The reactive oxygen species (ROS)-mediated mechanism is the major cause underlying the efficacy of photodynamic therapy (PDT). The PDT procedure is based on the cascade of synergistic effects between light, a photosensitizer (PS) and oxygen, which greatly favors the spatiotemporal control of the treatment. This procedure has also evoked several unresolved challenges at different levels including (i) the limited penetration depth of light, which restricts traditional PDT to superficial tumours; (ii) oxygen reliance does not allow PDT treatment of hypoxic tumours; (iii) light can complicate the phototherapeutic outcomes because of the concurrent heat generation; (iv) specific delivery of PSs to sub-cellular organelles for exerting effective toxicity remains an issue; and (v) side effects from undesirable white-light activation and self-catalysation of traditional PSs. Recent advances in nanotechnology and nanomedicine have provided new opportunities to develop ROS-generating systems through photodynamic or non-photodynamic procedures while tackling the challenges of the current PDT approaches. In this review, we summarize the current status and discuss the possible opportunities for ROS generation for cancer therapy. We hope this review will spur pre-clinical research and clinical practice for ROS-mediated tumour treatments.

Reactive oxygen species generating systems meeting challenges of photodynamic cancer therapy

Reactive oxygen species (ROS) play an essential role in regulating various physiological functions of living organisms. The intrinsic biochemical properties of ROS, which underlie the mechanisms ne...

Reactive Oxygen Species (ROS)-Based Nanomedicine.

Photodynamic therapy (PDT) has been applied to treat a wide range of medical conditions, including wet age-related macular degeneration psoriasis, atherosclerosis, viral infection and malignant cancers. However, the tissue penetration limitation of excitation light hinders the widespread clinical use of PDT. To overcome this “Achilles' heel”, deep PDT, a novel type of phototherapy, has been developed for the efficient treatment of deep-seated diseases. Based on the different excitation sources, including near-infrared (NIR) light, X-ray radiation, and internal self-luminescence, a series of deep PDT techniques have been explored to demonstrate the advantages of deep cancer therapy over conventional PDT excited by ultraviolet-visible (UV-Vis) light. In particular, the featured applications of deep PDT, such as organelle-targeted deep PDT, hypoxic deep PDT and deep PDT-involved multimodal synergistic therapy are discussed. Finally, the future development and potential challenges of deep PDT are also elucidated for clinical translation. It is highly expected that deep PDT will be developed as a versatile, depth/oxygen-independent and minimally invasive strategy for treating a variety of malignant tumours at deep locations.

Overcoming the Achilles' heel of photodynamic therapy.

Tens of millions of contrast-enhanced magnetic resonance imaging (MRI) exams are performed annually around the world. The contrast agents, which improve diagnostic accuracy, are almost exclusively small, hydrophilic gadolinium(III) based chelates. In recent years concerns have arisen surrounding the long-term safety of these compounds, and this has spurred research into alternatives. There has also been a push to develop new molecularly targeted contrast agents or agents that can sense pathological changes in the local environment. This comprehensive review describes the state of the art of clinically approved contrast agents, their mechanism of action, and factors influencing their safety. From there we describe different mechanisms of generating MR image contrast such as relaxation, chemical exchange saturation transfer, and direct detection and the types of molecules that are effective for these purposes. Next we describe efforts to make safer contrast agents either by increasing relaxivity, increasing resistance to metal ion release, or by moving to gadolinium(III)-free alternatives. Finally we survey approaches to make contrast agents more specific for pathology either by direct biochemical targeting or by the design of responsive or activatable contrast agents.

Chemistry of MRI Contrast Agents: Current Challenges and New Frontiers

Hypoxia development in tumor is closely associated with its increased aggressiveness and strong resistance to therapy, leading to the poor prognosis in several cancer types. Clinically, invasive oxygen microelectrode and high dosage radiotherapy are often utilized to accurately detect and effectively fight hypoxia. Recently, however, there has been a surge of interdisciplinary research aiming at developing functional molecules and nanomaterials that can be used to noninvasively image and efficiently treat hypoxic tumors. In this review, we will provide an overview of the reports published to date on the imaging and therapy of hypoxic tumors. First, we will present the design concepts and engineering of various hypoxia-responsive probes that can be applied to image hypoxia noninvasively, in an order of fluorescent imaging, positron emission tomography, magnetic resonance imaging, and photoacoustic imaging. Then, we will summarize the up-to-date functional nanomaterials which can be used for the effective t...

Chemical Design and Synthesis of Functionalized Probes for Imaging and Treating Tumor Hypoxia

Dysregulated remodeling of the extracellular matrix (ECM) can lead to excessive accumulation of ECM proteins (primarily collagen, elastin/ tropoelastin, fibronectin and fibrin) resulting in tissue fibrosis. In many pathologies, changes in the molecular pattern of ECM components have been related to the progression and severity of fibrosis. Thus, magnetic resonance imaging (MRI) probes sensing specific ECM components hold promise for accurate staging of fibrotic diseases. This paper focuses on gadolinium-based contrast agents (GBCA) targeted to ECM components, including structural proteins and enzymes. According to available examples, they can be grouped into: 1) GBCA conjugated to targeting vectors that recognize and non-covalently bind to specific sites on the molecular target; 2) GBCA carrying a reactive chemical function able to bind covalently to the complementary chemical function of the molecular target; and 3) enzyme-responsive probes, whose relaxivity and pharmacokinetics change after enzymatic processing. Pros and cons of each approach are discussed. 

Extracellular Matrix Targeted MRI Probes

Summary. 153 Sm and 166 Ho complexes with two series of tetraazamacrocyclic ligands containing methylcarboxylate and/or methylphosphonate pendant arms were synthesized and their charge, lipophilicity, protein binding and in vitro and in vivo behaviour evaluated. The first series has the same backbone, a 14-membered tetraazamacrocycle containing a pyridine unit with different pendant arms, namely methylcarboxylates (ac3py14) or methylphosphonates (MeP2py14 and P3py14). The second series comprises 12- to 14-membered tetraazamacrocycles having methylcarboxylates and/or methylphosphonates as pendant arms (trans-DO2A2P, TRITA, TRITP, TETA and TETP). The 153 Sm/ 166 Ho complexes with the 14-membered tetraazamacrocycles containing the pyridine unit are neutral, hydrophilic, have a significant plasmatic protein binding, are unstable in vivo and present a slow rate of radioactivity excretion and high hepatic retention. 153 Sm/ 166 Ho complexes with the 12- to 14-membered tetraazamacrocycles are quantitatively prepared, except those with TETP. These complexes are hydrophilic, have an overall negative charge and present a medium to low plasmatic protein binding. The 153 Sm/ 166 Ho-trans-DO2A2P, 153 Sm/ 166 Ho-TRITA and 166 Ho-TRITP complexes are stable in vitro and in vivo ,p resenting a rapid clearance from main organs and a high rate of whole body radioactivity excretion. Biological profile of 153 Sm/ 166 Ho-TRITA complexes makes them promising candidates for therapy when conjugated to a biomolecule, while 166 Ho-TRITP is potentially useful for bone targeting due to

Radiolanthanides / Tetraazamacrocycles / Phosphonates / Carboxylates / Biodistribution / Therapy

Fibrosis occurs in various tissues as a reparative response to injury or damage. If excessive, however, fibrosis can lead to tissue scarring and organ failure, which is associated with high morbidity and mortality. Collagen is a key driver of fibrosis, with type I and type III collagen being the primary types involved in many fibrotic diseases. Unlike conventional protocols used to immobilize other proteins (e.g., elastin, albumin, fibronectin, etc.), comprehensive protocols to reproducibly immobilize different types of collagens in order to produce stable coatings are not readily available. Immobilizing collagen is surprisingly challenging because multiple experimental conditions may affect the efficiency of immobilization, including the type of collagen, the pH, the temperature, and the type of microplate used. Here, a detailed protocol to reproducibly immobilize and quantify type I and III collagens resulting in stable and reproducible gels/films is provided. Furthermore, this work demonstrates how to perform, analyze, and interpret in vitro time-resolved fluorescence binding studies to investigate the interactions between collagens and candidate collagen-binding compounds (e.g., a peptide conjugated to a metal chelate carrying, for example, europium [Eu(III)]). Such an approach can be universally applied to various biomedical applications, including the field of molecular imaging to develop targeted imaging probes, drug development, cell toxicity studies, cell proliferation studies, and immunoassays.

Optimized Methods for the Surface Immobilization of Collagens and Collagen Binding Assays.

The present invention relates to particles, useful for drug release detection, comprising: at least one luminescent metal complex of formula [Ln].[L], wherein: Ln is a lanthanide ion, L is an organic ligand comprising a hydrophilic unit with at least 6 chelating groups chosen from the group consisting of hydroxyl, carboxyl, optionally in the carboxylate form, carbonyl, ether, phosphonate, phosphinate, thiolate, amino and imino functions, and - at least one drug comprising a conjugated aromatic system, wherein said drug is not covalently bonded to the metal complex, said particle having a size comprised from 3 nm to 2 000 nm, and wherein the distribution of the metal complex and the drug within the particle is such that the mean distance between a drug molecule and a metal complex is less than 15 nm.

Sara Lacerda

Papers

Extracellular Matrix Targeted MRI Probes

Radiolanthanides / Tetraazamacrocycles / Phosphonates / Carboxylates / Biodistribution / Therapy

Optimized Methods for the Surface Immobilization of Collagens and Collagen Binding Assays.

Particles comprising luminescent lanthanide complexes