Polymer-drug conjugates (polymer therapeutics) are finding increasing use as novel anticancer agents. Here a series of poly(ethylene glycol) PEG-doxorubicin (Dox) conjugates were synthesized using polymers of linear or branched architecture (molecular weight 5000-20000 g/mol) and with different peptidyl linkers (GFLG, GLFG, GLG, GGRR, and RGLG). The resultant conjugates had a drug loading of 2.7-8.0 wt % Dox and contained <2.0% free drug (% total drug). All conjugates containing a GFLG linker showed approximately 30% release of Dox at 5 h irrespective of PEG molecular weight or architecture. The GLFG linker was degraded more quickly (approximately 57% Dox release at 5 h), and the other linkers more slowly (<16% release at 5 h), by lysosomal enzymes in vitro. In vitro there was no clear relationship between cytotoxicity toward B16F10 cells and the observed Dox release rate. All PEG conjugates were more than 10-fold less toxic (IC50 values > 2 microg/mL) than free Dox (IC50 value = 0.24 microg/mL). Biodistribution in mice bearing sc B16F10 tumors was assessed after administration of PEGs (5000, 10000, or 20000 g/mol) radioiodinated using the Bolton and Hunter reagent or PEG-Dox conjugates by HPLC. The 125I-labeled PEGs showed a clear relationship between Mw and blood clearance and tumor accumulation. The highest Mw PEG had the longest plasma residence time and consequently the greatest tumor targeting. The PEG-Dox conjugates showed a markedly prolonged plasma clearance and greater tumor targeting compared to free Dox, but there was no clear molecular weight-dependence on biodistribution. This was consistent with the observation that the PEG-Dox conjugates formed micelles in aqueous solution comprising 2-20 PEG-Dox molecules depending on polymer Mw and architecture. Although PEG-Dox showed greater tumor targeting than free Dox, PEG conjugation led to significantly lower anthracycline levels in heart. Preliminary experiments to assess antitumor activity against sc B16F10 in vivo showed the PEG5000linear (L)-GFLG-Dox and PEG10000branched (B)-GLFG-Dox (both 5 mg/kg Dox-equiv) to be the most active with T/C values of 146 and 143%, respectively. Free Dox did not show significant activity in this model (T/C = 121%). Dose escalation of PEG5000(L)-GFLG-Dox to 10 mg/kg Dox-equiv prolonged further animal survival (T/C = 161%). Using the Dox-sensitive model ip L1210 (where Dox displayed a T/C = 150% after single ip dose), the PEG5000(L)-GFLG-Dox displayed a maximum T/C of 141% (10 mg/kg Dox-equiv) using a once a day (x3) schedule. Further studies are warranted with PEG5000(L)-GFLG-Dox to determine its spectrum of antitumor activity and also the optimum dosing schedule before clinical testing.

Five poly(amido-amine)s (PAAs) carrying two ter-amino groups and one carboxyl group per repeating unit were prepared by hydrogen-transfer polyaddition of 2-methylpiperazine (ISA 23), 1,2bis(N-methylamino)ethane (DMEDA-BAC), 1,2-bis(N-ethylamino)ethane (DEEDA-BAC, 1,3-bis(N-methylamino)propane (DMEPDA-BAC), or 1,6-bis(N-methylamino)hexane (DMEXA-BAC), in each case to 2,2-bis(acrylamido)acetic acid (BAC). The resultant PAAs had an M n in the range 7 985-24 980 g/mole and an Mw in the range 11 420-42 710 g/mole. Considerable differences were observed in the basicity of the amino groups present (log K°1 ) 7.5-9.5; log K°2 ) 3.2-8.4), whereas the log K°3 value (2-3) of the carboxyl groups was consistent with that of a fairly strong acid. DEEDA-BAC, DMEDA-BAC, and ISA 23 were nontoxic (IC50 > 5 mg/mL). Those PAAs with the highest log K°2 values were more cytotoxic (IC50 ) 3.55 mg/mL for DMEPDA-BAC, and IC50 ) 0.23 m/mL for DMEXA-BAC). All the PAAs displayed pH-dependent haemolysis (most lytic at pH 5.5), consistent with their proposed use as endosomolytic polymers.

Many human diseases are associated with harmful action of reactive oxygen species (ROS). These species are involved in the degradation of essential tissue or related components. One of such components is synovial fluid that contains a high-molecular-weight polymer--hyaluronan (HA). Uninhibited and/or inhibited hyaluronan degradation by the action of various ROS has been studied in many in vitro models. In these studies, the change of the molecular weight of HA or a related parameter, such as HA solution viscosity, has been used as a marker of inflicted damage. The aim of the presented review is to briefly summarize the available data. Their correct interpretation could contribute to the implementation of modern methods of evaluation of the antioxidative capacity of natural and synthetic substances and prospective drugs--potential inflammatory disease modifying agents. Another focus of this review is to evaluate briefly the impact of different available analytical techniques currently used to investigate the structure of native high-molecular-weight hyaluronan and/or of its fragments.

Nine hyaluronan (HA) samples were fractionated by size-exclusion chromatography, and molar mass (M), radius of gyration (Rg), and intrinsic viscosity ([eta]) were measured in 0.15 M NaCl at 37 degrees C by on-line multiangle light scattering and viscometer detectors. Using such method, we investigated the Rg and [eta] molar mass dependence for HA over a very wide range of molar masses: M ranging from 4 x 10(4) to 5.5 x 10(6) g/mol. The Rg and the [eta] molar mass dependence found for HA showed a meaningful difference. The Rg = f(M) power law was substantially linear in the whole range of molar masses explored with a constant slope of 0.6. In contrast, the [eta] = f(M) power law (Mark-Houwink-Sakurada plot) showed a marked curve shape, and a linear regression over the whole range of molar masses does not make sense. Also the persistence length (stiffness) for HA was estimated. The persistence length derived by using both the Odijk's model (7.5 nm from Rg vs M data) and the Bohdanecky's plot (6.8 nm from [eta] vs M data) were quite similar. These persistence length values are congruent with a semistiff conformation of HA macromolecules.