Tuning Size and Morphology of mPEG-b-p(HPMA-Bz) Copolymer Self-Assemblies Using Microfluidics.

The careful design of nanoparticles, in terms of size and morphology, is of great importance to developing effective drug delivery systems. The ability to precisely tailor nanoparticles in size and morphology during polymer self-assembly was therefore investigated. Four poly(ethylene glycol)-b-poly(N-2-benzoyloxypropyl methacrylamide) mPEG-b-p(HPMA-Bz) block copolymers with a fixed hydrophilic block of mPEG 5 kDa and a varying molecular weight of the hydrophobic p(HPMA-Bz) block (A: 17.1, B: 10.0, C: 5.2 and D: 2.7 kDa) were self-assembled into nanoparticles by nanoprecipitation under well-defined flow conditions, using microfluidics, at different concentrations. The nanoparticles from polymer A, increased in size from 55 to 90 nm using lower polymer concentrations and slower flow rates and even polymer vesicles were formed along with micelles. Similarly, nanoparticles from polymer D increased in size from 35 to 70 nm at slower flow rates and also formed vesicles along with micelles, regardless of the used concentration. Differently, polymers B and C mainly self-assembled into micelles at the different applied flow rates with negligible size difference. In conclusion, this study demonstrates that the self-assembly of mPEG-b-p(HPMA-Bz) block copolymers can be easily tailored in size and morphology using microfluidics and is therefore an attractive option for further scaled-up production activities.

Cationic synthetic long peptides-loaded nanogels: An efficient therapeutic vaccine formulation for induction of T-cell responses.

Recent studies have shown a high potency of protein-based vaccines for cell-mediated cancer immunotherapy. However, due to their poor cellular uptake, efficient immune responses with soluble protein antigens are often not observed. As a result of superior cellular uptake, nanogels loaded with antigenic peptides were investigated in this study as carrier systems for cancer immunotherapy. Different synthetic long peptides (SLPs) containing the CTL and CD4+ T-helper (Help) epitopes were synthesized and covalently conjugated via disulfide bonds to the polymeric network of cationic dextran nanogels. Cationic nanogels with a size of 210 nm, positive zeta potential (+24 mV) and high peptide loading content (15%) showed triggered release of the loaded peptides under reducing conditions. An in vitro study demonstrated the capability of cationic nanogels to maturate dendritic cells (DCs). Importantly, covalently SLP-loaded nanogels adjuvanted with poly(I:C) showed superior CD8+ T cell responses compared to soluble peptides and nanogel formulations with physically loaded peptides both in vitro and in vivo. In conclusion, covalently SLPs-loaded cationic nanogels are a promising system to provoke immune responses for therapeutic cancer vaccination.

In vitro hydrolytic degradation of hydroxyl-functionalized poly(alpha-hydroxy acid)s.

The in vitro hydrolytic degradation of hydroxyl-functionalized poly(alpha-hydroxy acid)s was investigated. Benzyl-ether-protected hydroxyl-functionalized dilactones (S)-3-benzyloxymethyl-(S)-6-methyl-1,4-dioxane-2,5-dione (1a) and (S)-3-benzyloxymethyl-1,4-dioxane-2,5-dione (1b) were copolymerized in a melt with various amounts of L-lactide using benzyl alcohol and SnOct2 as the initiator and catalyst, respectively. The benzyl groups were removed by hydrogenation to yield polyesters with hydroxyl functional groups, poly(lactic acid-co-hydroxymethyl glycolic acid) and poly(lactic acid-co-glycolic acid-co-hydroxymethyl glycolic acid) (2a and 2b). Degradation of the hydroxyl-functionalized polyesters and poly(lactic-co-glycolic acid) (50/50) was studied by incubation of pellets of these polymers in phosphate buffer (174 mM, pH 7.4) at 37 degrees C. Polymer degradation was monitored by mass-loss measurements and by gel permeation chromatography, differential scanning calorimetry, and 1H NMR analysis. The degradation times ranging from less than 1 day (for the homopolymer of 2a) to 2 months (copolymer of 25% 2a and 75% lactide) were found. The degradation rates increased with increasing hydroxyl density of the polymers, which was associated with a switch from bulk to surface erosion. NMR and thermal analysis showed that the moieties with the hydroxyl groups were preferentially removed from the degrading polymer. In conclusion, this study shows that the degradation rate of polyesters containing 2a and 2b can be tailored from a few days to 2 months, making them very suitable for biomedical and pharmaceutical applications.

Synthesis of peptide-based polymers by microwave-assisted cycloaddition backbone polymerization.

The optimized reaction conditions for the Cu(I)-catalyzed N-->C polymerization of azido-phenylalanyl-alanyl-propargyl amide to yield either high molecular weight linear polymers or medium-sized cyclic polymers is described. These reaction conditions will be applied to tailor the synthesis, properties, and structure of biologically relevant peptide-based biopolymers.