Recent Progress in Upconversion Photodynamic Therapy

NIR Photoregulated Theranostic System Based on Hexagonal-Phase Upconverting Nanoparticles for Tumor-Targeted Photodynamic Therapy and Fluorescence Imaging

Although photodynamic therapy (PDT) is an effective, minimally invasive therapeutic modality with advantages in highly localized and specific tumor treatments, large and deep-seated cancers within the body cannot be successfully treated due to low transparency to visible light. To improve the therapeutic efficiency of tumor treatment in deep tissue and reduce the side effects in normal tissue, this study developed a near-infrared (NIR)-triggered upconversion nanoparticle (UCNP)-based photosensitizer (PS) carrier as a new theranostics system. The NaYF4:Yb/Er UCNPs were synthesized by a hydrothermal method, producing nanoparticles of a uniformly small size (≈20 nm) and crystalline morphology of the hexagonal phase. These UCNPs were modified with folic acid-conjugated biocompatible block copolymers through a bidentate dihydrolipoic acid linker. The polymer modified hexagonal phase UCNPs (FA-PEAH-UCNPs) showed an improved dispersibility in the aqueous solution and strong NIR-to-vis upconversion fluorescence. The hydrophobic PS, pheophorbide a (Pha), was then conjugated to the stable vectors. Moreover, these UCNP-based Pha carriers containing tumor targeting folic acid ligands exhibited the significantly enhanced cellular uptake efficiency as well as PDT treatment efficiency. These results suggested that this system could extend the excitation wavelength of PDT to the NIR region and effectively improve therapeutic efficiency of PSs.

Recent advances in nanoscale materials for antibody-based cancer theranostics

The quest for advanced management tools or options of various cancers has been on the rise to efficiently reduce their risks of mortality without the demerits of conventional treatments (e.g., undesirable side effects of the medications on non-target tissues, non-targeted distribution, slow clearance of the administered drugs, and the development of drug resistance over the duration of therapy). In this context, nanomaterials-antibody conjugates can offer numerous advantages in the development of cancer theranostics over conventional delivery systems (e.g., highly specific and enhanced biodistribution of the drug in targeted tissues, prolonged systemic circulation, low toxicity, and minimally invasive molecular imaging). This review comprehensively discusses and evaluates recent advances in the application of nanomaterial-antibody bioconjugates for cancer theranostics for the further advancement in the control of diverse cancerous diseases. Further, discussion is expanded to cover the various challenges and limitations associated with the design and development of nanomaterial-antibody conjugates applicable towards better management of cancer.

Nano Antiviral Photodynamic Therapy: a Probable Biophysicochemical Management Modality in SARS-CoV-2

INTRODUCTION

COVID-19 disease has shocked the world by its spread and contagiousness. At this time, there is no valid vaccine and no proven drug treatment for COVID-19 patients. Current treatments are focused on Oxygenation, Cytokine Storm management, anti-inflammatory effects, and antiviral therapy. Antiviral photodynamic therapy (aPDT) is based on the reaction between a photo-sensitive agent and a light source in the presence of oxygen which can produce oxidative and free radical agents to damage the virus' structures. Recent studies show that nanotechnology can improve aPDT's outcome. The aim of this study was to find out the potential therapeutic effects of Nano antiviral photodynamic therapy on COVID-19.

AREAS COVERED

This review evaluates Nano Antiviral Photodynamic Therapy: A Probable Biophysicochemical Management Modality in SARS-CoV-2. Data were extracted from published different studies published on PUBMED, SCOPUS, and Web of Science.

EXPERT OPINION

Studies indicating that aPDT and Nano-based aPDT can be useful in viral pulmonary complications like Influenza, SARS-CoV, and MERS, but there was no direct study on SARS-Cov-2. Recent studies showed that Nano-based aPDT could relate to control of the stages of viral infections. Altogether, further investigations for the application of nanomedicine in antimicrobial photodynamic inactivation are needed for COVID-19 Management.

A Robust Intrinsically Green Fluorescent Poly(Amidoamine) Dendrimer for Imaging and Traceable Central Nervous System Delivery in Zebrafish

Intrinsically fluorescent poly(amidoamine) dendrimers (IF-PAMAM) are an emerging class of versatile nanoplatforms for in vitro tracking and bio-imaging. However, limited tissue penetration of their fluorescence and interference due to auto-fluorescence arising from biological tissues limit its application in vivo. Herein, a green IF-PAMAM (FGP) dendrimer is reported and its biocompatibility, circulation, biodistribution and potential role for traceable central nervous system (CNS)-targeted delivery in zebrafish is evaluated, exploring various routes of administration. Key features of FGP include visible light excitation (488 nm), high fluorescence signal intensity, superior photostability and low interference from tissue auto-fluorescence. After intravenous injection, FGP shows excellent imaging and tracking performance in zebrafish. Further conjugating FGP with transferrin (FGP-Tf) significantly increases its penetration through the blood-brain barrier (BBB) and prolongs its circulation in the blood stream. When administering through local intratissue microinjection, including intracranial and intrathecal injection in zebrafish, both FGP and FGP-Tf exhibit excellent tissue diffusion and effective cellular uptake in the brain and spinal cord, respectively. This makes FGP/FGP-Tf attractive for in vivo tracing when transporting to the CNS is desired. The work addresses some of the major shortcomings in IF-PAMAM and provides a promising application of these probes in the development of drug delivery in the CNS.

Natural Hydrogels Applied in Photodynamic Therapy

Natural hydrogels are three-dimensional (3D) water-retaining materials with a skeleton consisting of natural polymers, their derivatives or mixtures. Natural hydrogels can provide sustained or controlled drug release and possess some unique properties of natural polymers, such as biodegradability, biocompatibility and some additional functions, such as CD44 targeting of hyaluronic acid. Natural hydrogels can be used with photosensitizers (PSs) in photodynamic therapy (PDT) to increase the range of applications. In the current review, the pertinent design variables are discussed along with a description of the categories of natural hydrogels available for PDT.

A versatile platform for bioimaging based on colominic acid-decorated upconversion nanoparticles

Lanthanide-doped upconversion nanoparticles (UCNPs) are promising bioimaging agents that emit light under near infra-red excitation, capable of penetrating deep in biotissues with a high signal-to-noise ratio. Their successful implementation is principally associated with surface functionalization. Here, we report on UCNP surface modification with highly hydrophilic, endogenous, non-toxic, non-immunogenic colominic acid, conferring "stealth" properties. We proposed surface functionalization of UCNPs based on a two-step strategy, which consists of hydrophilization with polyethyleneimine and attachment of colominic acid by electrostatic or covalent bond formation. Analysis revealed that regardless of the nature of the bond, colominic acid acted as a non-cytotoxic UCNP surface coating with low nonspecific blood protein adsorption. UCNP-colominic acid nanocomplexes exhibited low uptake by macrophages in vitro, which plays an active role in inflammatory reactions. We demonstrated the superiority of colominic acid compared to polyethylene glycol coating in terms of the prolonged circulation time in the bloodstream of small animals when injected intravenously. The colominic acid coating made it possible to prolong the UCNP circulation time up to 3 h. This led to the efficient UCNP accumulation in the inflammation site due to microvascular remodeling, accompanied by an enhanced uptake and retention effect. UCNP-assisted imaging of inflammation in the whole-body mode as well as local visualization of blood vessels were acquired in vivo. These collective findings validate the functional significance of UCNP decoration with colominic acid for their application in bioimaging.

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.

Near Infrared Light Triggered Photo/Immuno-Therapy Toward Cancers

Nanomaterials-based phototherapies, mainly including photothermal therapy (PTT), photodynamic therapy (PDT) and photoimmunotherapy (PIT), present high efficacy, minimal invasion and negligible adverse effects in cancer treatment. The integrated phototherapeutic modalities can enhance the efficiency of cancer immunotherapy for clinical application transformation. The near-infrared (NIR) light source enables phototherapies with the high penetration depth in the biological tissues, less toxic to normal cells and tissues and a low dose of light irradiation. Mediated via the novel NIR-responsive nanomaterials, PTT and PDT are able to provoke cancer cells apoptosis from the generated heat and reactive oxygen species, respectively. The released cancer-specific antigens and membrane damage danger signals from the damaged cancer cells trigger immune responses, which would enhance the antitumor efficacy via a variety of immunotherapy. This review summarized the recent advances in NIR-triggered photo-/immune-therapeutic modalities and their synergistic mechanisms and applications toward cancers. Furthermore, the challenges, potential solutions and future directions of NIR-triggered photo-/immunotherapy were briefly discussed.

Local Overheating of Biotissue Labeled With Upconversion Nanoparticles Under Yb3+ Resonance Excitation

Local overheating of biotissue is a critical step for biomedical applications, such as photothermal therapy, enhancement of vascular permeability, remote control of drug release, and so on. Overheating of biological tissue when exposed to light is usually realized by utilizing the materials with a high-absorption cross section (gold, silica, carbon nanoparticles, etc.). Here, we demonstrate core/shell NaYF4:Yb3+, Tm3+/NaYF4 upconversion nanoparticles (UCNPs) commonly used for bioimaging as promising near-infrared (NIR) absorbers for local overheating of biotissue. We assume that achievable temperature of tissue labeled with nanoparticles is high enough because of Yb3+ resonance absorption of NIR radiation, whereas the use of auxiliary light-absorbing materials or shells is optional for photothermal therapy. For this purpose, a computational model of tissue heating based on the energy balance equations was developed and verified with the experimentally obtained thermal-graphic maps of a mouse in response to the 975-nm laser irradiation. Labeling of biotissue with UCNPs was found to increase the local temperature up to 2°C compared to that of the non-labeled area under the laser intensity lower than 1 W/cm2. The cellular response to the UCNP-initiated hyperthermia at subcritical ablation temperatures (lower than 42°C) was demonstrated by measuring the heat shock protein overexpression. This indicates that the absorption cross section of Yb3+ in UCNPs is relatively large, and microscopic temperature of nanoparticles exceeds the integral tissue temperature. In summary, a new approach based on the use of UCNP without any additional NIR absorbers was used to demonstrate a simple approach in the development of photoluminescent probes for simultaneous bioimaging and local hyperthermia.

Modularly Assembled Upconversion Nanoparticles for Orthogonally Controlled Cell Imaging and Drug Delivery

Upconversion nanoparticles (UCNPs) have been used effectively as light transducers to convert near-infrared irradiation to short-wavelength emissions for photoactivation in deep tissues. UCNPs with single/multiple emissions under excitation at a single wavelength can be used for simultaneous activation of single or multiple photosensitive molecules only; an ideal multifunctional UCNP nanoplatform should not only have the ability to load multiple molecules but also should activate them at the right time with the right dose when necessary, depending upon the application for which it is used. The control of many biological processes requires complex (simultaneous or subsequent) photoactivation at different time points. Subsequent photoactivation requires UCNPs with orthogonal fluorescence emissions, which can be controlled independently. So far, there are only a few reports about UCNPs with orthogonal emissions. Synthesis of these orthogonal emission nanoparticles is complicated and tedious because nanoparticles with multiple shells need to be synthesized, and different lanthanide ions need to be doped into different shells. Also, there is no flexibility for changing the doped ions and emission profile after the nanoparticles are produced. Here, we have demonstrated a versatile method to modularly assemble individual UCNPs into UCNP clusters (UCNPs-C) with adjustable emissions. The synthesis is much easier, and there is a lot of flexibility in changing the particle size, shape, doped ions, and emission profile. We have demonstrated the use of such UCNPs-C for color encoding at the nanoscale. We further designed orthogonal photoactivatable UCNPs-C (OP-UCNPs-C), which can be independently activated under 980 nm excitation for red emission and 808 nm excitation for UV/blue emission. These OP-UCNPs-C were used for independent activation of processes for cell imaging (980 nm) and drug delivery (808 nm). In comparison to the traditional nonprogrammed activation, a programmed controlled imaging and drug delivery process could guarantee highly targeted and enhanced cell death of cancerous cells.

Advances in nanomaterials for photodynamic therapy applications: Status and challenges

Photodynamic therapy (PDT), as a non-invasive therapeutic modality that is alternative to radiotherapy and chemotherapy, is extensively investigated for cancer treatments. Although conventional organic photosensitizers (PSs) are still widely used and have achieved great progresses in PDT, the disadvantages such as hydrophobicity, poor stability within PDT environment and low cell/tissue specificity largely limit their clinical applications. Consequently, nano-agents with promising physicochemical and optical properties have emerged as an attractive alternative to overcome these drawbacks of traditional PSs. Herein, the up-to-date advances in the fabrication and fascinating applications of various nanomaterials in PDT have been summarized, including various types of nanoparticles, carbon-based nanomaterials, and two-dimensional nanomaterials, etc. In addition, the current challenges for the clinical use of PDT, and the corresponding strategies to address these issues, as well as future perspectives on further improvement of PDT have also been discussed.

Gold Nanoshell-Linear Tetrapyrrole Conjugates for Near Infrared-Activated Dual Photodynamic and Photothermal Therapies

Photodynamic therapy (PDT) is a treatment in which photoactive compounds delivered to cancerous tissues are excited with light and then transfer the absorbed energy to adjacent tissue oxygen molecules to generate toxic singlet oxygen (¹O₂). As ¹O₂ is produced only where light and photosensitizers (PSs) are combined, PDT holds promise as a minimally invasive, highly selective treatment for certain cancers. The practical application of PDT requires easily synthesized, water-soluble PSs that have low dark toxicities, high ¹O₂ quantum yields, and efficient absorption of 650-850 nm near-infrared (NIR) light, which deeply penetrates tissue. We recently developed a linear tetrapyrrole metal complex, Pd[DMBil1]-PEG₇₅₀, that meets most of these criteria. This complex is remarkably effective as a PS for PDT against triple-negative breast cancer (TNBC) cells but, critically, it does not absorb NIR light, which is necessary to treat deeper tumors. To enable NIR activation, we synthesized a new derivative, Pd[DMBil1]-PEG₅₀₀₀-SH, which bears a thiol functionality that facilitates conjugation to NIR-absorbing gold nanoshells (NSs). Upon excitation with pulsed 800 nm light, NSs emit two-photon-induced photoluminescence spanning 500-700 nm, which can sensitize the attached PSs to initiate PDT. Additionally, NSs produce heat upon 800 nm irradiation, endowing the NS-PS conjugates with an auxiliary photothermal therapeutic (PTT) capability. Here, we demonstrate that NS-PS conjugates are potent mediators of NIR-activated tandem PDT/PTT against TNBC cells in vitro. We show that Pd[DMBil1]-PEG₅₀₀₀-SH retains the photophysical properties of the parent Pd[DMBil1] complex, and that NS-PS generate ¹O₂ under pulsed 800 nm irradiation, confirming activation of the PSs by photoluminescence emitted from NSs. TNBC cells readily internalize NS PS conjugates, which generate reactive oxygen species in the cells upon pulsed NIR irradiation to damage DNA and induce apoptosis. Together, these findings demonstrate that exploiting photoluminescent NSs as carriers of efficient Pd[DMBil1] PSs is an effective strategy to enable NIR light-activated tandem PDT/PTT.

Fluorescence resonance energy transfer-based drug delivery systems for enhanced photodynamic therapy

In this Review, recent advances in fluorescence resonance energy transfer-based drug delivery systems for enhanced photodynamic therapy are described, and the current challenges and perspectives in this emerging field are also discussed.

One-pot synthesis of theranostic nanocapsules with lanthanide doped nanoparticles

One-pot synthesis of theranostic nanocapsules with lanthanide doped nanoparticles via interfacial templating condensation for upconversion based photodynamic therapy.

Near Infrared-Activated Dye-Linked ZnO Nanoparticles Release Reactive Oxygen Species for Potential Use in Photodynamic Therapy

Novel dye-linked zinc oxide nanoparticles (NPs) hold potential as photosensitizers for biomedical applications due to their excellent thermal- and photo-stability. The particles produced reactive oxygen species (ROS) upon irradiation with 850 nm near infrared (NIR) light in a concentration- and time-dependent manner. Upon irradiation, ROS detected in vitro in human umbilical vein endothelial cells (HUVEC) and human carcinoma MCF7 cells positively correlated with particle concentration and interestingly, ROS detected in MCF7 was higher than in HUVEC. Preferential cytotoxicity was also exhibited by the NPs as cell killing was higher in MCF7 than in HUVEC. In the absence of irradiation, dye-linked ZnO particles minimally affected the viability of cell (HUVEC) at low concentrations (<30 μg/mL), but viability significantly decreased at higher particle concentrations, suggesting a need for particle surface modification with poly (ethylene glycol) (PEG) for improved biocompatibility. The presence of PEG on particles after dialysis was indicated by an increase in size, an increase in zeta potential towards neutral, and spectroscopy results. Cell viability was improved in the absence of irradiation when cells were exposed to PEG-coated, dye-linked ZnO particles compared to non-surface modified particles. The present study shows that there is potential for biological application of dye-linked ZnO particles in photodynamic therapy.

An Nd3+-Sensitized Upconversion Fluorescent Sensor for Epirubicin Detection

We describe here an Nd³⁺-sensitized upconversion fluorescent sensor for epirubicin (EPI) detection in aqueous solutions under 808 nm laser excitation. The upconversion fluorescence of nanoparticles is effectively quenched in the presence of EPI via a fluorescence resonance energy transfer mechanism. The dynamic quenching constant was 2.10 × 10⁴ M⁻¹. Normalized fluorescence intensity increased linearly as the EPI concentration was raised from 0.09 μM to 189.66 μM and the fluorometric detection limit was 0.05 μM. The sensing method was simple, fast, and low-cost and was able to be applied to determine the levels of EPI in urine with spike recoveries from 97.5% to 102.6%. Another important feature of the proposed fluorescent sensor is that it holds a promising potential for in vivo imaging and detection due to its distinctive properties such as weak autofluorescence, low heating effect, and high light penetration depth.

Remote Light-Responsive Nanocarriers for Controlled Drug Delivery: Advances and Perspectives

Engineering of smart photoactivated nanomaterials for targeted drug delivery systems (DDS) has recently attracted considerable research interest as light enables precise and accurate controlled release of drug molecules in specific diseased cells and/or tissues in a highly spatial and temporal manner. In general, the development of appropriate light-triggered DDS relies on processes of photolysis, photoisomerization, photo-cross-linking/un-cross-linking, and photoreduction, which are normally sensitive to ultraviolet (UV) or visible (Vis) light irradiation. Considering the issues of poor tissue penetration and high phototoxicity of these high-energy photons of UV/Vis light, recently nanocarriers have been developed based on light-response to low-energy photon irradiation, in particular for the light wavelengths located in the near infrared (NIR) range. NIR light-triggered drug release systems are normally achieved by using two-photon absorption and photon upconversion processes. Herein, recent advances of light-responsive nanoplatforms for controlled drug release are reviewed, covering the mechanism of light responsive small molecules and polymers, UV and Vis light responsive nanocarriers, and NIR light responsive nanocarriers. NIR-light triggered drug delivery by two-photon excitation and upconversion luminescence strategies is also included. In addition, the challenges and future perspectives for the development of light triggered DDS are highlighted.

Graphene quantum dots (GQDs)-based nanomaterials for improving photodynamic therapy in cancer treatment

Graphene quantum dots (GQDs) as novel nanomaterials, have received significant interest in the field of biomedical applications. It is worth noting that a large amount of research is devoted to GQDs-based nanocomposites for cancer treatment, especially for photodynamic therapy (PDT), in that they can act not only as more favorable photosensitizers (PSs) but also nanoplatforms for delivering PSs. In this review, the biological behavior and physicochemical properties of GQDs for PDT are described in detail, and the application of GQDs-based nanocomposites in improved PDT and PDT-based combination therapies is analyzed, which may provide a new strategy for designing efficient PDT systems for cancer treatment.

Trends and targets in antiviral phototherapy

Photodynamic therapy (PDT) is a well-established treatment option in the treatment of certain cancerous and pre-cancerous lesions. Though best-known for its application in tumor therapy, historically the photodynamic effect was first demonstrated against bacteria at the beginning of the 20^th century. Today, in light of spreading antibiotic resistance and the rise of new infections, this photodynamic inactivation (PDI) of microbes, such as bacteria, fungi, and viruses, is gaining considerable attention. This review focuses on the PDI of viruses as an alternative treatment in antiviral therapy, but also as a means of viral decontamination, covering mainly the literature of the last decade. The PDI of viruses shares the general action mechanism of photodynamic applications: the irradiation of a dye with light and the subsequent generation of reactive oxygen species (ROS) which are the effective phototoxic agents damaging virus targets by reacting with viral nucleic acids, lipids and proteins. Interestingly, a light-independent antiviral activity has also been found for some of these dyes. This review covers the compound classes employed in the PDI of viruses and their various areas of use. In the medical area, currently two fields stand out in which the PDI of viruses has found broader application: the purification of blood products and the treatment of human papilloma virus manifestations. However, the PDI of viruses has also found interest in such diverse areas as water and surface decontamination, and biosafety.

Anti-Biofilm Property of Bioactive Upconversion Nanocomposites Containing Chlorin e6 against Periodontal Pathogens

Photodynamic therapy (PDT) based periodontal disease treatment has received extensive attention. However, the deep tissue location of periodontal plaque makes the conventional PDT encounter a bottleneck. Herein, upconversion fluorescent nanomaterial with near-infrared light excitation was introduced into the treatment of periodontal disease, overcoming the limited tissue penetration depth of visible light in PDT. Photosensitizer Ce6 molecules were combined with upconversion nanoparticles (UCNPs) NaYF4:Yb,Er with a novel strategy. The hydrophobic UCNPs were modified with amphiphilic silane, utilizing the hydrophobic chain of the silane to bind to the hydrophobic groups of the UCNPs through a hydrophobic-hydrophobic interaction, and the Ce6 molecules were loaded in this hydrophobic layer. This achieves both the conversion of the hydrophobic to the hydrophilic surface and the loading of the oily photosensitizer molecules. Because the excitation position of the Ce6 molecule is in the red region, Mn ions were doped to enhance red light, and thus the improved PDT function. This Ce6 loaded UCNPs composites with efficient red upconversion luminescence show remarkable bacteriological therapeutic effect on Porphyromonas gingivalis, Prevotella intermedia and Fusobacterium nucleatum and the corresponding biofilms under 980 nm irradiation, indicating a high application prospect in the treatment of periodontal diseases.

Surface Modifications for Photon-Upconversion-Based Energy-Transfer Nanoprobes

An emerging class of inorganic optical reporters are near-infrared (NIR) excitable lanthanide-based upconversion nanoparticles (UCNPs) with multicolor emission and long luminescence lifetimes in the range of several hundred microseconds. For the design of chemical sensors and optical probes that reveal analyte-specific changes in their spectroscopic properties, these nanomaterials must be combined with sensitive indicator dyes that change their absorption and/or fluorescence properties selectively upon interaction with their target analyte, utilizing either resonance energy transfer (RET) processes or reabsorption-related inner filter effects. The rational development of UCNP-based nanoprobes for chemical sensing and imaging in a biological environment requires reliable methods for the surface functionalization of UCNPs, the analysis and quantification of surface groups, a high colloidal stability of UCNPs in aqueous media as well as the chemically stable attachment of the indicator molecules, and suitable instrumentation for the spectroscopic characterization of the energy-transfer systems and the derived nanosensors. These topics are highlighted in the following feature article, and examples of functionalized core-shell nanoprobes for the sensing of different biologically relevant analytes in aqueous environments will be presented. Special emphasis is placed on the intracellular sensing of pH.

Energy-Converting Nanomedicine

Serious side effects to surrounding normal tissues and unsatisfactory therapeutic efficacy hamper the further clinic applications of conventional cancer-therapeutic strategies, such as chemotherapy and surgery. The fast development of nanotechnology provides unprecedented superiorities for cancer therapeutics. Externally activatable therapeutic modalities mediated by nanomaterials, relying on highly effective energy transformation to release therapeutic elements/effects (cytotoxic reactive oxygen species, thermal effect, photoelectric effect, Compton effect, cavitation effect, mechanical effect or chemotherapeutic drug) for cancer therapies, categorized and termed as "energy-converting nanomedicine," have arouse considerable concern due to their noninvasiveness, desirable tissue-penetration depth, and accurate modulation of therapeutic dose. This review summarizes the recent advances in the engineering of intelligent functional nanotherapeutics for energy-converting nanomedicine, including photo-based, radiation-based, ultrasound-based, magnetic field-based, microwave-based, electric field-based, and radiofrequency-based nanomedicines, which are enabled by external stimuli (light, radiation, ultrasound, magnetic field, microwave, electric field, and radiofrequency). Furthermore, biosafety issues of energy-converting nanomedicine related to future clinical translation are also addressed. Finally, the potential challenges and prospects of energy-converting nanomedicine for future clinical translation are discussed.

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.