Multifunctional Microspheres Encoded with Upconverting Nanocrystals and Magnetic Nanoparticles for Rapid Separation and Immunoassays

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.

Fabrication of Fe3O4@poly(methyl methacrylate-co-glycidyl methacrylate) microspheres via miniemulsion polymerization using porous microspheres as templates for removal of cationic dyes

A novel and simple method was proposed to prepare monodisperse magnetic microspheres with controllable particle sizes and different functionalities.

Preparation of fluorescence-encoded microbeads with large encoding capacities and application of suspension array technology

This research study reported a type of reconstructed polystyrene microbeads for fluorescence encoding in suspension array technology (SAT). The present study improved their surface functionalization and compatibility with dyes.

Lab-on-Microsphere-FRET-Based Multiplex Sensor Platform

Here we report on the development and investigation of a novel multiplex assay model based on polymer microspheres (PMS) encoded with ternary AIS/ZnS quantum dots (QDs). The system was prepared via layer-by-layer deposition technique. Our studies of Förster resonance energy transfer (FRET) between the QD-encoded microspheres and two different cyanine dyes have demonstrated that the QD photoluminescence (PL) quenching steadily increases with a decrease in the QD-dye distance. We have found that the sensitized dye PL intensity demonstrates a clear maximum at two double layers of polyelectrolytes between QDs and Dye molecules on the polymer microspheres. Time resolved PL measurements have shown that the PL lifetime decreases for the QDs and increases for the dyes due to FRET. The designed system makes it possible to record spectrally different bands of FRET-induced dye luminescence with different decay times and thereby allows for the multiplexing by wavelength and photoluminescence lifetimes of the dyes. We believe that PMS encoded with AIS/ZnS QDs have great potential for the development of new highly selective and sensitive sensor systems for multiplex analysis to detect cell lysates and body fluids' representative biomarkers.

Multiplexed Nanobiosensors: Current Trends in Early Diagnostics

The ever-growing demand for fast, cheap, and reliable diagnostic tools for personalised medicine is encouraging scientists to improve existing technology platforms and to create new methods for the detection and quantification of biomarkers of clinical significance. Simultaneous detection of multiple analytes allows more accurate assessment of changes in biomarker expression and offers the possibility of disease diagnosis at the earliest stages. The concept of multiplexing, where multiple analytes can be detected in a single sample, can be tackled using several types of nanomaterial-based biosensors. Quantum dots are widely used photoluminescent nanoparticles and represent one of the most frequent choices for different multiplex systems. However, nanoparticles that incorporate gold, silver, and rare earth metals with their unique optical properties are an emerging perspective in the multiplexing field. In this review, we summarise progress in various nanoparticle applications for multiplexed biomarkers.

Multi-Dimensionally Extended Functionalization Innovates to an Entropy-Driven Detection of Multi-miRNAs for One-Step Cancer Screening and Diagnosis in Living Cells

Compared with tedious multi-step detections, multi-functional nanoprobes are effective for one-step screening and diagnosis of cancers by multi-detection of microRNAs (miRNAs). However, limited probe density, spatial mutual interference, and low target-triggered hybridization efficiency of nanoprobes will hinder intracellular applications. Here, for obtaining high loading density but low spatial mutual interference between functional biomolecules on nanoprobes, an extended biofunctionalization in three dimensions (the two-dimensional surface and a special "height" direction) is designed. Therefore, a multi-functional probe is constructed for one-step detection of multi-miRNAs for cancer screening and diagnosis. With linker-bridged multiple single-stranded DNAs swung out rigidly, multi-dimensionally extended upconversion nanorods (ME-UCNRs) covered by chitosan are constructed to load and deliver multiple biomolecules into living cells. Escaping from endolysosomes, ME-UCNRs maintain good biological activities of functionalized DNAs for effective detection of multi-miRNAs in living cells. Thereby, with multiple targets of miRNAs, toehold-mediated entropy-driven strand displacements are employed to give respectively changed fluorescent signals via fluorescence resonance energy transfer. Thus, a universal cancer biomarker of miR-21 and two specific liver-cancer biomarkers (miR-199a and miR-224) are efficiently detected through a one-step detection. By discriminating cancer cells from normal ones and determining liver-cancer cells simultaneously, this work innovates an efficient and definite one-step strategy for fast screening and early cancer diagnosis.

Facile synthesis of multifunctional nanoparticles encoded with quantum dots and magnetic nanoparticles: cell tagging and MRI

In this study, fluorescence-encoded magnetic biocompatible nanoparticles (NPs) were constructed from CdSe@ZnS quantum dots (QDs) and Fe₃O₄ nanoparticles with a one-step reprecipitation-encapsulation method. The resultant hybrid NPs exhibit small size (∼130 nm in diameter), highly bright QDs, two-color emissions (green and red) under single-wavelength excitation, easy separation with a magnet and efficient cellular internalization. Energy transfer between the incorporated QDs was studied to better tailor the encoded fluorescence, and 11 barcodes were obtained by adjusting the ratio of green and red QDs. We used four sets of the barcodes to tag specific cancer cells (HepG2) as a proof-of-concept, and distinguished each set according to respective overlayed fluorescence images using laser confocal microscopy. Moreover, the incorporated Fe₃O₄ NPs endowed as-constructed optical barcode superparamagnetic property by T ₂-enhanced magnetic resonance effect with an r ₂ value of 145.25 s^-1 mM^-1 at 3 T. These results suggest that the multifunctional NPs are very promising for discriminating different cells and dual-modality imaging.

Recent Advances in Magnetic Upconversion Nanocomposites for Bioapplications

The combination of magnetism and upconversion luminescent property into one single nanostructure is fascinating for biological fields, such as multimodal bioimaging, targeted drug delivery, and imaging-guided therapy. In this review, we will provide the state-of-the-art advances on magnetic upconversion nanocomposites towards their bioapplications. Their structure design, synthesis methods, surface engineering and applications in bioimaging, drug delivery, therapy as well as biodetection will be covered.

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).

A smartphone-based quantitative detection platform of mycotoxins based on multiple-color upconversion nanoparticles

The detection of mycotoxins in food is urgently needed because they pose a significant threat to public health. In this study, we developed a quantitative detection platform for mycotoxins by integrating multicolor upconversion nanoparticle barcode technology with fluorescence image processing using a smartphone-based portable device. The multi-colored upconversion nanoparticle encoded microspheres (UCNMs) were used as encoded signals for detecting different mycotoxins simultaneously. After indirect competitive immunoassays using UCNMs, images could be captured by the portable device and the camera of a smartphone. Then, a self-written Android application, which is an HSV-based image recognition program installed on a smartphone, analyzed images and offered a reliable and accurate result in less than 1 min. The quantitative detection platform of mycotoxins proved to be feasible and reliable, and the limit of detection (LOD) was 1 ng, which was lower than that obtained from standard assays. This study demonstrates a method for detecting mycotoxins in food and other point of care analysis.

Biochemistry and biomedicine of quantum dots: from biodetection to bioimaging, drug discovery, diagnostics, and therapy

According to recent research, nanotechnology based on quantum dots (QDs) has been widely applied in the field of bioimaging, drug delivery, and drug analysis. Therefore, it has become one of the major forces driving basic and applied research. The application of nanotechnology in bioimaging has been of concern. Through in vitro labeling, it was found that luminescent QDs possess many properties such as narrow emission, broad UV excitation, bright fluorescence, and high photostability. The QDs also show great potential in whole-body imaging. The QDs can be combined with biomolecules, and hence, they can be used for targeted drug delivery and diagnosis. The characteristics of QDs make them useful for application in pharmacy and pharmacology. This review focuses on various applications of QDs, especially in imaging, drug delivery, pharmaceutical analysis, photothermal therapy, biochips, and targeted surgery. Finally, conclusions are made by providing some critical challenges and a perspective of how this field can be expected to develop in the future.

STATEMENT OF SIGNIFICANCE

Quantum dots (QDs) is an emerging field of interdisciplinary subject that involves physics, chemistry, materialogy, biology, medicine, and so on. In addition, nanotechnology based on QDs has been applied in depth in biochemistry and biomedicine. Some forward-looking fields emphatically reflected in some extremely vital areas that possess inspiring potential applicable prospects, such as immunoassay, DNA analysis, biological monitoring, drug discovery, in vitro labelling, in vivo imaging, and tumor target are closely connected to human life and health and has been the top and forefront in science and technology to date. Furthermore, this review has not only involved the traditional biochemical detection but also particularly emphasized its potential applications in life science and biomedicine.

Supraparticles: Functionality from Uniform Structural Motifs

Under the right process conditions, nanoparticles can cluster together to form defined, dispersed structures, which can be termed supraparticles. Controlling the size, shape, and morphology of such entities is a central step in various fields of science and technology, ranging from colloid chemistry and soft matter physics to powder technology and pharmaceutical and food sciences. These diverse scientific communities have been investigating formation processes and structure/property relations of such supraparticles under completely different boundary conditions. On the fundamental side, the field is driven by the desire to gain maximum control of the assembly structures using very defined and tailored colloidal building blocks, whereas more applied disciplines focus on optimizing the functional properties from rather ill-defined starting materials. With this review article, we aim to provide a connecting perspective by outlining fundamental principles that govern the formation and functionality of supraparticles. We discuss the formation of supraparticles as a result of colloidal properties interplaying with external process parameters. We then outline how the structure of the supraparticles gives rise to diverse functional properties. They can be a result of the structure itself (emergent properties), of the colocalization of different, functional building blocks, or of coupling between individual particles in close proximity. Taken together, we aim to establish structure-property and process-structure relationships that provide unifying guidelines for the rational design of functional supraparticles with optimized properties. Finally, we aspire to connect the different disciplines by providing a categorized overview of the existing, diverging nomenclature of seemingly similar supraparticle structures.

Gold Nanoparticle-Based Paper Sensor for Simultaneous Detection of 11 Benzimidazoles by One Monoclonal Antibody

A colloidal gold immunochromatographic assay based on a generic monoclonal antibody is developed for the simultaneous detection of benzimidazoles and metabolite residues in milk samples. The monoclonal antibody is prepared using 2-(methoxycarbonylamino)-3H-benzimidazole-5-carboxylic acid as the hapten, and it can recognize 11 types of benzimidazoles simultaneously. The immunochromatographic strip is assembled and labeled using gold nanoparticles. This strip can detect 11 benzimidazoles including albendazole, albendazole s-oxide, albendazole sulfone, fenbendazole, fenbendazole sulfone, flubendazole, mebendazole, parbendazole, oxfendazole, oxibendazole, and carbendazim within 15 min in milk samples. Results are obtained visually with the naked eye, and the cutoff values and the visual limit of detection values for these benzimidazoles are 25, 6.25, 12.5, 12.5, 50, 25, 50, 50, 50, 6.25, and 25 ng mL^-1 , and 6.25, 3.125, 3.125, 1.56, 12.5, 6.25, 12.5, 12.5, 6.25, 0.78, and 12.5 ng mL^-1 , respectively. Results are also obtained using a hand-held strip scan reader, with calculated limit of detection values for these benzimidazoles of 0.83, 0.77, 1.83, 0.98, 7.67, 3.50, 3.96, 5.71, 0.92, 0.59, and 1.69 ng mL^-1 , respectively. In short, the developed paper sensor is a useful tool for rapid and simple screening of residues of benzimidazoles in milk samples.

Novel Magnetic-Luminescent Janus Nanoparticles for Cell Labeling and Tumor Photothermal Therapy

Magnetic-luminescent nanocomposites have multiple uses including multimodal imaging, magnetic targeted drug delivery, and cancer imaging-guided therapies. In this work, dumbbell-like MnFe₂ O₄ -NaYF₄ Janus nanoparticles are synthesized via a two-step thermolysis approach. These synthesized nanoparticles exhibit stability in aqueous solutions and very low cytotoxicity after poly(acryl amide) modification. High cellular uptake efficiency is observed for the folic acid-conjugated MnFe₂ O₄ -NaYF₄ in human esophagus carcinoma cells (Eca-109) due to the upconversion luminescence properties as well as the folate targeting potential. The MnFe₂ O₄ -NaYF₄ also strongly absorbs light in the near-infrared range and rapidly converts to heat energy. It is demonstrated that Eca-109 cells incubated with MnFe₂ O₄ -NaYF₄ are killed with high efficiency after 808 nm laser irradiation. Furthermore, the growth of tumors in mice (grown from Eca-109 cells) is highly inhibited by the photothermal effects of MnFe₂ O₄ -NaYF₄ efficiently. Histological analysis reveals no pathological change and inflammatory response in heart, liver, spleen, lung, or kidney. The low toxicity, excellent luminescence, and highly efficient photothermal therapy properties of MnFe₂ O₄ -NaYF₄ Janus nanoparticles illustrated in this work support their vast potential for nanomedicine and cancer therapy.

Efficient Enrichment and Analyses of Bacteria at Ultralow Concentration with Quick-Response Magnetic Nanospheres

Enrichment and purification of bacteria from complex matrices are crucial for their detection and investigation, in which magnetic separation techniques have recently show great application advantages. However, currently used magnetic particles all have their own limitations: Magnetic microparticles exhibit poor binding capacity with targets, while magnetic nanoparticles suffer slow magnetic response and high loss rate during treatment process. Herein, we used a highly controllable layer-by-layer assembly method to fabricate quick-response magnetic nanospheres (MNs), and with Salmonella typhimurium as a model, we successfully achieve their rapid and efficient enrichment. The MNs combined the advantages of magnetic microparticles and nanoparticles. On the one hand, the MNs had a fast magnetic response, and almost 100% of the MNs could be recovered by 1 min attraction with a simple magnetic scaffold. Hence, using antibody conjugated MNs (immunomagnetic nanospheres, IMNs) to capture bacteria hardly generated loss and did not need complex separation tools or techniques. On the other hand, the IMNs showed much excellent capture capacity. With 20 min interaction, almost all of the target bacteria could be captured, and even only one bacterium existing in the samples was not missed, comparing with the immunomagnetic microparticles which could only capture less than 50% of the bacteria. Besides, the IMNs could achieve the same efficient enrichment in complex matrices, such as milk, fetal bovine serum, and urine, demonstrating their good stability, strong anti-interference ability, and low nonspecific adsorption. In addition, the isolated bacteria could be directly used for culture, polymerase chain reaction (PCR) analyses, and fluorescence immunoassay without a release process, which suggested our IMNs-based enrichment strategy could be conveniently coupled with the downstream identification and analysis techniques. Thus, the MNs provided by this work showed great superiority in bacteria enrichment, which would be a promising tool for bacteria detection and investigation.

A Protein-Polymer Bioconjugate-Coated Upconversion Nanosystem for Simultaneous Tumor Cell Imaging, Photodynamic Therapy, and Chemotherapy

Combined cancer therapy possesses many advantages including improved tumoricidal efficacy, reduced side effects, and retarded drug resistance. Herein, a protein-polymer bioconjugate-coated multifunctional upconversion nanosystem, consisting of upconversion nanoparticles (UCNs) core, tailored amphiphilic protein-polymer bioconjugate shell, and photosensitizer zinc phthalocyanine (ZnPc) and antitumor drug doxorubicin coloaded inside, was elaborately developed for combined photodynamic therapy (PDT) and chemotherapy. In this system, UCNs core could convert deep penetrating near-infrared light to visible light for simultaneous cell fluorescence imaging and photodynamic therapy by activating ZnPc to generate cytotoxic ROS, while the protective shell of bovine serum albumin-poly(ε-caprolactone) (BSA-PCL) offered excellent water solubility, good stability, and low cytotoxicity. The ROS production test showed that this nanosystem could successfully generate singlet oxygen under NIR irradiation. A cellular uptake study demonstrated that intense fluorescence emission of the UCNs could be observed in HeLa cells, indicating their outstanding real-time imaging capability. More importantly, compared with single PDT or chemotherapy systems, the constructed combined therapy UCNs system demonstrated significantly enhanced tumor cell killing efficiency. On the basis of our findings, this multifunctional UCNs nanosystem could be a promising versatile theranostic nanoplatform for image-guided combined cancer therapy.