Quantum Dot Surface Chemistry and Functionalization for Cell Targeting and Imaging

Quantum Dot-Based Nanosensors for In Vitro Detection of Mycobacterium tuberculosis

Despite the existing effective treatment methods, tuberculosis (TB) is the second most deadly infectious disease, its carriers in the latent and active phases accounting for more than 20% of the world population. An effective method for controlling TB and reducing TB mortality is regular population screening aimed at diagnosing the latent form of TB and taking preventive and curative measures. Numerous methods allow diagnosing TB by directly detecting Mycobacterium tuberculosis (M.tb) biomarkers, including M.tb DNA, proteins, and specific metabolites or antibodies produced by the host immune system in response to M.tb. PCR, ELISA, immunofluorescence and immunochemical analyses, flow cytometry, and other methods allow the detection of M.tb biomarkers or the host immune response to M.tb by recording the optical signal from fluorescent or colorimetric dyes that are components of the diagnostic systems. Current research in biosensors is aimed at increasing the sensitivity of detection, a promising approach being the use of fluorescent quantum dots as brighter and more photostable optical tags. Here, we review current methods for the detection of M.tb biomarkers using quantum dot-based nanosensors and summarize data on the M.tb biomarkers whose detection can be made considerably more sensitive by using these sensors.

Visualization of 2D and 3D Tissue Models via Size-Selected Aqueous AgInS/ZnS Quantum Dots

Three-dimensional (3D) spheroid cell cultures of fibroblast (L929) and tumor mammary mouse (4T1) were chosen as in vitro tissue models for tissue imaging of ternary AgInS/ZnS fraction quantum dots (QDs). We showed that the tissue-mimetic morphology of cell spheroids through well-developed cell-cell and cell-matrix interactions and distinct diffusion/transport characteristics makes it possible to predict the effect of ternary AgInS/ZnS fraction QDs on the vital activity of cells while simultaneously comparing with classical two-dimensional (2D) cell cultures. The AgInS/ZnS fractions, emitting in a wide spectral range from 635 to 535 nm with a mean size from ∼3.1 ± 0.8 to ∼1.8 ± 0.4 nm and a long photoluminescence lifetime, were separated from the initial QD ensemble by using antisolvent-induced precipitation. For ternary AgInS/ZnS fraction QDs, the absence of toxicity at different QD concentrations was demonstrated on 2D and 3D cell structures. QDs show a robust correlation between numerous factors: their sizes in biological fluids over time, penetration capabilities into 2D and 3D cell structures, and selectivity with respect to penetration into cancerous and healthy cell spheroids. A reproducible protocol for the preparation of QDs along with their unique biological properties allows us to consider ternary AgInS/ZnS fraction QDs as attractive fluorescent contrast agents for tissue imaging.

Quantum dots as a fluorescent labeling tool for live-cell imaging of Leptospira

Leptospirosis is a global public health problem caused by Gram-negative pathogenic bacteria belonging to the genus Leptospira. The disease is transmitted through the urine of infected animals, which contaminates water and soil, leading to the infection of other animals and humans. Currently, several approaches exist to detect these bacteria; however, a new sensitive method for the live-cell imaging of Leptospira is required. In this study, we report the green synthesis of cadmium telluride quantum dots (CdTe QDs) which are unique fluorescent nanocrystals with a high fluorescence quantum yield capable of modifying cell surfaces and are biocompatible with cells. The fabrication of QDs with concanavalin A (ConA), a carbohydrate-binding lectin and known biological probe for Gram-negative bacteria, produced ConA-QDs which can effectively bind on Leptospira and exhibit strong fluorescence under simple fluorescence microscopy, allowing the live-cell imaging of the bacteria. Overall, we performed the simple synthesis of ConA-QDs and demonstrated their potential use as versatile fluorescent probes for the live-cell imaging of Leptospira. This technique could be further applied to track leptospiral cells and study the infection mechanism, contributing to a more thorough understanding of leptospirosis and how to control it in the future.

Biotin-functionalized nanoparticles: an overview of recent trends in cancer detection

Electrochemical bio-sensing is a potent and efficient method for converting various biological recognition events into voltage, current, and impedance electrical signals. Biochemical sensors are now a common part of medical applications, such as detecting blood glucose levels, detecting food pathogens, and detecting specific cancers. As an exciting feature, bio-affinity couples, such as proteins with aptamers, ligands, paired nucleotides, and antibodies with antigens, are commonly used as bio-sensitive elements in electrochemical biosensors. Biotin-avidin interactions have been utilized for various purposes in recent years, such as targeting drugs, diagnosing clinically, labeling immunologically, biotechnology, biomedical engineering, and separating or purifying biomolecular compounds. The interaction between biotin and avidin is widely regarded as one of the most robust and reliable noncovalent interactions due to its high bi-affinity and ability to remain selective and accurate under various reaction conditions and bio-molecular attachments. More recently, there have been numerous attempts to develop electrochemical sensors to sense circulating cancer cells and the measurement of intracellular levels of protein thiols, formaldehyde, vitamin-targeted polymers, huwentoxin-I, anti-human antibodies, and a variety of tumor markers (including alpha-fetoprotein, epidermal growth factor receptor, prostate-specific Ag, carcinoembryonic Ag, cancer antigen 125, cancer antigen 15-3, etc.). Still, the non-specific binding of biotin to endogenous biotin-binding proteins present in biological samples can result in false-positive signals and hinder the accurate detection of cancer biomarkers. This review summarizes various categories of biotin-functional nanoparticles designed to detect such biomarkers and highlights some challenges in using them as diagnostic tools.

Fluorescent, phosphorescent, magnetic resonance contrast and radioactive tracer labelling of extracellular vesicles

This review focusses on the significance of fluorescent, phosphorescent labelling and tracking of extracellular vesicles (EVs) for unravelling their biology, pathophysiology, and potential diagnostic and therapeutic uses. Various labeling strategies, such as lipid membrane, surface protein, luminal, nucleic acid, radionuclide, quantum dot labels, and metal complex-based stains, are evaluated for visualizing and characterizing EVs. Direct labelling with fluorescent lipophilic dyes is simple but generally lacks specificity, while surface protein labelling offers selectivity but may affect EV-cell interactions. Luminal and nucleic acid labelling strategies have their own advantages and challenges. Each labelling approach has strengths and weaknesses, which require a suitable probe and technique based on research goals, but new tetranuclear polypyridylruthenium(II) complexes as phosphorescent probes have strong phosphorescence, selective staining, and stability. Future research should prioritize the design of novel fluorescent probes and labelling platforms that can significantly enhance the efficiency, accuracy, and specificity of EV labeling, while preserving their composition and functionality. It is crucial to reduce false positive signals and explore the potential of multimodal imaging techniques to gain comprehensive insights into EVs.

Recent Advances in Fluorescent Nanoparticles for Stimulated Emission Depletion Imaging

Stimulated emission depletion (STED) microscopy, as a popular super-resolution imaging technique, has been widely used in bio-structure analysis and resolving the dynamics of biological processes beyond the diffraction limit. The performance of STED critically depends on the optical properties of the fluorescent probes. Ideally, the probe should process high brightness and good photostability, and exhibit a sensitive response to the depletion beam. Organic dyes and fluorescent proteins, as the most widely used STED probes, suffer from low brightness and exhibit rapid photobleaching under a high excitation power. Recently, luminescent nanoparticles (NPs) have emerged as promising fluorescent probes in biological imaging due to their high brightness and good photostability. STED imaging using various kinds of NPs, including quantum dots, polymer dots, carbon dots, aggregation-induced emission dots, etc., has been demonstrated. This review will comprehensively review recent advances in fluorescent NP-based STED probes, discuss their advantages and pitfalls, and outline the directions for future development.

Recent Advances of carbon Pathways for Sustainable Environment development

Carbon dots (CDs) are an emerging type of carbon nanomaterial with strong biocompatibility, distinct chemical and physical properties, and low toxicity. CDs may emit fluorescence in the ultraviolet (UV) to near-infrared (NIR) range, which renders them beneficial for biomedical applications. CDs are usually made from carbon precursors and can be synthesized using top-down and bottom-up methods and it can be easily functionalized using different methods. For specific cases of biomedical applications carbon dot functionalization augments the materials' characteristics. Novel functionalization techniques are still being investigated. This review will look at the benefits of functionalization to attain a high yield and various biological applications. Biomedical applications such as photodynamic and photothermal therapy, biosensing, bioimaging, and antiviral and antibacterial properties will be covered in this review. The future applications of green synthesized carbon dots will be determined in part by this review.

Liquid lasing from solutions of ligand-engineered semiconductor nanocrystals

Semiconductor nanocrystals (NCs) can function as efficient gain materials with chemical versatility because of their surface ligands. Because the properties of NCs in solution are sensitive to ligand-environment interactions, local chemical changes can result in changes in the optical response. However, amplification of the optical response is technically challenging because of colloidal instability at NC concentrations needed for sufficient gain to overcome losses. This paper demonstrates liquid lasing from plasmonic lattice cavities integrated with ligand-engineered CdZnS/ZnS NCs dispersed in toluene and water. By taking advantage of calcium ion-induced aggregation of NCs in aqueous solutions, we show how lasing threshold can be used as a transduction signal for ion detection. Our work highlights how NC solutions and plasmonic lattices with open cavity architectures can serve as a biosensing platform for lab-on-chip devices.

Role of CdTe quantum dots on peripheral Immunocytes and selenoprotein P: immunotoxicity at the molecular and cellular levels

The extensive product and application of cadmium-quantum dots (Cd-QDs), one kind of semiconductor nanomaterials, lead to prolonged exposure to the environment. Cd-QDs have shown good properties in biomedical and imaging-related fields; the safety of Cd-QDs limits the application of these materials and technologies, however. The systematic distribution of CdTe QDs in organisms has been ascertained in previous studies. Nevertheless, it is relatively less reported about the toxicity of CdTe QDs to immune macromolecules and organs. Based on this, immunocytes (including lymphocyte subsets-CD4+ T and CD8+ T cells, splenocytes) and selenoprotein P (SelP) were chosen as targets for CdTe QDs immunotoxicity studies. Results indicate that CdTe QDs induced cytotoxicity to CD4+ T cells, CD8+ T cells and splenocytes by reducing cell viability and causing apoptosis as CdTe QDs and Cd2+ enter cells. At the molecular level, the direct interaction between CdTe QDs and SelP is proved by multispectral measurements, which demonstrated the alteration of protein structure. The combined results show that CdTe QDs induced adverse effects on the immune system at the cellular and molecular levels. This research contributes to a better understanding of CdTe QDs cause harmful damage to the immune system and provides new strategies for the inhibition and treatment of health damages caused by CdTe QDs.

Bioinspired theranostic quantum dots: Paving the road to a new paradigm for cancer diagnosis and therapeutics

Despite extensive research, a complete cure remains lacking for most types of cancer. Nanotechnology-based carriers, such as liposomes, nanoparticles (NPs), dendrimers, nanoemulsions, and other nanocarriers, can target cancer cells, but their in vivo fate is unpredictable. Bioinspired quantum dots (BQDs) offer enhanced aqueous solubility, exceptionally low toxicity, biocompatibility, easy biofunctionalization, and selective cancer targeting. Due to their photoluminescence, high longitudinal relaxation value, photothermal effect upon laser irradiation, generation of singlet oxygen, and production of H2S for gas therapy, BQDs are excellent cancer theranostic agents. In this review, we highlight the theranostic application of, and existing challenges relating to BQDs.

Aptamer-based Upconversion Fluorescence Sensor for Doxorubicin Detection

Doxorubicin is a common chemotherapeutic drug used to treat a variety of cancers. Monitoring the concentration of doxorubicin in human biological fluids is vital for treatment. In this work, we report an aptamer-functionalized, 808 nm-excited core-shell upconversion fluorescence sensor for specific detection of doxorubicin (DOX). Upconversion nanoparticles and DOX are used as energy donors and energy acceptors respectively. Aptamers immobilized on the surface of upconversion nanoparticles act as the molecular recognition element for DOX. The binding of DOX to the immobilized aptamers results in the fluorescence quenching of the upconversion nanoparticles via a fluorescence resonance energy transfer process. The relative fluorescence intensity exhibits a good linear response to DOX concentration in the range of 0.5 μM to 55 μM with a detection limit of 0.5 μM. The aptasensor displays high specificity and anti-interference against other antibiotics, common ions, and biomolecules owing to strong and specific interactions of aptamers towards DOX. The sensor is further applied for the detection of DOX in urine with spike recoveries of nearly 100%.

Novel Förster Resonance Energy Transfer probe with quantum dot for a long-time imaging of active caspases inside individual cells

With the goal to investigate biological phenomena at a single-cell level, we designed, synthesized and tested a molecular probe based on Förster resonance energy transfer (FRET) between a highly luminescent quantum dot (QD) as a donor and a fluorophore or fluorescence quencher as an acceptor linked by a specific peptide. In principle, QD luminescence, effectively dissipated in the probe, is switched on after the cleavage of the peptide by a protease and the release of the quencher. We proposed a novel synthesis strategy of a probe. A two-step synthesis consists of: (i) Conjugation of CdTe QDs functionalized by -COOH groups of succinic acid on the nanoparticle surface with the designed specific peptide (GTADVEDTSC) using a ligand-exchange approach; (ii) A fast, high-yield reaction of amine-reactive succinimidyl group on the BHQ-2 quencher with N-terminal of the peptide. This way, any crosslinking between individual nanoparticles and any nonspecific conjugation bonds are excluded. The analysis of the product after the first step proved a high reaction yield and nearly no occurrence of unreacted QDs, a prerequisite of the specificity of our luminescent probe. Its parameters evaluated as Michaelis-Menten description of enzymatic kinetics are similar to products published by other groups. Our research is focused on the fluorescence microscopy analyses of biologically active molecules, such as proteolytic active caspases, playing important roles in cell signaling regulations in normal and diseased states. Consequently, they are attractive targets for clinical diagnosis and medical therapy. The ultimate goal of our work was to synthesize a new QD luminescent probe for a long-time quantitative monitoring of active caspase-3/7 distribution in apoptotic osteoblastic MC3T3-E1 cells treated with camptothecin. As a result of comparison, our synthetized luminescent probe provides longer imaging times of caspases than commercial products. The probe proved the stability of the luminescence signal inside cells for more than 14 days.

Recent advances in quantum dot-based fluorescence-linked immunosorbent assays

Fluorescence immunoassays have been given considerable attention among the quantitative detection methods in the clinical medicine and food safety testing fields. In particular, semiconductor quantum dots (QDs) have become ideal fluorescent probes for highly sensitive and multiplexed detection due to their unique photophysical properties, and the QD fluorescence-linked immunosorbent assay (FLISA) with high sensitivity, high accuracy, and high throughput has been greatly developed recently. In this manuscript, the advantages of applying QDs to FLISA platforms and some strategies for their application to in vitro diagnostics and food safety are discussed. Given the rapid development of this field, we classify these strategies based on the combination of QD types and detection targets, including traditional QDs or QD micro/nano-spheres-FLISA, and multiple FLISA platforms. In addition, some new sensors based on the QD-FLISA are introduced; this is one of the hot spots in this field. The current focus and future direction of QD-FLISA are also discussed, which provides important guidance for the further development of FLISA.

A Short Review on Miniaturized Biosensors for the Detection of Nucleic Acid Biomarkers

Even today, most biomarker testing is executed in centralized, dedicated laboratories using bulky instruments, automated analyzers, and increased analysis time and expenses. The development of miniaturized, faster, low-cost microdevices is immensely anticipated for substituting for these conventional laboratory-oriented assays and transferring diagnostic results directly onto the patient's smartphone using a cloud server. Pioneering biosensor-based approaches might make it possible to test biomarkers with reliability in a decentralized setting, but there are still a number of issues and restrictions that must be resolved before the development and use of several biosensors for the proper understanding of the measured biomarkers of numerous bioanalytes such as DNA, RNA, urine, and blood. One of the most promising processes to address some of the issues relating to the growing demand for susceptible, quick, and affordable analysis techniques in medical diagnostics is the creation of biosensors. This article critically discusses a short review of biosensors used for detecting nucleic acid biomarkers, and their use in biomedical prognostics will be addressed while considering several essential characteristics.

Semiconductor quantum dots in photoelectrochemical sensors from fabrication to biosensing applications

Semiconductor quantum dots (QDs) are a promising class of nanomaterials for developing new photoelectrodes and photoelectrochemistry systems for energy storage, transfer, and biosensing applications. These materials have unique electronic and photophysical properties and can be used as optical nanoprobes in displays, biosensors, imaging, optoelectronics, energy storage and energy harvesting. Researchers have recently been exploring the use of QDs in photoelectrochemical (PEC) sensors, which involve exciting a QD-interfaced photoactive material with a flashlight source and generating a photoelectrical current as an output signal. The simple surface properties of QDs also make them suitable for addressing issues related to sensitivity, miniaturization, and cost-effectiveness. This technology has the potential to replace current laboratory practices and equipment, such as spectrophotometers, used for testing sample absorption and emission. Semiconductor QD-based PEC sensors offer simple, fast, and easily miniaturized sensors for analyzing a variety of analytes. This review summarizes the various strategies for interfacing QD nanoarchitectures for PEC sensing, as well as their signal amplification. PEC sensing devices, particularly those used for the detection of disease biomarkers, biomolecules (glucose, dopamine), drugs, and various pathogens, have the potential to revolutionize the biomedical field. This review discusses the advantages of semiconductor QD-based PEC biosensors and their fabrication methods, with a focus on disease diagnostics and the detection of various biomolecules. Finally, the review provides prospects and considerations for QD-based photoelectrochemical sensor systems in terms of their sensitivity, speed, and portability for biomedical applications.

Carbon-Based Fluorescent Nano-Biosensors for the Detection of Cell-Free Circulating MicroRNAs

Currently, non-communicable diseases (NCDs) have emerged as potential risks for humans due to adopting a sedentary lifestyle and inaccurate diagnoses. The early detection of NCDs using point-of-care technologies significantly decreases the burden and will be poised to transform clinical intervention and healthcare provision. An imbalance in the levels of circulating cell-free microRNAs (ccf-miRNA) has manifested in NCDs, which are passively released into the bloodstream or actively produced from cells, improving the efficacy of disease screening and providing enormous sensing potential. The effective sensing of ccf-miRNA continues to be a significant technical challenge, even though sophisticated equipment is needed to analyze readouts and expression patterns. Nanomaterials have come to light as a potential solution as they provide significant advantages over other widely used diagnostic techniques to measure miRNAs. Particularly, CNDs-based fluorescence nano-biosensors are of great interest. Owing to the excellent fluorescence characteristics of CNDs, developing such sensors for ccf-microRNAs has been much more accessible. Here, we have critically examined recent advancements in fluorescence-based CNDs biosensors, including tools and techniques used for manufacturing these biosensors. Green synthesis methods for scaling up high-quality, fluorescent CNDs from a natural source are discussed. The various surface modifications that help attach biomolecules to CNDs utilizing covalent conjugation techniques for multiple applications, including self-assembly, sensing, and imaging, are analyzed. The current review will be of particular interest to researchers interested in fluorescence-based biosensors, materials chemistry, nanomedicine, and related fields, as we focus on CNDs-based nano-biosensors for ccf-miRNAs detection applications in the medical field.

Semiconductor Quantum Dots as Target Analytes: Properties, Surface Chemistry and Detection

Since the discovery of Quantum Dots (QDs) by Alexey I. Ekimov in 1981, the interest of researchers in that particular type of nanomaterials (NMs) with unique optical and electrical properties has been increasing year by year. Thus, since 2009, the number of scientific articles published on this topic has not been less than a thousand a year. The increasing use of QDs due to their biomedical, pharmaceutical, biological, photovoltaics or computing applications, as well as many other high-tech uses such as for displays and solid-state lighting (SSL), has given rise to a considerable number of studies about its potential toxicity. However, there are a really low number of reported studies on the detection and quantification of QDs, and these include ICP-MS and electrochemical analysis, which are the most common quantification techniques employed for this purpose. The knowledge of chemical phenomena occurring on the surface of QDs is crucial for understanding the interactions of QDs with species dissolved in the dispersion medium, while it paves the way for a widespread use of chemosensors to facilitate its detection. Keeping in mind both human health and environmental risks of QDs as well as the scarcity of analytical techniques and methodological approaches for their detection, the adaptation of existing techniques and methods used with other NMs appears necessary. In order to provide a multidisciplinary perspective on QD detection, this review focused on three interrelated key aspects of QDs: properties, surface chemistry and detection.

Tissue engineered drug delivery vehicles: Methods to monitor and regulate the release behavior

Tissue engineering is a rapidly evolving, multidisciplinary field that aims at generating or regenerating 3D functional tissues for in vitro disease modeling and drug screening applications or for in vivo therapies. A variety of advanced biological and engineering methods are increasingly being used to further enhance and customize the functionality of tissue engineered scaffolds. To this end, tunable drug delivery and release mechanisms are incorporated into tissue engineering modalities to promote different therapeutic processes, thus, addressing challenges faced in the clinical applications. In this review, we elaborate the mechanisms and recent developments in different drug delivery vehicles, including the quantum dots, nano/micro particles, and molecular agents. Different loading strategies to incorporate the therapeutic reagents into the scaffolding structures are explored. Further, we discuss the main mechanisms to tune and monitor/quantify the release kinetics of embedded drugs from engineered scaffolds. We also survey the current trend of drug delivery using stimuli driven biopolymer scaffolds to enable precise spatiotemporal control of the release behavior. Recent advancements, challenges facing current scaffold-based drug delivery approaches, and areas of future research are discussed.

Carboxymethylcellulose biofunctionalized ternary quantum dots for subcellular-targeted brain cancer nanotheranostics

Among the most lethal forms of cancer, malignant brain tumors persist as one of the greatest challenges faced by oncologists, where nanotechnology-driven theranostics can play a critical role in developing novel polymer-based supramolecular nanoarchitectures with multifunctional and multi-modal characteristics to fight cancer. However, it is virtually a consensus that, besides the complexity of active delivering anticancer drugs by the nanocarriers to the tumor site, the current evaluation methods primarily relying on in vitro assays and in vivo animal models have been accounted for the low translational effectiveness to clinical applications. In this view, the chick chorioallantoic membrane (CAM) assay has been increasingly recognized as one of the best preclinical models to study the effects of anticancer drugs on the tumor microenvironment (TME). Thus, in this study, we designed, characterized, and developed novel hybrid nanostructures encompassing chemically functionalized carboxymethylcellulose (CMC) with mitochondria-targeting pro-apoptotic peptide (KLA) and cell-penetrating moiety (cysteine, CYS) with fluorescent inorganic semiconductor (Ag-In-S, AIS) for simultaneously bioimaging and inducing glioblastoma cancer cell (U-87 MG, GBM) death. The results demonstrated that the CMC-peptide macromolecules produced supramolecular vesicle-like nanostructures with aqueous colloidal stability suitable as nanocarriers for passive and active targeting of cancer tumors. The optical properties and physicochemical features of the nanoconjugates confirmed their suitability as photoluminescent nanoprobes for cell bioimaging and intracellular tracking. Moreover, the results in vitro demonstrated a notable killing activity towards GBM cells of cysteine-bearing CMC conjugates coupled with pro-apoptotic KLA peptides. More importantly, compared to doxorubicin (DOX), a model anticancer drug in chemotherapy that is highly toxic, these innovative nanohybrids nanoconjugates displayed higher lethality against U-87 MG cancer cells. In vivo CAM assays validated these findings where the nanohybrids demonstrated a significant reduction of GBM tumor progression (41% area) and evidenced an antiangiogenic activity. These results pave the way for developing polymer-based hybrid nanoarchitectonics applied as targeted multifunctional theranostics for simultaneous imaging and therapy against glioblastoma while possibly reducing the systemic toxicity and side-effects of conventional anticancer chemotherapeutic agents.

Controlled synthesis of silver-based ternary quantum dots with outstanding luminescence

Quantum dots (QDs) have attracted much attention over the past decades due to their outstanding properties. However, obtaining QDs with excellent photoluminescence and quantum yields (QYs) from their aqueous synthesis is still a big concern. We herein present a green and facile synthesis of AgInS (AIS) QDs and AgInS-ZnS (AIS-ZnS) core-shell QDs using a combination of two capping agents (glutathione and sodium citrate). The temporal evolution of the optical properties is investigated by varying the reaction time and pH of the solution. The results show that the fluorescence intensity of the QDs increases as the reaction time increase, while the emission position blue-shift as the pH of the solution increase. An outstanding photoluminescence quantum yield (PLQY) of 90% is obtained at optimized synthetic conditions. The Fourier transform Infrared studies confirm efficient passivation of the QDs by the capping agents. The XRD analysis reveals that all the materials crystallize in the tetragonal crystalline phase, while the TEM micrographs of AIS-ZnS QDs reveal a spherical shape. The EDS analysis confirms the presence of Silver, Indium, Sulphide, and Zinc elements. The reported synthetic route is facile and eco-friendly.

Insight into Sonoluminescence Augmented by ZnO-Functionalized Nanoparticles

Recent advances in optical imaging techniques rely on the use of nanosized contrast agents for in vitro and in vivo applications. We report on an imaging method based on the inertial cavitation of ultrasound-irradiated water solutions that lead to sonoluminescence (SL), here, newly proposed in combination with semiconductor nanoparticles, in particular, aminopropyl-functionalized zinc oxide nanocrystals. The obtained measurements confirm the ability of such nanocrystals to increase the sonoluminescence emission, together with the ability to modify the SL spectrum when compared to the pure water behavior. In particular, it is shown that the UV component of SL is absorbed by the semiconductor behavior that is also confirmed in different biologically relevant media. Finally, optical images of nanocrystal-assisted SL are acquired for the first time, in particular, in biological buffers, revealing that at low ultrasound intensities, SL is measurable only when the nanocrystals are present in solution. All of these results witness the role of amine-functionalized zinc oxide nanocrystals for sonoluminescence emission, which makes them very good candidates as efficient nanocontrast agents for SL imaging for biological and biomedical applications.

Organic building blocks at inorganic nanomaterial interfaces

This tutorial review presents our perspective on designing organic molecules for the functionalization of inorganic nanomaterial surfaces, through the model of an "anchor-functionality" paradigm. This "anchor-functionality" paradigm is a streamlined design strategy developed from a comprehensive range of materials (e.g., lead halide perovskites, II-VI semiconductors, III-V semiconductors, metal oxides, diamonds, carbon dots, silicon, etc.) and applications (e.g., light-emitting diodes, photovoltaics, lasers, photonic cavities, photocatalysis, fluorescence imaging, photo dynamic therapy, drug delivery, etc.). The structure of this organic interface modifier comprises two key components: anchor groups binding to inorganic surfaces and functional groups that optimize their performance in specific applications. To help readers better understand and utilize this approach, the roles of different anchor groups and different functional groups are discussed and explained through their interactions with inorganic materials and external environments.

Designing Functionalized Polyelectrolyte Microcapsules for Cancer Treatment

The engineering of delivery systems for drugs and contrasting labels ensuring the simultaneous imaging and treatment of malignant tumors is an important hurdle in developing new tools for cancer therapy and diagnosis. Polyelectrolyte microcapsules (MCs), formed by nanosized interpolymer complexes, represent a promising platform for the designing of multipurpose agents, functionalized with various components, including high- and low-molecular-weight substances, metal nanoparticles, and organic fluorescent dyes. Here, we have developed size-homogenous MCs with different structures (core/shell and shell types) and microbeads containing doxorubicin (DOX) as a model anticancer drug, and fluorescent semiconductor nanocrystals (quantum dots, QDs) as fluorescent nanolabels. In this study, we suggest approaches to the encapsulation of DOX at different stages of the MC synthesis and describe the optimal conditions for the optical encoding of MCs with water-soluble QDs. The results of primary characterization of the designed microcarriers, including particle analysis, the efficacy of DOX and QDs encapsulation, and the drug release kinetics are reported. The polyelectrolyte MCs developed here ensure a modified (prolonged) release of DOX, under conditions close to normal and tumor tissues; they possess a bright fluorescence that paves the way to their exploitation for the delivery of antitumor drugs and fluorescence imaging.

Positive Sorption Behaviors in the Ligand Exchanges for Water-Soluble Quantum Dots and a Strategy for Specific Targeting

N,N,N',N'-Tetramethylethylenediamine (TMEDA) and ethylenediamine (EDA) were investigated in-depth in the ligand exchanges for water-soluble CdSe quantum dots (QDs). TMEDA could assist the phase transfer of QDs from apolar solvents to the aqueous solutions as stabilized by mercaptopropionic acid (MPA). We successfully maintained the stability of a series of MPA-capped QDs of different ligand densities for NMR characterizations in aqueous solutions. The proton NMR spectroscopies of MPA of the binding state were used to analyze the ligand densities on the surface of QDs, which were not explored in the past. The binding thermodynamics of the surface ligands of QDs, as analyzed using the Hill equation, demonstrated a positive promoting effect and possible interactions between ligands. EDA in the purification process underwent a spontaneous adsorption with two-stage thermodynamic behaviors as characterized by isothermal titration calorimetry. Due to the positive role of the already adsorbed ligands, excess EDA would further attach to the surface of QDs in the form of non-bonded physisorption, greatly improving the quantum yield (QY) of QDs, and the ligand of this part would almost not change the stability of QDs. We proposed a strategy for the preparation of aqueous QDs with a high QY, followed by fluorescence quenching-enhancement cycles caused by purification-adsorption operations. The strategy made it possible for the preparation of functional QDs with small molecules after purification operations. Kinetics of the sorption of ligands on the surface of QDs were determined by fluorescence spectroscopy. Modified pseudo-second-order kinetics after consideration of the ligand-ligand interaction effect could well analyze the kinetic data. This kinetic model had advantages over the previous ligand exchange model in terms of accuracy, reproducibility, and physical significance. Finally, we used the above strategy for the design of fluorescent QDs for bioimaging of lysosomes, mitochondria, and cancer cells. This work can simplify the preparation of multifunctional fluorescent QDs and avoid complicated ligand design.

Photoluminescent Nanoparticles for Chemical and Biological Analysis and Imaging

Research related to the development and application of luminescent nanoparticles (LNPs) for chemical and biological analysis and imaging is flourishing. Novel materials and new applications continue to be reported after two decades of research. This review provides a comprehensive and heuristic overview of this field. It is targeted to both newcomers and experts who are interested in a critical assessment of LNP materials, their properties, strengths and weaknesses, and prospective applications. Numerous LNP materials are cataloged by fundamental descriptions of their chemical identities and physical morphology, quantitative photoluminescence (PL) properties, PL mechanisms, and surface chemistry. These materials include various semiconductor quantum dots, carbon nanotubes, graphene derivatives, carbon dots, nanodiamonds, luminescent metal nanoclusters, lanthanide-doped upconversion nanoparticles and downshifting nanoparticles, triplet-triplet annihilation nanoparticles, persistent-luminescence nanoparticles, conjugated polymer nanoparticles and semiconducting polymer dots, multi-nanoparticle assemblies, and doped and labeled nanoparticles, including but not limited to those based on polymers and silica. As an exercise in the critical assessment of LNP properties, these materials are ranked by several application-related functional criteria. Additional sections highlight recent examples of advances in chemical and biological analysis, point-of-care diagnostics, and cellular, tissue, and in vivo imaging and theranostics. These examples are drawn from the recent literature and organized by both LNP material and the particular properties that are leveraged to an advantage. Finally, a perspective on what comes next for the field is offered.

Biocompatible chitin-encapsulated CdS quantum dots: Fabrication and antibacterial screening

Chitin-encapsulated cadmium sulfide quantum dots (CdS@CTN QDs) were successfully synthesized from chitin and Cd(NO₃)₂ precursor using the colloidal chemistry method, toward the development of biocompatible and biodegradable QDs for biomedical applications. CdS@CTN QDs exhibited the nanocrystalline cubic CdS encapsulated by α-chitin. The average particle size of CdS@CTN QDs was estimated using empirical Henglein model to be 3.9 nm, while their crystallite size was predicted using Scherrer equation to be 4.3 nm, slightly larger compared to 3-mercaptopropionic acid-capped CdS QDs (3.2 and 3.6 nm, respectively). The mechanism of formation was interpreted based on the spectroscopic data and X-ray crystal structures of CdS@CTN QDs fabricated at different pH values and mass ratios of chitin to Cd(NO₃)₂ precursor. As an important step to explore potential biomolecular and biological applications of CdS@CTN QDs, their antibacterial activities were tested against four different bacterial strains; i.e. Escherichia coli, Bacillus subtillus, Staphylococcus aureus and Pseudomonas aeruginosa.

Two-Photon Fluorescent Nanomaterials and Their Applications in Biomedicine

In recent years, two-photon excited (TPE) materials have attracted great attentions because of their excellent advantages over conventional one-photon excited (OPE) materials, such as deep tissue penetration, three-dimensional spatial selectivity and low phototoxicity. Also, they have been widely applied in lots of field, such as biosensing, imaging, photo-catalysis, photoelectric conversion, and therapy. In this article, we review recent advances in vibrant topic of two-photon fluorescent nanomaterials, including organic molecules, quantum dots (QDs), carbon dots (CDs) and metal nanoclus-ters (MNCs). The optical properties, synthetic methods and important applications of TPE nanomaterials in biomedical field, such as biosensing, imaging and therapy are introduced. Also, the probable challenges and perspectives in the forthcoming development of two-photon fluorescent nanomaterials are addressed.

Quantum dots as targeted doxorubicin drug delivery nanosystems in human lung cancer cells

Background

Lung cancer is one of the most frequently diagnosed cancers all over the world and is also one of the leading causes of cancer-related mortality. The main treatment option for small cell lung cancer, conventional chemotherapy, is characterized by a lack of specificity, resulting in severe adverse effects. Therefore, this study aimed at developing a new targeted drug delivery (TDD) system based on Ag–In–Zn–S quantum dots (QDs). For this purpose, the QD nanocrystals were modified with 11-mercaptoundecanoic acid (MUA), L-cysteine, and lipoic acid decorated with folic acid (FA) and used as a novel TDD system for targeting doxorubicin (DOX) to folate receptors (FARs) on adenocarcinomic human alveolar basal epithelial cells (A549). NIH/3T3 cells were used as FAR-negative controls. Comprehensive physicochemical, cytotoxicity, and genotoxicity studies were performed to characterize the developed novel TDDs.

Results

Fourier transformation infrared spectroscopy, dynamic light scattering, and fluorescence quenching confirmed the successful attachment of FA to the QD nanocrystals and of DOX to the QD–FA nanocarriers. UV–Vis analysis helped in determining the amount of FA and DOX covalently anchored to the surface of the QD nanocrystals. Biological screening revealed that the QD–FA–DOX nanoconjugates had higher cytotoxicity in comparison to the other forms of synthesized QD samples, suggesting the cytotoxic effect of DOX liberated from the QD constructs. Contrary to the QD–MUA–FA–DOX nanoconjugates which occurred to be the most cytotoxic against A549 cells among others, no such effect was observed for NIH/3T3 cells, confirming FARs as molecular targets. In vitro scratch assay also revealed significant inhibition of A549 cell migration after treatment with QD–MUA–FA–DOX. The performed studies evidenced that at IC50 all the nanoconjugates induced significantly more DNA breaks than that observed in nontreated cells. Overall, the QD–MUA–FA–DOX nanoconjugates showed the greatest cytotoxicity and genotoxicity, while significantly inhibiting the migratory potential of A549 cells.

Conclusion

QD–MUA–FA–DOX nanoconjugates can thus be considered as a potential drug delivery system for the effective treatment of adenocarcinomic human alveolar basal epithelial cells.

Nanotheranostics through Mitochondria-targeted Delivery with Fluorescent Peptidomimetic Nanohybrids for Apoptosis Induction of Brain Cancer Cells

Overview: Malignant brain tumors remain one of the greatest challenges faced by health professionals and scientists among the utmost lethal forms of cancer. Nanotheranostics can play a pivotal role in developing revolutionary nanoarchitectures with multifunctional and multimodal capabilities to fight cancer. Mitochondria are vital organelles to eukaryotic cells, which have been recognized as a significant target in cancer therapy where, by damaging the mitochondria, it will cause irreparable cell death or apoptosis. Methods: We designed and produced novel hybrid nanostructures comprising a fluorescent semiconductor core (AgInS2, AIS) and cysteine-modified carboxymethylcellulose (termed thiomer, CMC_Cys) conjugated with mitochondria-targeting peptides (KLA) forming a macromolecular shell for combining bioimaging and for inducing brain cancer cell (U-87 MG) death. Results: The optical and physicochemical properties of the nanoconjugates demonstrated suitability as photoluminescent nanostructures for cell bioimaging and intracellular tracking. Additionally, the results proved a remarkable killing activity towards glioblastoma cells of cysteine-bearing CMC conjugates coupled with KLA peptides through the half-maximal effective concentration values, approximately 70-fold higher compared to the conjugate analogs without Cys residues. Moreover, these thiomer-based pro-apoptotic drug nanoconjugates displayed higher lethality against U-87 MG cancer cells than doxorubicin, a model drug in chemotherapy, although extremely toxic. Remarkably, these peptidomimetic nanohybrids demonstrated a relative "protective effect" regarding healthy cells while maintaining high killing activity towards malignant brain cells. Conclusion: These findings pave the way for developing hybrid nanoarchitectures applied as targeted multifunctional platforms for simultaneous imaging and therapy against cancer while minimizing the high systemic toxicity and side-effects of conventional drugs in anticancer chemotherapy.

Nanoengineering with RAFT polymers: from nanocomposite design to applications

Reversible addition–fragmentation chain-transfer (RAFT) polymerization is a powerful tool for the precise formation of macromolecular building blocks that can be used for the construction of well-defined nanocomposites.

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.

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.

Graphene Quantum Dots as Flourishing Nanomaterials for Bio-Imaging, Therapy Development, and Micro-Supercapacitors

Graphene quantum dots (GQDs) are considerably a new member of the carbon family and shine amongst other members, thanks to their superior electrochemical, optical, and structural properties as well as biocompatibility features that enable us to engage them in various bioengineering purposes. Especially, the quantum confinement and edge effects are giving GQDs their tremendous character, while their heteroatom doping attributes enable us to specifically and meritoriously tune their prospective characteristics for innumerable operations. Considering the substantial role offered by GQDs in the area of biomedicine and nanoscience, through this review paper, we primarily focus on their applications in bio-imaging, micro-supercapacitors, as well as in therapy development. The size-dependent aspects, functionalization, and particular utilization of the GQDs are discussed in detail with respect to their distinct nano-bio-technological applications.

Prospects on Nano-Based Platforms for Antimicrobial Photodynamic Therapy Against Oral Biofilms

Objective: This review clusters the growing field of nano-based platforms for antimicrobial photodynamic therapy (aPDT) targeting pathogenic oral biofilms and increase interactions between dental researchers and investigators in many related fields. Background data: Clinically relevant disinfection of dental tissues is difficult to achieve with aPDT alone. It has been found that limited penetrability into soft and hard dental tissues, diffusion of the photosensitizers, and the small light absorption coefficient are contributing factors. As a result, the effectiveness of aPDT is reduced in vivo applications. To overcome limitations, nanotechnology has been implied to enhance the penetration and delivery of photosensitizers to target microorganisms and increase the bactericidal effect. Materials and methods: The current literature was screened for the various platforms composed of photosensitizers functionalized with nanoparticles and their enhanced performance against oral pathogenic biofilms. Results: The evidence-based findings from the up-to-date literature were promising to control the onset and the progression of dental biofilm-triggered diseases such as dental caries, endodontic infections, and periodontal diseases. The antimicrobial effects of aPDT with nano-based platforms on oral bacterial disinfection will help to advance the design of combination strategies that increase the rate of complete and durable clinical response in oral infections. Conclusions: There is enthusiasm about the potential of nano-based platforms to treat currently out of the reach pathogenic oral biofilms. Much of the potential exists because these nano-based platforms use unique mechanisms of action that allow us to overcome the challenging of intra-oral and hard-tissue disinfection.

Bioluminescence-Based Energy Transfer Using Semiconductor Quantum Dots as Acceptors

Bioluminescence resonance energy transfer (BRET) is the non-radiative transfer of energy from a bioluminescent protein donor to a fluorophore acceptor. It shares all the formalism of Förster resonance energy transfer (FRET) but differs in one key aspect: that the excited donor here is produced by biochemical means and not by an external illumination. Often the choice of BRET source is the bioluminescent protein Renilla luciferase, which catalyzes the oxidation of a substrate, typically coelenterazine, producing an oxidized product in its electronic excited state that, in turn, couples with a proximal fluorophore resulting in a fluorescence emission from the acceptor. The acceptors pertinent to this discussion are semiconductor quantum dots (QDs), which offer some unrivalled photophysical properties. Amongst other advantages, the QD's large Stokes shift is particularly advantageous as it allows easy and accurate deconstruction of acceptor signal, which is difficult to attain using organic dyes or fluorescent proteins. QD-BRET systems are gaining popularity in non-invasive bioimaging and as probes for biosensing as they don't require external optical illumination, which dramatically improves the signal-to-noise ratio by avoiding background auto-fluorescence. Despite the additional advantages such systems offer, there are challenges lying ahead that need to be addressed before they are utilized for translational types of research.

Fluorescent Labeling of Proteins of Interest in Live Cells: Beyond Fluorescent Proteins

Live cell imaging brings us into a new era of direct visualization of biological processes and molecular dynamics in real time. To visualize dynamic cellular processes and virus-host interactions, fluorescent labeling of proteins of interest is often necessary. Fluorescent proteins are widely used for protein imaging, but they have some intrinsic deficiencies such as big size, photobleaching, and spectrum restriction. Thus, a variety of labeling strategies have been established and continuously developed. To protect the natural biological function(s) of the protein of interest, especially in viral life cycle, in vivo labeling requires smaller-sized tags, more specificity, and lower cytotoxicity. Here, we briefly summarized the principles, development, and their applications mainly in the virology field of three strategies for fluorescent labeling of proteins of interest including self-labeling enzyme derivatives, stainable peptide tags, and non-canonical amino acid incorporation. These labeling techniques greatly expand the fluorescent labeling toolbox and provide new opportunities for imaging biological processes.

Peptide- and Drug-Functionalized Fluorescent Quantum Dots for Enhanced Cell Internalization and Bacterial Debilitation

This report illustrates a strategy for designing a nanoconjugate derived vector that efficiently delivers antimicrobial drug directly into bacterial cells. The nanoconjugate comprises of negatively charged CDTe@CdS quantum dots (QDs) with its surface functionalized using cationic BP-100 (KKLFKKILKYL-amide), a known cell-penetrating peptide (CPP), via electrostatic approach. The interactions between QD and CPP in QD-functionalized CPPs (QD-CPP) have been well analyzed using fluorescence spectroscopy, gel electrophoresis, and ζ-potential analysis. The QD-CPP conjugate was internalized into Gram negative (Escherichia coli) as well as Gram positive (Staphylococcus aureus) bacterial strains with confocal studies exhibiting a strong signal in tested microorganisms. Further, to check the applicability of QD-CPP conjugate as a delivery vector for generating an effective therapeutics, ampicillin molecules were conjugated on QD-CPP surface to generate QD-CPP-Amp conjugate. The CPP and drug molecules on the surface of QDs were well quantified using high-performance liquid chromatography (HPLC) data. It was observed that the internalization and bacterial debilitation of the QD-CPP-Amp conjugate is 2- to 4-fold effective as compared to that of bare ampicillin. The morphological changes to the bacterial cells upon the treatment with QD-CPP-Amp conjugates were noted with no cytotoxic effect on tested mammalian cell lines. The results inferred that the proposed QD-CPP vector provides a targeted and proficient approach for cellular internalization of cargo (drug) in bacterial cells with effective tracking through florescent QDs.

Shell-Free Copper Indium Sulfide Quantum Dots Induce Toxicity in Vitro and in Vivo

Semiconductor quantum dots (QDs) are attractive fluorescent contrast agents for in vivo imaging due to their superior photophysical properties, but traditional QDs comprise toxic materials such as cadmium or lead. Copper indium sulfide (CuInS₂, CIS) QDs have been posited as a nontoxic and potentially clinically translatable alternative; however, previous in vivo studies utilized particles with a passivating zinc sulfide (ZnS) shell, limiting direct evidence of the biocompatibility of the underlying CIS. For the first time, we assess the biodistribution and toxicity of unshelled CIS and partially zinc-alloyed CISZ QDs in a murine model. We show that bare CIS QDs breakdown quickly, inducing significant toxicity as seen in organ weight, blood chemistry, and histology. CISZ demonstrates significant, but lower, toxicity compared to bare CIS, while our measurements of core/shell CIS/ZnS are consistent with literature reports of general biocompatibility. In vitro cytotoxicity is dose-dependent on the amount of metal released due to particle degradation, linking degradation to toxicity. These results challenge the assumption that removing heavy metals necessarily reduces toxicity: indeed, we find comparable in vitro cytotoxicity between CIS and CdSe QDs, while CIS caused severe toxicity in vivo compared to CdSe. In addition to highlighting the complexity of nanotoxicity and the differences between the in vitro and in vivo outcomes, these unexpected results serve as a reminder of the importance of assessing the biocompatibility of core QDs absent the protective ZnS shell when making specific claims of compositional biocompatibility.

Colloidal synthesis of tunably luminescent AgInS-based/ZnS core/shell quantum dots as biocompatible nano-probe for high-contrast fluorescence bioimaging

Tremendous demands for simultaneous imaging of biological entities, along with the drawback of photobleaching in fluorescent dyes, have encouraged scientists to apply novel and non-toxic colloidal quantum dots (QDs) in biomedical researches. Herein, a novel aqueous-phase approach for the preparation of multicomponent In-based QDs is reported. Absorption and photoluminescence emission spectra of the as-prepared QDs were tuned by alteration of QDs' composition as Zn-Ag-In-S/ZnS, Ag-In-S/ZnS and Cu-Ag-In-S/ZnS core/shell QDs. In order to reach reproducibly intense and tunable light-emissive colloidal QDs with green, amber, and red color, various optimization steps were carefully performed. The structural characterizations such as EDX, ICP-AES, XRD, TEM and FT-IR measurements were also carried out to demonstrate the success of the present method to prepare extremely quantum-confined QDs capped with functional groups. Then, to ensure their promising biomedical applications, the generated intracellular reactive oxygen species (ROS) by QDs were quantitatively and qualitatively measured in dark conditions and under 405 nm laser irradiation. Our results verified an enhancement in the generation of reactive oxygen species (ROS) and cytotoxic effects in the presence of laser irradiation while their muted toxic effects in dark conditions confirmed biocompatible properties of un-excited In-based QDs. Moreover, bioimaging analysis revealed strong merits of the suggested synthetic route to achieve ideal fluorescent QDs as bright/multi-color optical nano-probes in imaging and transporting pumps in the cell membrane. This further emphasized the potential ability of the present AgInS-based/ZnS QDs in obtaining required results as theranostic agents for simultaneous treatment and imaging of cancer. The harmonized advantages in simplicity and effectiveness of synthesis procedure, excellent structural/optical properties enriched with confirmed biomedical merits in high contrast imaging and potential treatment highlight the present work.

Tumor-specific fluorescent Cdots-based nanotheranostics by acid-labile conjugation of doxorubicin onto reduction-cleavable Cdots-based nanoclusters

Carbon quantum dots (Cdots) have attracted more and more interests in bioimaging and tumor theranostics. However, their practical application has been limited due to the small particle size and non-tumor-specific fluorescence. Here, reduction-cleavable disulfide-linked Cdots-based nanoclusters were fabricated to conjugate doxorubicin (DOX) via an acid-labile hydrazone bond. Owing to the pH and reduction dual-stimuli responsiveness, the proposed Cdots-based nanotheranostics possessed unique tumor-specific fluorescent property and tumor-specific controlled drug release performance, indicating their promising potential for the in-situ real-time fluorescent monitoring of therapeutic response in future tumor therapy.

Semiconductor Quantum Dots as Components of Photoactive Supramolecular Architectures

Luminescent quantum dots (QDs) are colloidal semiconductor nanocrystals consisting of an inorganic core covered by a molecular layer of organic surfactants. Although QDs have been known for more than thirty years, they are still attracting the interest of researchers because of their unique size-tunable optical and electrical properties arising from quantum confinement. Moreover, the controlled decoration of the QD surface with suitable molecular species enables the rational design of inorganic-organic multicomponent architectures that can show a vast array of functionalities. This minireview highlights the recent progress in the use of surface-modified QDs - in particular, those based on cadmium chalcogenides - as supramolecular platforms for light-related applications such as optical sensing, triplet photosensitization, photocatalysis and phototherapy.

Selection and Characterization of CSFV-Specific Single-Domain Antibodies and Their Application along with Immunomagnetic Nanobeads and Quantum Dots

Outbreak of classical swine fever (CSF) results in high mortality and thus causes severe economic losses in the swine industry. Single-domain antibody (sdAb) is the smallest antigen-binding molecule derived from camelid heavy-chain antibodies and has the potential to be used as a molecular probe for detection of CSF virus (CSFV). In this study, two sdAb fragments against the E2 antigen of CSFV were obtained, expressed in vitro. The functional characteristics analysis indicated that the recombinant sdAbE2-1 and sdAbE2-2 have excellent binding activity, specificity, and high affinity with equilibrium constant value of 3.34 × 10⁻⁷ and 1.35 × 10⁻⁸ M to E2 protein. Then, sdAbE2s were conjugated with quantum dots (QD)/AF488 to synthesize two molecular probes for imaging CSFV distribution in cells. The sdAbE2-1 was also labeled with carboxyl-magnetic beads to construct immunomagnetic nanobeads (IMNBs) able to capture CSFV virions and recombinant E2 protein. QD/AF455-sdAbE2s probes colocalised with CSFV virions in swine testis cells, and IMNBs were used as a detection template and proved to bind specifically with CSFV virions and E2 protein. The selected sdAb fragments and sdAb-based molecular probes may be used for the rapid identification of CSFV during field outbreaks and for research on CSFV and host interactions.

Immunochromatographic assay for melamine based on luminescent quantum dot beads as signaling probes

To screen and detect the harmful substance melamine (MEL), a quantum-dot-bead-based immunochromatographic assay (QB-ICA) was formulated. After optimization, calibration was performed within the linear range from 0.06 to 0.28 ng mL⁻¹, with limit of detection (LOD) of 0.04 ng mL⁻¹. The LOD was 35 times lower than that of ICA that used colloidal gold nanoparticles (LOD = 1.4 ng mL⁻¹) and 40 times lower than that of the assay based on quantum dots (LOD = 1.6 ng mL⁻¹). In the detection of MEL in spiked pure milk using the proposed QB-ICA strategy, the LOD (LOD = 0.19 ng mL⁻¹) of the samples with the proposed pretreatment was 18.4 times lower than those of the samples without pretreatment (LOD = 3.5 ng mL⁻¹). The performance and practicability of the proposed QB-ICA system was validated; the obtained results reveal that QB-ICA is comparable with the conventional enzyme-linked immunosorbent assay (ELISA) method, but with enhanced applicability. Given its high sensitivity and practicability, the QB-ICA strategy could become a worthwhile alternative for the rapid, sensitive, and quantitative onsite detection of harmful substances, facilitating food safety monitoring.

An immunochromatographic assay using quantum dot beads as a label was established for melamine detection in milk with fast and effective pretreatment.

Nanoparticle-based Cell Trackers for Biomedical Applications

The continuous or real-time tracking of biological processes using biocompatible contrast agents over a certain period of time is vital for precise diagnosis and treatment, such as monitoring tissue regeneration after stem cell transplantation, understanding the genesis, development, invasion and metastasis of cancer and so on. The rationally designed nanoparticles, including aggregation-induced emission (AIE) dots, inorganic quantum dots (QDs), nanodiamonds, superparamagnetic iron oxide nanoparticles (SPIONs), and semiconducting polymer nanoparticles (SPNs), have been explored to meet this urgent need. In this review, the development and application of these nanoparticle-based cell trackers for a variety of imaging technologies, including fluorescence imaging, photoacoustic imaging, magnetic resonance imaging, magnetic particle imaging, positron emission tomography and single photon emission computing tomography are discussed in detail. Moreover, the further therapeutic treatments using multi-functional trackers endowed with photodynamic and photothermal modalities are also introduced to provide a comprehensive perspective in this promising research field.

Green synthesis of highly luminescent biotin-conjugated CdSe quantum dots for bioimaging applications

An efficient green protocol for the synthesis of luminescent biotin-conjugated CdSe quantum dots has been developed for bioimaging applications.