In the past decade there has been increasing interest in exploring the use of nanocellulose in medicine. However, the influence of the physicochemical properties of nanocellulose on the material´s biocompatibility has not been fully investigated.  In this thesis, thin films of nanocellulose from wood (NFC) and from Cladophora algae (CC) were modified by the addition of charged groups on their surfaces and the influence of these modifications on the material´s physicochemical properties and on cell responses in vitro was studied. The results indicate that the introduction of charged groups on the surface of NFC and CC results in films with decreased surface area, smaller average pore size and a more compact structure compared with the films of unmodified nanocelluloses. Furthermore, the fibres in the carboxyl-modified CC films were uniquely aggregated and aligned, a state which tended to become more prevalent with increased surface-group density. The biocompatibility studies showed that NFC films containing hydroxypropyltrime-thylammonium (HPTMA) groups presented a more cytocompatible surface than unmodified NFC and carboxymethylated NFC regarding human dermal fibroblasts. Carboxymethyl groups resulted in NFC films that promoted inflammation, while HPTMA groups had a passivating effect in terms of inflammatory response.  On the other hand, both modified CC films behaved as inert materials in terms of the inflammatory response of monocytes/macrophages and, under pro-inflammatory stimuli, they suppressed secretion of the pro-inflammatory cytokine TNF-α, with the effects of the carboxylated CC film more pronounced than those of the HPTMA CC material.  Carboxyl CC films showed good cytocompatibility with fibroblasts and osteoblastic cells. However, it was necessary to reach a threshold value in carboxyl-group density to obtain CC films with cytocompatibility comparable to that of commercial tissue culture material.  The studies presented here highlight the ability of the nanocellulose films to modulate cell behaviour and provide a foundation for the design of nanocellulose-based materials that trigger specific cell responses. The bioactivity of nanocellulose may be optimized by careful tuning of the surface properties. The outcomes of this thesis are foreseen to contribute to our fundamental understanding of the biointerface phenomena between cells and nanocellulose as well as to enable engineering of bioinert, bioactive, and bioadaptive materials.

Submitted by Josmary Karoline Demko Alves (josmarykaroline@yahoo.com.br) on 2016-10-29T19:29:03Z No. of bitstreams: 1 Dissertação Josmary vfinal.pdf: 958731 bytes, checksum: 99f22613883eb6a31dcd046c8ee98a08 (MD5) / Approved for entry into archive by ÁUREA CORRÊA DA FONSECA CORRÊA DA FONSECA (aurea.fonseca@fgv.br) on 2017-01-25T12:38:46Z (GMT) No. of bitstreams: 1 Dissertação Josmary vfinal.pdf: 958731 bytes, checksum: 99f22613883eb6a31dcd046c8ee98a08 (MD5) / Made available in DSpace on 2017-02-02T18:20:37Z (GMT). No. of bitstreams: 1 Dissertação Josmary vfinal.pdf: 958731 bytes, checksum: 99f22613883eb6a31dcd046c8ee98a08 (MD5) Previous issue date: 2016-08-29 / Estruturas sociais influenciam a efetividade dos grupos. O propósito deste estudo é explorar os efeitos contingenciais dessa relação por meio da investigação da densidade em diferentes redes na performance das equipes. Hipotetizou-se, primeiramente, o efeito oposto para densidade instrumental e afetiva em performance das equipes; posteriormente, argumenta-se que interdependência das tarefas e a orientação de distância de poder agem como moderadores. Para testar as hipóteses, foram utilizadas informações de questionários coletados de 27 Unidades de Pronto Atendimento (UPA) e 106 grupos. O resultado encontrado suporta o efeito positivo de densidade instrumental e o impacto negativo da densidade afetiva. Além disso, provou-se que a interdependência de tarefas atenua ambas as relações diretas. Ao final, são discutidas as implicações destes resultados para pesquisa em densidade das redes e performance das equipes. / Social structures influence team effectiveness. The purpose of this study is to explore the contingencies effects of this relationship by investigating density in distinct network contents on team performance. We first hypothesized opposite direct effects for instrumental and affective density on team performance; then we further argue that task interdependence and power distance orientation act as moderators. To test our hypotheses we use survey data from 27 Emergency and Care Units and 106 teams. The results support the positive effect of instrumental density and the negative impact of affective density. Moreover, task interdependence was found to attenuate both main relationships. We discuss the implications of these findings for research on network density and team performance.