One-pot hydrothermal synthesis of fluorophore-modified cerium oxide nanoparticles.

Cerium oxide nanoparticles (CeO2 NPs), which have powerful antioxidant properties, are promising nanomaterials for the treatment of diseases associated with oxidative stress. The well-developed surface of CeO2 NPs makes them promising for use as a multifunctional system for various biomedical applications. This work demonstrates a simple approach that allows the direct formation of a molecular fluorophore on the surface of CeO2 NPs using a simple one-pot hydrothermal synthesis. Thus, we were able to synthesize CeO2 NPs of ultra-small size ∼2 nm with a narrow distribution, highly stable fluorescence, and a quantum yield of ∼62%. UV-visible transmission studies revealed that the resulting CeO2 NPs exhibited fast autogenerative catalytic reduction. In vitro results showed high biocompatibility of CeO2 NPs; their internalization occurs mainly in the region of cell nuclei. Thus, the resulting NPs have the necessary parameters and can be successfully used in biovisualization and therapy.

Fluorescent Alloyed CdZnSeS/ZnS Nanosensor for Doxorubicin Detection.

Doxorubicin (DOX) is widely used in chemotherapy as an anti-tumor drug. However, DOX is highly cardio-, neuro- and cytotoxic. For this reason, the continuous monitoring of DOX concentrations in biofluids and tissues is important. Most methods for the determination of DOX concentrations are complex and costly, and are designed to determine pure DOX. The purpose of this work is to demonstrate the capabilities of analytical nanosensors based on the quenching of the fluorescence of alloyed CdZnSeS/ZnS quantum dots (QDs) for operative DOX detection. To maximize the nanosensor quenching efficiency, the spectral features of QDs and DOX were carefully studied, and the complex nature of QD fluorescence quenching in the presence of DOX was shown. Using optimized conditions, turn-off fluorescence nanosensors for direct DOX determination in undiluted human plasma were developed. A DOX concentration of 0.5 µM in plasma was reflected in a decrease in the fluorescence intensity of QDs, stabilized with thioglycolic and 3-mercaptopropionic acids, for 5.8 and 4.4 %, respectively. The calculated Limit of Detection values were 0.08 and 0.03 µg/mL using QDs, stabilized with thioglycolic and 3-mercaptopropionic acids, respectively.

Targeted Therapy for Glomerulonephritis Using Arterial Delivery of Encapsulated Etanercept.

Complex immunosuppressive therapy is prescribed in medical practice to patients with glomerulonephritis to help them overcome symptoms and prevent chronic renal failure. Such an approach requires long-term systemic administration of strong medications, which causes severe side effects. This work shows the efficiency of polymer capsule accumulation (2.8 ± 0.4 µm) containing labeled etanercept (100 µg per dose) in the kidneys of mice. The comparison of injection into the renal artery and tail vein shows the significant superiority of the intra-arterial administration strategy. The etanercept retention rate of 18% and 8% ID in kidneys was found 1 min and 1 h after injection, respectively. The capsules were predominantly localized in the glomeruli after injection in mice using a model of acute glomerulonephritis. Histological analysis confirmed a significant therapeutic effect only in animals with intra-arterial administration of microcapsules with etanercept. The proposed strategy combines endovascular surgery and the use of polymer microcapsules containing a high molecular weight drug that can be successfully applied to treat a wide range of kidney diseases associated with glomerular pathology.

Luminescent Composite Carbon/SiO2 Structures: Synthesis and Applications.

Luminescent carbon nanostructures (CNSs) have attracted great interest from the scientific community due to their photoluminescent properties, structural features, low toxicity, and a great variety of possible applications. Unfortunately, a few problems hinder their further development. These include the difficulties of separating a mixture of nanostructures after synthesis and the dependence of their properties on the environment and the aggregate state. The application of a silica matrix to obtain luminescent composite particles minimizes these problems and improves optical properties, reduces photoluminescence quenching, and leads to wider applications. We describe two methods for the formation of silica composites containing CNSs: inclusion of CNSs into silica particles and their grafting onto the silica surface. Moreover, we present approaches to the synthesis of multifunctional particles. They combine the unique properties of silica and fluorescent CNSs, as well as magnetic, photosensitizing, and luminescent properties via the combination of functional nanoparticles such as iron oxide nanoparticles, titanium dioxide nanoparticles, quantum dots (QDs), and gold nanoclusters (AuNCs). Lastly, we discuss the advantages and challenges of these structures and their applications. The novelty of this review involves the detailed description of the approaches for the silica application as a matrix for the CNSs. This will support researchers in solving fundamental and applied problems of this type of carbon-based nanoobjects.

Luminescent alloyed quantum dots for turn-off enzyme-based assay.

A new bioanalytical labeling system based on alloyed quantum dots' (QDs) photoluminescence quenching caused by an enzymatic reaction has been developed and tested for the first time. The catalytic role of the enzyme provides high sensitivity and the possibility of varying detecting time to improve assay sensitivity. Alloyed luminescent QDs were chosen in view of their small size (5-7 nm) and the high sensitivity of their optical properties to physicochemical interactions. Here, we described the synthesis of alloyed luminescent QDs and demonstrated the possibility of using them as a luminescent turn-off substrate for enzymatic assay. Synthesized alloyed QDs were found to be a sensitive turn-off substrate for glucose oxidase in homogeneous and heterogeneous assay models. CdZnSeS and CdZnSeS/ZnS QDs covered with dihydrolipoic acid and 2-mercaptoethanol were tested. A glucose oxidase limit of detection of 6.6 nM for the heterogenous high-throughput model assay was reached.

Influence of particle architecture on the photoluminescence properties of silica-coated CdSe core/shell quantum dots.

Light-emitting nanoparticles like semiconductor nanocrystals (termed quantum dots, QDs) are promising candidates for biosensing and bioimaging applications based on their bright and stable photoluminescent properties. As high-quality QDs are often synthesized in organic solvents, strategies needed to be developed to render them water-dispersible without affecting their optical properties and prevent changes in postmodification steps like the biofunctionalization with antibodies or DNA. Despite a large number of studies on suitable surface modification procedures, the preparation of water-soluble QDs for nanobiotechnology applications still presents a challenge. To highlight the advantages of surface silanization, we systematically explored the influence of the core/multishell architecture of CdSe/CdS/ZnS QDs and the silanization conditions on the optical properties of the resulting silanized QDs. Our results show that the optical properties of silica-coated CdSe/CdS/ZnS QDs are best preserved in the presence of a thick CdS (6 monolayers (ML)) intermediate shell, providing a high photoluminescence quantum yield (PL QY), and a relatively thick ZnS (4.5 ML) external shell, effectively shielding the QDs from the chemical changes during silica coating. In addition to the QD core/shell architecture, other critical parameters of the silica-coating process, that can have an influence on the optical properties of the QD, include the choice of the surfactant and its concentration used for silica coating. The highest PL QY of about 46% was obtained by a microemulsion silica-coating procedure with the surfactant Brij L4, making these water-dispersible QDs to well-suited optical reporters in future applications like fluorescence immunoassays, biomedicine, and bioimaging.

Homogenous FRET-based fluorescent immunoassay for deoxynivalenol detection by controlling the distance of donor-acceptor couple.

Semiconductor quantum dots (QDs) are one of the most popular luminescent labels that are widely used in food and medical analysis. Their unique optical properties establish QDs as excellent tools for highly sensitive biosensors based on Förster resonance energy transfer (FRET). To provide a convenient analytical system with long-term optical stability, a FRET pair consisting of QDs as energy donor and gold nanoparticles (GNs) as energy acceptor was developed. Careful selection of donor and acceptor properties allowed to achieve a large Förster distance of 12.9 nm and to use full-size specific antibody. As the immunoreagents pair, mycotoxins were bound to proteins and then to GNs, while QDs were conjugated with specific antibodies. FRET was observed as a result of the immunocomplex formation. Contributions of FRET and inner filter effect on the quenching were evaluated separately. The quenching effect in the donor-acceptor pair was compared for proteins with different sizes. The developed homogeneous FRET-based immunoassay for the detection of deoxynivalenol (DON) is an example of a fast method for high-throughput control of mycotoxins. The quenching effect of FRET was observed with a limit of detection of 28 µg kg-1 of DON in spiked wheat samples.

Silanized Luminescent Quantum Dots for the Simultaneous Multicolor Lateral Flow Immunoassay of Two Mycotoxins.

A critical point for the successful development of a fluorescent quantum dot (QD)-based immunoassay is maintaining the high fluorescence quantum yield of QDs during hydrophilization and bioconjugation. In this paper, we carefully designed CdSe/CdS and CdSe/CdS/ZnS core-shell heterostructures and extended them with silica coating of different surface composition allowing preservation of fluorescence quantum yield as high as 70% in aqueous media. The silanized QDs containing epoxy and carboxy surface groups were bioconjugated with monoclonal antibodies. The synthesized fluorescent conjugates were used in a multicolor lateral flow immunoassay for simultaneous determination of two mycotoxins. Zearalenone and deoxynivalenol were chosen as a proof of concept. Cutoff levels for the zearalenone and deoxynivalenol detection were adjusted to be at 40 and 400 µg kg-1, respectively, complying with the European Commission regulation. Validation of the developed test was performed by analysis of 34 naturally contaminated maize and wheat samples; as a confirmatory method, LC-MS/MS was used.