Upconversion optical/magnetic resonance imaging-guided small tumor detection and in vivo tri-modal bioimaging based on high-performance luminescent nanorods

The role of NF-κB in breast cancer initiation, growth, metastasis, and resistance to chemotherapy

Breast cancer (BC) is the second most fatal disease and is the prime cause of cancer allied female deaths. BC is caused by aberrant tumor suppressor genes and oncogenes regulated by transcription factors (TFs) like NF-κB. NF-κB is a pro-inflammatory TF that crucially alters the expressions of various genes associated with inflammation, cell progression, metastasis, and apoptosis and modulates a network of genes that underlie tumorigenesis. Herein, we focus on NF-κB signaling pathways, its regulators, and the rationale for targeting NF-κB. This review also includes TFs that maintain NF-κB crosstalk and their roles in promoting angiogenesis and metastasis. In addition, we discuss the importance of combination therapies, resistance to treatment, and potential novel therapeutic strategies including nanomedicine that targets NF-κB.

Shape programmable T1-T2 dual-mode MRI nanoprobes for cancer theranostics

The shape effect is an important parameter in the design of novel nanomaterials. Engineering the shape of nanomaterials is an effective strategy for optimizing their bioactive performance. Nanomaterials with a unique shape are beneficial to blood circulation, tumor targeting, cell uptake, and even improved magnetism properties. Therefore, magnetic resonance imaging (MRI) nanoprobes with different shapes have been extensively focused on in recent years. Different from other multimodal imaging techniques, dual-mode MRI can provide imaging simultaneously by a single instrument, which can avoid differences in penetration depth, and the spatial and temporal resolution of multiple imaging devices, and ensure the accurate matching of spatial and temporal imaging parameters for the precise diagnosis of early tumors. This review summarizes the latest developments of nanomaterials with various shapes for T₁-T₂ dual-mode MRI, and highlights the mechanism of how shape intelligently affects nanomaterials' longitudinal or transverse relaxation, namely sphere, hollow, core-shell, cube, cluster, flower, dumbbell, rod, sheet, and bipyramid shapes. In addition, the combination of T₁-T₂ dual-mode MRI nanoprobes and advanced therapeutic strategies, as well as possible challenges from basic research to clinical transformation, are also systematically discussed. Therefore, this review will help others quickly understand the basic information on dual-mode MRI nanoprobes and gather thought-provoking ideas to advance the subfield of cancer nanomedicine.

Recent advances in ZnO-based photosensitizers: Synthesis, modification, and applications in photodynamic cancer therapy

Zinc oxide nanoparticles (ZnO NPs) are important semiconductor materials with interesting photo-responsive properties. During the past, ZnO-based NPs have received considerable attention for photodynamic therapy (PDT) due to their biocompatibility and excellent potential of generating tumor-killing reactive oxygen species (ROS) through gentle photodynamic activation. This article provides a comprehensive review of the recent developments and improvements in optical properties of ZnO NPs as photosensitizers for PDT. The optical properties of ZnO-based photosensitizers are significantly dependent on their charge separation, absorption potential, band gap engineering, and surface area, which can be adjusted/tuned by doping, compositing, and morphology control. Here, we first summarize the recent progress in the charge separation capability, absorption potential, band gap engineering, and surface area of nanosized ZnO-based photosensitizers. Then, morphology control that is closely related to their synthesis method is discussed. Following on, the state-of-art for the ZnO-based NPs in the treatment of hypoxic tumors is comprehensively reviewed. Finally, we provide some outlooks on common targeted therapy methods for more effective tumor killing, including the attachment of small molecules, antibodies, ligands molecules, and receptors to NPs which further improve their selective distribution and targeting, hence improving the therapeutic effectiveness. The current review may provide useful guidance for the researchers who are interested in this promising dynamic cancer treatment technology.

Multimodal channel cancer chemotherapy by 2D functional gadolinium metal-organic framework

2D nanomaterials generally exhibit enhanced physiochemical and biological functions in biomedical applications due to their high surface-to-volume ratio and surface charge. Conventional cancer chemotherapy based on nanomaterials has been hindered by their low drug loading and poor penetration in tumor tissue. To overcome these difficulties, novel materials systems are urgently needed. Hereby, the lanthanide-based porphyrin metal–organic framework (MOF) nanosheets (NSs) with promising cancer imaging/chemotherapy capacities are fabricated, which display superior performance in the drug loading and tumor tissue penetration. The biodegradable PPF-Gd NSs deliver an ultrahigh drug loading (>1500%) and demonstrate the stable and highly sensitive stimuli-responsive degradation/release for multimodal tumor imaging and cancer chemotherapy. Meanwhile, PPF-Gd NSs also exhibit excellent fluorescence and magnetic resonance imaging capability in vitro and in vivo. Compared to the traditional doxorubicin (DOX) chemotherapy, the in vivo results confirm the evident suppression of the tumor growth by the PPF-Gd/DOX drug delivery system with negligible side effects. This work further supports the potential of lanthanide-based MOF nanomaterials as biodegradable systems to promote the cancer theranostics technology development in the future.

Multimodal channel cancer chemotherapy by 2D functional gadolinium metal-organic framework

2D nanomaterials generally exhibit enhanced physiochemical and biological functions in biomedical applications due to their high surface-to-volume ratio and surface charge. Conventional cancer chemotherapy based on nanomaterials has been hindered by their low drug loading and poor penetration in tumor tissue. To overcome these difficulties, novel materials systems are urgently needed. Hereby, the lanthanide-based porphyrin metal-organic framework (MOF) nanosheets (NSs) with promising cancer imaging/chemotherapy capacities are fabricated, which display superior performance in the drug loading and tumor tissue penetration. The biodegradable PPF-Gd NSs deliver an ultrahigh drug loading (>1500%) and demonstrate the stable and highly sensitive stimuli-responsive degradation/release for multimodal tumor imaging and cancer chemotherapy. Meanwhile, PPF-Gd NSs also exhibit excellent fluorescence and magnetic resonance imaging capability in vitro and in vivo. Compared to the traditional doxorubicin (DOX) chemotherapy, the in vivo results confirm the evident suppression of the tumor growth by the PPF-Gd/DOX drug delivery system with negligible side effects. This work further supports the potential of lanthanide-based MOF nanomaterials as biodegradable systems to promote the cancer theranostics technology development in the future.

The Spectroscopic Properties and Microscopic Imaging of Thulium-Doped Upconversion Nanoparticles Excited at Different NIR-II Light

Lanthanide-doped upconversion nanoparticles (UCNPs) are promising bioimaging nanoprobes due to their excellent photostability. As one of the most commonly used lanthanide activators, Tm³⁺ ions have perfect ladder-type electron configuration and can be directly excited by bio-friendly near-infrared-II (NIR-II) wavelengths. Here, the emission characteristics of Tm³⁺-doped nanoparticles under laser excitations of different near-infrared-II wavelengths were systematically investigated. The 1064 nm, 1150 nm, and 1208 nm lasers are proposed to be three excitation strategies with different response spectra of Tm³⁺ ions. In particular, we found that 1150 nm laser excitation enables intense three-photon 475 nm emission, which is nearly 100 times stronger than that excited by 1064 nm excitation. We further optimized the luminescence brightness after investigating the luminescence quenching mechanism of bare NaYF₄: Tm (1.75%) core. After growing an inert shell, a ten-fold increase of emission intensity was achieved. Combining the advantages of NIR-II wavelength and the higher-order nonlinear excitation, a promising facile excitation strategy was developed for the application of thulium-doped upconversion nanoparticles in nanoparticles imaging and cancer cell microscopic imaging.

Bright Blue, Green, and Red Luminescence from Dye-Sensitized Core@Shell Upconversion Nanophosphors under 800 nm Near-Infrared Light

In this study, Li-based blue- and green-emitting core@shell (C@S) upconversion nanophosphors (UCNPs) and NaGdF4-based red-emitting C@S UCNPs were synthesized, and IR-808 dyes were conjugated with the C@S UCNPs to enhance upconversion (UC) luminescence. The surface of the as-synthesized C@S UCNPs, which was originally capped with oleic acid, was modified with BF4- to conjugate the IR-808 dye having a carboxyl functional group to the surface of the UCNPs. After the conjugation with IR-808 dyes, absorbance of the UCNPs was significantly increased. As a result, dye-sensitized blue (B)-, green (G)-, and red (R)-emitting UCNPs exhibited 87-fold, 10.8-fold, and 110-fold enhanced UC luminescence compared with B-, G-, and R-emitting Nd3+-doped C@S UCNPs under 800 nm near-infrared (NIR) light excitation, respectively. Consequently, dye-sensitized UCNPs exhibiting strong UC luminescence under 800 nm NIR light excitation have high applicability in a variety of biological applications.

Gadolinium-based bimodal probes to enhance T1-Weighted magnetic resonance/optical imaging

Gd³⁺-based contrast agents have been extensively used for signal enhancement of T₁-weighted magnetic resonance imaging (MRI) due to the large magnetic moment and long electron spin relaxation time of the paramagnetic Gd³⁺ ion. The key requisites for the development of Gd³⁺-based contrast agents are their relaxivities and stabilities which can be achieved by chemical modifications. These modifications include coordinating Gd³⁺ with a chelator such as diethylenetriamine pentaacetic acid (DTPA) or 1,4,7,10-Tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA), encapsulating Gd³⁺ in nanoparticles, conjugation to biomacromolecules such as polymer micelles and liposomes, or non-covalent binding to plasma proteins. In order to have a coherent diagnostic and therapeutic approach and to understand diseases better, the combination of MRI and optical imaging (OI) techniques into one technique entity has been developed to overcome the conventional boundaries of either imaging modality used alone through bringing the excellent spatial resolution of MRI and high sensitivity of OI into full play. Novel MRI and OI bimodal probes have been extensively studied in this regard. This review is an attempt to shed some light on the bimodal imaging probes by summarizing all recent noteworthy publications involving Gd³⁺ containing MR-optical imaging probes. The several key elements such as novel synthetic strategy, high sensitivity, biocompatibility, and targeting of the probes are highlighted in the review. STATEMENT OF SIGNIFICANCE: The present article aims at giving an overview of the existing bimodal MRI and OI imaging probes. The review structured as a series of examples of paramagnetic Gd³⁺ ions, either as ions in the crystalline structure of inorganic materials or chelates for contrast enhancement in MRI, while they are used as optical imaging probes in different modes. The comprehensive review focusing on the synthetic strategies, characterizations and properties of these bimodal imaging probes will be helpful in a way to prepare related work.

Acute hepatotoxicity of multimodal targeted imaging contrast agent NaLuF4:Gd,Yb,Er-PEG/PEI-FA in mice

In the past few decades, upconversion nanoparticles (abbreviated as UCNPs) have been more widely applied in the biomedical fields, such as in vitro and in vivo upconversion fluorescent bioimaging, photodynamic therapy, biological macromolecular detection, imaging mediated drug delivery and so on. But meanwhile, there is still not much research on the acute toxicity of upconversion nanoparticles in vivo, such as acute hepatotoxicity. In this work, we studied the in vivo biodistribution and acute hepatotoxicity of multimodal targeted contrast agent NaLuF₄:Gd,Yb,Er-PEG/PEI-FA nanoprobe, which were synthesized by the solvothermal method and modified with Polyethylene glycol (PEG), Polyetherimide (PEI), folic acid (FA) on the surface. The acute hepatotoxicity in mice was systematically assessed after tail vein injection of different concentration of UCNPs. The results showed that NaLuF₄:Gd,Yb,Er-PEG/PEI-FA nanoparticles with an average diameter of 44.5 ± 10.4 nm, and three typical upconversion fluorescence emission bands at 520 nm, 540 nm and 660 nm under the excitation of 980 nm laser. In vivo distribution experiments results demonstrated that approximately 87% of UCNPs injected through the tail vein accumulate in the liver. In the acute hepatotoxicity test, the intravenously injection dose of UCNPs was 10, 40, 70 and 100 mg/kg, respectively. The body weight, blood routine, serum biochemistry, histomorphology and liver oxidative stress were detected and observed no significant acute hepatotoxicity damage under the injection dose of 100 mg/kg. In conclusion, NaLuF₄:Gd,Yb,Er-PEG/PEI-FA nanoprobes are safe and reliable, and have potential applications in the field of tumor targeted multimodal imaging.

Semiconductor ZnO based photosensitizer core–shell upconversion nanoparticle heterojunction for photodynamic therapy

NaErF₄@ZnO UCNPs for potential application in thyroid tumor cell PDT.

Multifunctional BiF3:Ln3+ (Ln = Ho, Er, Tm)/Yb3+ nanoparticles: an investigation on the emission color tuning, thermosensitivity, and bioimaging

Pure cubic phase and uniform BiF₃:Ln³⁺ (Ln = Ho, Er, Tm)/Yb³⁺ nanoparticles (NPs) were prepared by coprecipitation. The growth mechanism of BiF₃:2%Er³⁺/20%Yb³⁺ NPs was proposed based on evolution analysis of the time-dependent morphology, in which BiF₃:2%Er³⁺/20%Yb³⁺ was formed through the growth process of “nucleation to crystallization and Ostwald ripening”. The upconversion luminescence (UCL) properties and mechanism of BiF₃:Ln³⁺ (Ln = Ho, Er, Tm)/Yb³⁺ under dual-wavelength excitation were also systematically investigated. The emission intensity of BiF₃:2%Er³⁺/20%Yb³⁺ by dual-wavelength excitation (λ = 980 nm + 1550 nm) was 1.49 times more than that excited by 1550 nm or 980 nm individually. Furthermore, the properties of the bright white and multicolor UCL showed that yellow, purple, green, or pinkish light could be observed by controlling the doping concentration of Ln³⁺ (Ln = Yb, Er, Tm, and Ho), indicating that they had potential applications in backlight sources of color displays and security labeling. The temperature sensitivity of BiF₃:2%Er³⁺/20%Yb³⁺ exhibited a downward tendency and its max value was about 0.0036 K⁻¹ at 273 K. Cell toxicity tests showed that the UCNPs in phospholipid aqueous solution presented low cytotoxicity. Also, in vivo imaging and X-ray imaging revealed that the BiF₃:2%Er³⁺/20%Yb³⁺ NPs had deep penetration and high contrast, which meant it could be used as a potential probe and contrast agent in in vivo optical bioimaging.

Multifunctional BiF₃:Ln³⁺(Ln = Ho, Er, Tm)/Yb³⁺ UCLNPs presented better performances in dual-wavelength synergy, thermosensitivity, emission color tuning, and bioimaging.

Advances in the application of upconversion nanoparticles for detecting and treating cancers

The detection and treatment of cancer cells at an early stage are crucial for prolonging the survival time and improving the quality of life of patients. Upconversion nanoparticles (UCNPs) have unique physical and chemical advantages and likely provide a platform for detecting and treating cancer cells at an early stage. In this paper, the principle of UCNPs as chemical sensors based on fluorescence resonance energy transfer (FRET) has been briefly introduced. Research progress in such chemical sensors for detecting and analyzing bioactive substances and heavy metal ions at the subcellular level has been summarized. The principle of UCNP-based nanoprobe-targeting of cancer cells has been described. The research progress in using nanocomposites for cancer cell detection, namely cancer cell targeted imaging and tissue staining, has been discussed. In the field of cancer treatment, the principles and research progress of UCNPs in photodynamic therapy and photothermal therapy of cancer cells are systematically discussed. Finally, the prospects for UCNPs and remaining challenges to UCNP application in the field of cancer diagnosis and treatment are briefly described. This review provides powerful theoretical guidance and useful practical information for the research and application of UCNPs in the field of cancer.

A high performance Sc-based nanoprobe for through-skull fluorescence imaging of brain vessels beyond 1500 nm

Optical bioimaging that works in the second near infrared region (NIR-II, 1000-1700 nm) has emerged as a next generation imaging technique with superior imaging sensitivity and spatial resolution compared to traditional optical imaging utilizing visible and near-infrared lights (below 900 nm). Herein, a new Sc-based NIR-II probe was explored for high performance NIR-II in vivo bioimaging and optical imaging-guided non-invasive brain blood vessel visualization. The lanthanide doped Sc-based probes (KSc2F7:Yb3+/Er3+) possess a pure orthorhombic phase structure with size control by adjusting the F- ion content. These probes present a dominant red upconversion (UC) emission, which is significantly different from the traditional NaYF4:Yb/Er host, which usually has a green UC emission. More importantly, apart from the dominant red UC emission, these probes also possess a strong NIR-II downconversion (DC) emission centered at 1525 nm, which is usually ignored for bioimaging applications. In vivo NIR-II imaging reveals that our explored Sc-based nanorods are promising probes for highly sensitive optical imaging. Moreover, non-invasive through-skull fluorescence bioimaging of brain vessels with high spatial resolution was demonstrated. Therefore, it is expected that Sc-based nanomaterials with unique dominant red UC and DC NIR-II emissions beyond 1500 nm are ideal probes for bio-applications.

Theranostic nanocomposite from upconversion luminescent nanoparticles and black phosphorus nanosheets

An anti-cancer campaign might not be easily achieved through a single therapeutic modality. Collaboration of multimodal therapies and diagnosis could be vital to win the battle against cancer. In this context, we synthesized a multifunctional theranostic nanocomposite (UCNP–BPNS) from upconversion nanoparticles (UCNP) and black phosphorus nanosheets (BPNS) for synergistic photothermal/photodynamic therapies in vitro and dual modal imaging. Core–shell UCNP (NaYF₄:Yb,Er@NaGdF₄) and BPNS were synthesized using solvo-thermal and liquid exfoliation methods, respectively, and then covalently conjugated after UCNP was modified with polyacrylic acid and BPNS with methoxypolyethylene glycol amine. The experimental results validate that the nanocomposite exhibited a good photothermal therapy (PTT) effect under 808 nm laser irradiation, endorsing the apparent heat conversion effect of BPNS. Besides, a very good photodynamic therapy (PDT) effect was achieved under 980 nm laser irradiation of the nanocomposite due to Förster resonance energy transfer from UCNP to BPNS that generated singlet oxygen (¹O₂). The synergistic PTT/PDT therapeutic effect provided by UCNP–BPNS under simultaneous 808 and 980 nm laser irradiation was significantly higher than either PTT or PDT alone. Furthermore, due to the merit of the outer shell coated on the surface of the core of UCNP, the nanocomposite exhibited good potential for magnetic resonance and upconversion luminescence imaging. These results demonstrated that our multifunctional nanocomposite has promising theranostic efficacy under near infrared laser irradiation.

We successfully synthesized a multifunctional theranostic nanocomposite from upconversion nanoparticles and black phosphorus nanosheets for synergistic photothermal/photodynamic therapies in vitro and dual modal imaging.

Short-wave near-infrared emissive GdPO4:Nd3+theranostic probe forin vivobioimaging beyond 1300 nm

The optical probes working in the second near-infrared (NIR-II) window have attracted increasing research interest for their advantages of high tissue penetration depth, low autofluorescence, and unprecedentedly improved imaging sensitivity and spatial resolution. Therefore, it is of great significance to design a new nanoplatform by integration of NIR-II optical imaging and drug delivery functions. Herein, a multifunctional nanoplatform based on GdPO₄:Nd³⁺ yolk–shell sphere was developed for dual-modal in vivo NIR-II/X-ray bioimaging and pH-responsive drug delivery. The in vivo NIR-II bioimaging and real-time tracking presented that these probes were mainly accumulated in liver and spleen. Moreover, owing to the large X-ray absorption coefficient of Gd³⁺, these probes are successfully used as superior X-ray imaging agents than iobitridol. The in vivo toxicity assessments demonstrate the low biotoxicity of the GdPO₄:Nd³⁺ spheres in living animals. More importantly, apart from the excellent dual-modal bioimaging, these yolk–shell-structured probes were also used as ideal nanotransducer for pH-responsive drug delivery of doxorubicin (DOX). These findings open up the opportunity of designing theranostic nanoplatform with integration of imaging-based diagnosis and therapy.

A multifunctional theranostic nanoplatform based on GdPO₄:Nd³⁺ yolk–shell sphere was developed for dual-modal in vivo NIR-II/X-ray bioimaging and pH-responsive drug delivery.

Soft X-ray activated NaYF4:Gd/Tb scintillating nanorods for in vivo dual-modal X-ray/X-ray-induced optical bioimaging

Lanthanide (Ln) nanocrystals using soft X-ray as an excitation source have received significant research interest due to the advantages of unlimited penetration depth of X-ray light. In this study, we demonstrated an efficient scintillator based on NaYF₄:Gd nanorods (denoted as NRs) doped with different contents of terbium (Tb) ions for optical bioimaging under X-ray irradiation. The experimental results showed that the emission intensity was correlated to the doping contents of Tb³⁺, and the largest emission intensity was achieved by doping 15% Tb under excitation by soft X-ray light. In addition, the emission intensity of the as-prepared NRs can be significantly improved by increasing the excitation power and irradiation times of the X-ray. Owing to the efficient X-ray-induced emission, these NRs were successfully used as probes for X-ray-induced optical bioimaging with high sensitivity. In addition, the dual-modal X-ray imaging and X-ray induced optical bioimaging were performed on a mouse, which indicated that the NRs were promising dual-modal bioprobes. Therefore, the X-ray activation nature of the designed NRs makes them promising probes for biomedicine and X-ray-induced photodynamic therapy (PDT) applications owing to the unlimited penetration depth of X-ray excitation source and absence of autofluorescence.

Green synthesis of highly dispersed ytterbium and thulium co-doped sodium yttrium fluoride microphosphors for in situ light upconversion from near-infrared to blue in animals

We report a simple, low cost and environmentally friendly method to prepare NaYF₄:Yb³⁺, Tm³⁺ upconversion microphosphors (UCMPs) by thermal decomposition of rare earth-trifluoroacetate precursors using paraffin as the high boiling non-coordinating solvent. The UCMPs exhibited cubic phase with defined shape and bright upconversion luminescence. After coating with amphiphilic polymers of phospholipid-polyethylene glycol, the NaYF₄:Yb³⁺, Tm³⁺ UCMPs were highly dispersed in aqueous solutions and exhibited low cytotoxicity. Furthermore, we explored the use of the micro-injected micro-sized NaYF₄:Yb³⁺, Tm³⁺ particles for converting of near infrared into blue light in mice brain. The in vivo macroscopic upconversion luminescence imaging results showed that UCMPs located at 1mm depth in the brain could be clearly distinguished. Microscopic upconversion luminescence imaging of the brain sections in vitro revealed that the UCMPs embedded at the particular location in brain tissues of mice were stable without significant diffusion in two weeks.

Depleted upconversion luminescence in NaYF4:Yb3+,Tm3+ nanoparticles via simultaneous two-wavelength excitation

Depleted UCL in NaYF₄:Yb³⁺,Tm³⁺ UCNPs upon simultaneous excitation at 980 nm and 1550 nm is attributed to the STED process.