Bioconjugation of luminescent silicon quantum dots for selective uptake by cancer cells

Conventional quantum dots have great potential in cancer-related imaging and diagnostic applications; however, these applications are limited by concerns about the inherent toxicity of their core materials (e.g., cadmium, lead). Virtually all imaging applications require conjugation of the imaging agent to a biologically active molecule to achieve selective uptake or binding. Here, we report a study of biocompatible silicon quantum dots covalently attached to biomolecules including lysine, folate, antimesothelin, and transferrin. The particles possess desirable physical properties, surface chemistry, and optical properties. Folate- and antimesothelin-conjugated silicon quantum dots show selective uptake into Panc-1 cells. This study contributes to the preclinical evaluation of silicon quantum dots and further demonstrates their potential as an imaging agent for cancer applications.     

纳米材料在生物医学检测中的应用

纳米技术的兴起,对生物医学领域的变革产生了深远的影响。纳米材料是纳米技术发展的重要基础,它具有许多传统材料所不具备的独特的理化性质,因此在生物医学、传感器等重要技术领域有着广泛的应用前景。对几类常见的纳米材料包括纳米金、量子点、磁性纳米粒子、碳纳米管和硅纳米线在蛋白质、DNA、金属离子以及生物相关分子检测方面的应用进行综述。     

Renal clearance of quantum dots

The field of nanotechnology holds great promise for the diagnosis and treatment of human disease. However, the size and charge of most nanoparticles preclude their efficient clearance from the body as intact nanoparticles. Without such clearance or their biodegradation into biologically benign components, toxicity is potentially amplified and radiological imaging is hindered. Using intravenously administered quantum dots in rodents as a model system, we have precisely defined the requirements for renal filtration and urinary excretion of inorganic, metal-containing nanoparticles. Zwitterionic or neutral organic coatings prevented adsorption of serum proteins, which otherwise increased hydrodynamic diameter by >15 nm and prevented renal excretion. A final hydrodynamic diameter <5.5 nm resulted in rapid and efficient urinary excretion and elimination of quantum dots from the body. This study provides a foundation for the design and development of biologically targeted nanoparticles for biomedical applications.     

Better together: Strategies based on magnetic particles and quantum dots for improved biosensing

Novel technologies and strategies for sensitive detection of biological responses in healthcare, food and environmental monitoring continue to be a priority. The present review focuses on bioassay development based on the simultaneous use of quantum dots and magnetic beads. Due to the outstanding characteristics of both particles for biosensing applications and the large number of publications using a combined approach, we aim to provide a comprehensive overview of the literature on different bioassays, the most recent advances and innovative strategies on the topic, together with an analysis of the main drawbacks encountered and potential solutions offered, with a special emphasis on the requirements that the transfer of technologies from the laboratory to the market will demand for future commercialization of biodevices. Several procedures used in immunoassays and nucleic acid-based bioassays for the detection of pathogens and biomarkers are discussed. The improvement of current approaches together with novel multiplex detection systems and nanomaterials-based research, including the use of multimodal nanoparticles, will contribute to simpler and more sensitive bioanalyses.     

Emerging nanoproteomics approaches for disease biomarker detection: a current perspective

Availability of genome sequence of human and different pathogens has advanced proteomics research for various clinical applications. One of the prime goals of proteomics is identification and characterization of biomarkers for cancer and other fatal human diseases to aid an early diagnosis and monitor disease progression. However, rapid detection of low abundance biomarkers from the complex biological samples under clinically relevant conditions is extremely difficult, and it requires the development of ultrasensitive, robust and high-throughput technological platform. In order to overcome several technical limitations associated with sensitivity, dynamic range, detection time and multiplexing, proteomics has started integrating several emerging disciplines such as nanotechnology, which has led to the development of a novel analytical platform known as 'nanoproteomics'. Among the diverse classes of nanomaterials, the quantum dots, gold nanoparticles, carbon nanotubes and silicon nanowires are the most promising candidates for diagnostic applications. Nanoproteomics offers several advantages such as ultralow detection, short assay time, high-throughput capability and low sample consumption. In this article, we have discussed the application of nanoproteomics for biomarker discovery in various diseases with special emphasis on various types of cancer. Furthermore, we have discussed the prospects, merits and limitations of nanoproteomics.     

Plasmonic Tuning of Photoluminescence from Semiconducting Quantum Dot Assemblies

We report tuning of photoluminescence enhancement and quenching from closed packed monolayers of cadmium selenide quantum dots doped with gold nanoparticles. Plasmon-mediated control of the emission intensity from the monolayers is achieved by varying the size and packing density of the quantum dots as well as the doping concentration of gold nanoparticles. We observe a unique packing density dependent crossover from enhancement to quenching and vice versa for fixed size of quantum dots and doping concentration of gold nanoparticles. We suggest that this behavior is indicative of a crossover from single particle to collective emission from quantum dots mediated by gold nanoparticles.     

量子点在新药开发中的应用

由于具有优异的光学特性,量子点在生物医学领域内的研究和应用取得了一些有意义的进展,同时也引起了新药开发人员的兴趣.本文概述了量子点在新药开发中所具有的优势,分析了量子点在药物传输、药物筛选和药靶确证方面的潜在应用,进一步讨论了当前量子点应用于新药开发存在的问题和不足.     

Stimuli-responsive nanocarriers for intracellular delivery

The emergence of different nanoparticles (NPs) has made a significant revolution in the field of medicine. Different NPs in the form of metallic NPs, dendrimers, polymeric NPs, carbon quantum dots and liposomes have been functionalized and used as platforms for intracellular delivery of biomolecules, drugs, imaging agents and nucleic acids. These NPs are designed to improve the pharmacokinetic properties of the drug, improve their bioavailability and successfully surpass physiological or pathological obstacles in the biological system so that therapeutic efficacy is achieved. In this review I present some of the current approaches used in intracellular delivery systems, with a focus on various stimuli-responsive nanocarriers, including cell-penetrating peptides, to highlight their various biomedical applications.     

生物分子的纳米粒子标记和检测技术

生物分子的标记和检测一直是生物分析领域的重要内容 .近年来 ,纳米材料与生物检测技术的结合 ,使得生物分子的检测有了重要的发展 ,这一交叉学科现已成为生物分析领域最具活力的研究方向 .对近期出现的新型纳米粒子标记物的性质、检测原理、特点和应用进行了评述 ,并分析了用该标记物进行分析的可能发展方向     

Application of Solanum lycopersicum (tomato) hairy roots for production of passivated CdS nanocrystals with quantum dot properties

Semiconductor quantum dot particles have a wide range of applications in medicine, bioassays, computing and photovoltaics. Biological synthesis is an attractive approach for mass production of quantum dots as cells have the capacity to passivate the particles with organic ligands. In this work, hairy roots of Solanum lycopersicum (tomato) were used to produce CdS nanoparticles with quantum dot properties. Treatment of the roots with 100 μM Cd during the mid-growth phase of batch culture elicited cellular responses for Cd detoxification without affecting root growth. A combination of freeze-drying and freeze-thawing of the roots was used to extract Cd from the biomass; anion-exchange chromatography was then applied to selectively remove metal–phytochelatin complexes. Size-fractionation using gel filtration allowed the recovery of phytochelatin-capped Cd- and inorganic sulphide-containing nanoparticles displaying the size and size-dependent optical/electronic properties of CdS quantum dots. At 4–10 nm in diameter, these particles fluoresced at wavelengths corresponding to blue-violet on the colour spectrum and exhibited a high level of photostability with prolonged excitation. Whereas 69% of the Cd extracted from the roots was associated with phytochelatin peptides, the maximum yield of CdS nanocrystals with quantum dot properties was 1.4% of the total Cd taken up into the biomass. This work demonstrates a new culture-based approach for the biosynthesis of metallo-organic semiconductor quantum dots using hairy roots.     

Synthesis of Cd-free InP/ZnS Quantum Dots Suitable for Biomedical Applications

Fluorescent nanocrystals, specifically quantum dots, have been a useful tool for many biomedical applications. For successful use in biological systems, quantum dots should be highly fluorescent and small/monodisperse in size. While commonly used cadmium-based quantum dots possess these qualities, they are potentially toxic due to the possible release of Cd²⁺ ions through nanoparticle degradation. Indium-based quantum dots, specifically InP/ZnS, have recently been explored as a viable alternative to cadmium-based quantum dots due to their relatively similar fluorescence characteristics and size. The synthesis presented here uses standard hot-injection techniques for effective nanoparticle growth; however, nanoparticle properties such as size, emission wavelength, and emission intensity can drastically change due to small changes in the reaction conditions. Therefore, reaction conditions such temperature, reaction duration, and precursor concentration should be maintained precisely to yield reproducible products. Because quantum dots are not inherently soluble in aqueous solutions, they must also undergo surface modification to impart solubility in water. In this protocol, an amphiphilic polymer is used to interact with both hydrophobic ligands on the quantum dot surface and bulk solvent water molecules. Here, a detailed protocol is provided for the synthesis of highly fluorescent InP/ZnS quantum dots that are suitable for use in biomedical applications.     

Protein microarrays and novel detection platforms

The field of proteomics has undergone rapid advancements over the last decade and protein microarrays have emerged as a promising technological platform for the challenging task of studying complex proteomes. This gel-free approach has found an increasing number of applications due to its ability to rapidly and efficiently study thousands of proteins simultaneously. Different protein microarrays, including capture arrays, reverse-phase arrays, tissue microarrays, lectin microarrays and cell-free expression microarrays, have emerged, which have demonstrated numerous applications for proteomics studies including biomarker discovery, protein interaction studies, enzyme-substrate profiling, immunological profiling and vaccine development, among many others. The need to detect extremely low-abundance proteins in complex mixtures has provided motivation for the development of sensitive, real-time and multiplexed detection platforms. Conventional label-based approaches like fluorescence, chemiluminescence and use of radioactive isotopes have witnessed substantial advancements, with techniques like quantum dots, gold nanoparticles, dye-doped nanoparticles and several bead-based methods now being employed for protein microarray studies. In order to overcome the limitations posed by label-based technologies, several label-free approaches like surface plasmon resonance, carbon nanotubes and nanowires, and microcantilevers, among others, have also advanced in recent years, and these methods detect the query molecule itself. The scope of this article is to outline the protein microarray techniques that are currently being used for analytical and function-based proteomics and to provide a detailed analysis of the key technological advances and applications of various detection systems that are commonly used with microarrays.     

Influence of the nature of quantum dot surface cations on interactions with DNA

Quantum dots are semiconductor nanoparticles that are approximately 1-10nm in diameter, similar to small proteins, and their photoluminescence is sensitive to the presence and nature of adsorbates. We have deployed these nanomaterials as luminescent probes of DNA structure. Sequence dependent conformational flexibility of DNA is of great interest due to its implications for drug-DNA and DNA-protein interactions. The counterion atmosphere surrounding DNA plays an important role in its structure, dynamics, and packaging. In this paper, we investigate the effect that various monovalent and divalent cations have on the binding of 4.5 nm CdS quantum dots to oligonucleotides that have sequence-directed intrinsic structure.     

Mortalin imaging in normal and cancer cells with quantum dot immuno-conjugates

Quantum dots are the nanoparticles that are recently emerging as an alternative to organic fluorescence probes in cell biology and biomedicine, and have several predictive advantages. These include their ⑴broad absorption spectra allowing visualization with single light source, ⑵exceptional photo-stability allowing long term studies and ⑶narrow and symmetrical emission spectrum that is controlled by their size and material composition. These unique properties allow simultaneous excitation of different size of quantum dots with a single excitation light source, their simultaneous resolution and visualization as different colors. At present there are only a few studies that have tested quantum dots in cellular imaging. We describe here the use of quantum dots in mortalin imaging of normal and cancer cells. Mortalin staining pattern with quantum dots in both normal and cancer cells mimicked those obtained with organic florescence probes and were considerably stable.     

Functionalized quantum dots to quantify NADPH and their use for NADP+-dependent biocatalyzed transformations

Quantum dots are semiconducting nanoparticles that can be prepared with interesting optical properties. The fluorescent properties of quantum dots are one of the key advantages for their use as optical labels for biorecognition events and biocatalytic processes. We have prepared semiconductor quantum dots conjugated with Nile Blue (NB), and demonstrate that NB-functionalized quantum dots can act as versatile probes to analyze different biocatalyzed transformations, and can be used for the quantitative detection of NADPH as well as NADH. This approach provides a new path for the optical detection of NAD(P)H and for the quantitative analysis of NAD(P)(+)-dependent biotransformations.     

Self-Assembling Complexes of Quantum Dots and scFv Antibodies for Cancer Cell Targeting and Imaging

Semiconductor quantum dots represent a novel class of fluorophores with unique physical and chemical properties which could enable a remarkable broadening of the current applications of fluorescent imaging and optical diagnostics. Complexes of quantum dots and antibodies are promising visualising agents for fluorescent detection of selective biomarkers overexpressed in tumor tissues. Here we describe the construction of self-assembling fluorescent complexes of quantum dots and anti-HER1 or anti-HER2/neu scFv antibodies and their interactions with cultured tumor cells. A binding strategy based on a very specific non-covalent interaction between two proteins, barnase and barstar, was used to connect quantum dots and the targeting antibodies. Such a strategy allows combining the targeting and visualization functions simply by varying the corresponding modules of the fluorescent complex.     

Using cadmium telluride quantum dots as a proton flux sensor and applying to detect H9 avian influenza virus

Semiconductor nanocrystals, often known as quantum dots, have been used extensively for a wide range of applications in bioimaging and biosensing. In this article, we report that the pH-sensitive cadmium telluride (CdTe) quantum dots (QDs) were used as a proton sensor to detect proton flux that was driven by ATP synthesis in chromatophores. To confirm that these QD-labeled chromatophores were responding to proton flux pumping driven by ATP synthesis, N,N'-dicyclohexylcarbodiimide (DCCD) was used as an inhibitor of ATPase activity. Furthermore, we applied the QD-labeled chromatophores as a virus detector to detect the H9 avian influenza virus based on antibody-antigen reaction. The results showed that this QD virus detector could be a new virus-detecting device.     

One‐pot synthesis of fluorescent nitrogen‐doped carbon dots with good biocompatibility for cell labeling

Here we report an easy and economical hydrothermal carbonization approach to synthesize the fluorescent nitrogen‐doped carbon dots (N‐CDs) that was developed using citric acid and triethanolamine as the precursors. The synthesis conditions were optimized to obtain the N‐CDs with superior fluorescence performances. The as‐prepared N‐CDs are monodispersed sphere nanoparticles with good water solubility, and exhibited strong fluorescence, favourable photostability and excitation wavelength‐dependent behavior. Furthermore, the in vitro cytotoxicity and cellular labeling of N‐CDs were investigated using the rat glomerular mesangial cells. The results showed the N‐CDs have more inconspicuous cytotoxicity and better biosafety in comparison with ZnSe quantum dots, although both targeted the cells successfully. Considering their admirable photostability, low toxicity and good compatibility, the as‐obtained N‐CDs could have potential applications in biosensors, cellular imaging, and other fields.     

Targeted Bifunctional Proteins and Hybrid Nanoconstructs for Cancer Diagnostics and Therapies

In this review, the authors' works published within the past 5 years devoted to the development of bifunctional hybrid nanostructures based on the targeting polypeptides and nanoparticles of various origin (quantum dots, nanogold, nanodiamonds, upconversion nanoparticles, magnetic and polymer nanoparticles) as modules that ensure visualization and various damaging effects on cancer cells are surveyed and the prospects of their application in theranostics and precision medicine have been contemplated.