Double hydrophilic block copolymers self-assemblies in biomedical applications.

Double-hydrophilic block copolymers (DHBCs), consisting of at least two different water-soluble blocks, are an alternative to the classical amphiphilic block copolymers and have gained increasing attention in the field of biomedical applications. Although the chemical nature of the two blocks can be diverse, most classical DHBCs consist of a bioeliminable non-ionic block to promote solubilization in water, like poly(ethylene glycol), and a second block that is more generally a pH-responsive block capable of interacting with another ionic polymer or substrate. This second block is generally non-degradable and the presence of side chain functional groups raises the question of its fate and toxicity, which is a limitation in the frame of biomedical applications. In this review, following a first part dedicated to recent examples of non-degradable DHBCs, we focus on the DHBCs that combine a biocompatible and bioeliminable non-ionic block with a degradable functional block including polysaccharides, polypeptides, polyesters and other miscellaneous polymers. Their use to design efficient drug delivery systems for various biomedical applications through stimuli-dependent self-assembly is discussed along with the current challenges and future perspectives for this class of copolymers.

PCL-PEG graft copolymers with tunable amphiphilicity as efficient drug delivery systems.

The development of flexible drug delivery systems that can be tuned as a function of the drug to be delivered and of the target disease is crucial in modern medicine. For this aim, novel amphiphilic poly(ε-caprolactone)-g-poly(ethylene glycol) (PCL-g-PEG) copolymers with well-controlled design were synthesized by thiol-yne photochemistry. The grafting density and the copolymer amphiphilicity were easily controlled via the reaction parameters: concentration, reaction time, PEG length and the molar ratio between PCL and PEG or the photoinitiator in the reaction mixture. The self-assembling behavior of the copolymers was studied and a correlation between the composition of PCL-g-PEG and the nanoaggregate diameter sizes (28 to 73 nm) and critical aggregation concentrations (1.1 to 4.3 mg L-1) was found. The influence of copolymer amphiphilicity on the drug loading was evaluated with various drugs including anticancer drugs (paclitaxel, ABT-199), drugs to overcome multidrug resistance in cancer cells (curcumin, elacridar), an anti-inflammatory drug (dexamethasone) and an antibacterial drug (clofazimine). Finally, the influence of amphiphilicity on curcumin release and toxicity towards MCF-7 cancer cell lines was studied. The impact of the grafting density, PEG length and the overall EG/CL ratio is discussed in detail. Curcumin loaded PCL-g-PEG with lower EG/CL ratios and shorter PEG chains showed higher toxicity compared to their more hydrophilic counterparts.

[The use of a hydrolysis residue from lysine production in a straw concentrate mixture for fattening lambs]. / Die Verwendung eines Hydrolyserückstandes aus der Lysinherstellung im Strohkonzentratgemisch für Mastlämmer.

The validity of residues from hydrolysis of soya bean meal for production of lysine was tested in a growth experiment with 2 groups of 25 cross breeding lambs as well as in a N-balance trial with 5 lambs. The animals in the growth experiment started with an average body weight of 25 kg. An industrially produced concentrate for lamb fattening was given to the animals of the control group. To the second group a straw-concentrate mixture was given, containing 30% straw, 52% barley, 5% soya bean meal, 5% dried beet pulp and 5% of hydrolysis residue. The mixture included 10.71 MJ ME resp. 5.51 MJ net-energy fat (cattle) and 166 g digestible crude protein per kg dry matter. The lambs of group 2 showed an 8% lower intake of DM, connected with a 26% intake of energy and 32% lower intake of DCP in comparison to the control group. The average daily body weight gain was 374 g for the control group and 241 g for group 2 respectively, the difference being statistically significant. The feed/gain ratio was in group 2 = 14% higher for energy and 6% higher for DCP than in the control group. The N-balance trial resulted in a N-retention of 25 percent of the N-intake. The results approved the possible use of 5% of the hydrolysis residue product for 2% crude protein in straw-concentrate mixtures for ruminants.