A novel immobilized-enzyme system utilizing microcapsules

Some factors affecting the size of nylon 6-10 microcapsules prepared by interfacial polymerization in a high-voltage electric field

The effect of process variables such as nozzle size, flow-rate of dispersed phase, inter-electrode distance, and presence of an acid acceptor and a thickening agent in the dispersed phase, on the production and size distribution of nylon 6-10 microcapsules prepared by interfacial polymerization in a high-voltage electric field was studied. Factors which increased the intensity of the electrostatic forces acting upon the droplets formed, such as increasing nozzle diameter at constant aqueous phase flow-rate and decreasing inter-electrode distance, were found to decrease the capsule size while those which enhanced the availability of the aqueous phase monomer for the polymerization reaction, such as the addition of an acid acceptor and a thickening agent, resulted in an increase in the average size of the capsules obtained. Free flowing capsules and a reduction in the rate of diacid chloride hydrolysis during the process were also obtained with increasing concentration of the thickening agent in the aqueous phase.

Preparation of heat responding artificial cells

Enzyme-loaded microcapsules were prepared and treated with dimyristoylphosphatidylcholine molecules so as to control the permeation of substrates through the microcapsule membranes. The activities of enclosed enzymes increased with increase in ambient temperature, but gave an abrupt change at around the phase transition temperature of the lipid. The experimental results indicate the possibility of making artificial cells which respond to the temperature change of the surrounding medium.

Freezing behaviour of microencapsulated water

The freezing behaviour of water in polyurea microcapsules was studied through DSC (differential scanning calorimetry) and ESR (electron spin resonance) measurements under a non-equilibrium condition to show that supercooling of water becomes more noticeable with decreasing droplet size of the liquid. Thermodynamics of small systems was found applicable to analyse the experimental findings, even though the process of water freezing in the microcapsules was not of an equilibrium nature.

A study on the thermostability of microencapsulated glucose oxidase

Glucose oxidase was microencapsulated within polyurea membranes by the interfacial polymerization method and the stability to heat of the encapsulated enzyme was examined. Thermostability of microencapsulated glucose oxidase was prominent and increased with increase in the amount of glucose oxidase entrapped. This stability, however, could not be ascribed to the peculiar properties of microcapsules but was suggested to be caused by the incorporation of glucose oxidase molecules in the membranes through chemical bonding. This stability revealed that the enzyme molecules in the microcapsules could not always exist in the dissolved form but a fairly large portion of the molecules participated in the polymerization reaction and changed their enzymatic properties.