Department of Hydrogels for Medical and Technical Practice

Characterization of Dept. Hydrogels for medical and technical practice

The development of synthetic hydrogels for biomedical use as well as contact and intraocular lenses is the typical topic for department. The research has been advanced continuously from the period of the eighties when our department was closely associated with the Academician Otto Wichterle DSc, one of the leading pioneers of polymer science.

Figure 1: Academician Otto Wichterle DSc in front of a machine for contact lenses producing		Fig 2: All operations in preparation of medical grade articles are carried out in a clean room of type A

New polymeric materials are tested using physical and chemical methods. The material properties (swelling, mechanical, transport and optical properties) are studied including their biocompatibility and interaction with living tissue.

In the last year we developed polymer materials facilitating wound healing, which are capable of removing reactive oxygen and nitrogen species. The wound-cover material is characteristic in that it consists of a polymer carrier based on slightly crosslinked hydrophilic polymers or copolymers and physiological bioactive substances with radical scavenger properties, selected from the group of vitamins A, carotenoids, vitamins E, ubiquinones, flavonoids, nicotin­amide, uric acid, bilirubin, lipoic acid, glutathione, and melatonin. The material is successfully used in veterinary medicine.

New hydrophilic polymer supports for cultivation and subsequent transplantation of keratinocytes designed for treatment of burns and large skin defects have also been prepared. We continued the research by testing low-hydrated materials containing ether groupings. We prepared copolymers of glycerol monomethacrylate and 2-ethoxy­ethyl methacrylate cross­linked with glycerol dimethacrylate and compared them with copolymers of glycerol mono- and dimeth­acrylate. Following our present and previous results, it is evident that one of the main factors determining keratinocyte adhesion is the equilibrium swelling of hydrogel. Low-hydrated hydrogels show enhanced sorption of proteins important for cell adhesion (e.g. fibronectin and its active adhesive sequences). Thus, we started preparation of polymer carriers based on 2-ethoxyethyl methacrylate (possibly with a low admixture of 2-hydroxyethyl meth­acrylate) crosslinked with hexane-1,6-diyl dimeth­acrylate and containing modified adhesive amino acid sequences derived from fibronectin (e.g. RGD with synergic sequence PHSRN). We prepared 6-meth­acryl­amidohexanoyl-PHSRN­amide and 6-methacryl­amido­hexanoyl-RGD-amide by a method of solid-phase synthesis of peptides. Both the prepared amides were copolymerized with 2-ethoxy­ethyl meth­acrylate. Now we are working on optimization of the length and type of flexible spacer between methacrylate chain and adhesive sequences.

In the framework of the research on implants for the central nervous system, we continued in the research of macroporous hydrogels based on copolymers of 2-hydroxyethyl meth­acrylate, methacrylic acid and [2-(meth­acryloyloxy)ethyl]tri­methyl­amonium chloride and their polyelectrolyte complexes. Previous results have demonstrated the possibility of obtaining controlled pore size, pore communication, and suitable biological response. Our hydrogels show predominantly communicating pores and quite a narrow pore size distribution as follows from confocal and electron microscopy.

From the viewpoint of mechanical properties, the 10 mol% concentration of ionic monomers is an optimum (properties of the resulting polymer are similar to those of the nervous tissue). As most polymer - living tissue interactions are localized in the protein layer at the interface, we prepared a layer of selected proteins on surfaces of the materials. The described macroporous hydrogels were used for immobilization of model proteins: albumin (low pI, 4.9) and avidin (high pI, 10.5). The protein adsorption capacity was measured and kinetic studies were carried out. The protein - polymer complex is stable, desorption of proteins is minimal.

Fig 3: AquaSEM picture of a macroporous hydrogel prepared by a copolymerization of 2-hydroxyethyl methacrylate and sodium methacrylate (11.3 mol %) in the presence of NaCl (particle size 50 - 90 um). After polymerization NaCl was washed out by water. This material is tested in vivo and vitro as potential implant in the central nervous system.		Fig 4:   AFM picture of 1% poly(HEMA) deposited onto a fused silica as a polymer layer for capillary electrophoretic separations of biologically active compounds

In the framework of the research on new hydrogel materials for contact lenses, we prepared copolymers of diethylene glycol methacrylate with new types of perfluorinated vinyl monomers. They are transparent gels with promising properties. The mentioned structures enhance oxygen permeability of resulting hydrophilic gels.

We also participate in the development of novel separation techniques, e.g. in syntheses of imprinted polymers for high-performance liquid chromatography or capillary electro­chromatography and in the study of permanent hydrogel coatings of fused-silica columns for capillary electrophoresis. 

The biomedical properties of prepared polymers are evaluated by long-standing and successful collaboration with the teams of co-workers at the Institute of Anatomy, the First Faculty of Medicine at Charles University, Prague, and Burn center, the Third Faculty of Medicine at Charles University, Prague as well as at the Department of Eye Histochemistry, the Institute of Experimental Medicine, Academy of Sciences, Prague.

In cooperation with the Charles University of Prague, the Institute of Chemical Technology of Prague our department educates several PhD. and diploma students and generates the opportunity to evolve both pure and applied research. 

Further our department makes use of long tradition in coactions with the Czech Contact Lens Society and we profess at the Second Faculty of Medicine at Charles University, Prague as external lecturers.

Send your comments to:
jiri@imc.cas.cz

Last modified: 04.06.2004