Fast, Sensitive, and Quantitative Point-of-Care Platform for the Assessment of Drugs of Abuse in Urine, Serum, and Whole Blood

Cannabis detection with solid sensors and paper-based immunoassays by conjugating antibodies to nanocellulose

Highly sensitive and specific diagnostics for cannabis usage are essential for rapid on-site screening for illicit drug usage. To improve the sensitivity of THC immunoassays, a proper immobilization of the sensing elements on the sensor substrate is critical. In this work, we demonstrated the utilization of EDC/NHS coupling chemistry with nanocellulose to obtain efficient anchor layers for the immobilization of anti-immune complex antibodies on surfaces. In our approach, the high surface-to-volume ratio, OH-group-rich surface, and high hygroscopicity of TOCNF enable efficient surface functionalization and enhance water permeation inside the nanocellulose network structure, offering a hydrophilic spacer for the sensing antibodies. THC detection was shown in both SPR (surface plasmon resonance technique) and paper-based sensing systems. In SPR, antibody immobilization and the related interactions with the target molecule complex with 1-10 μg/mL THC were followed in-situ in aqueous environment, revealing robust attachment of the antibody to the nanocellulose layer and preserved bioactivity. Additionally, quantitative THC detection was enabled on paper substrate by colorimetric means by employing labeled anti-THC Fab antibody fragments as detection antibodies. THC detection efficiency of covalently linked biointerface was superior compared to the performance of physically linked biointerface. The chemical conjugation of anti-IC to nanocellulose allowed efficient binding, whereas supramolecular conjugation led to insufficient binding, highlighting the relevance of the developed nanocellulose-based anchor layer.

Technologies for Frugal and Sensitive Point-of-Care Immunoassays

Immunoassays are a powerful tool for sensitive and quantitative analysis of a wide range of biomolecular analytes in the clinic and in research laboratories. However, enzyme-linked immunosorbent assay (ELISA)-the gold-standard assay-requires significant user intervention, time, and clinical resources, making its deployment at the point-of-care (POC) impractical. Researchers have made great strides toward democratizing access to clinical quality immunoassays at the POC and at an affordable price. In this review, we first summarize the commercially available options that offer high performance, albeit at high cost. Next, we describe strategies for the development of frugal POC assays that repurpose consumer electronics and smartphones for the quantitative detection of analytes. Finally, we discuss innovative assay formats that enable highly sensitive analysis in the field with simple instrumentation.

Gas-propelled biosensors for quantitative analysis

Gas-propelled biosensors display a simple gas-based signal amplification with quantitative detection features based on the target recognition event in combination with gas propulsion. Due to the liquid-gas conversion, the gas not only pushes the ink bar forward in the microchannel, but also serves as the power to propel the micromotors in the liquid. Thus, this continuous motion leads to a shift in distances which is associated with the target amount. Therefore, gas-propelled biosensors provide a visual quantification based on distance or speed signals without the need for expensive instruments. In this review, we focus on current developments in gas-propelled biosensors for quantitative analysis. First, we list the types of gas utilized as actuators in biosensors. Second, we review the representative gas-propelled biosensors, including the propulsion mechanisms and fabrication methods. Moreover, gas-propelled quantification based on distance and speed is summarized. Finally, we cover applications and provide a future perspective of gas-propelled biosensors.

Point-of-Care Drug of Abuse Testing in the Opioid Epidemic

CONTEXT.—

The United States is experiencing an opioid overdose epidemic. Point-of-care (POC) drug of abuse testing is a useful tool to combat the intensified opioid epidemic.

OBJECTIVES.—

To review commercially available POC drug of abuse testing involving opioids, to review opportunities and challenges for POC opioid testing and emerging testing methods in research literature, and finally to summarize unmet clinical needs and future development prospects.

DATA SOURCES.—

The Google search engine was used to access information for commercial opioid POC devices and the Google Scholar search engine was used to access research literature published from 2000 to 2019 for opioid POC tests.

CONCLUSIONS.—

The opioid epidemic provides unprecedented opportunities for POC drug testing, with significant clinical needs. Compared with gold standard tests, limitations for commercially available opioid POC testing include lower analytical sensitivity, lower specificity, and cross-reactivity. In response to unmet clinical needs, novel methods have emerged in research literature, such as microfluidics and miniature mass spectrometry. Future prospects include the development of quantitative POC devices and smarter and real-time drug testing.

Phenotype-related drug sensitivity analysis of single CTCs for medicine evaluation

Due to the heterogeneous and variable drug sensitivity of tumor cells, real-time monitoring of a patient's drug response is desirable for implementing personalized and dynamic therapy. Although considerable efforts have been directed at drug screening in living cells, performing repeated drug sensitivity analysis using patient-derived primary tumor cells at the single-cell level remains challenging. Here, we present an efficient approach to assess phenotype-related drug sensitivity at the single-cell level using patient-derived circulating tumor cells (CTCs) based on a drug sensitivity microfluidic chip (DS-Chip). The DS-Chip consists of a drug gradient generator and parallel cell traps, achieving continuous single CTC capture, drug gradient distributions, drug stimulation, fluorescent probe labeling and three-color fluorescence imaging. Based on the established DS-Chip, we investigated the drug sensitivity of single cells by simultaneously monitoring epithelial–mesenchymal transition (EMT) biomarkers and apoptosis in living cells, and verified the correlation between EMT gradients and drug sensitivity. Using the new approach, we further tested the optimal drug response dose in individual CTCs isolated from 5 cancer patients through fluorescence analysis of EMT and apoptosis. The DS-Chip allows noninvasive and real-time measurements of the drug sensitivity of a patient's tumor cells during therapy. This developed approach has practical significance and can effectively guide drug selection and therapeutic evaluation for personalized medicine.

Due to the heterogeneous and variable drug sensitivity of tumor cells, real-time monitoring of a patient's drug response is desirable for implementing personalized and dynamic therapy.

Naked-eye based point-of-care detection of E.coli O157: H7 by a signal-amplified microfluidic aptasensor

Fast and sensitive detection of E.coli O157: H7 is significantly essential for clinical management as well as for transmission prevention during disease outbreaks. Though many types of detection strategies have been implemented for measuring E.coli O157: H7, most of them still rely on complex instruments or tedious/laborious setups, which restrict their applications in resource-limited scenarios. Herein, we introduce an eye-based microfluidic aptasensor (EA-Sensor) for fast detection of E.coli O157: H7 without the assist of any instruments. We demonstrate the perfect coupling of aptamer sensing, hybridization chain reaction (HCR)-amplification and a distance-based visualized readout to quantitatively determine the pathogen concentration. We first used gel-electrophoresis assay to evaluate the system and the results proved that E.coli O157: H7 was well recognized by the aptamer and HCR could increase the signal by about 100 folds. In addition, the Aptamer specificity and signal-amplification ability were verified on the EA-Sensor for sensing E.coli O157: H7 by naked eyes. Furthermore, we demonstrated that E.coli O157: H7 in milk could be accurately and conveniently measured with good performance. With the benefits of operation integration and strategy integration, our EA-Sensor shows advantages of high specificity, easy operation, efficient amplification and visualized readout, which offers a favorable point-of-care tool for E.coli O157: H7 or other pathogen detection in resource-constrained settings.

Microfluidics-Implemented Biochemical Assays: From the Perspective of Readout

Over the past decades, microfluidics has emerged as an increasingly important tool to perform biochemical assays for diagnosis and healthcare. The precise fluid control and molecule manipulation within microfluidics greatly contribute to developing assays with simplicity and convenience. The advantages of microfluidics, including decreased consumption of reagents and samples, lower operating and analysis time, much lower cost, and higher integration and automation over traditional systems, offer a great platform to meet the needs of point-of-care applications. In this Review, versatile strategies are outlined and recent advances in microfluidics-implemented assays are discussed from the perspective of readout, because a convenient and straightforward readout is what a biochemical assay requires and the end user desires. Functions and properties arising from each readout are reviewed and the advantages and limitations of each readout are discussed together with current challenges and future perspectives.

FRET-Created Traffic Light Immunoassay Based on Polymer Dots for PSA Detection

There have been enormous efforts for developing the next generations of fluorometric lateral flow immunochromatographic strip (ICTS) owing to the great advances in fluorescent materials in these years. Here we developed one type of fluorometric ICTS based on ultrabright semiconducting polymer dots (Pdots) in which the traffic light-like signals were created by energy transfer depending on the target concentration. This platform was successfully applied for qualitatively rapid screening and quantitatively precise analysis of prostate-specific antigen (PSA) in 10 min from merely one drop of the whole blood sample. This FRET-created traffic light ICTS possesses excellent specificity and an outstanding detection sensitivity of 0.32 ng/mL for PSA. Moreover, we conducted proof-of-concept experiments to demonstrate its potential for multiplexed detection of cancer biomarkers at the same time in an individual test strip by taking advantage of the traffic light signals. To the best of our knowledge, it is the first model of a traffic light-like immunoassay test strip based on Pdots with multiplexing ability. These results would pave an avenue for designing the next generation of point-of-care diagnostics.

Microfluidic triple-gradient generator for efficient screening of chemical space

Generation of a combinatorial gradient for multiple chemicals is essential for studies of biochemical stimuli, chemoattraction, protein crystallization and others. While currently available platforms require complex design/settings to obtain a double-gradient chemical matrix, we herein report for the first time a simple triple-gradient matrix (TGM) device for efficient screening of chemical space. The TGM device is composed of two glass slides and works following the concept of SlipChip. The device utilizes XYZ space to distribute three chemicals and establishes a chemical gradient matrix within 5 min. The established matrix contains 24 or 104 screening conditions depending on the device used, which covers a concentration range of [0.117-1, 0.117-1 and 0.686-1] and [0.0830-1, 0.0830-1, 0.686-1] respectively for the three chemicals. With the triple gradients built simultaneously, this TGM device provides order-of-magnitude improvement in screening efficiency over existing single- or double-gradient generators. As a proof of concept, we applied the device to screen the crystallization conditions for two model proteins of lysozyme and trypsin and confirmed the crystal structures using X-ray diffraction. Furthermore, we successfully obtained the crystallization condition of adhesin competence repressor, a protein that senses the alterations in intracellular zinc concentrations. We expect the TGM system to be widely used as an analytical platform for material synthesis and chemical screening beyond for protein crystallization.

Lateral flow assay ruler for quantitative and rapid point-of-care testing

Lateral flow assay (LFA) is a well-established platform for point-of-care (POC) testing due to its low cost and user friendliness. Conventional LFAs provide qualitative or semi-quantitative results and require dedicated instruments for quantitative detection. Here, we developed an "LFA ruler" for quantitative and rapid readout of LFA results, using a 3D printed strip cassette and a simple, inexpensive microfluidic chip. Platinum nanoparticles are used as signal amplification reporters, which catalyze the generation of oxygen to push ink advancement in the microfluidic channel. The concentration of the target is linearly correlated with the ink advancement distance. The entire assay can be completed within 30 minutes without external instruments and complicated operations. We demonstrated quantitative prostate specific antigen testing using the LFA ruler, with a limit of detection of 0.54 ng mL^-1, linear range of 0-12 ng mL^-1, and high correlation with a clinical gold standard assay. The LFA ruler achieves low cost, quantitative, sensitive and rapid detection, which has great potential in POC testing and can be extended to quantify other disease biomarkers.

Colorimetric and Fluorescent Dual-Mode Immunoassay Based on Plasmon-Enhanced Fluorescence of Polymer Dots for Detection of PSA in Whole Blood

Although enormous efforts have been devoted to the development of new types of fluorometric immunochromatographic test strip (ICTS) with improved sensitivity over the past years, it still remains a big challenge to design ICTS with colorimetric and fluorescent bimodal signal readout for rapid yet accurate detection of cancer markers in a clinic. Scientists have tried to prepare bimodal reporters by combining fluorescent dyes with metal nanomaterials, but their fluorescence was easily quenched by metal nanomaterials through surface energy transfer, making dual colorimetric and fluorometric ICTS very difficult to be achieved. As compared to conventional fluorescent probes, semiconducting polymer dots (Pdots) exhibit extraordinary fluorescence brightness and facile surface functionalization, which are very suitable to be engineered as bimodal signal reporting reagents. Here, we integrated highly fluorescent Pdots with strongly plasmonic Au nanorods to form Pdot-Au hybrid nanocomposites with dual colorimetric and fluorescent readout abilities. We further utilized these nanohybrids in ICTS for qualitatively fast screening (colorimetry) as well as quantitatively accurate determination (fluorometry) of prostate-specific antigen (PSA) within 10 min. By taking advantage of the plasmon-enhanced fluorescence of Pdots on Au nanorods, this immunoassay possesses much better detection sensitivity of 1.07 pg/mL for PSA, which is at least 2 orders of magnitude lower than that of conventional fluorometric ICTS. Moreover, the direct detection of PSA from human whole blood collected without sample pretreatment makes this Pdot-based ICTS platform promising for on-site point-of-care diagnostics.

Chromogenic and Fluorogenic Probes for the Detection of Illicit Drugs

The consumption of illicit drugs has increased exponentially in recent years and has become a problem that worries both governments and international institutions. The rapid emergence of new compounds, their easy access, the low levels at which these substances are able to produce an effect, and their short time of permanence in the organism make it necessary to develop highly rapid, easy, sensitive, and selective methods for their detection. Currently, the most widely used methods for drug detection are based on techniques that require large measurement times, the use of sophisticated equipment, and qualified personnel. Chromo- and fluorogenic methods are an alternative to those classical procedures.

Applications of liquid-based separation in conjunction with mass spectrometry to the analysis of forensic evidence

In the past few years, there has been a significant effort by the forensic science community to develop new scientific techniques for the analysis of forensic evidence. Forensic chemists have been spearheaded to develop information-rich confirmatory technologies and techniques and apply them to a broad array of forensic challenges. The purpose of these confirmatory techniques is to provide alternatives to presumptive techniques that rely on data such as color changes, pattern matching, or retention time alone, which are prone to more false positives. To this end, the application of separation techniques in conjunction with mass spectrometry has played an important role in the analysis of forensic evidence. Moreover, in the past few years the role of liquid separation techniques, such as liquid chromatography and capillary electrophoresis in conjunction with mass spectrometry, has gained significant tractions and have been applied to a wide range of chemicals, from small molecules such as drugs and explosives, to large molecules such as proteins. For example, proteomics and peptidomics have been used for identification of humans, organs, and bodily fluids. A wide range of HPLC techniques including reversed phase, hydrophilic interaction, mixed-mode, supercritical fluid, multidimensional chromatography, and nanoLC, as well as several modes of capillary electrophoresis mass spectrometry, including capillary zone electrophoresis, partial filling, full filling, and micellar electrokenetic chromatography have been applied to the analysis drugs, explosives, and questioned documents. In this article, we review recent (2015-2017) applications of liquid separation in conjunction with mass spectrometry to the analysis of forensic evidence.

Hand-powered centrifugal microfluidic platform inspired by the spinning top for sample-to-answer diagnostics of nucleic acids

Point-of-care (POC), sample-to-answer and electricity-free nucleic acid diagnostic tools are vital for health care and disease control in resource-limited settings where centralized medical facilities or even electric power may remain unreliable. Inspired by one of the oldest recognizable toys, the spinning top, here we report a fully hand-powered centrifugal microfluidic platform for the diagnostics of pathogenic bacteria. Assay procedures such as zeolite-based purification of nucleic acids, loop-mediated isothermal amplification (LAMP) and visual detection of fluorescence signals are integrated into a single microfluidic disc. A simple pull-out operation of the top rack of the customized centrifuge initiates high-speed rotation of the disc, resulting in efficient actuation and mixing of preloaded sample/reagent fluids. This microfluidic platform enables the simultaneous detection of six kinds of pathogenic bacteria within a small disc in an electricity-free manner, showing great promise in sample-to-answer nucleic acid detection in remote settings.

Gas-generating reactions for point-of-care testing

Gas generation-based measurement is an attractive alternative approach for POC (Point-of-care) testing, which relies on the amount of generated gas to detect the corresponding target concentrations.