The use of polymers for coating of cells

Bare cells or tissues are sometimes exposed to external hazardous conditions, physical (thermal changes), chemical or biological (such as enzymes, bacteria and viruses). Liquids, semi-liquids (e.g. gels) or solid films are often used to surround individual cells or tissues in order to protect them and to achieve greater stability in laboratory and industrial uses. On the one hand there is a need for isolation and creating a barrier between the cell and its surroundings, and on the other hand this should not affect the metabolism and viability of the cell used. Polymers are major substances for cell encapsulation and entrapment. These preparations are often used for the manufacture of drugs and other cell metabolites. There are only a few publications describing single-cell coating. We can consider a definition of coating as a process of surrounding an object with a thin film, having a thickness of only a small fraction of the object's dimensions. Taking this definition into account, in fact, most coating experiments actually deal with entrapment or immobilization rather than coating. The latest research shows for the first time the ability to coat a single cell by producing a thin gel layer around it. Xenopus laevis eggs and embryos were used as a model system for coating with thin films composed of low-methoxy pectin (LMP), alginate, and i- and k-carrageenans. These gums have different compositions and structures and accordingly created different coatings around the cells. The first goal was to achieve a thin film (similar to50 mum) around an individual non-fertilized egg (one cell). Next, the influence Of coating an early-stage toad embryo was tested. All coated embryos appeared to develop normally, similar to non-coated embryos. The survival percentages after hatching of coated embryos were, significantly higher than of the non-coated control. In addition, the coating served as a barrier to microbial contamination and thus improved survival prospects. The coatings delayed hatching by 18 to 24 hr. At hatch, the embryos were at a more developed stage than their non-coated counterparts. Thus, coating cells by polymeric thin film appears to be a suitable tool for laboratories interested in performing longer-term experiments with cells or embryos. Copyright (C) 2003 John Wiley Sons, Ltd.