Gd-based upconversion nanocarriers with yolk-shell structure for dual-modal imaging and enhanced chemotherapy to overcome multidrug resistance in breast cancer

Stimuli-Responsive Codelivery System Self-Assembled from in Situ Dynamic Covalent Reaction of Macrocyclic Disulfides for Cancer Magnetic Resonance Imaging and Chemotherapy

Supramolecular self-assembly has gained increasing attention to construct multicomponent drug delivery systems for cancer diagnosis and therapy. Despite that these self-assembled nanosystems present surprising properties beyond that of each subcomponent, the spontaneous nature of co-self-assembly causes significant difficulties in control of the synthesis process and consequently leads to unsatisfactory influences in downstream applications. Hence, we utlized an in situ dynamic covalent reaction based on thiol-disulfide exchange to slowly produce disulfide macrocycles, which subsequently triggered the co-self-assembly of an anticancer drug (doxorubicin, DOX) and a magnetic resonance imaging (MRI) contrast agent of ultrasmall iron oxide nanoparticles (IO NPs). It showed concentration regulation of macrocyclic disulfides, DOX, and IO NPs by a dynamic covalent self-assembly (DCS) strategy, resulting in a stable codelivery nanosystem with high drug loading efficiency of 37.36%. More importantly, disulfide macrocycles in the codelivery system could be reduced and broken by glutathione (GSH) in tumor cells, thus leading to disassembly of nanostructures and intellgent release of drugs. These stimuli-responsive performances have been investigated via morphologies and molecular structures, revealing greatly enhanced dual-modal MRI abilities and smart drug release under the trigger of GSH. Moreover, the codelivery system conjugated with a targeting molecule of cyclic Arg-Gly-Asp (cRGD) exhibited significant biocompatibility, MR imaging, and chemotherapeutic anticancer effect in vitro and in vivo. These results indicated that in situ dynamic covalent chemistry enhanced the control over co-self-assembly and paved the way to develop more potential drug delivery systems.

Using host-guest interactions at the interface of quantum dots to load drug molecules for biocompatible, safe, and effective chemo-photodynamic therapy against cancer

Combining photodynamic therapy (PDT) and chemotherapy (CHT) by loading an anti-cancer drug and a photosensitizer (PS) into the same delivery nanosystem has been proposed as an effective approach to achieve synergistic effects for a safe cancer treatment. However, exploring an ideal delivery nanosystem has been challenging, because the noncovalent interactions must be maintained between the multiple components to produce a stable yet responsive nanostructure that takes into account the encapsulation of drug molecules. We addressed this issue by engineering the interfacial interaction between Ag₂S quantum dots (QDs) using a pillararene derivative to direct the co-self-assembly of the entire system. The high surface area-to-volume ratio of the Ag₂S QDs provided ample hydrophobic space to accommodate the anti-drug molecule doxrubicine. Moreover, Ag₂S QDs served as PSs triggered by 808 nm near-infrared (NIR) light and also as carriers for high-efficiency delivery of drug molecules to the tumor site. Drug release experiments showed smart drug release under the acidic microenvironments (pH 5.5) in tumor cells. Additionally, the Ag₂S QDs demonstrated outstanding PDT ability under NIR light, as confirmed by extracellular and intracellular reactive oxygen species generation. Significant treatment efficacy of the chemo-photodynamic synergistic therapy for cancer using the co-delivery system was demonstrated via in vitro and in vivo studies. These findings suggest that our system offers intelligent control of CHT and PDT, which will provide a promising strategy for constructing hybrid systems with synergistic effects for advanced applications in biomedicine, catalysis, and optoelectronics.

Boosting Checkpoint Immunotherapy with Biomaterials

The immune checkpoint blockade (ICB) therapy has revolutionized the field of cancer treatment, while low response rates and systemic toxicity limit its clinical outcomes. With the rapid advances in nanotechnology and materials science, various types of biomaterials have been developed to maximize therapeutic efficacy while minimizing side effects by increasing tumor antigenicity, reversing immunosuppressive microenvironment, amplifying antitumor immune response, and reducing extratumoral distribution of checkpoint inhibitors as well as enhancing their retention within target sites. In this review, we reviewed current design strategies for different types of biomaterials to augment ICB therapy effectively and then discussed present representative biomaterial-assisted immune modulation and targeted delivery of checkpoint inhibitors to boost ICB therapy. Current challenges and future development prospects for expanding the ICB with biomaterials were also summarized. We anticipate this review will be helpful for developing emerging biomaterials for ICB therapy and promoting the clinical application of ICB therapy.

Photon Upconversion in Small Molecules

Upconversion (UC) is a process that describes the emission of shorter-wavelength light compared to that of the excitation source. Thus, UC is also referred to as anti-Stokes emission because the excitation wavelength is longer than the emission wavelength. UC materials are used in many fields, from electronics to medicine. The objective of using UC in medical research is to synthesize upconversion nanoparticles (UCNPs) composed of a lanthanide core with a coating of adsorbed dye that will generate fluorescence after excitation with near-infrared light to illuminate deep tissue. Emission occurs in the visible and UV range, and excitation mainly in the near-infrared spectrum. UC is observed for lanthanide ions due to the arrangement of their energy levels resulting from f-f electronic transitions. Organic compounds and transition metal ions are also able to form the UC process. Biocompatible UCNPs are designed to absorb infrared light and emit visible light in the UC process. Fluorescent dyes are adsorbed to UCNPs and employed in PDT to achieve deeper tissue effects upon irradiation with infrared light. Fluorescent UCNPs afford selectivity as they may be activated only by illumination of an area of diseased tissue, such as a tumor, with infrared light and are by themselves atoxic in the absence of infrared light. UCNP constructs can be monitored as to their location in the body and uptake by cancer cells, aiding in evaluation of exact doses required to treat the targeted cancer. In this paper, we review current research in UC studies and UCNP development.

Effects of polyallylamine-coated nanoparticles on the optical and photochemical properties of rose bengal

BACKGROUND

Inasmuch as optical and photochemical properties of a photosensitizer can be modified upon association with the nanoparticle (NP), we wondered whether the effectiveness of phototherapeutic rose bengal (RB) was affected upon tethering to the sodium lanthanide fluoride NP with an outer polyallylamine (PAH) coat.

METHODS

RB molecules were electrostatically bound to the NaYF 4 :Gd 3+ :Nd 3+ NPs with inner silica and outer PAH coats. The products were analyzed for their size, shape and zeta potential using transmission electron microscopy and dynamic light scattering instrument. Ultraviolet-visible absorption spectrometry and fluorescence spectrometry were used to examine the spectral properties. Photodynamic effect in terms of singlet oxygen generation was quantitatively determined using the indicator 1,3-diphenylisobenzofuran (DPBF). Photocytotoxicity mediated by NP-bound RB was tested using A549 cells (Student's t test was used for statistical evaluation).

RESULTS

NP-bound RB had the major absorbance peak at 561 nm, in comparison with 549 nm for free RB, accompanied with a significant decrease in absorptivity. The molar extinction coefficient becomes 36 000 M -1 cm -1 , only ~35% of that for free RB. Fluorescence spectral analyses showed a paradoxical decrease in the emission with higher NP concentrations even at very low dilutions. Most importantly, the association of RB with these NPs drastically increased its singlet oxygen production upon irradiation. The interaction of RB with PAH coat could partly account for this enhancement, given our finding that PAH in solution also caused a drastic rise in DPBF reactivity by free RB. These NPs exhibited strong photocytotoxic effects, and their promise in photodynamic therapy was addressed.

CONCLUSION

Our findings provide evidence that the PAH coat plays a key role in enhanced biological activities of RB delivered via NPs, including the increase in singlet oxygen production and photocytotoxic effects.

Functionalized Fluorescent Nanodiamonds for Simultaneous Drug Delivery and Quantum Sensing in HeLa Cells

Here, we present multifunctional fluorescent nanodiamonds (FNDs) for simultaneous drug delivery and free radical detection. For this purpose, we modified FNDs containing nitrogen vacancy (NV) centers with a diazoxide derivative. We found that our particles enter cells more easily and are able to deliver this cancer drug into HeLa cells. The particles were characterized by infrared spectroscopy, dynamic light scattering, and secondary electron microscopy. Compared to the free drug, we observe a sustained release over 72 h rather than 12 h for the free drug. Apart from releasing the drug, with these particles, we can measure the drug's effect on free radical generation directly. This has the advantage that the response is measured locally, where the drug is released. These FNDs change their optical properties based on their magnetic surrounding. More specifically, we make use of a technique called relaxometry to detect spin noise from the free radical at the nanoscale with subcellular resolution. We further compared the results from our new technique with a conventional fluorescence assay for the detection of reactive oxygen species. This provides a new method to investigate the relationship between drug release and the response by the cell via radical formation or inhibition.

Controllable synthesis of layered black bismuth oxidechloride nanosheets and their applications in internal tumor ablation

The recently emerging bismuth oxyhalide (BiOX) nanomaterials are promising indirect band gap photosensitizer for ultraviolet (UV) light triggered phototherapy due to their unique layered nanosheet structure. However, the low absorption and poor photothermal conversion efficiency have always impeded their further applications in cancer clinical therapy. Herein, BiOCl rich in oxygen vacancies has been reported to have full spectrum absorption properties, making it possible to achieve photothermal property under near-infrared (NIR) laser. Under 808 nm irradiation, the photothermal conversion efficiency of black BiOCl nanosheets (BBNs) is up to 40%. BBNs@PEG can effectively clear primary subcutaneous tumors and prevent recurrence, achieving good synergistic treatment effect. These results not only broke the limitation of ultraviolet on the BiOCl material and provided a good template for other semiconductor materials, also represent a promising approach to fabricate BBN@PEG a novel, potent and multi-functional theranostic platform for precise PTT and prognostic evaluation.

Nanoarchitectured prototypes of mesoporous silica nanoparticles for innovative biomedical applications

Despite exceptional morphological and physicochemical attributes, mesoporous silica nanoparticles (MSNs) are often employed as carriers or vectors. Moreover, these conventional MSNs often suffer from various limitations in biomedicine, such as reduced drug encapsulation efficacy, deprived compatibility, and poor degradability, resulting in poor therapeutic outcomes. To address these limitations, several modifications have been corroborated to fabricating hierarchically-engineered MSNs in terms of tuning the pore sizes, modifying the surfaces, and engineering of siliceous networks. Interestingly, the further advancements of engineered MSNs lead to the generation of highly complex and nature-mimicking structures, such as Janus-type, multi-podal, and flower-like architectures, as well as streamlined tadpole-like nanomotors. In this review, we present explicit discussions relevant to these advanced hierarchical architectures in different fields of biomedicine, including drug delivery, bioimaging, tissue engineering, and miscellaneous applications, such as photoluminescence, artificial enzymes, peptide enrichment, DNA detection, and biosensing, among others. Initially, we give a brief overview of diverse, innovative stimuli-responsive (pH, light, ultrasound, and thermos)- and targeted drug delivery strategies, along with discussions on recent advancements in cancer immune therapy and applicability of advanced MSNs in other ailments related to cardiac, vascular, and nervous systems, as well as diabetes. Then, we provide initiatives taken so far in clinical translation of various silica-based materials and their scope towards clinical translation. Finally, we summarize the review with interesting perspectives on lessons learned in exploring the biomedical applications of advanced MSNs and further requirements to be explored.

Synthesis of Noble Metal M@YSiO2 Yolk-Shell Nanoparticles with Thin Organic/Inorganic Hybrid Outer Shells via an Aqueous Medium Phase

A simple method is proposed for the synthesis of noble metal M@YSiO₂ (M = Au, Pd, Ag) yolk-shell nanoparticles. The effects of synthesis conditions on the preparation of yolk-shell nanoparticles were discussed in detail. According to the different corrosion resistances between inorganic silica and organosilicone in a selective etching solution, yolk-shell nanoparticles with large cavity and thin shell were prepared using the same aqueous medium in a step-by-step synthesis process. Different from traditional methods, this method is facile and efficient because the main synthesis process is carried out in an aqueous phase. This extended method may benefit the synthesis and application of other nanomaterials with a similar yolk-shell structure.

Research advances in integrated theranostic probes for tumor fluorescence visualization and treatment

At present, cancer is obviously a major threat to human health worldwide. Accurate diagnosis and treatment are in great demand and have become an effective method to alleviate the development of cancer and improve the survival rate of patients. A large number of theranostic probes that combine diagnosis and treatment methods have been developed as promising tools for tumor precision medicine. Among them, fluorescent theranostic probes have developed rapidly in the frontier research field of precision medicine with their real time, low toxicity, and high-resolution merit. Therefore, this review focuses on recent advances in the development of fluorescent theranostic probes, as well as their applications for cancer diagnosis and treatment. Initially, small-molecule fluorescent theranostic probes mainly including tumor microenvironment-responsive fluorescent prodrugs and phototherapeutic probes were introduced. Subsequently, nanocomposite probes are expounded based on four types of nano-fluorescent particles combining different therapies (chemotherapy, photothermal therapy, photodynamic therapy, gene therapy, etc.). Then, the capsule-type "all in one" probes, which occupy an important position in theranostic probes, are summarized according to the surface carrier type. This review aims to present a comprehensive guide for researchers in the field of tumor-related theranostic probe design and development.

Oxygen self-enriched single-component "black carbon nitride" for near-infrared phototheranostics

Single component agent-based near-infrared phototheranostics has captivated researchers in cancer treatment over recent decades. However, the current single-component agents rarely alleviate the hypoxic microenvironment in tumor cells, which severely limits the development of photodynamic therapy. Here, we report a new phototheranostic agent, single-component black graphite carbon nitride nanoparticles (named CN-B NPs), synthesized through thermal copolymerization. Compared with unmodified graphitic carbon nitride (g-C3N4), the absorption of CN-B NPs in the near-infrared region was enhanced. Through in vitro and in vivo studies, we demonstrated that CN-B NPs can be used as a near-infrared phototheranostic agent in both normoxia and hypoxia, simultaneously allowing infrared thermal/photoacoustic imaging and photodynamic/photothermal co-therapy, thereby resulting in remarkable inhibition of tumor growth. This approach could provide a new method to achieve multimodal phototheranostics using a single-component material.

Versatile Yolk-Shell Encapsulation: Catalytic, Photothermal, and Sensing Demonstration

Here, a novel, versatile synthetic strategy to fabricate a yolk-shell structured material that can encapsulate virtually any functional noble metal or metal oxide nanocatalysts of any morphology in a free suspension fashion is reported. This strategy also enables encapsulation of more than one type of nanoparticle inside a single shell, including paramagnetic iron oxide used for magnetic separation. The mesoporous organosilica shell provides efficient mass transfer of small target molecules, while serving as a size exclusion barrier for larger interfering molecules. Major structural and functional advantages of this material design are demonstrated by performing three proof-of-concept applications. First, effective encapsulation of plasmonic gold nanospheres for localized photothermal heating and heat-driven reaction inside the shell is shown. Second, hydrogenation catalysis is demonstrated under spatial confinement driven by palladium nanocubes. Finally, the surface-enhanced Raman spectroscopic detection of model pollutant by gold nanorods is presented for highly sensitive environmental sensing with size exclusion.

Triple stimuli-responsive ZnO quantum dots-conjugated hollow mesoporous carbon nanoplatform for NIR-induced dual model antitumor therapy

Aiming at the inefficiency and toxicity in traditional antitumor therapy, a novel multifunctional nanoplatform was constructed based on hollow mesoporous carbon (HMC) to achieve triple stimuli response and dual model antitumor therapy via chemo-photothermal synergistic effect. HMC was used as an ideal nanovehicle with a high drug loading efficiency as well as a near-infrared (NIR) photothermal conversion agent for photothermal therapy. Acid-dissoluble, luminescent ZnO quantum dots (QDs) were used as the proper sealing agents for the mesopores of HMC, conjugated to HMC via disulfide linkage to prevent drug (doxorubicin, abbreviated as Dox) premature release from Dox/HMC-SS-ZnO. After cellular endocytosis, the Dox was released in a pH, GSH and NIR laser triple stimuli-responsive manner to realize accurate drug delivery. Moreover, the local hyperthermia effect induced by NIR irradiation could promote the drug release, enhance cell sensitivity to chemotherapeutic agents, and also directly kill cancer cells. As expected, Dox/HMC-SS-ZnO exhibited a high drug loading capacity of 43%, well response to triple stimuli and excellent photothermal conversion efficiency η of 29.7%. The therapeutic efficacy in 4T1 cells and multicellular tumor spheroids (MCTSs) demonstrated that Dox/HMC-SS-ZnO + NIR had satisfactory chemo-photothermal synergistic effect with a combination index (CI) of 0.532. The cell apoptosis rate of the combined treatment group was more than 95%. The biodistribution and pharmacodynamics studies showed its biosecurity to normal tissues and synergistic inhibition effect to tumor cells. These distinguished results indicated that the Dox/HMC-SS-ZnO nanoplatform is potential to realize efficient triple stimuli-responsive drug delivery and dual model chemo-photothermal synergistic antitumor therapy.

One-step synthesis of novel phosphorus nitride dots for two-photon imaging in living cells

Novel phosphorus nitride dots mainly consisting of N and P with strong fluorescence, excellent dispersibility and outstanding biocompatibility were prepared via a solvothermal method. The phosphorus nitride dots demonstrated great two-photon imaging capability in living cells under 800 nm excitation.

Photothermally controlled drug release system with high dose loading for synergistic chemo-photothermal therapy of multidrug resistance cancer

Chemotherapy is an important first-line strategy for tumor therapy in cancer treatment, but multidrug resistance (MDR) is a major problem that reduces the efficacy of chemotherapeutics. Herein, we report a novel photothermally controlled intelligent drug release system (AuNP@mSiO₂-DOX-FA) with a large amount of drugs loading for synergistic chemo-photothermal therapy of MDR in breast cancer. The nanoplatform utilized gold nanoparticles as a hyperthermia core, and large-mesoporous silica as a shell for doxorubicin (DOX) loading. Benefiting from the thick layer and large pore size, the encapsulation and loading efficiency were as high as 97.7% and 8.84%, respectively. Furthermore, under the trigger of 808 nm near infrared (NIR) light, the released DOX increased significantly at pH 5.0 and reached to 39.0% in 20 min, achieving a facile intelligent control of chemotherapy additional to the photothermal therapy. The viability of MCF-7/ADR cells could be efficiently reduced to 16.9%, demonstrating the proposed photothermally controlled system with synergistic chemo-photothermal therapy has great potential capability to overcome MDR in breast cancer.

Homologous Gold Nanoparticles and Nanoclusters Composites with Enhanced Surface Raman Scattering and Metal Fluorescence for Cancer Imaging

A large number of deaths from cancer can be attributed to the lack of effective early-stage diagnostic techniques. Thus, accurate and effective early diagnosis is a major research goal worldwide. With the unique phenomenon of localized surface plasmon resonance (LSPR), plasmonic nanomaterials have attracted considerable attention for applications in surface-enhanced Raman scattering (SERS) and metal-enhanced fluorescence (MEF). Both SERS and MEF are ultra-sensitive methods for the detection and identification of early tumor at molecular level. To combine the merits of the fast and accurate imaging of MEF and the stable and clear imaging of SERS, we propose a novel dual functional imaging nanoprobe based on gold nanoparticles and gold nanocluster composites (denoted AuNPC-RGD). The gold nanoparticles are used as LSPR substrates to realized enhancement of Raman or fluorescence signal, while the gold nanoclusters serve as a fluorophore for MEF imaging, and exhibit better biocompatibility and stability. Furthermore, target molecule of cyclic Arg-Gly-Asp (cRGD) is incorporated into the composite to improve delivery efficiency, selectivity and imaging accuracy. These integrated properties endow AuNPC-RGD composites with outstanding biocompatibility and excellent imaging abilities, which could be used to achieve accurate and effective diagnosis for early cancer.

Enriching Mn-Doped ZnSe Quantum Dots onto Mesoporous Silica Nanoparticles for Enhanced Fluorescence/Magnetic Resonance Imaging Dual-Modal Bio-Imaging

Multimodal imaging is more suitable for disease diagnosis because of its ability to provide more complementary and accurate information over single-mode imaging. Mn-doped quantum dots (QDs), especially Mn-doped ZnS (ZnSe) QDs, possess unique fluorescent and magnetic properties and are thus attractive for fluorescence/magnetic resonance imaging (MRI) dual-mode imaging. However, the optimal dopant (Mn²⁺) concentration for maximizing the fluorescence of QDs is relatively low for the MRI imaging. Herein, based on the large Stokes shift of Mn-doped ZnSe QDs, an enrichment strategy with mesoporous silica (MSN) loading was explored for constructing a highly luminescent/paramagnetism Mn-doped ZnSe QDs assembly (MSN@QDs) for improved MRI/optical dual-model imaging. After assembly, the loading density of QDs in MSNs was estimated to be 152 ± 12. Upon loading, the fluorescence of the MSN@QDs assembly was enriched along with QDs (enrichment factor of ∼143). Because of the large Stokes shift (∼200 nm), no appreciable concentration quenching was observed. Meanwhile, the T₁ MR contrast was also increased both in vitro and in vivo through improved local Mn²⁺ concentration, realizing MRI signal enrichment. In fluorescence imaging investigations, MSN@QDs showed better performance over both single QDs and equivalent numbers of MSN-free single QD. Therefore, this enrichment strategy allowed simultaneous signal enhancement of the two imaging modes of Mn-doped ZnSe QDs.

The Bioimaging Applications of Mesoporous Silica Nanoparticles

The unique features of Mesoporous Silica Nanoparticles (MSNs) provide a suitable platform to carry fluorescence dyes for various bioimaging applications. Several strategies have been developed to conjugate a variety of dyes either in the pores or on the surfaces of MSNs to form the fluorescence MSNs (FMSNs). In this chapter, we will discuss recent research progress and future development of FMSNs for living system imaging. We will first describe different strategies for the fabrications of FMSNs. Then, we will discuss the recent developments of cellular and intracellular imaging including self-probe for the interactions of FMSNs with the cells, receptor and organelle labeling, sensing and tracking of biological system, and monitoring the drug delivery and release processes. Moreover, we will include the applications of FMSNs as contrast agents for in vivo imaging. Finally, we will conclude and highlight the challenges and opportunities for MSNs in medical applications.

Triple Stimuli-Responsive Magnetic Hollow Porous Carbon-Based Nanodrug Delivery System for Magnetic Resonance Imaging-Guided Synergistic Photothermal/Chemotherapy of Cancer

The premature leakage of anticancer drugs during blood circulation may the damage immune system, normal cells, and tissues. Constructing targeted nanocarriers with pH, glutathione, and NIR triple-responsive property can effectively avoid the leakage of anticancer drugs before they arrive at the targeted site. In this paper, magnetic hollow porous carbon nanoparticles (MHPCNs) were successfully fabricated as nanocarrier. Poly(γ-glutamic acid) was used to cap the pores of MHPCNs. The photothermal conversion property of carbon and iron oxide (Fe₃O₄) nanomaterials was utilized to perform photothermal therapy to overcome multidrug-resistance produced by chemotherapy. The biodistribution of nanoparticles was investigated by magnetic resonance imaging. Experiments in vivo confirm the efficient accumulations of nanoparticles at tumor sites. Meanwhile, tumor growth was effectively inhibited via synergistic photothermal/chemotherapy with minimal side effects.

Advances in Multicompartment Mesoporous Silica Micro/Nanoparticles for Theranostic Applications

Mesoporous silica nanoparticles (MSNs) are promising functional nanomaterials for a variety of biomedical applications, such as bioimaging, drug/gene delivery, and cancer therapy. This is due to their low density, low toxicity, high biocompatibility, large specific surface areas, and excellent thermal and mechanical stability. The past decade has seen rapid advances in the development of MSNs with multiple compartments. These include hierarchical porous structures and core-shell, yolk-shell, and Janus structured particles for efficient diagnosis and therapeutic applications. We review advances in this area, covering the categories of multicompartment MSNs and their synthesis methods, with an emphasis on hierarchical structures and the incorporation of multiple functions. We classify multicompartment mesoporous silica micro/nanostructures, ranging from core-shell and yolk-shell structures to Janus and raspberry-like nanoparticles, and discuss their synthesis methods. We review applications of these multicompartment MSNs, including bioimaging, targeted drug/gene delivery, chemotherapy, phototherapy, and in vitro diagnostics. We also highlight the latest trends and new opportunities.

Interconversion between KSc2F7:Yb/Er and K2NaScF6:Yb/Er nanocrystals: the role of chemistry

Interconversion between nanocrystals of orthorhombic KSc₂F₇:Yb/Er and cubic K₂NaScF₆:Yb/Er was realized by adjusting the according chemical reaction conditions.

A "protective umbrella" nanoplatform for loading ICG and multi-modal imaging-guided phototherapy

In order to prevent the aggregation of ICG and enhance its stability, a novel nanoplatform (TiO₂:Yb,Ho,F-β-CD@ICG/HA) was designed for NIR-induced phototherapy along with multi-mode imaging(UCL/MRI/Flu). In this nanosysytem: TiO₂:Yb,Ho,F was used as upconversion materials and applied in vivo for the first time; β-CD acted as a "protective umbrella" to load separated ICG and avoid the low phototherapy efficiency because of its aggregation; HA was the capping agent of β-CD to prevent ICG unexpected leaking and a target to recognize CD44 receptor. The nanosystem exhibited excellent size (~200 nm) and photo- and thermal-stability, preferable reactive oxygen yield and temperature response (50.4 °C) under 808 nm laser. It could efficiently target and suppress tumor growth. The imaging ability (UCL/MRI) of TiO₂:Yb,Ho,F could facilitate diagnosis of the tumor, especially for deep tissues. Altogether, our work successfully improved the phototherapy efficacy through incorporating the ICG into the cavity of β-CD and applied TiO₂:Yb,Ho,F for upconversion imaging in vivo.

Upconversion processes: versatile biological applications and biosafety

Lanthanide-doped photon upconverting nanomaterials are evolving as a new class of imaging contrast agents, offering highly promising prospects in the area of biomedical applications. Owing to their ability to convert long-wavelength near-infrared excitation radiation into shorter-wavelength emissions, these nanomaterials are well suited to yield properties of low imaging background, large anti-Stokes shift, along with high optical penetration depth of NIR light for deep tissue optical imaging or light-activated drug release and therapy. Such materials have potential for significant advantages in analytical applications compared to molecular fluorophores and quantum dots. The use of IR radiation as an excitation source diminishes autofluorescence and scattering of excitation radiation, which leads to a reduction of background in optical experiments. The upconverting nanocrystals show exceptional photostability and are constituted of materials that are not significantly toxic to biological organisms. Excitation at long wavelengths also minimizes damage to biological materials. In this detailed review, various mechanisms operating for the upconversion process, and methods that are utilized to synthesize and decorate upconverting nanoparticles are investigated to elucidate by what means absorption and emission can be tuned. Up-to-date reports concerning cellular internalization, biodistribution, excretion, cytotoxicity and in vivo toxic effects of UCNPs are discussed. Specifically, studies which assessed the relationship between the chemical and physical properties of UCNPs and their biodistribution, excretion, and toxic effects are reviewed in detail. Finally, we also deliberate the challenges of guaranteeing the biosafety of UCNPs in vivo.

Black TiO2 based core-shell nanocomposites as doxorubicin carriers for thermal imaging guided synergistic therapy of breast cancer

TiO₂ nanomaterials have been widely used for anticancer drug carriers and UV/980 nm NIR triggered cancer synergistic platforms. However, traditional pure TiO₂ nanocarriers encounter some serious drawbacks, such as low drug loading ability, limited tissue penetration of UV light, and heating effect of 980 nm NIR on normal tissue, which obstruct their further application in cancer treatment. To overcome those challenges, novel mesoporous silica (mSiO₂) coated black TiO₂ core-shell nanocomposites are designed and constructed as doxorubicin carriers for 808 nm NIR triggered thermal imaging guided photothermal therapy combined chemotherapy of breast cancer. Properties of the nanocomposites such as micro-morphology, size, drug loading ability and release, targeting performance, and therapy efficiency in vitro and in vivo were evaluated. The results indicated the core-shell nanocomposites with dramatically increased loading ability were pH-responsive/NIR-accelerated doxorubicin release nanocarriers and showed synergistic breast cancer treatment in vitro and in vivo. This study verifies that the newly prepared mSiO₂ coated black TiO₂ core-shell nanocarriers can overcome the limitations of traditional TiO₂ nanocarriers and thus improve and broaden usage of TiO₂ nanoparticles in nanomedicine.

Gadolinium-based nanoscale MRI contrast agents for tumor imaging

Gadolinium-based nanoscale magnetic resonance imaging (MRI) contrast agents (CAs) have gained significant momentum as a promising nanoplatform for detecting tumor tissue in medical diagnosis, due to their favorable capability of enhancing the longitudinal relaxivity (r₁) of individual gadolinium ions, delivering to the region of interest a large number of gadolinium ions, and incorporating different functionalities. This mini-review highlights the latest developments and applications, and simultaneously gives some perspectives for their future development.

Tuning the morphology, luminescence and magnetic properties of hexagonal-phase NaGdF4: Yb, Er nanocrystals via altering the addition sequence of the precursors

Hexagonal-phase NaGdF₄: Yb, Er upconversion nanocrystals (UCNCs) with tunable morphology and properties were successfully prepared via a thermal decomposition method. The influences of the adding sequence of the precursors on the morphology, chemical composition, luminescence and magnetic properties were investigated by transmission electron microscopy (TEM), inductively coupled plasma-atomic emission spectrometry (ICP-AES), upconversion (UC) spectroscopy, and a vibrating sample magnetometer (VSM). It was found that the resulting nanocrystals, with different sizes ranging from 24 to 224 nm, are in the shape of spheres,  hexagonal plates and flakes; moreover, the composition percentage of Yb³⁺-Er³⁺ and Gd³⁺ ions was found to vary in a regular pattern with the adding sequence. Furthermore, the intensity ratios of emission colors (f _g/r, f _g/p), and the magnetic mass susceptibility of hexagonal-phase NaGdF₄: Yb, Er nanocrystals change along with the composition of the nanocrystals. A positive correlation between the susceptibility and f _g/r of NaGdF₄: Yb, Er was proposed. The decomposition processes of the precursors were investigated by a thermogravimetric (TG) analyzer. The result indicated that the decomposition of the resolved lanthanide trifluoroacetate is greatly different from lanthanide trifluoroacetate powder. It is of tremendous help to recognize the decomposition process of the precursors and to understand the related reaction mechanism.

Current Advances in Lanthanide-Doped Upconversion Nanostructures for Detection and Bioapplication

Along with the development of science and technology, lanthanide-doped upconversion nanostructures as a new type of materials have taken their place in the field of nanomaterials. Upconversion luminescence is a nonlinear optical phenomenon, which absorbs two or more photons and emits one photon. Compared with traditional luminescence materials, upconversion nanostructures have many advantages, such as weak background interference, long lifetime, low excitation energy, and strong tissue penetration. These interesting nanostructures can be applied in anticounterfeit, solar cell, detection, bioimaging, therapy, and so on. This review is focused on the current advances in lanthanide-doped upconversion nanostructures, covering not only basic luminescence mechanism, synthesis, and modification methods but also the design and fabrication of upconversion nanostructures, like core-shell nanoparticles or nanocomposites. At last, this review emphasizes the application of upconversion nanostructure in detection and bioimaging and therapy. Learning more about the advances of upconversion nanostructures can help us better exploit their excellent performance and use them in practice.

Probing the Interior Crystal Quality in the Development of More Efficient and Smaller Upconversion Nanoparticles

Optical biomedical imaging using luminescent nanoparticles as contrast agents prefers small size, as they can be used at high dosages and efficiently cleared from body. Reducing nanoparticle size is critical for the stability and specificity for the fluorescence nanoparticles probes for in vitro diagnostics and subcellular imaging. The development of smaller and brighter upconversion nanoparticles (UCNPs) is accordingly a goal for complex imaging in bioenvironments. At present, however, small UCNPs are reported to exhibit less emission intensity due to increased surface deactivation and decreased number of dopants. Here we show that smaller and more efficient UCNPs can be made by improving the interior crystal quality via controlling heating rate during synthesis. We further developed a unique quantitative method for optical characterizations on the single UCNPs with varied sizes and the corresponding shell passivated UCNPs, confirming that the internal crystal quality dominates the relative emission efficiency of the UCNPs.

A Multifunctional PB@mSiO2-PEG/DOX Nanoplatform for Combined Photothermal-Chemotherapy of Tumor

In this work, we design mesoporous silica-coated Prussian blue nanocubes with PEGyltation to construct multifunctional PB@mSiO2-PEG nanocubes. The PB@mSiO2-PEG nanocubes have good biocompatibility, excellent photothermal transformation capacity, in vivo magnetic resonance and photoacoustic imaging ability. After loading antitumor drug doxorubicin (DOX) in the PB@mSiO2-PEG nanocubes, the constructured PB@mSiO2-PEG/DOX nanoplatforms show an excellent pH-responsive drug release character within 48 h, namely, an ultralow cumulative drug release amount of 3.1% at pH 7.4 and a high release amount of 46.6% at pH 5.0. Upon near-infrared laser irradiation, the PB@mSiO2-PEG/DOX nanoplatforms show an enhanced synergistic photothermal and chemical therapeutic efficacy for breast cancer than solo photothermal therapy or chemotherapy.

Nd3+ sensitized dumbbell-like upconversion nanoparticles for photodynamic therapy application

Dumbbell-like structured NaYF₄:Yb/Er@NaNdF₄:Yb upconversion nanoparticles are fabricated and have potential in photodynamic therapy (PDT).

NIR photoresponsive drug delivery and synergistic chemo-photothermal therapy by monodispersed-MoS2-nanosheets wrapped periodic mesoporous organosilicas

NIR photoresponsive PMO–Dox@MoS₂–PEG nanoplatforms were constructed for synergistic chemo-photothermal therapy.