Selective Partitioning of (Biomacro)molecules in the Crowded Environment of Double-Hydrophilic Block Copolymers

Self-Coacervation of Oligo(ethylene glycol) and Oligo(2-ethyl-2-oxazoline)-Based Double Hydrophilic Brush Block Copolymers in Aqueous Solution

Coacervates are a highly relevant class of structures formed via liquid-liquid phase separation and new coacervate-forming polymers are highly sought after. Here, the formation of simple coacervate droplets from a double hydrophilic block copolymer (DHBC) with the combination of poly(oligo ethylene glycol methacrylate) (POEGMA) and poly(oligo 2-ethyl-2-oxazoline methacrylate) (POEtOx) without the use of external triggers or charges is shown. At a high concentration of 25 wt.%, the DHBC forms coacervate droplets with sizes in the low micrometre range. The droplets have relatively high stability over a long period of time with only minor coalescence observed after 4 weeks. At low concentrations, no coacervation is observed. Furthermore, copolymers of the monomers also do not show coacervation clearly indicating that the DHBC architecture is required to form the desired structures. The addition of guest polymers and biomacromolecules at low concentrations shows a specific partitioning behaviour with a preference for the polymer or the aqueous phase. At high guest concentrations, enrichment in the aqueous phase is observed, in line with common water-in-water (w/w) emulsions. These findings constitute a new direction for coacervate systems that are of interest for biotechnology, synthetic cell environment mimics and drug delivery.

Membrane Fusion-Based Drug Delivery Liposomes Transiently Modify the Material Properties of Synthetic and Biological Membranes

Many drug targets are located in intracellular compartments of cells but they often remain inaccessible to standard imaging and therapeutic agents. To aid intracellular delivery, drug carrier nanoparticles have been used to overcome the barrier imposed by the plasma membrane. The carrier must entrap large amounts of cargo, efficiently and quickly deliver the cargo in the cytosol or other intracellular compartments, and must be inert; they should not induce cellular responses or alter the cell state in the course of delivery. This study demonstrates that cationic liposomes with high charge density efficiently fuse with synthetic membranes and the plasma membrane of living cells. Direct fusion efficiently delivers large amounts of cargo to cells and cell-like vesicles within seconds, bypassing slow and often inefficient internalization-based pathways. These effects depend on liposome charge density, concentration, and the helper lipid. However, fusion-mediated cargo delivery results in the incorporation of large amounts of foreign lipids, causing changes to the material properties of these membranes, namely modifications in membrane packing and fluidity, induction of membrane curvature, decrease in surface tension, and the formation of (short-lived) pores. Importantly, these effects are transient and liposome removal allows cells to recover their state prior to liposome interaction.

Investigating and Optimizing Insulin Partitioning with Conjugated Au Nanoparticles in Aqueous Two-Phase Systems Using Response Surface Methodology

This study investigated the impact of bioconjugation on the partitioning of insulin, a clinically valuable protein, in an aqueous two-phase system. Gold nanoparticles of different sizes were synthesized and conjugated with insulin. Analysis of the conjugated insulin showed that the insulin remains fully active. Conjugated gold nanoparticles (AuNPs/insulin) were used in polyethylene glycol (PEG)-dextran aqueous two-phase systems to investigate the effect of pH, PEG and dextran molecular weights, PEG and dextran concentrations, AuNPs/insulin dosage, and nanoparticle size on the partition coefficient. These systems were chosen for their biocompatibility and low toxicity. Response surface methodology with D-optimal design was used to model and optimize these systems and their affected parameters. At the optimum condition of a pH = 8 system containing 21% PEG 4000, 5% dextran 100,000, and 100 IU AuNPs/insulin, the partition coefficient of AuNPs/insulin was found to be 192.96, which is in agreement with the empirical partition coefficient of 189.2. This is significantly higher than the partition coefficient of free insulin in a similar system. This approach could be used to overcome limitations in the feasibility of aqueous two-phase systems for industrial-scale purification of biomolecules and biopharmaceuticals.

Membranous and Membraneless Interfaces-Origins of Artificial Cellular Complexity

Living cell architecture is based on the concept of micro-compartmentation at different hierarchical levels [...].

Modulation of Double Zwitterionic Block Copolymer Aggregates by Zwitterion-Specific Interactions

Transformable double hydrophilic block copolymer assemblies are valid as a biocompatible smart macromolecular system. The molecular mechanisms in the spontaneous assembly of double zwitterionic diblock copolymers composed of a poly(carboxybetaine methacrylate) (PCB2) and a poly(sulfobetaine methacrylate) (PSB4) chains (PCB2-b-PSB4) were investigated by the modulation of the aggregates in response to nondetergent zwitterions. The PCB2-b-PSB4 diblock copolymers with a high degree of polymerization PSB4 block produced aggregates in salt-free water through "zwitterion-specific" interactions. The PCB2-b-PSB4 aggregates were dissociated by the addition of nondetergent sulfobetaine (SB4) and carboxybetaine (CB2) molecules, while the aggregates showed different aggregation modulation processes for SB4 and CB2. Zwitterions with different charged groups from SB4 and CB2, glycine and taurine, hardly disrupted the PCB2-b-PSB4 aggregates. The PCB2-b-PSB4 aggregate modulation efficiency of SBs associated with the intercharge hydrocarbon spacer length (CSL) rather than the symmetry with the SB in the PSB chain. These zwitterion-specific modulation behaviors were rationalized based on the nature of zwitterions including partial charge density, dipole moment, and hydrophobic interactions depending on the charged groups and CSL.

Polysaccharide nanoparticles: from fabrication to applications

The present review highlights the developments in polysaccharide nanoparticles with a particular focus on applications in biomedicine, cosmetics and food.