Quantum dot-based lab-on-a-bead system for multiplexed detection of free and total prostate-specific antigens in clinical human serum samples

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.

Structure-function relationships in polymeric multilayer capsules designed for cancer drug delivery

The targeted delivery of cancer drugs to tumor-specific molecular targets represents a major challenge in modern personalized cancer medicine. Engineering of micron and submicron polymeric multilayer capsules allows the obtaining of multifunctional theranostic systems serving as controllable stimulus-responsive tools with a high clinical potential to be used in cancer therapy and detection. The functionalities of such theranostic systems are determined by the design and structural properties of the capsules. This review (1) describes the current issues in designing cancer cell-targeting polymeric multilayer capsules, (2) analyzes the effects of the interactions of the capsules with the cellular and molecular constituents of biological fluids, and (3) presents the key structural parameters determining the effectiveness of capsule targeting. The influence of the morphological and physicochemical parameters and the origin of the structural components and surface ligands on the functional activity of polymeric multilayer capsules at the molecular, cellular, and whole-body levels are summarized. The basic structural and functional principles determining the future trends of theranostic capsule development are established and discussed.

One-step assembly of barcoded planar microparticles for efficient readout of multiplexed immunoassay

Barcoded planar microparticles are suitable for developing cost-efficient multiplexed assays, but the robustness and efficiency of the readout process still needs improvement. Here, we designed a one-step microparticle assembling chip that produces efficient and accurate multiplex immunoassay readout results. Our design was also compatible with injection molding for mass production.

Recent advances in nanomaterials for prostate cancer detection and diagnosis

Despite the significant progress in the discovery of biomarkers and the exploitation of technologies for prostate cancer (PCa) detection and diagnosis, the initial screening of these PCa-related biomarkers using current...

Ultrasound-Triggered Liposomes Encapsulating Quantum Dots as Safe Fluorescent Markers for Colorectal Cancer

Quantum dots (QDs) are a promising tool to detect and monitor tumors. However, their small size allows them to accumulate in large quantities inside the healthy cells (in addition to the tumor cells), which increases their toxicity. In this study, we synthesized stealth liposomes encapsulating hydrophilic graphene quantum dots and triggered their release with ultrasound with the goal of developing a safer and well-controlled modality to deliver fluorescent markers to tumors. Our results confirmed the successful encapsulation of the QDs inside the core of the liposomes and showed no effect on the size or stability of the prepared liposomes. Our results also showed that low-frequency ultrasound is an effective method to release QDs encapsulated inside the liposomes in a spatially and temporally controlled manner to ensure the effective delivery of QDs to tumors while reducing their systemic toxicity.

Nanoparticle-Doped Hybrid Polyelectrolyte Microcapsules with Controlled Photoluminescence for Potential Bioimaging Applications

Fluorescent imaging is widely used in the diagnosis and tracking of the distribution, interaction, and transformation processes at molecular, cellular, and tissue levels. To be detectable, delivery systems should exhibit a strong and bright fluorescence. Quantum dots (QDs) are highly photostable fluorescent semiconductor nanocrystals with wide absorption spectra and narrow, size-tunable emission spectra, which make them suitable fluorescent nanolabels to be embedded into microparticles used as bioimaging and theranostic agents. The layer-by-layer deposition approach allows the entrapping of QDs, resulting in bright fluorescent microcapsules with tunable surface charge, size, rigidity, and functional properties. Here, we report on the engineering and validation of the structural and photoluminescent characteristics of nanoparticle-doped hybrid microcapsules assembled by the deposition of alternating oppositely charged polyelectrolytes, water-soluble PEGylated core/shell QDs with a cadmium selenide core and a zinc sulfide shell (CdSe/ZnS), and carboxylated magnetic nanoparticles (MNPs) onto calcium carbonate microtemplates. The results demonstrate the efficiency of the layer-by-layer approach to designing QD-, MNP-doped microcapsules with controlled photoluminescence properties, and pave the way for the further development of next-generation bioimaging agents based on hybrid materials for continuous fluorescence imaging.

CdSe/ZnS quantum dots exhibited nephrotoxicity through mediating oxidative damage and inflammatory response

Objective: This study aimed to the evaluate the nephrotoxicity of CdSe/ZnS QDs in vitro and vivo, as well as investigate the underlying toxicity mechanisms.

Results: In vitro experiments showed that compared with control cells, CdSe/ZnS QDs treatment significantly inhibited cell viability and promoted cell apoptosis in dose-dependent manner in NRK cells. Notably, CdSe/ZnS QDs treatment increased the contents of MDA and ROS, and decreased the activities of SOD, CAT and GSH-Px; however, the co-treatment of NAC and QDs relieved the oxidative damage of NRK cells. Moreover, in vivo experiments also revealed that CdSe/ZnS QDs treatment obviously increased kidney weight coefficient, damaged the kidney function, as well as induced inflammatory response and inhibited the activation of NRF2/Keap1 pathway in kidney tissues of mice.

Conclusions: CdSe/ZnS QDs exhibited obvious nephrotoxicity by mediating oxidative damage and inflammatory response in vitro and in vivo via NRF2/Keap1 pathway.

Methods: The characterization of CdSe/ZnS QDs was analyzed by transmission electron microscope, emission spectrum scanning, and dynamic light scattering. Rat kidney cells (NRK) were exposed to different doses of CdSe/ZnS QDs with or without N-acetylcysteine (NAC, antioxidant). Then, cellular uptake of CdSe/ZnS QDs was detected, and in vitro cytotoxicity was evaluated by MTT assay and TUNEL assay.

Recent advances in nanoscale materials for antibody-based cancer theranostics

The quest for advanced management tools or options of various cancers has been on the rise to efficiently reduce their risks of mortality without the demerits of conventional treatments (e.g., undesirable side effects of the medications on non-target tissues, non-targeted distribution, slow clearance of the administered drugs, and the development of drug resistance over the duration of therapy). In this context, nanomaterials-antibody conjugates can offer numerous advantages in the development of cancer theranostics over conventional delivery systems (e.g., highly specific and enhanced biodistribution of the drug in targeted tissues, prolonged systemic circulation, low toxicity, and minimally invasive molecular imaging). This review comprehensively discusses and evaluates recent advances in the application of nanomaterial-antibody bioconjugates for cancer theranostics for the further advancement in the control of diverse cancerous diseases. Further, discussion is expanded to cover the various challenges and limitations associated with the design and development of nanomaterial-antibody conjugates applicable towards better management of cancer.

Nanoparticle enhanced optical biosensing technologies for Prostate Specific Antigen biomarker detection

Prostate Cancer (PCa) is one of the deadliest forms of Cancer among men. Early screening process for PCa is primarily conducted with the help of a FDA approved biomarker known as Prostate Specific Antigen (PSA). The PSA-based screening is challenged with the inability to differentiate between the cancerous PSA and Benign Prostatic Hyperplasia (BPH), resulting in high rates of false-positives. Optical techniques such as optical absorbance, scattering, surface plasmon resonance (SPR), and fluorescence have been extensively employed for Cancer diagnostic applications. One of the most important diagnostic applications involves utilization of nanoparticles (NPs) for highly specific, sensitive, rapid, multiplexed, and high performance Cancer detection and quantification. The incorporation of NPs with these optical biosensing techniques allow realization of low cost, point-of-care, highly sensitive, and specific early cancer detection technologies, especially for PCa. In this work, the current state-of-the-art, challenges, and efforts made by the researchers for realization of low cost, point-of-care (POC), highly sensitive, and specific NP enhanced optical biosensing technologies for PCa detection using PSA biomarker are discussed and analyzed.

Controlling Charge Transfer from Quantum Dots to Polyelectrolyte Layers Extends Prospective Applications of Magneto-Optical Microcapsules

The layer-by-layer (LbL) deposition approach allows combined incorporation of fluorescent, magnetic, and plasmonic nanoparticles into the shell of polyelectrolyte microcapsules to obtain stimulus-responsive systems whose imaging and drug release functions can be triggered by external stimuli. The combined use of fluorescent quantum dots (QDs) and magnetic nanoparticles (MNPs) yields magnetic-field-driven imaging tools that can be tracked and imaged even deep in tissue when the appropriate type of QDs and wavelength of their excitation are used. QDs are excellent photonic labels for microcapsule encoding due to their close-to-unity photoluminescence (PL) quantum yields, narrow PL emission bands, and tremendous one- and two-photon extinction coefficients. However, the presence of MNPs and electrically charged polyelectrolyte molecules used for the LbL fabrication of magneto-optical microcapsules provokes alterations of the QD optical properties because of the photoinduced charge and energy transfer resulting in QD photodarkening or photobrightening. These lead to variation of the microcapsule PL signal under illumination, which hampers their tracking and quantitative analysis in cells and tissues. Here, we have studied the effects of the structure and spatial arrangement of the nanoparticles within the microcapsule polyelectrolyte shell, the total shell thickness, and the shell surface charge on their PL properties under continuous illumination. The roles of the charge transfer and its main driving forces in the stability of the microcapsules PL signal have been established, and the design of the microcapsules dually encoded with QDs and MNPs providing the strongest and most stable PL has been determined. Controlling the energy transfer from the QDs and MNPs and the charge transfer from QDs to polyelectrolyte layers in the engineering of magneto-optical microcapsules with a bright and stable PL signal extends their applications to long-lasting quantitative fluorescence imaging.

Multiplexed Detection of Cancer Serum Antigens with a Quantum Dot-Based Lab-on-Bead System

A quantum dot (QD)-based lab-on-bead system is a unique tool for multiple analysis of cancer markers in human serum samples by using a flow cytometer. In terms of specificity and sensitivity, this method is comparable with ELISA, the "gold standard" of serological in-clinic detection of single analytes. Fluorescent microspheres encoded with QDs have been used for the quantitative detection of free and total prostate-specific antigen in human serum samples. Developed multiplex assay demonstrates a clear discrimination between serum samples from control subjects and cancer patients. The proposed QD-based method is adaptable and makes it possible to develop numerous clinical tests with decreased duration and cost for early diagnosis of various diseases.

Tempo-spectral multiplexing in flow cytometry with lifetime detection using QD-encoded polymer beads

Semiconductor quantum dots (QDs) embedded into polymer microbeads are known to be very attractive emitters for spectral multiplexing and colour encoding. Their luminescence lifetimes or decay kinetics have been, however, rarely exploited as encoding parameter, although they cover time ranges which are not easily accessible with other luminophores. We demonstrate here the potential of QDs made from II/VI semiconductors with luminescence lifetimes of several 10 ns to expand the lifetime range of organic encoding luminophores in multiplexing applications using time-resolved flow cytometry (LT-FCM). For this purpose, two different types of QD-loaded beads were prepared and characterized by photoluminescence measurements on the ensemble level and by single-particle confocal laser scanning microscopy. Subsequently, these lifetime-encoded microbeads were combined with dye-encoded microparticles in systematic studies to demonstrate the potential of these QDs to increase the number of lifetime codes for lifetime multiplexing and combined multiplexing in the time and colour domain (tempo-spectral multiplexing). These studies were done with a recently developed novel luminescence lifetime flow cytometer (LT-FCM setup) operating in the time-domain, that presents an alternative to reports on phase-sensitive lifetime detection in flow cytometry.

Biofunctionalized Polyelectrolyte Microcapsules Encoded with Fluorescent Semiconductor Nanocrystals for Highly Specific Targeting and Imaging of Cancer Cells

Fluorescent semiconductor nanocrystals or quantum dots (QDs) are characterized by unique optical properties, including a high photostability, wide absorption spectrum, and narrow, symmetric fluorescence spectrum. This makes them attractive fluorescent nanolabels for the optical encoding of microcarriers intended for targeted drug delivery, diagnosis, and imaging of transport processes on the body, cellular, and subcellular levels. Incorporation of QDs into carriers in the form of polyelectrolyte microcapsules through layer-by-layer adsorption of oppositely charged polyelectrolyte polymers yields microcapsules with a bright fluorescence signal and adaptable size, structure, and surface characteristics without using organic solvents. The easily modifiable surface of the microcapsules allows for its subsequent functionalization with capture molecules, such as antibodies, which ensures specific and selective interaction with cells, including tumor cells, with the use of the bioconjugation technique developed here. We obtained stable water-soluble nanolabels based on QDs whose surface was modified with polyethylene glycol (PEG) derivatives and determined their colloidal and optical characteristics. The obtained nanocrystals were used to encode polyelectrolyte microcapsules optically. The microcapsule surface was modified with humanized monoclonal antibodies (Abs) recognizing a cancer marker, epidermal growth factor receptor (EGFR). The possibility of effective, specific, and selective delivery of the microcapsules to tumor cells expressing EGFR has been demonstrated. The results show that the QD-encoded polyelectrolyte microcapsules functionalized with monoclonal Abs against EGFR can be used for targeted imaging and diagnosis.

Nanoparticles With a Specific Size and Surface Charge Promote Disruption of the Secondary Structure and Amyloid-Like Fibrillation of Human Insulin Under Physiological Conditions

Nanoparticles attract much interest as fluorescent labels for diagnostic and therapeutic tools, although their applications are often hindered by size- and shape-dependent cytotoxicity. This cytotoxicity is related not only to the leak of toxic metals from nanoparticles into a biological solution, but also to molecular cytotoxicity effects determined by the formation of a protein corona, appearance of an altered protein conformation leading to exposure of cryptic epitopes and cooperative effects involved in the interaction of proteins and peptides with nanoparticles. In the last case, nanoparticles may serve, depending on their nature, as centers of self-association or fibrillation of proteins and peptides, provoking amyloid-like proteinopathies, or as inhibitors of self-association of proteins, or they can self-assemble on biopolymers as on templates. In this study, human insulin protein was used to analyze nanoparticle-induced proteinopathy in physiological conditions. It is known that human insulin may form amyloid fibers, but only under extreme experimental conditions (very low pH and high temperatures). Here, we have shown that the quantum dots (QDs) may induce amyloid-like fibrillation of human insulin under physiological conditions through a complex process strongly dependent on the size and surface charge of QDs. The insulin molecular structure and fibril morphology have been shown to be modified at different stages of its fibrillation, which has been proved by comparative analysis of the data obtained using circular dichroism, dynamic light scattering, amyloid-specific thioflavin T (ThT) assay, transmission electron microscopy, and high-speed atomic force microscopy. We have found important roles of the QD size and surface charge in the destabilization of the insulin structure and the subsequent fibrillation. Remodeling of the insulin secondary structure accompanied by remarkable increase in the rate of formation of amyloid-like fibrils under physiologically normal conditions was observed when the protein was incubated with QDs of exact specific diameter coated with slightly negative specific polyethylene glycol (PEG) derivatives. Strongly negatively or slightly positively charged PEG-modified QDs of the same specific diameter or QDs of bigger or smaller diameters had no effect on insulin fibrillation. The observed effects pave the way to the control of amyloidosis proteinopathy by varying the nanoparticle size and surface charge.

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).

Cancer Cell Targeting With Functionalized Quantum Dot-Encoded Polyelectrolyte Microcapsules

Imaging agents and drug carriers are commonly targeted toward cancer cell through functionalization with specific recognition molecules. Quantum dots (QDs) are fluorescent semiconductor nanocrystals whose extraordinary brightness and photostability make them attractive for direct fluorescent labeling of biomolecules or optical encoding of the membranes and cells. Here, we analyse the cytotoxicity of QD-encoded microcapsules, validate an approach to the activation of the microcapsule's surface for further functionalization with monoclonal antibody Trastuzumab, a humanized monoclonal antibody targeting the extracellular domain of the human epidermal growth factor receptor 2 (HER2) and already in clinical use for the treatment of HER2 positive breast cancer. In addition, we characterize the cell-specific targeting activity of the resultant bio-conjugate by immunofluorescence assay (IFA) and real-time analysis of interaction of the conjugates with live HER2 overexpressing human breast cancer cells. We demonstrate, that encapsulation of QDs into the polymer shell using the layer-by-layer deposition method yields highly fluorescent polyelectrolyte microcapsules with a homogeneous size distribution and biocompatibility upon in vitro treatment of cancer cells. Carbodiimide surface activation ensures optimal disperse and optical characteristics of the QD-encoded microcapsules before antibody conjugation. The prepared conjugates of the microcapsules with cancer-specific monoclonal antibody targeting HER2 provide sufficiently sensitive and specific antibody-mediated binding of the microcapsules with live cancer cells, which demonstrated their potential as prospective cancer cell–targeting agents.

Sensing with photoluminescent semiconductor quantum dots

Fluorescent sensors benefit from high signal-to-noise and multiple measurement modalities, enabling a multitude of applications and flexibility of design. Semiconductor nanocrystal quantum dots (QDs) are excellent fluorophores for sensors because of their extraordinary optical properties. They have high thermal and photochemical stability compared to organic dyes or fluorescent proteins and are extremely bright due to their large molar cross-sections. In contrast to organic dyes, QD emission profiles are symmetric, with relatively narrow bandwidths. In addition, the size tunability of their emission color, which is a result of quantum confinement, make QDs exceptional emitters with high color purity from the ultra-violet to near infrared wavelength range. The role of QDs in sensors ranges from simple fluorescent tags, as used in immunoassays, to intrinsic sensors that utilize the inherent photophysical response of QDs to fluctuations in temperature, electric field, or ion concentration. In more complex configurations, QDs and biomolecular recognition moieties like antibodies are combined with a third component to modulate the optical signal via energy transfer. QDs can act as donors, acceptors, or both in energy transfer-based sensors using Förster resonance energy transfer (FRET), nanometal surface energy transfer (NSET), or charge or electron transfer. The changes in both spectral response and photoluminescent lifetimes have been successfully harnessed to produce sensitive sensors and multiplexed devices. While technical challenges related to biofunctionalization and the high cost of laboratory-grade fluorimeters have thus far prevented broad implementation of QD-based sensing in clinical or commercial settings, improvements in bioconjugation methods and detection schemes, including using simple consumer devices like cell phone cameras, are lowering the barrier to broad use of more sensitive QD-based devices.

Bioimaging Tools Based on Polyelectrolyte Microcapsules Encoded with Fluorescent Semiconductor Nanoparticles: Design and Characterization of the Fluorescent Properties

Fluorescent imaging is a widely used technique for detecting and monitoring the distribution, interaction, and transformation processes at molecular, cellular, and tissue level in modern diagnostic and other biomedical applications. Unique photophysical properties of fluorescent semiconductor nanocrystals "quantum dots" (QDs) make them advanced fluorophores for fluorescent labeling of biomolecules or optical encoding of microparticles to be used as bioimaging and theranostic agents in targeted delivery, visualization, diagnostics, and imaging. This paper reports on the results of development of an improved approach to the optical encoding of polyelectrolyte microcapsules with stable, covered with the multifunctional polyethyleneglycol derivatives water-soluble QDs, as well as characterization of the optical properties, morphological and structural properties of the encoded microcapsules. The embedding of QDs into the polymer microcapsule membrane through layer-by-layer deposition on a preliminarily formed polymeric polyelectrolyte shell makes it possible to obtain bright fluorescent particles with an adapted charge and size distribution that are distinctly discernible by flow cytometry as individual homogeneous populations. The fluorescent microcapsules developed can be used in further designing bioimaging and theranostic agents sensitive to various external stimuli along with photoexcitation.

Early diagnosis of disease using microbead array technology: A review

Early diagnosis of diseases (before they become advanced and incurable) is essential to reduce morbidity and mortality rates. With the advent of novel technologies in clinical laboratory diagnosis, microbead-based arrays have come to be recognized as an efficient approach, that demonstrates useful advantages over traditional assay methods for multiple disease-related biomarkers. Multiplexed microbead assays provide a robust, rapid, specific, and cost-effective approach for high-throughput and simultaneous screening of many different targets. Biomolecular binding interactions occur after applying a biological sample (such as blood plasma, saliva, cerebrospinal fluid etc.) containing the target analyte(s) to a set of microbeads with different ligand-specificities that have been coded in planar or suspension arrays. The ligand-receptor binding activity is tracked by optical signals generated by means of flow cytometry analysis in the case of suspension arrays, or by image processing devices in the case of planar arrays. In this review paper, we discuss diagnosis of cancer, neurological and infectious diseases by using optically-encoded microbead-based arrays (both multiplexed and single-analyte assays) as a reliable tool for detection and quantification of various analytes.

Comparison of fluorescence excitation modes for cdse semi-conductor quantum dots used in medical research

Fluorescence spectroscopy is a powerful tool used in applied biological and medical research. Colloid semi-conductor quantum dots are promising fluorescent tags for simultaneous detection of different biopathogens. The techniques employing these tags can be improved by selecting the optimal modes for signal excitation and detection. The aim of the present work was to derive a mathematical expression to describe the signal-to-noise ratios in the pulsed and modulated excitation modes. Below, we compare these two modes of fluorescence excitation in ultralow quantities of quantum dots. We demonstrate that modulated excitation should be preferred for CdSe/ZnS quantum dots given that signal accumulation time is over 100 mc and the photosensor is exposed to background light of > 1 μW.

Multiplex measurement of twelve tumor markers using a GMR multi-biomarker immunoassay biosensor

Tumor markers play an important role in the early diagnosis and therapeutic effect monitoring of tumors. Combined detection of multiple tumor markers is a realistic way of improving the sensitivity and specificity of cancer diagnosis. To achieve this, we studied and designed a giant magneto resistance (GMR) multi-biomarker immunoassay biosensor that can simultaneously detect twelve kinds of tumor markers by integrating a GMR sensor chip, a microfluidic device, a magnetic nano-beads label, and a double antibody sandwich immunoassay method. As a proof of concept, the proposed immunosensor was utilized to detect 12 tumor markers (AFP, CEA, CYFRA21-1, NSE, SCC, PG I, PG II, CA19-9, total PSA, free PSA, free-β-hCG, Tg) and to screen patients with lung cancer, liver cancer, digestive tract cancer, prostatic cancer, etc. The immunosensor showed excellent sensitivity, accuracy, precision and stability. Designed as a POCT device, the immunosensor also allows for portability, able to perform rapid detection wherever necessary. As a multi-analyte assay, it provides significant advantages over single-analyte tests in terms of cost per test, labor and convenience. The system's ability to simultaneously measure the concentration of multiple markers in serum samples with excellent sensitivity and accuracy allows the immunosensor to be used for early tumor diagnosis.

Multiplexed microarrays based on optically encoded microbeads

In recent years, there has been growing interest in optically-encoded or tagged functionalized microbeads as a solid support platform to capture proteins or nucleotides which may serve as biomarkers of various diseases. Multiplexing technologies (suspension array or planar array) based on optically encoded microspheres have made possible the observation of relatively minor changes in biomarkers related to specific diseases. The ability to identify these changes at an early stage may allow the diagnosis of serious diseases (e.g. cancer) at a time-point when curative treatment may still be possible. As the overall accuracy of current diagnostic methods for some diseases is often disappointing, multiplexed assays based on optically encoded microbeads could play an important role to detect biomarkers of diseases in a non-invasive and accurate manner. However, detection systems based on functionalized encoded microbeads are still an emerging technology, and more research needs to be done in the future. This review paper is a preliminary attempt to summarize the state-of-the-art concerning diagnostic microbeads; including microsphere composition, synthesis, encoding technology, detection systems, and applications.

Potential Applications of Nanotechnology in Urological Cancer

Nowadays, the potential scope of nanotechnology in uro-oncology (cancers of the prostate, bladder, and kidney) is broad, ranging from drug delivery, prevention, and diagnosis to treatment. Novel drug delivery methods using magnetic nanoparticles, gold nanoparticles, and polymeric nanoparticles have been investigated in prostate cancer. Additionally, renal cancer treatment may be profoundly influenced by applications of nanotechnology principles. Various nanoparticle-based strategies for kidney cancer therapy have been proposed. Partly due to the dilution of drug concentrations by urine production, causing inadequate drug delivery to tumor cells in the treatment of bladder cancer, various multifunctional bladder-targeted nanoparticles have been developed to enhance therapeutic efficiency. In each of these cancer research fields, nanotechnology has shown several advantages over widely used traditional methods. Different types of nanoparticles improve the solubility of poorly soluble drugs, and multifunctional nanoparticles have good specificity toward prostate, renal, and bladder cancer. Moreover, nanotechnology can also combine with other novel technologies to further enhance effectivity. As our understanding of nanotechnologies grows, additional opportunities to improve the diagnosis and treatment of urological cancer are excepted to arise. In this review, we focus on nanotechnologies with potential applications in urological cancer therapy and highlight clinical areas that would benefit from nanoparticle therapy.

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.

Lysyl oxidase activates cancer stromal cells and promotes gastric cancer progression: quantum dot-based identification of biomarkers in cancer stromal cells

Purpose

Semiconductor quantum dots (QDs) are a promising alternative to organic fluorescent dyes for multiplexed molecular imaging of cancer stroma, which have great advantages in holistically analyzing the complex interactions among cancer stromal components in situ.

Patients and methods

A QD probe-based multiplexed spectral molecular imaging method was established for simultaneous imaging. Three tissue microarrays (TMAs) including 184 gastric cancer (GC) tissues were constructed for the study. Multispectral analyses were performed for quantifying stromal biomarkers, such as lysyl oxidase (LOX). The stromal status including infiltrating of immune cells (high density of macrophages), angiogenesis (high density of microvessel density [MVD], low neovessel maturation) and extracellular matrix (ECM) remodeling (low density of type IV collagen, intense expression of matrix metalloproteinase 9 [MMP-9]) was evaluated.

Results

This study compared the imaging features of the QD probe-based single molecular imaging method, immunohistochemistry, and organic dye-based immunofluorescent methods, and showed the advantages of the QD probe-based multiple molecular imaging method for simultaneously visualizing complex components of cancer stroma. The risk of macrophages in high density, high MVD, low neomicrovessel maturation, MMP-9 expression and low type IV collagen was significantly increased for the expression of LOX. With the advantages of the established QD probe-based multiplexed molecular imaging method, the spatial relationship between LOX and stromal essential events could be simultaneously evaluated histologically. Stromal activation was defined and then evaluated. Survival analysis showed that the stromal activation was correlated with overall survival and disease-free survival (P<0.001 for all). The expression of LOX was significantly increased in the intense activation subgroup (P<0.001).

Conclusion

Quantifying assessment of the stroma indicates that the LOX may be a stromal marker for GC and stromal activation, which is not only responsible for the ECM remodeling morphologically, but also for the formation of invasive properties and recurrence. These results support the possibility to integrate morphological and molecular biomarker information for cancer research by the biomedical application of QDs.

Quantum-dot-based suspension microarray for multiplex detection of lung cancer markers: preclinical validation and comparison with the Luminex xMAP® system

A novel suspension multiplex immunoassay for the simultaneous specific detection of lung cancer markers in bronchoalveolar lavage fluid (BALF) clinical samples based on fluorescent microspheres having different size and spectrally encoded with quantum dots (QDEM) was developed. The designed suspension immunoassay was validated for the quantitative detection of three lung cancer markers in BALF samples from 42 lung cancer patients and 10 control subjects. Tumor markers were detected through simultaneous formation of specific immune complexes consisting of a capture molecule, the target antigen, and biotinylated recognition molecule on the surface of the different QDEM in a mixture. The immune complexes were visualized by fluorescently labeled streptavidin and simultaneously analyzed using a flow cytometer. Preclinical validation of the immunoassay was performed and results were compared with those obtained using an alternative 3-plex immunoassay based on Luminex xMAP^® technology, developed on classical organic fluorophores. The comparison showed that the QDEM and xMAP^® assays yielded almost identical results, with clear discrimination between control and clinical samples. Thus, developed QDEM technology can become a good alternative to xMAP^® assays permitting analysis of multiple protein biomarkers using conventional flow cytometers.

Engineering of Optically Encoded Microbeads with FRET-Free Spatially Separated Quantum-Dot Layers for Multiplexed Assays

Quantum dot (QD) encoded microbeads are emerging for multiplexed analysis of biological markers. The quantitative encoding of microbeads prepared with different concentrations of QDs of different colors suffers from resonance energy transfer from the QDs fluorescing at shorter wavelengths to the QDs fluorescing at longer wavelengths. Here, we used the layer-by-layer deposition technique to spatially separate QDs of different colors with several polymer layers so that the distance between them would be larger than the Förster energy transfer radius. We performed fluorescence lifetime measurements to investigate and determine the conditions excluding significant resonance energy transfer between QDs within QD-encoded microbeads. Additionally, the number of QDs adsorbed onto microbeads was systematically established and multilayer structures of the QD-encoded microbead shells were characterized by scanning probe nanotomography. Finally, we prepared eight populations of FRET-free microbeads encoded with QDs of three colors at two intensity levels and demonstrated that all the optical codes are excitable at a single wavelength and may be clearly identified in three channels of a flow cytometer. The developed approach for engineering QD-encoded microbeads that are free from optical artefacts related to inter-QD resonance energy transfer paves the way to quantitative QD-based multiplexed assays.

Anchored protease-activatable polymersomes for molecular diagnostics of metastatic cancer cells

We have designed unique protease-activatable polymersomes (PeptiSomes) forin situquantitative analysis with high selectivity towards MT1-MMP.

The Role of Proteomics in Biomarker Development for Improved Patient Diagnosis and Clinical Decision Making in Prostate Cancer

Prostate Cancer (PCa) is the second most commonly diagnosed cancer in men worldwide. Although increased expression of prostate-specific antigen (PSA) is an effective indicator for the recurrence of PCa, its intended use as a screening marker for PCa is of considerable controversy. Recent research efforts in the field of PCa biomarkers have focused on the identification of tissue and fluid-based biomarkers that would be better able to stratify those individuals diagnosed with PCa who (i) might best receive no treatment (active surveillance of the disease); (ii) would benefit from existing treatments; or (iii) those who are likely to succumb to disease recurrence and/or have aggressive disease. The growing demand for better prostate cancer biomarkers has coincided with the development of improved discovery and evaluation technologies for multiplexed measurement of proteins in bio-fluids and tissues. This review aims to (i) provide an overview of these technologies as well as describe some of the candidate PCa protein biomarkers that have been discovered using them; (ii) address some of the general limitations in the clinical evaluation and validation of protein biomarkers; and (iii) make recommendations for strategies that could be adopted to improve the successful development of protein biomarkers to deliver improvements in personalized PCa patient decision making.

Fluorescent/magnetic micro/nano-spheres based on quantum dots and/or magnetic nanoparticles: preparation, properties, and their applications in cancer studies

The study of cancer is of great significance to human survival and development, due to the fact that cancer has become one of the greatest threats to human health. In recent years, the rapid progress of nanoscience and nanotechnology has brought new and bright opportunities to this field. In particular, the applications of quantum dots (QDs) and magnetic nanoparticles (MNPs) have greatly promoted early diagnosis and effective therapy of cancer. In this review, we focus on fluorescent/magnetic micro/nano-spheres based on QDs and/or MNPs (we may call them "nanoparticle-sphere (NP-sphere) composites") from their preparation to their bio-application in cancer research. Firstly, we outline and compare the main four kinds of methods for fabricating NP-sphere composites, including their design principles, operation processes, and characteristics (merits and limitations). The NP-sphere composites successfully inherit the unique fluorescence or magnetic properties of QDs or MNPs. Moreover, compared with the nanoparticles (NPs) alone, the NP-sphere composites show superior properties, which are also discussed in this review. Then, we summarize their recent applications in cancer research from three aspects, that is: separation and enrichment of target tumor cells or biomarkers; cancer diagnosis mainly through medical imaging or tumor biomarker detection; and cancer therapy via targeted drug delivery systems. Finally, we provide some perspectives on the future challenges and development trends of the NP-sphere composites.

Therapeutic efficacy of nanomedicines for prostate cancer: An update

Recent advances in cancer nanomedicine have attracted remarkable attention in medical sectors. Pharmacologic research on nanomedicines, including targeted cancer therapy, has increased dramatically in the past 5 years. The success stories of nanomedicines in the clinical field include the fabrication of nanomedicines that show maximum loading efficiency into carriers, maximal release kinetics, and minimum toxicity to healthy cells. Nanoparticle-mediated medicines have been developed to specifically target prostate cancer tissue by use of aptamers, antibody targeting, and sustained release of nanomedicines in a dose- and time-dependent manner. Nanomedicines have been developed for therapeutic application in combination with image-guided therapy in real time. The scope of one of these nanomedicines, Abraxane (paclitaxel), may be extended to prostate cancer therapeutic applications for better quality of patient life and longer survival. This review provides an update on the latest directions and developments in nanomedicines for prostate cancer.

Semiconductor and carbon-based fluorescent nanodots: the need for consistency

The need for establishing the bases and definitions of photoluminescent nanodots is discussed and their state-of-the-art in analytical and biomedical research fields is highlighted.

Applications of nanoparticles in cancer medicine and beyond: optical and multimodal in vivo imaging, tissue targeting and drug delivery

INTRODUCTION

Nanotechnology has opened up the way to the engineering of new organized materials endowed with improved performances. In the past decade, engineered nanoparticles (NPs) have been progressively implemented by exploiting synthetic strategies that yield complex materials capable of performing functions with applications also in medicine. Indeed, in the field of 'nanomedicine' it has been explored the possibility to design multifunctional nanosystems, characterized by high analytical performances and stability, low toxicity and specificity towards a given cell target.

AREA COVERED

In this review article, we summarize the advances in the engineering of NPs for biomedical applications, from optical imaging (OI) to multimodal OI and targeted drug delivery. For this purpose, we will provide some examples of how investigations in nanomedicine can support preclinical and clinical research generating innovative diagnostic and therapeutic strategies in oncology.

EXPERT OPINION

The progressive breakthroughs in nanomedicine have supported the development of multifunctional and multimodal NPs. In particular, NPs are significantly impacting the diagnostic and therapeutic strategies since they allow the development of: NP-based OI probes containing more than one modality-specific contrast agent; surface functionalized NPs for specific 'molecular recognition'. Therefore, the design and characterization of innovative NP-based systems/devices have great applicative potential into the medical field.

Quantum dots in nanomedicine: recent trends, advances and unresolved issues

The review addresses the current state of progress in the use of ultra-small nanoparticles from the category of quantum dots (QDs), which presently embraces a widening range of nanomaterials of different nature, including "classical" semiconductor groups III-V and II-VI nanocrystals, along with more recently emerged carbon, silicon, gold and other types of nanoparticles falling into this class of nanomaterials due to their similar physical characteristics such as small size and associated quantum confinement effects. A diverse range of QDs applications in nanomedicine has been extensively summarised previously in numerous publications. Therefore, this review is not intended to provide an all-embracing survey of the well documented QDs uses, but is rather focused on the most recent emerging developments, concepts and outstanding unresolved problematic and sometimes controversial issues. Over 125 publications are overviewed and discussed here in the context of major nanomedicine domains, i.e. medical imaging, diagnostics, therapeutic applications and combination of them in multifunctional theranostic systems.