Functionalized hydrogel microparticles prepared by microfluidics and their interaction with tumour marker carbonic anhydrase IX.

Microfluidics allows precise control of the synthesis of microparticles for specific applications, where size and morphology play an important role. In this work, we have introduced microfluidic chip design with dedicated extraction and gelation sections allowing to prepare hydrogel particles in the size range of a red blood cell. The influence of the extractive channel size, alginate concentration and type of storage media on the final size of the prepared alginate microparticles has been discussed. The second part of the work is dedicated to the surface modification of prepared particles using chitosan, pHPMA and the monoclonal antibody molecule, IgG M75. The specific interaction of the antibody molecule with an antigen domain of carbonic anhydrase IX, the transmembrane tumour protein associated with several types of cancer, is demonstrated by fluorescence imaging and compared to an isotypic antibody molecule.

Synthesis of poly[N-(2-hydroxypropyl)methacrylamide] conjugates of inhibitors of the ABC transporter that overcome multidrug resistance in doxorubicin-resistant P388 cells in vitro.

The effects of novel polymeric therapeutics based on water-soluble N-(2-hydroxypropyl)methacrylamide copolymers (P(HPMA)) bearing the anticancer drug doxorubicin (Dox), an inhibitor of ABC transporters, or both, on the viability and the proliferation of the murine monocytic leukemia cell line P388 (parental cell line) and its doxorubicin-resistant subline P388/MDR were studied in vitro. The inhibitor derivatives 5-methyl-4-oxohexanoyl reversin 121 (MeOHe-R121) and 5-methyl-4-oxohexanoyl ritonavir ester (MeOHe-RIT), showing the highest inhibitory activities, were conjugated to the P(HPMA) via the biodegradable pH-sensitive hydrazone bond, and the ability of these conjugates to block the ATP driven P-glycoprotein (P-gp) efflux pump was tested. The P(HPMA) conjugate P-Ahx-NH-N═MeOHe-R121 showed a dose-dependent increase in the ability to sensitize the P388/MDR cells to Dox from 1.5 to 24 µM, and achieved an approximately 50-fold increase in sensitization at 24 µM. The P(HPMA) conjugate P-Ahx-NH-N═MeOHe-RIT showed moderate activity at 6 µM (∼10 times higher sensitization) and increased sensitization by 50-fold at 12 µM. The cytostatic activity of the P(HPMA) conjugate P-Ahx-NH-N═MeOHe-R121(Dox) containing Dox and the P-gp inhibitor MeOHe-R121, both bound via hydrazone bonds to the P(HPMA) carrier, was almost 30 times higher than that of the conjugate P-Ahx-NH-N═Dox toward the P388/MDR cells in vitro. A similar result was observed for P-Ahx-NH-N═MeOHe-RIT(Dox), which exhibited almost 10 times higher cytostatic activity than P-Ahx-NH-N═Dox.

Cell-penetrating peptides: a useful tool for the delivery of various cargoes into cells.

Cell-penetrating compounds are substances that enhance the cellular uptake of various molecular cargoes that do not easily cross the cellular membrane. The majority of cell-penetrating compounds described in the literature are cell-penetrating peptides (CPPs). This review summarizes the various structural types of cell-penetrating compounds, with the main focus on CPPs. The authors present a brief overview of the history of CPPs, discuss the various types of conjugation of CPPs to biologically active cargoes intended for cell internalization, examine the cell-entry mechanisms of CPPs, and report on the applications of CPPs in research and in preclinical and clinical studies.

Micelle-forming HPMA copolymer conjugates of ritonavir bound via a pH-sensitive spacer with improved cellular uptake designed for enhanced tumor accumulation.

We describe design, synthesis, physico-chemical characterization and preliminary biological evaluation of micelle-forming polymer drug conjugates with controlled drug release intended for tumor treatment. The structure of the conjugates was designed to enable tumor tissue- and cell-specific drug release and micelle disassembly to avoid side effects accompanying classic chemotherapy and guarantee safe elimination of the drug-free carrier from the organisms. The amphiphilic polymer conjugates consisted of a hydrophobic hexaleucine block and a hydrophilic block based on the N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer with an antiviral and cytostatic drug, ritonavir, bound through a pH-sensitive spacer. Diblock copolymers with low dispersity (D∼ 1.1) were prepared via reversible addition-fragmentation chain transfer (RAFT) copolymerization using a hexaleucine derivative as a chain transfer agent. The associative properties of the copolymers depend on the hydrophilic polymer block length and the hydrophobic ritonavir content. The micelles dissociated under mild acidic conditions mimicking the environment inside tumor tissue/cells, because of the decrease in polymer hydrophobicity after the rapid release of the hydrophobic drug from the polymer carrier. Unexpectedly, the polymer-ritonavir conjugates internalized into HeLa cells significantly more than the polymers without ritonavir. The enhanced cell penetration and pH-triggered micelle disassembly predetermine the polymer-ritonavir conjugates to become promising tumor-targeted drug carriers.

Doxorubicin bound to a HPMA copolymer carrier through hydrazone bond is effective also in a cancer cell line with a limited content of lysosomes.

We have synthesized conjugates containing doxorubicin (DOX) bound to oligopeptide side chains (GlyGly or GlyPheLeuGly) of a water-soluble copolymer carrier based on poly[N-(2-hydroxypropyl)methacrylamide] (PHPMA) either through proteolytically (PK1 conjugates) [Synthetic polymeric drugs. U.S. Patent 5,037,883 (1991)] or hydrolytically cleavable bond (HC conjugates). Pharmacological efficacy of PK1 and HC conjugates was compared in vitro on murine: T-cell lymphoma EL4, B-cell leukemia BCL1, B-cell lymphoma 38C13, leukemia P388 and Con A-stimulated A/Ph splenocytes and on human: primary (SW480) and metastatic (SW620) colorectal cancer cell lines parent and transfected with Thy 1.2 gene [2] and on erythromyeloid leukemia cell line K 562. Inhibition of proliferation determined by 3[H]-thymidine incorporation revealed that the cytostatic effect of HC conjugates is up to two orders of magnitude higher compared to PK1 conjugates. In some cancer cell lines (SW 620/T, SW 480) the pharmacological activity of HC conjugates is in vitro comparable with the activity of the free drug. Unlike PK1 conjugates, HC conjugates with a lysosomally degradable spacer (GlyPheLeuGly) are less effective compared to HC conjugates containing lysosomally non-degradable spacer (GlyGly). Moreover, HC conjugates exert pronounced anti-proliferative activity also in erythroblastoid leukemia cell line K 562 with a limited content of lysosomes.

Polymeric anticancer drugs with pH-controlled activation.

The paper is dealing with the synthesis and properties of new, nontargeted or antibody-targeted pH-sensitive polymer-doxorubicin (DOX) conjugates designed as anticancer drugs facilitating site-specific therapy. These conjugates are stable and inactive during transport in the body but activate inside target cells as a result of pH changes outside and inside the cells. Cytotoxicity of the conjugates depends on the detailed structure of the polymer and of the spacer between the drug and polymer carrier. In both protective and therapeutic regimes of drug administration, the in vivo antitumor activity of the pH-sensitive conjugates containing DOX was significantly enhanced (T-cell lymphoma EL 4, C57BL/16 mice) in comparison with the free DOX or classic PK1, the PHPMA-DOX conjugate clinically tested at present.

Cathepsin K inhibitor-polymer conjugates: potential drugs for the treatment of osteoporosis and rheumatoid arthritis.

The role of the newly discovered cysteine protease, cathepsin K, in osteoporosis and rheumatoid arthritis is reviewed. The current development of cathepsin K inhibitors and their targeted delivery using synthetic polymer carriers are discussed. Future challenges and possible strategies to improve these delivery systems are addressed.

Poly(ethylene glycol) multiblock copolymer as a carrier of anti-cancer drug doxorubicin.

The synthesis of a novel water-soluble polymer drug carrier system based on biodegradable poly(ethylene glycol) block copolymer is described in this paper. The copolymer consisting of PEG blocks of molecular weight 2000 linked by means of an oligopeptide with amino end groups was prepared by interfacial polycondensation of the diamine and PEG bis(succinimidyl carbonate). The structure of the oligopeptide diamine consisting of glutamic acid and lysine residues was designed as a substrate for cathepsin B, a lysosomal enzyme, which was assumed to be one of the enzymes responsible for the degradation of the polymer carrier in vivo. Each of the oligopeptide blocks incorporated in the carrier contained three carboxylic groups of which some were used for attachment of an anti-cancer drug, doxorubicin (Dox), via a tetrapeptide spacer Gly-Phe-Leu-Gly. This tetrapeptide spacer is susceptible to enzymatic hydrolysis. In vitro release of Dox and the degradation of the polymer chain by cathepsin B as well as preliminary evaluation of in vivo anti-cancer activity of the conjugate are also demonstrated.