Although organic photothermal agents (PTAs) have been extensively studied in preclinical cancer photothermal therapy (PTT), the internal mechanism, particularly the impact of side chains on photothermal performance, remains inadequately investigated. Herein, we conducted a systematic comparison of the photothermal properties between two organic molecules, namely O-IDTBR with four n-octyl chains and EH-IDTBR with four 2-ethylhexyl chains. With the same conjugated main structure, both O-IDTBR and EH-IDTBR exhibited nearly identical absorption properties (with a peak at 629 nm) in their molecular states. Interestingly, after the formation of nanoparticles (NPs), O-IDTBR NPs with linear alkyl chains exhibit a further red-shifted absorption onset (peak at 711 nm) compared to EH-IDTBR NPs (peak at 662 nm) with branched alkyl chains. Additionally, the photothermal conversion efficiency of O-IDTBR NPs was calculated of 33.7%, which is higher than that of EH-IDTBR NPs (27.7%). This can be attributed to the fact that linear alkyl chains of O-IDTBR NPs promote more intramolecular motions at the aggregated state by extending intermolecular distance and distorting molecular conformation. Therefore, the nonradiative thermal deactivation-induced photothermal property can be further enhanced. Through both in vitro and in vivo experiments, O-IDTBR NPs exhibit effective PTT effect and excellent biocompatibility. This study not only introduces a novel PTA but also opens new avenues for exploring organic optical nano-agents through side-chain engineering to adjust intramolecular motions at the aggregated state.

Phototherapy not only eliminates local tumors through laser irradiation but also induces systemic immune responses against recurrent and metastatic tumors, thereby enhancing anti-tumor immunity and promoting the development of immune memory. In recent years, photoimmunotherapy (PIT) that combines phototherapy and immunotherapy has emerged as a novel cancer treatment strategy. In this review, we focus on the diverse functional nanomaterials that have been employed in cancer PIT, elaborate on the mechanism of phototherapy induced immunogenic cell death (ICD), and discuss the therapeutic potential of various functional materials in PIT. Subsequently, we extensively explore the synergistic effects of PIT with other therapeutic modalities. Finally, we provide a comprehensive overview of the current clinical applications of PIT, and discuss the challenges and prospects associated with functional nanomaterials in potential clinical applications.

Croconic acid (CA), an organic pseudo-oxocarbon molecule with a highly strong electron-withdrawing character, can efficiently react with electron-rich groups and form a donor-acceptor-donor (D-A-D) con-jugated structure. CA-based molecules have excellent photobleaching resistance, thermal stability, high molar absorption coefficient, and favorable spectral tunability. Consequently, the development of CA -based functional materials in various biomedical applications is significant for potential clinical transfor-mation. Herein, we thoroughly review the development of CA-based near-infrared (NIR) materials in biomedical fields. Primarily, we introduce the rational structure design of CA molecules for excellent NIR optical properties, and the formation of CA dye-based nanomaterials for better bioavailability and stability. Subsequently, the biomedical applications such as photothermal therapy, photoacoustic imag-ing, phototheranostics, and multimodal treatment of CA-based functional materials are summarized. Finally, the perspectives and potential drawbacks of CA-based materials for future clinical transformation are systematically discussed.(c) 2022 Elsevier B.V. All rights reserved.

Triple-negative breast cancer (TNBC) possesses special biological behavior and clinicopathological characteristics, which is highly invasive and propensity to metastasize to lymph nodes, leading to a worse prognosis than other types of breast cancer. Thus, the development of an effective therapeutic method is significant to improve the survival rate of TNBC patients. In this work, a liposome-based theranostic nanosystem (ILA@Lip) was successfully prepared by simultaneously encapsulating IR 780 as the photosensitizer and lenvatinib as an anti-angiogenic agent, together with banoxantrone (AQ4N) molecule as the hypoxia-activated prodrug. The ILA@Lip can be applied for the near-infrared (NIR) fluorescence diagnostic imaging of TNBC and its lymph node metastasis for multimodal therapy. Lenvatinib in ILA@Lip can inhibit angiogenesis by cutting oxygen supply, thereby leading to enhanced hypoxia levels. Meanwhile, large amounts of reactive oxygen species (ROS) were produced while IR 780 was irradiated by an 808 nm laser, which also rapidly exhausted oxygen in tumor cells to worsen tumor hypoxia. Through creating an extremely hypoxic in TNBC, the conversion of non-toxic AQ4N to toxic AQ4 was much more efficiency for hypoxia-activated chemotherapy. Cytotoxicity assay of ILA@Lip indicated excellent biocompatibility with normal cells and tissues, but showed high toxicity in hypoxic breast cancer cells. Also, the in vivo tumors treated by the ILA@Lip with laser irradiation were admirably suppressed in both subcutaneous tumor model and orthotopic tumor models. Utilizing ILA@Lip is a profound strategy to create an extremely hypoxic tumor microenvironment for higher therapeutic efficacy of hypoxia-activated chemotherapy, which realized collective suppression of tumor growth and has promising potential for clinical translation.

Currently, clinical photothermal therapy (PTT) is greatly limited by the poor tissue penetration of the excitation light sources in visible (390–780 nm) and first near‐infrared (NIR‐I, 780–900 nm) window. Herein, based on space and bond synergistic conjugation, a multiple‐aniline organic small molecule (TPD), is synthesized for high‐efficiency second near‐infrared (NIR‐II, 900–1700 nm) photoacoustic imaging guided PTT. With the heterogeneity of six nitrogen atoms in TPD, the lone electrons on the nitrogen atom and the π bond orbital on the benzene ring form multielectron conjugations with highly delocalized state, which endowed TPD with strong NIR‐II absorption (maximum peak at 925 nm). Besides, according to the single molecular reorganization, the alkyl side chains on TPD make more free space for intramolecular motion to enhance the photothermal conversion ability. Forming TPD nanoparticles (NPs) in J‐aggregation, they show a further bathochromic‐shifted absorbance (maximum peak at 976 nm) as well as a high photothermal conversion efficiency (66.7%) under NIR‐II laser irradiation. In vitro and in vivo experiments demonstrate that TPD NPs can effectively inhibit the growth of tumors without palpable side effects. The study provides a novel NIR‐II multiple‐aniline structure based on multielectron hyperconjugation, and opens a new design thought for photothermal agents.

Background Angiogenesis and tissue repair in chronic non-healing diabetic wounds remain critical clinical problems. Engineered MSC-derived exosomes have significant potential for the promotion of wound healing. Here, we discuss the effects and mechanisms of eNOS-rich umbilical cord MSC exosomes (UCMSC-exo/eNOS) modified by genetic engineering and optogenetic techniques on diabetic chronic wound repair. Methods Umbilical cord mesenchymal stem cells were engineered to express two recombinant proteins. Large amounts of eNOS were loaded into UCMSC-exo using the EXPLOR system under blue light irradiation. The effects of UCMSC-exo/eNOS on the biological functions of fibroblasts and vascular endothelial cells in vitro were evaluated. Full-thickness skin wounds were constructed on the backs of diabetic mice to assess the role of UCMSC-exo/eNOS in vascular neogenesis and the immune microenvironment, and to explore the related molecular mechanisms. Results eNOS was substantially enriched in UCMSCs-exo by endogenous cellular activities under blue light irradiation. UCMSC-exo/eNOS significantly improved the biological functions of cells after high-glucose treatment and reduced the expression of inflammatory factors and apoptosis induced by oxidative stress. In vivo, UCMSC-exo/eNOS significantly improved the rate of wound closure and enhanced vascular neogenesis and matrix remodeling in diabetic mice. UCMSC-exo/eNOS also improved the inflammatory profile at the wound site and modulated the associated immune microenvironment, thus significantly promoting tissue repair. Conclusion This study provides a novel therapeutic strategy based on engineered stem cell-derived exosomes for the promotion of angiogenesis and tissue repair in chronic diabetic wounds. Graphic Abstract

Innovative therapeutic strategy and effective drug delivery are significant challenges in current glioblastoma multiforme (GBM) therapy. The development of efficient combination therapy based on chemodynamic therapy (CDT) has attracted widespread attention in recent years. Herein, a lipopolysaccharide-free bacterial outer membrane vesicles (dOMV) camouflaged biomimetic nanoreactor was constructed for quadruple synergistic therapy of orthotopic GBM. Benefiting from the immune escaping property and blood-brain barrier (BBB) penetration capacity of dOMV, nanoreactors can target cancer cells and accumulate in the tumor site. Firstly, for quadruple synergistic therapy, Glucose oxidase (GOx) can rapidly consume intratumoral glucose to generate H2O2 and gluconic acid for starvation therapy. Secondly, the abundant H2O2 produced by the enzyme-catalyzed reaction can continuously supply Cu9S8-mediated Fenton-like reaction to enhance CDT. Meanwhile, tumor hypoxic microenvironment exacerbated by GOx-induced oxygen depletion activated prodrug AQ4N for chemotherapy. Finally, the second near -infrared (NIR-II) absorbed Cu9S8 increased the temperature in local tumor site upon NIR-II laser irradiation, which can achieve photothermal-enhanced CDT, elevate GOx activity, and accelerate drug release. In vitro and in vivo results demonstrated that the camouflaging multifunctional nanoparticles with bacterial outer mem-brane (AG@Cu9S8@dOMV) was a promising multifunctional therapeutic nanomedicine platform for highly efficient treatment of GBM, which may be extended to as a treatment option for clinical cancer theranostics.

Cancer with a complex pathological process is a major disease to human welfare. Due to the imbalance between oxygen (O2) supply and consumption, hypoxia is a natural characteristic of most solid tumors and an important obstacle for cancer therapy, which is closely related to tumor proliferation, metastasis, and invasion. Various strategies to exploit the feature of tumor hypoxia have been developed in the past decade, which can be used to alleviate tumor hypoxia, or utilize the hypoxia for targeted delivery and diagnostic imaging. The strategies to alleviate tumor hypoxia include delivering O2, in situ O2 generation, reprogramming the tumor vascular system, decreasing O2 consumption, and inhibiting HIF-1 related pathways. On the other side, hypoxia can also be utilized for hypoxia-responsive chemical construction and hypoxia-active prodrug-based strategies. Taking advantage of hypoxia in the tumor region, a number of methods have been applied to identify and keep track of changes in tumor hypoxia. Herein, we thoroughly review the recent progress of nanomedicine strategies in both conquering and utilizing hypoxia to combat cancer and put forward the prospect of emerging nanomaterials for future clinical transformation, which hopes to provide perspectives in nanomaterials design.

With excellent biocompatibility, stable chemical and optical properties, small organic molecules-based agents have always been a research hotspot in cancer photothermal therapy (PTT). In this work, a novel croconic acid-based molecule (CR) was designed and synthesized as an ideal photothermal agent (PTA), which showed abundant near-infrared (NIR) light absorption, high photothermal conversion ability, and excellent photothermal stability. By loading CR and quercetin (Qu) in CaO2, and coated with DSPE-PEG2000, a multifunctional theranostic nanoparticle (CCQ) was successfully prepared for calcium overloading mitochondrial metabolism inhibition synergetic mild PTT. Upon entering tumor microenvironment, CCQ can produce abundant H2O2 and a large amount of calcium ions, which lead to the imbalance of calcium concentration in the internal environment of tumor cells and induced mitochondrial apoptosis. With the existence of Qu, CCQ can effectively inhibit the expression of heat shock proteins (Hsp) during the PTT process, which weaken the heat resistance of tumors, ablate tumors at lower temperature (~45 °C), and reduce the damage to normal tissues. Guided by photoacoustic imaging (PAI), CCQ showed excellent multimodal therapeutic effect of tumors. This study provided a novel CR organic molecule-based theranostic nanoplatform that can be used to treat tumors via calcium overload therapy synergetic PTT at safe temperatures, which has promising potential for the future clinical cancer treatment.

Triple-negative breast cancer (TNBC) presents special biological behavior and clinicopathological characteristics and leads to a worse prognosis than other types of breast cancer. The development of an effective therapeutic method is significant to improve the survival rate of TNBC cancer patients. In this work, an engineered red blood cell membrane (RBCm)-coating salidroside/indocyanine green nanovesicle (ARISP) is successfully prepared for hypoxic targeting phototherapy of TNBC. Salidroside in ARISP effectively ameliorates hypoxia-induced tumorigenesis by downregulating the expression of hypoxia-inducible factor 1α (HIF-1α), which increases the killing effect of reactive oxygen species on tumor cells during photodynamic therapy (PDT) using the photosensitizer indocyanine green. Besides, ARISP has an anti-LDLR modified RBCm-coating that extends its circulation time in the blood and escapes from immune surveillance and enhances hypoxia-targeted cellular uptake via the overexpressed LDLR receptor in hypoxic tumor sites. Moreover, guided by near-infrared fluorescence imaging and photoacoustic imaging, ARISP can eliminate tumors via high-efficiency phototherapy and inhibit lung and liver metastasis in TNBC models. Cytotoxicity assay of ARISP indicates the excellent biocompatibility with normal cells and tissues. This study provides fulfilling insights into the anticancer mechanism of reducing HIF-1α for enhanced PDT and has a promising therapeutic potential for TNBC treatment.

The development of new diagnostic imaging and precise treatment methods for glioblastoma multiforme (GBM) is significant to improve patients' quality of life and prolong their survival time. Herein, we pro-posed a photoacoustic imaging (PAI)-guided GBM high-efficient photothermal therapy (PTT) based on a second near-infrared (NIR-II) absorptive polymer (PDTP-TBZ) conjugated with intense electron donor dithienopyrrole (DTP) and strong electron acceptor thiadiazolobenzotriazole (TBZ). By nanoprecipitation, PDTP-TBZ can form into nanoparticles (PT NPs), and c(RGDfK) cyclic peptide with integrin-specific target-ing was then modified on the surface of PT NPs to obtain the ability of active targeting GBM multifunc-tional nano-reagent (cRGD@PT NPs). Both in vitro and in vivo experiments demonstrated that cRGD@PT NPs as NIR-II GBM phototheranostic reagents can greatly improve the enrichment rate at tumor sites un -der PAI monitoring, and carry out precise NIR-II PTT with high effective tumor cell phototoxicity and high biological safety. Thus, cRGD@PT NPs have great potential for the future GBM phototheranostic applica-tion in clinic.Statement of significance In this work, we successfully constructed an intense electron donor dithienopyrrole (DTP) with a strong electron acceptor thiadiazolobenzotriazole (TBZ) into a novel NIR-II optical absorptive conjugated poly-mer (PDTP-TBZ). Then, the c(RGDfK) cyclic peptide was modified on the surface of PT NPs to obtain multifunctional nanodiagnostic reagents (cRGD@PT NPs) that can effectively target GBM neovasculariza-tion and tumor cells. Both in vitro and in vivo experiments demonstrate that cRGD@PT NPs possess high photothermal conversion efficiency and practical photoacoustic imaging capability under 1064 nm laser irradiation. The results of this work suggested that cRGD@PT NPs have great potential in efficient NIR-II PTT guided by accurate PAI, which provide a good perspective for the treatment and diagnosis of GBM.(c) 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Many organisms activate adaptive transcriptional programs to help them cope with decreased oxygen (O2) levels, or hypoxia, in their environment. These responses are triggered by various O2 sensing systems in bacteria, yeast and metazoans. In metazoans, the hypoxia inducible factors (HIFs) mediate the adaptive transcriptional response to hypoxia by upregulating genes involved in maintaining bioenergetic homeostasis. The HIFs in turn are regulated by HIF-specific prolyl hydroxlase activity, which is sensitive to cellular O2 levels and other factors such as tricarboxylic acid cycle metabolites and reactive oxygen species (ROS). Establishing a role for ROS in cellular oxygen sensing has been challenging since ROS are intrinsically unstable and difficult to measure. However, recent advances in fluorescence energy transfer resonance (FRET)-based methods for measuring ROS are alleviating some of the previous difficulties associated with dyes and luminescent chemicals. In addition, new genetic models have demonstrated that functional mitochondrial electron transport and associated ROS production during hypoxia are required for HIF stabilization in mammalian cells. Current efforts are directed at determining how ROS mediate prolyl hydroxylase activity and hypoxic HIF stabilization. Progress in understanding this process has been enhanced by the development of the FRET-based ROS probe, an vivo prolyl hydroxylase reporter and various genetic models harboring mutations in components of the mitochondrial electron transport chain.

Prolyl hydroxylation of hypoxible-inducible factor alpha (HIF-alpha) proteins is essential for their recognition by pVHL containing ubiquitin ligase complexes and subsequent degradation in oxygen (O(2))-replete cells. Therefore, HIF prolyl hydroxylase (PHD) enzymatic activity is critical for the regulation of cellular responses to O(2) deprivation (hypoxia). Using a fusion protein containing the human HIF-1alpha O(2)-dependent degradation domain (ODD), we monitored PHD activity both in vivo and in cell-free systems. This novel assay allows the simultaneous detection of both hydroxylated and nonhydroxylated PHD substrates in cells and during in vitro reactions. Importantly, the ODD fusion protein is regulated with kinetics identical to endogenous HIF-1alpha during cellular hypoxia and reoxygenation. Using in vitro assays, we demonstrated that the levels of iron (Fe), ascorbate, and various tricarboxylic acid (TCA) cycle intermediates affect PHD activity. The intracellular levels of these factors also modulate PHD function and HIF-1alpha accumulation in vivo. Furthermore, cells treated with mitochondrial inhibitors, such as rotenone and myxothiazol, provided direct evidence that PHDs remain active in hypoxic cells lacking functional mitochondria. Our results suggest that multiple mitochondrial products, including TCA cycle intermediates and reactive oxygen species, can coordinate PHD activity, HIF stabilization, and cellular responses to O(2) depletion.

While cellular responses to low oxygen (O2) or hypoxia have been studied extensively, the precise identity of mammalian cellular O2 sensors remains controversial. Using murine embryonic cells lacking cytochrome c, and therefore mitochondrial activity, we show that mitochondrial reactive oxygen species (mtROS) are essential for proper O2 sensing and subsequent HIF-1α and HIF-2α stabilization at 1.5% O2. In the absence of this signal, HIF-α subunits continue to be degraded. Furthermore, exogenous treatment with H2O2 or severe O2 deprivation is sufficient to stabilize HIF-α even in the absence of cytochrome c and functional mitochondria. These results provide genetic evidence indicating that mtROS act upstream of prolyl hydroxylases in regulating HIF-1α and HIF-2α in this O2-sensing pathway.

Solid tumors frequently contain hypoxic subregions due to insufficient blood supply. In these domains, cells can undergo p53-dependent apoptosis. Therefore, hypoxia has been implicated as a physiological stimulus for p53 accumulation and activation. In such an environment, p53 mutant cells exhibit a selective growth advantage. Hypoxic regulation of p53 has been proposed to be hypoxia inducible factor (HIF) dependent; however, controversy remains over whether and to what extent low oxygen (O2) tension by itself enhances p53 protein stability. Here, we examined the p53 response to hypoxia and hypoxia mimetics in several cell lines expressing different HIF-α proteins. Most cells exhibited elevated levels of p53 in response to hypoxia mimetics such as deferoxamine mesylate and CoCl2, regardless of their HIF-α protein expression profile. However, over a range of O2 levels, from 1.5% to less than 0.02%, we failed to observe p53 accumulation or p53 nuclear translocation in any cell lines tested. Only after treatment with a combination of hypoxia and acidosis/nutrient deprivation did some cells exhibit p53 induction. Our results suggest that, although hypoxia induces p53 accumulation in vivo, secondary effects such as acidosis caused by a hypoxic Pasteur effect (instead of low O2 by itself) are necessary for p53 accumulation. Therefore, the expression of HIF-1α and p53 proteins is not coupled during the cellular hypoxia response.

It has been proposed that bone marrow (BM) hematopoietic stem and progenitor cells are distributed along an oxygen (O-2) gradient, where stem cells reside in the most hypoxic areas and proliferating progenitors are found in O-2-rich areas. However, the effects of hypoxia on human hematopoietic stem cells (HSCs) have not been characterized. Our objective was to evaluate the functional and molecular responses of human BM progenitors and stem cells to hypoxic conditions. BM lineage-negative (Lin-) CD34(+)CD38(-) cells were cultured in serum-free medium under 1.5% O-2 (hypoxia) or 20% O-2 (normoxia) for 4 days. Using limiting dilution analysis, we demonstrate that the absolute number of SCID-repopulating cells (SRCs) increased by 5.8-fold in hypoxic cultures compared with normoxia, and by 4.2-fold compared with freshly isolated Lin(-)CD34(+)CD38(-) cells. The observed increase in BM-repopulating activity was associated with a preferential expansion of Lin(-)CD34(+)CD38(-) cells. We also demonstrate that, in response to hypoxia, hypoxia-inducible factor-1alpha. protein was stabilized, surface expression of angiogenic receptors was upregulated, and VEGF secretion increased in BM Lin(-)CD34(+) cultures. The use of low O2 levels to enhance the survival and/or self-renewal of human BM HSCs in vitro represents an important advance and could have valuable clinical implications.

Oxygen (O2), the final electron acceptor in the respiratory chain of oxidative phosphorylation, is absolutely required for most living organisms, including all invertebrates and vertebrates. The delivery of atmospheric O2 via diffusion to individual cells within a tissue is limited if the organ dimension is more than 3 mm3 (Dachs and Tozer, 2000). Thus, in insects such as Drosophila, a tracheal (respiratory) system develops to meet the O2 demand for internal tissues. Although the O2 delivery system in mammals is far more complicated, consisting of respiratory, cardiac, vascular, and hematopoietic cells, the basic function is similar to that of the insect trachea, to transport O2. Since these systems were developed to supply O2, it is logical to state that the availability and concentration of O2 regulates development of these O2 delivery systems. Indeed, a great deal of data sustains this claim both in the Drosophila tracheal system and mammalian angiogenesis.