Biodegradable hypocrellin derivative nanovesicle as a near-infrared light-driven theranostic for dually photoactive cancer imaging and therapy

Tumor microenvironment-modulated nanoparticles with cascade energy transfer as internal light sources for photodynamic therapy of deep-seated tumors

Photodynamic therapy (PDT) is an appealing modality for cancer treatments. However, the limited tissue penetration depth of external-excitation light makes PDT impossible in treating deep-seated tumors. Meanwhile, tumor hypoxia and intracellular reductive microenvironment restrain the generation of reactive oxygen species (ROS). To overcome these limitations, a tumor-targeted self-illuminating supramolecular nanoparticle T-NPCe6-L-N is proposed by integrating photosensitizer Ce6 with luminol and nitric oxide (NO) for chemiluminescence resonance energy transfer (CRET)-activated PDT. The high H2O2 level in tumor can trigger chemiluminescence of luminol to realize CRET-activated PDT without exposure of external light. Meanwhile, the released NO significantly relieves tumor hypoxia via vascular normalization and reduces intracellular reductive GSH level, further enhancing ROS abundance. Importantly, due to the different ROS levels between cancer cells and normal cells, T-NPCe6-L-N can selectively trigger PDT in cancer cells while sparing normal cells, which ensured low side effect. The combination of CRET-based photosensitizer-activation and tumor microenvironment modulation overcomes the innate challenges of conventional PDT, demonstrating efficient inhibition of orthotopic and metastatic tumors on mice. It also provoked potent immunogenic cell death to ensure long-term suppression effects. The proof-of-concept research proved as a new strategy to solve the dilemma of PDT in treatment of deep-seated tumors.

Hypocrellin: A Natural Photosensitizer and Nano-Formulation for Enhanced Molecular Targeting of PDT of Melanoma

Nano-formulation has generated attention in the battle against cancer, because of its great flexibility, reduced adverse side effects, and accuracy in delivering drugs to target tissues dependent on the size and surface characteristics of the disease. The field of photodynamic treatment has advanced significantly in the past years. Photodynamic techniques that use nano-formulations have surfaced to further the field of nanotechnology in medicine, especially in cancer treatment. The pharmaceutical industry is seeing a growing trend toward enhanced drug formulation using nano-formulations such as liposomes, polymeric nanoparticles, dendrimers, nano-emulsions, and micelles. Natural extracts have also shown adverse effects when employed as photosensitizers in cancer therapy because they are cytotoxic when activated by light. Still, natural photosensitizers are a big part of cancer treatment. However, some shortcomings can be minimized by combining nano-formulations with these natural photosensitizers. The synergistic improvement in medication delivery that maintains or increases the mechanism of cell death in malignant cells has also been demonstrated by the combination of photodynamic therapy with nano-formulations and natural photosensitizers. Lastly, this review assesses the feasibility and potential of a photodynamic therapy system based on nano-formulations and natural photosensitizers in clinical treatment applications and briefly discusses the removal of toxic compounds associated with nano-formulations within cells.

Wireless Light‐Emitting Diode‐Driven Functional Microneedle Devices for Skin Cancer Therapy

Photodynamic therapy, a noninvasive cancer treatment strategy, is a promising remedy for malignant skin cancers. However, treatment of skin cancer with this method requires sufficient photosensitizer molecules to permeate into cancer cells before illumination for effective activation to induce potent reactive oxygen species for eliminating cancer cells. However, transdermal drug delivery using conventional photosensitizers faces major challenges due to skin barriers, diminishing the effectiveness of drug penetration and therapeutic efficacies. To overcome these limitations, biocompatible, physiologically dissolvable, and optically activatable functional microneedle devices are applied for effective percutaneous penetration of drug molecules into solid tumors in a murine model. The proposed wireless light‐emitting diode light‐driven functional microneedle device that effectively induces apoptosis of cancer cells and disruption of the tumor area and can enhance in vitro, ex vivo, and in vivo drug‐delivery effectiveness for treating skin cancer. The design and strategy of the present functional microneedle devices can help shed light on future advanced cancer therapy.

A General Strategy for Enhanced Photodynamic Antimicrobial Therapy with Perylenequinonoid Photosensitizers Using a Macrocyclic Supramolecular Carrier

Perylenequinonoid natural products are a class of photosensitizers (PSs) that exhibit high reactive oxygen species (ROS) generation and excellent activity for Type I/Type II dual photodynamic therapy. However, their limited activity against gram-negative bacteria and poor water solubility significantly restrict their potential in broad-spectrum photodynamic antimicrobial therapy (PDAT). Herein, a general approach to overcome the limitations of perylenequinonoid photosensitizers (PQPSs) in PDAT by utilizing a macrocyclic supramolecular carrier is presented. Specifically, AnBox·4Cl, a water-soluble cationic cyclophane, is identified as a universal macrocyclic host for PQPSs such as elsinochrome C, hypocrellin A, hypocrellin B, and hypericin, forming 1:1 host-guest complexes with high binding constants (≈107 m -1) in aqueous solutions. Each AnBox·4Cl molecule carries four positive charges that promote strong binding with the membrane of gram-negative bacteria. As a result, the AnBox·4Cl-PQPS complexes can effectively anchor on the surfaces of gram-negative bacteria, while the PQPSs alone cannot. In vitro and in vivo experiments demonstrate that these supramolecular PSs have excellent water solubility and high ROS generation, with broad-spectrum PDAT effect against both gram-negative and gram-positive bacteria. This work paves a new path to enhance PDAT by showcasing an efficient approach to improve PQPSs' water solubility and killing efficacy for gram-negative bacteria.

Aggregation-Induced Emission-Active Organic Nanoagent with High Photothermal Conversion Efficiency for Near-Infrared Imaging-Guided Tumor Photothermal Therapy

Photothermal therapy (PTT) provides a great prospect for noninvasive cancer therapy. However, it is still highly challenging to construct photothermal agents (PTAs) with the desired performances for imaging-guided PTT applications. Herein, a D-A-D-type naphthalene diamine (NDI)-based photothermal nano-PTAs NDS-BPN NP with near-infrared region (NIR) emission at 822 nm, aggregation-induced emission (AIE), high photothermal conversion efficiency (55.05%), and excellent photothermal stability is successfully designed and prepared through a simple two-step engineering method by using a new AIE molecule NDS-BPN and DSPE-PEG2000 as precursors. The prepared PTT nanoagents NDS-BPN NPs have been further applied for efficient photothermal ablation of cancer cells in vitro and also achieved the NIR fluorescent image-guided PTT tumor therapy in vivo with satisfactory results. We believe that this work provides an attractive NIR AIE NDI-based nano-PTA for the phototherapy of tumors as well as develops the construction strategy of NDI molecular-based photothermal nanoagents with desired performances for imaging-guided PTT.

Targeting macrophagic RasGRP1 with catechin hydrate ameliorates sepsis-induced multiorgan dysfunction

BACKGROUND

The proinflammatory response induced by macrophages plays a crucial role in the development of sepsis and the resulting multiorgan dysfunction. Identifying new regulatory targets for macrophage homeostasis and devising effective treatment strategies remains a significant challenge in contemporary research.

PURPOSE

This study aims to identify new regulatory targets for macrophage homeostasis and develop effective strategies for treating sepsis.

STUDY DESIGN AND METHODS

Macrophage infiltration in septic patients and in lungs, kidneys, and brains of caecum ligation and puncture (CLP)-induced septic mice was observed using CIBERSORT and immunofluorescence (IF). Upon integrating the MSigDB database and GSE65682 dataset, differently expressed macrophage-associated genes (DEMAGs) were identified. Critical DEMAGs were confirmed through machine learning. The protein level of the critical DEMAG was detected in PBMCs of septic patients, RAW264.7 cells, and mice lungs, kidneys, and brains using ELISA, western blot, immunohistochemistry, and IF. siRNA was applied to investigate the effect of the critical DEMAG in RAW264.7 cells. A natural product library was screened to find a compound targeting the critical DEMAG protein. The binding of compounds and proteins was analyzed through molecular docking, molecular dynamics simulations, CETSA, and MST analysis. The therapeutic efficacy of the compounds against sepsis was then evaluated through in vitro and in vivo experiments.

RESULTS

Macrophage infiltration was inversely correlated with survival in septic patients. The critical differentially expressed molecule RasGRP1 was frequently observed in the PBMCs of septic patients, LPS-induced RAW264.7 cells, and the lungs, kidneys, and brains of septic mice. Silencing RasGRP1 alleviated proinflammatory response and oxidative stress in LPS-treated RAW264.7 cells. Catechin Hydrate (CH) was identified as an inhibitor of RasGRP1, capable of maintaining macrophage homeostasis and mitigating lung, kidney, and brain damage during sepsis.

CONCLUSION

This study demonstrates that RasGRP1, a novel activator of macrophage proinflammatory responses, plays a crucial role in the excessive inflammation and oxidative stress associated with sepsis. CH shows potential for treating sepsis by inhibiting RasGRP1.

Enhancing the Photosensitivity of Hypocrellin A by Perylene Diimide Metallacage-Based Host-Guest Complexation for Photodynamic Therapy

The development of supramolecular hosts which can efficiently encapsulate photosensitizers to improve the photodynamic efficacy holds great promise for cancer therapy. Here, we report two perylene diimide-based metallacages that can form stable host-guest complexes with planar conjugated molecules including polycyclic aromatic hydrocarbons and photosensitizers (hypocrellin A). Such host-guest complexation not only prevents the aggregation of photosensitizers in aqueous environments, but also offers fluorescence resonance energy transfer (FRET) from the metallacage to the photosensitizers to further improve the singlet oxygen generation (ΦΔ = 0.66). The complexes are further assembled with amphiphilic polymers, forming nanoparticles with improved stability for anticancer study. Both in vitro and in vivo studies indicate that the nanoparticles display excellent anticancer activities upon light irradiation, showing great potential for cancer photodynamic therapy. This study provides a straightforward and effective approach for enhancing the photosensitivity of conventional photosensitizers via host-guest complexation-based FRET, which will open a new avenue for host-guest chemistry-based supramolecular theranostics.

Tumor Microenvironment-Activatable Phototheranostic: Leveraging Nitric Oxide and Weak Acidity as Dual Biomarkers for Ratiometric Fluorescence, Photoacoustic Imaging, and Photothermal Therapy

Tumor microenvironment-responsive phototheranostic agents are highly sought after for their ability to improve diagnostic accuracy and treatment specificity. Here, we introduce a novel single-molecule probe, POZ-NO, which is activated by nitric oxide (NO) and weak acidity, enabling dual-mode imaging and photothermal therapy (PTT) of tumors. In acidic environments with elevated NO levels, POZ-NO exhibits a distinctive ratiometric fluorescence signal shift from the red to near-infrared, accompanied by a 700 nm photoacoustic signal. Additionally, POZ-NO demonstrated potent photothermal effects upon NO and acidity activation, achieving an impressive conversion efficiency of 74.3% under 735 nm laser irradiation. In vivo studies confirm POZ-NO's ability to accurately image tumors through ratiometric fluorescence and photoacoustic modes while selectively treating tumors with PTT.

Engineered cell membrane-coated nanoparticles based cancer therapy: A robust weapon against the lethal and challenging hepatocellular carcinoma

Hepatocellular carcinoma (HCC) has become an important public health problem, and there are still challenges to overcome in clinical treatment. The nanodrug delivery system (NDDS) has developed tremendously in recent years, and many researchers have explored NDDS for the treatment of HCC. Engineered cell membrane-coated nanoparticles (ECNPs) have emerged, combining the unique functions of cell membranes with the engineering versatility of synthetic nanoparticles (NPs) to effectively deliver therapeutic drugs. It is designed to have the capabilities: specific active targeting, immune evasion, prolonging the circulation blood time, controlled drug release delivery, and reducing drugs systematic toxicity. Thus, ECNPs are a promising bionic tool in the treatment of HCC and have operability to achieve combination and integrated therapy. This review focuses on the mechanism and strategy of ECNPs for the treatment of HCC and summarizes its research progress in the treatment of HCC in recent years.

Visualizing intracellular membrane interactions and cell type-specific differentiation in ferroptosis and apoptosis with Boranil-Carbazole derivative

Intracellular lipid systems play essential roles in various physiological functions and cell growth processes. However, our understanding of the intricate interactions within this system, especially between mitochondria and lipid droplets, is limited, particularly in the context of cancer cells' altered lipid metabolism. To address this, our study introduces an N-B-O BODIPY-hexylcarbazole derivative, named Cz-Boranil, that sets a new benchmark in visualizing these critical interactions. Cz-Boranil's unique capability lies in its ability to display distinct intracellular distribution patterns in both normal and cancer cells, offering nuanced cell type-specific differentiation. More impressively, this probe tracks the coordinated interactions of lipid droplets and mitochondria during the critical processes of ferroptosis and apoptosis. We believe that the innovative capabilities of Cz-Boranil will revolutionize our understanding of intracellular lipid interactions and prove pivotal in identifying and studying cancerous cells.

Optimisation of hypocrellin production in Shiraia-like fungi via genetic modification involving a transcription factor gene and a putative monooxygenase gene

Shiraia-like fungi, which are rare parasitic fungi found around bamboo, play an important role in traditional medicine. Their main active component, hypocrellin, is widely used in medicine, food, and cosmetics. By comparing strains with different hypocrellin yields, we identified a transcription factor (SbTF) in the hypocrellin biosynthesis pathway. SbTF from high-yielding zzz816 and low-yielding CNUCC C72 differed in its protein structure. Subsequently, SbTF from high-yielding zzz816 was overexpressed in several strains. This stabilised the yield in zzz816 and significantly increased the yield in low-yielding CNUCC C72. Comparing downstream non-essential genes between wild type and SbTF-overexpressing CNUCC C72 showed that SbMNF was significantly up-regulated. Therefore, it was selected for further study. SbMNF overexpression increased the hypocrellin yield in low-yielding CNUCC C72 and altered the composition of compounds in high-yielding CNUCC 1353PR and zzz816. This involved an increased elsinochrome C yield in CNUCC 1353PR and an increased hypocrellin B yield in zzz816 (by 2 and 70.3 times that in the corresponding wild type, respectively). This study is the first to alter hypocrellin synthesis to alter the levels of one bioactive agent compared to another. The results provide new insights regarding genetic modification and will help to optimise fungal fermentation.

pH-Responsive NIR-II phototheranostic agents for in situ tumor vascular monitoring and combined anti-vascular/photothermal therapy

Developing nanoplatforms integrating superior fluorescence imaging ability in second near-infrared (NIR-II) window and tumor microenvironment responsive multi-modal therapy holds great potential for real-time feedback of therapeutic efficacy and optimizing tumor inhibition. Herein, we developed a pH-sensitive pyrrolopyrrole aza-BODIPY-based amphiphilic molecule (PTG), which has a balanced NIR-II fluorescence brightness and photothermal effect. PTG is further co-assembled with a vascular disrupting agent (known as DMXAA) to prepare PTDG nanoparticles for combined anti-vascular/photothermal therapy and real-time monitoring of the tumor vascular disruption. Each PTG molecule has an active PT-3 core which is linked to two PEG chains via pH-sensitive ester bonds. The cleavage of ester bonds in the acidic tumor environment would tricker releases of DMXAA for anti-vascular therapy and further assemble PT-3 cores into micrometer particles for long term monitoring of the tumor progression. Furthermore, benefiting from the high brightness in the NIR-II region (119.61 M-1 cm-1) and long blood circulation time (t1/2 = 235.6 min) of PTDG nanoparticles, the tumor vascular disrupting process can be in situ visualized in real time during treatment. Overall, this study demonstrates a self-assembly strategy to build a pH-responsive NIR-II nanoplatform for real-time monitoring of tumor vascular disruption, long-term tracking tumor progression and combined anti-vascular/photothermal therapy.

Pyrrolopyrrole aza-BODIPY-based NIR-II fluorophores for in vivo dynamic vascular dysfunction visualization of vascular-targeted photodynamic therapy

Real-time monitoring vascular responses is crucial for evaluating the therapeutic effects of vascular-targeted photodynamic therapy (V-PDT). Herein, we developed a highly-stable and bright aggregation induced emission (AIE) fluorophore (PTPE3 NP) for dynamic fluorescence (FL) imaging of vascular dysfunction beyond 1300 nm window during V-PDT. The superior brightness (ϵ_maxΦ_{f>1000 nm} ≈ 180.05 M^-1 cm^-1) and high resolution of PTPE3 NP affords not only high-clarity images of whole-body and local vasculature (hindlimbs, mesentery, and tumor) but also high-speed video imaging for tracking blood circulation process. By virtue of the NPs' prolonged blood circulation time (t_1/2 ≈ 86.5 min) and excellent photo/chemical (pH, RONS) stability, mesenteric and tumor vascular dysfunction (thrombosis formation, vessel occlusion, and hemorrhage) can be successfully visualized during V-PDT by FL imaging for the first time. Furthermore, the reduction of blood flow velocity (BFV) can be monitored in real time for precisely evaluating efficacy of V-PDT. These provide a powerful approach for assessing vascular responses during V-PDT and promote the development of advanced fluorophores for biological imaging.

Photosensitive pro-drug nanoassemblies harboring a chemotherapeutic dormancy function potentiates cancer immunotherapy

Immunotherapy combined with effective therapeutics such as chemotherapy and photodynamic therapy have been shown to be a successful strategy to activate anti-tumor immune responses for improved anticancer treatment. However, developing multifunctional biodegradable, biocompatible, low-toxic but highly efficient, and clinically available transformed nano-immunostimulants remains a challenge and is in great demand. Herein, we report and design of a novel carrier-free photo-chemotherapeutic nano-prodrug COS-BA/Ce6 NPs by combining three multifunctional components-a self-assembled natural small molecule betulinic acid (BA), a water-soluble chitosan oligosaccharide (COS), and a low toxic photosensitizer chlorin e6 (Ce6)-to augment the antitumor efficacy of the immune adjuvant anti-PD-L1-mediated cancer immunotherapy. We show that the designed nanodrugs harbored a smart and distinctive "dormancy" characteristic in chemotherapeutic effect with desired lower cytotoxicity, and multiple favorable therapeutic features including improved 1O2 generation induced by the reduced energy gap of Ce6, pH-responsiveness, good biodegradability, and biocompatibility, ensuring a highly efficient, synergistic photochemotherapy. Moreover, when combined with anti-PD-L1 therapy, both nano-coassembly based chemotherapy and chemotherapy/photodynamic therapy (PDT) could effectively activate antitumor immunity when treating primary or distant tumors, opening up potentially attractive possibilities for clinical immunotherapy.

Supramolecular photosensitizers using extended macrocyclic hosts for photodynamic therapy with distinct cellular delivery

Two hydrophilic macrocycles can strongly bind hypocrellin B. The resulting supramolecular photosensitizers show excellent photodynamic efficiency with different cellular delivery.

Advances and perspectives on perylenequinone biosynthesis

Under illumination, the fungal secondary metabolites, perylenequinones (PQs) react with molecular oxygen to generate reactive oxygen species (ROS), which, in excess can damage cellular macromolecules and trigger apoptosis. Based on this property, PQs have been widely used as photosensitizers and applied in pharmaceuticals, which has stimulated research into the discovery of new PQs and the elucidation of their biosynthetic pathways. The PQs-associated literature covering from April 1967 to September 2022 is reviewed in three sections: (1) the sources, structural diversity, and biological activities of microbial PQs; (2) elucidation of PQ biosynthetic pathways, associated genes, and mechanisms of regulation; and (3) advances in pathway engineering and future potential strategies to modify cellular metabolism and improve PQ production.

Preparation of oxime compound lipid droplet-specifically labeled fluorescent probe and its application in cell imaging

Fluorescent probes can facilitate our further comprehension of the functional and physiological roles of LDs and thus promote the development of effective therapeutic approaches. Oxime compounds are widely used due to their good crystallinity and high reactivity. However, the majority oximes fluorescent probes are usually employed for the detection of HCIO, and the application of oximes in fluorescently labeled LD_S is poorly reported. In this paper, three kinds of LDs fluorescent probes (NAP-a, NAP-b and NAP-c) with D-π-A structure were synthesized by simple synthesis method with 1,8-naphthalimide as fluorescent matrix and oxime group as electron donor. These probes were highly sensitive to polarity, and possessed good photostability and low cytotoxicity. Co-staining experiments showed that these probes could target LDs and the fluorescence image was green. These probes NAP-a, NAP-b and NAP-c possessed high Pearson coefficient (HeLa cells: 0.91, 0.95, 0.86) and Manders coefficient (HeLa cells: 0.91, 0.96, 0.86) with Nile Red. Interestingly, the dynamic variations in their size, shape and distribution could be clearly observed in the oleic acid-treated cell model of LDs. Imaging of zebrafish was performed and green fluorescence was collected in zebrafish. These excellent properties make oxime compound fluorescent probes a promising fluorescent probes for studying LDs and metabolic diseases. This study opens up a new way for the preparation of LDs fluorescent probe.

GPR37 promotes cancer growth by binding to CDK6 and represents a new theranostic target in lung adenocarcinoma

Lung adenocarcinoma (LUAD) is associated with poor prognosis. Identifying novel cancer targets and helpful therapeutic strategies remains a serious clinical challenge. This study detected differentially expressed genes in The Cancer Genome Atlas (TCGA) LUAD data collection. We also identified a predictive DNA biomarker, G protein-coupled receptor 37 (GPR37), which was verified as a prognostic biomarker with a critical role in tumor progression. In human LUAD specimens and microarray analyses, we determined that GPR37 was significantly upregulated and associated with a poor prognosis. GPR37 downregulation markedly inhibited the proliferation and migration of LUAD both in vitro and in vivo. Mechanistically, GPR37 could bind to CDK6, thereby facilitating tumor progression in LUAD by inducing cell cycle arrest at the G1 phase. GPR37 also facilitates tumorigenesis in xenograft tumors in vivo. High-throughput screening for GPR37-targeted drugs was performed using the Natural Products Library, which revealed the potential of Hypocrellin B to inhibit GPR37 and cell growth in LUAD. We demonstrated that Hypocrellin B suppressed LUAD cell proliferation and migration both in vitro and in vivo via GPR37 inhibition. Collectively, our findings reveal the role of GPR37 in LUAD progression and migration and the potential of GPR37 as a target for the treatment of LUAD. Thus, the specific inhibition of GPR37 by the natural product Hypocrellin B may possess the potential for the treatment of LUAD.

Recent Progress Toward Imaging Application of Multifunction Sonosensitizers in Sonodynamic Therapy

Sonodynamic therapy (SDT) is a rapidly developing non-surgical therapy that initiates sensitizers’ catalytic reaction using ultrasound, showing great potential for cancer treatment due to its high safety and non-invasive nature. In addition, recent research has found that using different diagnostic and therapeutic methods in tandem can lead to better anticancer outcomes. Therefore, as essential components of SDT, sonosensitizers have been extensively explored to optimize their functions and integrate multiple medical fields. The review is based on five years of articles evaluating the combined use of SDT and imaging in treating cancer. By developing multifunctional sonosensitive particles that combine imaging and sonodynamic therapy, we have integrated diagnosis into the treatment of precision medicine applications, improving SDT cell uptake and antitumor efficacy utilizing different tumour models. This paper describes the imaging principle and the results of cellular and animal imaging of the multifunctional sonosensitizers. Efforts are made in this paper to provide data and design references for future SDT combined imaging research and clinical application development and to provide offer suggestions.

NIR-I Dye-Based Probe: A New Window for Bimodal Tumor Theranostics

Near-infrared (NIR, 650-1700 nm) bioimaging has emerged as a powerful strategy in tumor diagnosis. In particular, NIR-I fluorescence imaging (650-950 nm) has drawn more attention, benefiting from the high quantum yield and good biocompatibility. Since their biomedical applications are slightly limited by their relatively low penetration depth, NIR-I fluorescence imaging probes have been under extensive development in recent years. This review summarizes the particular application of the NIR-I fluorescent dye-contained bimodal probes, with emphasis on related nanoprobes. These probes have enabled us to overcome the drawbacks of individual imaging modalities as well as achieve synergistic imaging. Meanwhile, the application of these NIR-I fluorescence-based bimodal probes for cancer theranostics is highlighted.

Exogenous Contrast Agents in Photoacoustic Imaging: An In Vivo Review for Tumor Imaging

The field of cancer theranostics has grown rapidly in the past decade and innovative 'biosmart' theranostic materials are being synthesized and studied to combat the fast growth of cancer metastases. While current state-of-the-art oncology imaging techniques have decreased mortality rates, patients still face a diminished quality of life due to treatment. Therefore, improved diagnostics are needed to define in vivo tumor growths on a molecular level to achieve image-guided therapies and tailored dosage needs. This review summarizes in vivo studies that utilize contrast agents within the field of photoacoustic imaging-a relatively new imaging modality-for tumor detection, with a special focus on imaging and transducer parameters. This paper also details the different types of contrast agents used in this novel diagnostic field, i.e., organic-based, metal/inorganic-based, and dye-based contrast agents. We conclude this review by discussing the challenges and future direction of photoacoustic imaging.

Optical properties of natural small molecules and their applications in imaging and nanomedicine

Natural small molecules derived from plants have fascinated scientists for centuries due to their practical applications in various fields, especially in nanomedicine. Some of the natural molecules were found to show intrinsic optical features such as fluorescence emission and photosensitization, which could be beneficial to provide spatial temporal information and help tracking the drugs in biological systems. Much efforts have been devoted to the investigation of optical properties and practical applications of natural molecules. In this review, optical properties of natural small molecules and their applications in fluorescence imaging, and theranostics will be summarized. First, we will introduce natural small molecules with different fluorescence emission, ranging from blue to near infrared emission. Second, imaging applications in biological samples will be covered. Third, we will discuss the applications of theranostic nanomedicines or drug delivering systems containing fluorescent natural molecules acting as imaging agents or photosensitizers. Finally, future perspectives in this field will be discussed.

Pure photosensitizer-driven nanoassembly with core-matched PEGylation for imaging-guided photodynamic therapy

Pure drug-assembled nanomedicines (PDANs) are currently under intensive investigation as promising nanoplatforms for cancer therapy. However, poor colloidal stability and less tumor-homing ability remain critical unresolved problems that impede their clinical translation. Herein, we report a core-matched nanoassembly of pyropheophorbide a (PPa) for photodynamic therapy (PDT). Pure PPa molecules are found to self-assemble into nanoparticles (NPs), and an amphiphilic PEG polymer (PPa-PEG_2K) is utilized to achieve core-matched PEGylating modification via the π‒π stacking effect and hydrophobic interaction between the PPa core and the PPa-PEG_2K shell. Compared to PCL-PEG_2K with similar molecular weight, PPa-PEG_2K significantly increases the stability, prolongs the systemic circulation and improves the tumor-homing ability and ROS generation efficiency of PPa-nanoassembly. As a result, PPa/PPa-PEG_2K NPs exert potent antitumor activity in a 4T1 breast tumor-bearing BALB/c mouse xenograft model. Together, such a core-matched nanoassembly of pure photosensitizer provides a new strategy for the development of imaging-guided theragnostic nanomedicines.

Amphiphilic Diketopyrrolopyrrole Derivatives for Efficient Near-Infrared Fluorescence Imaging and Photothermal Therapy

The design and synthesis of single-molecule amphiphilic and multifunctional phototherapeutic agents are important to cancer diagnosis and therapy. In this work, we developed three amphiphilic diketopyrrolopyrrole derivatives (TPADPP, DTPADPP, and TPADDPP) with different donor-acceptor structures and poly(ethylene glycol) side chains. The corresponding nanoparticles (NPs) were obtained via a self-assembly from three amphiphilic DPP derivatives and used as smart phototherapeutic agents for tumor diagnosis and treatment. The three amphiphilic DPP NPs exhibited near-infrared (NIR) emissions and good biocompatibility. Thus, they could be used as fluorescence (FL) imaging agents for guided therapy. DTPADPP NPs and TPADDPP NPs also displayed excellent photothermal performance and high accumulation in the tumor. Owing to these beneficial features, the DTPADPP NPs and TPADDPP NPs synthesized herein are suitable for NIR FL imaging and effective photothermal therapy against the tumor in vivo.

Biodegradable Hypocrellin B nanoparticles coated with neutrophil membranes for hepatocellular carcinoma photodynamics therapy effectively via JUNB/ROS signaling

Hepatocellular carcinoma (HCC) is an inflammation-induced and chemotherapy-resistant common liver cancer, and a major cause of death. Some natural products have been found to be used as photosensitizers in photodynamic therapy of HCC. Due to its specific molecular structure diversities and biological activities, current status of HCC treatment with nature production remains unsatisfactory, owing largely to the toxicity, side effect and inefficiency to drug targeting. Herein, we show a nanoparticle-based broad-spectrum anti-inflammatory strategy that naïve neutrophil membrane-coated PLGA nanoparticles (NM-HB NPs) were constructed for synchronous nearinfrared fluorescence (NIR FL) imaging and photodynamic therapy (PDT) for HCC. Moreover, NM-HB NPs inhibited the expression of JUNB and promoted the ROS production. JUNB depletion enhanced the anti-HCC effect of NM-HB NPs. Importantly, it was shown that NM-HB NPs are well targeted to the tumor site and overcomes the blood circulation and immune elimination in vivo and vitro. In a mouse model of HCC, the neutrophil membrane-coated nanoparticles (NM-HB NPs) show significant therapeutic efficacy by PDT and suppressing tumor tissue increase. All results demonstrated that NM coated HB NPs representing a viable and effective treatment option for HCC.

Two-Color Visualization of Cholesterol Fluctuation in Plasma Membranes by Spatial Distribution-Controllable Single Fluorescent Probes

Visualizing cholesterol (CL) fluctuation in plasma membranes is a crucially important yet challenging task in cell biology. Here, we proposed a new imaging strategy based on permeability changes of plasma membranes triggered by different CL contents to result in controllable spatial distribution of single fluorescent probes (SF-probes) in subcellular organelles. Three spatial distribution-controllable SF-probes (PMM-Me, PMM-Et, and PMM-Bu) for imaging CL fluctuation in plasma membranes were rationally developed. These SF-probes target plasma membranes and mitochondria at normal CL levels, while they display solely staining in plasma membranes and mitochondria at increased and decreased CL levels, respectively. These polarity-sensitive probes also show distinct emission colors with fluorescence peaks of 575 and 620 nm in plasma membranes and mitochondria, respectively. Thus, the CL fluctuation in plasma membranes can be clearly visualized by means of the spatially distributed and two-color emissive SF-probes.

A Single Fluorescent pH Probe for Simultaneous Two-Color Visualization of Nuclei and Mitochondria and Monitoring Cell Apoptosis

Subcellular organelles play indispensable roles in diverse biological processes by their precise mutual cooperation. Thus, the development of a single fluorescent probe (SF-probe) for simultaneous and discriminable visualization of different organelles and their dynamics during certain bioprocess is significant, yet remains greatly challenging. Herein, for the first time, we rationally prepared a pH-sensitive SF-probe (named HMBI) for the simultaneous two-color visualization of nuclei and mitochondria and monitoring cell apoptosis. HMBI shows remarkable ratiometric fluorescence changes toward pH changes. Due to different pH environments in subcellular organelles, HMBI can image nuclei and mitochondria with green and red emission, respectively. HMBI can monitor drug-induced cell apoptosis with dramatically decreased red emission in mitochondria but almost unchanged green emission in nuclei, and the shrinking and pyknotic nuclei are also observed during cell apoptosis. HMBI possesses tremendous potential in two-color biomedical imaging of the dynamic changes of nuclei and mitochondria in many physiological processes.

Charge-Dependent Strategy Enables a Single Fluorescent Probe to Study the Interaction Relationship between Mitochondria and Lipid Droplets

Cooperation between organelles is essential to maintain the normal operation of the cell. A lipid droplet (LD), a dynamic organelle, is specialized in lipid storage and can interact physically with mitochondria in several cell types. However, an appropriate method for in situ studying the interaction relationships of mitochondria-LDs is still lacking. Herein, a charge-dependent strategy is proposed for the first time by considering adequately the charge difference between mitochondria and LDs. According to the novel strategy, we have developed a unique fluorescent probe Mito-LD based on the cyclization and ring-opening conversion. Mito-LD could simultaneously stain mitochondria and LDs and emit a red and green fluorescence, respectively. More importantly, with the probe Mito-LD, the in situ interaction relationships of mitochondria-LDs were investigated in detail from LD accumulation, mitochondrial dysfunction, lower environmental temperatures, and four aspects of apoptosis. The experimental results showed that mitochondria played an important role in LD accumulation, and the numbers and size of LDs would increase after mitochondrial dysfunction that may be due to excess liposomes. In addition, as an energy storage organelle, LDs played an important role in helping to coordinate mitochondrial energy supply in response to cold. In addition, the Mito-LD revealed that the polarity of mitochondria was higher than that of LDs. In a word, the probe Mito-LD could serve as a potential tool for further exploring mitochondria-LD interaction mechanisms, and importantly, the charge-dependent strategy is valuable for designing robust new probes in imaging multiple organelles.

Ultrasound-Enhanced Self-Exciting Photodynamic Therapy Based on Hypocrellin B

Peroxalate CL as an energy source to excite photosensitizers has attracted tremendous attention in photodynamic therapy (PDT). In this work, peroxyoxalate CPPO and hypocrellin B (HB)-based nanoparticles (CBNPs) for ultrasound (US)-enhanced self-exciting PDT were designed and prepared. CBNPs showed an excellent therapeutic effect against cancer cells with the assistance of US. This US-enhanced-chemiluminescence system avoids the dependence on external light and provides an example for inspiring more effective and precise strategies for cancer treatment.

Does the chemistry of fungal pigments demand the existence of photoactivated defense strategies in basidiomycetes?

The well-known photosensitizers hypericin, harmane, and emodin are typical pigments of certain mushroom species-is this a coincidence or an indication towards a photoactivated defense mechanism in the phylum Basidiomycota? This perspective article explores this hypothesis by cross-linking the chemistry of fungal pigments with structural requirements from known photosensitizers and insights from photoactivated strategies in the kingdom Plantae. Thereby, light is shed on a yet unexplored playground dealing with ecological questions, photopharmaceutical opportunities, and biotechnological potentials.

Near-Infrared Hypocrellin Derivatives for Synergistic Photodynamic and Photothermal Therapy

Hypocrellin B (HB) derived from naturally produced hypocrellins has attracted considerable attention in photodynamic therapy (PDT) because of its excellent photosensitive properties. However, the weak absorption within a "phototherapy window" (600-900 nm) and poor water solubility of HB have limited its clinical application. In this study, two HB derivatives (i. e., HE and HF) were designed and synthesized for the first time by introducing two different substituent groups into the HB structure. The obtained derivatives showed a broad absorption band covering the near-infrared (NIR) region, NIR emission (peaked at 805 nm), and singlet oxygen quantum yields of 0.27/0.31. HE-PEG-NPs were also prepared using 2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethyleneglycol)-2000] (DSPE-mPEG2000) to achieve excellent dispersion in water and further explored their practical applications. HE-PEG-NPs not only retained their ¹ O₂ -generating ability, but also exhibited a photothermal conversion efficiency of 25.9%. In vitro and in vivo therapeutic results revealed that the synergetic effect of HE-PEG-NPs on PDT and photothermal therapy (PTT) could achieve a good performance. Therefore, HE-PEG-NPs could be regarded as a promising phototheranostic agent.

Recent advances in theranostic agents based on natural products for photodynamic and sonodynamic therapy

The integration of diagnosis and therapy based on natural products has been receiving considerable attention in recent years because nature can contribute many fantastic functional molecules with good biocompatibility and low toxicity. Diagnostic and therapeutic agents combined with the technique of photodynamic therapy (PDT) and sonodynamic therapy (SDT) have been extensively developed thanks to the advantages of PDT and SDT, such as good selectivity, low toxicity, and noninvasive treatment for cancers and other diseases compared with traditional treatments. In this review, we summarize the recent advances in theranostic agents for natural products categorized as porphyrins, perylenequinone, curcumin, and others. Some representative examples of disease diagnosis in fluorescence/photoacoustic imaging and disease treatment in PDT/SDT were introduced. Potential limitations and future perspectives of these natural products for theranostic agents were also discussed.

Hypocrellin-Based Multifunctional Phototheranostic Agent for NIR-Triggered Targeted Chemo/Photodynamic/Photothermal Synergistic Therapy against Glioblastoma

A huge challenge exists in the diagnosis and treatment of malignant glioblastoma (GBM) due to the presence of the blood-brain barrier (BBB). Herein, a multifunctional phototheranostic agent is designed on the basis of an octadecane-modified temozolomide (TMZ-C18) for chemotherapy, a dicysteamine-modified hypocrellin derivative (DCHB) as a natural-origin photosensitizer with a singlet oxygen (¹O₂) quantum yield of 0.51, and a cyclic peptide (cRGD) as a targeting unit against glioblastoma. Co-encapsulated DCHB and TMZ-C18 assembly with cRGD decoration, referred to as DTRGD NPs, shows a wide absorption at the NIR region peaked at 703 nm, an NIR emission peak at 720 nm, good photostability, high photothermal conversion efficiency (33%), and effective degradation of TMZ-C18. More importantly, DTRGD NPs can efficiently break through the blood-brain barrier and enrich in the orthotopic glioblastoma. The treatment of subcutaneous U87MG tumor beard mice demonstrates that DTRGD NPs present remarkable anticancer efficiency and the targeted chemo/photodynamic/photothermal synergistic therapy can be achieved with almost no toxicity. This multifunctional phototheranostic agent shows great potential for the diagnosis and treatment of glioblastoma.

The investigation of unique water-soluble heptamethine cyanine dye for use as NIR photosensitizer in photodynamic therapy of cancer cells

In this paper, a unique water-soluble heptamethine cyanine dye as NIR photosensitizer was synthesized to explore its properties associated with potential applications in photodynamic therapy (PDT). In the strategy of designing this photosensitizer, a sulfonic acid was used as a water soluble functional group and linked to the fluorophore through alkyl chains. 4-amino-2,2,6,6-tetramethylpiperidine-N-oxyl(Tempo) moiety was used as the a nitroxide spin label in obtaining biochemical reaction information in vivo due to it could greatly increase the inter-system crossing (ISC) process for triplet-state photosensitizers and low toxicity. As expected, the photosensitizers performed well in vitro photodynamic therapy. There were a remarkable absorbance band located at 692 nm and emission peaks falls at 762 nm, the quantum yield (Φ_f) was calculated to be 12.12% in pure aqueous solution using ICG as standards. The photosensitizer also has high singlet oxygen quantum yield (Φ_△) for 16.96% with NIR LED irradiation. This photosensitizer can rapidly produce singlet oxygen and exhibit high phototoxicity under NIR light irradiation. It has excellent cellular uptake ability and better cell compatibility. It was also successfully applied in Near-infrared fluorescence imaging and AO/EB staining. In a whole, the organic dye based on Heptamethine cyanine used as photosensitizer has great potential in vivo cancer treatment.

Biodegradable Inorganic Nanoparticles for Cancer Theranostics: Insights into the Degradation Behavior

Inorganic nanoparticles as a versatile nanoplatform have been broadly applied in the diagnosis and treatment of cancers due to their inherent superior physicochemical properties (including magnetic, thermal, optical, and catalytic performance) and excellent functions (e.g., imaging, targeted delivery, and controlled release of drugs) through surface functional modification or ingredient dopant. However, in practical biological applications, inorganic nanomaterials are relatively difficult to degrade and excrete, which induces a long residence time in living organisms and thus may cause adverse effects, such as inflammation and tissue cysts. Therefore, the development of biodegradable inorganic nanomaterials is of great significance for their biomedical application. This Review will focus on the recent advances of degradable inorganic nanoparticles for cancer theranostics with highlight on the degradation mechanism, aiming to offer an in-depth understanding of degradation behavior and related biomedical applications. Finally, key challenges and guidelines will be discussed to explore biodegradable inorganic nanomaterials with minimized toxicity issues, facilitating their potential clinical translation in cancer diagnosis and treatment.

Natural-Origin Hypocrellin-HSA Assembly for Highly Efficient NIR Light-Responsive Phototheranostics against Hypoxic Tumors

Tumor hypoxia severely limits the therapeutic efficacy of solid tumors in photodynamic therapy. One strategy is to develop photosensitizers with simultaneously high efficiency in photodynamic (PDT) and photothermal therapies (PTT) in a single natural-origin phototheranostic agent to overcome this problem. However, less attention has been paid to the natural-origin phototheranostic agent with high PDT and PTT efficiencies even though they have negligible side effects and are environmentally sustainable in comparison with many reported phototheranostic agents. In addition, almost all clinical applied photosensitizers are of natural origin so far. Herein, we synthesized a natural product-based hypocrellin derivative (AETHB), with a high singlet oxygen quantum yield of 0.64 as an efficient photosensitizer different from commercially available porphyrin-based photosensitizers. AETHB is further assembled with human serum albumin to construct nanoparticles (HSA-AETHB NPs) with a high photothermal conversion efficiency (more than 50%). As-prepared HSA-AETHB NPs have shown good water solubility and biocompatibility, pH and light stability, wide absorption (400-750 nm), and NIR emission centered at 710 nm. More importantly, HSA-AETHB NPs can be applied for fluorescent/photoacoustic dual-mode imaging and simultaneously highly efficient PDT/PTT in hypoxic solid tumors. Therefore, this natural-origin multifunctional phototheranostic agent is showing very promising for effective, precise, and safe cancer therapy in clinical applications.

Harnessing the Power of Optical Microscopic and Macroscopic Imaging for Natural Products as Cancer Therapeutics

Natural products (NPs) are an important source for new drug discovery over the past decades, which have been demonstrated to be effectively used in cancer prevention, treatment, and adjuvant therapy. Many methods, such as the genomic and metabolomic approaches, immunochemistry, mass spectrometry, and chromatography, have been used to study the effects of NPs on cancer as well as themselves. Because of the advantages in specificity, sensitivity, high throughput, and cost-effectiveness, optical imaging (OI) approaches, including optical microscopic imaging and macroscopic imaging techniques have also been applied in the studies of NPs. Optical microscopic imaging can observe NPs as cancer therapeutics at the cellular level and analyze its cytotoxicity and mechanism of action. Optical macroscopic imaging observes the distribution, metabolic pathway, and target lesions of NPs in vivo, and evaluates NPs as cancer therapeutics at the whole-body level in small living animals. This review focuses on the recent advances in NPs as cancer therapeutics, with particular emphasis on the powerful use of optical microscopic and macroscopic imaging techniques, including the studies of observation of ingestion by cells, anticancer mechanism, and in vivo delivery. Finally, we prospect the wider application and future potential of OI approaches in NPs as cancer therapeutics.