Point-of-care detection of Monkeypox virus clades using high-performance upconversion nanoparticle-based lateral flow assay.

There is an urgent need for a point-of-care testing (POCT) method in developing and underserved regions to distinguish between two Monkeypox virus (MPXV) clades, given their varying transmissibility and clinical manifestations. In this paper, we target the specific complement protein gene fragment of two MPXV clades and construct a high-performance upconversion nanoparticles-based lateral flow assay (UCNPs-based LFA) with double T-lines and a shared C-line. This enables qualitative and quantitative dual-mode detection when combined with a smartphone and a benchtop fluorescence analyzer. The developed LFA exhibits stable performance, convenient operation, rapid readout (within 8 min), and a much lower limit of detection (LOD) (~ pM level) compared to existing POCT methods. The proposed detection platform demonstrates significant potential for pathogen diagnosis using a POCT approach.

Hydrogel-assisted microfluidic spinning of stretchable fibers via fluidic and interfacial self-adaptations.

Stretchable polymeric fibers have enormous potential, but their production requires rigorous environmental controls and considerable resource consumption. It's also challenging for elastic polymers with high performance but poor spinnability, such as silicones like polydimethylsiloxane and Ecoflex. We present a hydrogel-assisted microfluidic spinning (HAMS) method to address these challenges by encapsulating their prepolymers within arbitrarily long, protective, and sacrificable hydrogel fibers. By designing simple apparatuses and manipulating the fluidic and interfacial self-adaptations of oil/water flows, we successfully produce fibers with widely controllable diameter (0.04 to 3.70 millimeters), notable length, high quality (e.g., smooth surface, whole-length uniformity, and rounded section), and remarkable stretchability (up to 1300%) regardless of spinnability. Uniquely, this method allows an easy, effective, and controllable reshaping production of helical fibers with exceptional stretchability and mechanical compliance. We deeply reveal the mechanisms in producing these fibers and demonstrate their potential as textile components, optoelectronic devices, and actuators. The HAMS method would be a powerful tool for mass-producing high-quality stretchable fibers.

Regulation of probe density on upconversion nanoparticles enabling high-performance lateral flow assays.

Upconversion nanoparticles (UCNPs)-based fluorescence probes have shown great potential in point-of-care testing (POCT) applications, due to UCNPs' features of high photostability and background-free fluorescence. Ceaseless improvements of UCNPs-probes have been carried out to increase detection sensitivity and to broaden detection range of UCNPs-based POCT. In this paper, we optimized UCNPs-probes by regulating probe density. The optimization was verified by a traditional lateral flow assay (LFA) platform for C-reactive protein (CRP) detection. Further, the optimized UCNPs-LFA integrating with a home-made benchtop fluorescence analyzer holds the capability to achieve high-performance POCT. Finally, nearly a 20 times sensitivity enhancement with a limit of detection of 0.046 ng/mL and a broad detection range of 0.2-300 ng/mL for CRP detection was obtained. Moreover, the optimized UCNPs-LFA was applied to detecting CRP in clinical serum samples and the detection results were consistent with the clinical test, validating its clinical practicability. The proposed optimization method is also expected to optimize other nanoparticles-based bio-probes for wider POCT application.

Eu-Chelate Polystyrene Microsphere-Based Lateral Flow Immunoassay Platform for hs-CRP Detection.

Inflammation caused by viral or bacterial infection is a major threat to human health globally. Blood C-reactive protein (CRP) has been proven to be a sensitive indicator for the occurrence and development of inflammation. Furthermore, a tiny change of blood CRP concentration may portend chronic diseases; therefore, high-sensitivity CRP (hs-CRP) detection in a quantitative, rapid, user-friendly, and low-cost manner is highly demanded. In this paper, we developed a europium-chelate polystyrene microsphere (EuPSM)-based lateral flow immunoassay (LFIA) integrating with a benchtop fluorescence analyzer for hs-CRP detection. The optimization of the EuPSM-based LFIA was implemented through adjusting the antibody density on EuPSM from 100% to 60% of the saturated density. Finally, the limit of detection of 0.76 pg/mL and detection range of 0.025-250 ng/mL were obtained. Moreover, the clinical application capability of the proposed platform was validated through detecting CRP in clinical serum samples, showing high consistency with the results obtained from the clinical standard method. Hence, the proposed EuPSM-based LFIA has been verified to be well suitable for hs-CRP detection, while also showing great applicability for sensitively and rapidly detecting other biomarkers.

Upconversion fluorescence-based paper disc for multiplex point-of-care testing in water quality monitoring.

Water quality monitoring is of great significance for human health, which involves a large number of distinct targets detection, such as pathogens, heavy metal ions, and toxins. Traditional detection methods usually carried out in well-equipped central labs are subjected to time, labor, and expense consumption, thus not suitable for implementing water quality monitoring at point of care, where the detection implemented on a multiplexed, miniaturized, and simplified device with rapid and sensitive answer out is desired. To this end, we developed a paper disc relying on upconversion fluorescence signal and aptamer recognition probes for multiplex detection of water contaminants with high sensitivity and specificity. Finally, several different typical kinds of water contaminants have been successfully detected on our paper disc with limit of detection of 115 cfu/mL for Salmonella, 3 ng/mL for Ochratoxin A and Microcystin-LR, 20 nM for Hg2+ and 4 nM for Pb2+, respectively. Additionally, we designed a compact smartphone-based reading device to enable water quality monitoring at point-of-care. Furthermore, this paper disc-based detection platform can be extended to apply to multiplex detection for disease diagnosis and food safety monitoring.

Recombinase polymerase amplification integrated with microfluidics for nucleic acid testing at point of care.

Nucleic acid testing (NAT) implemented on a portable, miniaturized, and integrated device with rapid and sensitive results readout is highly demanded for pathogen detection or genetic screening at resource-limited settings, especially after the outbreak of coronavirus disease 2019 (COVID-19). The integration of recombinase polymerase amplification (RPA) with emerging microfluidics, classified by paper-based microfluidics and chip-based microfluidics, shows great potential to perform laboratory independent NAT assays at point of care with minimal labor, time and energy consumption. This review summarizes the state-of-the-art of RPA integrated with paper-based microfluidics and chip-based microfluidics, and discusses their pros and cons. Finally, existing challenges and possible ways for optimization of microfluidics-based RPA are proposed.

Paper-based point-of-care test with xeno nucleic acid probes.

Bridging the unmet need of efficient point-of-care testing (POCT) in biomedical engineering research and practice with the emerging development in artificial synthetic xeno nucleic acids (XNAs), this review summarized the recent development in paper-based POCT using XNAs as sensing probes. Alongside the signal transducing mode and immobilization methods of XNA probes, a detailed evaluation of probe performance was disclosed. With these new aspects, both researchers in synthetic chemistry / biomedical engineering and physicians in clinical practice could gain new insights in designing, manufacturing and choosing suitable reagents and techniques for POCT.

A portable and universal upconversion nanoparticle-based lateral flow assay platform for point-of-care testing.

Upconversion nanoparticle-based lateral flow assays (UCNP-LFAs) have attracted significant attention in point-of-care testing (POCT) applications, due to the long-term photostability and enhanced signal-to-background noise ratio. The existing UCNP-LFAs generally require peripheral equipment for exciting fluorescent signals and reading out fluorescence results, which are generally bulky and expensive. Herein, we developed a miniaturized and portable UCNP-LFA platform, which is composed of a LFA detection system, an UCNP-LFA reader and a smartphone-assisted UCNP-LFA analyzer. The LFA detection system is based on three types of UCNPs for multiplexed detection. The reader has a dimension of 24.0 cm × 9.4 cm × 5.4 cm (L × W × H) and weight of 0.9 kg. The analyzer based on the custom-designed software of a smartphone (termed as UCNP-LFA analyzer) can get the quantitative analysis results in a real-time manner. We demonstrated the universality of this platform by highly sensitive and quantitative detections of several kinds of targets, including small molecule (ochratoxin A, OTA), heavy metal ion (Hg2+), bacteria (salmonella, SE), nucleic acid (hepatitis B virus, HBV) and protein (growth stimulation expressed gene 2, ST-2). Our developed UCNP-LFA platform holds great promise for applications in disease diagnostics, environmental pollution monitoring and food safety at the point of care.

Upconversion nanoparticles based FRET aptasensor for rapid and ultrasenstive bacteria detection.

Pathogenic bacteria cause serious harm to human health, which calls for the development of advanced detection methods. Herein, we developed a novel detection platform based on fluorescence resonance energy transfer (FRET) for rapid, ultrasensitive and specific bacteria detection, where gold nanoparticles (AuNPs, acceptor) were conjugated with aptamers while upconversion nanoparticles (UCNPs, donor) were functionalized with corresponding complementary DNA (cDNA). The spectral overlap between UCNPs fluorescence emission and AuNPs absorption enables the occurrence of FRET when hybridizing the targeted aptamer and cDNA, causing upconversion fluorescence quenching. In the presence of target bacteria, the aptamers preferentially bind to bacteria forming a three-dimensional structure and thereby dissociate UCNPs-cDNA from AuNPs-aptamers, resulting in the recovery of upconversion fluorescence. Using the UCNPs based FRET aptasensor, we successfully detected Escherichia coli ATCC 8739 (as a model analyte) with a detection range of 5-106cfu/mL and detection limit of 3cfu/mL. The aptasensor was further used to detect E. coli in real food and water samples (e.g., tap/pond water, milk) within 20min. The novel UCNPs based FRET aptasensor could be used to detect a broad range of targets from whole cells to metal ions by using different aptamer sequences, holding great potential in environmental monitoring, medical diagnostics and food safety analysis.

Microbubble embedded with upconversion nanoparticles as a bimodal contrast agent for fluorescence and ultrasound imaging.

Bimodal imaging offers additional imaging signal thus finds wide spread application in clinical diagnostic imaging. Fluorescence/ultrasound bimodal imaging contrast agent using fluorescent dyes or quantum dots for fluorescence signal has emerged as a promising method, which however requires visible light or UV irradiation resulting in photobleaching, photo blinking,auto-fluorescence and limited tissue penetration depth. To surmount these problems, we developed a novel bimodal contrast agent using layer-by-layer assembly of up conversion nanoparticles onto the surface of microbubbles. The resulting microbubbles with average size of 2 µm provide enhanced ultrasound echo for ultrasound imaging and upconversion emission upon near infrared irradiation for fluorescence imaging. The developed bimodal contrast agent holds great potential to be applied in ultrasound target technique for targeted diseases diagnostics and therapy.