Determining toxicity of europium oxide nanoparticles in immune cell components and hematopoiesis in dominant organs in mice: Role of lysosomal fluid interaction.

Extensive application of rare earth element oxide nanoparticles (REE NPs) has raised a concern over the possible toxic health effects after human exposure. Once entering the body, REE NPs are primarily processed by phagocytes in particular macrophages and undergo biotic phosphate complexation in lysosomal compartment. Such biotransformation affects the target organs and in vivo fate of REE NPs after escaping the lysosomes. However, the immunomodulatory effects of intraphagolysosomal dissolved REE NPs remains insufficient. Here, europium oxide (Eu2O3) NPs were pre-incubated with phagolysosomal simulant fluid (PSF) to mimic the biotransformation of europium oxide (p-Eu2O3) NPs under acid phagolysosome conditions. We investigated the alteration in immune cell components and the hematopoiesis disturbance on adult mice after intravenous administration of Eu2O3 NPs and p-Eu2O3 NPs. Our results indicated that the liver and spleen were the main target organs for Eu2O3 NPs and p-Eu2O3 NPs. Eu2O3 NPs had a much higher accumulative potential in organs than p-Eu2O3 NPs. Eu2O3 NPs induced more alterations in immune cells in the spleen, while p-Eu2O3 NPs caused stronger response in the liver. Regarding hematopoietic disruption, Eu2O3 NPs reduced platelets (PLTs) in peripheral blood, which might be related to the inhibited erythrocyte differentiation in the spleen. By contrast, p-Eu2O3 NPs did not cause significant disturbance in peripheral PLTs. Our study demonstrated that the preincubation with PSF led to a distinct response in the immune system compared to the pristine REE NPs, suggesting that the potentially toxic effects induced by the release of NPs after phagocytosis should not be neglected, especially when evaluating the safety of NPs application in vivo.

Schottky Barrier-Based Built-In Electric Field for Enhanced Tumor Photodynamic Therapy.

Photodynamic therapy's antitumor efficacy is hindered by the inefficient generation of reactive oxygen species (ROS) due to the photogenerated electron-hole pairs recombination of photosensitizers (PS). Therefore, there is an urgent need to develop efficient PSs with enhanced carrier dynamics. Herein, we designed Schottky junctions composed of cobalt tetroxide and palladium nanocubes (Co3O4@Pd) with a built-in electric field as effective PS. The built-in electric field enhanced photogenerated charge separation and migration, resulting in the generation of abundant electron-hole pairs and allowing effective production of ROS. Thanks to the built-in electric field, the photocurrent intensity and carrier lifetime of Co3O4@Pd were approximately 2 and 3 times those of Co3O4, respectively. Besides, the signal intensity of hydroxyl radical and singlet oxygen increased to 253.4% and 135.9%, respectively. Moreover, the localized surface plasmon resonance effect of Pd also enhanced the photothermal conversion efficiency of Co3O4@Pd to 40.50%. In vitro cellular level and in vivo xenograft model evaluations demonstrated that Co3O4@Pd could generate large amounts of ROS, trigger apoptosis, and inhibit tumor growth under near-infrared laser irradiation. Generally, this study reveals the contribution of the built-in electric field to improving photodynamic performance and provides new ideas for designing efficient inorganic PSs.

Newly identified lncRNA-45 promotes breast cancer metastasis through activating the mTOR signaling pathway.

BACKGROUND: Metastasis, a complex multi-stage process, is the primary cause of breast cancer-related death. Unfortunately, the molecular mechanisms underlying tumor metastasis have not been fully elucidated thus far. Long noncoding RNAs (lncRNAs) dictate the behaviours of tumor cells via multiple signaling pathways, resulting in tumor cell migration and invasion, as well as all stages of cancer progression. LncRNAs function as regulators in shaping cellular activities directly through influencing key genes involved in biological processes of the tumor, and representing promising novel targets in cancer diagnosis and therapy. We therefore sought to define the correlations between lncRNA expression and breast cancer metastasis, especially to investigate the functional pathway underlying lncRNA-mediated tumor invasion and metastasis process. RESULTS: In this study, we compared the lncRNA transcriptome profiles between primary breast cancer 4T1 cells and high metastatic 4T1-LG12 cells. We found that many differently expressed lncRNAs greatly correlated to the metastatic propensity of 4T1-LG12 cells, particularly lncRNA-45, a new lncRNA without functional annotations, which was found to be the most upregulated lncRNA transcribed by an internal region within the regulatory associated with protein of mechanistic target of rapamycin kinase (mTOR) complex 1 (Rptor) gene. LncRNA-45 was uncovered to be involved in the epithelial-to-mesenchymal transition process of breast cancer cells, as evidenced by the observation that lncRNA-45 knockdown significantly suppressed the invasive capability of parental 4T1-LG12 cells. Molecular mechanistic investigation showed that reduced activity of mTORC1-associated pathway led to a decrease of total ribosomal protein S6 kinase, polypeptide 1 (S6K1) content and enhancement of autophagy, consequently compromising the metastatic propensity in lncRNA-45 knockdown cells. CONCLUSIONS: Overall, our experiments uncovered that the newly identified lncRNA-45 played a regulatory role in breast cancer cell metastasis.

Deciphering the Effects of 2D Black Phosphorus on Disrupted Hematopoiesis and Pulmonary Immune Homeostasis Using a Developed Flow Cytometry Method.

As an emerging two-dimensional nanomaterial with promising prospects, mono- or few-layer black phosphorus (BP) is potentially toxic to humans. We investigated the effects of two types of BPs on adult male mice through intratracheal instillation. Using the flow cytometry method, the generation, migration, and recruitment of immune cells in different organs have been characterized on days 1, 7, 14, and 21 post-exposure. Compared with small BP (S-BP, lateral size at ∼188 nm), large BP (L-BP, lateral size at ∼326 nm) induced a stronger stress lymphopoiesis and B cell infiltration into the alveolar sac. More importantly, L-BP dramatically increased peripheral neutrophil (NE) counts up to 1.9-fold on day 21 post-exposure. Decreased expression of the CXCR4 on NEs, an important regulator of NE retention in the bone marrow, explained the increased NE release into the circulation induced by L-BP. Therefore, BP triggers systemic inflammation via the disruption of both the generation and migration of inflammatory immune cells.

Disturbed Gut-Liver axis indicating oral exposure to polystyrene microplastic potentially increases the risk of insulin resistance.

Human uptake abundance of microplastics via various pathways, and they accumulate in human liver, kidney, gut and even placenta (especially with a diameter of 1 µm or less). Recent scientific studies have found that exposure to microplastics causes intestinal inflammation and liver metabolic disorder, but it remains largely unknown that whether the damage and inflammation may cause further development of severe diseases. In this study, we discovered one of such potential diseases that may be induced by the exposure to small-sized microplastics (with a diameter of 1 µm) performing a multi-organ and multi-omics study comprising metabolomics and microbiome approaches. Unlike other animal experiments, the dosing strategy was applied in mice according to the daily exposure of the highly exposed population, which was more environmentally relevant and reflective of real-world human exposure. Our studies on the gut-liver axis metabolism have shown that the crosstalk between the gut and liver ultimately leaded to insulin resistance and even diabetes. We proactively verified this hypothesis by measuring the levels of fasting blood glucose and fasting insulin, which were found significantly elevated in the mice with microplastics exposure. These results indicate the urgent need of large-scale cohort evaluation on epidemiology and prognosis of insulin resistance after microplastics exposure in future.

Inflammation and accompanied disrupted hematopoiesis in adult mouse induced by rare earth element nanoparticles.

Rare earth element nanoparticles (REE NPs) or agents have been used extensively in various fields. Human exposure to REE NPs is an increasing concern. To date, REE NP-mediated comprehensive immune responses after incorporation into the body remain unclear. In our study, using gadolinium oxide NPs (Gd2O3) as a typical REE NP, we systematically investigated immune responses in vivo. The liver and spleen were the main sites where Gd2O3 retained and accumulated, while Gd2O3 content per unit tissue mass in the spleen was 4.4 times higher than that in the liver. Gd2O3 increased the number of monocyte-derived macrophages and myeloid-derived dendritic cells (M-DCs) in the liver. In the spleen, Gd2O3 caused infiltration of neutrophils, M-DCs, and B cells. The accumulation of Gd2O3 in the liver or spleen also contributed to an increased concentration of cytokines in peripheral blood. In both the bone marrow and spleen, Gd2O3 led to increased populations of hematopoietic stem cells (HSCs), multipotent progenitors, and common lymphoid progenitors. Compared to the decreased monocytes in peripheral blood on day 2, a significant decrease of circulating lymphocytes on day 7 was still observed, suggesting the exposure duration led to variable effects. This might be explained by the sustained accumulation of Gd2O3 in the liver and spleen. Together, our study systemically depicted the alterations in mature immune alterations together with hematopoiesis in both myeloid and lymphoid lineages induced by Gd2O3 exposure. Our findings will facilitate a comprehensive understanding of the interactions of immune system with REE NPs in vivo.

Palladium Nanoplate-Based IL-6 Receptor Antagonists Ameliorate Cancer-Related Anemia and Simultaneously Inhibit Cancer Progression.

In recent years, targeted therapies and immunotherapeutics, along with conventional chemo- and radiotherapy, have greatly improved cancer treatments. Unfortunately, in cancer patients, anemia, either as a complication of cancer progression or as the result of cancer treatment, undermines the expected therapeutic efficacy. Here, we developed a smart nanosystem based on the palladium nanoplates (PdPLs) to deliver tocilizumab (TCZ, a widely used IL-6R antibody) to the liver for specific blockade of IL-6/IL-6R signaling to correct anemia. With chemical modifications, this nanosystem delivered a large mass of TCZ and enhanced liver delivery, inducing a marked suppression of hepcidin expression as a result of diminished IL-6 signaling. Through this mechanism, significant suppression of tumor progression was realized (at least in part) because of the corrected anemia after treatment.

Tumor-specific fluorescence activation of rhodamine isothiocyanate derivatives.

Fluorescence is routinely used for in vivo tracking and imaging of molecules and nanostructures with assuming that the fluorescence intensity is proportional to the dye concentration. Herein, we report the unique tumor-specific fluorescence character of rhodamine B isothiocyanate derivatives (RBITCs), which emits fluorescence selectively in cancerous tissues, including small metastatic tumors, but is quenched in blood and healthy tissues. A preliminary mechanism study shows that binding of the thiourea group in the RBITCs on hemoglobin quenches their fluorescence, but the oxidation of the thiourea by the elevated reactive oxygen species in tumor activates the fluorescence. Thus, the fluorescent intensity of RBITCs is associated with the microenvironment of tissues and positively correlates with the cancer stages. These findings suggest that the RBITCs are not suitable for tracking of cargos in the presence of red blood cells but may be useful for cancer imaging and early diagnosis, and probing the tumor microenvironment.

Nanoscale perfluorocarbon expediates bone fracture healing through selectively activating osteoblastic differentiation and functions.

BACKGROUND AND RATIONALE: Fracture incidence increases with ageing and other contingencies. However, the strategy of accelerating fracture repair in clinical therapeutics remain a huge challenge due to its complexity and a long-lasting period. The emergence of nano-based drug delivery systems provides a highly efficient, targeted and controllable drug release at the diseased site. Thus far, fairly limited studies have been carried out using nanomedicines for the bone repair applications. Perfluorocarbon (PFC), FDA-approved clinical drug, is received increasing attention in nanomedicine due to its favorable chemical and biologic inertness, great biocompatibility, high oxygen affinity and serum-resistant capability. In the premise, the purpose of the current study is to prepare nano-sized PFC materials and to evaluate their advisable effects on promoting bone fracture repair. RESULTS: Our data unveiled that nano-PFC significantly enhanced the fracture repair in the rabbit model with radial fractures, as evidenced by increased soft callus formation, collagen synthesis and accumulation of beneficial cytokines (e.g., vascular endothelial growth factor (VEGF), matrix metalloprotein 9 (MMP-9) and osteocalcin). Mechanistic studies unraveled that nano-PFC functioned to target osteoblasts by stimulating their differentiation and activities in bone formation, leading to accelerated bone remodeling in the fractured zones. Otherwise, osteoclasts were not affected upon nano-PFC treatment, ruling out the potential target of nano-PFC on osteoclasts and their progenitors. CONCLUSIONS: These results suggest that nano-PFC provides a potential perspective for selectively targeting osteoblast cell and facilitating callus generation. This study opens up a new avenue for nano-PFC as a promising agent in therapeutics to shorten healing time in treating bone fracture.

Metal-Organic-Framework-Derived Carbon Nanostructures for Site-Specific Dual-Modality Photothermal/Photodynamic Thrombus Therapy.

Although near-infrared (NIR)-light-mediated photothermal thrombolysis has been investigated to overcome the bleeding risk of clinical clot-busting agents, the secondary embolism of post-phototherapy fragments (>10 µm) for small vessels should not be ignored in this process. In this study, dual-modality photothermal/photodynamic thrombolysis is explored using targeting nanoagents with an emphasis on improving biosafety as well as ameliorating the thrombolytic effect. The nanoagents can actively target glycoprotein IIb/IIIa receptors on thrombus to initiate site-specific thrombolysis by hyperthermia and reactive oxygen species under NIR laser irradiation. In comparison to single photothermal thrombolysis, an 87.9% higher re-establishment rate of dual-modality photothermal/photodynamic thrombolysis by one-time treatment is achieved in a lower limb thrombosis model. The dual-modality thrombolysis can also avoid re-embolization after breaking fibrin into tiny fragments. All the results show that this strategy is a safe and validated protocol for thrombolysis, which fits the clinical translational trend of nanomedicine.

Improved Healing of Diabetic Foot Ulcer upon Oxygenation Therapeutics through Oxygen-Loading Nanoperfluorocarbon Triggered by Radial Extracorporeal Shock Wave.

Diabetic foot ulcers (DFUs), the most serious complication of diabetes mellitus, can induce high morbidity, the need to amputate lower extremities, and even death. Although many adjunctive strategies have been applied for the treatment of DFUs, the low treatment efficiency, potential side effects, and high cost are still huge challenges. Recently, nanomaterial-based drug delivery systems (NDDSs) have achieved targeted drug delivery and controlled drug release, offering great promises in various therapeutics for diverse disorders. Additionally, the radial extracorporeal shock wave (rESW) has been shown to function as a robust trigger source for the NDDS to release its contents, as the rESW harbors a potent capability in generating pressure waves and in creating the cavitation effect. Here, we explored the performance of oxygen-loaded nanoperfluorocarbon (Nano-PFC) combined with the rESW as a treatment for DFUs. Prior to in vivo assessment, we first demonstrated the high oxygen affinity in vitro and great biocompatibility of Nano-PFC. Moreover, the rESW-responsive oxygen release behavior from oxygen-saturated Nano-PFC was also successfully verified in vitro and in vivo. Importantly, the wound healing of DFUs was significantly accelerated due to improved blood microcirculation, which was a result of rESW therapy (rESWT), and the targeted release of oxygen into the wound from oxygen-loaded Nano-PFC, which was triggered by the rESW. Collectively, the oxygen-saturated Nano-PFC and rESW provide a completely new approach to treat DFUs, and this study highlights the advantages of combining nanotechnology with rESW in therapeutics.

Black Phosphorus-Based Multimodal Nanoagent: Showing Targeted Combinatory Therapeutics against Cancer Metastasis.

In breast cancer chemophotothermal therapy, it is a great challenge for the development of multifunctional nanoagents for precision targeting and the effective treatment of tumors, especially for metastasis. Herein, we successfully design and synthesize a multifunctional black phosphorus (BP)-based nanoagent, BP/DTX@PLGA, to address this challenge. In this composite nanoagent, BP quantum dots (BPQDs) are loaded into poly(lactic-co-glycolic acid) (PLGA) with additional conjugation of a chemotherapeutic agent, docetaxel (DTX). The in vivo distribution results demonstrate that BP/DTX@PLGA shows striking tropism for targeting both primary tumors and lung metastatic tumors. Moreover, BP/DTX@PLGA exhibits outstanding controllable chemophotothermal combinatory therapeutics, which dramatically improves the efficacy of photothermal tumor ablation when combined with near-light irradiation. Mechanistically, accelerated DTX release from the nanocomplex upon heating and thermal treatment per se synergistically incurs apoptosis-dependent cell death, resulting in the elimination of lung metastasis. Meanwhile, in vitro and in vivo results further confirm that BP/DTX@PLGA possesses good biocompatibility. This study provides a promising BP-based multimodal nanoagent to constrain cancer metastasis.

A Nanozyme with Photo-Enhanced Dual Enzyme-Like Activities for Deep Pancreatic Cancer Therapy.

Nanozymes have attracted extensive interest owing to their high stability, low cost and easy preparation, especially in the field of cancer therapy. However, the relatively low catalytic activity of nanozymes in the tumor microenvironment (TME) has limited their applications. Herein, we report a novel nanozyme (PtFe@Fe3 O4 ) with dual enzyme-like activities for highly efficient tumor catalytic therapy. PtFe@Fe3 O4 shows the intrinsic photothermal effect as well as photo-enhanced peroxidase-like and catalase-like activities in the acidic TME, thereby effectively killing tumor cells and overcoming the tumor hypoxia. Importantly, a possible photo-enhanced synergistic catalytic mechanism of PtFe@Fe3 O4 was first disclosed. We believe that this work will advance the development of nanozymes in tumor catalytic therapy.

Activation of Prodrugs by NIR-Triggered Release of Exogenous Enzymes for Locoregional Chemo-photothermal Therapy.

Enzymes have been used to direct the conversion of prodrugs in cancer therapy. However, non-specific distribution of endogenous enzymes seriously hinders their bioapplications. Herein, we developed a near-infrared-triggered locoregional chemo-photothermal therapy based on the exogenous enzyme delivery and remolded tumor mivroenvironment. The catalytic efficiency of enzymes was enhanced by the hyperthermia, and the therapeutic efficacy of photothermal therapy (PTT) was improved owing to the inhibition of heat shock protein 90 by chemotherapeutics. The locoregional chemo-phototherapy achieved a one-time successful cure in 4T1 tumor-bearing mice model. Thus, a mutually reinforcing feedback loop between PTT and chemotherapy can be initiated by the irradiation, which holds a promising future in cancer therapy.

Interventional Photothermal Therapy Enhanced Brachytherapy: A New Strategy to Fight Deep Pancreatic Cancer.

Photothermal-radiotherapy (PT-RT) is an effective strategy for relieving hypoxia-related radiotherapy resistance and inducing tumor-specific cell apoptosis/necrosis. Nevertheless, limited tissue penetration of near-infrared (NIR) laser and the serious side effects of high-dose radiation severely hinder its applications for deep tumors. An interventional photothermal-brachytherapy (IPT-BT) technology is proposed here for the internal site-specific treatment of deep tumors. This technology utilizes a kind of biodegradable honeycomb-like gold nanoparticles (HGNs) acting as both internal photothermal agents and radiosensitizers. A high tumor inhibition rate of 96.6% is achieved in SW1990 orthotopic pancreatic tumor-bearing mice by HGNs-mediated IPT-BT synergistic therapy. Interestingly, this approach effectively causes double-stranded DNA damage and improves the oxygen supply and the penetration of nanoparticles inside the tumor. Therefore, it is believed that this strategy may open up a new avenue for PT-RT synergistic therapy of deep malignant tumors and has a significant impact on the future clinical translation.

Desferrioxamine-caffeine shows improved efficacy in chelating iron and depleting cancer stem cells.

Iron chelation has already been proposed to be a feasible strategy for cancer therapeutics in that reinforced iron demand is demonstrated in cancer cells, and quite a few iron chelators have been developed for this purpose. Desferrioxamine (DFO), an iron chelator approved by the U.S. Food and Drug Administration (FDA), has been extensively examined to remove extra iron. However, DFO has been found to harbor limited efficacies in combating cancer cells due to poor cellular permeability. In the current study, we synthesized the DFO derivative, named as desferrioxamine-caffeine dimer (DFCAF) by linking DFO to caffeine with high purity and excellent stability. Our data showed that DFCAF displayed greater cellular permeability to chelate intracellular iron in 4T1 breast cancer cells than DFO, posing more inhibition on cell growth and cellular motility/invasion. Importantly, DFCAF was uncovered to remarkably deplete cancer stem cells (CSCs), as characterized by the remarkable decrease of the CD44+/high/CD24-/low and ALDH+/high subpopulation. In parallel, DFCAF was also found to greatly reverse epithelial-mesenchymal transition (EMT), suggesting the potential application to restrain tumor progression and metastasis. Collectively, these data unveiled the improved efficacy to target cancer cells and to deplete CSCs, thus opening a new path for better cancer therapeutics through iron chelation.

Radial extracorporeal shock wave promotes the enhanced permeability and retention effect to reinforce cancer nanothermotherapeutics.

Since most cancer nanomedicine relies on the enhanced permeability and retention (EPR) effect to eradicate tumors, strategies that are able to promote nanoparticle (NP) delivery and extravasation are presupposed to elevate the EPR effect for more effective cancer therapeutics. However, nanothermotherapeutics still suffers from limited drug delivery into tumor sites, for even though numerous efforts have been made to enhance the selective tumor targeting of NPs. In this study, we uncovered that radial extracorporeal shock wave therapy (rESWT), an important approach in physical therapy that has been overlooked in cancer treatment in the past, can largely improve the EPR-dependent tumor uptake of NPs. We here defined the optimal low dosage and desirable combinatory manner for rESWT in driving NP accumulation towards tumors. Two underlying biophysical mechanisms responsible for the rESWT-enhanced EPR effect were proposed. On one hand, rESWT-conducted compressive and tensile forces could relieve high intra-tumoral pressure; on the other hand, rESWT-induced cavitation bubbles could directly distend and disrupt tumor blood vessels. All these together synergistically promoted vessel vasodilation, tumor perfusion and NP extravasation. Further experiments revealed that the combinatory therapeutics between rESWT and nanothermotherapeutics greatly improved the tumor-killing efficacy. Thus, our findings open a new path to improve EPR-mediated drug delivery with the assistance of rESWT.

Biodegradable Poly(amino acid)-Gold-Magnetic Complex with Efficient Endocytosis for Multimodal Imaging-Guided Chemo-photothermal Therapy.

Gold complexes can serve as efficient photothermal converters for cancer therapy, but their non-biodegradability hinders clinical bioapplications. Although enormous effort has been devoted, the conventionally adopted synthetic methods of biodegradation are characterized by high cost and complicated procedures, which delay the process of further clinical translation of gold complexes. Here, we report a multifunctional poly(amino acid)-gold-magnetic complex with self-degradation properties for synergistic chemo-photothermal therapy via simple and green chemistry methods. Nanoparticles of ∼3 nm in the biodegradation product were observed in simulated body fluid in 4 days. The biodegradability mainly benefits from the weakened internal electrostatic interaction of the poly(amino acid) by the ions in simulated body fluid. It is demonstrated that the poly(amino acid)-gold-magnetic complex has great cellular endocytosis by taking advantage of the guanidine group in arginine and possesses multimodal imaging and efficient tumor ablation (94%). This study reports a possibility for gold-magnetic complexes composed of poly(amino acid) to serve as a biodegradable nanotherapeutic for clinical applications.

Reduction of graphene oxide alters its cyto-compatibility towards primary and immortalized macrophages.

Graphene oxide (GO) and its derivatives (e.g., reduced graphene oxide, RGO) have shown great promise in biomedicine. Although many studies have been conducted to understand the relative cyto-compatibility between GO and RGO materials, the results are inconclusive and controversial. In this study, we compared the biocompatibility aspects (e.g. cytotoxicity, pro-inflammatory effects and impairment of cellular morphology) between parental and reduced GOs towards macrophages using primary bone marrow-derived macrophages (BMDMs) and J774A.1 cell line. Two RGOs (RGO1 and RGO2) with differential reduction levels relative to the parental GO were prepared. Intriguingly, besides loss of oxygen-containing functional groups, significant morphological alteration of GO occurred, from the sheet-like structure to a polygonal curled shape for RGO, without significant aggregation in biological medium. Cytotoxicity assessment unveiled that the RGOs were more toxic than pristine GO to both types of cells. It was surprising to find for the first time (to our knowledge) that GO and RGOs elicited different effects on the morphological changes of BMDMs, as reflected by elongated protrusions from GO treatment and shortened protrusions from the RGOs. Furthermore, RGOs induced greater pro-inflammatory responses than GO, especially in BMDMs. Compromised cyto-compatibility of RGOs was attributable (at least partially) to their greater oxidative stress in macrophages. Mechanistically, these differences in bio-reactivities between GO and RGO should be boiled down to (at least in part) the synergistic effects from the variation of oxygen-containing functional groups and the distinct morphology in between. This study unearthed the crucial contribution of reduction-mediated detrimental cellular effects between GO and RGO towards macrophages.

Bio-transformation of Graphene Oxide in Lung Fluids Significantly Enhances Its Photothermal Efficacy.

Rationale: Graphene oxide (GO) has shown great promises in biomedical applications, such as drug delivery and thermotherapeutics, owing to its extraordinary physicochemical properties. Nonetheless, current biomedical applications of GO materials are premised on the basis of predesigned functions, and little consideration has been given to the influence of bio-transformation in the physiological environment on the physicochemical properties and predesigned functionalities of these materials. Hence, it is crucial to uncover the possible influence on GO's physicochemical properties and predesigned functionalities for better applications. Methods: Bio-transformed GOs were characterized by X-ray diffraction (XRD) spectra, Raman spectra, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared transmission (FT-IR) spectra. The morphologies of various GO materials were assessed via transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM) images. The photothermal (PTT) performance of different GO materials in vitro and in vivo were measured using 808 nm laser at a power density of 2 W/cm2. The PTT efficacy was determined using transplanted 4T1 cells-derived breast tumors in mice. Results: Bio-transformation of GO in the lung (a main target organ for GO to localize in vivo) can induce dramatic changes to its physicochemical properties and morphology, and consequently, its performances in biomedical applications. Specifically, GO underwent significant reduction in two simulated lung fluids, Gamble's solution and artificial lysosomal fluid (ALF), as evidenced by the increase of C/O ratio (the ratio of C content to O content) relative to pristine GO. Bio-transformation also altered GO's morphology, characterized by sheet folding and wrinkle formation. Intriguingly, bio-transformation elevated the PTT performance of GO in vitro, and this elevation further facilitated PTT-based tumor-killing efficacy in tumor cells in vitro and in a mouse model with transplanted tumors. Bio-transformation also compromised the interaction between drug with GO, leading to reduced drug adsorption, as tested using doxorubicin (DOX). Conclusions: Transformation in Gamble's solution and ALF resulted in varied degrees of improved performances of GO, due to the differential effects on GO's physicochemical properties. Our findings unveiled an overlooked impact of GO bio-transformation, and unearthed a favorable trait of GO materials in thermotherapeutics and drug delivery in the lung microenvironment.