Fluorescent nanocrystal quantum dots as medical diagnostic tools

Nontoxic Fluorescent Nanoprobes for Multiplexed Detection and 3D Imaging of Tumor Markers in Breast Cancer

Multiplexed fluorescent immunohistochemical analysis of breast cancer (BC) markers and high-resolution 3D immunofluorescence imaging of the tumor and its microenvironment not only facilitate making the disease prognosis and selecting effective anticancer therapy (including photodynamic therapy), but also provides information on signaling and metabolic mechanisms of carcinogenesis and helps in the search for new therapeutic targets and drugs. The characteristics of imaging nanoprobe efficiency, such as sensitivity, target affinity, depth of tissue penetration, and photostability, are determined by the properties of their components, fluorophores and capture molecules, and by the method of their conjugation. Regarding individual nanoprobe components, fluorescent nanocrystals (NCs) are widely used for optical imaging in vitro and in vivo, and single-domain antibodies (sdAbs) are well established as highly specific capture molecules in diagnostic and therapeutic applications. Moreover, the technologies of obtaining functionally active sdAb–NC conjugates with the highest possible avidity, with all sdAb molecules bound to the NC in a strictly oriented manner, provide 3D-imaging nanoprobes with strong comparative advantages. This review is aimed at highlighting the importance of an integrated approach to BC diagnosis, including the detection of biomarkers of the tumor and its microenvironment, as well as the need for their quantitative profiling and imaging of their mutual location, using advanced approaches to 3D detection in thick tissue sections. The existing approaches to 3D imaging of tumors and their microenvironment using fluorescent NCs are described, and the main comparative advantages and disadvantages of nontoxic fluorescent sdAb–NC conjugates as nanoprobes for multiplexed detection and 3D imaging of BC markers are discussed.

Next-Generation Theranostic Agents Based on Polyelectrolyte Microcapsules Encoded with Semiconductor Nanocrystals: Development and Functional Characterization

Fabrication of polyelectrolyte microcapsules and their use as carriers of drugs, fluorescent labels, and metal nanoparticles is a promising approach to designing theranostic agents. Semiconductor quantum dots (QDs) are characterized by extremely high brightness and photostability that make them attractive fluorescent labels for visualization of intracellular penetration and delivery of such microcapsules. Here, we describe an approach to design, fabricate, and characterize physico-chemical and functional properties of polyelectrolyte microcapsules encoded with water-solubilized and stabilized with three-functional polyethylene glycol derivatives core/shell QDs. Developed microcapsules were characterized by dynamic light scattering, electrophoretic mobility, scanning electronic microscopy, and fluorescence and confocal microscopy approaches, providing exact data on their size distribution, surface charge, morphological, and optical characteristics. The fluorescence lifetimes of the QD-encoded microcapsules were also measured, and their dependence on time after preparation of the microcapsules was evaluated. The optimal content of QDs used for encoding procedure providing the optimal fluorescence properties of the encoded microcapsules was determined. Finally, the intracellular microcapsule uptake by murine macrophages was demonstrated, thus confirming the possibility of efficient use of developed system for live cell imaging and visualization of microcapsule transportation and delivery within the living cells.

Chiral recognition of phenylglycinol enantiomers based on N-acetyl-l-cysteine capped CdTe quantum dots in the presence of Ag. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2017;183:23-29. [PMID: 28432917 DOI: 10.1016/j.saa.2017.04.014]

In this study, a novel method for chiral recognition of phenylglycinol (PG) enantiomers was proposed. Firstly, water-soluble N-acetyl-l-cysteine (NALC)-capped CdTe quantum dots (QDs) were synthesized and experiment showed that the fluorescence intensity of the reaction system slightly enhancement when added PG enantiomers to NALC-capped CdTe quantum dots (QDs), but the R-PG and S-PG could not be distinguished. Secondly, when there was Ag⁺ presence in the reaction system, the experiment result was extremely interesting, the PG enantiomers cloud make NALC-capped CdTe QDs produce different fluorescence signal, in which the fluorescence of S-PG+Ag⁺+NALC-CdTe system was significantly enhanced, and the fluorescence of R-PG+Ag⁺+NALC-CdTe system was markedly decreased. Thirdly, all the enhanced and decreased of the fluorescence intensity were directly proportional to the concentration of R-PG and S-PG in the linearly range 10^-5-10^-7mol·L^-1, respectively. So, the new method for simultaneous determination of the PG enantiomers was built too. The experiment result of the method was satisfactory with the detection limit of PG can reached 10^-7mol·L^-1 and the related coefficient of S-PG and R-PG are 0.995 and 0.980, respectively. The method was highly sensitive, selective and had wider detection range compared with other methods.

Blood group antigen studies using CdTe quantum dots and flow cytometry

New methods of analysis involving semiconductor nanocrystals (quantum dots [QDs]) as fluorescent probes have been highlighted in life science. QDs present some advantages when compared to organic dyes, such as size-tunable emission spectra, broad absorption bands, and principally exceptional resistance to photobleaching. Methods applying QDs can be simple, not laborious, and can present high sensibility, allowing biomolecule identification and quantification with high specificity. In this context, the aim of this work was to apply dual-color CdTe QDs to quantify red blood cell (RBC) antigen expression on cell surface by flow cytometric analysis. QDs were conjugated to anti-A or anti-B monoclonal antibodies, as well as to the anti-H (Ulex europaeus I) lectin, to investigate RBCs of A₁, B, A₁B, O, A₂, and A_weak donors. Bioconjugates were capable of distinguishing the different expressions of RBC antigens, both by labeling efficiency and by flow cytometry histogram profile. Furthermore, results showed that RBCs from A_weak donors present fewer amounts of A antigens and higher amounts of H, when compared to A₁ RBCs. In the A group, the amount of A antigens decreased as A₁ > A₃ > A_X = A_el, while H antigens were A_X = A_el > A₁. Bioconjugates presented stability and remained active for at least 6 months. In conclusion, this methodology with high sensibility and specificity can be applied to study a variety of RBC antigens, and, as a quantitative tool, can help in achieving a better comprehension of the antigen expression patterns on RBC membranes.

Surface modified multifunctional nanomedicines for simultaneous imaging and therapy of cancer

INTRODUCTION

To date, a growing number of advanced anticancer nanomedicines (e.g., Doxil(®), Lipoxal(®), DepoCyte(®)) have entered into different phases of clinical trials. However, most of these medicaments fail to differentiate between diseased and normal cells. They also do not have capability of real time monitoring of disease status trough on-demand imaging/sensing of target molecule(s). Multifunctional nanomedicines and theranostics can resolve such limitations, while formulation of these advanced seamless systems appear to involve various sophisticated process, exploiting several bioconjugations.

METHODS

Recent works upon multifunctional nanomedicines for simultaneous imaging and therapy of cancer have been systematically reviewed, focusing on surface modification and application of advanced nanobiomaterials.

RESULTS

Ultimate therapy of malignancies, as complex systems, demands implementation of seamless nanosystems (NSs) that can specifically target the cancerous cells and smartly deliver the anticancer agent(s) into the desired target site. Engineering of such NSs requires in-situ coordination of various technologies (e.g., synthesis, surface modification and bioconjugation) in order to achieve improved pharmacokinetics and pharmacodynamics outcomes.

CONCLUSION

Seamless multimodal NSs have potential to simultaneously target and monitor the tumor cells through homing and imaging/sensing devices and deliver the therapeutic agents. However, to achieve superior pharmacokinetics with maximal efficacy and minimal side effects, these advanced NSs need to become much more intelligent to sense the disease condition and liberate therapeutics on demand.

Emerging applications of fluorescent nanocrystals quantum dots for micrometastases detection

The occurrence of metastases is one of the main causes of death in many cancers and the main cause of death for breast cancer patients. Micrometastases of disseminated tumour cells and circulating tumour cells are present in more than 30% of breast cancer patients without any clinical or even histopathological signs of metastasis. Low abundance of these cell types in clinical diagnostic material dictates the necessity of their enrichment prior to reliable detection. Current micrometastases detection techniques are based on immunocytochemical and molecular methods suffering from low efficiency of tumour cells enrichment and observer-dependent interpretation. The use of highly fluorescent semiconductor nanocrystals, also known as "quantum dots" and nanocrystal-encoded microbeads tagged with a wide panel of antibodies against specific tumour markers offers unique possibilities for ultra-sensitive micrometastases detection in patients' serum and tissues. The nanoparticle-based diagnostics provides an opportunity for highly sensitive parallel quantification of specific proteins in a rapid and low-cost method, thereby providing a link between the primary tumour and the micrometastases for early diagnosis.

Probing cell-type-specific intracellular nanoscale barriers using size-tuned quantum dots

The compartmentalization of size-tuned luminescent semiconductor nanocrystal quantum dots (QDs) in four distinctive cell lines, which would be representative of the most likely environmental exposure routes to nanoparticles in humans, is studied. The cells are fixed and permeabilized prior to the addition of the QDs, thus eliminating any cell-membrane-associated effects due to active QD uptake mechanisms or to specificity of signaling routes in different cell types, but leaving intact the putative physical subcellular barriers. All quantitative assays are performed using a high content analysis (HCA) platform, thereby obtaining robust data on large cell populations. While smaller QDs 2.1 nm in diameter enter the nuclei and localize to the nucleoli in all cell types, the rate and dynamics of their passage vary depending on the cell origin. As the QD size is increased to 4.4 nm, penetration into the cell is reduced but each cell line displays its own cutoff size thresholds reflecting cell-type-determined cytoplasmic and nuclear pore penetration specificity. These results give rise to important considerations regarding the differential compartmentalization and susceptibility of organs, tissues, and cells to nanoparticles, and may be of prime importance for biomedical imaging and drug-delivery research employing nanoparticle-based probes and systems.

Fluorescent nanocrystal-encoded microbeads for multiplexed cancer imaging and diagnosis

Bead-based assays on very large numbers of molecules in proteomics, genomics, drug screening and clinical diagnostics require encoding of each of the microbeads according to the particular ligand bound to its surface. The benefits of using optically encoded microbeads (instead of the solid-state two-dimensional arrays) are derived from the freedom of bead to move in three dimensions. Polymeric beads optically encoded with organic dyes allow for a limited number of unique codes whereas the use of semiconductor nanocrystals as fluorescent tags improves the beads multiplexed imaging capabilities, photostability and sensitivity of the antigen detection. Additionally, an employment of the recently demonstrated Förster resonance energy transfer (FRET) from the microbeads nanocrystal codes to the nearby antibody dye label allows for the very specific detection of the interaction between the microbead and the antibody. This interaction turns the fluorescence signal from dye label off and on thus effectively discriminating between the occurrence and the non-occurrence of antibody binding. The absence of fluorescent background from non-interacting with the beads dye-labelled antibodies additionally increases the sensitivity of detection and further facilitates the multiplexing capabilities of nanocrystals-based detection and diagnostics. This paper reviews the state-of-the-art results of development of microbeads optically encoded with the fluorescent nanocrystals "quantum dots" and their applications to proteomics for cancer antigens and autoantibodies imaging and diagnosis.