ethyl-cellulose and ethyl-acetate

Monodisperse ethyl cellulose (EC) hollow microcapsules are successfully prepared by using a simple and novel method which combines microfluidic double emulsification and solvent diffusion. To dissolve EC, we use a non-toxic solvent ethyl acetate (EA), instead of methylene chloride which is commonly used but carcinogenic. By introducing chitosan (CS) into outer fluid, we can increase the viscosity of outer fluid and obtain smaller microcapsules which are desired. On the other hand, introducing CS only into outer fluid could lead to osmotic pressure gradient between the inner and outer fluids which could cause the undesired collapse of microcapsules. To avoid the collapse phenomena, we try adding iso-osmotic NaCl into inner aqueous fluid but failed in achieving osmotic pressure balance possibly because the small Na(+) and Cl(-) ions could penetrate the EC matrix during solidification. However, success is achieved when we introduce CS into both inner and outer fluids because CS polymer is too big to permeate through the EC matrix and thus could maintain iso-osmotic state. The microcapsules prepared under iso-osmotic state show perfect spherical shape and no collapse. The method developed in this work provides a novel and versatile route for fabricating monodisperse biocompatible microcapsules composed of water insoluble polymers.

Topics: Acetates; Capsules; Cellulose; Chitosan; Equipment Design; Microfluidics; Particle Size; Solubility; Solvents; Viscosity; Water

We have developed a new coating material for cerebral aneurysms consisting of cellulose. The possible usefulness of this ethyl cellulose-ethyl acetate solution ("Liquid cellulose") as a coating material was evaluated as follows: 1) The liquid cellulose (ethyl cellulose concentration, 10%; degree of polymerization, 100) and Biobond had pHs of 7.35 and 3.16, and viscosities of 1,385 and 626 cp, respectively. The properties of the coat (N = 30, M +/- SD) of the liquid cellulose and Biobond at a cast coat thickness of 254 microns were as follows: coat thickness after drying (microns), 17.8 +/- 2.8 and 109.8 +/- 44.2; coat formation time (sec), 62 and 1,800; strength of the coat (gm), 432.3 +/- 51.4 and 8.0 +/- 5.6; strength index (kg/cm2), 572.8 +/- 84.7 and 2.4 +/- 1.8; and elongation index (%), 14.8 +/- 3.5 and 705 +/- 188.8, respectively. The coat using liquid cellulose was more physiological and far stronger. It was also more readily manipulated during the operation than Biobond. 2) The liquid cellulose showed excellent adhesiveness when applied to the vascular wall. Sequential histological observations for 12 months showed that the liquid cellulose remained stable without histotoxicity or cracks in the coat. These results indicate the potential usefulness of this agent for reinforcing the vascular wall.

Topics: Acetates; Animals; Biomechanical Phenomena; Carotid Artery, Common; Cellulose; Cyanates; Cyanoacrylates; Dogs; Foreign-Body Reaction; Intracranial Aneurysm; Membranes, Artificial; Microscopy, Electron, Scanning; Solvents; Tissue Adhesives; Viscosity