Bioresponsive and near infrared photon co-enhanced cancer theranostic based on upconversion nanocapsules

Deformable nanocarriers for enhanced drug delivery and cancer therapy

Recently, the field of nanomedicine has witnessed substantial advancements in the development of nanocarriers for targeted drug delivery, emerges as promising platforms to enhance therapeutic efficacy and minimize adverse effects associated with conventional chemotherapy. Notably, deformable nanocarriers have garnered considerable attention due to their unique capabilities of size changeable, tumor-specific aggregation, stimuli-triggered disintegration, and morphological transformations. These deformable nanocarriers present significant opportunities for revolutionizing drug delivery strategies, by responding to specific stimuli or environmental cues, enabling achieved various functions at the tumor site, including size-shrinkage nanocarriers enhance drug penetration, aggregative nanocarriers enhance retention effect, disintegrating nanocarriers enable controlled drug release, and shape-changing nanocarriers improve cellular uptake, allowing for personalized treatment approaches and combination therapies. This review provides an overview of recent developments and applications of deformable nanocarriers for enhancing tumor therapy, underscores the diverse design strategies employed to create deformable nanocarriers and elucidates their remarkable potential in targeted tumor therapy.

Targeting the organelle for radiosensitization in cancer radiotherapy

Radiotherapy is a well-established cytotoxic therapy for local solid cancers, utilizing high-energy ionizing radiation to destroy cancer cells. However, this method has several limitations, including low radiation energy deposition, severe damage to surrounding normal cells, and high tumor resistance to radiation. Among various radiotherapy methods, boron neutron capture therapy (BNCT) has emerged as a principal approach to improve the therapeutic ratio of malignancies and reduce lethality to surrounding normal tissue, but it remains deficient in terms of insufficient boron accumulation as well as short retention time, which limits the curative effect. Recently, a series of radiosensitizers that can selectively accumulate in specific organelles of cancer cells have been developed to precisely target radiotherapy, thereby reducing side effects of normal tissue damage, overcoming radioresistance, and improving radiosensitivity. In this review, we mainly focus on the field of nanomedicine-based cancer radiotherapy and discuss the organelle-targeted radiosensitizers, specifically including nucleus, mitochondria, endoplasmic reticulum and lysosomes. Furthermore, the organelle-targeted boron carriers used in BNCT are particularly presented. Through demonstrating recent developments in organelle-targeted radiosensitization, we hope to provide insight into the design of organelle-targeted radiosensitizers for clinical cancer treatment.

Hydrogel design to overcome thermal resistance and ROS detoxification in photothermal and photodynamic therapy of cancer

Responsive heat resistance (by heat shock protein upregulation) and spontaneous reactive oxygen species (ROS) detoxification have been regarded as the major obstacles for photothermal/photodynamic therapy of cancer. To overcome the thermal resistance and improve ROS susceptibility in breast cancer therapy, Au ion-crosslinked hydrogels including indocyanine green (ICG) and polyphenol are devised. Au ion has been introduced for gel crosslinking (by catechol-Au3+ coordination), cellular glutathione depletion, and O2 production from cellular H2O2. ICG can generate singlet oxygen from O2 (for photodynamic therapy) and induce hyperthermia (for photothermal therapy) under the near-infrared laser exposure. (-)-Epigallocatechin gallate downregulates heat shock protein to overcome heat resistance during hyperthermia and exerts multiple anticancer functions in spite of its ironical antioxidant features. Those molecules are concinnously engaged in the hydrogel structure to offer fast gel transformation, syringe injection, self-restoration, and rheological tuning for augmented photo/chemotherapy of cancer. Intratumoral injection of multifunctional hydrogel efficiently suppressed the growth of primary breast cancer and completely eliminated the residual tumor mass. Proposed hydrogel system can be applied to tumor size reduction prior to surgery of breast cancer and the complete remission after its surgery.

Stimuli-Responsive Nanoradiosensitizers for Enhanced Cancer Radiotherapy

Radiotherapy (RT) has been a classical therapeutic method of cancer for several decades. It attracts tremendous attention for the precise and efficient treatment of local tumors with stimuli-responsive nanomaterials, which enhance RT. However, there are few systematic reviews summarizing the newly emerging stimuli-responsive mechanisms and strategies used for tumor radio-sensitization. Hence, this review provides a comprehensive overview of recently reported studies on stimuli-responsive nanomaterials for radio-sensitization. It includes four different approaches for sensitized RT, namely endogenous response, exogenous response, dual stimuli-response, and multi stimuli-response. Endogenous response involves various stimuli such as pH, hypoxia, GSH, and reactive oxygen species (ROS), and enzymes. On the other hand, exogenous response encompasses X-ray, light, and ultrasound. Dual stimuli-response combines pH/enzyme, pH/ultrasound, and ROS/light. Lastly, multi stimuli-response involves the combination of pH/ROS/GSH and X-ray/ROS/GSH. By elaborating on these responsive mechanisms and applying them to clinical RT diagnosis and treatment, these methods can enhance radiosensitive efficiency and minimize damage to surrounding normal tissues. Finally, this review discusses the additional challenges and perspectives related to stimuli-responsive nanomaterials for tumor radio-sensitization.

Ultrasound mediated gold nanoclusters-capped gas vesicles for enhanced fluorescence imaging

The intercellular tight junction inhibits tumor imaging efficiency of nanomaterials, and enhanced cellular drug delivery with efficient detection is an important tool for tumor diagnosis. Herein, we fabricate fluorescence gold nanoclusters (Au NCs) decorated gas vesicles (GV-Au) for ultrasound (US)-mediated enhanced cellular delivery and imaging, in which GVs are living cell derived protein bubbles. GV-Au is rod-shaped sack-like structure around 230 nm, and displays improved stability and fluorescence ability compared with free Au NCs. Flow cytometry assay confirms the intracellular localization of Au NCs and GV-Au with a respective 2.20-fold enhanced cellular uptake post US treatment. Confocal images reveal the efficient cellular uptake of GV-Au under US impact, indicating that GV-Au is suitable for cellular and in vivo fluorescence imaging. Our strategy provides a new idea for efficient fluorescence imaging by penetrating cell membranes at the presence of US treatment.

Physically stimulus-responsive nanoparticles for therapy and diagnosis

Nanoparticles offer numerous advantages in various fields of science, particularly in medicine. Over recent years, the use of nanoparticles in disease diagnosis and treatments has increased dramatically by the development of stimuli-responsive nano-systems, which can respond to internal or external stimuli. In the last 10 years, many preclinical studies were performed on physically triggered nano-systems to develop and optimize stable, precise, and selective therapeutic or diagnostic agents. In this regard, the systems must meet the requirements of efficacy, toxicity, pharmacokinetics, and safety before clinical investigation. Several undesired aspects need to be addressed to successfully translate these physical stimuli-responsive nano-systems, as biomaterials, into clinical practice. These have to be commonly taken into account when developing physically triggered systems; thus, also applicable for nano-systems based on nanomaterials. This review focuses on physically triggered nano-systems (PTNSs), with diagnostic or therapeutic and theranostic applications. Several types of physically triggered nano-systems based on polymeric micelles and hydrogels, mesoporous silica, and magnets are reviewed and discussed in various aspects.

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.

Construction of NaYF4 Library for Morphology-Controlled Multimodality Applications

Morphology and size of the nanoparticles are highly related to the properties; establishing a library to summarize the relationship between the morphology/size and property is very helpful for associated applications. However, the NaYF₄ library and thus the correlation between the morphology and property are still absent. Here NaYF₄ library is presented and their morphologies and structures are illustrated at atomic scale for the first time. How about the crystal formation affects the morphology is further used to guide the property. Through rational doping, upconversion luminescence, magnetic resonance (MR) and computed tomography are investigated with the nanoprisms, nanoflowers, and nanoplates as models to reveal the effect of the size and morphology. The difference of the properties provides strong evidence on the importance of the library. In particular, the "imperfect structure" of nanoflower is observed on atomic scale and enhances the MR response. The different upconversion intensity ratio for the emissions at 475 and 693 nm is observed from doped NaYF₄ with different morphology. Thus, controllable fabrication of NaYF₄ with desired morphology is indispensable to achieve the optimal properties as the guidance on how to choose matrix from the library to meet the specific applications.

Dual-Crosslinked Dynamic Hydrogel Incorporating {Mo154 } with pH and NIR Responsiveness for Chemo-Photothermal Therapy

Polyoxometalates are an emerging class of molecular clusters, with well-defined structures and chemical compositions that are produced through simple, low-cost, and highly reproducible methods. In particular, the wheel-shaped cluster {Mo154 } is a promising photothermal agent due to its intervalence charge transfer transitions. However, its toxicity hinders its systemic administration, being the development of a localized delivery system still incipient. Herein, an injectable and self-healing hydrogel of easy preparation and administration is developed, incorporating both {Mo154 } and doxorubicin for synergistic photothermal and chemotherapy applications. The hydrogel is composed of benzylaldehyde functionalized polyethylene glycol, poly(N-isopropylacrylamide) functionalized chitosan and {Mo154 }. The gelation occurs within 60 s at room temperature, and the dual crosslinking by Schiff base and electrostatic interactions generates a dynamic network, which enables self-healing after injection. Moreover, the hydrogel delivers chemotherapeutic drugs, with a release triggered by dual near infra-red (NIR) radiation and pH changes. This stimuli-responsive release system along with the photothermal conversion ability of the hydrogel allows the simultaneous combination of photothermal and chemotherapy. This synergic system efficiently ablates the cancer tumor in vivo with no systemic toxicity. Overall, this work paves the way for the development of novel {Mo154 }-based systems, incorporated in self-healing and injectable hydrogels for dual chemo-photothermal therapy.

Dual-Targeting Peptide-Guided Approach for Precision Delivery and Cancer Monitoring by Using a Safe Upconversion Nanoplatform

Using Epstein-Barr virus (EBV)-induced cancer cells and HeLa cells as a comparative study model, a novel and safe dual-EBV-oncoproteins-targeting pH-responsive peptide engineering, coating, and guiding approach to achieve precision targeting and treatment strategy against EBV-associated cancers is introduced. Individual functional peptide sequences that specifically bind to two overexpressed EBV-specific oncoproteins, EBNA1 (a latent cellular protein) and LMP1 (a transmembrane protein), are engineered in three different ways and incorporated with a pH-sensitive tumor microenvironment (TME)-cleavable linker onto the upconversion nanoparticles (UCNP) NaGdF4:Yb3+, Er3+@NaGdF4 (UCNP-P n , n = 5, 6, and 7). A synergistic combination of the transmembrane LMP1 targeting ability and the pH responsiveness of UCNP-P n is found to give specific cancer differentiation with higher cellular uptake and accumulation in EBV-infected cells, thus a lower dose is needed and the side effects and health risks from treatment would be greatly reduced. It also gives responsive UC signal enhancement upon targeted dual-protein binding and shows efficacious EBV cancer inhibition in vitro and in vivo. This is the first example of simultaneous imaging and inhibition of two EBV latent proteins, and serves as a blueprint for next-generation peptide-guided precision delivery nanosystem for the safe monitoring and treatment against one specific cancer.

A nanoprobe for fluorescent monitoring of microRNA and targeted delivery of drugs

Multifunctional nano-materials that can be used to monitor the expression of specific biomarkers and serve as vehicles for controlled drug delivery are highly desirable. Herein, we report a new DNA-hybrid-gated core–shell upconversion nanoprobe (UCNP@MOF/DOX) for fluorescence analysis of microRNA-21 (miR-21), which also triggers the release of drug loaded in the probes for on-demand anti-cancer treatment. The nanoprobe is built on the merits of ultraviolet-visible light of upconversion nanoparticles (UCNPs) excited by near-infrared (NIR) and extraordinary loading capability of metal–organic frameworks (MOFs) for drug delivery. Controlled release of doxorubicin (DOX) from the nanoprobe by miR-21 underwent the following two-stage kinetics: a fast release stage specifically triggered by miR-21 and proportional to miR-21 concentration and a slow stage observed in both gated and ungated nanoprobes due to collapse of the UIO-66-NH₂ coatings via ligand exchange with phosphates. In addition, the nanoprobe showed good selectivity, a linear response towards miR-21 ranging from 4 nM to 500 nM, and a limit of detection in 4 nM, which precluded unintended payload leakage due to low-abundance endogenous miR-21 expression in normal cells. Moreover, based on a dual-targeted delivery system constituted by AS1411-mediated recognition and responsive release of DOX, a specific cytotoxic efficacy was observed in MCF-7 cells. The present work provides a smart and robust nanoprobe for real-time detection of miRNA and dual-responsive drug delivery in tumor cells.

A DNA-hybrid-gated core–shell upconversion nanoprobe is prepared for both fluorescent monitoring of miR-21 and on-demand delivery of DOX. It showed good selectivity towards miR-21 and demonstrated specific cytotoxic efficacy towards MCF-7 cells.

A novel theranostic nanoplatform for imaging-guided chemo-photothermal therapy in oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is highly malignant and invasive, and current treatments are limited due to serious side effects and unsatisfactory outcomes. Here, we reported the terbium ion-doped hydroxyapatite (HATb) nanoparticle as a luminescent probe to encapsulate both the near-infrared (NIR) photothermal agent polydopamine (PDA) and anticancer doxorubicin (DOX) for imaging-guided chemo-photothermal therapy. The morphology, crystal structure, fluorescence, and composition of HATb-PDA-DOX were characterized. HATb-PDA showed a high DOX loading capacity. A theranostic nanoplatform showed pH/NIR responsive release properties and better antitumor outcomes in OSCC cells than monomodal chemotherapy or photothermal therapy, while keeping side effects at a minimum. Also, the luminescence signal was confirmed to be tracked and the increase of the red/green (R/G) ratio caused by the DOX release could be used to monitor the DOX release content. Furthermore, HATb-PDA-DOX plus NIR treatment synergistically promoted in vitro cell death through the overproduction of reactive oxygen species (ROS), cell cycle arrest, and increased cell apoptosis. Overall, this work presents an innovative strategy in designing a multifunctional nano-system for imaging-guided cancer treatment.

Stimuli-Responsive Nanomaterials for Smart Tumor-Specific Phototherapeutics

Phototherapy, a type of photoresponsive regulation of biological activities, together with additional stimuli-responsive features, offers significant potential for enhancing the precision and efficacy of cancer treatments. To achieve tumor-specific therapeutics, numerous studies have focused on the development of smart phototherapeutic nanomaterials (PNMs) that can respond to endogenous pathological characteristics (e. g., mild acidity, the overproduction of glutathione, the overproduction of hydrogen peroxide, the overexpression of specific surface receptors, etc.) present in the tumor and/or exogenous stimuli. Such responsiveness can effectively improve the physicochemical properties, cellular uptake, tumor-targeting performance, and pharmacokinetic profile of PNMs. Herein, we will systematically discuss recent advances in this field. Moreover, potential challenges and future directions in the development of stimuli-responsive PNMs are also presented to support the development of this emerging cutting-edge research area.

Nanotheranostics for Cancer Therapy and Detection: State of the Art

Nanotheranostics, an approach of combining both diagnosis and therapy, is one of the latest advances in cancer therapy particularly. Nanocarriers designed and derived from inorganic materials such as like gold nanoparticles, silica nanoparticles, magnetic nanoparticles and carbon nanotubes have been explored for tremendous applications in this area. Similarly, nanoparticles composed of some organic material alone or in combination with inorganic nano-cargos have been developed pre-clinically and possess excellent features desired. Photothermal therapy, MRI, simultaneous imaging and delivery, and combination chemotherapy with a diagnosis are a few of the known methods exploring cancer therapy and detection at organ/tissue/molecular/sub-cellular level. This review comprises an overview of the recent reports meant for nano theranostics purposes. Targeted cancer nanotheranostics have been included for understating tumor micro-environment or cell-specific targeting approach employed. A brief account of various strategies is also included for the readers highlighting the mechanism of cancer therapy.

Perspectives and advancements in the design of nanomaterials for targeted cancer theranostics

Cancer continues to be one of the most challenging diseases to be treated and is one of the leading causes of deaths around the globe. Cancers account for 13% of all deaths each year, with cancer-related mortality expected to rise to 13.1 million by the year 2030. Although, we now have a large library of chemotherapeutic agents, the problem of non-selectivity remains the biggest drawback, as these substances are toxic not only to cancerous cells, but also to other healthy cells in the body. The limitations with chemotherapy and radiation have led to the discovery and development of novel strategies for safe and effective treatment strategies to manage the menace of cancer. Researchers have long justified and have shed light on the emergence of nanotechnology as a potential area for cancer therapy and diagnostics, whereby, nanomaterials are used primarily as nanocarriers or as delivery agents for anticancer drugs due to their tumor targeting properties. Furthermore, nanocarriers loaded with chemotherapeutic agents also overcome biological barriers such as renal and hepatic clearances, thus improving therapeutic efficacy with lowered morbidity. Theranostics, which is the combination of rationally designed nanomaterials with cancer-targeting moieties, along with protective polymers and imaging agents has become one of the core keywords in cancer research. In this review, we have highlighted the potential of various nanomaterials for their application in cancer therapy and imaging, including their current state and clinical prospects. Theranostics has successfully paved a path to a new era of drug design and development, in which nanomaterials and imaging contribute to a large variety of cancer therapies and provide a promising future in the effective management of various cancers. However, in order to meet the therapeutic needs, theranostic nanomaterials must be designed in such a way, that take into account the pharmacokinetic and pharmacodynamics properties of the drug for the development of effective carcinogenic therapy.

Enzyme-Responsive Nanoparticles for Anti-tumor Drug Delivery

The past few decades have seen great progress in the exploration of nanoparticles (NPs) as novel tools for cancer treatments and diagnosis. Practical and reliable application of nanoparticle-based technology in clinical transformation remains nevertheless an ongoing challenge. The design, preparation, and evaluation of various smart NPs with specific physicochemical responses in tumor-related physiological conditions have been of great interests in both academic and clinical research. Of particular, smart enzyme-responsive nanoparticles can predictively and selectively react with specific enzymes expressed in tumor tissues, leading to targeted delivery of anti-tumor drugs, reduced systemic toxicity, and improved therapeutic effect. In addition, NPs interact with internal enzymes usually under mild conditions (low temperature, aqueous media, neutral or close to neutral pH) with high efficiency. In this review, recent advances in the past 5 years in enzyme-responsive nanoparticles for anti-tumor drug delivery are summarized and discussed. The following contents are divided based on the different action sites of enzymes toward NPs, notably hydrophobic core, cleavable/uncleavable linker, hydrophilic crown, and targeting ligand. Enzyme-engaged destruction of any component of these delicate nanoparticle structures could result in either targeting drug delivery or controlled drug release.

Lysine demethylase KDM3A regulates nanophotonic hyperthermia resistance generated by 2D silicene in breast cancer

Breast cancer (BC) is the most common malignant disease affecting women's health worldwide. The benefits from conventional therapeutic modalities are severely limited. An increasing number of promising photothermal materials have been recently developed and introduced into the therapeutic regimens of BC, but the underlying biological mechanism remains unclear. Silicon-based materials have enjoyed many popularities in the biomedical field owing to their desirable biocompatibility, biodegradability and versatility. Herein, we introduced two dimensional (2D) silicene nanosheets (SNSs) into the BC treatment and achieved profound photothermal-ablation efficacy. Importantly, this work reveals the underlying biological mechanism and regulation factors of photonic hyperthermia in BC. The RNA sequencing and immunoblot demonstrated that photothermia enhanced apoptosis in BC by activating caspase 3 and caspase 7. Importantly, knockdown of lysine demethylase KDM3A sensitized BC to photothermia epigenetically. It has been revealed that KDM3A could erase p53K372me1 and suppress the anti-cancer functions of p53, leading to the downregulation of pro-apoptotic proteins-PUMA and NOXA verified by Co-IP and ChIP-qPCR assays. Therefore, our results not only import near infrared light (NIR) induced photothermal ablation generated by SNSs-BSA into the BC treatment, but also clarify the underlying mechanism and regulation factors for further photothermal performance optimization and clinical translation.

Designing Stimuli-Responsive Upconversion Nanoparticles that Exploit the Tumor Microenvironment

Tailoring personalized cancer nanomedicines demands detailed understanding of the tumor microenvironment. In recent years, smart upconversion nanoparticles with the ability to exploit the unique characteristics of the tumor microenvironment for precise targeting have been designed. To activate upconversion nanoparticles, various bio-physicochemical characteristics of the tumor microenvironment, namely, acidic pH, redox reactants, and hypoxia, are exploited. Stimuli-responsive upconversion nanoparticles also utilize the excessive presence of adenosine triphosphate (ATP), riboflavin, and Zn²⁺ in tumors. An overview of the design of stimulus-responsive upconversion nanoparticles that precisely target and respond to tumors via targeting the tumor microenvironment and intracellular signals is provided. Detailed understanding of the tumor microenvironment and the personalized design of upconversion nanoparticles will result in more effective clinical translation.

An intelligent nanodevice based on the synergistic effect of telomerase-triggered photodynamic therapy and gene-silencing for precise cancer cell therapy

The development of intelligent and precise cancer therapy systems that enable accurate diagnosis and specific elimination of cancer cells while protecting normal cells to improve the safety and effectiveness of the treatment is still a challenge. Herein, we report a novel activatable nanodevice for precise cancer therapy. The nanodevice is constructed by adsorbing a DNA duplex probe onto MnO2 nanosheets. After cellular uptake, the DNA duplex probe undergoes telomerase-triggered conformation switching, resulting in a Ce6 "turn-on" signal for the identification of cancer cells. Furthermore, Deoxyribozyme (DNAzyme) is activated to catalyse the cleavage of survivin mRNA, actualizing a precise synergistic therapy in cancer cells involving photodynamic therapy and gene-silencing. The MnO2 nanosheets provide Mn2+ for the DNAzyme and relieve hypoxia to improve the efficiency of the photodynamic therapy. Live cell studies reveal that this nanodevice can diagnose cancer cells and specifically eliminate them without harming normal cells, so making the treatment safer and more effective. The developed DNA-MnO2 nanodevice provides a valuable and general platform for precise cancer therapy.

Near-Infrared-Detached Adhesion Enabled by Upconverting Nanoparticles

Achieving efficient and biocompatible detachment between adhered wet materials (i.e., tissues and hydrogels) is a major challenge. Recently, photodetachable topological adhesion has shown great promise as a strategy for conquering this hurdle. However, this photodetachment was triggered by UV light with poor biocompatibility and penetration capacity. This study describes near-infrared (NIR) light-detached topological adhesion based on polyacrylic acid coated upconverting nanoparticles (UCNP@PAA) and a photodetachable adhesive (termed Cell-Fe). Cell-Fe is a coordinated topological adhesive consisting of carboxymethylcellulose and Fe3+ that can be photodecomposed by UV light. To prepare a substrate for NIR-detached topological adhesion, UCNP@PAA and Cell-Fe were mixed and brushed on the surface of the model adherent. The UCNP@PAA can harvest NIR light and convert it into UV light, triggering the decomposition of the Cell-Fe and inducing the detachment. This NIR-detached topological adhesion is also feasible in deep tissue because of the ability of NIR light to penetrate tissue.

Recent advances of polyoxometalates in multi-functional imaging and photothermal therapy

The recent advances of polyoxometalate clusters in terms of near infrared photothermal properties for targeted tumor therapy have been summarized while the combined applications with various bio-imaging techniques and chemotherapies are reviewed.

Heterodimers made of metal–organic frameworks and upconversion nanoparticles for bioimaging and pH-responsive dual-drug delivery

An ingenious method was developed to grow metal–organic frameworks on the surface of UCNPs, resulting in the UCMOFs@D@5 nanosystem for bioimaging and pH-responsive dual-drug delivery.

Upconversion System with Quantum Dots as Sensitizer: Improved Photoluminescence and PDT Efficiency

Upconversion nanoparticles (UCNPs) are prospective platforms for bioimaging and phototherapy, but a critical bottleneck is the limited brightness due to the faint absorptivity of lanthanide ions and the low quantum yield. To circumvent this problem, we herein propose our strategy to reconstruct the energy cascade of UCNPs using semiconductor quantum dots (QDs) as light sensitizer of Nd³⁺/Yb³⁺ codoped UCNPs. Ag₂Se QDs with strong absorption at 808 nm acted as efficient antenna and transferred their energy to Yb³⁺ via a resonance energy transfer process, significantly enhancing the luminescence of UCNPs. This nanocomposite was then combined with Rose Bengal and applied for photodynamic therapy. Both in vitro and in vivo studies revealed the introduction of QDs improved the therapeutic performance remarkably. Our study suggests Ag₂Se QDs with excellent photophysical properties can be promising agents to overcome the shortcomings of UCNPs and further strengthen their applications.

Photosensitizer coated upconversion nanoparticles for triggering reactive oxygen species under 980 nm near-infrared excitation

Rare-earth-based upconversion nanotechnology has recently shown great promise for photodynamic therapy (PDT). NaGd(MoO₄)₂-based materials have a scheelite structure with good thermal and chemical stability, and excellent up-conversion luminescence properties after co-doping rare earth ions (Tm³⁺ and Yb³⁺), which can effectively excite the photosensitizer to generate reactive oxygen species (ROS). In this work, Tm³⁺ and Yb³⁺ co-doped NaGd(MoO₄)₂ upconversion nanoparticles (UCNPs) are prepared by the sol-gel method and further complexed with photosensitizer MC540 (UCNPs@MC540). The prepared UCNPs showed a tetragonal phase and revealed nanoparticles with an average size of 150 nm. Under 980 nm excitation, the UCNPs exhibited a dominant blue emission band (¹G₄→³H₆) of Tm³⁺, while the optimum doping concentration was identified at 1% Tm³⁺ and 20% Yb³⁺. In addition, the blue emissions of Tm³⁺ simultaneously activate the MC540 composited on the surface of the nanoparticles to produce a large amount of singlet oxygen (¹O₂), which is detected by DCFH-DA. Moreover, UCNPs@MC540 also shows strong emission at around 800 nm near-infrared. The results show that the UCNPs@MC540 materials have potential application prospects in PDT and biological imaging.

Tumor-acidity activated surface charge conversion of two-photon fluorescent nanoprobe for enhanced cellular uptake and targeted imaging of intracellular hydrogen peroxide

Elevated levels of intracellular hydrogen peroxide (H2O2) are closely related to the development of cancers. Specific imaging of H2O2 in tumor sites would be significant not only for cancer diagnosis but also for gaining a deep understanding of the role of H2O2 in cancer. However, traditional fluorescent probes based only on responses to overexpression levels of H2O2 in cancer cells are insufficient to distinguish cancer cells from other unhealthy or healthy cells in complex biological systems. Herein, we developed a smart, two-photon fluorescent GC-NABP nanoprobe with pH-dependent surface charge conversion for tumor-targeted imaging of H2O2. The nanoprobe was constructed by the self-assembly of amphiphilic GC-NABP, which was synthesized by grafting the hydrophobic, H2O2-responsive and two-photon fluorophore, NABP, onto hydrophilic biopolymer glycol chitosan (GC). Taking advantage of pH-titratable amino groups on GC, the nanoprobe had the capability of surface charge conversion from negative at physiologic pH to positive in the acidic tumor microenvironment. The positive charge of the nanoprobe promoted electrostatic interactions with cell membranes, leading to enhanced cellular uptake in acidic environment. Upon cellular uptake, the high level of H2O2 in tumor cells triggered boronate deprotections of the nanoprobe, generating a "turn-on" fluorescence emission for H2O2 imaging. The nanoprobe exhibited good sensitivity and selectivity to H2O2 with a detection limit down to 110 nM in vitro. The results from flow cytometry and two-photon fluorescence imaging of H2O2 in living cells and tissues evidenced the enhanced cellular uptake and targeted imaging of intracellular H2O2 in acidic environment. Compared to control nanoparticles that lack pH sensitivity, our nanoprobe showed enhanced accumulation in tumor sites and was applied to targeted imaging of H2O2 in a tumor-bearing mouse model. This work demonstrates that the nanoprobe GC-NABP holds great promise for tumor-specific imaging of cellular H2O2, providing a potential tool to explore the role of H2O2 in tumor sites.

Tumor self-responsive upconversion nanomedicines for theranostic applications

To date, malignant tumors continue to be the most lethal disease, causing more than 8.2 million deaths worldwide each year. In recent years, nanostructures based on rare-earth upconversion luminescent nanoparticles have shown significant advantages in the integration of multimodal imaging and therapy. Compared with normal tissues, the tumor microenvironment (TME) exhibits unique characteristics including high interstitial fluid pressure, abnormal blood vessels, a hypoxic and slightly acidic environment, and high levels of glutathione (GSH) and hydrogen peroxide (H2O2). According to these characteristics, increasing attention in the antitumor field has been given to designing nanomedicines with specific responses to the TME based on rare-earth upconversion nanoparticles (UCNPs) and to achieving efficient tumor diagnosis and treatment under the premise of reducing side effects. Nevertheless, a review that systematically summarizes TME-responsive upconversion nanomedicines (UCNMs) for realizing tumor self-enhanced theranostics has not been published to date. In this review, we summarize the recent progress made in UCNP-based nanotherapeutics by highlighting the increasingly developing trend of TME-responsive UCNMs. The general characteristics of the TME are introduced in detail and their utilization in designing TME-responsive UCNMs is systematically discussed. Based on NIR light-excited optical imaging, we discuss the superiority of UCNMs when applied in tumor theranostics with an emphasis on how to use them to realize TME-mediated multimodal imaging-guided therapy.

A theranostic saponin nano-assembly based on FRET of an aggregation-induced emission photosensitizer and photon up-conversion nanoparticles

A photodynamic aggregation-induced emissive (AIE) fluorophore, characterized by near-infrared (NIR) emission, was created based on a fluorescence resonance energy transfer (FRET) donor of appreciable NIR up-conversion nanoparticles (UCNPs) and acceptor of immense fluorescence emissive AIEgen. Hence, the entrapment of the FRET couple into an amphiphilic saponin-based nanoscaled self-assembly demonstrated appealing theranostic functions in producing immense fluorescence emission and cytotoxic reactive oxygen species (ROS).

Time-staggered delivery of erlotinib and doxorubicin by gold nanocages with two smart polymers for reprogrammable release and synergistic with photothermal therapy

Photochemotherapy is currently an effective anticancer therapy. Recently, it has been reported that cancer cells pretreated with epidermal growth factor receptor (EGFR) inhibitor erlotinib (Erl) can significantly synergize its apoptosis against the DNA damaging agent doxorubicin (Dox). As a result, we designed two gold nanocages (Au NCs) microcontainers covered with different smart polymer shell-PAA (pH responsive) and p (NIPAM-co-AM) (temperature responsive) containing Erl and Dox respectively. The acidic tumor microenvironment and NIR light irradiation can selectively activate the release of Erl and Dox. Time staggered release of Erl and Dox and photothermal therapy enhance the apoptotic signaling pathways, resulting in improved tumor cell killing in both MCF-7 (low EGFR expression) and A431 (very high EGFR expression) tumor cells, but more efficient in the latter. The photochemotherapy strategy controls the order and duration of drug exposure precisely in spatial and temporal, and significantly improves the therapeutic efficacy against high EGFR expressed tumors.

Lanthanide-Doped Photoluminescence Hollow Structures: Recent Advances and Applications

Lanthanide-doped nanomaterials have attracted significant attention for their preeminent properties and widespread applications. Due to the unique characteristic, the lanthanide-doped photoluminescence materials with hollow structures may provide advantages including enhanced light harvesting, intensified electric field density, improved luminescent property, and larger drug loading capacity. Herein, the synthesis, properties, and applications of lanthanide-doped photoluminescence hollow structures (LPHSs) are comprehensively reviewed. First, different strategies for the engineered synthesis of LPHSs are described in detail, which contain hard, soft, self-templating methods and other techniques. Thereafter, the relationship between their structure features and photoluminescence properties is discussed. Then, niche applications including biomedicines, bioimaging, therapy, and energy storage/conversion are focused on and superiorities of LPHSs for these applications are particularly highlighted. Finally, keen insights into the challenges and personal prospects for the future development of the LPHSs are provided.

Precisely tailored shell thickness and Ln3+ content to produce multicolor emission from Nd3+-sensitized Gd3+-based core/shell/shell UCNPs through bi-directional energy transfer

Lanthanide (Ln3+)-doped upconversion nanoparticles (UCNPs) have been paid great attention as multiplexing agents due to their numerous uses in biological and clinical applications such as bioimaging and magnetic resonance imaging (MRI), to name a few. To achieve efficient multicolor emission from UCNPs under single 808 nm excitation and avoid detrimental cross-relaxations between the Ln3+ activator ions (positioned in either the core and/or shell in the core/shell), it is essential to design an adequate nanoparticle architecture. Herein, we demonstrate the tailoring of multicolor upconversion luminescence (UCL) from Nd3+-sensitized Gd3+-based core/shell/shell UCNPs with an architecture represented as NaGdF4:Tm3+(0.75)/Yb3+(40)/Ca2+(7)/Nd3+(1)@NaGdF4:Ca2+(7)/Nd3+(30)@NaGdF4:Yb3+(40)/Ca2+(7)/Nd3+(1)/Er3+(X = 1, 2, 3, 5, 7) [hereafter named CSS (Er3+ = 1, 2, 3, 5 and 7 mol%)]. Such UCNPs can be excited at a single wavelength (∼808 nm) without generation of any local heat. Incorporation of substantial Nd3+-sensitizers with an appropriate concentration in the middle layer allows efficient harvesting of excitation light which migrates bi-directionally across the core/shell interfaces in sync to produce blue emission from Tm3+ (activator) ions in the core as well as green and red emission from Er3+ (activator) ions in the outermost shell. Introduction of Ca2+ lowers the local crystal field symmetry around Ln3+ ions and subsequently affects their intra 4f-4f transition probability, thus enhancing the upconversion efficiency of the UCNPs. By simple and precise control of the shell thickness along with tuning the content of Ln3+ ions in each domain, multicolor UCL can be produced, ranging from blue to white. We envision that our sub-20 nm sized Nd3+-sensitized Gd3+-based UCNPs are not only potential candidates for a variety of multiplexed biological applications (without impediment of any heating effect), but also can act as MRI contrast agents in clinical diagnosis.

Upconversion-mediated ZnFe2O4 nanoplatform for NIR-enhanced chemodynamic and photodynamic therapy

ZnFe2O4, a semiconductor catalyst with high photocatalytic activity, is ultrasensitive to ultraviolet (UV) light and tumor H2O2 for producing reactive oxygen species (ROS). Thereby, ZnFe2O4 can be used for photodynamic therapy (PDT) from direct electron transfer and the newly defined chemodynamic therapy (CDT) from the Fenton reaction. However, UV light has confined applicability because of its high phototoxicity, low penetration, and speedy attenuation in the biotissue. Herein, an upconversion-mediated nanoplatform with a mesoporous ZnFe2O4 shell was developed for near-infrared (NIR) light enhanced CDT and PDT. The nanoplatform (denoted as Y-UCSZ) was comprised of upconversion nanoparticles (UCNPs), silica shell, and mesoporous ZnFe2O4 shell and was synthesized through a facile hydrothermal method. The UCNPs can efficiently transfer penetrable NIR photons to UV light, which can activate ZnFe2O4 for producing singlet oxygen thus promoting the Fenton reaction for ROS generation. Besides, Y-UCSZ possesses enormous internal space, which is highly beneficial for housing DOX (doxorubicin, a chemotherapeutic agent) to realize chemotherapy. Moreover, the T 2-weighted magnetic resonance imaging (MRI) effect from Fe3+ and Gd3+ ions in combination with the inherent upconversion luminescence (UCL) imaging and computed tomography (CT) from the UCNPs makes an all-in-one diagnosis and treatment system. Importantly, in vitro and in vivo assays authenticated excellent biocompatibility of the PEGylated Y-UCSZ (PEG/Y-UCSZ) and high anticancer effectiveness of the DOX loaded PEG/Y-UCSZ (PEG/Y-UCSZ&DOX), indicating its potential application in the cancer treatment field.

Rationally designed pure-inorganic upconversion nanoprobes for ultra-highly selective hydrogen sulfide imaging and elimination in vivo

Lung injury is a hydrogen sulfide (H2S)-associated complication with high mortality in acute pancreatitis (AP) cases. Herein, we used Prussian Blue (PB) as a H2S-responsive acceptor to develop a novel pure-inorganic upconversion nanoprobe for detecting and eliminating H2S, which can be used for diagnosing AP and alleviating lung injury. Upconversion nanoprobes with 5 nm PB shells were optimized to achieve outstanding in vitro H2S detection capacity (linear range: 0-150 μM, LOD: 50 nM), which met the in vivo serum H2S range, and thus were feasible for imaging H2S in vivo. More importantly, when combined with the traditional H2S synthetase inhibitor dl-PAG, the nanoprobes also served as a therapeutic agent that synergistically alleviated lung injury. As PB is an FDA-approved drug, our work proposes a potential clinical modality for the early diagnosis of AP, which will decrease lung injury-induced mortality and increase the survival rates of AP cases.

Ferric Hydroxide-Modified Upconversion Nanoparticles for 808 nm NIR-Triggered Synergetic Tumor Therapy with Hypoxia Modulation

The efficacy of dynamic therapy for solid tumors suffers daunting challenges induced by tumor hypoxia. Herein, we report a biocompatible nanosystem containing Fe(OH)₃-modified upconversion nanoparticles (UCNPs) for promoting synergetic chemo- and photodynamic therapy with the modulation of tumor hypoxia. In this system, UCNPs convert 808 nm near-infrared excitation to visible photon energy, which stimulates chlorin-e6 photosensitizers to generate toxic reactive oxygen species (ROS) by consumption of dissolved oxygen in cancer cells. Importantly, we employ Fe(OH)₃ compounds to enable continuous oxygen generation in cancer cells and, meanwhile, induce extra ROS formation through the Fenton-like reaction. The system consequently improves the tumor treatment efficacy in vitro and in vivo. This study puts forward a novel combinatorial therapeutic platform for tumor microenvironment modulation and enhanced cancer therapy.

A smart tumor microenvironment responsive nanoplatform based on upconversion nanoparticles for efficient multimodal imaging guided therapy

A smart tumor microenvironment responsive theranostic nanoplatform USPDF for UCL/CT dual-mode imaging and combination of chemotherapy and photothermal therapy.

Ultrafast synthesis of fluorine-18 doped bismuth based upconversion nanophosphors for tri-modal CT/PET/UCL imaging in vivo

A fluorine-18 doped bismuth upconversion luminescence (UCL) nanoprobe (¹⁸F-UNBOF) was quickly synthesized within 1 min at room temperature, and it could be utilized for computed tomography (CT), positron emission tomography (PET) and UCL imaging in vivo.

Heterogeneous growth of palladium nanocrystals on upconversion nanoparticles for multimodal imaging and photothermal therapy

Based on the heterogeneous growth of nano-palladium on UCNPs, a new kind of nanocomposite was developed that can be used for dual-imaging guided photothermal therapy. This smart strategy provides new insights for future development of materials based on the multicomponent nanocomposites.

Preparation and spectroscopic study of a water-soluble NaYF4:Yb3+/Er3+@NaGdF4 crystal particle and its application in bioimaging

Water-soluble, magnetic and up-conversion luminescent NaYF₄:Yb³⁺/Er³⁺@NaGdF₄ core–shell particles were prepared directly by the hydrothermal method.

Emerging Strategies of Nanomaterial-Mediated Tumor Radiosensitization

Nano-radiosensitization has been a hot concept for the past ten years, and the nanomaterial-mediated tumor radiosensitization method is mainly focused on increasing intracellular radiation deposition by high atomic number (high Z) nanomaterials, particularly gold (Au)-mediated radiation enhancement. Recently, various new nanomaterial-mediated radiosensitive approaches have been successively reported, such as catalyzing reactive oxygen species (ROS) generation, consuming intracellular reduced glutathione (GSH), overcoming tumor hypoxia, and various synergistic radiotherapy ways. These strategies may open a new avenue for enhancing the radiotherapeutic effect and avoiding its side effects. Nevertheless, reviews systematically summarizing these newly emerging methods and their radiosensitive mechanisms are still rare. Therefore, the general strategies of nanomaterial-mediated tumor radiosensitization are comprehensively summarized, particularly aiming at introducing the emerging radiosensitive methods. The strategies are divided into three general parts. First, methods on account of the intrinsic radiosensitive properties of nanoradiosensitizers for radiosensitization are highlighted. Then, newly developed synergistic strategies based on multifunctional nanomaterials for enhancing radiotherapy efficacy are emphasized. Third, nanomaterial-mediated radioprotection approaches for increasing the radiotherapeutic ratio are discussed. Importantly, the clinical translation of nanomaterial-mediated tumor radiosensitization is also covered. Finally, further challenges and outlooks in this field are discussed.

A GSH-responsive nanophotosensitizer for efficient photodynamic therapy

Photodynamic therapy (PDT) is a promising cancer treatment modality, which depends on the reactive oxygen species (ROS) generated by a photosensitizer to kill cancer cells. The lack of selectivity and the over-production of glutathione (GSH) in cancer cells are the two major challenges for efficient and safe cancer PDT because they can cause harm to normal tissues and eliminate ROS in cancer cells. Herein, we report a GSH-responsive nanophotosensitizer based on CoOOH nanosheets for PDT of cancer. The nanophotosensitizer shows negligible photo-toxicity toward normal cells because of the quenching effect between CoOOH and photosensitizer Ce6. In the presence of overexpressed GSH, Ce6 molecules can be released into cancer cells because of GSH induced degradation of CoOOH nanosheets. In vivo experiments demonstrated that the tumor growth was efficiently inhibited by the CoOOH-based PDT strategy. The current nanophotosensitizer represents a promising smart platform to synergistically improve the therapeutic index and safety of PDT.