Design of new quantum dot materials for deep tissue infrared imaging

Recent insights and applications of nanocarriers-based drug delivery systems for colonic drug delivery and cancer therapy: An updated review

Colorectal cancer (CRC) is the third most prevalent malignant tumor globally and is associated with high morbidity and mortality rates. The advancement of novel nanocarrier-based drug delivery systems has revolutionized therapeutic strategies for colonic drug delivery and cancer treatment. This review provides updated insights into various nanocarrier technologies, including quantum dots (QDs), polymeric nanoparticles (PNPs), magnetic and metallic nanoparticles, solid lipid nanoparticles (SLNs), and self-microemulsifying and self-nanoemulsifying drug delivery systems (SMEDDS/SNEDDS). These nanocarriers offer enhanced drug stability, controlled release, and targeted delivery, particularly for CRC treatment, resulting in up to 70 % improved therapeutic efficacy and a significant reduction in systemic toxicity as reported in preclinical studies. The review comprehensively discusses the structural composition, mechanisms of action, therapeutic potential, and imaging capabilities of these systems, with a focus on their applications in theranostics and targeted CRC therapy. For instance, polymeric nanoparticles have demonstrated a 50 % increase in bioavailability compared to conventional formulations, while QDs have enabled real-time imaging with high precision for tumor localization. Additionally, the toxicity profiles and challenges associated with these nanocarriers are critically evaluated. Despite significant progress in preclinical and clinical studies, the review highlights the need for optimizing biocompatibility, scalability, and regulatory standards to facilitate the clinical translation of these promising technologies. Emerging formulations such as graphene quantum dots and PEGylated nanoparticles have shown potential for achieving dual therapeutic and diagnostic applications with fewer adverse effects. Overall, nanocarrier-based systems hold great potential for personalized and more effective treatments in colon-targeted therapies.

Tailored Viral-like Particles as Drivers of Medical Breakthroughs

Despite the recognized potential of nanoparticles, only a few formulations have progressed to clinical trials, and an even smaller number have been approved by the regulatory authorities and marketed. Virus-like particles (VLPs) have emerged as promising alternatives to conventional nanoparticles due to their safety, biocompatibility, immunogenicity, structural stability, scalability, and versatility. Furthermore, VLPs can be surface-functionalized with small molecules to improve circulation half-life and target specificity. Through the functionalization and coating of VLPs, it is possible to optimize the response properties to a given stimulus, such as heat, pH, an alternating magnetic field, or even enzymes. Surface functionalization can also modulate other properties, such as biocompatibility, stability, and specificity, deeming VLPs as potential vaccine candidates or delivery systems. This review aims to address the different types of surface functionalization of VLPs, highlighting the more recent cutting-edge technologies that have been explored for the design of tailored VLPs, their importance, and their consequent applicability in the medical field.

Quantum Dots Mediated Imaging and Phototherapy in Cancer Spheroid Models: State of the Art and Perspectives

Quantum Dots (QDs) are fluorescent nanoparticles known for their exceptional optical properties, i.e., high fluorescence emission, photostability, narrow emission spectrum, and broad excitation wavelength. These properties make QDs an exciting choice for bioimaging applications, notably in cancer imaging. Challenges lie in their ability to specifically label targeted cells. Numerous studies have been carried out with QDs coupled to various ligands like peptides, antibodies, aptamers, etc., to achieve efficient targeting. Most studies were conducted in vitro with two-dimensional cell monolayers (n = 8902) before evolving towards more sophisticated models. Three-dimensional multicellular tumor models better recapitulate in vivo conditions by mimicking cell-to-cell and cell-matrix interactions. To date, only few studies (n = 34) were conducted in 3D in vitro models such as spheroids, whereas these models could better represent QDs behavior in tumors compared to monolayers. Thus, the purpose of this review is to present a state of the art on the studies conducted with Quantum Dots on spheroid models for imaging and phototherapy purposes.

Recent developments in germanium containing clusters in intermetallics and nanocrystals

Multimetallic clusters can be described as building blocks in intermetallics, compounds prepared from all metals and/or semi-metals, and in Zintl phases, a subset of intermetallics containing metals with large differences in electronegativity. In many cases, these intermetallic and Zintl phases provide the first clue for the possibilities of bond formation between metals and semi-metals. Recent advances in multimetallic clusters found in Zintl phases and nanoparticles focusing on Ge with transition metals and semi-metals is presented. Colloidal routes to Ge nanocrystals provide an opportunity for kinetically stabilized Ge-metal and Ge-semi-metal bonding. These routes provide crystalline nanoclusters of Ge, hereafter referred to as nanocrystals, that can be structurally characterized. Compositions of Ge nanocrystals containing transition metals, and the semi-metals, Sb, Bi, and Sn, whose structures have recently been elucidated through EXAFS, will be presented along with potential applications.

Trifunctional Graphene Quantum Dot@LDH Integrated Nanoprobes for Visualization Therapy of Gastric Cancer

Visualization technology has become a trend in tumor therapy in recent years. The superior optical properties of graphene quantum dots (GQDs) make them suitable candidates for tumor diagnosis, but their tumor targeting and drug-carrying capacities are still not ideal for treatment. Sulfur-doped graphene quantum dots (SGQDs) with stable fluorescence are prepared in a previous study. A reliable strategy by associating layered double hydroxides (LDHs) and etoposide (VP16) is designed for precise visualization therapy. Trifunctional LDH@SGQD-VP16 integrated nanoprobes can simultaneously achieve targeted aggregation, fluorescence visualization, and chemotherapy. LDH@SGQD-VP16 can accumulate in the tumor microenvironment, owing to pH-sensitive properties and long-term photostability in vivo, which can provide a basis for cancer targeting, real-time imaging, and effect tracking. The enhanced therapeutic and attenuated side effects of VP16 are demonstrated, and the apoptosis caused by LDH@SGQD-VP16 is ≈2.7 times higher than that of VP16 alone, in HGC-27 cells. This work provides a theoretical and experimental basis for LDH@SGQD-VP16 as a potential multifunctional agent for visualization therapy of gastric cancer.

Extending the Near-Infrared Emission Range of Indium Phosphide Quantum Dots for Multiplexed In Vivo Imaging

This report of the reddest emitting indium phosphide quantum dots (InP QDs) to date demonstrates tunable, near-infrared (NIR) photoluminescence (PL) as well as PL multiplexing in the first optical tissue window while avoiding toxic constituents. This synthesis overcomes the InP "growth bottleneck" and extends the emission peak of InP QDs deeper into the first optical tissue window using an inverted QD heterostructure, specifically ZnSe/InP/ZnS core/shell/shell nanoparticles. The QDs exhibit InP shell thickness-dependent tunable emission with peaks ranging from 515-845 nm. The high absorptivity of InP yields effective photoexcitation of the QDs with UV, visible, and NIR wavelengths. These nanoparticles extend the range of tunable direct-bandgap emission from InP-based nanostructures, effectively overcoming a synthetic barrier that has prevented InP-based QDs from reaching their full potential as NIR imaging agents. Multiplexed lymph node imaging in a mouse model demonstrates the potential of the NIR-emitting InP particles for in vivo imaging.

Photoluminescent Nanomaterials for Medical Biotechnology

Creation of various photoluminescent nanomaterials has significantly expanded the arsenal of approaches used in modern biomedicine. Their unique photophysical properties can significantly improve the sensitivity and specificity of diagnostic methods, increase therapy effectiveness, and make a theranostic approach to treatment possible through the application of nanoparticle conjugates with functional macromolecules. The most widely used nanomaterials to date are semiconductor quantum dots; gold nanoclusters; carbon dots; nanodiamonds; semiconductor porous silicon; and up-conversion nanoparticles. This paper considers the promising groups of photoluminescent nanomaterials that can be used in medical biotechnology: in particular, for devising agents for optical diagnostic methods, sensorics, and various types of therapy.

Inexpensive Near-Infrared Fluorimeters: Enabling Translation of nIR-Based Assays to the Field

The practical impact of analytical probes that transduce in the near-infrared (nIR) has been dampened by the lack of cost-effective and portable nIR fluorimeters. Herein, we demonstrate straightforward designs for an inexpensive microplate reader and a portable fluorimeter. These instruments require minimally complex machining and fabrication and operate with an open-source programming language (Python). Complete wiring diagrams, assembly diagrams, and scripts are provided. To demonstrate the utility of these two instruments, we performed high-throughput and field-side measurements of soil samples to evaluate the effect of soil management strategies on extracellular proteolytic, cellulolytic, and lignin-modifying activities. This was accomplished with fluorescent enzyme probes that utilized uniquely sensitive transducers exclusive to the nIR spectrum, single-walled carbon nanotubes. We also used the portable fluorimeter to evaluate spatial variations of proteolytic activity within individual field plots, while minimizing the effects of soil storage and handling. These demonstrations indicate the utility of these fluorimeters for translating analytical probes that operate in the nIR beyond the laboratory and into actual use.

PEGylated CuInS2/ZnS quantum dots inhibit neurite outgrowth by downregulating the NGF/p75NTR/MAPK pathway

The widespread application of cadmium-free CuInS₂/ZnS QDs has raised great concern regarding their potential toxicity to humans. To date, toxicological data related to CuInS₂/ZnS QDs are scarce. Neurons play extraordinary roles in regulating the activities of organs and systems, and serious consequences occur when neurons are damaged. Currently, the potential toxicity of CuInS₂/ZnS QDs on neurons has not been fully elucidated. Here, we investigate the neurotoxicity of PEGylated CuInS₂/ZnS (CuInS₂/ZnS-PEG) QDs on neuron-like PC12 cells. We found that CuInS₂/ZnS-PEG QDs were taken up by PC12 cells, but at a concentration range from 0 to 100 μg/mL, they did not affect the survival rate of the PC12 cells. In addition, we found that CuInS₂/ZnS-PEG QDs significantly inhibited neurite outgrowth from and the differentiation of PC12 cells in the presence of NGF, while COOH-modified CuInS₂/ZnS QDs or free PEG did not have a similar effect. Further studies showed that CuInS₂/ZnS-PEG QDs obviously downregulated the expression of low-affinity NGF receptor (p75^NTR) and subsequently negatively regulated the downstream MAPK cascade by dephosphorylating ERK1/2 and AKT. Taken together, these results suggest that CuInS₂/ZnS-PEG QDs disturb NGF signal transduction from external stimuli to relevant internal signals, thus affecting normal biological processes such as neurite outgrowth and cell differentiation.

Exploring the Biocompatibility of Near-IR CuInSexS2-x/ZnS Quantum Dots for Deep-Tissue Bioimaging

Near-infrared (NIR) emitting quantum dots (QDs) with emission in the biological transparency windows (NIR-I: 650-950 nm and NIR-II: 1000-1350 nm) are promising candidates for deep-tissue bioimaging. However, they typically contain toxic heavy metals such as cadmium, mercury, arsenic, or lead. We report on the biocompatibility of high brightness CuInSe_xS_2-x/ZnS (CISeS/ZnS) QDs with a tunable emission covering the visible to NIR (550-1300 nm peak emission) and quantify the transmission of their photoluminescence through multiple biological components to evaluate their use as imaging agents. In general, CISeS/ZnS QDs were less cytotoxic to mouse fibroblast cells when compared with commercial CdSe/ZnS and InP/ZnS QDs. Surprisingly, InP/ZnS QDs significantly upregulated expression of apoptotic genes in mouse fibroblast cells, while cells exposed to CISeS/ZnS QDs did not. These findings provide insight into biocompatibility and cytotoxicity of CISeS/ZnS QDs that could be used for bioimaging.

NIR Imaging of the Integrin-Rich Head and Neck Squamous Cell Carcinoma Using Ternary Copper Indium Selenide/Zinc Sulfide-Based Quantum Dots

The efficient intraoperative identification of cancers requires the development of the bright, minimally-toxic, tumor-specific near-infrared (NIR) probes as contrast agents. Luminescent semiconductor quantum dots (QDs) offer several unique advantages for in vivo cellular imaging by providing bright and photostable fluorescent probes. Here, we present the synthesis of ZnCuInSe/ZnS core/shell QDs emitting in NIR (~750 nm) conjugated to NAVPNLRGDLQVLAQKVART (A20FMDV2) peptide for targeting α_vβ₆ integrin-rich head and neck squamous cell carcinoma (HNSCC). Integrin α_vβ₆ is usually not detectable in nonpathological tissues, but is highly upregulated in HNSCC. QD-A20 showed α_vβ₆ integrin-specific binding in two-dimension (2D) monolayer and three-dimension (3D) spheroid in vitro HNSCC models. QD-A20 exhibit limited penetration (ca. 50 µm) in stroma-rich 3D spheroids. Finally, we demonstrated the potential of these QDs by time-gated fluorescence imaging of stroma-rich 3D spheroids placed onto mm-thick tissue slices to mimic imaging conditions in tissues. Overall, QD-A20 could be considered as highly promising nanoprobes for NIR bioimaging and imaging-guided surgery.

Nanomedicine Approaches for Advanced Diagnosis and Treatment of Atherosclerosis and Related Ischemic Diseases

Cardiovascular diseases (CVDs) remain one of the major causes of mortality worldwide. In response to this and other worldwide health epidemics, nanomedicine has emerged as a rapidly evolving discipline that involves the development of innovative nanomaterials and nanotechnologies and their applications in therapy and diagnosis. Nanomedicine presents unique advantages over conventional medicines due to the superior properties intrinsic to nanoscopic therapies. Once used mainly for cancer therapies, recently, tremendous progress has been made in nanomedicine that has led to an overall improvement in the treatment and diagnosis of CVDs. This review elucidates the pathophysiology and potential targets of atherosclerosis and associated ischemic diseases. It may be fruitful to pursue future work in the nanomedicine-mediated treatment of CVDs based on these targets. A comprehensive overview is then provided featuring the latest preclinical and clinical outcomes in cardiovascular imaging, biomarker detection, tissue engineering, and nanoscale delivery, with specific emphasis on nanoparticles, nanostructured scaffolds, and nanosensors. Finally, the challenges and opportunities regarding the future development and clinical translation of nanomedicine in related fields are discussed. Overall, this review aims to provide a deep and thorough understanding of the design, application, and future development of nanomedicine for atherosclerosis and related ischemic diseases.

Mitochondria-targeted aggregation-induced emission active near infrared fluorescent probe for real-time imaging

Mitochondria are essential organelles in eukaryotic cells and act as the energy powerhouse and biosynthetic compartment. Fluorescent dyes are widely used powerful molecular tools for analytical sensing and optical imaging. Low photostability, short excitation and emission wavelengths, and aggregation-induced quenching effects restrict the application of traditional commercial mitochondrial fluorescent probes for bioimaging. In this study, using rhodamine as the acceptor and phenothiazine as the donor, we synthesized a novel mitochondrial-targeted near infrared (NIR) fluorescent probe, MIT-PZR. Due to low cytotoxicity, great photostability and high specificity for mitochondria targeting, MIT-PZR has enormous potential for cell imaging. Furthermore, with a sizeable Stokes shift (emission peak at 705 nm), MIT-PZR penetrated tissues providing stable red fluorescence for imaging in vivo. The histological assessment of various tissues after treatment with MIT-PZR indicated that it has good biocompatibility. Thus, MIT-PZR is a promising mitochondrial NIR fluorescent probe for future application in clinical diagnosis and modern biological research.

Introductory lecture: origins and applications of efficient visible photoluminescence from silicon-based nanostructures

This review highlights many spectroscopy-based studies and selected phenomenological studies of silicon-based nanostructures that provide insight into their likely PL mechanisms, and also covers six application areas.

Bypassing pro-survival and resistance mechanisms of autophagy in EGFR-positive lung cancer cells by targeted delivery of 5FU using theranostic Ag2S quantum dots

Targeted drug delivery systems that combine imaging and therapeutic functions in a single structure have become very popular in nanomedicine. Near-infrared (NIR) emitting Ag₂S quantum dots (QDs) are excellent candidates for this task. Here, we have developed PEGylated Ag₂S QDs functionalized with Cetuximab (Cet) antibody and loaded with an anticancer drug, 5-fluorouracil (5FU). These theranostic QDs were used for targeted NIR imaging and treatment of lung cancer using low (H1299) and high (A549) Epidermal Growth Factor Receptor (EGFR) overexpressing cell lines. The Cet conjugated QDs effectively and selectively delivered 5FU to A549 cells and provided significantly enhanced cell death associated with apoptosis. Interestingly, while treatment of cells with free 5FU activated autophagy, a cellular mechanism conferring resistance to cell death, these EGFR targeting multimodal QDs significantly overcame drug resistance compared to 5FU treatment alone. The improved therapeutic outcome of 5FU delivered to A549 cells by Cet conjugated Ag₂S QDs is suggested as the synergistic outcome of enhanced receptor mediated uptake of nanoparticles, and hence the drug, coupled with suppressed autophagy even in the absence of addition of an autophagy suppressor.

pH-Sensitive Visible or Shortwave Infrared Quantum Dot Nanoprobes Using Conformation-Switchable Copolymeric Ligands

Intracellular and extracellular pH are key parameters in many physiological processes and diseases. For example, the extracellular pH of the tumor micro-environment is slightly more acidic than in healthy tissue. In vivo mapping of the extracellular pH within the tumor would therefore improve our understanding of the tumor physiology. Fluorescent semiconductor quantum dots (QDs) represent interesting probes for in vivo imaging, in particular in the shortwave infrared (SWIR) range. Here, pH-sensitive QD nanoprobes are developed using a conformation-switchable surface chemistry. The central fluorescent QD is coated with a copolymer ligand and conjugated to gold nanoparticle quenchers. As the pH decreases from physiological (7.5) to slightly acidic (5.5-6), the copolymer reversibly shrinks, which increases the energy transfer between the QD and the gold quenchers and modulates the QD fluorescence signal. This enables the design of ratiometric QD probes for biological pH range emitting in the visible or SWIR range. In addition, these probes can be easily encapsulated and remain functional within ghost erythrocyte membranes, which facilitate their in vivo application.

Infrared Quantum Dots: Progress, Challenges, and Opportunities

Infrared technologies provide tremendous value to our modern-day society. The need for easy-to-fabricate, solution-processable, tunable infrared active optoelectronic materials has driven the development of infrared colloidal quantum dots, whose band gaps can readily be tuned by dimensional constraints due to the quantum confinement effect. In this Perspective, we summarize recent progress in the development of infrared quantum dots both as infrared light emitters ( e.g., in light-emitting diodes, biological imaging, etc.) as well as infrared absorbers ( e.g., in photovoltaics, solar fuels, photon up-conversion, etc.), focusing on how fundamental breakthroughs in synthesis, surface chemistry, and characterization techniques are facilitating the implementation of these nanostructures into exploratory device architectures as well as in emerging applications. We discuss the ongoing challenges and opportunities associated with infrared colloidal quantum dots.

Label-free detection of biotoxins via a photo-induced force infrared spectrum at the single-molecular level

Schematic illustration of photo-induced force microscopy combine principal component analysis detected and distinguish single molecule particles of biotoxins AT, RT/ETX with label-free.

Nanomedicine in cancer stem cell therapy: from fringe to forefront

Nanomedicine is the spin-off of modern medicine and nanotechnology and aims to prevent and treat diseases using nanoscale materials such as biocompatible nanoparticles and nanorobots. Targeted cellular and tissue-specific clinical applications with maximal therapeutic effects and insignificant side effects could be achieved by the pursuit of nanotechnology in medicine and healthcare regimen. The majority of conventional cancer therapies eliminate the cells of the tumor but not the cancer stem cells (CSCs). Conversely, the use of nanotechnology in CSC-based therapies is an emerging field of biomedical sciences. This article summarizes the recent trends and application of nanomedicine especially in CSC therapy along with its limitations.

Engineered nanomaterials and human health: Part 2. Applications and nanotoxicology (IUPAC Technical Report)

Research on engineered nanomaterials (ENM) has progressed rapidly from the very early stages of studying their unique, size-dependent physicochemical properties and commercial exploration to the development of products that influence our everyday lives. We have previously reviewed various methods for synthesis, surface functionalization, and analytical characterization of ENM in a publication titled ‘Engineered Nanomaterials: Preparation, Functionalization and Characterization’. In this second, inter-linked document, we first provide an overview of important applications of ENM in products relevant to human healthcare and consumer goods, such as food, textiles, and cosmetics. We then highlight the challenges for the design and development of new ENM for bio-applications, particularly in the rapidly developing nanomedicine sector. The second part of this document is dedicated to nanotoxicology studies of ENM in consumer products. We describe the various biological targets where toxicity may occur, summarize the four nanotoxicology principles, and discuss the need for careful consideration of the biodistribution, degradation, and elimination routes of nanosized materials before they can be safely used. Finally, we review expert opinions on the risk, regulation, and ethical aspects of using engineered nanomaterials in applications that may have direct or indirect impact on human health or our environment.

Fluorescent Nanoparticles for the Guided Surgery of Ovarian Peritoneal Carcinomatosis

Complete surgical resection is the ideal cure for ovarian peritoneal carcinomatosis, but remains challenging. Fluorescent guided surgery can be a promising approach for precise cytoreduction when appropriate fluorophore is used. In the presence paper, we review already developed near- and short-wave infrared fluorescent nanoparticles, which are currently under investigation for peritoneal carcinomatosis fluorescence imaging. We also highlight the main ways to improve the safety of nanoparticles, for fulfilling prerequisites of clinical application.

Near infrared fluorescent peptide nanoparticles for enhancing esophageal cancer therapeutic efficacy

Various types of nanoparticles have been proposed for targeted drug delivering, imaging, and tracking of therapeutic agents. However, highly biocompatible nanoparticles with structure-induced fluorescence and capability to conjugate with biomarkers and drugs remain lacking. This research proposes and synthesizes fluorescent nanoparticles (f-PNPs) assembled by cyclic peptides to combine imaging and drug delivering for esophageal cancer (EC). To achieve tumor targeting, f-PNPs are first conjugated with RGD moieties to selectively target EC cells via αvβ3 integrin; the nanoparticles are then embedded with epirubicin (EPI). Cell viability assays and analysis of tissue histology reveal that EPI-loaded RGD-f-PNPs (RGD-f-PNPs/EPI) led to significantly reduced cardiotoxicity and improved anti-tumor activity compared to EPI alone. Moreover, the drug delivery to tumor sites and therapeutic responses could be monitored with near-infrared fluorescence using RGD-f-PNPs/EPI. This unique nanoparticle system may lead to potential approaches for bioorganic fluorescence-based delivering, imaging, and drug release tracking.

Quantum dot-decorated semiconductor micro- and nanoparticles: A review of their synthesis, characterization and application in photocatalysis

Quantum dot (QD)-decorated semiconductor micro- and nanoparticles are a new class of functional nanomaterials that have attracted considerable interest for their unique structural, optical and electronic properties that result from the large surface-to-volume ratio and the quantum confinement effect. In addition, because of QDs' excellent light-harvesting capacity, unique photoinduced electron transfer, and up-conversion behaviour, semiconductor nanoparticles decorated with quantum dots have been used widely in photocatalytic applications for the degradation of organic pollutants in both the gas and aqueous phases. This review is a comprehensive overview of the recent progress in synthesis methods for quantum dots and quantum dot-decorated semiconductor composites with an emphasis on their composition, morphology and optical behaviour. Furthermore, various approaches used for the preparation of QD-based composites are discussed in detail with respect to visible and UV light-induced photoactivity. Finally, an outlook on future development is proposed with the goal of overcoming challenges and stimulating further research into this promising field.

Clickable-Zwitterionic Copolymer Capped-Quantum Dots for in Vivo Fluorescence Tumor Imaging

In the last decades, fluorescent quantum dots (QDs) have appeared as high-performance biological fluorescent nanoprobes and have been explored for a variety of biomedical optical imaging applications. However, many central challenges still exist concerning the control of the surface chemistry to ensure high biocompatibility, low toxicity, antifouling, and specific active targeting properties. Regarding in vivo applications, circulation time and clearance of the nanoprobe are also key parameters to control the design and characterization of new optical imaging agents. Herein, the complete design and characterization of a peptide-near-infrared-QD-based nanoprobe for biomedical optical imaging is presented from the synthesis of the QDs and the zwitterionic-azide copolymer ligand, enabling a bio-orthogonal coupling, till the final in vivo test through all the characterization steps. The developed nanoprobes show high fluorescence emission, controlled grafting rate, low toxicity, in vitro active specific targeting, and in vivo long circulating blood time. This is, to our knowledge, the first report characterizing the in vivo circulation kinetics and tumor accumulation of targeted zwitterionic QDs.

Biocompatible Semiconductor Quantum Dots as Cancer Imaging Agents

Approximately 1.7 million new cases of cancer will be diagnosed this year in the United States leading to 600 000 deaths. Patient survival rates are highly correlated with the stage of cancer diagnosis, with localized and regional remission rates that are much higher than for metastatic cancer. The current standard of care for many solid tumors includes imaging and biopsy with histological assessment. In many cases, after tomographical imaging modalities have identified abnormal morphology consistent with cancer, surgery is performed to remove the primary tumor and evaluate the surrounding lymph nodes. Accurate identification of tumor margins and staging are critical for selecting optimal treatments to minimize recurrence. Visible, fluorescent, and radiolabeled small molecules have been used as contrast agents to improve detection during real-time intraoperative imaging. Unfortunately, current dyes lack the tissue specificity, stability, and signal penetration needed for optimal performance. Quantum dots (QDs) represent an exciting class of fluorescent probes for optical imaging with tunable optical properties, high stability, and the ability to target tumors or lymph nodes based on surface functionalization. Here, state-of-the-art biocompatible QDs are compared with current Food and Drug Administration approved fluorophores used in cancer imaging and a perspective on the pathway to clinical translation is provided.

NIR-Emitting Alloyed CdTeSe QDs and Organic Dye Assemblies: A Nontoxic, Stable, and Efficient FRET System

In the present work, we synthesize Near Infrared (NIR)-emitting alloyed mercaptopropionic acid (MPA)-capped CdTeSe quantum dots (QDs) in a single-step one-hour process, without the use of an inert atmosphere or any pyrophoric ligands. The quantum dots are water soluble, non-toxic, and highly photostable and have high quantum yields (QYs) up to 84%. The alloyed MPA-capped CdTeSe QDs exhibit a red-shifted emission, whose color can be tuned between visible and NIR regions (608-750 nm) by controlling the Te:Se molar ratio in the precursor mixtures and/or changing the time reaction. The MPA-capped QDs were characterized by UV-visible absorption spectroscopy, fluorescence spectroscopy, transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), and zeta potential measurements. Photostability studies were performed by irradiating the QDs with a high-power xenon lamp. The ternary MPA-CdTeSe QDs showed greater photostability than the corresponding binary MPA-CdTe QDs. We report the Förster resonance energy transfer (FRET) from the MPA-capped CdTeSe QDs as energy donors and Cyanine5 NHS-ester (Cy5) dye as an energy acceptor with efficiency (E) up to 95%. The distance between the QDs and dye (r), the Förster distance (R₀), and the binding constant (K) are reported. Additionally, cytocompatibility and cell internalization experiments conducted on human cancer cells (HeLa) cells revealed that alloyed MPA-capped CdTeSe QDs are more cytocompatible than MPA-capped CdTe QDs and are capable of ordering homogeneously all over the cytoplasm, which allows their use as potential safe, green donors for biological FRET applications.

Synthesis of silver sulfide nanoparticles and their photodetector applications

Silver sulfide nanoparticles (Ag₂S NPs) are currently being explored as infrared active nanomaterials that can provide environmentally stable alternatives to heavy metals such as lead. In this paper, we describe the novel synthesis of Ag₂S NPs by using a sonochemistry method and the fabrication of photodetector devices through the integration of Ag₂S NPs atop a graphene sheet. We have also synthesized Li-doped Ag₂S NPs that exhibited a significantly enhanced photodetector sensitivity via their enhanced absorption ability in the UV-NIR region. First-principles calculations based on a density functional theory formalism indicated that Li-doping produced a dramatic enhancement of NIR photoluminescence of the Ag₂S NPs. Finally, high-performance photodetectors based on CVD graphene and Ag₂S NPs were demonstrated and investigated; the hybrid photodetectors based on Ag₂S NPs and Li-doped Ag₂S NPs exhibited a photoresponse of 2723.2 and 4146.0 A W⁻¹ respectively under a light exposure of 0.89 mW cm⁻² at 550 nm. Our novel approach represents a promising and effective method for the synthesis of eco-friendly semiconducting NPs for photoelectric devices.

Silver sulfide nanoparticles (Ag₂S NPs) are currently being explored as infrared active nanomaterials that can provide environmentally stable alternatives to heavy metals such as lead.

Far-red fluorescent probes for canonical and non-canonical nucleic acid structures: current progress and future implications

Our review presents the recent progress on far-red fluorescent probes of canonical and non-canonical nucleic acid (NA) structures, critically discusses the design principles, applications, limitations and outline the future prospects of developing newer probes with target-specificity for different NA structures.

Biochemical mechanisms of dose-dependent cytotoxicity and ROS-mediated apoptosis induced by lead sulfide/graphene oxide quantum dots for potential bioimaging applications

Colloidal quantum dots (CQD) have attracted considerable attention for biomedical diagnosis and imaging as well as biochemical analysis and stem cell tracking. In this study, quasi core/shell lead sulfide/reduced graphene oxide CQD with near infrared emission (1100 nm) were prepared for potential bioimaging applications. The nanocrystals had an average diameter of ~4 nm, a hydrodynamic size of ~8 nm, and a high quantum efficiency of 28%. Toxicity assay of the hybrid CQD in the cultured human mononuclear blood cells does not show cytotoxicity up to 200 µg/ml. At high concentrations, damage to mitochondrial activity and mitochondrial membrane potential (MMP) due to the formation of uncontrollable amounts of intracellular oxygen radicals (ROS) was observed. Cell membrane and Lysosome damage or a transition in mitochondrial permeability were also noticed. Understanding of cell-nanoparticle interaction at the molecular level is useful for the development of new fluorophores for biomedical imaging.

Charge-Neutral, Stable, Non-Cytotoxic, Near-Infrared SnS Aqueous Quantum Dots for High Signal-to-Noise-Ratio Biomedical Imaging

We have synthesized charge-neutral, stable, non-cytotoxic, bright, near-infrared (NIR) SnS quantum dots (QDs) by first making Cysteamine-capped SnS QDs in glycerol under acidic conditions followed by lengthening the capping molecule with peptide bonds by reacting the capping molecules with glycine and subsequent heat treatment at 200°C for 4 hours. The obtained stable SnS QDs exhibited a band gap of 1.5 eV and a strong, narrow NIR emission peak at 830 nm with a quantum yield of 4.6%. The suspension could be stable for more than 1 month without aggregation or emission decay. The positively charged SnS QDs were further neutralized by 3-mercaptoproprionic acid (MPA) through electrostatic attraction. The MPA neutralized SnS QDs were shown to be non-cytotoxic at concentrations 6 times the typical QDs concentration for immunostaining. Low-noise, optimal NIR immunofluorescent imaging of vascular endothelial growth factor (VEGF) on 3T3 cells and Tn antigen on HT29 cells was achieved by using streptavidin (SA)-linked MPA-neutralized SnS QDs with a SA:QD molar ratio of 22:1 to bind to biotinylated secondary antibody bound on the primary antibody that was bound on the targeted antigen on the cell membrane with a high signal-to noise ratio (SNR) of 35.

Patterning and fluorescence tuning of quantum dots with haptic-interfaced bubble printing

Semiconductor quantum dots (QDs) are attractive for a wide range of applications such as displays, light-emitting devices, and sensors due to their properties such as tunable fluorescence wavelength, high brightness, and narrow bandwidth. Most of the applications require precise patterning of QDs with targeted properties on solid-state substrates. Herein, we have developed a haptic-interfaced bubble printing (HIBP) technique to enable high-resolution (510 nm) high-throughput (>10⁴ μm s^-1) patterning of QDs with strong emission tunability and to significantly enhance the accessibility of the technique via a smartphone device. The scalability and versatility of the HIBP are demonstrated in our arbitrary patterning of QDs on plasmonic substrates. A detailed study of plasmonic and photothermal interactions is performed via programmed stage movements to realize tunability of the emission wavelength and lifetime. Finally, the influence of the hand movement on the properties of the printed QDs in terms of emission wavelength tuning from yellow to blue is established. This work provides a single-step macroscale platform to manipulate nanoscale properties at high resolution and high throughput.

High-Resolution Bubble Printing of Quantum Dots

Semiconductor quantum dots (QDs) feature excellent properties, such as high quantum efficiency, tunable emission frequency, and good fluorescence stability. Incorporation of QDs into new devices relies upon high-resolution and high-throughput patterning techniques. Herein, we report a new printing technique known as bubble printing (BP), which exploits a light-generated microbubble at the interface of colloidal QD solution and a substrate to directly write QDs into arbitrary patterns. With the uniform plasmonic hot spot distribution for high bubble stability and the optimum light-scanning parameters, we have achieved full-color QD printing with submicron resolution (650 nm), high throughput (scanning rate of ∼10^-2 m/s), and high adhesion of the QDs to the substrates. The printing parameters can be optimized to further control the fluorescence properties of the patterned QDs, such as emission wavelength and lifetime. The patterning of QDs on flexible substrates further demonstrates the wide applicability of this new technique. Thus, BP technique addresses the barrier of achieving a widely applicable, high-throughput and user-friendly patterning technique in the submicrometer regime, along with simultaneous fluorescence modification capability.

Imaging the pharmacology of nanomaterials by intravital microscopy: Toward understanding their biological behavior

Therapeutic nanoparticles (NPs) can deliver cytotoxic chemotherapeutics and other drugs more safely and efficiently to patients; furthermore, selective delivery to target tissues can theoretically be accomplished actively through coating NPs with molecular ligands, and passively through exploiting physiological "enhanced permeability and retention" features. However, clinical trial results have been mixed in showing improved efficacy with drug nanoencapsulation, largely due to heterogeneous NP accumulation at target sites across patients. Thus, a clear need exists to better understand why many NP strategies fail in vivo and not result in significantly improved tumor uptake or therapeutic response. Multicolor in vivo confocal fluorescence imaging (intravital microscopy; IVM) enables integrated pharmacokinetic and pharmacodynamic (PK/PD) measurement at the single-cell level, and has helped answer key questions regarding the biological mechanisms of in vivo NP behavior. This review summarizes progress to date and also describes useful technical strategies for successful IVM experimentation.

Targeted imaging and induction of apoptosis of drug-resistant hepatoma cells by miR-122-loaded graphene-InP nanocompounds

BACKGROUND

Currently, graphene oxide has attracted growing attention as a drug delivery system due to its unique characteristics. Furthermore, utilization of microRNAs as biomarkers and therapeutic strategies would be particularly attractive because of their biological mechanisms and relatively low toxicity. Therefore, we have developed functionalized nanocompounds consisted of graphene oxide, quantum dots and microRNA, which induced cancer cells apoptosis along with targeted imaging.

RESULTS

In the present study, we synthesized a kind of graphene-P-gp loaded with miR-122-InP@ZnS quantum dots nanocomposites (GPMQNs) that, in the presence of glutathione, provides controlled release of miR-122. The miR-122 actively targeted liver tumor cells and induced their apoptosis, including drug-resistant liver tumor cells. We also explored the near-infrared fluorescence and potential utility for targeting imaging of InP@ZnS quantum dots. To further understand the molecular mechanism of GPMQNs-induced apoptosis of drug-resistant HepG2/ADM hepatoma cells, the relevant apoptosis proteins and signal pathways were explored in vitro and in vivo. Furthermore, near-infrared GPMQNs, which exhibited reduced photon scattering and auto-fluorescence, were applied for tumor imaging in vivo to allow for deep tissue penetration and three-dimensional imaging.

CONCLUSION

In conclusion, techniques using GPMQNs could provide a novel targeted treatment for liver cancer, which possessed properties of targeted imaging, low toxicity, and controlled release.

Obtaining control of cell surface functionalizations via Pre-targeting and Supramolecular host guest interactions

The use of mammalian cells for therapeutic applications is finding its way into modern medicine. However, modification or "training" of cells to make them suitable for a specific application remains complex. By envisioning a chemical toolbox that enables specific, but straight-forward and generic cellular functionalization, we investigated how membrane-receptor (pre)targeting could be combined with supramolecular host-guest interactions based on β-cyclodextrin (CD) and adamantane (Ad). The feasibility of this approach was studied in cells with membranous overexpression of the chemokine receptor 4 (CXCR4). By combining specific targeting of CXCR4, using an adamantane (Ad)-functionalized Ac-TZ14011 peptide (guest; KD = 56 nM), with multivalent host molecules that entailed fluorescent β-CD-Poly(isobutylene-alt-maleic-anhydride)-polymers with different fluorescent colors and number of functionalities, host-guest cell-surface modifications could be studied in detail. A second set of Ad-functionalized entities enabled introduction of additional surface functionalities. In addition, the attraction between CD and Ad could be used to drive cell-cell interactions. Combined we have shown that supramolecular interactions, that are based on specific targeting of an overexpressed membrane-receptor, allow specific and stable, yet reversible, surface functionalization of viable cells and how this approach can be used to influence the interaction between cells and their surroundings.

Nanomaterials for In Vivo Imaging

In vivo imaging, which enables us to peer deeply within living subjects, is producing tremendous opportunities both for clinical diagnostics and as a research tool. Contrast material is often required to clearly visualize the functional architecture of physiological structures. Recent advances in nanomaterials are becoming pivotal to generate the high-resolution, high-contrast images needed for accurate, precision diagnostics. Nanomaterials are playing major roles in imaging by delivering large imaging payloads, yielding improved sensitivity, multiplexing capacity, and modularity of design. Indeed, for several imaging modalities, nanomaterials are now not simply ancillary contrast entities, but are instead the original and sole source of image signal that make possible the modality's existence. We address the physicochemical makeup/design of nanomaterials through the lens of the physical properties that produce contrast signal for the cognate imaging modality-we stratify nanomaterials on the basis of their (i) magnetic, (ii) optical, (iii) acoustic, and/or (iv) nuclear properties. We evaluate them for their ability to provide relevant information under preclinical and clinical circumstances, their in vivo safety profiles (which are being incorporated into their chemical design), their modularity in being fused to create multimodal nanomaterials (spanning multiple different physical imaging modalities and therapeutic/theranostic capabilities), their key properties, and critically their likelihood to be clinically translated.

Optical nanoprobes for biomedical applications: shining a light on upconverting and near-infrared emitting nanoparticles for imaging, thermal sensing, and photodynamic therapy

Shining a light on spectrally converting lanthanide (Ln³⁺)-doped nanoparticles: progress, trends, and challenges in Ln³⁺-nanoprobes for near-infrared bioimaging, nanothermometry, and photodynamic therapy.

One-Pot Aqueous Synthesization of Near-Infrared Quantum Dots for Bioimaging and Photodynamic Therapy of Gliomas

BACKGROUND

As the early detection and total destruction of gliomas are essential for longer survival, we attempted to synthesize a quantum dot (QD) that is capable of recognizing glioma cells for imaging and photodynamic therapy.

METHODS

Using a one-pot aqueous approach, near infrared-emitting CdTe was produced. After detection of its physicochemical characteriistics, it was conjugated with RGD. The emission images were observed with confocal microscopy. To test its toxicity, CdTe-RGD at various concentrations was separately added to a human glioma cell line (U251) and a mouse embryo fibroblast cell line (3T3) (control) for incubation in dark conditions. To test its photodynamic effect, the U251 and 3T3 cells were then irradiated for 5-60 min, using a 632.8-nm laser.

RESULTS

This QD (Φ = 3.75 nm, photoluminescence (PL) peak wavelength = 700 nm, photoluminescence quantum yield (PLQY) = 20 %), was a spherical crystal with excellent monodispersity. Under a confocal microscope, U251 cells were visualized, but not the 3T3 cells. In dark conditions, the survival rates of both U251 and 3T3 cells were above 85 %. After laser irradiation, the survival rate of U251 cells decreased to 37 ± 1.6 % as the irradiation time and the CdTe-RGD concentration were increased.

CONCLUSIONS

With good physicochemical characteriistics and low toxicity, this QD-RGD has broad prospects for use in the biomedical imaging and photodynamic therapy of gliomas.

In Vivo Targeting and Imaging of Atherosclerosis Using Multifunctional Virus-Like Particles of Simian Virus 40

Atherosclerosis is a leading cause of death globally. Targeted imaging and therapeutics are desirable for the detection and treatment of the disease. In this study, we developed trifunctional Simian virus 40 (SV40)-based nanoparticles for in vivo targeting and imaging of atherosclerotic plaques. These novel trifunctional SV40-based nanoparticles encapsulate near-infrared quantum dots and bear a targeting element and a drug component. Using trifunctional SV40-based nanoparticles, we were able to noninvasively fluorescently image atherosclerotic plaques in live intact ApoE(-/-) mice. Near-infrared quantum dots encapsulated in the SV40 virus-like particles showed prominent optical properties for in vivo imaging. When different targeting peptides for vascular cell adhesion molecule-1, macrophages, and fibrin were used, early, developmental, and late stages of atherosclerosis could be targeted and imaged in live intact ApoE(-/-) mice, respectively. Targeted SV40 virus-like particles also delivered an increased concentration of the anticoagulant drug Hirulog to atherosclerosis plaques. Our study provides novel SV40-based nanoparticles with multivalency and multifunctionality suitable for in vivo imaging, molecular targeting, and drug delivery in atherosclerosis.

In vivo biodistribution studies and ex vivo lymph node imaging using heavy metal-free quantum dots

Quantum dots (QDs) are attractive photoluminescence probes for biomedical imaging due to their unique photophysical properties. However, the potential toxicity of QDs has remained a major obstacle to their clinical use because they commonly incorporate the toxic heavy metal cadmium within the core of the QDs. In this work, we have evaluated a novel type of heavy metal-free/cadmium-free and biocompatible QD nanoparticles (bio CFQD(®) nanoparticles) with a good photoluminescence quantum yield. Sentinel lymph node mapping is an increasingly important treatment option in the management of breast cancer. We have demonstrated their potential for lymph node mapping by ex vivo imaging of regional lymph nodes after subcutaneous injection in the paw of rats. Using photoluminescence imaging and chemical extraction measurements based on elemental analysis by inductively coupled plasma mass spectroscopy, the quantum dots are shown to accumulate quickly and selectively in the axillary and thoracic regional lymph nodes. In addition, lifetime imaging microscopy of the QD photoluminescence indicates minimal perturbation to their photoluminescence properties in biological systems.

Suppressing the Fluorescence Blinking of Single Quantum Dots Encased in N-type Semiconductor Nanoparticles

N-type semiconductor indium tin oxide (ITO) nanoparticles are used to effectively suppress the fluorescence blinking of single near-infrared-emitting CdSeTe/ZnS core/shell quantum dots (QDs), where the ITO could block the electron transfer from excited QDs to trap states and facilitate more rapid regeneration of neutral QDs by back electron transfer. The average blinking rate of QDs is significantly reduced by more than an order of magnitude and the largest proportion of on-state is 98%, while the lifetime is not considerably reduced. Furthermore, an external electron transfer model is proposed to analyze the possible effect of radiative, nonradiative, and electron transfer pathways on fluorescence blinking. Theoretical analysis based on the model combined with measured results gives a quantitative insight into the blinking mechanism.

Bio-compatibility and cytotoxicity studies of water-soluble CuInS2-ZnS-AFP fluorescence probe in liver cancer cells

BACKGROUND

The oncogenesis of hepatocellular carcinoma (HCC) is not clear. The current methods of the pertinent studies are not precise and sensitive. The present study was to use liver cancer cell line to explore the bio-compatibility and cytotoxicity of ternary quantum dots (QDs) probe and to evaluate the possible application of QDs in HCC.

METHODS

CuInS2-ZnS-AFP fluorescence probe was designed and synthesized to label the liver cancer cell HepG2. The cytotoxicity of CuInS2-ZnS-AFP probe was evaluated by MTT experiments and flow cytometry.

RESULTS

The labeling experiments indicated that CuInS2-ZnS QDs conjugated with AFP antibody could enter HepG2 cells effectively and emit intensive yellow fluorescence by ultraviolet excitation without changing cellular morphology. Toxicity tests suggested that the cytotoxicity of CuInS2-ZnS-AFP probe was significantly lower than that of CdTe-ZnS-AFP probe (t test, F=0.8, T=-69.326, P<0.001). For CuInS2-ZnS-AFP probe, time-effect relationship was presented in intermediate concentration (>20%) groups (P<0.05) and dose-effect relationship was presented in almost all of the groups (P<0.05).

CONCLUSION

CuInS2-ZnS-AFP QDs probe had better bio-compatibility and lower cytotoxicity compared with CdTe-ZnS-AFP probe, and could be used for imaging the living cells in vitro.