The effects of composition and surface chemistry on the toxicity of quantum dots

Research Progress of Heavy-Metal-Free Quantum Dot Light-Emitting Diodes

At present, heavy-metal-free quantum dot light-emitting diodes (QLEDs) have shown great potential as a research hotspot in the field of optoelectronic devices. This article reviews the research on heavy-metal-free quantum dot (QD) materials and light-emitting diode (LED) devices. In the first section, we discussed the hazards of heavy-metal-containing quantum dots (QDs), such as environmental pollution and human health risks. Next, the main representatives of heavy-metal-free QDs were introduced, such as InP, ZnE (E=S, Se and Te), CuInS2, Ag2S, and so on. In the next section, we discussed the synthesis methods of heavy-metal-free QDs, including the hot injection (HI) method, the heat up (HU) method, the cation exchange (CE) method, the successful ionic layer adsorption and reaction (SILAR) method, and so on. Finally, important progress in the development of heavy-metal-free QLEDs was summarized in three aspects (QD emitter layer, hole transport layer, and electron transport layer).

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.

Anisotropic Heavy-Metal-Free Semiconductor Nanocrystals: Synthesis, Properties, and Applications

Heavy-metal (Cd, Hg, and Pb)-containing semiconductor nanocrystals (NCs) have been explored widely due to their unique optical and electrical properties. However, the toxicity risks of heavy metals can be a drawback of heavy-metal-containing NCs in some applications. Anisotropic heavy-metal-free semiconductor NCs are desirable replacements and can be realized following the establishment of anisotropic growth mechanisms. These anisotropic heavy-metal-free semiconductor NCs can possess lower toxicity risks, while still exhibiting unique optical and electrical properties originating from both the morphological and compositional anisotropy. As a result, they are promising light-emitting materials in use various applications. In this review, we provide an overview on the syntheses, properties, and applications of anisotropic heavy-metal-free semiconductor NCs. In the first section, we discuss hazards of heavy metals and introduce the typical heavy-metal-containing and heavy-metal-free NCs. In the next section, we discuss anisotropic growth mechanisms, including solution-liquid-solid (SLS), oriented attachment, ripening, templated-assisted growth, and others. We discuss mechanisms leading both to morphological anisotropy and to compositional anisotropy. Examples of morphological anisotropy include growth of nanorods (NRs)/nanowires (NWs), nanotubes, nanoplatelets (NPLs)/nanosheets, nanocubes, and branched structures. Examples of compositional anisotropy, including heterostructures and core/shell structures, are summarized. Third, we provide insights into the properties of anisotropic heavy-metal-free NCs including optical polarization, fast electron transfer, localized surface plasmon resonances (LSPR), and so on, which originate from the NCs' anisotropic morphologies and compositions. Finally, we summarize some applications of anisotropic heavy-metal-free NCs including catalysis, solar cells, photodetectors, lighting-emitting diodes (LEDs), and biological applications. Despite the huge progress on the syntheses and applications of anisotropic heavy-metal-free NCs, some issues still exist in the novel anisotropic heavy-metal-free NCs and the corresponding energy conversion applications. Therefore, we also discuss the challenges of this field and provide possible solutions to tackle these challenges in the future.

Emerging ultrasmall luminescent nanoprobes for in vivo bioimaging

Photoluminescence (PL) imaging has become a fundamental tool in disease diagnosis, therapeutic evaluation, and surgical navigation applications. However, it remains a big challenge to engineer nanoprobes for high-efficiency in vivo imaging and clinical translation. Recent years have witnessed increasing research efforts devoted into engineering sub-10 nm ultrasmall nanoprobes for in vivo PL imaging, which offer the advantages of efficient body clearance, desired clinical translation potential, and high imaging signal-to-noise ratio. In this review, we present a comprehensive summary and contrastive discussion of emerging ultrasmall luminescent nanoprobes towards in vivo PL bioimaging of diseases. We first summarize size-dependent nano-bio interactions and imaging features, illustrating the unique attributes and advantages/disadvantages of ultrasmall nanoprobes differentiating them from molecular and large-sized probes. We also discuss general design methodologies and PL properties of emerging ultrasmall luminescent nanoprobes, which are established based on quantum dots, metal nanoclusters, lanthanide-doped nanoparticles, and silicon nanoparticles. Then, recent advances of ultrasmall luminescent nanoprobes are highlighted by surveying their latest in vivo PL imaging applications. Finally, we discuss existing challenges in this exciting field and propose some strategies to improve in vivo PL bioimaging and further propel their clinical applications.

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.

Fabrication of tumor targeting rare-earth nanocrystals for real-time NIR-IIb fluorescence imaging-guided breast cancer precise surgery

The near-infrared fluorescence imaging has been integrated into the operating room to guide tumor resection, potentially reducing the positive margin rates in breast-conserving surgery (BCS). Relative to the widely used first near-infrared fluorescence imaging, imaging in the second near-infrared (NIR-II) region possesses higher contrast and deeper tissue penetration, particularly in the NIR-IIb window, offering many new opportunities for imaging-guided BCS. Here, we fabricated the c(RGDfC) functionalized erbium-based rare-earth nanoparticles (ErNPs@cRGD) with superior optical property in NIR-IIb region. Owing to deeper tissue penetration and efficient tumor targeting, ErNPs@cRGD-based NIR-IIb fluorescence imaging achieved enhanced signal-to-background ratios in tumor visualization, which was able to guide more complete tumor resection, identify multiple microtumors and distinguish malignant lesions from normal tissues in various mice models. Based on these, this NIR-IIb imaging strategy for surgical navigation can significantly reduce positive margin rates and improve prognosis, laying a foundation for the clinical resection of breast cancer.

Organic quantum dots: An ultrasmall nanoplatform for cancer theranostics

Tumours are the second leading cause of death globally, generating alterations in biological interactions and, as a result, malfunctioning of crucial genetic traits. Technological advancements have made it possible to identify tumours at the cellular level, making transcriptional gene variations and other genetic variables more easily investigated. Standard chemotherapy is seen as a non-specific treatment that has the potential to destroy healthy cells while also causing systemic toxicity in individuals. As a result, developing new technologies has become a pressing necessity. QDs are semiconductor particles with diameters ranging from 2 to 10 nanometers. QDs have grabbed the interest of many researchers due to their unique characteristics, including compact size, large surface area, surface charges, and precise targeting. QD-based drug carriers are well known among the many nanocarriers. Using QDs as a delivery approach enhances solubility, lengthens retention time, and reduces the harmful effects of loaded medicines. Several varieties of quantum dots used in drug administration are discussed in this article, along with their chemical and physical characteristics and manufacturing methods. Furthermore, it discusses the role of QDs in biological, medicinal, and theranostic applications.

Ferritin: A Promising Nanoreactor and Nanocarrier for Bionanotechnology

The essence of bionanotechnology lies in the application of nanotechnology/nanomaterials to solve the biological problems. Quantum dots and nanoparticles hold potential biomedical applications, but their inherent problems such as low solubility and associated toxicity due to their interactions at nonspecific target sites is a major concern. The self-assembled, thermostable, ferritin protein nanocages possessing natural iron scavenging ability have emerged as a potential solution to all the above-mentioned problems by acting as nanoreactor and nanocarrier. Ferritins, the cellular iron repositories, are hollow, spherical, symmetric multimeric protein nanocages, which sequester the excess of free Fe(II) and synthesize iron biominerals (Fe₂O₃·H₂O) inside their ∼5-8 nm central cavity. The electrostatics and dynamics of the pore residues not only drives the natural substrate Fe²⁺ inside ferritin nanocages but also uptakes a set of other metals ions/counterions during in vitro synthesis of nanomaterial. The current review aims to report the recent developments/understanding on ferritin structure (self-assembly, surface/pores electrostatics, metal ion binding sites) and chemistry occurring inside these supramolecular protein cages (protein mediated metal ion uptake and mineralization/nanoparticle formation) along with its surface modification to exploit them for various nanobiotechnological applications. Furthermore, a better understanding of ferritin self-assembly would be highly useful for optimizing the incorporation of nanomaterials via the disassembly/reassembly approach. Several studies have reported the successful engineering of these ferritin protein nanocages in order to utilize them as potential nanoreactor for synthesizing/incorporating nanoparticles and as nanocarrier for delivering imaging agents/drugs at cell specific target sites. Therefore, the combination of nanoscience (nanomaterials) and bioscience (ferritin protein) projects several benefits for various applications ranging from electronics to medicine.

Cell-membrane-inspired polymers for constructing biointerfaces with efficient molecular recognition

Fabrication of devices that accurately recognize, detect, and separate target molecules from mixtures is a crucial aspect of biotechnology for applications in medical, pharmaceutical, and food sciences. This technology has also been recently applied in solving environmental and energy-related problems. In molecular recognition, biomolecules are typically complexed with a substrate, and specific molecules from a mixture are recognized, captured, and reacted. To increase sensitivity and efficiency, the activity of the biomolecules used for capture should be maintained, and non-specific reactions on the surface should be prevented. This review summarizes polymeric materials that are used for constructing biointerfaces. Precise molecular recognition occurring at the surface of cell membranes is fundamental to sustaining life; therefore, materials that mimic the structure and properties of this particular surface are emphasized in this article. The requirements for biointerfaces to eliminate nonspecific interactions of biomolecules are described. In particular, the major issue of protein adsorption on biointerfaces is discussed by focusing on the structure of water near the interface from a thermodynamic viewpoint; moreover, the structure of polymer molecules that control the water structure is considered. Methodologies enabling stable formation of these interfaces on material surfaces are also presented.

Fe3 O4 @Au@Cu2-x S Heterostructures Designed for Tri-Modal Therapy: Photo- Magnetic Hyperthermia and 64 Cu Radio-Insertion

Here, the synthesis and proof of exploitation of three-material inorganic heterostructures made of iron oxide-gold-copper sulfide (Fe₃ O₄ @Au@Cu_2-x S) are reported. Starting with Fe₃ O₄ -Au dumbbell heterostructure as seeds, a third Cu_2-x S domain is selectively grown on the Au domain. The as-synthesized trimers are transferred to water by a two-step ligand exchange procedure exploiting thiol-polyethylene glycol to coordinate Au and Cu_2-x S surfaces and polycatechol-polyethylene glycol to bind the Fe₃ O₄ surface. The saline stable trimers possess multi-functional properties: the Fe₃ O₄ domain, of appropriate size and crystallinity, guarantees optimal heating losses in magnetic hyperthermia (MHT) under magnetic field conditions of clinical use. These trimers have indeed record values of specific adsorption rate among the inorganic-heterostructures so far reported. The presence of Au and Cu_2-x S domains ensures a large adsorption which falls in the first near-infrared (NIR) biological window and is here exploited, under laser excitation at 808 nm, to produce photo-thermal heat alone or in combination with MHT obtained from the Fe₃ O₄ domain. Finally, an intercalation protocol with radioactive ⁶⁴ Cu ions is developed on the Cu_2-x S domain, reaching high radiochemical yield and specific activity making the Fe₃ O₄ @Au@Cu_2-x S trimers suitable as carriers for ⁶⁴ Cu in internal radiotherapy (iRT) and traceable by positron emission tomography (PET).

Structural changes in selected human proteins induced by exposure to quantum dots, their biological relevance and possible biomedical applications

Quantum dots (QDs) are semi-conductor luminescent nanocrystals usually of 2-10 nm diameter, attracting the significant attention in biomedical studies since emerged. Due to their unique optical and electronic properties, i.e. wide absorption spectra, narrow tunable emission bands or stable, bright photoluminescence, QDs seem to be ideally suited for multi-colour, simultaneous bioimaging and cellular labeling at the molecular level as new-generation probes. A highly reactive surface of QDs allows for conjugating them to biomolecules, what enables their direct binding to areas of interest inside or outside the cell for biosensing or targeted delivery. Particularly protein-QDs conjugates are current subjects of research, as features of QDs can be combined with protein specific functionalities and therefore used as a complex in variety of biomedical applications. It is known that QDs are able to interact with cells, organelles and macromolecules of the human body after administration. QDs are reported to cause changes at proteins level, including unfolding and three-dimensional structure alterations which might hamper proteins from performing their physiological functions and thereby limit the use of QD-protein conjugates in vivo. Moreover, these changes may trigger unwanted cellular outcomes as the effect of different signaling pathways activation. In this review, characteristics of QDs interactions with certain human proteins are presented and discussed. Besides that, the following manuscript provides an overview on structural changes of specific proteins exposed to QDs and their biological and biomedical relevance.

Non-toxic near-infrared light-emitting diodes

Harnessing cost-efficient printable semiconductor materials as near-infrared (NIR) emitters in light-emitting diodes (LEDs) is extremely attractive for sensing and diagnostics, telecommunications, and biomedical sciences. However, the most efficient NIR LEDs suitable for printable electronics rely on emissive materials containing precious transition metal ions (such as platinum), which have triggered concerns about their poor biocompatibility and sustainability. Here, we review and highlight the latest progress in NIR LEDs based on non-toxic and low-cost functional materials suitable for solution-processing deposition. Different approaches to achieve NIR emission from organic and hybrid materials are discussed, with particular focus on fluorescent and exciplex-forming host-guest systems, thermally activated delayed fluorescent molecules, aggregation-induced emission fluorophores, as well as lead-free perovskites. Alternative strategies leveraging photonic microcavity effects and surface plasmon resonances to enhance the emission of such materials in the NIR are also presented. Finally, an outlook for critical challenges and opportunities of non-toxic NIR LEDs is provided.

Unlocking the power of optical imaging in the second biological window: Structuring near-infrared II materials from organic molecules to nanoparticles

Biomedical imaging techniques play a crucial role in clinical diagnosis, surgical intervention, and prognosis. Fluorescence imaging in the second biological window (second near-infrared [NIR-II]; 1000-1700 nm) has attracted attention recently. NIR-II fluorescence imaging offers unique advantages in terms of reduced photon scattering, deep tissue penetration, high sensitivity, and many others. A host of materials, including small organic molecules, single-walled carbon nanotubes, polymeric and rare-earth-doped nanoparticles, have been explored as NIR-II emitting fluorescent probes. Efficient and viable approaches to design and develop fluorescence probes with tunable photophysical properties without compromising other key features are of paramount importance. Various chemical strategies are explored to increase the quantum yield of these imaging agents without compromising their spatiotemporal resolution, specificity, and tissue penetration capabilities. This review summarizes the strategies implemented to design and synthesize NIR-II emitting nanoparticles and small organic molecule-based fluorescent probes for applications in the biomedical field. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Implantable Materials and Surgical Technologies > Nanoscale Tools and Techniques in Surgery.

Doped-carbon dots: Recent advances in their biosensing, bioimaging and therapy applications

As a fascinating class of fluorescent carbon dots (CDs), doped-CDs are now sparked intense research interest, particularly in the diverse fields of biomedical applications due to their unique advantages, including low toxicity, physicochemical, photostability, excellent biocompatibility, and so on. In this review, we have summarized the most recent developments in the literature regarding the employment of doped-CDs for pharmaceutical and medical applications, which are published over approximately the past five years. Accordingly, we discuss the toxicity and optical properties of these nanomaterials. Beyond the presentation of successful examples of the application of these multifunctional nanoparticles in photothermal therapy, photodynamic therapy, and antibacterial activity, we further highlight their application in the cellular labeling, dual imaging, and in vitro and in vivo bioimaging by use of fluorescent-, photoacoustic-, magnetic-, and computed tomography (CT)-imaging. The potency of doped-CDs was also described in the biosensing of ions, small molecules, and drugs in biological samples or inside the cells. Finally, the advantages, disadvantages, and common limitations of doped-CD technologies are reviewed, along with the future prospects in biomedical research. Therefore, this review provides a concise insight into the current developments and challenges in the field of doped-CDs, especially for biological and biomedical researchers.

Toxicity evaluation of cadmium-containing quantum dots: A review of optimizing physicochemical properties to diminish toxicity

Fluorescent quantum dots (QDs) have received extensive attention because of their excellent optical properties and wide utilization in biological and biomedical areas. Nonetheless, there have been intense concerns on the cytotoxicity assessment of cadmium-containing QDs due to free cadmium ions release and nano-size effects. This paper reviews the representative synthetic strategies for preparation of cadmium-containing QDs and their applications. Then the toxicity assessments of QDs from cell studies to animal models are discussed, which can aid in improving our understanding of the cytotoxicity of QDs, and the toxicity mechanism is proposed. Several critical physicochemical properties of QDs are discussed and suggestions are provided for optimizing QDs design in view of minimal cytotoxicity. Finally, accurate detection techniques and systematic methodologies for the toxicity assessment of QDs are expected to achieve further breakthroughs in the future, especially in-situ, real-time, and rapid quantitative analysis methods.

Discrimination of copper and silver ions based on the label-free quantum dots

A simple and fast method for copper ions (Cu²⁺) and silver ions (Ag⁺) detection was established with cadmium telluride quantum dots (CdTe QDs) as fluorescent probes. In the presence of Cu²⁺ or Ag⁺, the fluorescence intensity of TGA-CdTe QD can be significantly quenched, which fitted a linear relationship between the fluorescence quenching degree (F₀-F)/F₀ and the concentration of metal ions. In this work, the lowest detected concentration for Cu²⁺ and Ag⁺ was 35.0 nM and 25.3 nM, respectively. In addition, the differentiation of Cu²⁺ and Ag⁺ at different concentrations was realized with the principal component analysis (PCA). Furthermore, Cu²⁺ was successfully detected in body fluids. This method provides a good potential for copper ions and silver ions detection with simplicity, rapidity, and excellent selectivity.

Aptamers used for biosensors and targeted therapy

Aptamers are single-stranded nucleic acid sequences that can bind to target molecules with high selectivity and affinity. Most aptamers are screened in vitro by a combinatorial biology technique called systematic evolution of ligands by exponential enrichment (SELEX). Since aptamers were discovered in the 1990s, they have attracted considerable attention and have been widely used in many fields owing to their unique advantages. In this review, we present an overview of the advancements made in aptamers used for biosensors and targeted therapy. For the former, we will discuss multiple aptamer-based biosensors with different principles detected by various signaling methods. For the latter, we will focus on aptamer-based targeted therapy using aptamers as both biotechnological tools for targeted drug delivery and as targeted therapeutic agents. Finally, challenges and new perspectives associated with these two regions were further discussed. We hope that this review will help researchers interested in aptamer-related biosensing and targeted therapy research.

Tunable NIR-II emitting silver chalcogenide quantum dots using thio/selenourea precursors: preparation of an MRI/NIR-II multimodal imaging agent

Aqueous-stable, Cd- and Pb-free colloidal quantum dots with fluorescence properties in the second near-infrared region (NIR-II, 1000-1400) are highly desirable for non-invasive deep-tissue optical imaging and biosensing. The low band-gap semiconductor, silver chalcogenide, offers a non-toxic and stable alternative to existing Pd, As, Hg and Cd-based NIR-II colloidal quantum dots (QDs). We report facile access to NIR-II emission windows with Ag2X (X = S, Se) QDs using easy-to-prepare thio/selenourea precursors and their analogues. The aqueous phase transfer of these QDs with a high conservation of fluorescence quantum yield (retention up to ∼90%) and colloidal stability is demonstrated. A bimodal NIR-II/MRI contrast agent with a tunable fluorescence and high T1 relaxivity of 408 mM-1 s-1 per QD (size ∼ 2.2 nm) and 990 mM-1 s-1 per QD (size ∼ 4.2 nm) has been prepared by grafting 50 and 120 monoaqua Gd(iii) complexes respectively to two differently sized Ag2S QDs. The size of the nanocrystals is crucial for tuning the Gd payload and the relaxivity.

A fluorescent sensor based on oyster mushroom-carbon dots for sensing nitroarenes in aqueous solutions

The synthesis of OM-CDs and their sensing application for NAs.

Novel fluorescent CdTe quantum dot-thymine conjugate-synthesis, properties and possible application

Novel, highly fluorescent cadmium telluride quantum dots conjugated with thymine and stabilized with thioglycolic acid were obtained and characterized. Successful formation of the conjugate was confirmed by elemental analysis, and UV-vis, fluorescence and Fourier transform infrared spectroscopies. Crystal structure and composition of the conjugates were characterized with xray diffraction and x-ray photoelectron spectroscopy. The size of the conjugates was 4-6 nm as demonstrated using atomic force microscopy and high resolution transmission electron microscopy imaging. The plasmon resonance fluorescence band at 540 nm on excitation at 351 nm was observed for these nanoparticles. The intensity of this band increased with the increase in the amount of conjugated thymine with no shift in its position. Based on the fluorescence measurements it was found that the CdTe-thymine conjugate interacted efficiently and selectively not only with adenine, a nucleobase complementary to thymine, but also with adenine-containing modified nucleosides, i.e., 5'-deoxy-5'-(methylthio)adenosine and 2'-O-methyladenosine, the urinary tumor markers which allow monitoring of the disease progression. To the best of our knowledge, as yet, there have been no studies presented in literature on that type of the interaction with CdTe-thymine conjugates. Therefore, the system presented can be considered as a working component of a selective adenine/adenosine biosensor with potential application in cancer diagnosis.

ZnO-Based Nanoplatforms for Labeling and Treatment of Mouse Tumors without Detectable Toxic Side Effects

ZnO quantum dots (QDs) were synthesized with polymer shells, coordinated with Gd(3+) ions and adsorbed doxorubicin (DOX) together to form a new kind of multifunctional ZnO-Gd-DOX nanoplatform. Such pH sensitive nanoplatforms were shown to release DOX to cancer cells in vitro and to mouse tumors in vivo, and reveal better specificity and lower toxicity than free DOX, and even better therapeutic efficacy than an FDA approved commercial DOX-loading drug DOX-Liposome Injection (DOXIL, NDA#050718). The ZnO-Gd-DOX nanoplatforms exhibited strong red fluorescence, which benefited the fluorescent imaging on live mice. Due to the special structure of ZnO-Gd-DOX nanoparticles, such nanoplatforms possessed a high longitudinal relaxivity r1 of 52.5 mM(-1) s(-1) at 0.55 T, which was superior to many other Gd(3+) based nanoparticles. Thus, both fluorescence labeling and magnetic resonance imaging could be applied simultaneously on the tumor bearing mice along with drug delivery. After 36 days of treatment on these mice, ZnO-Gd-DOX nanoparticles greatly inhibited the tumor growth without causing any appreciable abnormality in major organs. The most important merit of ZnO-Gd-DOX was that such a nanoplatform was biodegraded completely and showed no toxic side effects after H&E (hematoxylin and eosin) staining of tumor slices and ICP-AES (inductively coupled plasma atomic emission spectrometry) bioanalyses.

The toxicity of graphene quantum dots

This review provides a comprehensive account on the current research status regarding the toxicity of graphene quantum dots (GQDs) – a new nano material with profound potential in various advanced applications.

Quantum dot as probe for disease diagnosis and monitoring

Semiconductor quantum dots (QD) possess unique optical and electric properties like size-tunable light emission, narrow emission range, high brightness and photostability. Recent research advances have minimized the toxicity of QDs and they are successfully used in in vitro and in vivo imaging. Encapsulation of QDs into polymeric nanoparticles and linking them with targeting ligands enabled the detection of tumors and cancer cells in vivo. QD-antibody conjugates were successfully used in monitoring and diagnosis of HIV and myocardial infarction. Application of near infrared (NIR) QDs was found to minimize the absorption and scattering of light by native tissues thus rendering them suitable in deep tissue analysis. Aggregation and endosomal sequestration of QDs pose major challenges for the effective delivery of QDs to the cell cytosol. Toxicity minimization and effective delivery strategies may further increase their suitability for utilization in disease diagnosis. New synthesis of QDs may provide new types of bioconjugates of QDs to biomolecules, which leads to a variety of applications to many challenged research areas. QDs with narrow emission wavelength ranges are very suitable for monitoring multiple cellular targets simultaneously, and still remain the best known probes for imaging as an alternative to traditional fluorophores in disease diagnosis.

Facile Construction of Near Infrared Fluorescence Nanoprobe with Amphiphilic Protein-Polymer Bioconjugate for Targeted Cell Imaging

A simple, straightforward, and reproducible strategy for the construction of a near-infrared (NIR) fluorescence nanoprobe was developed by coating CuInS2/ZnS quantum dots (CIS/ZnS QDs) with a novel amphiphilic bioconjugate. The amphiphilic bioconjugate with a tailor-designed structure of bovine serum albumin (BSA) as the hydrophilic segment and poly(ε-caprolactone) (PCL) as the hydrophobic part was fabricated by chemical coupling the hydrophobic polymer chain to BSA via the maleimide-sulfhydryl reaction. By incorporating CIS/ZnS QDs into the hydrophobic cores of the self-assembly of BSA-PCL conjugate, the constructed NIR fluorescence nanoprobe exhibited excellent fluorescent properties over a wide pH range (pH 3-10) and a good colloidal stability in PBS buffer (pH = 7.4) with or without 10% fetal bovine serum. The presence of the outer BSA shell effectively reduced the nonspecific cellular binding and imparted high biocompatibility and low-toxicity to the probe. Moreover, the NIR fluorescence nanoprobe could be functionalized by conjugating cyclic Arg-Gly-Asp (cRGD) peptide, and the decorated nanoprobe was shown to be highly selective for targeted integrin αvβ3-overexpressed tumor cell imaging. The feasibility of the constructed NIR fluorescence probe in vivo application was further investigated and the results demonstrated its great potential for in vivo imaging. This developed protocol for phase transfer of the CIS/ZnS QDs was universal and applicable to other nanoparticles stabilized with hydrophobic ligands.

Engineering the cell-semiconductor interface: a materials modification approach using II-VI and III-V semiconductor materials

Developing functional biomedical devices based on semiconductor materials requires an understanding of interactions taking place at the material-biosystem interface. Cell behavior is dependent on the local physicochemical environment. While standard routes of material preparation involve chemical functionalization of the active surface, this review emphasizes both biocompatibility of unmodified surfaces as well as use of topographic features in manipulating cell-material interactions. Initially, the review discusses experiments involving unmodified II-VI and III-V semiconductors - a starting point for assessing cytotoxicity and biocompatibility - followed by specific surface modification, including the generation of submicron roughness or the potential effect of quantum dot structures. Finally, the discussion turns to more recent work in coupling topography and specific chemistry, enhancing the tunability of the cell-semiconductor interface. With this broadened materials approach, researchers' ability to tune the interactions between semiconductors and biological environments continues to improve, reaching new heights in device function.

Direct synthesis of CdS nanodots embedded in bovine serum albumin without external sulfur source for cell imaging

CdS nanodots with good water solubility and low cell cytotoxicity were synthesized using BSA as template without external sulfur.

A study on effects of naphthalimide derivative-capped quantum dots on the cellular internalization, proliferation, and apoptosis ability

Quantum dots (QDs) have shown great potential in monitoring and imaging cancer cells because of their unique photochemical and photophysical properties. However, it is little-known whether QDs affect the cellular internalization, proliferation and apoptosis. Here a new class of multifunctional QDs capped with ligands that possess l-Lys or l-Arg and naphthalimide (NI), linked by carboxyl groups (l-Lys-NI@QDs and l-Arg-NI@QDs, respectively), have been synthesized. We found that these QDs are of controllable sizes, in the range of 4 to 5 nm and have strong optical emission properties. The cellular uptake of NI derivative-capped QDs was monitored by flow cytometry and confocal microscopy. The results of in vitro cytotoxicity revealed that NI derivative-capped QDs, with better cell selectivity, could inhibit the growth of multiple cancer cells more potently than amonafide. They effectively inhibited the proliferation of cells due to apoptosis, which was confirmed by Hoechst 33342, annexin V-FITC and JC-1 staining and mitochondrial membrane potential (MMP) experiments. The most potent NI derivative-capped QDs, l-Arg-NI@CdSe/ZnS, were verified to efficiently induce apoptosis via a reactive oxygen species (ROS) mediating mitochondrial dysfunction, and were more effective in promoting programmed cell death in HepG2 cells in a preliminary mechanistic study.

Highly colloidally stable hyperbranched polyglycerol grafted red fluorescent silicon nanoparticle as bioimaging probe

Here we report a surface modification approach for fluorescent silicon nanoparticle that transforms hydrophobic nanoparticle into water-soluble nanoparticle of high colloidal stability. The approach involves ring-opening polymerization of glycidol at the hydroxyl-terminated nanoparticle surface that results in a hyperbranched polyglycerol grafted silicon nanoparticle (Si-HPG). The resultant Si-HPG has 25 nm hydrodynamic diameter, low surface charge, and broad emission in the range of 450-700 nm with a fluorescence quantum yield of 6-9%. The Si-HPG has been transformed into cyclic RGD peptide functionalized nanoprobe using the conventional bioconjugation chemistry and used for specific targeting to αvβ3 integrin overexpressed cervical cancer cells and glioblastoma cells. Result shows that a silicon nanoparticle-based red fluorescent nanoprobe can be developed for in vitro/in vivo bioimaging applications.

Highly bright water-soluble silica coated quantum dots with excellent stability

A facile Stöber method for the synthesis of isolated silica coated QDs with high PL efficiencies, tunable small size and excellent stability leads to the practical bioapplication as robust biomarkers.