lateral flow device for the detection of Δ9-tetrahydrocannabinol

Cannabis is a plant that is harmful and beneficial because it contains more than 400 bioactive compounds, and the main compounds are Δ9 tetrahydrocannabinol (THC) and cannabidiol (CBD). Currently, cannabis extracts are used in medicine, but the amount of THC as a main psychoactive component is strictly regulated. Therefore, the ability to rapidly and accurately detect THC is important. Herein, we developed a sensitive electrochemical method combining a rapid lateral flow assay (LFA) to detect THC rapidly. An electrochemical LFA device was constructed by attaching a screen-printed electrode inside a lateral-flow device to exploit the remarkable binding of THC to the cannabinoid type 2 (CB2) receptor in the test zone. The ferrocene carboxylic acid attached to the monoclonal THC antibody acts as an electroactive species when it binds to the THC in the sample before it flows continuously to the CB2 receptor region on the electrode. Under optimal conditions, the detection time is within 6 min and the devise shows excellent performance with a detection limit of 1.30 ng/mL. Additionally, the device could be applied to detect THC in hemp extract samples. The results obtained from this sensor are similar to the standard method (HPLC) for detecting THC. Therefore, this proposed device is useful as an alternative device for the on-site determination of THC because it is inexpensive, portable, and exhibits high sensitivity.

Recent Trends in Lateral Flow Immunoassays with Optical Nanoparticles

Rapid, accurate, and convenient diagnosis is essential for effective disease management. Various detection methods, such as enzyme-linked immunosorbent assay, have been extensively used, with lateral flow immunoassay (LFIA) recently emerging as a major diagnostic tool. Nanoparticles (NPs) with characteristic optical properties are used as probes for LFIA, and researchers have presented various types of optical NPs with modified optical properties. Herein, we review the literature on LFIA with optical NPs for the detection of specific targets in the context of diagnostics.

Europium Nanoparticles-Based Fluorescence Immunochromatographic Detection of Three Abused Drugs in Hair

Drug abuse is becoming increasingly dangerous nowadays. Morphine (MOP), methamphetamine (MET) and ketamine (KET) are the most commonly abused drugs. The abuse of these drugs without supervision can cause serious harm to the human body and also endanger public safety. Developing a rapid and accurate method to screen drug suspects and thus control these drugs is essential to public safety. This paper presents a method for the simultaneous quantitative detection of these three drugs in hair by a europium nanoparticles-based fluorescence immunochromatographic assay (EuNPs-FIA). In our study, the test area of the nitrocellulose membrane was composed of three equally spaced detection lines and a quality control line. The test strip realized the quantitative analysis of the samples by detecting the fluorescence brightness of the europium nanoparticles captured on the test line within 15 min. For the triple test strip, the limits of detection of MOP, KET and MET were 0.219, 0.079 and 0.329 ng/mL, respectively. At the same time, it also showed strong specificity. The strip was stable and could be stored at room temperature for up to one year, and the average recovery rate was 85.98-115.92%. In addition, the EuNPs-FIA was validated by high-performance liquid chromatography (HPLC) analysis, and a satisfactory consistency was obtained. Compared to the current immunochromatographic methods used for detecting abused drugs in hair, this method not only increased the number of detection targets, but also ensured sensitivity, improving detection efficiency to a certain extent. The approach can also be used as an alternative to chromatography. It provides a rapid and accurate screening method for the detection of abused drugs in hair and has great application prospects in regard to public safety.

Portable biosensors for rapid on-site determination of cannabinoids in cannabis, a review

Recent studies highlight the therapeutic virtues of cannabidiol (CBD). Furthermore, due to their molecular enriched profiles, cannabis inflorescences are biologically superior to a single cannabinoid for the treatment of various health conditions. Thus, there is flourishing demand for Cannabis sativa varieties containing high levels of CBD. Additionally, legal regulations around the world restrict the cultivation and consumption of tetrahydrocannabinol (THC)-rich cannabis plants for their psychotropic effects. Therefore, the use of cannabis varieties that are high in CBD is permitted as long as their THC content does not exceed a low threshold of 0.3%-0.5%, depending on the jurisdiction. These chemovars are legally termed 'hemp'. This controlled cannabinoid requirement highlights the need to detect low levels of THC, already in the field. In this review, cannabis profiling and the existing methods used for the detection of cannabinoids are firstly evaluated. Then, selected valuable biosensor technologies are discussed, which suggest portable, rapid, sensitive, reproducible, and reliable methods for on-site identification of cannabinoids levels, mainly THC. Recent cutting-edge techniques of promising potential usage for both cannabis and hemp analysis are identified, as part of the future cultivation and agricultural improvement of this crop.

Machine Learning-Based Quantification of (-)-trans-Δ-Tetrahydrocannabinol from Human Saliva Samples on a Smartphone-Based Paper Microfluidic Platform

(-)-trans-Δ-Tetrahydrocannabinol (THC) is a major psychoactive component in cannabis. Despite the recent trends of THC legalization for medical or recreational use in some areas, many THC-driven impairments have been verified. Therefore, convenient, sensitive, quantitative detection of THC is highly needed to improve its regulation and legalization. We demonstrated a biosensor platform to detect and quantify THC with a paper microfluidic chip and a handheld smartphone-based fluorescence microscope. Microfluidic competitive immunoassay was applied with anti-THC-conjugated fluorescent nanoparticles. The smartphone-based fluorescence microscope counted the fluorescent nanoparticles in the test zone, achieving a 1 pg/mL limit of detection from human saliva samples. Specificity experiments were conducted with cannabidiol (CBD) and various mixtures of THC and CBD. No cross-reactivity to CBD was found. Machine learning techniques were also used to quantify the THC concentrations from multiple saliva samples. Multidimensional data were collected by diluting the saliva samples with saline at four different dilutions. A training database was established to estimate the THC concentration from multiple saliva samples, eliminating the sample-to-sample variations. The classification algorithms included k-nearest neighbor (k-NN), decision tree, and support vector machine (SVM), and the SVM showed the best accuracy of 88% in estimating six different THC concentrations. Additional validation experiments were conducted using independent validation sample sets, successfully identifying positive samples at 100% accuracy and quantifying the THC concentration at 80% accuracy. The platform provided a quick, low-cost, sensitive, and quantitative point-of-care saliva test for cannabis.

Smartphone-based paper microfluidic competitive immunoassay for the detection of α-amanitin from mushrooms

α-Amanitin is often considered the most poisonous mushroom toxin produced by various mushroom species, which are hard to identify from edible, non-toxic mushrooms. Conventional detection methods require expensive and bulky equipment or fail to meet high analytical sensitivity. We developed a smartphone-based fluorescence microscope platform to detect α-amanitin from dry mushroom tissues. Antibody-nanoparticle conjugates were captured by immobilized antigen-hapten conjugates while competing with the free analytes in the sample. Captured fluorescent nanoparticles were excited at 460 nm and imaged at 500 nm. The pixel numbers of such nanoparticles in the test zone were counted, showing a decreasing trend with increasing analyte concentration. The detection method exhibited a low detection limit (1 pg/mL), high specificity, and selectivity, allowing us to utilize a simple rinsing for toxin extraction and avoiding the need for high-speed centrifugation. In addition, this assay's short response time and portable features enable field detection of α-amanitin from amanitin-producing mushrooms.

Early detection of cannabinoids in biological samples based on their affinity interaction with the growth hormone secretagogue receptor

Herein we report on the early detection of cannabinoids in urine samples according to their affinity profiles in competitive assays with labelled ghrelin (GHR). We have demonstrated for the first time that cannabidiol (CBD) and 11-nor-Δ⁹-tetrahydrocannabinol-9-carboxylic acid (carboxy-THC) act as extracellular ligands for the growth hormone secretagogue receptor (GHS-R1a), strongly promoting the binding of ghrelin (GHR), the endogenous ligand of GHS-R1a. The affinity profiles of CBD and carboxy-THC are significantly different from the profiles of synthetic GHR mimetics such as CJC-1295 or [D-Arg¹-D-Phe⁵-D-Trp^7,9-Leu¹¹]-Substance P peptides, which are the most common interferents; the cannabinoids promoted the GHR/GHS-R1a interaction, while the ghrelin mimetics acted rather as competitive inhibitors. The analysis of 1:4 diluted urine samples proved that the proposed method displays good linearity and sensitivity in the range of 5-30 ng/mL for both CBD and carboxy-THC, whereas GHR mimetics display no interference at concentrations up to 100 ng/mL. The results were validated by comparison with the gas chromatography tandem mass spectrometry reference method. CBD may exert the same promoting effect on the interaction of GHS-R1a with other GHR mimetics listed as performance-enhancing substances.

A biomolecule-free electrochemical sensing approach based on a novel electrode modification technique: Detection of ultra-low concentration of Δ⁹-tetrahydrocannabinol in saliva by turning a sample analyte into a sensor analyte

Cannabis is currently one of the most consumed drugs in many countries. Δ⁹-tetrahydrocannabinol (THC) is the principal psychoactive component of this drug and is present in saliva after consumption. This paper reports a novel biomolecule-free electrochemical approach to detect an ultra-low level of THC in saliva using modified electrodes with molecules of the same analyte (THC) that are detected later via square wave voltammetry. The results from this research revealed that the electrodeposition of THC on the working electrode (sensor analyte) could highly enhance the limit of detection by improving the affinity of the THC molecules present in the sample (sample analyte) to the sensing electrode surface. Detailed descriptions about the optimization of the sensor and its performance in simple media, such as PBS, and complex media, such as simulated and real saliva, are provided. This novel and yet simple electrochemical-based sensing strategy allowed for a low limit of detection of 1.6 ng/mL THC in simulated and real saliva, distinguishing concentrations ranging from 2 to 25 ng/mL, making this technology viable for a real-world application such as roadside testing.

Immunoassay of SARS-CoV-2 nucleocapsid proteins using novel red emission-enhanced carbon dot-based silica spheres

It is imminent to develop a new type of rapid COVID-19 detection method with high sensitivity. Here, we used novel red emission-enhanced carbon dot (CD)-based silica (RCS) spheres as the signals of lateral flow immunochromatography (LFI) to ultrasensitively detect novel severe acute respiratory syndrome coronavirus 2 nucleocapsid proteins (SARS-CoV-2 NPs). The red emission of CDs can be enhanced and enriched in silica spheres by a simple way. The amino ends of the N-β-(aminoethyl)-γ-aminopropyltrimethoxy anchor carboxyl-rich CDs and enhance the red emission, while the other end is embedded in the silica carrier. Then, the composite silica spheres werecoated with 3-(triethylsilyl) propylamine to protect the CDs, promote bioconjugation and obtain RCS spheres. The optimal emission peaks of the aqueous solution and the solid state of RCS spheres were at 634 nm and 638 nm, respectively, with quantum yields (QYs) of 48.5% and 35.7%, respectively. Their red emission has a wide excitation range (from the ultraviolet region to the red region), and the best excitation wavelength is about 580 nm. Two fluorescence detection modes of the RCS-LFI technology for the SARS-CoV-2 NP assay are available: the simple mode of observation under ultraviolet light has a sensitivity of 100 pg mL-1; the advanced mode of detection under a fluorescence microscope has a sensitivity of 10 pg mL-1. This assay also exhibits the advantages of fast detection speed, high specificity, and simple operation. In addition, the feasibility of this method in actual sample detection was verified in human serum by the standard-addition method, and the results show that the method has excellent practicability. We believe that this method will be a valuable supplement for the diagnosis of COVID-19.

Ten Years of Lateral Flow Immunoassay Technique Applications: Trends, Challenges and Future Perspectives

The Lateral Flow Immunoassay (LFIA) is by far one of the most successful analytical platforms to perform the on-site detection of target substances. LFIA can be considered as a sort of lab-in-a-hand and, together with other point-of-need tests, has represented a paradigm shift from sample-to-lab to lab-to-sample aiming to improve decision making and turnaround time. The features of LFIAs made them a very attractive tool in clinical diagnostic where they can improve patient care by enabling more prompt diagnosis and treatment decisions. The rapidity, simplicity, relative cost-effectiveness, and the possibility to be used by nonskilled personnel contributed to the wide acceptance of LFIAs. As a consequence, from the detection of molecules, organisms, and (bio)markers for clinical purposes, the LFIA application has been rapidly extended to other fields, including food and feed safety, veterinary medicine, environmental control, and many others. This review aims to provide readers with a 10-years overview of applications, outlining the trends for the main application fields and the relative compounded annual growth rates. Moreover, future perspectives and challenges are discussed.

Fast detection of E. coli with a novel fluorescent biosensor based on a FRET system between UCNPs and GO@Fe3O4 in urine specimens

Biosensors based on nanomaterials are becoming a research hotspot for the rapid detection of pathogenic bacteria. Herein, a "turn-on" fluorescent biosensor based on a FRET system was constructed for the fast detection of a representative pathogenic microorganism, namely, E. coli, which causes most urinary tract infections. This biosensor was constructed by utilizing synthesized UCNPs as fluorescent donors with stable luminescence performance in complex biological samples and GO@Fe3O4 as a receptor with both excellent adsorption ability and fluorescence quenching ability. A specific ssDNA selected as an aptamer which could recognize E. coli was immobilized on the UCNPs to form UCNP-Apt nanoprobes. The nanoprobes were adsorbed on the surface of GO@Fe3O4 through the π-stacking interactions between aptamers and GO. In the presence of E. coli, UCNP-Apt nanoprobes detached from GO@Fe3O4 due to the specific recognition of aptamers and bacteria, resulting in obvious fluorescence recovery, and the concentration of bacteria was positively correlated with the intensity of the fluorescence signal; such a "turn-on" signal output mode ensures excellent precision. In addition, the easy magnetic separation of GO@Fe3O4 simplifies the operation process, helping the sensor detect bacteria in 30 minutes with a linear range from 103 to 107 CFU mL-1 and a limit of detection of 467 CFU mL-1. Moreover, recovery test results also showed that the sensor has clinical application potential for the rapid detection of pathogenic microorganisms in complex biological samples.