Biocompatible quantum dot-antibody conjugate for cell imaging, targeting and fluorometric immunoassay: crosslinking, characterization and applications

Fluorescence Immunoassay of Prostate-Specific Antigen Using 3D Paddle Screw-Type Devices and Their Rotating System

In this paper, we present a sensitive and highly reproducible fluorescence immunosensor for detecting PSA in human serum. A unique feature of this study is that it uses creatively designed paddle screw-type devices and their custom-made rotating system for PSA immunoassay. The paddle screw devices were designed to maximize the surface-to-volume ratio over which the immunoassay reaction could occur to improve detection sensitivity. This paddle screw-based immunoassay offers an accessible and efficient method with a short analysis time of less than 30 min. Active rotation of the paddle screw plays a crucial role in fast and accurate analysis of PSA. Additionally, a paddle screw-based immunoassay and subsequent fluorescence detection using a custom prototype fluorescence detection system were compared to a typical well plate-based immunoassay system. Results of PSA detection in human serum showed that the detection sensitivity through the paddle screw-based analysis improved about five times compared to that with a well plate-based analysis.

Green Synthesis of Carboxymethyl Chitosan-Based CuInS2 QDs with Luminescent Response toward Pb2+ Ion and Its Application in Bioimaging

Polysaccharide-based QDs have attracted great attention in the field of biological imaging and diagnostics. How to get rid of the high heavy metal toxicity resulting from conventional Cd- and Pb-based QDs is now the main challenge. Herein, we offer a simple and environmentally friendly approach for the "direct" interaction of thiol-ending carboxymethyl chitosan (CMC-SH) with metal salt precursors, resulting in CuInS2 QDs based on polysaccharides. A nucleation-growth mechanism based on the LaMer model can explain how CMC-CuInS2 QDs are formed. As-prepared water-soluble CMC-CuInS2 QDs exhibit monodisperse particles with sizes of 5.5-6.5 nm. CMC-CuInS2 QDs emit the bright-green fluorescence at 530 nm when excited at 466 nm with the highest quantum yield of ∼18.0%. Meanwhile, the fluorescence intensity of CMC-CuInS2 QD aqueous solution is quenched with the addition of Pb2+ and the minimal limit of detection is as little as 0.4 nM. Furthermore, due to its noncytotoxicity, great biocompatibility, and strong biorecognition ability, CMC-CuInS2 QDs can be exploited as a possible cell membrane imaging reagent. The imaging studies also demonstrate that CMC-CuInS2 QDs are suitable for Pb2+ detection in live cells and living organisms (zebrafish). Thus, this work offers such an efficient, green, and practical method for creating low-toxicity and water-soluble QD nanosensors for a sensitive and selective detection of toxic metal ion in live cells and organisms.

A glass matrices-assisted quantum dots-based biosensor for selective capturing and detection of Escherichia coli

Bacterial contamination of water and food is a grave health concern rendering humans quite vulnerable to disease(s), and proving, at times, fatal too. Exploration of the novel diagnostic tools is, accordingly, highly called for to ensure rapid detection of the pathogenic bacteria, particularly Escherichia coli. The current manuscript, accordingly, reports the use of silane-functionalized glass matrices and antibody-conjugated cadmium telluride (CdTe) quantum dots (QDs) for efficient detection of E. coli. Synthesis of QDs (size: 5.4-6.8 nm) using mercaptopropionic acid (MPA) stabilizer yielded stable photoluminescence (∼62%), corroborating superior fluorescent characteristics. A test sample, when added to antibody-conjugated matrices, followed by antibody-conjugated CdTe-MPA QDs, formed a pathogen-antibody QDs complex. The latter, during confocal microscopy, demonstrated rapid detection of the selectively captured pathogenic bacteria (10 microorganism cells/10 μL) with enhanced sensitivity and specificity. The work, overall, encompasses establishment and design of an innovative detection platform in microbial diagnostics for rapid capturing of pathogens in water and food samples.

Multifunctional magnetic nanocarriers for delivery of siRNA and shRNA plasmid to mammalian cells: Characterization, adsorption and release behaviors

Nucleic acids are promising candidates for treating various diseases. Nucleic acid is negatively charged and hydrophilic; therefore, it is not efficiently taken up by cells. Successful gene therapy requires the development of carriers for efficient delivery of gene-expressing DNA plasmid and small interfering RNA (siRNA) duplex. In this study, we developed MNP-CA-PEI, a citric acid (CA)-modified magnetic nanoparticle (MNP) cross-linked with polyethyleneimine (PEI), using carbonyldiimidazole as the crosslinker. The physical properties of MNP-CA-PEI (particle size, morphologies, surface coating, surface potentials, magnetic hystereses, superparamagnetic behaviors, and infrared spectra) were systematically characterized by transmission electron microscopy imaging, dynamic light scattering, thermogravimetric analysis, superconducting quantum interference device, and Fourier transform infrared spectroscopy. The adsorption isotherm and kinetics were determined by the Langmuir model, the Freundlich model, a pseudo-first-order equation, and a pseudo-second-order equation. MNP-CA-PEI could form polyelectrolyte complexes with negatively charged nucleic acids, enabling the efficient delivery of nucleic acids into cells. Using MNP-CA-PEI nanoparticles, we magnetically triggered the intracellular delivery of green fluorescence protein (GFP)-expressing DNA plasmid, plasmid-expressing short hairpin RNA (shRNA) against GFP, or siRNA targeting GFP into different cell lines. Nucleic acid/MNP-CA-PEI displayed the enhanced cellular uptake of GFP-expressing DNA plasmid, and it improved the silencing efficiency of shRNA and siRNA, determined by fluorescence imaging. Gene knockdowns mediated by shRNA and siRNA were also confirmed by a quantitative real-time polymerase chain reaction. MNP-CA-PEI delivered nucleic acids into cytosol through caveolae-mediated endocytosis. This study introduces a new MNP functionalization that can be used for the magnetically driven intracellular delivery of nucleic acids.

Realization of a Model-Free Pathway for Quantum Dot-Protein Interaction Beyond Classical Protein Corona or Protein Complex

Although in recent times nanoparticles (NPs) are being used in various biological applications, their mechanism of binding interactions still remains hazy. Usually, the binding mechanism is perceived to be mediated through either the protein corona (PC) or protein complex (PCx). Herein, we report that the nanoparticle (NP)-protein interaction can also proceed via a different pathway without forming the commonly observed PC or PCx. In the present study, the NP-protein interaction between less-toxic zinc-silver-indium-sulfide (ZAIS) quantum dots (QDs) and bovine serum albumin (BSA) was investigated by employing spectroscopic and microscopic techniques. Although the analyses of data obtained from fluorescence and thermodynamic studies do indicate the binding between QDs and BSA, they do not provide clear experimental evidence in favor of PC or PCx. Quite interestingly, high-resolution transmission electron microscopy (HRTEM) studies have shown the formation of a new type of species where BSA protein molecules are adsorbed onto some portion of a QD surface rather than the entire surface. To the best of our knowledge, we believe that this is the first direct experimental evidence in favor of a model-free pathway for NP-protein interaction events. Thus, the outcome of the present study, through experimental evidence, clearly suggests that NP-protein interaction can proceed by following a pathway that is different from classical PC and PCx.

Copolyelectrolyte-Based Nanocapsules for Oral Monoclonal Antibody Therapy: A Mesoscale Modeling Survey

Antibody therapy generally requires parenteral injection to attain the required bioavailability and pharmacokinetics, but improved formulations may slow enzymatic degradation of the antibody in the gastrointestinal tract, permitting the use of noninvasive oral delivery. Rationally designed carrier materials can potentially improve therapeutic activity both by shielding fragile biopharmaceuticals from proteolytic degradation and targeting specific receptors in vivo. One potentially useful class of protein carriers is block copolyelectrolytes, one polyelectrolyte plus one neutral hydrophilic polymer block, that self-assemble into stable micelles, providing a simple and biocompatible nanocapsule separating the protein from the outer medium. Here, we develop and implement an integrated mesoscale model to design molecular structures for block copolyelectrolyte nanocapsules predicted to protect Trastuzumab, an antibody used to treat breast cancer, in the low pH gastrointestinal tract and to selectively release this antibody in the more neutral intestinal environment. The simulations show a tightly packed self-assembled core-shell structure at pH = 3 that is ruptured and dynamically reassembled into a weaker structure at pH = 7. Our model identifies that the designed block copolyelectrolyte characteristics, such as block length ratio, can control the level of drug protection and release in vivo, providing simple design rules for engineering polyelectrolyte-based formulations that may allow oral administration of targeted antibody chemotherapies.

TGFBR3 supports anoikis through suppressing ATF4 signaling

Epithelial morphogenesis and oncogenic transformation can cause loss of cell adhesion, and detached cells are eliminated by anoikis. Here, we reveal that transforming growth factor beta receptor 3 (TGFBR3) acts as an anoikis mediator through the coordination of activating transcription factor 4 (ATF4). In breast cancer, TGFBR3 is progressively lost, but elevated TGFBR3 is associated with a histologic subtype characterized by cellular adhesion defects. Dissecting the impact of extracellular matrix (ECM) deprivation, we demonstrate that ECM loss promotes TGFBR3 expression, which in turn differentiates cell aggregates to a prosurvival phenotype and drives the intrinsic apoptotic pathway. We demonstrate that inhibition of TGFBR3 impairs epithelial anoikis by activating ATF4 signaling. These preclinical findings provide a rationale for therapeutic inhibition of ATF4 in the subgroup of breast cancer patients with low TGFBR3 expression.

Quantum Dot-Antibody Conjugates for Immunofluorescence Studies of Biomolecules and Subcellular Structures

Quantum dots, or nanoscale semiconductors, are one of the most important materials for various research and development purposes. Due to their advantageous photoluminescence and electronic properties, namely, their unique photostability, high brightness, narrow emission spectra from visible to near-infrared wavelengths, convey them significant advantages over widely used fluorochromes, including organic dyes, fluorescent probes. Quantum dots are a unique instrument for a wide range of immunoassays with antibodies. The paper provides an overview of the developed and already applied methods of quantum dot surface modification, quantum dots conjugation to different antibodies (non-covalent, direct covalent linkage or with the use of special adapter molecules), as well as practical examples of recent quantum dot-antibody applications in the immunofluorescence microscopy for cell and cell structure imaging, fluorescent assays for biomolecules detection and in diagnostics of various diseases. The review presents advantages of quantum dot-antibody conjugation technology over the existing methods of immunofluorescence studies and a forward look into its potential prospects in biological and biomedical research.

A fluorescent biosensor based on quantum dot-labeled streptavidin and poly-l-lysine for the rapid detection of Salmonella in milk

Salmonella, as a common foodborne pathogen in dairy products, poses a great threat to human health. We studied a new detection method based on quantum dots (QD). A fluorescent biosensor with multiple fluorescent signal amplification based on a streptavidin (SA) biotin system and the polyamino linear polymer poly-l-lysine (PLL) were established to detect Salmonella in milk. First, Salmonella was captured on a black 96-well plate with paired Salmonella mAb to form a double-antibody sandwich. Second, SA was immobilized on biotin-modified mAb by SA-biotin specific bond. Then, the biotin-modified polylysine (BT-PLL) was bound on SA and specifically bonded again through the SA-biotin system. Finally, water-soluble CdSe/ZnS QD-labeled SA was added to a black 96-well plate for covalent coupling with BT-PLL. The fluorescent signal was amplified in a dendritic manner by the layer-by-layer overlap of SA and biotin and the covalent coupling of biotinylated PLL. Under optimal conditions, the detection limit was 4.9 × 10³ cfu/mL in PBS. The detection limit was 10 times better than that of the conventional sandwich ELISA. In addition, the proposed biosensor was well specific and could be used for detecting Salmonella in milk samples.

Current advances in bio-fabricated quantum dots emphasising the study of mechanisms to diversify their catalytic and biomedical applications

Quantum dots (QDs), owing to their single atom-like electronic structure due to quantum confinement, are often referred to as artificial atoms. This unique physical property results in the diverse functions exhibited by QDs. A wide array of applications have been achieved by the surface functionalization of QDs, resulting in exceptional optical, antimicrobial, catalytic, cytotoxic and enzyme inhibition properties. Ordinarily, traditionally prepared QDs are subjected to post synthesis functionalization via a variety of methods, such as ligand exchange or covalent and non-covalent conjugation. Nevertheless, solvent toxicity, combined with the high temperature and pressure conditions during the preparation of QDs and the low product yield due to multiple steps in the functionalization, limit their overall use. This has driven scientists to investigate the development of greener, environmental friendly and cost-effective methods that can circumvent the complexity and strenuousness associated with traditional processes of bio-functionalization. In this review, a detailed analysis of the methods to bio-prepare pre-functionalized QDs, with elucidated mechanisms, and their application in the areas of catalysis and biomedical applications has been conducted. The environmental and health and safety aspects of the bio-derived QDs have been briefly discussed to unveil the future of nano-commercialization.

Antifungal Nano-Therapy in Veterinary Medicine: Current Status and Future Prospects

The global recognition for the potential of nanoproducts and processes in human biomedicine has given impetus for the development of novel strategies for rapid, reliable, and proficient diagnosis, prevention, and control of animal diseases. Nanomaterials exhibit significant antifungal and antimycotoxin activities against mycosis and mycotoxicosis disorders in animals, as evidenced through reports published over the recent decade and more. These nanoantifungals can be potentially utilized for the development of a variety of products of pharmaceutical and biomedical significance including the nano-scale vaccines, adjuvants, anticancer and gene therapy systems, farm disinfectants, animal husbandry, and nutritional products. This review will provide details on the therapeutic and preventative aspects of nanoantifungals against diverse fungal and mycotoxin-related diseases in animals. The predominant mechanisms of action of these nanoantifungals and their potential as antifungal and cytotoxicity-causing agents will also be illustrated. Also, the other theragnostic applications of nanoantifungals in veterinary medicine will be identified.

Metal Nanoparticle and Quantum Dot Tags for Signal Amplification in Electrochemical Immunosensors for Biomarker Detection

With the increasing importance of healthcare and clinical diagnosis, as well as the growing demand for highly sensitive analytical instruments, immunosensors have received considerable attention. In this review, electrochemical immunosensor signal amplification strategies using metal nanoparticles (MNPs) and quantum dots (Qdots) as tags are overviewed, focusing on recent developments in the ultrasensitive detection of biomarkers. MNPs and Qdots can be used separately or in combination with other nanostructures, while performing the function of nanocarriers, electroactive labels, or catalysts. Thus, different functions of MNPs and Qdots as well as recent advances in electrochemical signal amplification are discussed. Additionally, the methods most often used for antibody immobilization on nanoparticles, immunoassay formats, and electrochemical methods for indirect biomarker detection are overviewed.

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.

Conjugation of Carboxylated Graphene Quantum Dots with Cecropin P1 for Bacterial Biosensing Applications

Biosensors that can accurately and rapidly detect bacterial concentrations in solution are important for potential applications such as assessing drinking water safety. Meanwhile, quantum dots have proven to be strong candidates for biosensing applications in recent years because of their strong light emission properties and their ability to be modified with a variety of functional groups for the detection of different analytes. Here, we investigate the use of conjugated carboxylated graphene quantum dots (CGQDs) for the detection of Escherichia coli using a biosensing assay that focuses on measuring changes in fluorescence intensity. We have further developed this assay into a novel, compact, field-deployable biosensor focused on rapidly measuring changes in absorbance to determine E. coli concentrations. Our CGQDs were conjugated with cecropin P1, a naturally produced antibacterial peptide that facilitates the attachment of CGQDs to E. coli cells; to our knowledge, this is the first instance of cecropin P1 being used as a biorecognition element for quantum dot biosensors. As such, we confirm the structural modification of these conjugated CGQDs in addition to analyzing their optical characteristics. Our findings have the potential to be used in situations where rapid, reliable detection of bacteria in liquids, such as drinking water, is required, especially given the low range of E. coli concentrations (103 to 106 CFU/mL) within which our two biosensing assays have collectively been shown to function.

Rhodamine B dye is efficiently degraded by polypropylene-based cerium wet catalytic materials

Polypropylene-based cerium wet catalytic materials (Ce/PPNW-g-PAA) were prepared through ultraviolet grafting and ion exchange technology. They were used as effective and reusable heterogeneous catalysts for rhodamine B (RhB) degradation. The physicochemical properties of Ce/PPNW-g-PAA were characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), specific surface area measurements (BET), and X-ray photoelectron spectroscopy (XPS). The catalytic capacity of the Ce/PPNW-g-PAA-H2O2 system for the removal of RhB was tested in comparison with several other systems, which demonstrated that Ce/PPNW-g-PAA effectively promoted the oxidation and degradation of RhB by catalytic wet H2O2 oxidation. The results of the RhB degradation showed that Ce/PPNW-g-PAA exhibited excellent degradation performance by achieving a high removal rate for RhB (97.5%) at an initial RhB concentration of 100 mg L-1, H2O2 dosage of 5.0 mmol, Ce/PPNW-g-PAA dosage of 0.15 g L-1, and initial pH of 5.0 at 298 K. The degradation of RhB by Ce/PPNW-g-PAA conformed to the first-order kinetic reaction model. Consecutive experiments performed with the Ce/PPNW-g-PAA sample showed little activity decay, further confirming the high stability of the catalyst. In addition, the possible degradation mechanism of RhB was also investigated by XPS and electron paramagnetic resonance. The results suggested that Ce3+ and hydroxyl radical played important roles during the RhB degradation process.

Effective and Efficient Pretreatment of Polyimide Substrates by Capacitively Coupled Plasma for Coating the Composites of Tetracycline-Imprinted Polymers and Quantum Dots: Comparison with Chemical Pretreatment

Composites of tetracycline (Tc)-imprinted polymethacrylates and quantum dots have been coated on chemically pretreated polyimide substrates (PIs) as fluorescent sensors. In this study, PIs were pretreated by capacitively coupled plasma (CCP) before coating the same composites on them. For the first time, to fabricate sensors by plasma modification of PIs, the CCP conditions, including plasma gas, flow rate, radio frequency generation power, and duration time, the fabrication details, including coating, baking, and stripping steps, and the sample loading process were optimized to perform a linear decrease in fluorescent intensity with Tc concentrations in the range of 5.0-3000 μM (R2 = 0.9995) with a limit of detection of 0.2 μM (S/N = 3, relative standard deviation (RSD) = 2.2%). The selectivity of the stripped PIs was evaluated by the imprinting factors (IFs) for Tc (IF = 7.2), other Tc analogues (IF = 3.4-5.3), and steroids (IF ≈ 1) and by the recoveries of 5.0 μM Tc from bovine serum albumin at 300 μg∙mL-1 (98%, RSD = 3.2%), fetal bovine serum at 1.5 ppt (98%, RSD = 2.8%), and liquid milk (94.5%, RSD = 5.3%). The superiority of the present plasma-treated-based sensor over the previous chemically-treated one in fabrication efficiency and detection effectiveness was clear.