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- Alternative synthesis methods of electrically conductive bacterial cellulose-polyaniline composites for potential drug delivery applicationPublication . Alonso, Pedro Emanuel de Gouveia; Cordeiro, Nereida Maria AbanoBacterial cellulose/polyaniline (BC/PANi) nanocomposites have been lately receiving attention by the scientific community towards the development of electronic applications. The current work aims to determine the most suitable BC modification method to obtain an effective drug delivery membrane through electric stimulus. Thus, the BC/PANi nanocomposites were synthesized through the employment of different BC matrixes (drained, freeze dried and regenerated), as well as through different polymerization methods (in situ and ex situ). Prior to modification, the effects of both drying methods (freeze drying and oven drying), and regeneration process on BC structure were studied. By freeze drying BC, the fibril network is preserved, leading to a more porous material. On the other hand, regenerated BC presented a compact surface due to the incapacity to reorganize into fibrils during the regeneration process. This way, freeze dried BC should be more suited for modification. To obtain a highly conductive nanocomposite, the in situ polymerization on drained BC should be employed. The introduction of PANi onto BC obstructed the pores, which led into a more compact and rougher material. Also, a decrease in the thermal stability, as well as a decrease in the BC crystallinity was observed. The nanocomposites were drug loaded with sodium sulfacetamide to evaluate the antimicrobial activity. It was observed that without electrical stimulus, only drug loaded drained in situ BC/PANi nanocomposite presented an inhibitory effect onto the Escherichia coli (E. coli) growth (13%). By applying electric stimulus onto this membrane, the inhibition in E. coli growth is further evidenced (20%). This way, in situ polymerization of aniline on drained BC presented to be an effective method to create a highly conductive membrane for drug release through electrical stimulus.
- Conductive bacterial cellulose-polyaniline blends: Influence of the matrix and synthesis conditionsPublication . Alonso, Emanuel; Faria, Marisa; Mohammadkazemi, Faranak; Resnik, Matic; Ferreira, Artur; Cordeiro, NereidaBacterial cellulose/polyaniline (BC/PANi) blends present a great potential for several applications. The current study evaluates the impact of using different BC matrixes (drained, freeze-dried and regenerated) and different synthesis conditions (in situ and ex situ) to improve the inherent properties of BC, which were monitored through FTIR-ATR, EDX, XRD, SEM, AFM, swelling, contact angle measurement and IGC. The employment of in situ polymerization onto drained BC presented the most conductive membrane (1.4 × 10-1 S/cm). The crystallinity, swelling capacity, surface energy and acid/base behavior of the BC membranes is substantially modified upon PANi incorporation, being dependent on the BC matrix used, being the freeze-dried BC blends the ones with highest crystallinity (up to 54%), swelling capacity (up to 414%) and surface energy (up to 75.0 mJ/m2). Hence, this work evidenced that the final properties of the BC/PANi blends are greatly influenced by both the BC matrixes and synthesis methods employed.
- Influence of the matrix and polymerization methods on the synthesis of BC/PANi nanocomposites: an IGC studyPublication . Alonso, Emanuel; Faria, Marisa; Ferreira, Artur; Cordeiro, NereidaInverse gas chromatography (IGC) is a technique for evaluating surface properties. The current work emphasizes the use of IGC to evaluate the surface physicochemical changes during different bacterial cellulose (BC) processing methods as well as upon polyaniline (PANi) incorporation. The processing methods (oven-drying, freeze-drying, and regeneration) caused changes in the BC surface group distribution, where upon freeze-drying and regeneration, a more acidic behavior is obtained, compared to oven-drying (Kb/Ka decreased up to 24%). Through freeze-drying, the structural pore preservation increases (54%) the BC porosity, whereas through regeneration, the porosity decreases (23%), compared to BC oven-drying. Regarding the nanocomposites, with PANi incorporation, the overall properties evaluated by IGC were significantly changed. The γtotals increases up to 150%, indicating a more reactive surface in the nanocomposites. Also, is observed a sevenfold increase in the Kb/Ka and a less porous surface (up to 85%). Hence, the current work highlights the use of IGC as a viable technique to evaluate the physicochemical changes upon different BC modifications.
- Surface modification of banana fibers using organosilanes: an IGC insightPublication . Alonso, Emanuel; Pothan, Laly A.; Ferreira, Artur; Cordeiro, NereidaBanana fibers are an agricultural waste material with a great exploitation potential due to their cellulose-rich content. Raw banana fibers (RBF) were treated with 3-aminopropyltriethoxy silane and glycidoxypropyltrimethoxy silane to improve the inherent limitations of banana fibers, namely its poor cell adhesion. The fibers’ modification was evaluated by inverse gas chromatography (IGC). Similar cs d values were observed between the RBF and silane-treated fibers (39–41 mJ/m2 ), which indicates similar reactivity towards apolar probes. However, the decrease in the entropic parameter indicates the silane covalent bonding with the cellulose chains making a stiffer structure. Organosilane grafting was confirmed by an increased basic character in the silane-treated fibers (Kb/Ka from 1.03 to 2.81). The surface morphology also changed towards higher contact area (SBET increases 6.7 times) and porosity (Dp increases up to 67%). Both morphological and functional group reactivity changes suggest that the organosilane treatment offers new opportunities for these fibers to be used as adsorbents for proteins as well as to cell adhesion. Therefore, IGC proved a simple and viable technique in the characterization of silane-treated fibers.