Enhanced up/down-conversion luminescence and heat: Simultaneously achieving in one single core-shell structure for multimodal imaging guided therapy

Raspberry-like Nanoheterostructures Comprising Glutathione-Capped Gold Nanoclusters Grown on the Lanthanide Nanoparticle Surface

Bare lanthanide-doped nanoparticles (LnNPs), in particular, NaYF4:Yb3+,Tm3+ NPs (UCTm), have been seeded in situ with gold cations to be used in the subsequent growth of gold nanoclusters (AuNCs) in the presence of glutathione (GSH) to obtain a novel UCTm@AuNC nanoheterostructure (NHS) with a raspberry-like morphology. UCTm@AuNC displays unique optical properties (multiple absorption and emission wavelengths). Specifically, upon 350 nm excitation, it exhibits AuNC photoluminescence (PL) (500-1200 nm, λmax 650 nm) and Yb emission (λmax 980 nm); this is the first example of Yb sensitization in a UCTm@AuNC NHS. Moreover, under 980 nm excitation, it displays (i) upconverting PL of the UCTm (at the blue, red and NIR-I, ca. 800 nm, regions); (ii) two-photon PL of AuNC; and (iii) down-shifting PL of thulium (around 1470 nm). The occurrence of energy transfer from UCTm to AuNCs in the UCTm@AuNC NHS was evidenced by the drastic lengthening of the AuNC PL lifetime (τPL) (from few hundred nanoseconds to more than one hundred microseconds). Initial biological assessment of UCTm@AuNC NHSs in vitro revealed high biocompatibility and bioimaging capabilities upon near-infrared excitation.

Rare earth-doped nanocrystals for bioimaging in the near-infrared region

Rare earth-doped nanocrystals are widely used in medical diagnostics and bioimaging due to their narrow luminescence emission spectra (10-20 nm), long lifetime, and no photobleaching properties. Especially in the near-infrared (NIR) region, deeper tissue imaging can be achieved with low background luminescence and high spatial resolution. Further precise image-guided diagnosis and treatment can be achieved by using multimodal imaging such as MRI/CT/NIR/PA. Here, we focus on the construction of rare earth-doped nanocrystals, optical properties, and progress of such nanocomposites for bioimaging in the NIR region. In addition, the limitations at this stage in the field of bioimaging and the prospects for future technological development of rare earth-doped nanocrystals are present.

Sensing Leakage of Electrolytes from Magnesium Batteries Enabled by Natural AIEgens

The potential for leakage of liquid electrolytes from magnesium (Mg) batteries represents a large hurdle to future application. Despite this, there are no efficient sensing technologies to detect the leakage of liquid electrolytes. Here, we developed a sensor using laccaic acid (L-AIEgen), a naturally occurring aggregation-induced emission luminogen (AIEgens) isolated from the beetle Laccifer lacca. L-AIEgen showed good selectivity and sensitivity for Mg²⁺, a universal component of electrolytes in Mg batteries. Using L-AIEgen, we then produced a smart film (L-AIE-F) that was able to sense leakage of electrolytes from Mg batteries. L-AIE-F showed a strong "turn-on" AIE-active fluorescence at the leakage point of electrolyte from model Mg batteries. To the best of our knowledge, this is the first time that AIE technology has been used to sense the leakage of electrolytes.

Tumor-responsive nanomedicine based on Ce3+-modulated up-/downconversion dual-mode emission for NIR-II imaging-guided dynamic therapy

Chemodynamic therapy (CDT) and photodynamic therapy (PDT) based on intratumoral generation of reactive oxygen species (ROS) have been playing crucial roles in conquering tumors. However, the above therapeutic methods are still constrained by the overexpressed tumor glutathione (GSH) and intrinsic tumor resistance to conventional organic photosensitizers. Herein, lanthanide-doped nanoparticles (LDNPs) were coated with inorganic bimetallic copper and manganese silicate nanospheres (CMSNs) and modified with sodium alginate (SA) for second near-infrared (NIR-II, 1000-1700 nm) imaging-guided CDT and PDT. Interestingly, cross-relaxation (CR) pathways between Ce³⁺ and Ho³⁺ and CR between Ce³⁺ and Er³⁺ are fully exploited to enable dual-mode upconversion (UC) and NIR-II downconversion (DC) emissions of LDNPs under 980 nm laser excitation. UC emission can induce CMSNs to produce toxic singlet oxygen (¹O₂) for PDT, and the released Mn²⁺ and Cu⁺ ions caused by GSH-induced degradation of CMSNs can react with endogenous H₂O₂ to produce hydroxyl radical (˙OH) for CDT. Significantly, the ultrabright NIR-II DC emission endows the systems with exceptional optical imaging capabilities. All results affirm the potency of such an "all in one" theranostic nanomedicine integrating PDT, CDT and remarkable NIR-II imaging abilities accompanied by the function of modulating tumor microenvironment in cancer theranostics.

Hybrid Mesoporous MnO2-Upconversion Nanoparticles for Image-Guided Lung Cancer Spinal Metastasis Therapy

Upconversion nanoparticles (UCNPs) and MnO₂ composite materials have broad prospects in biological applications due to their near-infrared (NIR) imaging capability and tumor microenvironment-responsive features. Nevertheless, the synthesis of such composite nanoplatforms still faces many hurdles such as redundant processing and uneven coatings. Here, we explored a simple, rapid, and universal method for precisely controlled coating of mesoporous MnO₂ (mMnO₂) using poly(ethylene imine) as a reducing agent and potassium permanganate as a manganese source. Using this strategy, a mMnO₂ shell was successfully coated on UCNPs. We further modified the mMnO₂-coated UCNPs (UCNP@mMnO₂) with a photosensitizer (Ce6), cisplatin drug (DSP), and tumor targeting pentapeptide (TFA) to obtain a nanoplatform UCNP/Ce6@mMnO₂/DSP-TFA for treating spinal metastasis of nonsmall cell lung cancer (NSCLC-SM). The utilization of both upconversion and downconversion luminescence of UCNPs with different NIR wavelengths can avoid the simultaneous initiation of NIR-II in vivo imaging and tumor photodynamic therapy, thus reducing damage to normal tissues. This platform achieved a high synergistic effect of photodynamic therapy and chemotherapy. This leads to beneficial antitumor effects on the therapy of NSCLC-SM.

Near-infrared excitation/emission microscopy with lanthanide-based nanoparticles

Near-infrared optical imaging offers some advantages over conventional imaging, such as deeper tissue penetration, low or no autofluorescence, and reduced tissue scattering. Lanthanide-doped nanoparticles (LnNPs) have become a trend in the field of photoactive nanomaterials for optical imaging due to their unique optical features and because they can use NIR light as excitation and/or emission light. This review is focused on NaREF₄ NPs and offers an overview of the state-of-the-art investigation in their use as luminophores in optical microscopy, time-resolved imaging, and super-resolution nanoscopy based on, or applied to, LnNPs. Secondly, whenever LnNPs are combined with other nanomaterial or nanoparticle to afford nanohybrids, the characterization of their physical and chemical properties is of current interest. In this context, the latest trends in optical microscopy and their future perspectives are discussed.

Record efficiency of 1000 nm electroluminescence from a solution-processable host-free OLED

New ytterbium complexes K(Solv)_x[Yb(Lⁿ)₂] (Solv = ethanol and/or water) with 2-tosylaminobenzylidene-aryloylhydrazones (H₂L¹, aryloyl = benzoyl; H₂L², aryloyl = 2-naphthoyl) demonstrated high solubility and hole mobility (ca. 2.6 × 10^-6 cm² V^-1 s^-1), while their electron mobility and PLQY were different. The substitution of a benzoyl substituent with naphthoyl resulted in a significant increase of the electron mobility (6.9 × 10^-7vs. 1.7 × 10^-6 cm² V^-1 s^-1) and a decrease of the quantum yield (1.2% vs. 0.6%). As a result, the optimized OLEDs based on the K[Yb(Lⁿ)₂] layer demonstrated efficiencies up to 385 μW W^-1 and 441 μW W^-1, indicating the superior importance of charge mobility over the quantum yield. These are the highest efficiencies of the Yb electroluminescence.

Controlling upconversion in emerging multilayer core-shell nanostructures: from fundamentals to frontier applications

Lanthanide-based upconversion nanomaterials have recently attracted considerable attention in both fundamental research and various frontier applications owing to their excellent photon upconversion performance and favourable physicochemical properties. In particular, the emergence of multi-layer core-shell (MLCS) nanostructures offers a versatile and powerful tool to realize well-defined matrix compositions and spatial distributions of the dopant on the nanometer length scale. In contrast to the conventional nanomaterials and commonly investigated core-shell nanoparticles, the rational design of MLCS nanostructures allows us to deliberately introduce more functional properties into an upconversion system, thus providing unprecedented opportunities for the precise manipulation of energy transfer channels, the dynamic control of upconversion processes, the fine tuning of switchable emission colours and new functional integration at a single-particle level. In this review, we present a summary and discussion on the key aspects of the recent progress in lanthanide-based MLCS nanoparticles, including the manipulation of emission and lifetime, the switchable multicolour output and the lanthanide ionic interactions on the nanoscale. Benefitting from the multifunctional and versatile luminescence properties, the MLCS nanostructures exhibit great potential in diversities of frontier applications such as three-dimensional display, upconversion laser, optical memory, anti-counterfeiting, thermometry, bioimaging, and therapy. The outlook and challenges as well as perspectives for the research in MLCS nanostructure materials are also provided. This review would be greatly helpful in exploring new structural designs of lanthanide-based materials to further manipulate the upconversion phenomenon and expand their application boundaries.

Dye-Sensitized Rare Earth Nanoparticles with Up/Down Conversion Luminescence for On-Demand Gas Therapy of Glioblastoma Guided by NIR-II Fluorescence Imaging

As the primary malignant tumor in the brain, glioblastoma exhibits a high mortality due to the challenges for complete treatment by conventional therapeutic methods. It is of great importance to develop innovative therapeutic agents and methods for treatment of glioblastoma. In this work, the imaging and therapy of glioblastoma are reported by using dye sensitized core-shell NaYF₄ :Yb/Tm@NaYF₄ :Nd nanoparticles with strong up/down-conversion luminescence, of which the ultraviolet up-conversion emissions at 348 and 365 nm are significantly enhanced by nearly 28 times and used to control the release of SO₂ from 5-Amino-1,3-dihydrobenzo[c]thiophene 2,2-dioxide prodrug for gas therapy, and the second near-infrared (NIR-II) down conversion emission at 1340 nm is increased five times and applied for imaging. It is revealed that the released SO₂ molecules not only cause oxidative stress damage of tumor cells, but also induce their pro-death autophagy by down-regulating the expression of p62 and up-regulating the ratio of LC3-II/LC3-I, ultimately inhibiting tumor growth. The work demonstrates the great potential of rare earth nano-platform with functions of NIR-II imaging and photo-controlled gas therapy in the diagnosis and treatment of orthotopic glioblastoma.

Dual vis-NIR emissive bimetallic naphthoates of Eu-Yb-Gd: a new approach toward Yb luminescence intensity increase through Eu → Yb energy transfer

Homo- and heteroligand mono-, bi-, and trimetallic lanthanide naphtoates Eu_xYb_yGd_1-x-y(naph)₃(Phen)_n (n = 0, 1) were obtained and thoroughly investigated. Homoligand naphthoates of the new phase were obtained as anhydrous powders from water. The photophysical properties of the obtained compounds were studied in detail. The first example of Eu-to-Yb energy transfer was found in these systems. Careful selection of the metal ratio allowed a dual vis-NIR emissive complex with a ytterbium quantum yield of 1.5% to be obtained.

Temperature Feedback-Controlled Photothermal/Photodynamic/Chemodynamic Combination Cancer Therapy Based on NaGdF4 :Er,Yb@NaGdF4 :Nd@Cu-BIF Nanoassemblies

The intelligent design of multifunctional nanoplatforms is critical for cancer therapy. Herein, NaGdF₄ :Er,Yb@NaGdF₄ :Nd@Cu(II) boron-imidazolate frameworks (denoted as CSNPs@Cu-BIF) nanoassemblies are designed and fabricated. Upon a single 808 nm laser irradiation, the nanoassemblies not only show the outstanding photothermal conversion capacity (η = 41.7%) but also generate cytotoxic reactive oxygen species through an in situ Fenton-like reaction and fluorescence resonance energy transfer. Importantly, the nanoassemblies simultaneously introduce remarkable antitumor efficacy via photothermal/photodynamic/chemodynamic combination therapy both in vitro and in vivo. To improve the therapeutic effect of solid tumor ablation, it is highly desirable to monitor the treatment process in real-time. Multiclinical imaging modalities of ultrasonography are employed to systematically investigate the ablation mechanism of solid tumors in vivo. Furthermore, the significant difference between the eigen temperature of CSNPs@Cu-BIF nanoassemblies obtained by the temperature-sensitive emission bands signal changes and the apparent temperature recorded by the thermal imaging camera is 14.55 K at equilibrium. This current work therefore supplies an alternative strategy in temperature feedback-controlled accurate cancer therapy.

Recent Advances in Rare-Earth-Doped Nanoparticles for NIR-II Imaging and Cancer Theranostics

Fluorescence imaging in the second near infrared window (NIR-II, 1,000-1,700 nm) has been widely used in cancer diagnosis and treatment due to its high spatial resolution and deep tissue penetration depths. In this work, recent advances in rare-earth-doped nanoparticles (RENPs)-a novel kind of NIR-II nanoprobes-are presented. The main focus of this study is on the modification of RENPs and their applications in NIR-II in vitro and in vivo imaging and cancer theranostics. Finally, the perspectives and challenges of NIR-II RENPs are discussed.

808 nm Near-Infrared Light-Excited UCNPs@mSiO2-Ce6-GPC3 Nanocomposites For Photodynamic Therapy In Liver Cancer

Background

It is important to explore effective treatment for liver cancer. Photodynamic therapy (PDT) is a novel technique to treat liver cancer, but its clinical application is obstructed by limited depth of visible light penetration into tissue. The near-infrared (NIR) photosensitizer is a potential solution to the limitations of PDT for deep tumor tissue treatment.

Purpose

We aimed to investigate 808 nm NIR light-excited UCNPs@mSiO₂-Ce6-GPC3 nanocomposites for PDT in liver cancer.

Methods

In our study, 808 nm NIR light-excited upconversion nanoparticles (UCNPs) were simultaneously loaded with the photosensitizer chlorin e6 (Ce6) and the antibody glypican-3 (GPC3), which is overexpressed in hepatocellular carcinoma cells. The multitasking UCNPs@mSiO₂-Ce6-GPC3 nanoparticles under 808 nm laser irradiation with enhanced depth of penetration would enable the effective targeting of PDT.

Results

We found that the UCNPs@mSiO₂-Ce6-GPC3 nanoparticles had good biocompatibility, low toxicity, excellent cell imaging in HepG2 cancer cells and high anti-tumor effect in vitro and in vivo.

Conclusion

We believe that the utilization of 808 nm NIR excited UCNPs@mSiO₂-Ce6-GPC3 nanoparticles for PDT is a safe and potential therapeutic option for liver cancer.

Tumor Targeting Strategies of Smart Fluorescent Nanoparticles and Their Applications in Cancer Diagnosis and Treatment

Advantages such as strong signal strength, resistance to photobleaching, tunable fluorescence emissions, high sensitivity, and biocompatibility are the driving forces for the application of fluorescent nanoparticles (FNPs) in cancer diagnosis and therapy. In addition, the large surface area and easy modification of FNPs provide a platform for the design of multifunctional nanoparticles (MFNPs) for tumor targeting, diagnosis, and treatment. In order to obtain better targeting and therapeutic effects, it is necessary to understand the properties and targeting mechanisms of FNPs, which are the foundation and play a key role in the targeting design of nanoparticles (NPs). Widely accepted and applied targeting mechanisms such as enhanced permeability and retention (EPR) effect, active targeting, and tumor microenvironment (TME) targeting are summarized here. Additionally, a freshly discovered targeting mechanism is introduced, termed cell membrane permeability targeting (CMPT), which improves the tumor-targeting rate from less than 5% of the EPR effect to more than 50%. A new design strategy is also summarized, which is promising for future clinical targeting NPs/nanomedicines design. The targeting mechanism and design strategy will inspire new insights and thoughts on targeting design and will speed up precision medicine and contribute to cancer therapy and early diagnosis.

Boosting often overlooked long wavelength emissions of rare-earth nanoparticles for NIR-II fluorescence imaging of orthotopic glioblastoma

Rare-earth nanoparticles (RE NPs) with narrow long wavelength emissions have been recently investigated for their potential application for fluorescence imaging in the second near-infrared window (NIR-II). Previously these RE NPs have a very limited application in the diagnosis and treatment of deep-seated tumors such as brain tumors, due to their weak fluorescence in the range of 1300-1700 nm. Herein, we report a significant enhancement of more than 10 times regular emission of NaNdF₄ nanoparticles at 1340 nm wavelength by coating them with an inert layer of NaLuF₄, followed by sensitizing with a near-infrared dye (IR-808). We deliver these highly bright nanoparticles into the brain by using focused ultrasound to temporarily open the blood-brain barrier (BBB), and then detect the orthotopic glioblastoma by fluorescence imaging at 1340 nm. The images obtained from long wavelength fluorescence (i.e. 1340 nm) exhibited better resolution and contrast compared to the short wavelength fluorescence (i.e. 1060 nm). Our study not only provides insights for enhancing often overlooked emissions of rare-earth nanoparticles for NIR-II fluorescence imaging of deep-seated tumors, but also demonstrates great potential of focused ultrasound based technology in delivering nanotheranostic agents.

Concurrent photothermal therapy and photodynamic therapy for cutaneous squamous cell carcinoma by gold nanoclusters under a single NIR laser irradiation

The concurrent photothermal and photodynamic therapy of cutaneous squamous cell carcinoma by a single drug of Au₂₅(Capt)₁₈nanoclusters is demonstrated, together with a preliminary immune response study conducted under a single NIR laser irradiation.

A facile aqueous synthesis strategy for hexagonal phase NaGdF4 nanorods

A facile aqueous synthesis method is explored to synthesize hydrophilic β-NaGdF₄ nanorods at 60 °C.

Rational Surface Design of Upconversion Nanoparticles with Polyethylenimine Coating for Biomedical Applications: Better Safe than Brighter?

Upconversion nanoparticles (UCNPs) coated with polyethylenimine (PEI) are popular background-free optical contrast probes and efficient drug and gene delivery agents attracting attention in science, industry, and medicine. Their unique optical properties are especially useful for subsurface nanotheranostics applications, in particular, in skin. However, high cytotoxicity of PEI limits safe use of UCNP@PEI, and this represents a major barrier for clinical translation of UCNP@PEI-based technologies. Our study aims to address this problem by exploring additional surface modifications to UCNP@PEI to create less toxic and functional nanotheranostic materials. We designed and synthesized six types of layered polymer coatings that envelop the original UCNP@PEI surface, five of which reduced the cytotoxicity to human skin keratinocytes under acute (24 h) and subacute (120 h) exposure. In parallel, we examined the photoluminescence spectra and lifetime of the surface-modified UCNP@PEI. To quantify their brightness, we developed original methodology to precisely measure the colloidal concentration to normalize the photoluminescence signal using a nondigesting mass spectrometry protocol. Our results, specified for the individual coatings, show that, despite decreasing the cytotoxicity, the external polymer coatings of UCNP@PEI quench the upconversion photoluminescence in biologically relevant aqueous environments. This trade-off between cytotoxicity and brightness for surface-coated UCNPs emphasizes the need for the combined assessment of the viability of normal cells exposed to the nanoparticles and the photophysical properties of postmodification UCNPs. We present an optimized methodology for rational surface design of UCNP@PEI in biologically relevant conditions, which is essential to facilitate the translation of such nanoparticles to the clinical applications.

Core-shell rare-earth-doped nanostructures in biomedicine

The current status of the use of core-shell rare-earth-doped nanoparticles in biomedical applications is reviewed in detail. The different core-shell rare-earth-doped nanoparticles developed so far are described and the most relevant examples of their application in imaging, sensing, and therapy are summarized. In addition, the advantages and disadvantages they present are discussed. Finally, a critical opinion of their potential application in real life biomedicine is given.

Simple construction of Cu2-xS:Pt nanoparticles as nanotheranostic agent for imaging-guided chemo-photothermal synergistic therapy of cancer

Synergistic therapy has attracted intense attention in medical treatment because it can make up for the disadvantages of single therapy and greatly improve the efficacy of cancer treatment. However, it remains a challenge to build a simple system to achieve synergistic therapy. In this study, X-ray computed tomography (CT) imaging-guided chemo-photothermal synergistic therapy can be easily achieved by simple construction of Cu2-xS:Pt(0.3)/PVP nanoparticles (NPs). Cu2-xS:Pt(0.3)/PVP NPs can passively accumulate within the tumor sites, thus ensuring that many Cu2-xS:Pt(0.3)/PVP NPs are brought into the tumor cells, which can be confirmed by the results of cellular uptake, imaging, and nanoparticle biodistribution. It can be verified that the platinum ions can be released from Cu2-xS:Pt(0.3)/PVP NPs under 808 nm laser irradiation. Simultaneously, Pt(iv) ions are reduced to Pt(ii) ions by excess glutathione and then, they exhibit chemo-anticancer activities. In addition, Cu2-xS:Pt(0.3)/PVP NPs can be used as an effective photothermal agent. The results demonstrate that the efficient tumor growth inhibition effect can be realized from the mice treated with Cu2-xS:Pt(0.3)/PVP NPs under 808 nm laser irradiation by chemo-photothermal synergistic therapy. Furthermore, Cu2-xS:Pt(0.3)/PVP NPs can be thoroughly cleared through feces in a short time, showing high biosafety for further potential clinical translations.

Upconversion nanocomposite for programming combination cancer therapy by precise control of microscopic temperature

Combinational administration of chemotherapy (CT) and photothermal therapy (PTT) has been widely used to treat cancer. However, the scheduling of CT and PTT and how it will affect the therapeutic efficacy has not been thoroughly investigated. The challenge is to realize the sequence control of these two therapeutic modes. Herein, we design a temperature sensitive upconversion nanocomposite for CT-PTT combination therapy. By monitoring the microscopic temperature of the nanocomposite with upconversion luminescence, photothermal effect can be adjusted to achieve thermally triggered combination therapy with a sequence of CT, followed by PTT. We find that CT administered before PTT results in better therapeutic effect than other administration sequences when the dosages of chemodrug and heat are kept at the same level. This work proposes a programmed method to arrange the process of combination cancer therapy, which takes full advantage of each therapeutic mode and contributes to the development of new cancer therapy strategies.

The combination of chemo and photothermal therapy is widely used to treat cancer but control of chemo and thermal effects is needed for optimized treatment. Here, the authors describe an upconversion nanoparticle which can be used for controlled sequential treatment by controlling laser power.

Photodynamic Therapy Using Indocyanine Green Loaded on Super Carbonate Apatite as Minimally Invasive Cancer Treatment

Minimally invasive treatment is getting more and more important in an aging society. The purpose of this study was to explore the possibility of ICG loaded on super carbonate apatite (sCA) nanoparticles as a novel photodynamic therapy (PDT) against cancers. Using colon cancer cells, ICG uptake and anti-tumor effects were examined between the treatments of ICG and sCA-ICG. Reactive oxygen species (ROS) production and temperature rise were also evaluated to explore the underlying mechanism. Atomic force microscopy revealed that the size of sCA-ICG ranged from 10 to 20 nm. In aqueous solution with 0.5% albumin, the temperature increase after laser irradiation was 27.1°C and 23.1°C in sCA-ICG and ICG, respectively (control DW: 5.7°C). A significant increase in ROS generation was noted in cell cultures treated with sCA-ICG plus irradiation compared with those treated with ICG plus irradiation (P < 0.01). Uptake of ICG in the tumor cells significantly increased in sCA-ICG compared with ICG in vitro and in vivo The fluorescence signals of ICG in the tumor, liver, and kidney faded away in both treatments by 24 hours. Finally, the HT29 tumors treated with sCA-ICG followed by irradiation exhibited drastic tumor growth retardation (P < 0.01), whereas irradiation of tumors after injection of ICG did not inhibit tumor growth. This study shows that sCA is a useful vehicle for ICG-based PDT. Quick withdrawal of ICG from normal organs is unique to sCA-ICG and contrasts with the other nanoparticles remaining in normal organs for a long time. Mol Cancer Ther; 17(7); 1613-22. ©2018 AACR.

808 nm Light-Triggered Thermometer-Heater Upconverting Platform Based on Nd3+-Sensitized Yolk-Shell GdOF@SiO2

The realization of real-time and accurate temperature reading at subcutaneous level during the photothermal therapy (PTT) could maximally avoid the collateral damages induced by overheating effects, which remains a formidable challenge for biomedical applications. Herein, 808 nm light-driven yolk-shell GdOF:Nd³⁺/Yb³⁺/Er³⁺@SiO₂ microcapsules were developed with thermal-sensing and heating bifunctions. Under 808 nm excitation, sensitive thermometry was implemented by monitoring thermoresponsive emission from ²H_11/2/⁴S_3/2 levels of Er³⁺; meanwhile, the addition of Nd³⁺ with rich metastable intermediate levels and the yolk-shell configuration with large specific surface area triggered efficient light-to-heat conversion via enhanced nonradiative channels. The potentiality of dual-functional samples for controlled subcutaneous photothermal treatment was validated through ex vivo experiments, and the antibacterial activity against Escherichia coli was also elaborately evaluated. Results open a general avenue for designing and developing upconverting platforms with sensitive thermal-sensing and efficient heating bifunctions, which makes a significant step toward the achievement of real-time controlled PTT.

Recent Progress in Near Infrared Light Triggered Photodynamic Therapy

Nowadays, photodynamic therapy (PDT) is under the research spotlight as an appealing modality for various malignant tumors. Compared with conventional PDT treatment activated by ultraviolet or visible light, near infrared (NIR) light-triggered PDT possessing deeper penetration to lesion area and lower photodamage to normal tissue holds great potential for in vivo deep-seated tumor. In this review, recent research progress related to the exploration of NIR light responsive PDT nanosystems is summarized. To address current obstacles of PDT treatment and facilitate the effective utilization, several innovative strategies are developed and introduced into PDT nanosystems, including the conjugation with targeted moieties, O₂ self-sufficient PDT, dual photosensitizers (PSs)-loaded PDT nanoplatform, and PDT-involved synergistic therapy. Finally, the potential challenges as well as the prospective for further development are also discussed.

Injectable, NIR/pH-Responsive Nanocomposite Hydrogel as Long-Acting Implant for Chemophotothermal Synergistic Cancer Therapy

In this study, gold nanorods (GNRs) were incorporated into the hydrogel networks formed by the copolymerization of N-isopropylacrylamide (NIPAm) and methacrylated poly-β-cyclodextrin (MPCD)-based macromer to fabricate an injectable and near-infrared (NIR)/pH-responsive poly(NIPAm-co-MPCD)/GNRs nanocomposite hydrogel, which could serve as a long-acting implant for chemophotothermal synergistic cancer therapy. The nanocomposite hydrogel showed superior mechanical and swelling properties, gelation characteristics, and excellent NIR-responsive property. A hydrophobic acid-labile adamantane-modified doxorubicin (AD-DOX) prodrug was loaded into the hydrogel efficiently by host-guest interaction. The nanocomposite hydrogel exhibited a manner of sustained drug release and could sustain the slow and steady release of DOX for more than 1 month. The pH-responsive release of DOX from the nanocomposite hydrogel was observed owing to the cleavage of acid-labile hydrazone bond between DOX and the adamantyl group in acidic environment. NIR irradiation could accelerate the release of DOX from the networks, which was controlled by the collapse of the hydrogel networks induced by photothermal effect of GNRs. The in vitro cytotoxicity test demonstrated the excellent biocompatibility and photothermal effect of the nanocomposite hydrogel. Moreover, the in situ-forming hydrogel showed promising tissue biocompatibility in the mouse model study. The in vivo antitumor test demonstrated the capacity of the nanocomposite hydrogel for chemophotothermal synergistic therapy with reduced adverse effects owing to the prolonged drug retention in the tumor region and efficient photothermal effect. Therefore, this injectable and NIR/pH-responsive nanocomposite hydrogel exhibited great potential as a long term drug delivery platform for chemophotothermal synergistic cancer therapy.

Near-Infrared-Triggered Photodynamic Therapy with Multitasking Upconversion Nanoparticles in Combination with Checkpoint Blockade for Immunotherapy of Colorectal Cancer

While immunotherapy has become a highly promising paradigm for cancer treatment in recent years, it has long been recognized that photodynamic therapy (PDT) has the ability to trigger antitumor immune responses. However, conventional PDT triggered by visible light has limited penetration depth, and its generated immune responses may not be robust enough to eliminate tumors. Herein, upconversion nanoparticles (UCNPs) are simultaneously loaded with chlorin e6 (Ce6), a photosensitizer, and imiquimod (R837), a Toll-like-receptor-7 agonist. The obtained multitasking UCNP-Ce6-R837 nanoparticles under near-infrared (NIR) irradiation with enhanced tissue penetration depth would enable effective photodynamic destruction of tumors to generate a pool of tumor-associated antigens, which in the presence of those R837-containing nanoparticles as the adjuvant are able to promote strong antitumor immune responses. More significantly, PDT with UCNP-Ce6-R837 in combination with the cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) checkpoint blockade not only shows excellent efficacy in eliminating tumors exposed to the NIR laser but also results in strong antitumor immunities to inhibit the growth of distant tumors left behind after PDT treatment. Furthermore, such a cancer immunotherapy strategy has a long-term immune memory function to protect treated mice from tumor cell rechallenge. This work presents an immune-stimulating UCNP-based PDT strategy in combination with CTLA-4 checkpoint blockade to effectively destroy primary tumors under light exposure, inhibit distant tumors that can hardly be reached by light, and prevent tumor reoccurrence via the immune memory effect.

808-nm-Light-Excited Lanthanide-Doped Nanoparticles: Rational Design, Luminescence Control and Theranostic Applications

808 nm-light-excited lanthanide (Ln³⁺ )-doped nanoparticles (LnNPs) hold great promise for a wide range of applications, including bioimaging diagnosis and anticancer therapy. This is due to their unique properties, including their minimized overheating effect, improved penetration depth, relatively high quantum yields, and other common features of LnNPs. In this review, the progress of 808 nm-excited LnNPs is reported, including their i) luminescence mechanism, ii) luminescence enhancement, iii) color tuning, iv) diagnostic and v) therapeutic applications. Finally, the future outlook and challenges of 808 nm-excited LnNPs are presented.

Synthesis and characterization of Na(Gd0.5Lu0.5)F4: Nd3+,a core-shell free multifunctional contrast agent

Compared to conventional core-shell structures, core-shell free nanoparticles with multiple functionalities offer several advantages such as minimal synthetic complexity and low production cost. In this paper, we present the synthesis and characterization of Nd3+ doped Na(Gd0.5Lu0.5)F4 as a core-shell free nanoparticle system with three functionalities. Nanocrystals with 20 nm diameter, high crystallinity and a narrow particle size distributions were synthesized by the solvothermal method and characterized by various analytical techniques to understand their phase and morphology. Fluorescence characteristics under near infrared (NIR) excitation at 808 nm as well as X-ray excitation were studied to explore their potential in NIR optical and X-ray imaging. At 1.0 mol% Nd concentration, we observed a quantum yield of 25% at 1064 nm emission with 13 W/cm2 excitation power density which is sufficiently enough for imaging applications. Under 130 kVp (5 mA) power of X-ray excitation, Nd3+ doped Na(Gd0.5Lu0.5)F4 shows the characteristic emission bands of Gd3+ and Nd3+ with the strongest emission peak at 1064 nm due to Nd3+. Furthermore, magnetization measurements show that the nanocrystals are paramagnetic in nature with a calculated magnetic moment per particle of ~570 μB at 2T. These preliminary results support the suitability of the present nanophosphor as a multimodal contrast agent with three imaging features viz. optical, magnetic and X-ray.

Multifunctional PS@CS@Au–Fe3O4–FA nanocomposites for CT, MR and fluorescence imaging guided targeted-photothermal therapy of cancer cells

Multifunctional theranostic PS@CS@Au–Fe₃O₄–FA/ICG nanocomposites for MR, CT and fluorescence multiple-modal imaging-guided targeted photothermal therapy were fabricated, and they might be a promising theranostic nanoplatform for tumor diagnostics and treatment.

New advances on the marrying of UCNPs and photothermal agents for imaging-guided diagnosis and the therapy of tumors

This review primarily focuses on the new advances in the design and theranostic applications of rare earth upconversion nanoparticles (UCNPs)–NIR photothermal absorbers multifunctional nanoplatforms.