Near-infrared light-activated red-emitting upconverting nanoplatform for T1-weighted magnetic resonance imaging and photodynamic therapy

Temoporfin-Conjugated PEGylated Poly(N,N-dimethylacrylamide)-Coated Upconversion Colloid for NIR-Induced Photodynamic Therapy of Pancreatic Cancer

Photodynamic therapy (PDT) has the potential to cure pancreatic cancer with minimal side effects. Visible wavelengths are primarily used to activate hydrophobic photosensitizers, but in clinical practice, these wavelengths do not sufficiently penetrate deeper localized tumor cells. In this work, NaYF4:Yb3+,Er3+,Fe2+ upconversion nanoparticles (UCNPs) were coated with polymer and labeled with meta-tetra(hydroxyphenyl)chlorin (mTHPC; temoporfin) to enable near-infrared light (NIR)-triggered PDT of pancreatic cancer. The coating consisted of alendronate-terminated poly[N,N-dimethylacrylamide-co-2-aminoethylacrylamide]-graft-poly(ethylene glycol) [P(DMA-AEM)-PEG-Ale] to ensure the chemical and colloidal stability of the particles in aqueous physiological fluids, thereby also improving the therapeutic efficacy. The designed particles were well tolerated by the human pancreatic adenocarcinoma cell lines CAPAN-2, PANC-1, and PA-TU-8902. After intratumoral injection of mTHPC-conjugated polymer-coated UCNPs and subsequent exposure to 980 nm NIR light, excellent PDT efficacy was achieved in tumor-bearing mice.

Molecularly Targeted Lanthanide Nanoparticles for Cancer Theranostic Applications

Injectable colloidal solutions of lanthanide oxides (nanoparticles between 10 and 100 nm in size) have demonstrated high biocompatibility and no toxicity when the nanoparticulate units are functionalized with specific biomolecules that molecularly target various proteins in the tumor microenvironment. Among the proteins successfully targeted by functionalized lanthanide nanoparticles are folic receptors, fibroblast activation protein (FAP), gastrin-releasing peptide receptor (GRP-R), prostate-specific membrane antigen (PSMA), and integrins associated with tumor neovasculature. Lutetium, samarium, europium, holmium, and terbium, either as lanthanide oxide nanoparticles or as nanoparticles doped with lanthanide ions, have demonstrated their theranostic potential through their ability to generate molecular images by magnetic resonance, nuclear, optical, or computed tomography imaging. Likewise, photodynamic therapy, targeted radiotherapy (neutron-activated nanoparticles), drug delivery guidance, and image-guided tumor therapy are some examples of their potential therapeutic applications. This review provides an overview of cancer theranostics based on lanthanide nanoparticles coated with specific peptides, ligands, and proteins targeting the tumor microenvironment.

Reactive oxidative species (ROS)-based nanomedicine for BBB crossing and glioma treatment: current status and future directions

Glioma is the most common primary intracranial tumor in adults with poor prognosis. Current clinical treatment for glioma includes surgical resection along with chemoradiotherapy. However, the therapeutic efficacy is still unsatisfactory. The invasive nature of the glioma makes it impossible to completely resect it. The presence of blood-brain barrier (BBB) blocks chemotherapeutic drugs access to brain parenchyma for glioma treatment. Besides, tumor heterogeneity and hypoxic tumor microenvironment remarkably limit the efficacy of radiotherapy. With rapid advances of nanotechnology, the emergence of a new treatment approach, namely, reactive oxygen species (ROS)-based nanotherapy, provides an effective approach for eliminating glioma via generating large amounts of ROS in glioma cells. In addition, the emerging nanotechnology also provides BBB-crossing strategies, which allows effective ROS-based nanotherapy of glioma. In this review, we summarized ROS-based nanomedicine and their application in glioma treatment, including photodynamic therapy (PDT), photothermal therapy (PTT), chemodynamic therapy (CDT), sonodynamic therapy (SDT), radiation therapy, etc. Moreover, the current challenges and future prospects of ROS-based nanomedicine are also elucidated with the intention to accelerate its clinical translation.

Systematic Review of Photodynamic Therapy in Gliomas

Over the last 20 years, gliomas have made up over 89% of malignant CNS tumor cases in the American population (NIH SEER). Within this, glioblastoma is the most common subtype, comprising 57% of all glioma cases. Being highly aggressive, this deadly disease is known for its high genetic and phenotypic heterogeneity, rendering a complicated disease course. The current standard of care consists of maximally safe tumor resection concurrent with chemoradiotherapy. However, despite advances in technology and therapeutic modalities, rates of disease recurrence are still high and survivability remains low. Given the delicate nature of the tumor location, remaining margins following resection often initiate disease recurrence. Photodynamic therapy (PDT) is a therapeutic modality that, following the administration of a non-toxic photosensitizer, induces tumor-specific anti-cancer effects after localized, wavelength-specific illumination. Its effect against malignant glioma has been studied extensively over the last 30 years, in pre-clinical and clinical trials. Here, we provide a comprehensive review of the three generations of photosensitizers alongside their mechanisms of action, limitations, and future directions.

Photon Upconversion in Small Molecules

Upconversion (UC) is a process that describes the emission of shorter-wavelength light compared to that of the excitation source. Thus, UC is also referred to as anti-Stokes emission because the excitation wavelength is longer than the emission wavelength. UC materials are used in many fields, from electronics to medicine. The objective of using UC in medical research is to synthesize upconversion nanoparticles (UCNPs) composed of a lanthanide core with a coating of adsorbed dye that will generate fluorescence after excitation with near-infrared light to illuminate deep tissue. Emission occurs in the visible and UV range, and excitation mainly in the near-infrared spectrum. UC is observed for lanthanide ions due to the arrangement of their energy levels resulting from f-f electronic transitions. Organic compounds and transition metal ions are also able to form the UC process. Biocompatible UCNPs are designed to absorb infrared light and emit visible light in the UC process. Fluorescent dyes are adsorbed to UCNPs and employed in PDT to achieve deeper tissue effects upon irradiation with infrared light. Fluorescent UCNPs afford selectivity as they may be activated only by illumination of an area of diseased tissue, such as a tumor, with infrared light and are by themselves atoxic in the absence of infrared light. UCNP constructs can be monitored as to their location in the body and uptake by cancer cells, aiding in evaluation of exact doses required to treat the targeted cancer. In this paper, we review current research in UC studies and UCNP development.

Upconversion Nanostructures Applied in Theranostic Systems

Upconversion (UC) nanostructures, which can upconvert near-infrared (NIR) light with low energy to visible or UV light with higher energy, are investigated for theranostic applications. The surface of lanthanide (Ln)-doped UC nanostructures can be modified with different functional groups and bioconjugated with biomolecules for therapeutic systems. On the other hand, organic molecular-based UC nanostructures, by using the triplet-triplet annihilation (TTA) UC mechanism, have high UC quantum yields and do not require high excitation power. In this review, the major UC mechanisms in different nanostructures have been introduced, including the Ln-doped UC mechanism and the TTA UC mechanism. The design and fabrication of Ln-doped UC nanostructures and TTA UC-based UC nanostructures for theranostic applications have been reviewed and discussed. In addition, the current progress in the application of UC nanostructures for diagnosis and therapy has been summarized, including tumor-targeted bioimaging and chemotherapy, image-guided diagnosis and phototherapy, NIR-triggered controlled drug releasing and bioimaging. We also provide insight into the development of emerging UC nanostructures in the field of theranostics.

Metal-Based Nanostructured Therapeutic Strategies for Glioblastoma Treatment-An Update

Glioblastoma (GBM) is the most commonly diagnosed and most lethal primary malignant brain tumor in adults. Standard treatments are ineffective, and despite promising results obtained in early phases of experimental clinical trials, the prognosis of GBM remains unfavorable. Therefore, there is need for exploration and development of innovative methods that aim to establish new therapies or increase the effectiveness of existing therapies. One of the most exciting new strategies enabling combinatory treatment is the usage of nanocarriers loaded with chemotherapeutics and/or other anticancer compounds. Nanocarriers exhibit unique properties in antitumor therapy, as they allow highly efficient drug transport into cells and sustained intracellular accumulation of the delivered cargo. They can be infused into and are retained by GBM tumors, and potentially can bypass the blood-brain barrier. One of the most promising and extensively studied groups of nanostructured therapeutics are metal-based nanoparticles. These theranostic nanocarriers demonstrate relatively low toxicity, thus they might be applied for both diagnosis and therapy. In this article, we provide an update on metal-based nanostructured constructs in the treatment of GBM. We focus on the interaction of metal nanoparticles with various forms of electromagnetic radiation for use in photothermal, photodynamic, magnetic hyperthermia and ionizing radiation sensitization applications.

Recent development of contrast agents for magnetic resonance and multimodal imaging of glioblastoma

Glioblastoma (GBM) as the most common primary malignant brain tumor exhibits a high incidence and degree of malignancy as well as poor prognosis. Due to the existence of formidable blood–brain barrier (BBB) and the aggressive growth and infiltrating nature of GBM, timely diagnosis and treatment of GBM is still very challenging. Among different imaging modalities, magnetic resonance imaging (MRI) with merits including high soft tissue resolution, non-invasiveness and non-limited penetration depth has become the preferred tool for GBM diagnosis. Furthermore, multimodal imaging with combination of MRI and other imaging modalities would not only synergistically integrate the pros, but also overcome the certain limitation in each imaging modality, offering more accurate morphological and pathophysiological information of brain tumors. Since contrast agents contribute to amplify imaging signal output for unambiguous pin-pointing of tumors, tremendous efforts have been devoted to advances of contrast agents for MRI and multimodal imaging. Herein, we put special focus on summary of the most recent advances of not only MRI contrast agents including iron oxide-, manganese (Mn)-, gadolinium (Gd)-, ¹⁹F- and copper (Cu)-incorporated nanoplatforms for GBM imaging, but also dual-modal or triple-modal nanoprobes. Furthermore, potential obstacles and perspectives for future research and clinical translation of these contrast agents are discussed. We hope this review provides insights for scientists and students with interest in this area.

Advances in magnetic resonance imaging contrast agents for glioblastoma-targeting theranostics

Glioblastoma (GBM) is the most aggressive malignant brain tumour, with a median survival of 3 months without treatment and 15 months with treatment. Early GBM diagnosis can significantly improve patient survival due to early treatment and management procedures. Magnetic resonance imaging (MRI) using contrast agents is the preferred method for the preoperative detection of GBM tumours. However, commercially available clinical contrast agents do not accurately distinguish between GBM, surrounding normal tissue and other cancer types due to their limited ability to cross the blood–brain barrier, their low relaxivity and their potential toxicity. New GBM-specific contrast agents are urgently needed to overcome the limitations of current contrast agents. Recent advances in nanotechnology have produced alternative GBM-targeting contrast agents. The surfaces of nanoparticles (NPs) can be modified with multimodal contrast imaging agents and ligands that can specifically enhance the accumulation of NPs at GBM sites. Using advanced imaging technology, multimodal NP-based contrast agents have been used to obtain accurate GBM diagnoses in addition to an increased amount of clinical diagnostic information. NPs can also serve as drug delivery systems for GBM treatments. This review focuses on the research progress for GBM-targeting MRI contrast agents as well as MRI-guided GBM therapy.

Polymer-Functionalized Upconversion Nanoparticles for Light/Imaging-Guided Drug Delivery

The strong upconversion luminescence (UCL) of upconversion nanoparticles (UCNPs) endows the nanoparticles with attractive features for combined imaging and drug delivery. UCNPs convert near-infrared (NIR) light into light of shorter wavelengths such as light in the ultraviolet (UV) and visible regions, which can be used for light-guided drug delivery. Although light-responsive drug delivery systems as such have been known for many years, their application in medicine is limited, as strong UV-light can be damaging to tissue; moreover, UV light will not penetrate deeply into the skin, an issue that UCNPs can now address. However, UCNPs, as obtained after synthesis, are usually hydrophobic and require further surface functionalization to be stable in plasma. Polymers can serve as versatile surface coatings, as they can provide good colloidal stability, prevent the formation of a protein corona, provide a matrix for drugs, and be stimuli-responsive. In this Review, we provide a brief overview of the most recent progress in the synthesis of UCNPs with different shapes/sizes. We will then discuss the purpose of polymer coating for drug delivery before summarizing the strategies to coat UCNPs with various polymers. We will introduce the different polymers that have so far been used to coat UCNPs with the purpose to create a drug delivery system, focusing in detail on light-responsive polymers. To expand the application of UCNPs to allow photothermal therapy or magnetic resonance imaging (MRI) or to simply enhance the loading capacity of drugs, UCNPs were often combined with other materials to generate multifunctional nanoparticles such as carbon-based NPs and nanoMOFs. We then conclude with a discussion on drug loading and release and summarize the current knowledge on the toxicity of these polymer-coated UCNPs.

Long-Term Tri-Modal In Vivo Tracking of Engrafted Cartilage-Derived Stem/Progenitor Cells Based on Upconversion Nanoparticles

Cartilage-derived stem/progenitor cells (CSPCs) are a potential choice for seed cells in osteal and chondral regeneration, and the outcomes of their survival and position distribution in vivo form the basis for the investigation of their mechanism. However, the current use of in vivo stem cell tracing techniques in laboratories is relatively limited, owing to their high operating costs and cytotoxicity. Herein, we performed tri-modal in vivo imaging of CSPCs during subcutaneous chondrogenesis using upconversion nanoparticles (UCNPs) for 28 days. Distinctive signals at accurate positions were acquired without signal noise from X-ray computed tomography, magnetic resonance imaging, and upconversion luminescence. The measured intensities were all significantly proportional to the cell numbers, thereby enabling real-time in vivo quantification of the implanted cells. However, limitations of the detectable range of cell numbers were also observed, owing to the imaging shortcomings of UCNPs, which requires further improvement of the nanoparticles. Our study explores the application value of upconversion nanomaterials in the tri-modal monitoring of implanted stem cells and provides new perspectives for future clinical translation.

Self-Assembly Iron Oxide Nanoclusters for Photothermal-Mediated Synergistic Chemo/Chemodynamic Therapy

Methods

Superparamagnetic iron oxide nanoclusters (SPIOCs) were located within the core, which resulted in high photothermal conversion and outstanding generation of reactive oxygen species (ROS). The shell consisted of a human serum albumin- (HSA-) paclitaxel (PTX) layer, which extended the blood circulation time and ensured the effectiveness of the chemotherapy. Arg-Gly-Asp peptides (RGD) were linked to the naked cysteine moieties in HSA to promote the specific targeting of human glioma U87 cells by α_vβ₃ integrins. Continuous near-infrared light irradiation triggered and promoted the synergistic chemo/CDT therapy through the photothermal effect.

Results

Our SPIOCs@HSA-RGD nanoplatform showed well biocompatibility and could target glioma specifically. Photothermal conversion and ROS burst were detected after continuous 808 nm light irradiation, and a significant antitumor effect was achieved.

Conclusion

Experimental in vitro and in vivo evaluations showed that our photothermal-mediated chemo/CDT therapy could efficiently inhibit tumor growth and is therefore promising for cancer therapy.

MRI-traceable theranostic nanoparticles for targeted cancer treatment

Current cancer therapies, including chemotherapy and radiotherapy, are imprecise, non-specific, and are often administered at high dosages - resulting in side effects that severely impact the patient's overall well-being. A variety of multifunctional, cancer-targeted nanotheranostic systems that integrate therapy, imaging, and tumor targeting functionalities in a single platform have been developed to overcome the shortcomings of traditional drugs. Among the imaging modalities used, magnetic resonance imaging (MRI) provides high resolution imaging of structures deep within the body and, in combination with other imaging modalities, provides complementary diagnostic information for more accurate identification of tumor characteristics and precise guidance of anti-cancer therapy. This review article presents a comprehensive assessment of nanotheranostic systems that combine MRI-based imaging (T1 MRI, T2 MRI, and multimodal imaging) with therapy (chemo-, thermal-, gene- and combination therapy), connecting a range of topics including hybrid treatment options (e.g. combined chemo-gene therapy), unique MRI-based imaging (e.g. combined T1-T2 imaging, triple and quadruple multimodal imaging), novel targeting strategies (e.g. dual magnetic-active targeting and nanoparticles carrying multiple ligands), and tumor microenvironment-responsive drug release (e.g. redox and pH-responsive nanomaterials). With a special focus on systems that have been tested in vivo, this review is an essential summary of the most advanced developments in this rapidly evolving field.

Light: A Magical Tool for Controlled Drug Delivery

Light is a particularly appealing tool for on-demand drug delivery due to its noninvasive nature, ease of application and exquisite temporal and spatial control. Great progress has been achieved in the development of novel light-driven drug delivery strategies with both breadth and depth. Light-controlled drug delivery platforms can be generally categorized into three groups: photochemical, photothermal, and photoisomerization-mediated therapies. Various advanced materials, such as metal nanoparticles, metal sulfides and oxides, metal-organic frameworks, carbon nanomaterials, upconversion nanoparticles, semiconductor nanoparticles, stimuli-responsive micelles, polymer- and liposome-based nanoparticles have been applied for light-stimulated drug delivery. In view of the increasing interest in on-demand targeted drug delivery, we review the development of light-responsive systems with a focus on recent advances, key limitations, and future directions.

Hypoxia-Responsive Lipid-Polymer Nanoparticle-Combined Imaging-Guided Surgery and Multitherapy Strategies for Glioma

Glioma is the most prevalent type of malignant brain tumor and is usually very aggressive. Because of the high invasiveness and aggressive proliferative growth of glioma, it is difficult to resect completely or cure with surgery. Residual glioma cells are a primary cause of postoperative recurrence. Herein, we describe a hypoxia-responsive lipid polymer nanoparticle (LN) for fluorescence-guided surgery, chemotherapy, photodynamic therapy (PDT), and photothermal therapy (PTT) combination multitherapy strategies targeting glioma. The hypoxia-responsive LN [LN (DOX + ICG)] contains a hypoxia-responsive component poly(nitroimidazole)₂₅ [P-(Nis)₂₅], the glioma-targeting peptide angiopep-2 (A2), indocyanine green (ICG), and doxorubicin (DOX). LN (DOX + ICG) comprises four distinct functional components: (1) A2: A2 modified nanoparticles effectively target gliomas, enhancing drug concentration in gliomas; (2) P-(Nis)₂₅: (i) the hydrophobic component of LN (DOX + ICG) with hypoxia responsive ability to encapsulate DOX and ICG; (ii) allows rapid release of DOX from LN (DOX + ICG) after 808 nm laser irradiation; (3) ICG: (i) ICG allows imaging-guided surgery, combining PDT and PTT therapies; (ii) upon irradiation with an 808 nm laser, ICG creates a hypoxic environment; (4) DOX inhibits glioma growth. This work demonstrates that LN (DOX + ICG) might provide a novel clinical approach to preventing post-surgical recurrence of glioma.

c(RGDfK)- and ZnTriMPyP-Bound Polymeric Nanocarriers for Tumor-Targeted Photodynamic Therapy

Active targeting strategies are currently being extensively investigated in order to enhance the selectivity of photodynamic therapy. The aim of the present research was to evaluate whether the external decoration of nanopolymeric carriers with targeting peptides could add more value to a photosensitizer formulation and increase antitumor therapeutic efficacy and selectivity. To this end, we assessed PLGA-PLA-PEG nanoparticles (NPs) covalently attached to a hydrophilic photosensitizer 5-[4-azidophenyl]-10,15,20-tri-(N-methyl-4-pyridinium)porphyrinato zinc (II) trichloride (ZnTriMPyP) and also to c(RGDfK) peptides, in order to target α_v β₃ integrin-expressing cells. In vitro phototoxicity investigations showed that the ZnTriMPyP-PLGA-PLA-PEG-c(RGDfK) nanosystem is effective at submicromolar concentrations, is devoid of dark toxicity, successfully targets α_v β₃ integrin-expressing cells and is 10-fold more potent than related nanosystems where the PS is occluded instead of covalently bound.

Photodynamic Therapy for the Treatment of Glioblastoma

Glioblastoma is the most common form of adult brain cancer and remains one of the deadliest of human cancers. The current standard-of-care involves maximal tumor resection followed by treatment with concurrent radiation therapy and the chemotherapy temozolomide. Recurrence after this therapy is nearly universal within 2 years of diagnosis. Notably, >80% of recurrence is found in the region adjacent to the resection cavity. The need for improved local control in this region, thus remains unmet. The FDA approval of 5-aminolevulinic acid (5-ALA) for fluorescence guided glioblastoma resection renewed interests in leveraging this agent as a means to administer photodynamic therapy (PDT). Here we review the general principles of PDT as well as the available literature on PDT as a glioblastoma therapeutic platform.

Integrin αvβ3 Receptor Overexpressing on Tumor-Targeted Positive MRI-Guided Chemotherapy

Multifunctional nanomaterials with targeted imaging and chemotherapy have high demand with great challenge. Herein, we rationally aimed to design multifunctional drug delivery systems by RGD-modified chitosan (CH)-coated nanoneedles (NDs) of gadolinium arsenate (RGD-CH-Gd-AsNDs). These NDs have multifunctionality for imaging and targeted therapy. NDs on intravenous administration demonstrated significant accumulation of As ions/species in tumor tissues, which was monitored by the change in T₁-weighted magnetic resonance (MR) imaging. Moreover, NDs were well opsonized in cells with high specificity, subsequently inducing apoptosis to the HepG2 cells. Consequent to this, the in vivo results demonstrated biosafety, enhanced tumor targeting, and tumor regression in a subcutaneously transplanted xenograft model in nude mice. These RGD-CH-Gd-AsNDs have great potential, and we anticipate that they could serve as a novel platform for real-time T₁-weighted MR diagnosis and chemotherapy.

A fullerene based hybrid nanoparticle facilitates enhanced photodynamic therapy via changing light source and oxygen consumption

Recently, fullerene (C60) has been widely used as a nano photosensitizer (PS) for tumor related photodynamic therapy (PDT). However, current PDT based on C60 is severely restricted by the visible light source (shallow tissue penetrating depth) and oxygen dependent (tumor hypoxia). Therefore, taking advantages of the surface plasmon resonance (SPR) effect of gold nanoparticles (GNPs) and "electronic sponge" property of C60, a C60 based hybrid nanostructured photosensitizer (C60@GNPs) with high light stability, near infrared light (NIR) excitation, and oxygen non-dependent properties was rational designed according to the mechanism of PDT. Compared with C60, after GNPs in-situ synthesis, the PDT mechanism of C60@GNPs changed from type II to type I, and the main product of PDT changed from singlet oxygen to hydroxyl radicals. Furthermore, C60@GNPs hybrid could efficiently generate hydroxyl radicals under NIR light excitation even in the hypoxia condition. These results suggest that C60@GNPs hybrid has a great potential for in vivo PDT applications.

Second near-infrared photodynamic therapy and chemotherapy of orthotopic malignant glioblastoma with ultra-small Cu2-xSe nanoparticles

The treatment of malignant glioblastoma is a huge challenge due to the existence of the blood-brain barrier. Herein, we report the treatment of orthotopic malignant glioblastoma with imaging guided second near-infrared (NIR-II) photodynamic therapy and chemotherapy by using drug-loaded ultra-small Cu2-xSe theranostic nanoparticles (NPs). Ultra-small Cu2-xSe NPs possess a strong absorbance in the NIR-II window, and their absorption at 1064 nm is around 2 times that at 808 nm. Their strong NIR-II absorbance and the deeper-tissue penetration of NIR-II light ensure excellent photodynamic therapy performance under irradiation with a 1064 nm laser. We also demonstrate that ultra-small Cu2-xSe NPs can produce vast amounts of reactive oxygen species via electron transfer (for ˙OH generation) and energy transfer (for 1O2 generation) mechanisms under irradiation. In addition, these NPs can be effectively and locally transported into orthotopic malignant glioblastoma with the assistance of focused ultrasound. The deposited Cu2-xSe NPs can be used for photoacoustic imaging to guide the combined NIR-II photodynamic therapy and chemotherapy. The results show that the tumor growth can be significantly suppressed. This work demonstrates the great potential of drug-loaded ultra-small Cu2-xSe NPs as a promising therapeutic agent for the treatment of orthotopic malignant glioblastoma.

DOX Loaded Aggregation-induced Emission Active Polymeric Nanoparticles as a Fluorescence Resonance Energy Transfer Traceable Drug Delivery System for Self-indicating Cancer Therapy

In this study, an AIE-active polymer (FTP) was successfully prepared and employed to load anti-cancer drug doxorubicin (DOX) for self-indicating cancer therapy via dual FRET process. Our results demonstrated that the FTP polymer could self-assemble into nanoparticles (NPs) in aqueous solutions to give strong fluorescence emission via intramolecular FRET process. The DOX loaded FTP NPs (drug loading content: 21.77%) were homogeneous particles with size around 50 nm and neutral surface charge, which showed preferable colloidal stability, hemolysis and selective drug release with comparable in vivo antitumor effects to DOX·HCl. In particular, the FRET process between FTP (donor) and DOX (acceptor) could serve as indicator for monitoring the in vitro and in vivo drug release profile, which might be a promising platform to realize real-time monitoring of drug localization and release during the delivery process. STATEMENT OF SIGNIFICANCE: 1. An amphiphilic polymer containing aggregation-induced emission segments and polyethylene glycol (PEG) chains (FTP) was firstly synthesized, which is capable of exerting strong fluorescence via intramolecular Förster resonance energy transfer (FRET) in the aggregate state. 2. The FTP polymer could self-assembled into homogeneous nanoparticles in aqueous environment with decent DOX loading capacity. 3. The DOX loaded FTP nanoparticles can afford FRET-traceable monitoring of the drug release both in vitro and in vivo.

5-aminolevulinic acid photodynamic therapy for the treatment of high-grade gliomas

INTRODUCTION

Photodynamic therapy (PDT) is a two-step treatment involving the administration of a photosensitive agent followed by its activation at a specific light wavelength for targeting of tumor cells.

MATERIALS/METHODS

A comprehensive review of the literature was performed to analyze the indications for PDT, mechanisms of action, use of different photosensitizers, the immunomodulatory effects of PDT, and both preclinical and clinical studies for use in high-grade gliomas (HGGs).

RESULTS

PDT has been approved by the United States Food and Drug Administration (FDA) for the treatment of premalignant and malignant diseases, such as actinic keratoses, Barrett's esophagus, esophageal cancers, and endobronchial non-small cell lung cancers, as well as for the treatment of choroidal neovascularization. In neuro-oncology, clinical trials are currently underway to demonstrate PDT efficacy against a number of malignancies that include HGGs and other brain tumors. Both photosensitizers and photosensitizing precursors have been used for PDT. 5-aminolevulinic acid (5-ALA), an intermediate in the heme synthesis pathway, is a photosensitizing precursor with FDA approval for PDT of actinic keratosis and as an intraoperative imaging agent for fluorescence-guided visualization of malignant tissue during glioma surgery. New trials are underway to utilize 5-ALA as a therapeutic agent for PDT of the intraoperative resection cavity and interstitial PDT for inoperable HGGs.

CONCLUSION

PDT remains a promising therapeutic approach that requires further study in HGGs. Use of 5-ALA PDT permits selective tumor targeting due to the intracellular metabolism of 5-ALA. The immunomodulatory effects of PDT further strengthen its use for treatment of HGGs and requires a better understanding. The combination of PDT with adjuvant therapies for HGGs will need to be studied in randomized, controlled studies.

Approaches to physical stimulation of metallic nanoparticles for glioblastoma treatment

Glioblastoma multiforme (GBM) is the most aggressive malignant brain tumor. Despite new knowledges on the genetic characteristics, conventional therapy for GBM, tumor resection followed by radiotherapy and chemotherapy using temozolomide is limited in efficacy due to high rate of recurrence. GBM is indeed one of the most complex and difficult cancer to treat mainly due to its highly invasive properties and the standard treatments are thus rarely curative. Major challenges in the treatment of GBM are the limitation of irreversible brain damage, the infiltrative part of the tumor which is the ultimate cause of recurrence, the difficulty of identifying tumor margins and disseminated tumor cells, and the transport across the blood-brain barrier in order to obtain a sufficient therapeutic effect for pharmalogical agents. Considering these limitations, this review explores the in vivo potential of metal-based nanoparticles for hyperthermia, radiotherapy and photodynamic therapy. This article describes and clearly outlines the recent in vivo advances using innovative therapeutic metallic nanoparticles such as iron oxide, silver, gadolinium and gold nanoparticles.