Biocompatible glyconanomaterials based on HPMA-copolymer for specific targeting of galectin-3.

BACKGROUND: Galectin-3 (Gal-3) is a promising target in cancer therapy with a high therapeutic potential due to its abundant localization within the tumor tissue and its involvement in tumor development and proliferation. Potential clinical application of Gal-3-targeted inhibitors is often complicated by their insufficient selectivity or low biocompatibility. Nanomaterials based on N-(2-hydroxypropyl)methacrylamide (HPMA) nanocarrier are attractive for in vivo application due to their good water solubility and lack of toxicity and immunogenicity. Their conjugation with tailored carbohydrate ligands can yield specific glyconanomaterials applicable for targeting biomedicinally relevant lectins like Gal-3. RESULTS: In the present study we describe the synthesis and the structure-affinity relationship study of novel Gal-3-targeted glyconanomaterials, based on hydrophilic HPMA nanocarriers. HPMA nanocarriers decorated with varying amounts of Gal-3 specific epitope GalNAcß1,4GlcNAc (LacdiNAc) were analyzed in a competitive ELISA-type assay and their binding kinetics was described by surface plasmon resonance. We showed the impact of various linker types and epitope distribution on the binding affinity to Gal-3. The synthesis of specific functionalized LacdiNAc epitopes was accomplished under the catalysis by mutant ß-N-acetylhexosaminidases. The glycans were conjugated to statistic HPMA copolymer precursors through diverse linkers in a defined pattern and density using Cu(I)-catalyzed azide-alkyne cycloaddition. The resulting water-soluble and structurally flexible synthetic glyconanomaterials exhibited affinity to Gal-3 in low µM range. CONCLUSIONS: The results of this study reveal the relation between the linker structure, glycan distribution and the affinity of the glycopolymer nanomaterial to Gal-3. They pave the way to specific biomedicinal glyconanomaterials that target Gal-3 as a therapeutic goal in cancerogenesis and other disorders.

Adaptable polymerization platform for therapeutics with tunable biodegradability.

Biodegradable polymer-based therapeutics have recently become essential drug delivery biomaterials for various bioactive compounds. Biodegradable and biocompatible polymer-based biomaterials fulfill the requirements of these therapeutics because they enable to obtain polymer biomaterials with optimized blood circulation, pharmacokinetics, biodegradability, and renal excretion. Herein, we describe an adaptable polymerization platform employed for the synthesis of long-circulating, stimulus-sensitive and biodegradable biomaterials, therapeutics, or theranostics. Four chain transfer agents (CTA) were designed and successfully synthesized for the reversible addition-fragmentation chain transfer polymerization, allowing the straightforward synthesis of hydrolytically biodegradable structures of block copolymers-based biomaterials. The controlled polymerization using the CTAs enables controlling the half-life of the hydrolytic degradation of polymer precursors in a wide range from 5 h to 21 days. Moreover, the antitumor drug pirarubicin (THP) was successfully conjugated to the polymer biomaterials via a pH-sensitive hydrazone bond for in vitro and in vivo experiments. Polymer conjugates demonstrated superior antitumor efficacy compared to basic linear polymer-based conjugates. Notably, the biodegradable systems, even though those with degradation in the order of hours were selected, increased the half-life of THP in the bloodstream almost two-fold. Indeed, the presented platform design enables the main chain-end specific attachment of targeting ligands or diagnostic molecules. The adaptable polymerization platform design allows tuning of the biodegradability rate, stimuli-sensitive drug bonding, and optimized pharmacokinetics to increase the therapy outcome and system targeting, thus allowing the preparation of targeted or theranostic polymer conjugates. STATEMENT OF SIGNIFICANCE: Biodegradable and biocompatible polymer-based biomaterials are recognized as potential future bioactive nanomedicines. To advance the development of such biomaterials, we developed polymerization platforms utilizing tailored chain transfer agents allowing the straightforward synthesis of hydrolytically degradable polymer biomaterials with tuned biodegradability from hours to several days. The platform allows for the synthesis of long-circulating, stimulus-sensitive and biodegradable biomaterial serving as drug carriers or theranostics. The therapeutic potential was validated by preparation of polymer biomaterials containing pirarubicin, anticancer drug, bound via pH sensitive bond and by showing prolonged blood circulation and increased antitumor activity while keeping the drug side effects low. This work paves the way for future development of biodegradable polymer biomaterials with advanced properties in drug delivery.

Hybrid κ-carrageenan-based polymers showing "schizophrenic" lower and upper critical solution temperatures and potassium responsiveness.

Novel multiresponsive hybrid biocompatible systems of κ-carrageenan-graft-poly(2-isopropyl-2-oxazoline-co-2-butyl-2-oxazoline)s with unique combination of responsiveness to external stimuli were synthesized and studied. The polymer thermoresponsive behavior proved the existence of both lower and upper critical solution temperatures in aqueous milieu, forming gel at lower temperature, a solution at room temperature and cloudy nanophase-separated dispersion at elevated temperature. The limit temperatures can easily be adjusted by the polyoxazoline graft length and grafting density. Moreover, the polymer behavior is additionally dependent on the concentration of potassium ions. The polymers behave similarly as the original κ-carrageenan, and thus, the poly(2-alkyl-2-oxazoline) grafts do not decrease the ability of the κ-carrageenan to form the self-assembled structures. Molecular principles beyond this multistimuli-responsive behavior were elucidated with the use of dynamic light scattering, magnetic resonance and fluorescence measurements as well as atomic force microscopy. These polymers could be used in a wide range of biological applications demanding thermo- and potassium-responsiveness.

Polymer nitric oxide donors potentiate the treatment of experimental solid tumours by increasing drug accumulation in the tumour tissue.

The delivery of nitric oxide (NO) specifically to solid tumours was explored in this study as a strategy to augment the passive accumulation of nanomedicines in tumours induced by the Enhanced Permeability and Retention (EPR) effect. An increase in accumulation was achieved by the binding of the chemical precursor of NO, based on an organic nitrate, to a water-soluble synthetic polymer drug carrier. Four structurally different N-(2-hydroxypropyl)methacrylamide (HPMA)-based polymer NO donors were synthesized. Depending on their chemical structure, two of these donors were hydrolytically stable, while two rapidly released the parent nitrate under acidic conditions, mimicking the intracellular environment. The polymer NO donors were shown to overcome the drawbacks related to low-molecular-weight NO releasing compounds, namely systemic toxicity, lack of site specificity, and fast blood clearance. The NO donors showed intracellular NO release upon incubation with tumour cells. In vivo, they potentiated the EPR effect, resulting in an increased accumulation of polymer-bound cytotoxic drug doxorubicin (Dox) in EL4 T-cell lymphoma inoculated in mice. This led to a better therapeutic outcome in the treatment of lymphoma with the high-molecular-weight polymer conjugates carrying Dox but not in the treatment with the free Dox. The localized augmentation of the EPR effect via the tumour-specific NO delivery system can be viewed as a promising strategy to potentiate polymer-based tumour therapy without increasing systemic toxicity.

Pinocchio cells: morphologically atypical immunologically heterogeneous lymphocytes induced by treatment with interleukin 2.

We describe a novel cell type, the Pinocchio cell, that appears in the peripheral blood of all patients receiving treatment with interleukin 2, up to 20,000 cells/microliter. This cell is characterized by a prominent and granular proboscis with which it attaches to tumor cells and mediates tumor cell lysis. Pinocchio cells are immunologically heterogeneous and express antigens of both T and NK cells; Pinocchio cells are adherent in culture and are more cytolytic than non-adherent cells against NK-sensitive and resistant tumor cells. Incubation of normal whole human blood for 1 h induces Pinocchio morphology of mononuclear white blood cells.