Engineering and Functionalization of Hemicellulose Hydrogels

Abstract: Hemicellulose is the second most abundant component in wood and is an important renewable resource  that is used in films, paper composites and biofuels.  Hemicelluloses  have  several  advantages,  including  their abundance,  degradability  and  renewability.  O-acetyl-galactoglucomannan (AcGGM) is a type of hemicellulose that is predominantly found in softwood specimens. In the recent drive to engineer functional hydrogels with stimuli-responsive  properties,  functional  AcGGM-derived  hydrogels  are  highly interesting alternatives. In  the  first  part  of  this  thesis,  a  combination  of  the  electro-activity  of conducting oligomers and AcGGM was used to design a robust pathway to generate  electrically  conductive  hemicellulose  hydrogels  (ECHHs)  using AcGGM  and  a  conductive  aniline  tetramer.  Subsequently,  in  order  to fabricate  ECHHs  using  a  greener  and  more  facile  approach,  a  one-pot reaction  was  performed  in  which  AcGGM  was  cross-linked  with epichlorohydrin in the presence of a conductive aniline pentamer in water at ambient  temperature.  To  impart  other  functionalities  to  the  hemicellulose hydrogels,  magnetic  field-responsive  hemicellulose  hydrogels  (MFRHHs) were  fabricated  by  simultaneous  in  situ  formation  of  magnetic  Fe 3 O 4   and cross-linking of AcGGM. These MFRHHs exhibited  a controlled release of the  protein  bovine  serum  albumin.  Finally,  a  facile,  fast  and  functional chemical  methodology  to  prepare  stimuli-responsive  hemicellulose  micro-gels was developed that offers the potential for fabricating hydrogels using a green  processing  technique.  The  micro-gels  were  shown  to  have  a  rapid response to electrochemical stimuli, pH alterations and a magnetic field, as well  as  good  blood  compatibility,  which  is  required  for  biomedical applications.  All  these  stimuli-responsive  hemicellulose  hydrogels  demonstrated controllable  aqueous  swelling  behavior  and  combine  the  renewability  of hemicellulose  and  stimuli-responsiveness  of  functional  molecules,  thereby opening new potential routes to fabricate biomaterials with a wide range of applications  (e.g.,  biosensors,  nerve  system  repair,  and  controlled  drug release).