Upconversion Nanoparticles-Encoded Hydrogel Microbeads-Based Multiplexed Protein Detection

Development of structure-tailored and composite magnetic-fluorescent microspheres through the PRI method

Multifunctional micro- and nanoparticles have found their applications in fields like medicine, display materials, cosmetics, and so on. Advances in these fields have been demonstrated to need scalable uniformly sized, mass-produced, and structured spherical particles. In this work, we proposed structure-tailored and multifunctional composite polymeric microspheres with tunable diameter size, by using a versatile and scalable in-fiber particle fabrication through the Plateau-Rayleigh capillary instability method. The results show that the characteristic shapes of the luminescence spectra of CsPbBr3 remained similar before and after embedding in the microspheres. The luminescence intensity was stabilized at 85-90% of their original photoluminescence intensities over an extended period. Moreover, the photoluminescence lifetime of the fluorescent microspheres was increased by 9.03% compared to CsPbBr3. The X-ray diffraction results revealed that there was no change in the crystal structure of the dopants before and after the encapsulation. Also, precise magnetic manipulation of Janus microspheres was successfully demonstrated.

Research on high performance combustible gas concentration sensor based on pyramid beam splitter matrix

Combustible gas concentration detection faces challenges of increasing accuracy, and sensitivity, as well as high reliability in harsh using environments. The special design of the optical path structure of the sensitive element provides an opportunity to improve combustible gas concentration detection. In this study, the optical path structure of the sensitive element was newly designed based on the Pyramidal beam splitter matrix. The infrared light source was modulated by multi-frequency point signal superimposed modulation technology. At the same time, concentration detection results and confidence levels were calculated using the 4-channel combustible gas concentration detection algorithm based on spectral refinement. Through experiment, it is found that the sensor enables full-range measurement of CH4, at the lower explosive limit (LEL, CH4 LEL of 5%), the reliability level is 0.01 parts-per-million (PPM), and the sensor sensitivity is up to 0.5PPM. The sensor is still capable of achieving PPM-level detections, under extreme conditions in which the sensor's optical window is covered by 2/3, and humidity is 85% or dust concentration is 100mg/m3. Those improve the sensitivity, robustness, reliability, and accuracy of the sensor.

Injectable Nano-Micro Composites with Anti-bacterial and Osteogenic Capabilities for Minimally Invasive Treatment of Osteomyelitis

The effective management of osteomyelitis remains extremely challenging due to the difficulty associated with treating bone defects, the high probability of recurrence, the requirement of secondary surgery or multiple surgeries, and the difficulty in eradicating infections caused by methicillin-resistant Staphylococcus aureus (MRSA). Hence, smart biodegradable biomaterials that provide effective and precise local anti-infection effects and can promote the repair of bone defects are actively being developed. Here, a novel nano-micro composite is fabricated by combining calcium phosphate (CaP) nanosheets with drug-loaded GelMA microspheres via microfluidic technology. The microspheres are covalently linked with vancomycin (Van) through an oligonucleotide (oligo) linker using an EDC/NHS carboxyl activator. Accordingly, a smart nano-micro composite called "CaP@MS-Oligo-Van" is synthesized. The porous CaP@MS-Oligo-Van composites can target and capture bacteria. They can also release Van in response to the presence of bacterial micrococcal nuclease and Ca2+, exerting additional antibacterial effects and inhibiting the inflammatory response. Finally, the released CaP nanosheets can promote bone tissue repair. Overall, the findings show that a rapid, targeted drug release system based on CaP@MS-Oligo-Van can effectively target bone tissue infections. Hence, this agent holds potential in the clinical treatment of osteomyelitis caused by MRSA.

Research on High Performance Methane Gas Concentration Sensor Based on Pyramid Beam Splitter Matrix

Methane gas concentration detection faces the challenges of increasing accuracy and sensitivity, as well as high reliability in harsh environments. The special design of the optical path structure of the sensitive element provides an opportunity to improve methane gas concentration detection. In this study, the optical path structure of the sensitive element was newly designed based on the Pyramidal beam splitter matrix. The infrared light source was modulated by multi-frequency point-signal superimposed modulation technology. At the same time, concentration detection results and confidence levels were calculated using the four-channel methane gas concentration detection algorithm based on spectral refinement. Through the experiment, it was found that the sensor enables the full-range measurement of CH4; at the lower explosive limit (LEL, CH4 LEL of 5%), the reliability level is 0.01 parts-per-million (PPM), and the limit of detection is 0.5 ppm. The sensor is still capable of achieving PPM-level detections under extreme conditions in which the sensor's optical window is covered by two-thirds and humidity is 85% or dust concentration is 100 mg/m3. Those improve the sensitivity, robustness, reliability, and accuracy of the sensor.

Facile microfluidic synthesis of monodispersed size-controllable quantum dot (QD) microbeads using custom developed QD photoresist

Fluorescent microbeads (MBs) are widely used as next-generation biosensors for the detection of target chemicals at highly sensitive concentrations, and for imaging and tracking in vitro and in vivo. However, most known methods for producing fluorescent MBs require complicated multistep processes that result in low production rates. In this study, we report a method for fabricating micrometer-sized quantum dot microbeads (QD-MBs) using a microfluidic chip and specially designed QD photoresist (QD-PR). This on-demand lab-on-a-chip method yielded monodispersed QD-MBs ranging from 1.89 to 33 μm with a coefficient of variation of less than 10%. The size distribution of the fabricated QD-MBs was Gaussian with a peak around the mean diameter and a spread of sizes around the peak. Compared with nanoscale QDs, the fabricated QD-MBs showed no emission loss. The full-width at half-maximum of the emission peak of the QD-MBs was smaller than that of the colloidal QDs, indicating a more uniform distribution and a higher density of QDs within the MB structure. In addition, we investigated the microfluidic flow regime that yielded the most uniform and controllable QD-MB. The MBs in the dripping regime were spherical and monodisperse, with an excellent particle size distribution. In this study, we present a simple and effective strategy for producing QD-MBs with controllable sizes, which can be crucial in diverse fields such as biosensing, drug delivery, and imaging.

Fabrication of Chitosan/PEGDA Bionanocomposites for Enhanced Drug Encapsulation and Release Efficiency

Drug delivery systems (DDS) have evolved in the last decades with the development of hydrogels and particles. However, challenges such as high systemic uptake, side effects, low bioavailability, and encapsulation efficiency continue to be significant hurdles faced by such DDSs. Particles and hydrogels can be specifically designed for targeted DDSs to mitigate some of these problems. This study developed chitosan (Cs) particles (Ps) and composite films using poly(ethylene glycol) diacrylate (PEGDA) as a copolymer to encapsulate gentamicin (GtS) for drug delivery. We demonstrated that lysozyme degrades the chitosan β-1,4 glycosidic bonds to release GtS. PEGDA increased drug encapsulation efficiency by shielding the repelling forces of like charges between Cs and GtS. The data show that PEGDA does not hinder enzymatic degradation while increasing drug encapsulation efficiency and producing more homogeneous particles. Additionally, we utilized Michael's reaction to cross-link Cs, CsPs, and PEGDA to produce a film designed for drug delivery. The film is an anchor for CsPs to prevent premature drug release. The cross-linking of Cs and PEGDA does not affect lysozyme activity, and CsPs could successfully release GtS without affecting GtS activity.

Revisiting carboxylic group functionalization of silica sol-gel materials

The carboxylic chemical group is a ubiquitous moiety present in amino acids, a ligand for transition metals, a colloidal stabilizer, and a weak acidic ion-exchanger in polymeric resins and given this property, it is attractive for responsive materials or nanopore-based gating applications. As the number of uses increases, subtle requirements are imposed on this molecular group when anchored to various platforms for the functioning of an integrated chemical system. In this context, silica stands as an inert and multipurpose platform that enables the anchoring of multiple chemical entities combined through several orthogonal synthesis methods on the interface. Surface chemical modification relies on the use of organoalkoxysilanes that must meet the demand of tuned chemical properties; this, in turn, urges for innovative approaches for having an improved, but simple, organic toolbox. Starting from commonly available molecular precursors, several approaches have emerged: hydrosilylation, click thiol-ene additions, the use of carbodiimides or the reaction between cyclic anhydrides and anchored amines. In this review, we analyze the importance of the COOH groups in the area of materials science and the commercial availability of COOH-based silanes and present new approaches for obtaining COOH-based organoalkoxide precursors. Undoubtedly, this will attract widespread interest for the ultimate design of highly integrated chemical platforms.

Lanthanide-Doped Upconversion Nanoparticles: Exploring A Treasure Trove of NIR-Mediated Emerging Applications

Lanthanide-doped upconversion nanoparticles (UCNPs) possess the remarkable ability to convert multiple near-infrared (NIR) photons into higher energy ultraviolet-visible (UV-vis) photons, making them a prime candidate for several advanced applications within the realm of nanotechnology. Compared to traditional organic fluorophores and quantum dots (QDs), UCNPs possess narrower emission bands (fwhm of 10-50 nm), large anti-Stokes shifts, low toxicity, high chemical stability, and resistance to photobleaching and blinking. In addition, unlike UV-vis excitation, NIR excitation is nondestructive at lower power intensities and has high tissue penetration depths (up to 2 mm) with low autofluorescence and scattering. Together, these properties make UCNPs exceedingly favored for advanced bioanalytical and theranostic applications, where these systems have been well-explored. UCNPs are also well-suited for bioimaging, optically modulating chemistries, forensic science, and other state-of-the-art research applications. In this review, an up-to-date account of emerging applications in UCNP research, beyond bioanalytical and theranostics, are presented including optogenetics, super-resolution imaging, encoded barcodes, fingerprinting, NIR vision, UCNP-assisted photochemical manipulations, optical tweezers, 3D printing, lasing, NIR-II imaging, UCNP-molecule nanohybrids, and UCNP-based persistent luminescent nanocrystals.

Applications of upconversion nanoparticles in analytical and biomedical sciences: a review

Lanthanide-doped upconversion nanoparticles (UCNPs) have gained more attention from researchers due to their unique properties of photon conversion from an excitation/incident wavelength to a more suitable emission wavelength at a designated site, thus improving the scope in the life sciences field. Due to their fascinating and unique optical properties, UCNPs offer attractive opportunities in theranostics for early diagnostics and treatment of deadly diseases such as cancer. Also, several efforts have been made on emerging approaches for the fabrication and surface functionalization of luminescent UCNPs in optical biosensing applications using various infrared excitation wavelengths. In this review, we discussed the recent advancements of UCNP-based analytical chemistry approaches for sensing and theranostics using a 980 nm laser as the excitation source. The key analytical merits of UNCP-integrated fluorescence analytical approaches for assaying a wide variety of target analytes are discussed. We have described the mechanisms of the upconversion (UC) process, and the application of surface-modified UCNPs for in vitro/in vivo bioimaging, photodynamic therapy (PDT), and photothermal therapy (PTT). Based on the latest scientific achievements, the advantages and disadvantages of UCNPs in biomedical and optical applications are also discussed to overcome the shortcomings and to improve the future study directions. This review delivers beneficial practical information of UCNPs in the past few years, and insights into their research in various fields are also discussed precisely.

Nanomaterial-assisted microfluidics for multiplex assays

Simultaneous detection of different biomarkers from a single specimen in a single test, allowing more rapid, efficient, and low-cost analysis, is of great significance for accurate diagnosis of disease and efficient monitoring of therapy. Recently, developments in microfabrication and nanotechnology have advanced the integration of nanomaterials in microfluidic devices toward multiplex assays of biomarkers, combining both the advantages of microfluidics and the unique properties of nanomaterials. In this review, we focus on the state of the art in multiplexed detection of biomarkers based on nanomaterial-assisted microfluidics. Following an overview of the typical microfluidic analytical techniques and the most commonly used nanomaterials for biochemistry analysis, we highlight in detail the nanomaterial-assisted microfluidic strategies for different biomarkers. These highly integrated platforms with minimum sample consumption, high sensitivity and specificity, low detection limit, enhanced signals, and reduced detection time have been extensively applied in various domains and show great potential in future point-of-care testing and clinical diagnostics.

Self-Assembly of Upconversion Nanoparticles Based Materials and Their Emerging Applications

In the past few decades, significant progress of the conventional upconversion nanoparticles (UCNPs) based nanoplatform has been achieved in many fields, and with the development of nanoscience and nanotechnology, more and more complex situations need a UCNPs based nanoplatform having multifunctions for specific multimodal or multiplexed applications. Through self-assembly, different UCNPs or UCNPs with other materials could be combined together within an entity. It is more like an ideal UCNPs nanoplatform, a unique system with the properties defined by its individual components as well as by the morphology of the composite. Various designs can show their different desired properties depending on the application situation. This review provides a complete summary on the optimization of the synthesis method for the recently designed UCNPs assemblies and summarizes various applications, including dual-modality cell imaging, molecular delivery, detection, and programmed control therapy. The challenges and limitations the UCNPs assembly faces and the potential solutions in this field are also presented.

Development of an enhanced immunoassay based on protein nanoparticles displaying an IgG-binding domain and luciferase

Detection of small amounts of target molecules with high sensitivity is important for the diagnosis of many diseases, including cancers, and is particularly important to detect early stages of disease. Here, we report the development of a temperature-responsive fusion protein (ELP-DCN) comprised of an elastin-like polypeptide (ELP), poly-aspartic acid (D), antibody-binding domain C (C), and NanoLuc luciferase (N). ELP-DCN proteins form nanoparticles above a certain threshold temperature that display an antibody-binding domain and NanoLuc luciferase on their surface. ELP-DCN nanoparticles can be applied for enhancement of immunoassay systems because they provide more antibody-binding sites and an increased number of luciferase molecules, resulting in an increase in assay signal. Here, we report the detection of human serum albumin (HSA) as a model protein using anti-HSA and ELP-DCN proteins. Upon formation of ELP-DCN nanoparticles, the detection limit improved tenfold compared to the monomeric form of ELP-DCN.

Photoswitch-Based Fluorescence Encoding of Microspheres in a Limited Spectral Window for Multiplexed Detection

Fluorescence barcoding with multicolor fluorophores is limited by spectral crowding. Herein, we propose a fluorescence encoding method in a single-color channel with photoswitches. The photochromic naphthopyran was used to mediate the fluorescence of polystyrene microspheres through resonance energy transfer. The initial fluorescence intensity (F₀) and the fluorescence after UV light activation (F/F₀) were combined to generate hundreds of 2-dimensional barcodes. The coding capacity was further expanded with the different chemical kinetics of the photoswitches. The photoswitch-based fluorescence barcodes were applied to simultaneously and selectively detect the DNA sequences of COVID-19 (with related mutations) as a proof-of-concept for real applications. The compatibility with the state-of-the-art fluorescence microscopes and simple encoding and decoding make the method very attractive for multiplexed and high-throughput analyses.

Preparation of alginate hydrogel microparticles by gelation introducing cross-linkers using droplet-based microfluidics: a review of methods

This review examines the preparation of alginate hydrogel microparticles by using droplet-based microfluidics, a technique widely employed for its ease of use and excellent control of physicochemical properties, with narrow size distribution. The gelation of alginate is realized "on-chip" and/or "off-chip", depending on where cross-linkers are introduced. Various strategies are described and compared. Microparticle properties such as size, shape, concentration, stability and mechanical properties are discussed. Finally, we consider future perspectives for the preparation of hydrogel microparticles and their potential applications.

Microfluidic nanomaterials: From synthesis to biomedical applications

Microfluidic platforms gain popularity in biomedical research due to their attractive inherent features, especially in nanomaterials synthesis. This review critically evaluates the current state of the controlled synthesis of nanomaterials using microfluidic devices. We describe nanomaterials' screening in microfluidics, which is very relevant for automating the synthesis process for biomedical applications. We discuss the latest microfluidics trends to achieve noble metal, silica, biopolymer, quantum dots, iron oxide, carbon-based, rare-earth-based, and other nanomaterials with a specific size, composition, surface modification, and morphology required for particular biomedical application. Screening nanomaterials has become an essential tool to synthesize desired nanomaterials using more automated processes with high speed and repeatability, which can't be neglected in today's microfluidic technology. Moreover, we emphasize biomedical applications of nanomaterials, including imaging, targeting, therapy, and sensing. Before clinical use, nanomaterials have to be evaluated under physiological conditions, which is possible in the microfluidic system as it stimulates chemical gradients, fluid flows, and the ability to control microenvironment and partitioning multi-organs. In this review, we emphasize the clinical evaluation of nanomaterials using microfluidics which was not covered by any other reviews. In the future, the growth of new materials or modification in existing materials using microfluidics platforms and applications in a diversity of biomedical fields by utilizing all the features of microfluidic technology is expected.

Optical Fingerprint Classification of Single Upconversion Nanoparticles by Deep Learning

Highly controlled synthesis of upconversion nanoparticles (UCNPs) can be achieved in the heterogeneous design, so that a library of optical properties can be arbitrarily produced by depositing multiple lanthanide ions. Such a control offers the potential in creating nanoscale barcodes carrying high-capacity information. With the increasing creation of optical information, it poses more challenges in decoding them in an accurate, high-throughput, and speedy fashion. Here, we reported that the deep-learning approach can recognize the complexity of the optical fingerprints from different UCNPs. Under a wide-field microscope, the lifetime profiles of hundreds of single nanoparticles can be collected at once, which offers a sufficient amount of data to develop deep-learning algorithms. We demonstrated that high accuracies of over 90% can be achieved in classifying 14 kinds of UCNPs. This work suggests new opportunities in handling the diverse properties of nanoscale optical barcodes toward the establishment of vast luminescent information carriers.

A Portable Microfluidic System for Point-of-Care Detection of Multiple Protein Biomarkers

Protein biomarkers are indicators of many diseases and are commonly used for disease diagnosis and prognosis prediction in the clinic. The urgent need for point-of-care (POC) detection of protein biomarkers has promoted the development of automated and fully sealed immunoassay platforms. In this study, a portable microfluidic system was established for the POC detection of multiple protein biomarkers by combining a protein microarray for a multiplex immunoassay and a microfluidic cassette for reagent storage and liquid manipulation. The entire procedure for the immunoassay was automatically conducted, which included the antibody–antigen reaction, washing and detection. Alpha-fetoprotein (AFP), carcinoembryonic antigen (CEA) and carcinoma antigen 125 (CA125) were simultaneously detected in this system within 40 min with limits of detection of 0.303 ng/mL, 1.870 ng/mL, and 18.617 U/mL, respectively. Five clinical samples were collected and tested, and the results show good correlations compared to those measured by the commercial instrument in the hospital. The immunoassay cassette system can function as a versatile platform for the rapid and sensitive multiplexed detection of biomarkers; therefore, it has great potential for POC diagnostics.

Trimer-based aptasensor for simultaneous determination of multiple mycotoxins using SERS and fluorimetry

An aptasensor is reported for the detection of three different kinds of mycotoxins, i.e., zearalenone (ZEN), ochratoxin A (OTA), and fumonisin B1 (FB1). Based on fluorescence resonance energy transfer effect (FRET) and surface-enhanced Raman scattering (SERS), the levels of ZEN, FB1, and OTA can be simultaneously determined. Under 980-nm and 650-nm laser excitation, the logarithmic values of fluorescence signal intensities at 543 nm and 670 nm are slowly increased as the concentrations of ZEN and OTA vary from 0.1 ng mL^-1 and 0.05 ng mL^-1 to 100 ng mL^-1 and 25 ng mL^-1, respectively. For FB1, under 980-nm laser excitation, the logarithmic value of SERS signal intensity at 1567 cm^-1 gradually increases with the concentration of FB1 in the range 0.05-200 pg mL^-1 (R² = 0.996). The detection limits of the proposed assay for ZEN, OTA, and FB1 are 0.03 ng mL^-1, 0.01 ng mL^-1, and 0.02 pg mL^-1, respectively. The selectivity experiment results indicate this assay possesses a high selectivity over other commonly encountered mycotoxins. The average recoveries range from 90 to 107%, revealing satisfactory application potential of the proposed assay. The developed aptasensor will bring bright prospects for research in the field of multiplexed mycotoxine detection. Graphical Abstract Schematic representation of an aptamer-based assay for multiple mycotoxins determination.

A Review of Methane Gas Detection Sensors: Recent Developments and Future Perspectives

Methane, the primary component of natural gas, is a significant contributor to global warming and climate change. It is a harmful greenhouse gas with an impact 28 times greater than carbon dioxide over a 100-year period. Preventing methane leakage from transmission pipelines and other oil and gas production activities is a possible solution to reduce methane emissions. In order to detect and resolve methane leaks, reliable and cost-effective sensors need to be researched and developed. This paper provides a comprehensive review of different types of methane detection sensors, including optical sensors, calorimetric sensors, pyroelectric sensors, semiconducting oxide sensors, and electrochemical sensors. The discussed material includes the definitions, mechanisms and recent developments of these sensors. A comparison between different methods, highlighting the advantages and disadvantages of each, is also presented to help address future research needs.

A fluorometric method for aptamer-based simultaneous determination of two kinds of the fusarium mycotoxins zearalenone and fumonisin B1 making use of gold nanorods and upconversion nanoparticles

An aptamer-based assay for the determination of two different kinds of fusarium mycotoxins, i.e., zearalenone (ZEN) and fumonisin B₁ (FB₁), is presented. Based on the inner filter effect (IFE) strategy, the contents of ZEN and FB₁ can be simultaneously quantified. It is making use of 65-nm gold nanorods (AuNRs), 20-nm upconversion nanoparticles (UCNPs), fluorescence dyes, and DNA sequences. In the absence of ZEN and FB₁, the UCNPs and AuNRs associate through DNA sequences. Due to IFE effect, weak fluorescence signals are collected. In the presence of ZEN or FB₁, UCNPs and AuNRs become unstable and partially separate from each other. This results in the recovery of fluorescence signals. Under 980-nm laser excitation, the logarithmic values of fluorescence signal intensities at 606 nm and 753 nm gradually increase with the concentration of ZEN and FB₁ in the ranges 0.05-100 μg L^-1 (the coefficient of determination is 0.997) and 0.01-100 ng L^-1 (the coefficient of determination is 0.986), respectively. The limits of detection (LOD) of the fabricated assay for ZEN and FB1 are 0.01 μg L^-1 and 0.003 ng L^-1, respectively. The proposed method has a high selectivity over other competitive mycotoxins, including aflatoxin B1, ochratoxin A, patulin and ochratoxin B. The applicability of the assay was evaluated in the determination of ZEN and FB1 contents in spiked corn samples. The average recoveries ranged from 89.9 to 106.6%. This result confirms the practicality of this method. Graphical abstract Schematic representation of an aptamer-based fluorometric method for simultaneous determination of two kinds of the fusarium mycotoxins zearalenone and fumonisin B₁.

Homotypic targeting upconversion nano-reactor for cascade cancer starvation and deep-tissue phototherapy

Cancer starvation therapy based on catalytic chemistry of glucose oxidase (GOx) offers great potential for multimodal treatment, benefiting from both nutrition shutting-off and the oxidization product hydrogen peroxide (H₂O₂). Herein, further optimization of such combined therapy was achieved by a cascade Nano-reactor, which was constructed by incorporating GOx into a bio-mimic upconversion nanosystem. The cascade began when GOx was delivered into tumor sites through homotypic targeting, facilitating selective starving of cancer cells and H₂O₂ generation. Then, upon 980 nm laser excitation, the 470 nm light emitted by upconversion nanoparticles (NaYF₄: Yb, Tm) photolyzed H₂O₂ into hydroxyl radical for phototherapy, superior to direct photolysis by blue light with limited tissue penetration depth. Meanwhile, the 800 nm emission of UCNPs was used to track the in vivo fate and tumor targeting ability of the Nano-reactor. Radionuclide imaging further confirmed the targeting of the Nano-reactor to subcutaneous 4T1 tumor and lung metastasis. Significantly enhanced therapeutic efficacy of this cascade starvation-phototherapy was validated in vitro and in vivo, suggesting the Nano-reactor as a smart, simple and strong system for cancer multimodal therapy.

Photon-Upconversion Barcoding with Multiple Barcode Channels: Application for Droplet Microfluidics

Barcoding facilitates high-throughput analytical methods in complex matrixes with a reduced volume of sample, reagents, time, and cost. Because of orthogonality to fluorescence, photon-upconversion barcodes attracted considerable attention in recent years. We constructed an epiluminescence detector, which, for the first time, demonstrated the reading of photon-upconversion spectra from microdroplets in a microfluidic chip with frequency up to 10 Hz. Non-negative least-squares deconvolution enabled the reading of an unprecedented number of photon-upconversion barcode channels (six) from emission spectra (excitation 980 nm, emission 430-875 nm). The standard deviation of barcode reading from microdroplets was ∼1%. Described barcoding can be, for example, used for multiparameter titrations, multiplexed biological and chemical assays, optimizations on a microfluidic platform, and preparation of barcoded concentration gradients and libraries.

A Novel Theranostic Nanoprobe for In Vivo Singlet Oxygen Detection and Real-Time Dose-Effect Relationship Monitoring in Photodynamic Therapy

Singlet oxygen, as the main member of reactive oxygen species, plays a significant role in cancer photodynamic therapy. However, the in vivo real-time detection of singlet oxygen remains challenging. In this work, a Förster resonance energy transfer (FRET)-based upconversion nanoplatform for monitoring the singlet oxygen in living systems is developed, with the ability to evaluate the in vivo dose-effect relationship between singlet oxygen and photodynamic therapy (PDT) efficacy. In details, this nanoplatform is composed of core-shell upconversion nanoparticles (UCNPs), photosensitizer MC540, NIR dye IR-820, and poly(acryl amine) PAA-octylamine, where the UCNPs serve as an energy donor while IR-820 serves as an energy acceptor. The nanoparticles are found to sensitively reflect the singlet oxygen levels generated in the tumor tissues during PDT, by luminescence intensity changes of UNCPs at 800 nm emission. Furthermore, it could also enable tumor treatment with satisfactory biocompatibility. To the best knowledge, this is the first report of a theranostic nanoplatform with the ability to formulate the in vivo dose-effect relationship between singlet oxygen and PDT efficacy and to achieve tumor treatment at the same time. This work might also provide an executable strategy to evaluate photodynamic therapeutic efficacy based on singlet oxygen pathway.

Rapid Isolation and Multiplexed Detection of Exosome Tumor Markers Via Queued Beads Combined with Quantum Dots in a Microarray

Tumor-derived exosomes are actively involved in cancer progression and metastasis and have emerged as a promising marker for cancer diagnosis in liquid biopsy. Because of their nanoscale size, complex biogenesis, and methodological limitations related to exosome isolation and detection, advancements in their analysis remain slow. Microfluidic technology offers a better analytic approach compared with conventional methods. Here, we developed a bead-based microarray for exosome isolation and multiplexed tumor marker detection. Using this method, exosomes are isolated by binding to antibodies on the bead surface, and tumor markers on the exosomes are detected through quantum dot (QD) probes. The beads are then uniformly trapped and queued among micropillars in the chip. This design benefits fluorescence observation by dispersing the signals into every single bead, thereby avoiding optical interference and enabling more accurate test results. We analyzed exosomes in the cell culture supernatant of lung cancer and endothelial cell lines, and different lung cancer markers labeled with three QD probes were used to conduct multiplexed detection of exosome surface protein markers. Lung cancer-derived samples showed much higher (~ sixfold-tenfold) fluorescence intensity than endothelial cell samples, and different types of lung cancer samples showed distinctive marker expression levels. Additionally, using the chip to detect clinical plasma samples from cancer patients showed good diagnostic power and revealed a well consistency with conventional tests for serological markers. These results provide insight into a promising method for exosome tumor marker detection and early-stage cancer diagnosis.

Recent Advances in Droplet-based Microfluidic Technologies for Biochemistry and Molecular Biology

Recently, droplet-based microfluidic systems have been widely used in various biochemical and molecular biological assays. Since this platform technique allows manipulation of large amounts of data and also provides absolute accuracy in comparison to conventional bioanalytical approaches, over the last decade a range of basic biochemical and molecular biological operations have been transferred to drop-based microfluidic formats. In this review, we introduce recent advances and examples of droplet-based microfluidic techniques that have been applied in biochemistry and molecular biology research including genomics, proteomics and cellomics. Their advantages and weaknesses in various applications are also comprehensively discussed here. The purpose of this review is to provide a new point of view and current status in droplet-based microfluidics to biochemists and molecular biologists. We hope that this review will accelerate communications between researchers who are working in droplet-based microfluidics, biochemistry and molecular biology.

Fluorescent microbeads for point-of-care testing: a review

Microbead-based point-of-care testing (POCT) has demonstrated great promise in translating detection modalities from bench-side to bed-side. This is due to the ease of visualization, high surface area-to-volume ratio of beads for efficient target binding, and efficient encoding capability for simultaneous detection of multiple analytes. This review (with 112 references) summarizes the progress made in the field of fluorescent microbead-based POCT. Following an introduction into the field, a first large section sums up techniques and materials for preparing microbeads, typically of dye-labelled particles, various kinds of quantum dots and upconversion materials. Further subsections cover the encapsulation of nanoparticles into microbeads, decoration of nanoparticles on microbeads, and in situ embedding of nanoparticles during microbead synthesis. A next large section summarizes microbead-based fluorometric POCT, with subsections on detection of nucleic acids, proteins, circulating tumor cells and bacteria. A further section covers emerging POCT based on the use of smartphones or flexible microchips. The last section gives conclusions and an outlook on current challenges and possible solutions. Aside from giving an overview on the state of the art, we expect this article to boost the further development of POCT technology. Graphical Abstract Schematic presentation of the fabrication of microbeads, the detection targets of interest including bacteria, circulating tumor cells (CTCs), protein and nucleic acid, and the emerging point-of-care testing (POCT) platform. The colored wheels of the bus represent the fluorescent materials embedded in (red color) or decorated on the surface of microbeads (green color).

FRET-Based Upconversion Nanoprobe Sensitized by Nd3+ for the Ratiometric Detection of Hydrogen Peroxide in Vivo

The exorbitant level of hydrogen peroxide is closely related to many human diseases. The development of novel probes for H₂O₂ detection will be beneficial to disease diagnosis. In this study, a novel Nd³⁺-sensitized upconversion nanoprobe based on Förster resonance energy transfer was first developed for sensing H₂O₂. This nanosystem was made of core-shell upconversion nanoparticles (emission at 540 and 660 nm), dicyanomethylene-4 H-pyran (DCM)-H₂O₂, and poly acrylic acid (PAA)-octylamine. Obviously, upconversion nanoparticles (UCNPs) doped with Nd³⁺ acted as an energy donor, and DCM-H₂O₂, transferring to DCM-OH with the reaction of H₂O₂, acted as an energy acceptor. The ratiometric upconversion luminescence (540 nm/660 nm) signal could be utilized to visualize the H₂O₂ level, and the LOD of the nanoprobe for H₂O₂ was quantified to be 0.168 μM. Meanwhile, owing to the dope of Nd³⁺, the nanoprobe would not induce the overheating effect in biological samples and could possess deeper tissue penetration depth, compared with the UCNPs excited by 980 nm light during bioimaging. The nanoprobe could also play an important role in detecting the exogenous and endogenous H₂O₂ in living cells with ratiometric UCL (upconversion luminescence) imaging. Furthermore, our nanoprobe could function in detecting the H₂O₂ in a tumor-bearing mouse model. Therefore, this novel nanoprobe along with the ratiometric method for responding and bioimaging H₂O₂ could serve as a new model that promotes the emergence of novel probes for H₂O₂ detection.