Effect of end-groups on the motions of free nitroxyl radicals in poly(ethylene glycol)

Influence of water on the mobility of small molecules dispersed in a polymeric system

The rotational mobility of paramagnetic solutes dispersed in partially hydrated macromolecules (proteins, polysaccharides, synthetic polymers) was measured using Electron Spin Resonance. A critical minimum amount of water was observed to be necessary for these molecules to reach a level of mobility of the same order as in dilute solutions. This amount of water depended on the size of the diffusing solute and on the microporosity of the macromolecule. Above this critical moisture range, a progressive increase of the proportion of mobile solute occurred over a hydration range determined by the size of the diffusing solute. At the same time, the rotational diffusivity of the mobile solute increased linearly with water content. The mobilization pattern of spin-labelled side chains of caseinates was observed to be similar to that of the solute. Results are discussed with reference to free volume theory.

Microencapsulation of mammalian cells in a hydroxyethyl methacrylate-methyl methacrylate copolymer: preliminary development

Erythrocytes were microencapsulated in a thermoplastic copolymer of poly-2-hydroxyethyl methacrylate (79% mole%) - co-methyl methacrylate (21 mole %) with little apparent initial cell lysis. Droplets of cell suspension and polymer solution were blown from the tip of a coaxial needle assembly into a receiving bath of hexadecane over phosphate buffered saline (PBS) containing a low concentration of nonionic surfactant. Capsules were trapped at the hexadecane/PBS interface where they were cured by the removal of polymer solvent to precipitate a polymer coating around the cell suspension. Important principles which were considered in the development of the successful process, included the need to prevent intermixing of polymer solution and cell suspension, to fully surround the cells with polymer solution prior to precipitation, and to prevent direct mixing of the curing bath with the polymer solution.

Is purified poly(ethylene glycol) able to induce cell fusion?

Preparations of poly(ethylene glycol) 6000 (PEG) from five different commercial sources have been purified, and their ability to fuse hen erythrocytes has been investigated. Quantitative assessments of cell fusion showed that before purification one of the preparations (PEG Wako), was able to induce limited fusion (5-6%) of erythrocytes with conditions (1 min incubation with 50% w/w PEG) under which the other four unpurified preparations of PEG were inactive. On purification, PEG (Wako) became inactive. By contrast, when erythrocytes were incubated with 45% w/w PEG for 15 min, extensive fusion (23-27%) occurred with all five unpurified preparations of PEG. Under these conditions, the fusogenic properties of four of the preparations of PEG were unaffected by purification: fusion induced by PEG (Wako) was, however, decreased on purification from 27% to 19%. It appears that polymeric poly(ethylene glycol) is itself able to fuse cells, but that some commercial preparations, e.g. PEG (Wako), have enhanced fusogenic properties resulting from the presence of contaminating substances. No relationship between the absorbance at 290 nm of PEG and its fusogenic properties was found in this study. The addition of small quantities of fusogenic lipid-soluble compounds to PEG was, however, observed to enhance cell fusion by up to 50%.