Evaluation of Nanoporous and Macroporous polymer Hydro-gels as a potential Barrier for Guided Bone regeneration (GBr).

LEZCANO D; YSLAS EI; MOLINA MA; RIVAROLA CR; BARBERO C; RIVAROLA V

Cannes

Congreso; International Osteology Symposium.; 2011

International Osteology Symposium.

312- Evaluation Of Nanoporous and Macroporous polymer Hydrogels as a potential Barrier For Guided Bone regeneration (GBr) Objectives: 1. Synthesis of (poly(n-isopropylacrylamide-co-(2-acrylamido-2-methylpropane sulfonic acid)) (PNIPAm-co-2%AMPS). 2. Characterization of PNIPAm-co-2%AMPS using a scanning electron microscopy (SEM). 3. Determination of permeability properties of PNIPAm-co-2%AMPS nano and macroporous hydrogels. 4. Evaluation of biocompatibility of PNIPAm-co-2%AMPS nano and macroporous hydrogels using LM2 cell lines. 5. Analysis of cell adhesion on membrane surfaces of PNIPAm-co-2%AMPS nano and macroporous hydrogels. Methods: In order to prepare the nanoporous polymer, the hydrogel was dried by heating the PNIPAm-co-2%AMPS and a polymer network without voids in its structure was obtained. Further swelling of this material in water increased the network chain space in the polymer matrix by ~36 nm. To obtain the macropores, the polymer was prepared below the bulk freezing temperature of the reaction system (-18o C). During this process ice crystals acted as a template for the formation of the macro pores. To characterize the structure of these materials, SEM studies were carried out at low vacuum and low feld using a LEO 1450VP SEM. The permeability of these hydrogels was determined by passive diffusion of toluidine blue and Höechst dye. Biocompatibility of these materials was checked by following morphology and adhesion of LM2 cells cultured over the hydrogels. These experiments were performed using fuorescent microscopy. Toluidine blue and Höechst dyes were used as probes for labelling the cells. Results: SEM studies show clear macroporous structure. The distribution of macropore size is very narrow with a mean value of about ~64 nm. The shape and size of the macropores change after the gel is subjected to drying and rehydration. During drying the pores collapse and are then rehydrated into a different shape. After the initial rearrangement, the pore morphology remains stable during drying/wetting cycles. To calculate the size of the pores in nanoporous hydrogels we used the theory of equilibrium swelling obtaining an average of 36 nm. The adhesion of cells to hydrogels was studied observing cell interactions with these substrates. Microscopic examination revealed that the cells adhered to and grew onto the surface of material as well as inside its pores, showing regular cell morphology. Fluorescence microscopy analysis showed that the cells adhered and normally grew onto the surface of material as well as inside its pores. This result shows that the hydrogels were non-cytotoxic. Conclusions: We have evaluated both nano and macroporous hydrogels as a membrane barrier for GBR. We showed that both micro and macroporosity allow exchange of water and small molecules. In addition the material is biocompatible for lm2 cells. These studies demonstrated that the PNIPAMco-2%AMPS nano and macro porous hydrogels have a high potential as a barrier membrane for GBR. Future experiments are necessary to evaluate the behavior of hydrogels in vivo.