Singlet Oxygen In Vivo: It Is All about Intensity—Part 2

Recently, we reported induced anoxia as a limiting factor for photodynamic tumor therapy (PDT). This effect occurs in vivo if the amount of generated singlet oxygen that undergoes chemical reactions with cellular components exceeds the local oxygen supply. The amount of generated singlet oxygen depends mainly on photosensitizer (PS) accumulation, efficiency, and illumination intensity. With illumination intensities above a certain threshold, singlet oxygen is limited to the blood vessel and the nearest vicinity; lower intensities allow singlet oxygen generation also in tissue which is a few cell layers away from the vessels. While all experiments so far were limited to light intensities above this threshold, we report experimental results for intensities at both sides of the threshold for the first time, giving proof for the described model. Using time-resolved optical detection in NIR, we demonstrate characteristic, illumination intensity-dependent changes in signal kinetics of singlet oxygen and photosensitizer phosphorescence in vivo. The described analysis allows for better optimization and coordination of PDT drugs and treatment, as well as new diagnostic methods based on gated PS phosphorescence, for which we report a first in vivo feasibility test.Brigitte and Konstanze Wegener FoundationSojo UniversityGrant-in-Aid for Scientific Research on Scientific Research (C)Ministry of Health of Czech RepublicEuropean Union—Next Generation EUPeer Reviewe

Polymers in Medicine. 76th Prague Meeting on Macromolecules

The 76th Prague Meeting on macromolecules abstract book summarized the oral and poster presentation dealing with polymers in medicine. During the conference was presented 7 main, 13 special and 10 lectures by world known scientist in the field of drug delivery (Prof. Duncan, Prof. Maeda, Prof. Kataoka, Prof. Kopecek), 67 poster presentations and 7 oral presentations of young scientists

Book of Abstracts and Programme. Polymers in Medicine 2019 - Prague Meeting on Macromolecules /83./

The Book of abstracts and programme contains the summaries of all the contributions to the international conference “Polymers in Medicine 2019”. The participants presented 43 lectures and 35 posters. Main conference topics were: Polymers for nanomedicine, Stimuliresponsive polymers, Polymers for advanced drug delivery, Polymers for biomedical applications, Biomaterials for tissue engineering

Polymerní protirakovinná léčiva s pH- a enzymaticky závislou aktivací

Water-soluble synthetic polymers and their conjugates with antibodies, oligopeptides or saccharides proved a potential targetable drug delivery system. Recently, copolymers of N-(2-hydroxypropyl)methacrylamide (HPMA) have been developed in our laboratory as polymeric carriers of drugs

HPMA Copolymer-Based Nanomedicines in Controlled Drug Delivery

Recently, numerous polymer materials have been employed as drug carrier systems in medicinal research, and their detailed properties have been thoroughly evaluated. Water-soluble polymer carriers play a significant role between these studied polymer systems as they are advantageously applied as carriers of low-molecular-weight drugs and compounds, e.g., cytostatic agents, anti-inflammatory drugs, antimicrobial molecules, or multidrug resistance inhibitors. Covalent attachment of carried molecules using a biodegradable spacer is strongly preferred, as such design ensures the controlled release of the drug in the place of a desired pharmacological effect in a reasonable time-dependent manner. Importantly, the synthetic polymer biomaterials based on N-(2-hydroxypropyl) methacrylamide (HPMA) copolymers are recognized drug carriers with unique properties that nominate them among the most serious nanomedicines candidates for human clinical trials. This review focuses on advances in the development of HPMA copolymer-based nanomedicines within the passive and active targeting into the place of desired pharmacological effect, tumors, inflammation or bacterial infection sites. Specifically, this review highlights the safety issues of HPMA polymer-based drug carriers concerning the structure of nanomedicines. The main impact consists of the improvement of targeting ability, especially concerning the enhanced and permeability retention (EPR) effect

Polyelectrolyte complex formation and stability when mixing polyanions and polycations in salted media: A model study related to the case of body fluids

International audienc

Singlet Oxygen In Vivo: It Is All about Intensity

The presented work addresses the influence of illumination intensity on the amount and locations of singlet oxygen generation in tumor tissue. We used time-resolved optical detection at the typical emission wavelength around 1270 nm and at 1200 nm where there is no singlet oxygen phosphorescence to determine the phosphorescence kinetics. The discussed data comprise in vivo measurements in tumor-laden HET-CAM and mice. The results show that illumination that is too intense is a major issue, affecting many PDT treatments and all singlet oxygen measurements in vivo so far. In such cases, photosensitization and oxygen consumption exceed oxygen supply, limiting singlet oxygen generation to the blood vessels and walls, while photosensitizers in the surrounding tissue will likely not participate. Being a limitation for the treatment, on one hand, on the other, this finding offers a new method for tumor diagnosis when using photosensitizers exploiting the EPR effect. In contrast to high-intensity PDT, some papers reported successful treatment with nanoparticular drugs using much lower illumination intensity. The question of whether, with such illumination, singlet oxygen is indeed generated in areas apart from vessels and walls, is addressed by numerical analysis. In addition, we discuss how to perform measurements at such low intensities.Academy of Sciences of Czech RepublicPeer Reviewe

Tris-(Nitrilotriacetic Acid)-Decorated Polymer Conjugates as Tools for Immobilization and Visualization of His-Tagged Proteins

Recombinant proteins are commonly expressed with artificial affinity tags for purification, immobilization and characterization. The most frequently used tag, His-tag, is a sequence of consecutive histidine residues fused to the protein of interest. Specialized small molecules that bind His-tag are primarily used for purification, while antibodies are used for protein analysis. However, various issues may be encountered with the use of antibodies. Low inherent stability, the difficulty of introducing chemical modifications, and often-unreliable batch-to-batch consistency are among the limiting factors that call for better alternatives. Recently described polymer conjugates of N-(2-hydroxypropyl) methacrylamide and low-molecular-weight functional ligands, so-called iBodies, are antibody mimetics capable of replacing antibodies in biochemical applications. We tailored this system for methods utilizing His-tag by accessorizing the polymer carrier with tris-nitrilotriacetic acid targeting ligands. These anti-polyHis iBodies are additionally accessorized with fluorophores, enabling detection, and biotin ligands, enabling immobilization. Here, we characterized anti-polyHis iBodies and explored their use as antibody mimetics. We tested their stability, as well as the influence of different metal mediators and His-tag lengths on binding. With high affinity and stability, iBodies represent a new alternative for immobilization and visualization of His-tagged proteins

Anti-Lymphoma Efficacy Comparison of Anti-Cd20 Monoclonal Antibody-Targeted and Non-Targeted Star-Shaped Polymer-Prodrug Conjugates

Here we describe the synthesis and biological properties of two types of star-shaped polymer-doxorubicin conjugates: non-targeted conjugate prepared as long-circulating high-molecular-weight (HMW) polymer prodrugs with a dendrimer core and a targeted conjugate with the anti-CD20 monoclonal antibody (mAb) rituximab (RTX). The copolymers were linked to the dendrimer core or to the reduced mAb via one-point attachment forming a star-shaped structure with a central antibody or dendrimer surrounded by hydrophilic polymer chains. The anticancer drug doxorubicin (DOX) was attached to the N-(2-hydroxypropyl)methacrylamide (HPMA)-based copolymer chain in star polymer systems via a pH-labile hydrazone linkage. Such polymer-DOX conjugates were fairly stable in aqueous solutions at pH 7.4, and the drug was readily released in mildly acidic environments at pH 5–5.5 by hydrolysis of the hydrazone bonds. The cytotoxicity of the polymer conjugates was tested on several CD20-positive or negative human cell lines. Similar levels of in vitro cytotoxicity were observed for all tested polymer conjugates regardless of type or structure. In vivo experiments using primary cell-based murine xenograft models of human diffuse large B-cell lymphoma confirmed the superior anti-lymphoma efficacy of the polymer-bound DOX conjugate when compared with the original drug. Targeting with RTX did not further enhance the anti-lymphoma efficacy relative to the non-targeted star polymer conjugate. Two mechanisms could play roles in these findings: changes in the binding ability to the CD-20 receptor and a significant loss of the immunological properties of RTX in the polymer conjugates