Thermo- and pH-sensitive glycosaminoglycans derivatives obtained by controlled grafting of poly(N-isopropylacrylamide).

Poly(N-isopropyl acrylamide) grafted heparin and chondroitin sulfate were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. The copolymers were characterized by NMR, IR, SEC, DLS, SLS and NTA methods. High grafting densities were reached for both glycosaminoglycans. The temperature, pH and polymer concentration affected the low critical solution temperatures values. The increased pNIPAAm chain length, grafting density and concentration led to the sharp phase transition at 35 °C. Spherical nanogels were formed around this temperature. Terminal dodecyl trithiocarbonate groups of the copolymers were reduced to thiols that allowed formation of sensitive nanogels with sharp phase transitions induced by pNIPAAm chains. The copolymers showed no toxicity to the ocular cells and they provided the prolonged release of dexamethasone phosphate at 37 °C. These copolymers are interesting alternatives for ocular drug delivery.

Macroporous monoliths for biodegradation study of polymer particles considered as drug delivery systems.

Nanostructures based on biodegradable polymers are often considered as drug delivery systems. The properties of these nanomaterails towards in vitro biodegradation are very important and usually are studied using the model physiological conditions. In this work the novel approach based on application of monolithic immobilized enzyme reactors (IMERs) as the systems for biodegradation study of the nanoobjects of different nature and morphology was suggested. Rigid nanospheres based on poly(lactic acid) and self-assembled nanoobjects formed from block-copolymer of glutamic acid and phenylalanine were applied as model nanomaterials. For that, two enzymes, namely, esterase and papain were chosen for preparation of the monolithic IMERs. The properties of immobilized enzymes were compared to those obtained for soluble biocatalysts in the reaction of poly(lactic acid) and poly(glutamic acid) degradation. The monitoring of substrate destruction process was carried out using different HPLC modes (anion-exchange, cation-exchange or precipitation-redissolution based process) also based on application of the same modern stationary phase, namely, macroporous monoliths (CIM disks and lab-made column). Finally, the applicability of monolithic immobilized enzyme reactors for degradation of polyester and polypetide-based particles was demonstrated and compared to the process observed in human blood plasma.

Self-assembled polypeptide nanoparticles for intracellular irinotecan delivery.

In this research poly(l-lysine)-b-poly(l-leucine) (PLys-b-PLeu) polymersomes were developed. It was shown that the size of nanoparticles depended on pH of self-assembly process and varied from 180 to 650nm. The biodegradation of PLys-b-PLeu nanoparticles was evaluated using in vitro polypeptide hydrolysis in two model enzymatic systems, as well as in human blood plasma. The experiments on the visualization of cellular uptake of rhodamine 6g-loaded and fluorescein-labeled nanoparticles were carried out and the possibility of their penetration into the cells was approved. The cytotoxicity of polymersomes obtained was tested using three cell lines, namely, HEK, NIH-3T3 and A549. It was shown that tested nanoparticles did not demonstrate any cytotoxicity in the concentrations up to 2mg/mL. The encapsulation of specific to colorectal cancer anti-tumor drug irinotecan into developed nanocontainers was performed by means of pH gradient method. The dispersion of drug-loaded polymersomes in PBS was stable at 4°C for a long time (at least 1month) without considerable drug leakage. The kinetics of drug release was thoroughly studied using two model enzymatic systems, human blood serum and PBS solution. The approximation of irinotecan release profiles with different mathematical drug release models was carried out and allowed identification of the release mechanism, as well as the morphological peculiarities of developed particles. The dependence of encapsulation efficiency, as well as maximal loading capacity, on initial drug concentration was studied. The maximal drug loading was found as 320±55µg/mg of polymersomes. In vitro anti-tumoral activity of irinotecan-loaded polymersomes on a colon cancer cell line (Caco-2) was measured and compared to that for free drug.