Construction of Membraneless and Multicompartmentalized Coacervate Protocells Controlling a Cell Metabolism-like Cascade Reaction.

In recent years, there has been growing attention to designing synthetic protocells, capable of mimicking micrometric and multicompartmental structures and highly complex physicochemical and biological processes with spatiotemporal control. Controlling metabolism-like cascade reactions in coacervate protocells is still challenging since signal transduction has to be involved in sequential and parallelized actions mediated by a pH change. Herein, we report the hierarchical construction of membraneless and multicompartmentalized protocells composed of (i) a cytosol-like scaffold based on complex coacervate droplets stable under flow conditions, (ii) enzyme-active artificial organelles and a substrate nanoreservoir capable of triggering a cascade reaction between them in response to a pH increase, and (iii) a signal transduction component based on the urease enzyme capable of the conversion of an exogenous biological fuel (urea) into an endogenous signal (ammonia and pH increase). Overall, this strategy allows a synergistic communication between their components within the membraneless and multicompartment protocells and, thus, metabolism-like enzymatic cascade reactions. This signal communication is transmitted through a scaffold protocell from an "inactive state" (nonfluorescent protocell) to an "active state" (fluorescent protocell capable of consuming stored metabolites).

Phosphorylated Polyesters Inspired by Phospholipids: Synthesis, Characterization, and Potential Applications.

We report the synthesis of phosphorylated polyesters by the phosphorylation of hydroxylated polyesters synthesized by the lipase-catalyzed polycondensation of glycerol and aliphatic dicarboxylic acids and their characterization. The use of phosphoryl chloride as a phosphorylating agent and triethylamine as a catalyst in mild reaction conditions resulted in polyesters with repetitive units structurally similar to phospholipids, molar mass of around 14-38 kDa, and a degree of phosphorylation of 36 ± 11 mol %. These polyesters are composed mainly of 10 different repetitive units as determined by 1D and 2D NMR. Their properties change from more hydrophilic and amorphous for phosphorylated poly(glycerol adipate) to more hydrophobic and semicrystalline for phosphorylated poly(glycerol dodecanedioate). Preliminary investigations have shown the potential of these polyesters to self-assemble in aqueous media forming nanoparticles, which can be loaded with hydrophobic molecules and released into an organic phase, acting as a phase transfer agent, and used as a pH-responsive emulsifier.

Enzymatic Synthesis of Poly(glycerol sebacate): Kinetics, Chain Growth, and Branching Behavior.

Immobilized Candida antarctica lipase B (CALB)-catalyzed polycondensation of glycerol and sebacic acid at mild reaction conditions resulted in branched poly(glycerol sebacate) (PGS). To understand how PGS chains grow and branch, the kinetics of the CALB-catalyzed polycondensation were studied. The influence of the reaction temperature, solvent, CALB amount, and sebacic acid/glycerol feed ratio on the poly(glycerol sebacate) (PGS) molecular weight, degree of branching, and glyceridic repetitive unit distribution was also investigated. PGS architecture changes from linear to branched with the progression of the reaction, and the branching results from the simultaneous CALB-catalyzed esterification and acyl migration. For reactions performed in acetone at the temperature range from 30 to 50 °C, the apparent rate constant increases from 0.7 to 1.5 h-1, and the apparent energy of activation of 32 kJ mol-1 was estimated. The higher mass average molecular weight (16 kDa) and degree of branching (41%) were achieved using the equimolar sebacic acid/glycerol feed ratio in acetone at 40 °C with a CALB amount of 13.6 wt % and in the presence of the molecular sieves.

Mechanical behaviour and biocompatibility of poly(1-vinyl-2-pyrrolidinone)-gelatin IPN hydrogels.

IPN hydrogels based on poly(1-vinyl-2-pyrrolidinone) and gelatin were obtained by casting of aqueous solution using potassium persulphate and glutaraldehyde as respective crosslinking agents. Studies of swelling and mechanical behaviour showed that the samples of different composition can incorporate high content of water and still exhibit high compression strength. The composition has influence at the global crosslinking density what affects the mechanical performance. In vitro biocompatibility and hemocompatibility were also investigated. The materials do not interfere on the cellular functions and neither induce platelet adhesion. From this preliminary evaluation, it is possible to conclude that these hydrogels have potential for applications in the biomedical field.