This work was focused on developing bioactive materials from cellulose, mainly in the form of nanofibrils (CNF). The main efforts involved modifications to adjust the surface behavior (adsorption and fouling) and wet strength of CNF in various structures. In addition to other surface analytical techniques, ultrathin films of CNF were investigated by surface plasmon resonance (SPR) and quartz crystal microbalance with dissipation monitoring (QCM-D). Additionally, CNF nanopapers and wet-spun filaments were prepared and modified with functional properties, including bioactivity. The effect of molecular architecture of block and random copolymers of poly(2-(dimethylamino)ethyl methacrylate) (PDMEAMA) and poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA) on adsorption on substrates with low, medium and high density of electrostatic charges, namely, regenerated cellulose, CNF and TEMPO-oxidized CNF (TOCNF) was investigated. Polymer adsorption was mainly driven by electrostatic interactions between anionic groups of the cellulosic materials and cationic segments of the copolymers. Charge neutralization upon adsorption of block copolymers onto TOCNF was accompanied with significant water expulsion from the interface. The copolymers were highly efficient in producing antifouling TOCNF surfaces by reducing non-specific human IgG adsorption. The blocking efficiency was determined to be between 84-100%, depending on the polymer architecture. Remarkably, the copolymer passivation did not impair the selectivity and sensitivity of the TOCNF biointerfaces toward anti-human IgG after complementary bioactive molecules were installed by EDC/NHS coupling. The copolymer passivation reduced the otherwise nine-fold false response by the biointerface. Water-resistant CNF was prepared by TEMPO-oxidation and EDC/NHS coupling of aminobenzophenone to CNF (BP-CNF). Nanopapers and wet-spun filaments with superior wet strength (230-fold increase) were prepared from BP-CNF upon UV-activated crosslinking. The BP-CNF material was suitable for a secondary activation cycle with EDC/NHS to introduce bioactivity without significant interference from the BP functionalization. An anti-hemoglobin biointerface prepared on BP-CNF presented excellent affinity with hemoglobin, yet minimal non-specific adsorption as probed with human serum albumin. The results point to the possibility of tuning the systems' sensitivity and selectivity by passivation with random copolymers. Additionally, the BP-CNF filaments exhibiting anti-hemoglobin biointerfaces were employed successfully in testing of hemoglobin with fluorescence-labelled secondary antibodies. Overall, the work presented a method to adjust the material properties of cellulosic nanomaterials to allow their adoption in biomedical applications and biosensor development, without compromising the potential of the material for bioactivation.
|Translated title of the contribution||Nanoselluloosabiorajapintojen ominaisuuksien muokkaus|
|Publication status||Published - 2017|
|MoE publication type||G5 Doctoral dissertation (article)|
- cellulose nanofibrils
- copolymer adsorption
- UV-activated crosslinking
- wet strength