Analysis of tissue response around injectable hydrogels in the subcutaneous tissue of Wistar rats

Abstract

Event Abstract Back to Event Analysis of tissue response around injectable hydrogels in the subcutaneous tissue of Wistar rats Khatharine S. Aoki1*, Yuri Gurfinkel1*, Eliana A. Duek2*, Daniel V. Mistura3* and Newton Oliveira4* 1 Faculty of Medical Sciences and Health, Pontificial Catholic University of São Paulo, Medical student, Brazil 2 Faculty of Medical Sciences and Health, Pontificial Catholic University of São Paulo, Physiology Department, Brazil 3 Faculty of Medical Sciences and Health, Pontificial Catholic University of São Paulo, Laboratory of Biomaterials, Brazil 4 Faculty of Medical Sciences and Health, Pontificial Catholic University of São Paulo, Morphology and Pathology Department, Brazil Tissue engineering represents an alternative for the recovery of organs and tissues[1]. In this way, the use of polymers as biomaterials has increased, being the hydrogels an option. These polymers have a hydrophilic characteristic, so they swell when in contact with water[2]. Furthermore, they can be presented in solid or liquid form and, in the liquid presentation, the hydrogel can be injected[3]. This pathway is very useful for the release of drugs or viable cells, since the low viscosity material assumes a gel form after application[4]. The ability to be injected allows the material to be presented as a minimally invasive alternative for minor procedures, which may lead to numerous benefits[5]. The aim of the present study was to analyze the application of the hydrogel Poli(NIPAAm-co-AAc-co-HEMAPLDLA-co-TMC) in live animals, following the tissue reactions triggered around. The polymer was implanted through injections in the subcutaneous tissue of the posterior dorsum of 21 Wistar rats. After a period of 5, 7, 10, 15, 21 and 30 days the animals were sacrificed by overdose of halothane for subsequent histological analysis. As a result, the absence of inflammatory reaction was verified at the implant sites, in addition to the presence of gaps in the tissue, due to the processing of the implanted hydrogel. Still, histological analysis showed a reduction in the amount of hydrogel, according to the different times of sacrifice. Due to the thermosensitive characteristic of the PNIPAAm component of the hydrogel Poli(NIPAAm-co-AAc-co-HEMAPLDLA-co-TMC), it was expected that the polymer could solidify at the site of application and be identified by the swelling caused in this process, or by the remnant of material present on site. However, there was no evidence that the implanted hydrogel had swollen. In addition, there were no macroscopic or microscopic evidences of the polymer in the material collected from implant sites. An association of hydrogel with dye ink was necessary to discover the location of the injected material and carry out further analysis of the sample. The dissipation of the hydrogel and the absence of material swelling may have occurred due to the addition of other substances to the hydrogel Poli(NIPAAm-co-AAc-co-HEMAPLDLA-co-TMC) composition, which could modify its thermosensitive characteristic. Otherwise, the implant site may not have been suitable for its solidification. The results presented in this study suggest that the hydrogel Poli(NIPAAm-co-AAc-co-HEMAPLDLA-co-TMC) has biocompatibility and potential as a filling material. However, further studies of this hydrogel are needed to get a better definition of its sol-gel transition, in order to understand its thermosensitivity and identify the presence of the polymer without addition of a dye ink.