Nanoparticle Mediated Tumor Vascular Disruption: A Novel Strategy in Radiation Therapy

Breaking the barrier: Nanoparticle-enhanced radiotherapy as the new vanguard in brain tumor treatment

The pursuit of effective treatments for brain tumors has increasingly focused on the promising area of nanoparticle-enhanced radiotherapy (NERT). This review elucidates the context and significance of NERT, with a particular emphasis on its application in brain tumor therapy-a field where traditional treatments often encounter obstacles due to the blood-brain barrier (BBB) and tumor cells' inherent resistance. The aims of this review include synthesizing recent advancements, analyzing action mechanisms, and assessing the clinical potential and challenges associated with nanoparticle (NP) use in radiotherapy enhancement. Preliminary preclinical studies have established a foundation for NERT, demonstrating that nanoparticles (NPs) can serve as radiosensitizers, thereby intensifying radiotherapy's efficacy. Investigations into various NP types, such as metallic, magnetic, and polymeric, have each unveiled distinct interactions with ionizing radiation, leading to an augmented destruction of tumor cells. These interactions, encompassing physical dose enhancement and biological and chemical radio sensitization, are crucial to the NERT strategy. Although clinical studies are in their early phases, initial trials have shown promising results in terms of tumor response rates and survival, albeit with mindful consideration of toxicity profiles. This review examines pivotal studies affirming NERT's efficacy and safety. NPs have the potential to revolutionize radiotherapy by overcoming challenges in targeted delivery, reducing off-target effects, and harmonizing with other modalities. Future directions include refining NP formulations, personalizing therapies, and navigating regulatory pathways. NERT holds promise to transform brain tumor treatment and provide hope for patients.

Multifunctional nanostructures: Intelligent design to overcome biological barriers

Over the past three decades, nanoscience has offered a unique solution for reducing the systemic toxicity of chemotherapy drugs and for increasing drug therapeutic efficiency. However, the poor accumulation and pharmacokinetics of nanoparticles are some of the key reasons for their slow translation into the clinic. The is intimately linked to the non-biological nature of nanoparticles and the aberrant features of solid cancer, which together significantly compromise nanoparticle delivery. New findings on the unique properties of tumors and their interactions with nanoparticles and the human body suggest that, contrary to what was long-believed, tumor features may be more mirage than miracle, as the enhanced permeability and retention based efficacy is estimated to be as low as 1%. In this review, we highlight the current barriers and available solutions to pave the way for approved nanoformulations. Furthermore, we aim to discuss the main solutions to solve inefficient drug delivery with the use of nanobioengineering of nanocarriers and the tumor environment. Finally, we will discuss the suggested strategies to overcome two or more biological barriers with one nanocarrier. The variety of design formats, applications and implications of each of these methods will also be evaluated.

Recent Research Progress of RGD Peptide–Modified Nanodrug Delivery Systems in Tumor Therapy

There have been great advancements in targeted nanodrug delivery systems for tumor therapy. Liposomes, polymeric nanoparticles, and inorganic nanoparticles are commonly employed as nanocarriers for drug delivery, and it has been found that arginine glycine aspartic acid (RGD) peptides and their derivatives can be used as ligands of integrin receptors to enhance the direct targeting ability. In this paper, we review the recent applications of RGD-modified liposomes, polymeric nanoparticles, and inorganic nanocarriers in cancer diagnosis and treatment, discuss the current challenges and prospects, and examine the progress made by the latest research on RGD peptide–modified nano delivery systems in cancer therapy. In recent years, RGD peptide–modified nanodrug delivery systems have been proven to have great potential in tumor therapy. Finally, we provide an overview of the current limitations and future directions of RGD peptide–modified nano-drug delivery systems for cancer therapy. This review aims to elucidate the contribution of RGD peptide–modified nanodrug delivery systems in the field of tumor therapy.

Combined Photodynamic and Photothermal Therapy and Immunotherapy for Cancer Treatment: A Review

Photoactivation therapy based on photodynamic therapy (PDT) and photothermal therapy (PTT) has been identified as a tumour ablation modality for numerous cancer indications, with photosensitisers and photothermal conversion agents playing important roles in the phototherapy process, especially in recent decades. In addition, the iteration of nanotechnology has strongly promoted the development of phototherapy in tumour treatment. PDT can increase the sensitivity of tumour cells to PTT by interfering with the tumour microenvironment, whereas the heat generated by PTT can increase blood flow, improve oxygen supply and enhance the PDT therapeutic effect. In addition, tumour cell debris generated by phototherapy can serve as tumour-associated antigens, evoking antitumor immune responses. In this review, the research progress of phototherapy, and its research effects in combination with immunotherapy on the treatment of tumours are mainly outlined, and issues that may need continued attention in the future are raised.

Radiotherapy-induced enrichment of EGF-modified doxorubicin nanoparticles enhances the therapeutic outcome of lung cancer

Chemotherapy is the primary treatment for advanced non-small-cell lung cancer (NSCLC). However, related dose-dependent toxicity limits its clinical use. Therefore, it is necessary to explore new strategies for improving the clinical outcomes while reducing the side effects of chemotherapy in the treatment of NSCLC. In this study, we designed and synthesized epidermal growth factor (EGF)-modified doxorubicin nanoparticles (EGF@DOX-NPs) that selectively targets the epidermal growth factor receptor (EGFR) overexpressed in lung tumor cells. When administered in combination with low-dose X-ray radiotherapy (RT), the NPs preferentially accumulated at the tumor site due to radiation-induced outburst of the local intra-tumoral blood vessels. Compared with DOX alone, EGF@DOX-NPs significantly decreased the viability and migration and enhanced the apoptosis rates of tumor cells in vitro. Also, the EGF@DOX-NPs significantly inhibited tumor growth in vivo, increasing the survival of the tumor-bearing mice without apparent systemic toxic effects through RT-induced aggregation. The tumor cell proliferation was greatly inhibited in the RT + EGF@DOX-NPs group. Contrarily, the apoptosis of tumor cells was significantly higher in this group. These results confirm the promising clinical application of radiotherapy in combination with EGF@DOX-NPs for lung cancer treatment.

Precision Nanotoxicology in Drug Development: Current Trends and Challenges in Safety and Toxicity Implications of Customized Multifunctional Nanocarriers for Drug-Delivery Applications

The dire need for the assessment of human and environmental endangerments of nanoparticulate material has motivated the formulation of novel scientific tools and techniques to detect, quantify, and characterize these nanomaterials. Several of these paradigms possess enormous possibilities for applications in many of the realms of nanotoxicology. Furthermore, in a large number of cases, the limited capabilities to assess the environmental and human toxicological outcomes of customized and tailored multifunctional nanoparticles used for drug delivery have hindered their full exploitation in preclinical and clinical settings. With the ever-compounded availability of nanoparticulate materials in commercialized settings, an ever-arising popular debate has been egressing on whether the social, human, and environmental costs associated with the risks of nanomaterials outweigh their profits. Here we briefly review the various health, pharmaceutical, and regulatory aspects of nanotoxicology of engineered multifunctional nanoparticles in vitro and in vivo. Several aspects and issues encountered during the safety and toxicity assessments of these drug-delivery nanocarriers have also been summarized. Furthermore, recent trends implicated in the nanotoxicological evaluations of nanoparticulate matter in vitro and in vivo have also been discussed. Due to the absence of robust and rigid regulatory guidelines, researchers currently frequently encounter a larger number of challenges in the toxicology assessment of nanocarriers, which have also been briefly discussed here. Nanotoxicology has an appreciable and significant part in the clinical translational development as well as commercialization potential of nanocarriers; hence these aspects have also been touched upon. Finally, a brief overview has been provided regarding some of the nanocarrier-based medicines that are currently undergoing clinical trials, and some of those which have recently been commercialized and are available for patients. It is expected that this review will instigate an appreciable interest in the research community working in the arena of pharmaceutical drug development and nanoformulation-based drug delivery.

Inducible endothelial leakiness in nanotherapeutic applications

All intravenous delivered nanomedicine needs to escape from the blood vessel to exert their therapeutic efficacy at their designated site of action. Failure to do so increases the possibility of detrimental side effects and negates their therapeutic intent. Many powerful anticancer nanomedicine strategies rely solely on the tumor derived enhanced permeability and retention (EPR) effect for the only mode of escaping from the tumor vasculature. However, not all tumors have the EPR effect nor can the EPR effect be induced or controlled for its location and timeliness. In recent years, there have been exciting developments along the lines of inducing endothelial leakiness at the tumor to decrease the dependence of EPR. Physical disruption of the endothelial-endothelial cell junctions with coordinated biological intrinsic pathways have been proposed that includes various modalities like ultrasound, radiotherapy, heat and even nanoparticles, appear to show good progress towards the goal of inducing endothelial leakiness. This review explains the intricate and complex biological background behind the endothelial cells with linkages on how updated reported nanomedicine strategies managed to induce endothelial leakiness. This review will also end off with fresh insights on where the future of inducible endothelial leakiness holds.

Optimal Physicochemical Properties of Antibody-Nanoparticle Conjugates for Improved Tumor Targeting

Tumor-targeted antibody (mAb)/fragment-conjugated nanoparticles (NPs) represent an innovative strategy for improving the local delivery of small molecules. However, the physicochemical properties of full mAb-NPs and fragment-NPs-that is, NP material, size, charge, as well as the targeting antibody moiety, and the linker conjugation strategies-remain to be optimized to achieve an efficient tumor targeting. A meta-analysis of 161 peer-reviewed studies is presented, which describes the use of tumor-targeted mAb-NPs and fragment-NPs from 2009 to 2021. The use of these targeted NPs is confirmed to result in significantly greater tumor uptake of NPs than that of naked NPs (7.9 ± 1.9% ID g^-1 versus 3.2 ± 0.6% ID g^-1 , respectively). The study further demonstrates that for lipidic NPs, fragment-NPs provide a significantly higher tumor uptake than full mAb-NPs. In parallel, for both polymeric and organic/inorganic NPs, full mAb-NPs yield a significant higher tumor uptake than fragment-NPs. In addition, for both lipidic and polymeric NPs, the tumor uptake is improved with the smallest sizes of the conjugates. Finally, the pharmacokinetics of the conjugates are demonstrated to be driven by the NPs and not by the antibody moieties, independently of using full mAb-NPs or fragment-NPs, confirming the importance of optimizing the NP design to improve the tumor uptake.

Clinical Feasibility Study of Gold Nanoparticles as Theragnostic Agents for Precision Radiotherapy

Background: Gold nanoparticles (AuNP) may be useful in precision radiotherapy and disease monitoring as theragnostic agents. In diagnostics, they can be detected by computerized tomography (CT) because of their higher atomic number. AuNP may also improve the treatment results in radiotherapy due to a higher cross-section, locally improving the physically absorbed dose. Methods: Key parameters values involved in the use of AuNP were imposed to be optimal in the clinical scenario. Mass concentration of AuNP as an efficient contrast agent in clinical CT was found and implemented in a Monte Carlo simulation method for dose calculation under different proposed therapeutic beams. The radiosensitization effect was determined in irradiated cells with AuNP. Results: an AuNP concentration was found for a proper contrast level and enhanced therapeutic effect under a beam typically used for image-guided therapy and monitoring. This lower energetic proposed beam showed potential use for treatment monitoring in addition to absorbed dose enhancement and higher radiosensitization at the cellular level. Conclusion: the results obtained show the use of AuNP concentration around 20 mg Au·mL⁻¹ as an efficient tool for diagnosis, treatment planning, and monitoring treatment. Simultaneously, the delivered prescription dose provides a higher radiobiological effect on the cancer cell for achieving precision radiotherapy.

Image-Based Quantification of Gold Nanoparticle Uptake and Localization in 3D Tumor Models to Inform Radiosensitization Schedule

Gold nanoparticles (GNPs) have shown particular promise as radiosensitizing agents and as complementary drug delivery agents to improve therapeutic index in cancer treatment. Optimal implementation, however, depends critically on the localization of GNPs at the time of irradiation, which, in turn, depends on their size, shape, and chemical functionalization, as well as organism-level pharmacokinetics and interactions with the tumor microenvironment. Here, we use in vitro 3D cultures of A549 lung carcinoma cells, which recapitulate interaction with extracellular matrix (ECM) components, combined with quantitative fluorescence imaging to study how time-dependent localization of ultrasmall GNPs in tumors and ECM impacts the degree of damage enhancement to tumor cells. Confocal imaging of fluorescence-labeled GNPs in 3D culture reveals that nanoparticles are initially embedded in ECM and only gradually accumulate in cancer cells over multiple days. Furthermore, the timing of GNP redistribution from ECM to cellular compartments directly impacts efficacy, with major damage enhancement when irradiation is performed after GNPs have accumulated significantly in 3D tumor nodules. These results underscore the importance of the timing and scheduling in treatment planning to ensure optimal radiosensitization, as well as the necessity of studying these effects in model systems that recapitulate elements of tumor microenvironment interaction.

Recent advances of nanotechnology-based tumor vessel-targeting strategies

Tumor vessels can provide oxygen and nutrition for solid tumor tissue, create abnormal tumor microenvironment (TME), and play a vital role in the development, immune escape, metastasis and drug resistance of tumor. Tumor vessel-targeting therapy has become an important and promising direction in anti-tumor therapy, with the development of five anti-tumor therapeutic strategies, including vascular disruption, anti-angiogenesis, vascular blockade, vascular normalization and breaking immunosuppressive TME. However, the insufficient drug accumulation and severe side effects of vessel-targeting drugs limit their development in clinical application. Nanotechnology offers an excellent platform with flexible modified surface that can precisely deliver diverse cargoes, optimize efficacy, reduce side effects, and realize the combined therapy. Various nanomedicines (NMs) have been developed to target abnormal tumor vessels and specific TME to achieve more efficient vessel-targeting therapy. The article reviews tumor vascular abnormalities and the resulting abnormal microenvironment, the application of NMs in the tumor vessel-targeting strategies, and how NMs can improve these strategies and achieve multi-strategies combination to maximize anti-tumor effects.

Repurposing Erythrocytes as a "Photoactivatable Bomb": A General Strategy for Site-Specific Drug Release in Blood Vessels

Tumor vasculature has long been considered as an extremely valuable therapeutic target for cancer therapy, but how to realize controlled and site-specific drug release in tumor blood vessels remains a huge challenge. Despite the widespread use of nanomaterials in constructing drug delivery systems, they are suboptimal in principle for meeting this demand due to their easy blood cell adsorption/internalization and short lifetime in the systemic circulation. Here, natural red blood cells (RBCs) are repurposed as a remote-controllable drug vehicle, which retains RBC's morphology and vessel-specific biodistribution pattern, by installing photoactivatable molecular triggers on the RBC membrane via covalent conjugation with a finely tuned modification density. The molecular triggers can burst the RBC vehicle under short and mild laser irradiation, leading to a complete and site-specific release of its payloads. This cell-based vehicle is generalized by loading different therapeutic agents including macromolecular thrombin, a blood clotting-inducing enzyme, and a small-molecule hypoxia-activatable chemodrug, tirapazamine. In vivo results demonstrate that the repurposed "anticancer RBCs" exhibit long-term stability in systemic circulation but, when tumors receive laser irradiation, precisely releases their cargoes in tumor vessels for thrombosis-induced starvation therapy and local deoxygenation-enhanced chemotherapy. This study proposes a general strategy for blood vessel-specific drug delivery.

Ex vivo three-dimensional elemental imaging of mouse brain tissue block by laser-induced breakdown spectroscopy

Measurement and reconstruction of an elemental image of large brain tissue will be beneficial to the diagnosis of neurological brain diseases. Herein, laser-induced breakdown spectroscopy (LIBS) is introduced for three dimensional (3D) elemental analysis of paraffin-embedded mouse brain tissue blocks. It is used for the first time towards the mapping of mouse brain block samples. A micro-LIBS prototype is developed for brain elemental imaging and a layer-by-layer approach is used to reconstruct the 3D distribution of Ca, Mg, Na, Cu, and P in the brain tissue. Images are captured with 50 μm lateral resolution and 300 μm depth resolution. The images show that the reclamation area of the cortex surface is enriched with Ca and Mg. In contrast, the Cu distribution is circular and is found primarily in the entirety of the cerebral cortex for the paraffin-embedded brain samples. Elemental imaging results suggest that the highest P intensity is found in the cerebellum nearby the middle sagittal plane in the left-brain paraffin block. These preliminary results indicate that LIBS is a potentially powerful tool for elemental bioimaging of the whole brain and may further improve the understanding of complex brain mechanisms.

Preclinical models and technologies to advance nanovaccine development

The remarkable success of targeted immunotherapies is revolutionizing cancer treatment. However, tumor heterogeneity and low immunogenicity, in addition to several tumor-associated immunosuppression mechanisms are among the major factors that have precluded the success of cancer vaccines as targeted cancer immunotherapies. The exciting outcomes obtained in patients upon the injection of tumor-specific antigens and adjuvants intratumorally, reinvigorated interest in the use of nanotechnology to foster the delivery of vaccines to address cancer unmet needs. Thus, bridging nano-based vaccine platform development and predicted clinical outcomes the selection of the proper preclinical model will be fundamental. Preclinical models have revealed promising outcomes for cancer vaccines. However, only few cases were associated with clinical responses. This review addresses the major challenges related to the translation of cancer nano-based vaccines to the clinic, discussing the requirements for ex vivo and in vivo models of cancer to ensure the translation of preclinical success to patients.

Microdosimetric-Kinetic Model for Radio-enhancement of Gold Nanoparticles: Comparison with LEM

Numerous studies have strongly supported the application of gold nanoparticles (GNPs) as radio-enhanced agents. In our previous study, the local effect model (LEM I) was adopted to predict the cell survival for MDA-MB-231 cells exposed to 150 kVp X rays after 500 µg/ml GNPs treatment. However, microdosimetric quantities could not be obtained, which were correlated with biological effects on cells. Thus, we developed microdosimetric kinetic model (MKM) for GNP radio-enhancement (GNP-MKM), which uses the microdosimetric quantities such as dose-mean lineal energy with subcellular domain size. Using the Monte Carlo simulation tool Geant4, we estimated the dose-mean lineal energy with secondary radiations from GNPs and absorbed dose in the nucleus. The variations in MKM parameters for different domain sizes, and GNP concentrations, were calculated to compare the survival fractions predicted by both models. With a domain radius of 500 nm and a threshold dose of 20 Gy, the sensitizer enhancement ratio predicted by GNP-MKM and GNP-LEM was 1.41 and 1.29, respectively. The GNP-MKM predictions were much more strongly dependent on the domain size than were the GNP-LEM on the threshold dose. These findings provide another method to predict survival fraction for the GNP radio-enhancement.

Hierarchical responsive micelle facilitates intratumoral penetration by acid-activated positive charge surface and size contraction

Integrating these features of acid-activated positively charged surface and size contraction into single nanoparticle would be an effective strategy for enhancing cellular uptake, intratumoral penetration and accumulation. Here, hierarchical responsive micelle (HVDMs) was developed via RAFT reaction as multifunctional polymer-drug conjugate for maximizing penetration and therapeutic effect against MCF-7 tumor by combining positively charged surface with size contraction: surface zeta-potential reversal (-2 to +12 mV) by protonation of PHEME and size contraction (~81-~41 nm) by simultaneous hydrophobic/hydrophilic conversion (pH ≈ 6.7); the disintegration of hydrazone bond between hydrophobic PVB and DOX triggered drug release (pH ≈ 5.0). The in vitro structural stabilization, cellular uptake and anti-proliferative efficiency were significantly higher than other control groups (CVDMs and HSDMs) at pH 6.7. The markedly increased penetration depth, cellular internalization and anti-tumor efficiency were confirmed in 3D MCSs spheroids at pH 6.7, and the ex vivo DOX fluorescence images further verified obvious penetration and accumulation in internal region of solid tumor. The antitumor effect in vivo demonstrated that HVDMs accelerated tumor atrophy, induced intratumoral cells apoptosis and alleviated system toxicity.

Application of Emerging Plant-Derived Nanoparticles as a Novel Approach for Nano-Drug Delivery Systems

Nanotechnology has enabled the delivery of small molecular drugs packaged in nanosized vesicles to the target tissues. Plant-Derived Nanoparticles (PDNPs) are vesicles with natural origin and unique properties. These nanoparticles have several advantages over synthetic exosomes and liposomes. They provide bioavailability and biodistribution of therapeutic agents when delivered into different tissues. These nanoparticles can be modified according to the specificity of their functions in target tissues. When PDNPs are internalized, they can induce stem cells proliferation, reduce colitis injury, activate intrinsic and extrinsic apoptosis pathways, and inhibit tumor growth and progression. These properties make them potential drug delivery systems in targeting diseased tissues, such as inflammatory regions and different cancers.

Nanodrug Delivery Systems Modulate Tumor Vessels to Increase the Enhanced Permeability and Retention Effect

The use of nanomedicine for antitumor therapy has been extensively investigated for a long time. Enhanced permeability and retention (EPR) effect-mediated drug delivery is currently regarded as an effective way to bring drugs to tumors, especially macromolecular drugs and drug-loaded pharmaceutical nanocarriers. However, a disordered vessel network, and occluded or embolized tumor blood vessels seriously limit the EPR effect. To augment the EPR effect and improve curative effects, in this review, we focused on the perspective of tumor blood vessels, and analyzed the relationship among abnormal angiogenesis, abnormal vascular structure, irregular blood flow, extensive permeability of tumor vessels, and the EPR effect. In this commentary, nanoparticles including liposomes, micelles, and polymers extravasate through the tumor vasculature, which are based on modulating tumor vessels, to increase the EPR effect, thereby increasing their therapeutic effect.

Marginative Delivery-Mediated Extracellular Leakiness and T Cell Infiltration in Lung Metastasis by a Biomimetic Nanoraspberry

T lymphocytes infiltrate the most devastating metastatic tumors for immunotherapy, allowing the potential for tumor metastasis suppression. However, tumor heterogeneity often restricts the infiltration of immune cells and possesses immune privilege that leads to protection from the immune attack, especially for invading metastatic clusters. Here, an exosome-camouflaged nanoraspberry (RB@Exo) doubling as a metastases-targeting agent and T cell-infiltration inducer that delivers an anticancer drug and energy is reported. The RB@Exo integrated an exosome-derived margination effect, and density-mediated nanoparticle-induced extracellular leakiness (nanoEL) exhibited more than a 70% colocalization of the RB@Exo to metastatic tumors in the lung in vivo. The release of cancer cell-cell interactions at the metastasis via nanoEL also elicited the 10-fold infiltration of T lymphocytes. The synergy of the T cell infiltration and photolytic effects transported by the RB@Exo deep into the metastatic tumors effectively inhibited the tumor in 60 days when treated with a single alternating magnetic field (AMF).

Reactive Oxygen Species-Regulating Strategies Based on Nanomaterials for Disease Treatment

Reactive oxygen species (ROS) play an essential role in physiological and pathological processes. Studies on the regulation of ROS for disease treatments have caused wide concern, mainly involving the topics in ROS-regulating therapy such as antioxidant therapy triggered by ROS scavengers and ROS-induced toxic therapy mediated by ROS-elevation agents. Benefiting from the remarkable advances of nanotechnology, a large number of nanomaterials with the ROS-regulating ability are developed to seek new and effective ROS-related nanotherapeutic modalities or nanomedicines. Although considerable achievements have been made in ROS-based nanomedicines for disease treatments, some fundamental but key questions such as the rational design principle for ROS-related nanomaterials are held in low regard. Here, the design principle can serve as the initial framework for scientists and technicians to design and optimize the ROS-regulating nanomedicines, thereby minimizing the gap of nanomedicines for biomedical application during the design stage. Herein, an overview of the current progress of ROS-associated nanomedicines in disease treatments is summarized. And then, by particularly addressing these known strategies in ROS-associated therapy, several fundamental and key principles for the design of ROS-associated nanomedicines are presented. Finally, future perspectives are also discussed in depth for the development of ROS-associated nanomedicines.

Novel Iodine nanoparticles target vascular mimicry in intracerebral triple negative human MDA-MB-231 breast tumors

Triple negative breast cancer (TNBC), ~ 10-20% of diagnosed breast cancers, metastasizes to brain, lungs, liver. Iodine nanoparticle (INP) radioenhancers specifically localize to human TNBC MDA-MB-231 tumors growing in mouse brains after iv injection, significantly extending survival of mice after radiation therapy (RT). A prominent rim of INP contrast (MicroCT) previously seen in subcutaneous tumors but not intracerebral gliomas, provide calculated X-ray dose-enhancements up to > eightfold. Here, MDA-MB-231-cells, INPs, CD31 were examined by fluorescence confocal microscopy. Most INP staining co-localized with CD31 in the tumor center and periphery. Greatest INP/CD31 staining was in the tumor periphery, the region of increased MicroCT contrast. Tumor cells are seen to line irregularly-shaped spaces (ISS) with INP, CD31 staining very close to or on the tumor cell surface and PAS stain on their boundary and may represent a unique form of CD31-expressing vascular mimicry in intracerebral 231-tumors. INP/CD31 co-staining is also seen around ISS formed around tumor cells migrating on CD31+ blood-vessels. The significant radiation dose enhancement to the prolific collagen I containing, INP-binding ISS found throughout the tumor but concentrated in the tumor rim, may contribute significantly to the life extensions observed after INP-RT; VM could represent a new drug/NP, particularly INP, tumor-homing target.

Injectable biodegradation-visual self-healing citrate hydrogel with high tissue penetration for microenvironment-responsive degradation and local tumor therapy

Local tumor therapy through injectable biodegradable hydrogels with controlled drug release has attracted much attention recently, due to their easy operation, low side effect and efficiency. However, most of the reported therapeutic hydrogel system showed a lack of biodegradation tracking and tumor environment-responsive degradation/therapy. Herein, we developed a multifunctional injectable biodegradation-visual citric acid-based self-healing scaffolds with microenvironment-responsive degradation and drug release for safe and efficient skin tumor therapy (FPRC hydrogel). FPRC scaffolds possess multifunctional properties including thermosensitive, injectable, self-healing, photoluminescent and pH-responsive degradation/drug release. The FPRC scaffolds with strong red fluorescence which has good photostability, tissue penetration and biocompatibility can be tracked and monitored to evaluate the degradation of the scaffolds in vivo. Moreover, the FPRC scaffolds showed pH-responsive doxorubicin (DOX) release, efficiently killed the A375 cancer cell in vitro and suppressed the tumor growth in vivo. Compared to the free drug (DOX), the FPRC@DOX scaffolds displayed a significantly high therapeutic effect and less biotoxicity. This work provides an alternative strategy to design smart visual scaffolds for tumor therapy and regenerative medicine.

Gold Nanoparticles as Radiosensitizers in Cancer Radiotherapy

The rapid development of nanotechnology offers a variety of potential therapeutic strategies for cancer treatment. High atomic element nanomaterials are often utilized as radiosensitizers due to their unique photoelectric decay characteristics. Among them, gold nanoparticles (GNPs) are one of the most widely investigated and are considered to be an ideal radiosensitizers for radiotherapy due to their high X-ray absorption and unique physicochemical properties. Over the last few decades, multi-disciplinary studies have focused on the design and optimization of GNPs to achieve greater dosing capability and higher therapeutic effects and highlight potential mechanisms for radiosensitization of GNPs. Although the radiosensitizing potential of GNPs has been widely recognized, its clinical translation still faces many challenges. This review analyses the different roles of GNPs as radiosensitizers in cancer radiotherapy and summarizes recent advances. In addition, the underlying mechanisms of GNP radiosensitization, including physical, chemical and biological mechanisms are discussed, which may provide new directions for the optimization and clinical transformation of next-generation GNPs.

Host CD39 Deficiency Affects Radiation-Induced Tumor Growth Delay and Aggravates Radiation-Induced Normal Tissue Toxicity

The ectonucleoside triphosphate diphosphohydrolase (CD39)/5′ ectonuclotidase (CD73)-dependent purinergic pathway emerges as promising cancer target. Yet, except for own previous work revealing a pathogenic role of CD73 and adenosine in radiation-induced lung fibrosis, the role of purinergic signaling for radiotherapy outcome remained elusive. Here we used C57BL/6 wild-type (WT), CD39 knockout (CD39^−/−), and CD73 knockout (CD73^−/−) mice and hind-leg tumors of syngeneic murine Lewis lung carcinoma cells (LLC1) to elucidate how host purinergic signaling shapes the growth of LLC1 tumors to a single high-dose irradiation with 10 Gy in vivo. In complementary in vitro experiments, we examined the radiation response of LLC1 cells in combination with exogenously added ATP or adenosine, the proinflammatory and anti-inflammatory arms of purinergic signaling. Finally, we analyzed the impact of genetic loss of CD39 on pathophysiologic lung changes associated with lung fibrosis induced by a single-dose whole-thorax irradiation (WTI) with 15 Gy. Loss of CD73 in the tumor host did neither significantly affect tumor growth nor the radiation response of the CD39/CD73-negative LLC1 tumors. In contrast, LLC1 tumors exhibited a tendency to grow faster in CD39^−/− mice compared to WT mice. Even more important, tumors grown in the CD39-deficient background displayed a significantly reduced tumor growth delay upon irradiation when compared to irradiated tumors grown on WT mice. CD39 deficiency caused only subtle differences in the immune compartment of irradiated LLC1 tumors compared to WT mice. Instead, we could associate the tumor growth and radioresistance-promoting effects of host CD39 deficiency to alterations in the tumor endothelial compartment. Importantly, genetic deficiency of CD39 also augmented the expression level of fibrosis-associated osteopontin in irradiated normal lungs and exacerbated radiation-induced lung fibrosis at 25 weeks after irradiation. We conclude that genetic loss of host CD39 alters the tumor microenvironment, particularly the tumor microvasculature, and thereby promotes growth and radioresistance of murine LLC1 tumors. In the normal tissue loss of host, CD39 exacerbates radiation-induced adverse late effects. The suggested beneficial roles of host CD39 on the therapeutic ratio of radiotherapy suggest that therapeutic strategies targeting CD39 in combination with radiotherapy have to be considered with caution.

Understanding Nanoparticle Toxicity to Direct a Safe-by-Design Approach in Cancer Nanomedicine

Nanomedicine is a rapidly growing field that uses nanomaterials for the diagnosis, treatment and prevention of various diseases, including cancer. Various biocompatible nanoplatforms with diversified capabilities for tumor targeting, imaging, and therapy have materialized to yield individualized therapy. However, due to their unique properties brought about by their small size, safety concerns have emerged as their physicochemical properties can lead to altered pharmacokinetics, with the potential to cross biological barriers. In addition, the intrinsic toxicity of some of the inorganic materials (i.e., heavy metals) and their ability to accumulate and persist in the human body has been a challenge to their translation. Successful clinical translation of these nanoparticles is heavily dependent on their stability, circulation time, access and bioavailability to disease sites, and their safety profile. This review covers preclinical and clinical inorganic-nanoparticle based nanomaterial utilized for cancer imaging and therapeutics. A special emphasis is put on the rational design to develop non-toxic/safe inorganic nanoparticle constructs to increase their viability as translatable nanomedicine for cancer therapies.

Nanoparticle dose enhancement of synchrotron radiation in PRESAGE dosimeters

The physical absorbed dose enhancement by the inclusion of gold and bismuth nanoparticles fabricated into water-equivalent PRESAGE dosimeters was investigated. Nanoparticle-loaded water-equivalent PRESAGE dosimeters were irradiated with superficial, synchrotron and megavoltage X-ray beams. The change in optical density of the dosimeters was measured using UV-Vis spectrophotometry pre- and post-irradiation using a wavelength of 630 nm. Dose enhancement was measured for 5 nm and 50 nm monodispersed gold nanoparticles, 5-50 nm polydispersed bismuth nanoparticles, and 80 nm monodispersed bismuth nanoparticles at concentrations from 0.25 mM to 2 mM. The dose enhancement was highest for the 95.3 keV mean energy synchrotron beam (16-32%) followed by the 150 kVp superficial beam (12-21%) then the 6 MV beam (2-5%). The bismuth nanoparticle-loaded dosimeters produced a larger dose enhancement than the gold nanoparticle-loaded dosimeters in the synchrotron beam for the same concentration. For the superficial and megavoltage beams the dose enhancement was similar for both species of nanoparticles. The dose enhancement increased with nanoparticle concentration in the dosimeters; however, there was no observed nanoparticle size dependence on the dose enhancement.

Roadmap for metal nanoparticles in radiation therapy: current status, translational challenges, and future directions

This roadmap outlines the potential roles of metallic nanoparticles (MNPs) in the field of radiation therapy. MNPs made up of a wide range of materials (from Titanium, Z = 22, to Bismuth, Z = 83) and a similarly wide spectrum of potential clinical applications, including diagnostic, therapeutic (radiation dose enhancers, hyperthermia inducers, drug delivery vehicles, vaccine adjuvants, photosensitizers, enhancers of immunotherapy) and theranostic (combining both diagnostic and therapeutic), are being fabricated and evaluated. This roadmap covers contributions from experts in these topics summarizing their view of the current status and challenges, as well as expected advancements in technology to address these challenges.

Advancements in nanotechnology for the diagnosis and treatment of multiple myeloma

Multiple myeloma (MM), known as a tumor of plasma cells, is not only refractory but also has a high relapse rate, and is the second-most common hematologic tumor after lymphoma. It is often accompanied by multiple osteolytic damage, hypercalcemia, anemia, and renal insufficiency. In terms of diagnosis, conventional detection methods have many limitations, such as it is invasive and time-consuming and has low accuracy. Measures to change these limitations are urgently needed. At the therapeutic level, although the survival of MM continues to prolong with the advent of new drugs, MM remains incurable and has a high recurrence rate. With the development of nanotechnology, nanomedicine has become a powerful way to improve the current diagnosis and treatment of MM. In this review, the research progress and breakthroughs of nanomedicine in MM will be presented. Meanwhile, both superiorities and challenges of nanomedicine were discussed. As a new idea for the diagnosis and treatments of MM, nanomedicine will play a very important role in the research field of MM.

Increased carcinoembryonic antigen expression on the surface of lung cancer cells using gold nanoparticles during radiotherapy

PURPOSE

Tumor-associated antigens are a promising target of immunotherapy approaches for cancer treatments but rely on sufficient expression of the target antigen. This study investigates the expression of the carcinoembryonic antigen (CEA) on the surface of irradiated lung cancer cells in vitro using gold nanoparticles as radio-enhancer.

METHODS

Human lung carcinoma cells A549 were irradiated and expression of CEA on the cell surface measured by flow cytometry 3 h, 24 h, and 72 h after irradiation to doses of 2 Gy, 6 Gy, 10 Gy, and 20 Gy in the presence or absence of 0.1 mg/ml or 0.5 mg/ml gold nanoparticles. CEA expression was measured as median fluorescent intensity and percentage of CEA-positive cells.

RESULTS

An increase in CEA expression was observed with both increasing radiation dose and time. There was doubling in median fluorescent intensity 24 h after 20 Gy irradiation and 72 h after 6 Gy irradiation. Use of gold nanoparticles resulted in additional significant increase in CEA expression. Change in cell morphology included swelling of cells and increased internal complexity in accordance with change in CEA expression.

CONCLUSIONS

This study showed an increase in CEA expression on human lung carcinoma cells following irradiation. Increase in expression was observed with increasing radiation dose and in a time dependent manner up to 72 h post irradiation. The results further showed that gold nanoparticles can significantly increase CEA expression following radiotherapy.

Noninvasive imaging of tumor hypoxia after nanoparticle-mediated tumor vascular disruption

We have previously demonstrated that endothelial targeting of gold nanoparticles followed by external beam irradiation can cause specific tumor vascular disruption in mouse models of cancer. The induced vascular damage may lead to changes in tumor physiology, including tumor hypoxia, thereby compromising future therapeutic interventions. In this study, we investigate the dynamic changes in tumor hypoxia mediated by targeted gold nanoparticles and clinical radiation therapy (RT). By using noninvasive whole-body fluorescence imaging, tumor hypoxia was measured at baseline, on day 2 and day 13, post-tumor vascular disruption. A 2.5-fold increase (P<0.05) in tumor hypoxia was measured two days after combined therapy, resolving by day 13. In addition, the combination of vascular-targeted gold nanoparticles and radiation therapy resulted in a significant (P<0.05) suppression of tumor growth. This is the first study to demonstrate the tumor hypoxic physiological response and recovery after delivery of vascular-targeted gold nanoparticles followed by clinical radiation therapy in a human non-small cell lung cancer athymic Foxn1nu mouse model.

Anti-MUC1-C Antibody-Conjugated Nanoparticles Potentiate the Efficacy of Fractionated Radiation Therapy

PURPOSE

Heavy-metal chelators and inorganic nanoparticles (NPs) have been examined as potential radioenhancers to increase the efficacy of external beam radiation therapy for various cancers. Most of these agents have, unfortunately, displayed relatively poor pharmacokinetic properties, which limit the percentage of injected dose (%ID/g) that localizes to tumors and which shorten the window for effective radiation enhancement due to rapid tumor washout.

METHODS AND MATERIALS

To address these challenges, we sought to conjugate gadolinium-based ultrasmall (<5 nm) NPs to an antibody directed against the oncogenic MUC1-C subunit that is overexpressed on the surface of many different human cancer types. The binding of the anti-MUC1-C antibody 3D1 to MUC1-C on the surface of a cancer cell is associated with its internalization and, thereby, to effective intracellular delivery of the antibody-associated payload, promoting its effective tumor retention. As such, we examined whether systemically administered anti-MUC1-C antibody-conjugated, gadolinium-based NPs (anti-MUC1-C/NPs) could accumulate within cell-line xenograft models of MUC1-C-expressing (H460) lung and (E0771) breast cancers to improve the efficacy of radiation therapy (XRT).

RESULTS

The %ID/g of anti-MUC1-C/NPs that accumulated within tumors was found to be similar to that of their unconjugated counterparts (6.6 ± 1.4 vs 5.9 ± 1.7 %ID/g, respectively). Importantly, the anti-MUC1-C/NPs demonstrated prolonged retention in in vivo tumor microenvironments; as a result, the radiation boost was maintained during the course of fractionated therapy (3 × 5.2 Gy). We found that by administering anti-MUC1-C/NPs with XRT, it was possible to significantly augment tumor growth inhibition and to prolong the animals' overall survival (46.2 ± 3.1 days) compared with the administration of control NPs with XRT (31.1 ± 2.4 days) or with XRT alone (27.3 ± 1.6 days; P < .01, log-rank).

CONCLUSIONS

These findings suggest that anti-MUC1-C/NPs could be used to enhance the effectiveness of radiation therapy and potentially to improve clinical outcomes.

Overcoming the biological barriers in the tumor microenvironment for improving drug delivery and efficacy

The delivery of drugs to tumors by nanoparticles is a rapidly growing field. However, the complex tumor microenvironment (TME) barriers greatly hinder drug delivery to tumors. In this study, we first summarized the barriers in TME, including anomalous vasculature, rigid extracellular matrix, hypoxia, acidic pH, irregular enzyme level, altered metabolism pathway and immunosuppressive conditions. To overcome these barriers, many strategies have been developed, such as modulating TME, active targeting by ligand modification and biomimetic strategies, and TME-responsive drug delivery strategies to improve nanoparticle penetration, cellular uptake and drug release. Although extensive progress has been achieved, there are still many challenges, which are discussed in the last section. Overall, we carefully discuss the landscape of TME, development for improving drug delivery, and challenges that need to be further addressed.

Nanoparticle mediated cancer immunotherapy

The versatility and nanoscale size have helped nanoparticles (NPs) improve the efficacy of conventional cancer immunotherapy and opened up exciting approaches to combat cancer. This review first outlines the tumor immune evasion and the defensive tumor microenvironment (TME) that hinders the activity of host immune system against tumor. Then, a detailed description on how the NP based strategies have helped improve the efficacy of conventional cancer vaccines and overcome the obstacles led by TME. Sustained and controlled drug delivery, enhanced cross presentation by immune cells, co-encapsulation of adjuvants, inhibition of immune checkpoints and intrinsic adjuvant like properties have aided NPs to improve the therapeutic efficacy of cancer vaccines. Also, NPs have been efficient modulators of TME. In this context, NPs facilitate better penetration of the chemotherapeutic drug by dissolution of the inhibitory meshwork formed by tumor associated cells, blood vessels, soluble mediators and extra cellular matrix in TME. NPs achieve this by suppression, modulation, or reprogramming of the immune cells and other mediators localised in TME. This review further summarizes the applications of NPs used to enhance the efficacy of cancer vaccines and modulate the TME to improve cancer immunotherapy. Finally, the hurdles faced in commercialization and translation to clinic have been discussed and intriguingly, NPs owe great potential to emerge as clinical formulations for cancer immunotherapy in near future.

Use of 3-D Contrast-Enhanced Ultrasound to Evaluate Tumor Microvasculature After Nanoparticle-Mediated Modulation

A cost-effective method for serial in vivo imaging of tumor microvasculature has been developed. We evaluated acoustic angiography (AA) for visualizing and assessing non-small cell lung tumor (A549) microvasculature in mice before and after tumor vascular disruption by vascular-targeted gold nanoparticles and radiotherapy. Standard B-mode and microbubble-enhanced AA images were acquired at pre- and post-treatment time points. Using these modes, a new metric, 50% vessel penetration depth, was developed to characterize the 3-D spatial heterogeneity of microvascular networks. We observed an increase in tumor perfusion after radiation-induced vascular disruption, relative to control animals. This was also visualized in vessel morphology mode, which revealed a loss in vessel integrity. We found that tumors with poorly perfused vasculature at day 0 exhibited a reduced growth rate over time. This suggested a new method to reduce in-group treatment response variability using pre-treatment microvessel maps to objectively identify animals for study removal.

Self-Propelled Gemini-like LMWH-Scaffold Nanodrugs for Overall Tumor Microenvironment Manipulation via Macrophage Reprogramming and Vessel Normalization

Angiogenesis is the hallmark of melanoma that nurtures the tumor microenvironment (TME) for rapid tumor progression. Vessel normalization could benefit melanoma treatment through TME reconstruction, while its limited duration and extent are still the drag. Herein, two kinds of look-like nanodrugs, called Gemini-like nanodrugs (GLnano), were constructed separately with the same scaffold of antiangiogenic low molecular weight heparin (LMWH) and mixed upon administration in vivo. For one, doxorubicin (DOX) was encapsulated into LMWH-chrysin nanodrug (LCY) with DSPE-PEG-anisamide decoration (D-LCA nanodrugs) for active targeting and direct cell killing toward melanoma cells. For another, matrix metalloproteinases (MMPs)-sensitive peptide was conjugated to LMWH to encapsulate celecoxib (Cel) (C-Lpep nanodrugs), disassembling in TME by MMPs and releasing Cel for M2-to-M1 reprogramming of tumor-associated macrophages. Our results showed that GLnano could remarkably elongate the vessel normalization window up to 12 days with the highest pericyte coverage of nearly 75%, compared to only 4 days by LCY monotherapy. Furthermore, GLnano could spontaneously form the "treatment-delivery" loop to promote nanodrugs toward deep tumor regions, leading to a potent tumor inhibition, metastasis prevention, and overall TME improvements.

X-rays-optimized delivery of radiolabeled albumin for cancer theranostics

Exploiting the specific biological behaviors of the metabolizable nano-drugs assisted by X-rays exposure will be benefit for the optimization of radiotherapy-based combination therapy. Herein, Human serum albumin (HSA) nanoparticle, a familiar and metabolizable nanomaterial, is selected to investigate the changes of tumor accumulation and retention under X-rays exposure. Caveolin-1, an important protein which has positive correlation with cell uptake of nanomaterials, is expressed increasingly under X-rays exposure, resulting the enhanced cell uptake and prolonged tumor retention of HSA nanoparticles. After being labeled by radioactive iodine-125, HSA could be used for SPECT/CT imaging of mice. Moreover, it discovered that ¹²⁵I-HSA nanoparticles possess much longer-time retention time in pre-irradiated tumor than that of controlled tumor. Using this strategy, the therapeutic efficiency of ¹³¹I-HSA injected mice after irradiating their tumors by X-rays is better than that of opposite sequence treated mice. In order to further improve the targeting ability of HSA, GNQEQVSPLTLLKXC peptide (A15) is conjugated to HSA nanoparticles for targeting the thrombosis in the tumor tissue triggered by X-rays exposure, realizing the high tumor accumulation of ¹³¹I-HSA assisted by X-rays exposure. Therefore, taking advantage of the increased expression of Caveolin-1 and the induced thrombosis under X-rays exposure, we optimized the delivery of radiolabeled HSA via enhancing the cell uptake and prolonging tumor retention of HSA for cancer combination therapy. Our work make contribution to guide the clinical albumin based combination therapy.

Proteomic analysis of intracellular protein corona of nanoparticles elucidates nano-trafficking network and nano-bio interactions

The merits of nanomedicines are significantly impacted by the surrounding biological environment. Similar to the protein corona generated on the surface of nanoparticles in the circulation system, the intracellular protein corona (IPC) might be formed on nanoparticles when transported inside the cells. However, little is known currently about the formation of IPC and its possible biological influence.

Methods: Caco-2 cells, a classical epithelial cell line, were cultured in Transwell plates to form a monolayer. Gold nanoparticles (AuNPs) were prepared as the model nanomedicine due to their excellent stability. Here we focused on identifying IPC formed on the surface of AuNPs during cell transport. The nanoparticles in the basolateral side of the Caco-2 monolayer were collected and analyzed by multiple techniques to verify IPC formation. High-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based proteomics was utilized to analyze the composition of IPC proteins. In particular, we established a dual-filtration strategy to exclude various interference in IPC identification. Based on the subcellular localization of specific IPC proteins, we elicited the nano-trafficking network of AuNPs. The transport pathways of AuNPs identified by proteomic analysis were also verified by various conventional technologies. Finally, we explored the influence of IPC on the uptake and stress response of endothelium.

Results: The existence of IPC was demonstrated on the surface of AuNPs, in which 227 proteins were identified. Among them, 40 proteins were finally ascertained as the specific IPC proteins. The subcellular location analysis indicated that these “specific” IPC proteins could back-track the transport pathways of nanoparticles in the epithelial cell monolayer. According to the subcellular distribution of IPC proteins and co-localization, we discovered a new pathway of nanoparticles from endosomes to secretory vesicles which was dominant during the transcytosis. After employing conventional imageology and pharmacology strategies to verify the result of proteomic analysis, we mapped a comprehensive intracellular transport network. Our study also revealed the merits of IPC analysis, which could readily elucidate the molecular mechanisms of transcytosis. Besides, the IPC proteins increased the uptake and stress response of endothelium, which was likely mediated by extracellular matrix and mitochondrion-related IPC proteins.

Conclusion: The comprehensive proteomic analysis of IPC enabled tracing of transport pathways in epithelial cells as well as revealing the biological impact of nanoparticles on endothelium.

Applications of Surface Modification Technologies in Nanomedicine for Deep Tumor Penetration

The impermeable barrier of solid tumors due to the complexity of their components limits the treatment effect of nanomedicine and hinders its clinical translation. Several methods are available to increase the penetrability of nanomedicine, yet they are too complex to be effective, operational, or practical. Surface modification employs the characteristics of direct contact between multiphase surfaces to achieve the most direct and efficient penetration of solid tumors. Furthermore, their simple operation makes their use feasible. In this review, the latest surface modification strategies for the penetration of nanomedicine into solid tumors are summarized and classified into "bulldozer strategies" and "mouse strategies." Additionally, the evaluation methods, existing problems, and the development prospects of these technologies are discussed.

Platelet-Mimicking Biotaxis Targeting Vasculature-Disrupted Tumors for Cascade Amplification of Hypoxia-Sensitive Therapy

Tumorous vasculature plays key roles in sustaining tumor growth. Vascular disruption is accompanied by internal coagulation along with platelet recruitment and the resulting suppression of oxygen supply. We intend to artificially create this physiological process to establish the mutual feedback between vascular disruption and platelet-mimicking biotaxis for the cascade amplification of hypoxia-dependent therapy. To prove this concept, mesoporous silica nanoparticles are co-loaded with a hypoxia-activated prodrug (HAP) and a vessel-disruptive agent and then coated with platelet membranes. Upon entering into tumors, our nanotherapeutic can disrupt local vasculature for tumor inhibition. This platelet membrane-coated nanoplatform shares the hemorrhage-tropic function with parental platelets and can be persistently recruited by the vasculature-disrupted tumors. In this way, the intratumoral vascular disruption and tumor targeting are biologically interdependent and mutually reinforced. Relying on this mutual feedback, tumorous hypoxia was largely promoted by more than 20-fold, accounting for the effective recovery of the HAP's cytotoxicity. Consequently, our bioinspired nanodesign has demonstrated highly specific and effective antitumor potency via the biologically driven cooperation among intratumoral vascular disruption, platelet-mimicking biotaxis, cascade hypoxia amplification, and hypoxia-sensitive chemotherapy. This study offers a paradigm of correlating the therapeutic design with the physiologically occurring events to achieve better therapy performance.

Exploiting Current Understanding of Hypoxia Mediated Tumour Progression for Nanotherapeutic Development

Hypoxia is one of the most common phenotypes of malignant tumours. Hypoxia leads to the increased activity of hypoxia-inducible factors (HIFs), which regulate the expression of genes controlling a raft of pro-tumour phenotypes. These include maintenance of the cancer stem cell compartment, epithelial-mesenchymal transition (EMT), angiogenesis, immunosuppression, and metabolic reprogramming. Hypoxia can also contribute to the tumour progression in a HIF-independent manner via the activation of a complex signalling network pathway, including JAK-STAT, RhoA/ROCK, NF-κB and PI3/AKT. Recent studies suggest that nanotherapeutics offer a unique opportunity to target the hypoxic microenvironment, enhancing the therapeutic window of conventional therapeutics. In this review, we summarise recent advances in understanding the impact of hypoxia on tumour progression, while outlining possible nanotherapeutic approaches for overcoming hypoxia-mediated resistance.

Selective Priming of Tumor Blood Vessels by Radiation Therapy Enhances Nanodrug Delivery

Effective drug delivery is restricted by pathophysiological barriers in solid tumors. In human pancreatic adenocarcinoma, poorly-permeable blood vessels limit the intratumoral permeation and penetration of chemo or nanotherapeutic drugs. New and clinically viable strategies are urgently sought to breach the neoplastic barriers that prevent effective drug delivery. Here, we present an original idea to boost drug delivery by selectively knocking down the tumor vascular barrier in a human pancreatic cancer model. Clinical radiation activates the tumor endothelial-targeted gold nanoparticles to induce a physical vascular damage due to the high photoelectric interactions. Active modulation of these tumor neovessels lead to distinct changes in tumor vascular permeability. Noninvasive MRI and fluorescence studies, using a short-circulating nanocarrier with MR-sensitive gadolinium and a long-circulating nanocarrier with fluorescence-sensitive nearinfrared dye, demonstrate more than two-fold increase in nanodrug delivery, post tumor vascular modulation. Functional changes in altered tumor blood vessels and its downstream parameters, particularly, changes in Ktrans (permeability), Kep (flux rate), and Ve (extracellular interstitial volume), reflect changes that relate to augmented drug delivery. The proposed dual-targeted therapy effectively invades the tumor vascular barrier and improve nanodrug delivery in a human pancreatic tumor model and it may also be applied to other nonresectable, intransigent tumors that barely respond to standard drug therapies.

[Elemental imaging using laser-induced breakdown spectroscopy: latest medical applications]

Multi-elemental imaging of soft tissues using Laser-induced breakdown spectroscopy, also known as LIBS, allows for the direct visualization of the distribution of endogenous or exogenous elements within tissues. LIBS was used to image the kinetics of metal nanoparticles in elimination organs, but also the physiological distribution of biological elements in situ and the topography of chemicals or metals in exposed human tissues. Based on our experience and recent literature in the field of imaging the elemental content of animal and human specimens, this review describes the principle and characteristics of the instrument, technical considerations for setting up experiments with LIBS, its advantages, limitations and possibilities for pre-clinical and medical applications.

Targeted Gold Nanocluster-Enhanced Radiotherapy of Prostate Cancer

For over a hundred years, X-rays have been a main component of the radiotherapeutic approaches to treat cancer. Yet, to date, no radiosensitizer has been developed to selectively target prostate cancer. Gold has excellent X-ray absorptivity and is used as a radiotherapy enhancing material. In this work, ultrasmall Au25 nanoclusters (NCs) are developed for selective prostate cancer targeting, radiotherapy enhancement, and rapid clearance from the body. Targeted-Au25 NCs are rapidly and selectively taken up by prostate cancer in vitro and in vivo and also have fast renal clearance. When combined with X-ray irradiation of the targeted cancer tissues, radiotherapy is significantly enhanced. The selective targeting and rapid clearance of the nanoclusters may allow reductions in radiation dose, decreasing exposure to healthy tissue and making them highly attractive for clinical translation.

Nanomaterial-Based Modulation of Tumor Microenvironments for Enhancing Chemo/Immunotherapy

The tumor microenvironment (TME) has drawn considerable research attention as an alternative target for nanomedicine-based cancer therapy. Various nanomaterials that carry active substances have been designed to alter the features or composition of the TME and thereby improve the delivery and efficacy of anticancer chemotherapeutics. These alterations include disruption of the extracellular matrix and tumor vascular systems to promote perfusion or modulate hypoxia. Nanomaterials have also been used to modulate the immunological microenvironment of tumors. In this context, nanomaterials have been shown to alter populations of cancer-associated fibroblasts, tumor-associated macrophages, regulatory T cells, and myeloid-derived suppressor cells. Despite considerable progress, nanomaterial-based TME modulation must overcome several limitations before this strategy can be translated to clinical trials, including issues related to limited tumor tissue penetration, tumor heterogeneity, and immune toxicity. In this review, we summarize recent progress and challenges of nanomaterials used to modulate the TME to enhance the efficacy of anticancer chemotherapy and immunotherapy.