Quantum dots: synthesis, bioapplications, and toxicity

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.

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.

Shedding Light on Luminescent Janus Nanoparticles: From Synthesis to Photoluminescence and Applications

Luminescent Janus nanoparticles refer to a special category of Janus-based nanomaterials that not only exhibit dual-asymmetric surface nature but also attractive optical properties. The introduction of luminescence has endowed conventional Janus nanoparticles with many alluring light-responsive functionalities and broadens their applications in imaging, sensing, nanomotors, photo-based therapy, etc. The past few decades have witnessed significant achievements in this field. This review first summarizes well-established strategies to design and prepare luminescent Janus nanoparticles and then discusses optical properties of luminescent Janus nanoparticles based on downconversion and upconversion photoluminescence mechanisms. Various emerging applications of luminescent Janus nanoparticles are also introduced. Finally, opportunities and future challenges are highlighted with respect to the development of next-generation luminescent Janus nanoparticles with diverse applications.

Quantum Dots for Cancer-Related miRNA Monitoring

Quantum dots (QDs) possess exceptional optoelectronic properties that enable their use in the most diverse applications, namely, in the medical field. The prevalence of cancer has increased and has been considered the major cause of death worldwide. Thus, there has been a great demand for new methodologies for diagnosing and monitoring cancer in cells to provide an earlier prognosis of the disease and contribute to the effectiveness of treatment. Several molecules in the human body can be considered relevant as cancer markers. Studies published over recent years have revealed that micro ribonucleic acids (miRNAs) play a crucial role in this pathology, since they are responsible for some physiological processes of the cell cycle and, most important, they are overexpressed in cancer cells. Thus, the analytical sensing of miRNA has gained importance to provide monitoring during cancer treatment, allowing the evaluation of the disease's evolution. Recent methodologies based on nanochemistry use fluorescent quantum dots for sensing of the miRNA. Combining the unique characteristics of QDs, namely, their fluorescence capacity, and the fact that miRNA presents an aberrant expression in cancer cells, the researchers created diverse strategies for miRNA monitoring. This review aims to present an overview of the recent use of QDs as biosensors in miRNA detection, also highlighting some tutorial descriptions of the synthesis methods of QDs, possible surface modification, and functionalization approaches.

Synthesis, properties and catalysis of quantum dots in C–C and C-heteroatom bond formations

Luminescent quantum dots (QDs) represent a new form of carbon nanomaterials which have gained widespread attention in recent years, especially in the area of chemical sensing, bioimaging, nanomedicine, solar cells, light-emitting diode (LED), and electrocatalysis. Their extremely small size renders some unusual properties such as quantum confinement effects, good surface binding properties, high surface‐to‐volume ratios, broad and intense absorption spectra in the visible region, optical and electronic properties different from those of bulk materials. Apart from, during the past few years, QDs offer new and versatile ways to serve as photocatalysts in organic synthesis. Quantum dots (QD) have band gaps that could be nicely controlled by a number of factors in a complicated way, mentioned in the article. Processing, structure, properties and applications are also reviewed for semiconducting quantum dots. Overall, this review aims to summarize the recent innovative applications of QD or its modified nanohybrid as efficient, robust, photoassisted redox catalysts in C–C and C-heteroatom bond forming reactions. The recent structural modifications of QD or its core structure in the development of new synthetic methodologies are also highlighted. Following a primer on the structure, properties, and bio-functionalization of QDs, herein selected examples of QD as a recoverable sustainable nanocatalyst in various green media are embodied for future reference.

Improving photocatalytic activity of the ZnS QDs via lanthanide doping and photosensitizing with GO and g-C3N4 for degradation of an azo dye and bisphenol-A under visible light irradiation

In this research, insertion of Gd ions (2 wt%) into the crystalline lattice of the ZnS QDs enhanced the photocatalytic activity of the QDs. In addition, the influence of graphene oxide (GO) and graphitic carbon nitride (g-C₃N₄) was assessed on the photocatalytic activity of the ZnS QDs through degradation of acid red 14 (AR14) and bisphenol-A (BA) under visible light. Higher photocatalytic degradation efficiency (97.1% for AR14 and 67.4% for BA within 180 min) and higher total organic carbon (TOC) removal (67.1% for AR14 and 59.2% for BA within 5 h) was achieved in the presence of ZnS QDs/g-C₃N₄ compared with ZnS QDs/GO nanocomposite. Finally, the Gd-doped ZnS QDs were hybridized with g-C₃N₄ as optimal support to fabricate a potent visible-light-driven photocatalyst for the decomposition of organic contaminants. The maximum photocatalytic degradation of 99.1% and 80.5% were achieved for AR14 and BA, respectively, in the presence of Gd-doped ZnS QDs/g-C₃N₄ nanocomposite. The photosensitization mechanism was suggested for the improved photocatalytic activity of the ZnS QDs/GO, ZnS QDs/g-C₃N₄, and Gd-doped ZnS QDs/g-C₃N₄ nanocomposites under visible light.

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.

Advances in quantum dots as diagnostic tools

Quantum dots (QDs) are crystalline inorganic semiconductor nanoparticles a few nanometers in size that possess unique optical electronic properties vs those of larger materials. For example, QDs usually exhibit a strong and long-lived photoluminescence emission, a feature dependent on size, shape and composition. These special optoelectronic properties make them a promising alternative to conventional luminescent dyes as optical labels in biomedical applications including biomarker quantification, biomolecule targeting and molecular imaging. A key parameter for use of QDs is to functionalize their surface with suitable (bio)molecules to provide stability in aqueous solutions and efficient and selective tagging biomolecules of interest. Researchers have successfully developed biocompatible QDs and have linked them to various biomolecule recognition elements, i.e., antibodies, proteins, DNA, etc. In this chapter, QD synthesis and characterization strategies are reviewed as well as the development of nanoplatforms for luminescent biosensing and imaging-guided targeting. Relevant biomedical applications are highlighted with a particular focus on recent progress in ultrasensitive detection of clinical biomarkers. Finally, key future research goals to functionalize QDs as diagnostic tools are explored.

Functionalized Nanostructured Bioactive Carriers: Nanoliposomes, Quantum Dots, Tocosome and Theranostic Approach

BACKGROUND

Lipidic nanocarriers have great potential for the encapsulation and delivery of numerous bioactive compounds. They have demonstrated significant benefits over traditional disease management and conventional therapy. The benefits associated with the particular properties of lipidic nanocarriers include site-specific drug deposition, improved pharmacokinetics and pharmacodynamics, enhanced internalization and intracellular transport, biodegradability, and decreased biodistribution. These properties result in the alleviation of the harmful consequences of conventional treatment protocols. Scope and approach: The administration of various bioactive molecules has been extensively investigated using nanostructured lipid carriers. In this article, theranostic applications of novel formulations of lipidic nanocarriers combined or complexed with quantum dots, certain polymers such as chitosan, and metallic nanoparticles (particularly gold) are reviewed. These formulations have demonstrated better controlled release features, improved drug loading capability, as well as a lower burst release rate. As a recent innovation in the field of drug delivery, tocosomes and their unique advantages are also explained in the final section of this entry.

KEY FINDINGS AND CONCLUSIONS

Theranostic medicine requires nanocarriers with improved target-specific accumulation and bio-distribution. Towards this end, lipid-based nanocarrier systems and tocosomes combined with unique properties of quantum dots, biocompatible polymers, and metallic nanoparticles seem to be ideal candidates to be considered for safe and efficient drug delivery.

Role of Nanoparticles in Environmental Remediation: An Insight into Heavy Metal Pollution from Dentistry

Environmental damage is without a doubt one of the most serious issues confronting society today. As dental professionals, we must recognize that some of the procedures and techniques we have been using may pose environmental risks. The usage and discharge of heavy metals from dental set-ups pollute the environment and pose a serious threat to the ecosystem. Due to the exclusive properties of nanosized particles, nanotechnology is a booming field that is being extensively studied for the remediation of pollutants. Given that the nanoparticles have a high surface area to volume ratio and significantly greater reactivity, they have been greatly considered for environmental remediation. This review aims at identifying the heavy metal sources and their environmental impact in dentistry and provides insights into the usage of nanoparticles in environmental remediation. Although the literature on various functions of inorganic nanoparticles in environmental remediation was reviewed, the research is still confined to laboratory set-ups and there is a need for more studies on the usage of nanoparticles in environmental remediation.

Recent Advances in Colloidal Quantum Dots or Perovskite Quantum Dots as a Luminescent Downshifting Layer Embedded on Solar Cells

The solar cell has a poor spectral response in the UV region, which affects its power conversion efficiency (PCE). The utilization of a luminescent downshifting (LDS) layer has been suggested to improve the spectral response of the photovoltaics in the short wavelength region through photoluminescence (PL) conversion and antireflection effects, which then enhance the PCE of the solar cell. Recently, colloidal quantum dots (CQDs) or perovskite quantum dots (PQDs) have been gaining prime importance as an LDS material due to their eminent optical characteristics, such as their wide absorption band, adjustable visible emission, short PL lifetime, and near-unity quantum yields. However, the instability of QDs that occurs under certain air, heat, and moisture conditions limits its commercialization. Thus, in this review, we will focus on the physical and optical characteristics of QDs. Further, we will discuss different synthesis approaches and the stability issues of QDs. Different approaches to improve the stability of QDs will be discussed in detail alongside the recent breakthroughs in QD-based solar cells for various applications and their current challenges. We expect that this review will provide an effective gateway for researchers to fabricate LDS-layer-based solar cells.

Assessing the Environmental Effects Related to Quantum Dot Structure, Function, Synthesis and Exposure

Quantum dots (QDs) are engineered semiconductor nanocrystals with unique fluorescent, quantum confinement, and quantum yield properties, making them valuable in a range of commercial and consumer imaging, display, and lighting technologies. Production and usage of QDs are increasing, which increases the probability of these nanoparticles entering the environment at various phases of their life cycle. This review discusses the major types and applications of QDs, their potential environmental exposures, fates, and adverse effects on organisms. For most applications, release to the environment is mainly expected to occur during QD synthesis and end-product manufacturing since encapsulation of QDs in these devices prevents release during normal use or landfilling. In natural waters, the fate of QDs is controlled by water chemistry, light intensity, and the physicochemical properties of QDs. Research on the adverse effects of QDs primarily focuses on sublethal endpoints rather than acute toxicity, and the differences in toxicity between pristine and weathered nanoparticles are highlighted. A proposed oxidative stress adverse outcome pathway framework demonstrates the similarities among metallic and carbon-based QDs that induce reactive oxygen species formation leading to DNA damage, reduced growth, and impaired reproduction in several organisms. To accurately evaluate environmental risk, this review identifies critical data gaps in QD exposure and ecological effects, and provides recommendations for future research. Future QD regulation should emphasize exposure and sublethal effects of metal ions released as the nanoparticles weather under environmental conditions. To date, human exposure to QDs from the environment and resulting adverse effects has not been reported.

Optical and Physicochemical Characterizations of a Cellulosic/CdSe-QDs@S-DAB5 Film

CdSe quantum dots nanoparticles were coated with the thiolated (DiAminoButane based dendrimer) DAB dendrimer of fifth generation (S-DAB₅) and embedded in a highly hydrophilic regenerated cellulose (RC) film by simple dip-coating method (immersion in QD-dendrimer aqueous solution) as a way to get a flexible nano-engineered film (RC-4/CdSe-QDs@S-DAB₅) with high transparency and photoluminescence properties for different applications. Optical changes in the RC film associated with QDs inclusion were determined by spectroscopic ellipsometry (SE) measurements, which provide information on changes caused in the refraction index and the extinction coefficients of the film, as well as by light transmittance/reflectance curves and photoluminescence (PL) spectra. Impedance spectroscopy (IS) and other typical physicochemical techniques for material characterization (TEM, SEM and XPS) have also been used in order to have more complete information on film characteristics. A comparison of RC-4/CdSe-QDs@S-DAB₅ film optical characteristics with those exhibited by other RC-modified films depending on the type of dendrimer was also carried out.

Microemulsion Based Nanostructures for Drug Delivery

Most of the active pharmaceutical compounds are often prone to display low bioavailability and biological degradation represents an important drawback. Due to the above, the development of a drug delivery system (DDS) that enables the introduction of a pharmaceutical compound through the body to achieve a therapeutic effect in a controlled manner is an expanding application. Henceforth, new strategies have been developed to control several parameters considered essential for enhancing delivery of drugs. Nanostructure synthesis by microemulsions (ME) consist of enclosing a substance within a wall material at the nanoscale level, allowing to control the size and surface area of the resulting particle. This nanotechnology has shown the importance on targeted drug delivery to improve their stability by protecting a bioactive compound from an adverse environment, enhanced bioavailability as well as controlled release. Thus, a lower dose administration could be achieved by minimizing systemic side effects and decreasing toxicity. This review will focus on describing the different biocompatible nanostructures synthesized by ME as controlled DDS for therapeutic purposes.

A review on I–III–VI ternary quantum dots for fluorescence detection of heavy metals ions in water: optical properties, synthesis and application

Ternary I–III–VI quantum dots used in the fluorescence detection of heavy metals ions in water.

The Application of Nanoparticles in Diagnosis and Treatment of Kidney Diseases

Nanomedicine is currently showing great promise for new methods of diagnosing and treating many diseases, particularly in kidney disease and transplantation. The unique properties of nanoparticles arise from the diversity of size effects, used to design targeted nanoparticles for specific cells or tissues, taking renal clearance and tubular secretion mechanisms into account. The design of surface particles on nanoparticles offers a wide range of possibilities, among which antibodies play an important role. Nanoparticles find applications in encapsulated drug delivery systems containing immunosuppressants and other drugs, in imaging, gene therapies and many other branches of medicine. They have the potential to revolutionize kidney transplantation by reducing and preventing ischemia-reperfusion injury, more efficiently delivering drugs to the graft site while avoiding systemic effects, accurately localizing and visualising the diseased site and enabling continuous monitoring of graft function. So far, there are known nanoparticles with no toxic effects on human tissue, although further studies are still needed to confirm their safety.

Increased selenium concentration in the synthesis of CdSe magic-sized quantum dots affects how the brain responds to oxidative stress

CdSe magic-sized quantum dots (MSQDs) have been widely used as fluorescent probes in biological systems due to their excellent optical properties with a broader fluorescence spectrum and stable luminescence in biological media. However, they can be cytotoxic and alter the redox balance depending on the amounts of Cd²⁺ adsorbed on their surface. Thus, the present study aimed to evaluate whether increases in selenium concentration in the synthesis of CdSe-MSQDs decrease the oxidative stress caused by Cd²⁺ -based quantum dots. CdSe-MSQDs synthesized with different concentrations of selenium were investigated against oxidative stress in the brain of chicken embryos by examining total antioxidant capacity, lipid peroxidation, thiol, and glutathione contents, as well as the activities of glutathione peroxidase, superoxide dismutase (SOD), catalase (CAT), and glutathione reductase. In addition, the vascularization of the chorioallantoic membrane (CAM) analysis was performed. Higher selenium concentrations alter the surface defect levels (decrease free Cd²⁺ ) and controlled the oxidative effects of CdSe-MSQDs by reducing the lipid peroxidation, restoring the glutathione defense system and the antioxidant enzymes SOD and CAT, and maintaining the vascular density of the CAM. The current findings reinforce the study of the effects of the presence of Cd²⁺ ions on the surface of quantum dots, changing toxicity, and aiming interesting strategies of nanomaterials in biological systems.

Application of green synthesized WO3-poly glutamic acid nanobiocomposite for early stage biosensing of breast cancer using electrochemical approach

Biopolymer films have drawn growing demand for their application in the point of care domain owing to their biocompatibility, eco-friendly, and eligibility for in vivo analyses. However, their poor conductivity restricts their sensitivity in diagnostics. For high-quality electrochemical biosensor monitoring, two vital factors to be greatly paid attention are the effective merge of amplification modifiers with transducing surface and the superior linking across the recognition interface. Here, we introduce an enzyme-free electrochemical biosensor based on electrosynthesized biocompatible WO3/poly glutamic acid nano-biocomposites to address the hardships specific to the analysis of circulating proteins clinical samples. In addition to its green synthesis route, the poor tendency of both components of the prepared nano-biocomposite to amine groups makes it excellent working in untreated biological samples with high contents of proteins. Several electrochemical and morphological investigations (SEM, EDX, and dot mapping) were fulfilled to gain a reliable and trustful standpoint of the framework. By using this nanobiosensor, the concentration of HER-2 was detectable as low as 1 fg mL-1 with a wide linear response between 1 ng mL-1 and 1 fg mL-1. Meanwhile, the protocol depicted ideal specificity, stability, and reproducibility for the detection of HER-2 protein in untreated serum samples of breast cancer patients.

Microfluidic synthesis of optically responsive materials for nano- and biophotonics

Recently, nanomaterials demonstrating optical response under illumination, the so-called optically responsive nanoparticles (NPs), have found their broad application as optical switchers, gas adsorbents, data storage devices, and optical and biological sensors. Unique optical properties of such nanomaterials are strongly related to their chemical composition, geometrical parameters and morphology. Microfluidic approaches for NPs' synthesis allow overcoming the known critical stages in conventional synthesis of NPs due to a high rate of heat/mass transfer and precise regulation of synthesis conditions, which results in reproducible synthesis outcomes with the desired physico-chemical properties. Here, we review the recent advances in microfluidic approach for synthesis of optically responsive nanomaterials (plasmonic, photoluminescent, shape-changeable NPs), highlighting the general background of microfluidics, common considerations in the design of microfluidic chips (MFCs), and theoretical models of the NPs' formation mechanisms. Comparative analysis of microfluidic synthesis with conventional synthesis methods is provided further, along with the recent applications of optically responsive NPs in nano- and biophotonics.

Quantum dots synthetization and future prospect applications

Quantum dots (QDs) are nanocrystals of a semiconductor material that exist in a size regime less than 10 nm. QDs have become promising nanoparticles for a wide variety of different applications. However, the major drawback of QDs is their potential toxicity. This review reports on some recent methods for the synthesis of QDs and explores their properties, structures, applications, and toxicity. QDs are extraordinary because their minute size produces a physically confined electron cloud, an effect known as the quantum confinement. Certainly, because of their special properties as they had a great unique optical, electronic, and chemical properties that were not observe in other materials. These unique properties of the QD are an attractive material for a variety of scientific and commercial applications, most of them recently been realized, such as biosensors, bioimaging, photodetectors, displays, solar cells, wastewater treatment, and quantum computers. Finally, but not the end, an interesting potential QD application in future perspectives will expect as light-emitting diode products, biomedical applications, and Li-Fi.

Carbon nanodot-based electrogenerated chemiluminescence biosensor for miRNA-21 detection

A simple carbon nanodot–based electrogenerated chemiluminescence biosensor is described for sensitive and selective detection of microRNA-21 (miRNA-21), a biomarker of several pathologies including cardiovascular diseases (CVDs). The photoluminescent carbon nanodots (CNDs) were obtained using a new synthesis method, simply by treating tiger nut milk in a microwave reactor. The synthesis is environmentally friendly, simple, and efficient. The optical properties and morphological characteristics of the CNDs were exhaustively investigated, confirming that they have oxygen and nitrogen functional groups on their surfaces and exhibit excitation-dependent fluorescence emission, as well as photostability. They act as co-reactant agents in the anodic electrochemiluminescence (ECL) of [Ru(bpy)₃]²⁺, producing different signals for the probe (single-stranded DNA) and the hybridized target (double-stranded DNA). These results paved the way for the development of a sensitive ECL biosensor for the detection of miRNA-21. This was developed by immobilization of a thiolated oligonucleotide, fully complementary to the miRNA-21 sequence, on the disposable gold electrode. The target miRNA-21 was hybridized with the probe on the electrode surface, and the hybridization was detected by the enhancement of the [Ru(bpy)₃]²⁺/DNA ECL signal using CNDs. The biosensor shows a linear response to miRNA-21 concentration up to 100.0 pM with a detection limit of 0.721 fM. The method does not require complex labeling steps, and has a rapid response. It was successfully used to detect miRNA-21 directly in serum samples from heart failure patients without previous RNA extraction neither amplification process.

Modular fluorescent nanoparticle DNA probes for detection of peptides and proteins

Fluorescently labeled antibody and aptamer probes are used in biological studies to characterize binding interactions, measure concentrations of analytes, and sort cells. Fluorescent nanoparticle labels offer an excellent alternative to standard fluorescent labeling strategies due to their enhanced brightness, stability and multivalency; however, challenges in functionalization and characterization have impeded their use. This work introduces a straightforward approach for preparation of fluorescent nanoparticle probes using commercially available reagents and common laboratory equipment. Fluorescent polystyrene nanoparticles, Thermo Fisher Scientific FluoSpheres, were used in these proof-of-principle studies. Particle passivation was achieved by covalent attachment of amine-PEG-azide to carboxylated particles, neutralizing the surface charge from - 43 to - 15 mV. A conjugation-annealing handle and DNA aptamer probe were attached to the azide-PEG nanoparticle surface either through reaction of pre-annealed handle and probe or through a stepwise reaction of the nanoparticles with the handle followed by aptamer annealing. Nanoparticles functionalized with DNA aptamers targeting histidine tags and VEGF protein had high affinity (EC50s ranging from 3 to 12 nM) and specificity, and were more stable than conventional labels. This protocol for preparation of nanoparticle probes relies solely on commercially available reagents and common equipment, breaking down the barriers to use nanoparticles in biological experiments.

Synthesis of highly fluorescent and water soluble graphene quantum dots for detection of heavy metal ions in aqueous media

Fluorescent graphene quantum dots (GQDs) are nanomaterials which possess unique properties that show great potential in different applications. In this work, GQDs were synthesized using graphene oxide (GO) as precursor via thermal treatment at high temperature. The obtained GQDs were highly fluorescent and were suitable for the determination of heavy metal ions. X-ray diffraction, FTIR spectroscopy, and UV visible spectroscopy confirm the formation of GQDs. TEM images show that formed GQDs have size ranging from 2 to 10 nm. Emission profile of aqueous GQDs was taken by exciting GQDs at different wavelength. The intensity of GQDs remains the same for 4-5 months. Furthermore, as prepared, GQDs were used for selective recognition of Fe³⁺, Pb⁺², and Cr³⁺ from the bunch of different metal ions in aqueous media. Lower limit of detection obtained for Fe³⁺, Cr³⁺ and Pb²⁺ using GQDs were 50, 100 and 100 nM, respectively, which indicates that the GQDs can be utilized as a promising material for sensing of the heavy metal ions. Graphical abstract.

Pivotal Role of Quantum Dots in the Advancement of Healthcare Research

The quantum dot is a kind of nanoparticle whose dimension is smaller than the size of a typical nanoparticle ranging from tens of nanometers to a few hundredths of nanometers. The quantum mechanical behavior associated with the quantum dot displays different optical and electronic properties, enabling the quantum dot to find potential applications in a multitude of areas such as solar cells, light-emitting diodes, lasers, and biomedical applications. The objective of this investigation is to explore its fundamentals, synthesis, and applications, especially in the healthcare domain. We have discussed the quantum dot synthesis techniques using chemical methods, namely, wet-chemical methods and vapor-phase methods and plasma processing methods, namely, an ion sputtering method and plasma-enhanced chemical vapor deposition method. We have thoroughly investigated the application of quantum dots in imaging, diagnostics, and gene therapy areas. A significant outcome of this review is to propose quantum dots as a new modality in the treatment of cancer and gene therapeutics in the healthcare domain and the potentials of artificial intelligence to improve their performance via the applications of neural networks.

The Evolution of Single-Cell Analysis and Utility in Drug Development

This review provides a brief history of the advances of cellular analysis tools focusing on instrumentation, detection probes, and data analysis tools. The interplay of technological advancement and a deeper understanding of cellular biology are emphasized. The relevance of this topic to drug development is that the evaluation of cellular biomarkers has become a critical component of the development strategy for novel immune therapies, cell therapies, gene therapies, antiviral therapies, and vaccines. Moreover, recent technological advances in single-cell analysis are providing more robust cellular measurements and thus accelerating the advancement of novel therapies.

Graphical abstract

Recent applications of quantum dots in optical and electrochemical aptasensing detection of Lysozyme

Lysozyme (Lyz) is a naturally occurring enzyme that operates against Gram-positive bacteria and leads to cell death. This antimicrobial enzyme forms the part of the innate defense system of nearly all animals and exists in their somatic discharges such as milk, tears, saliva and urine. Increased Lyz level in serum is an important indication of several severe diseases and so, precise diagnosis of Lyz is an urgent need in biosensing assays. Up to know, various traditional and modern techniques have been introduced for Lyz determination. Although the traditional methods suffer from some significant limitations such as time-consuming, arduous, biochemical screening, bacterial colony isolation, selective enrichment and requiring sophisticated instrumentation or isotope labeling, some new modern approaches like aptamer-based biosensors (aptasensors) and quantum dot (QD) nanomaterials are the main goal in Lyz detection. Electrochemical and optical sensors have been highlighted because of their adaptability and capability to decrease the drawbacks of common methods. Using an aptamer-based biosensor, sensor selectivity is enhanced due to the specific recognition of the analyte. Thereby, in this review article, the recent advances and achievements in electrochemical and optical aptasensing detection of Lyz based on different QD nanomaterials and detection methods have been discussed in detail.

Antimicrobial Properties of Food Nanopackaging: A New Focus on Foodborne Pathogens

Food products contaminated by foodborne pathogens (bacteria, parasites, and viruses) cause foodborne diseases. Today, great efforts are being allocated to the development of novel and effective agents against food pathogenic microorganisms. These efforts even might have a possible future effect in coronavirus disease 2019 (COVID-19) pandemic. Nanotechnology introduces a novel food packaging technology that creates and uses nanomaterials with novel physiochemical and antimicrobial properties. It could utilize preservatives and antimicrobials to extend the food shelf life within the package. Utilizing the antimicrobial nanomaterials into food packaging compounds typically involves incorporation of antimicrobial inorganic nanoparticles such as metals [Silver (Ag), Copper (Cu), Gold (Au)], and metal oxides [Titanium dioxide (TiO2), Silicon oxide (SiO2), Zinc oxide (ZnO)]. Alternatively, intelligent food packaging has been explored for recognition of spoilage and pathogenic microorganisms. This review paper focused on antimicrobial aspects of nanopackaging and presented an overview of antibacterial properties of inorganic nanoparticles. This article also provides information on food safety during COVID-19 pandemic.

Leftover Kiwi Fruit Peel-Derived Carbon Dots as a Highly Selective Fluorescent Sensor for Detection of Ferric Ion

Recently, the use of natural products for the synthesis of carbon dots (CDs) has received much attention. Herein, leftover kiwi (Actinidia Deliciosa) fruit peels were successfully turned into beneficial fluorescent carbon dots (KN-CDs) via the hydrothermal-carbonization route. KN-CDs 1 and KN-CDs 2 were prepared without and with ammonium hydroxide, respectively. KN-CDs 1 and KN-CDs 2 were systematically characterized by various analytical techniques. Synthesized KN-CDs showed spherical-shaped morphology with narrow size distribution and excellent optical properties with excitation-independent behaviors. The quantum yields of KN-CDs 1 and KN-CDs 2 were calculated as 14 and 19%, respectively. Additionally, the KN-CDs possess excellent prolonging and photostability. Because of the excellent optical properties of KN-CDs, they were utilized as fluorescent sensors. The strong fluorescence of the KN-CDs was selectively quenched by Fe3+ ion, and quenching behavior showed a linear correlation with the concentrations of Fe3+ ion. KN-CDs 1 and KN-CDs 2 showed the detection of Fe3+ ions within the concentration range of 5–25 µM with the detection limit of 0.95 and 0.85 µM, respectively. Based on the turn-off sensing by the detection of Fe3+ ions, KN-CDs would be a promising candidate as a selective and sensitive fluorescent sensor.

Molecularly imprinted polymers in toxicology: a literature survey for the last 5 years

The science of toxicology dates back almost to the beginning of human history. Toxic chemicals, which are encountered in different forms, are always among the chemicals that should be investigated in criminal field, environmental application, pharmaceutic, and even industry, where many researches have been carried out studies for years. Almost all of not only drugs but also industrial dyes have toxic side and direct effects. Environmental micropollutants accumulate in the tissues of all living things, especially plants, and show short- or long-term toxic symptoms. Chemicals in forensic science can be known by detecting the effect they cause to the body with the similar mechanism. It is clear that the best tracking tool among analysis methods is molecularly printed polymer-based analytical setups. Different polymeric combinations of molecularly imprinted polymers allow further study on detection or extraction using chromatographic and spectroscopic instruments. In particular, methods used in forensic medicine can detect trace amounts of poison or biological residues on the scene. Molecularly imprinted polymers are still in their infancy and have many variables that need to be developed. In this review, we summarized how molecular imprinted polymers and toxicology intersect and what has been done about molecular imprinted polymers in toxicology by looking at the studies conducted in the last 5 years.

Use of nanotechnology in combating coronavirus

Recent COVID-19 pandemic situation caused due to the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) affected global health as well as economics. There is global attention on prevention, diagnosis as well as treatment of COVID-19 infection which would help in easing the current situation. The use of nanotechnology and nanomedicine has been considered to be promising due to its excellent potential in managing various medical issues such as viruses which is a major threat. Nanoparticles have shown great potential in various biomedical applications and can prove to be of great use in antiviral therapy, especially over other conventional antiviral agents. This review focusses on the pathophysiology of SARS-CoV-2 and the progression of the COVID-19 disease followed by currently available treatments for the same. Use of nanotechnology has been elaborated by exploiting various nanoparticles like metal and metal oxide nanoparticles, carbon-based nanoparticles, quantum dots, polymeric nanoparticles as well as lipid-based nanoparticles along with its mechanism of action against viruses which can prove to be beneficial in COVID-19 therapeutics. However, it needs to be considered that use of these nanotechnology-based approaches in COVID-19 therapeutics only aids the human immunity in fighting the infection. The main function is performed by the immune system in combatting any infection.

Microfluidic formulation of nanoparticles for biomedical applications

Nanomedicine has made significant advances in clinical applications since the late-20th century, in part due to its distinct advantages in biocompatibility, potency, and novel therapeutic applications. Many nanoparticle (NP) therapies have been approved for clinical use, including as imaging agents or as platforms for drug delivery and gene therapy. However, there are remaining challenges that hinder translation, such as non-scalable production methods and the inefficiency of current NP formulations in delivering their cargo to their target. To address challenges with existing formulation methods that have batch-to-batch variability and produce particles with high dispersity, microfluidics-devices that manipulate fluids on a micrometer scale-have demonstrated enormous potential to generate reproducible NP formulations for therapeutic, diagnostic, and preventative applications. Microfluidic-generated NP formulations have been shown to have enhanced properties for biomedical applications by formulating NPs with more controlled physical properties than is possible with bulk techniques-such as size, size distribution, and loading efficiency. In this review, we highlight advances in microfluidic technologies for the formulation of NPs, with an emphasis on lipid-based NPs, polymeric NPs, and inorganic NPs. We provide a summary of microfluidic devices used for NP formulation with their advantages and respective challenges. Additionally, we provide our analysis for future outlooks in the field of NP formulation and microfluidics, with emerging topics of production scale-independent formulations through device parallelization and multi-step reactions within droplets.

Probing How Various Metal Ions Interact with the Surface of QDs: Implication of the Interaction Event on the Photophysics of QDs

With an aim to understand the mechanism of interaction between quantum dots (QDs) and various metal ions, fluorescence response of less-toxic and water-soluble glutathione-capped Zn-Ag-In-S (GSH@ZAIS) QDs in the presence of different metal ions has been investigated at both ensemble and single-molecule level. Fourier transform infrared (FT-IR) spectroscopy has also been performed to obtain a molecular level understanding of the interaction event. The steady-state data reveal no significant change in QD emission for alkali and alkaline earth metal ions, while there is a decrease in fluorescence intensity for transition metal (TM) and some heavy transition metal (HTM) ions. Interestingly, a significant fluorescent enhancement (FE) (19-96%) of QDs is found for Cd²⁺ ions. Time-resolved fluorescence studies reveal that all the three decay components of QDs decrease in the presence of first-row TM ions. However, in the case of Cd²⁺, the shorter component is found to increase while the longer one decreases. The analysis of data reveals that photoinduced electron transfer is responsible for fluorescence quenching of QDs in the presence of first-row TM ions and destruction/removal of trap/defect states in the case of Cd²⁺ causes the FE. In FT-IR experiments, a prominent peak at 670 cm^-1, corresponding to Cd-S stretching vibrations, indicates strong ground-state interactions between the -SH of GSH and Cd²⁺ ions. Moreover, a decrease in the diffusion coefficient of QDs in the presence of Cd²⁺ ions during fluorescence correlation spectroscopy (FCS) studies further substantiates the removal of GSH by Cd²⁺ from the surface of QDs. The optical output of this study demonstrates that ZAIS can be used for fluorescence signaling of various metal ions and in particular selective detection of Cd²⁺. More importantly, these results also suggest that Cd²⁺ can effectively be used for enhancing the fluorescence quantum yield of thiol-capped QDs such as GSH@ZAIS.

Gene Expression and Transcriptome Profiling of Changes in a Cancer Cell Line Post-Exposure to Cadmium Telluride Quantum Dots: Possible Implications in Oncogenesis

Cadmium telluride quantum dots (CdTe-QDs) are acquiring great interest in terms of their applications in biomedical sciences. Despite earlier sporadic studies on possible oncogenic roles and anticancer properties of CdTe-QDs, there is limited information regarding the oncogenic potential of CdTe-QDs in cancer progression. Here, we investigated the oncogenic effects of CdTe-QDs on the gene expression profiles of Chang cancer cells. Chang cancer cells were treated with 2 different doses of CdTe-QDs (10 and 25 μg/ml) at different time intervals (6, 12, and 24 h). Functional annotations helped identify the gene expression profile in terms of its biological process, canonical pathways, and gene interaction networks activated. It was found that the gene expression profiles varied in a time and dose-dependent manner. Validation of transcriptional changes of several genes through quantitative PCR showed that several genes upregulated by CdTe-QD exposure were somewhat linked with oncogenesis. CdTe-QD-triggered functional pathways that appear to associate with gene expression, cell proliferation, migration, adhesion, cell-cycle progression, signal transduction, and metabolism. Overall, CdTe-QD exposure led to changes in the gene expression profiles of the Chang cancer cells, highlighting that this nanoparticle can further drive oncogenesis and cancer progression, a finding that indicates the merit of immediate in vivo investigation.

Nanobioengineered Sensing Technologies Based on Cellulose Matrices for Detection of Small Molecules, Macromolecules, and Cells

Recent advancement has been accomplished in the field of biosensors through the modification of cellulose as a nano-engineered matrix material. To date, various techniques have been reported to develop cellulose-based matrices for fabricating different types of biosensors. Trends of involving cellulosic materials in paper-based multiplexing devices and microfluidic analytical technologies have increased because of their disposable, portable, biodegradable properties and cost-effectiveness. Cellulose also has potential in the development of cytosensors because of its various unique properties including biocompatibility. Such cellulose-based sensing devices are also being commercialized for various biomedical diagnostics in recent years and have also been considered as a method of choice in clinical laboratories and personalized diagnosis. In this paper, we have discussed the engineering aspects of cellulose-based sensors that have been reported where such matrices have been used to develop various analytical modules for the detection of small molecules, metal ions, macromolecules, and cells present in a diverse range of samples. Additionally, the developed cellulose-based biosensors and related analytical devices have been comprehensively described in tables with details of the sensing molecule, readout system, sensor configuration, response time, real sample, and their analytical performances.

Ternary Quantum Dots in Chemical Analysis. Synthesis and Detection Mechanisms

Ternary quantum dots (QDs) are novel nanomaterials that can be used in chemical analysis due their unique physicochemical and spectroscopic properties. These properties are size-dependent and can be adjusted in the synthetic protocol modifying the reaction medium, time, source of heat, and the ligand used for stabilization. In the last decade, several spectroscopic methods have been developed for the analysis of organic and inorganic analytes in biological, drug, environmental, and food samples, in which different sensing schemes have been applied using ternary quantum dots. This review addresses the different synthetic approaches of ternary quantum dots, the sensing mechanisms involved in the analyte detection, and the predominant areas in which these nanomaterials are used.

Functionalization of Silk by AIEgens through Facile Bioconjugation: Full-Color Fluorescence and Long-Term Bioimaging

Silkworm silk is a promising natural biopolymer for textile and biomedical applications for its remarkable flexibility, excellent biocompatibility and controllable biodegradability. The functionalization of silks makes them more versatile for flexible displays and visible bioscaffolds. However, fluorescent silks are normally fabricated through unstable physical absorption or complicated chemical reactions under harsh conditions. Herein, we developed a simple strategy for preparing fluorescent silks. Five aggregation-induced emission luminogens (AIEgens) with activated alkynes were synthesized by rational molecular design, and then reacted with silk fibers through facile metal-free click bioconjugation. The resulting conjugates show bright full-color emissions and high stability. A white light-emitting silk was fabricated by simultaneous bioconjugation with red-, green- and blue-emissive AIEgens. The red-emissive AIEgen-functionalized silks were successfully applied for long-term cell tracking and two-photon bioimaging, demonstrating great potential for tissue engineering and bioscaffold monitoring.

Recent Advancements in Nanoparticle-Based Optical Biosensors for Circulating Cancer Biomarkers

The effectiveness of cancer treatment strongly depends on the early detection of the disease. Currently, the most common diagnostic method, tissue biopsy, takes time and can be damaging to the patient. Circulating cancer biomarkers such as circulating tumor DNA, micro-RNA (miRNA), tumor proteins, exosomes, and circulating tumor cells have repeatedly demonstrated their viability as targets for minimally invasive cancer detection through liquid biopsies. However, among other things, achieving a great sensitivity of detection is still challenging due to the very low concentration of biomarkers in fluid samples. This review will discuss how the recent advances in nanoparticle-based biosensors are overcoming these practical difficulties. This report will be focusing mainly on optical transduction mechanisms of metal nanoparticles (M-NPs), quantum dots (QDs), and upconversion nanoparticles (UCNPs).

Inorganic Nanoparticles Applied for Active Targeted Photodynamic Therapy of Breast Cancer

Photodynamic therapy (PDT) is an alternative modality to conventional cancer treatment, whereby a specific wavelength of light is applied to a targeted tumor, which has either a photosensitizer or photochemotherapeutic agent localized within it. This light activates the photosensitizer in the presence of molecular oxygen to produce phototoxic species, which in turn obliterate cancer cells. The incidence rate of breast cancer (BC) is regularly growing among women, which are currently being treated with methods, such as chemotherapy, radiotherapy, and surgery. These conventional treatment methods are invasive and often produce unwanted side effects, whereas PDT is more specific and localized method of cancer treatment. The utilization of nanoparticles in PDT has shown great advantages compared to free photosensitizers in terms of solubility, early degradation, and biodistribution, as well as far more effective intercellular penetration and uptake in targeted cancer cells. This review gives an overview of the use of inorganic nanoparticles (NPs), including: gold, magnetic, carbon-based, ceramic, and up-conversion NPs, as well as quantum dots in PDT over the last 10 years (2009 to 2019), with a particular focus on the active targeting strategies for the PDT treatment of BC.

Production of cadmium sulfide quantum dots by the lithobiontic Antarctic strain Pedobacter sp. UYP1 and their application as photosensitizer in solar cells

Background

Microbes are present in almost every environment on Earth, even in those with extreme environmental conditions such as Antarctica, where rocks may represent the main refuge for life. Lithobiontic communities are composed of microorganisms capable of colonizing rocks and, as it is a not so well studied bacterial community, they may represent a very interesting source of diversity and functional traits with potential for biotechnological applications. In this work we analyzed the ability of Antarctic lithobiontic bacterium to synthesize cadmium sulfide quantum dots (CdS QDs) and their potential application in solar cells.

Results

A basaltic andesite rock sample was collected from Fildes Peninsula, King George Island, Antarctica, and processed in order to isolate lithobiontic bacterial strains. Out of the 11 selected isolates, strain UYP1, identified as Pedobacter, was chosen for further characterization and analysis due to its high cadmium tolerance. A protocol for the biosynthesis of CdS QDs was developed and optimized for this strain. After 20 and 80 min of synthesis, yellow-green and orange-red fluorescent emissions were observed under UV light, respectively. QDs were characterized through spectroscopic techniques, dynamic light scattering analysis, high-resolution transmission electron microscopy and energy dispersive x-ray spectroscopy. Nanostructures of 3.07 nm, composed of 51.1% cadmium and 48.9% sulfide were obtained and further used as photosensitizer material in solar cells. These solar cells were able to conduct electrons and displayed an open circuit voltage of 162 mV, a short circuit current density of 0.0110 mA cm⁻², and had an efficiency of conversion up to 0.0016%, which is comparable with data previously reported for solar cells sensitized with biologically produced quantum dots.

Conclusions

We report a cheap, rapid and eco-friendly protocol for the production of CdS QDs by an Antarctic lithobiontic bacterium, Pedobacter, a genus that was not previously reported as a quantum dot producer. The application of the biosynthesized QDs as sensitizer material in solar cells was validated.