Cellulose nanofibers produced from banana peel by chemical and mechanical treatments: characterization and cytotoxicity assessment

Cellulose nanoparticles from a vegetable source (cellulose fiber) have been evaluated for future use as reinforcement of polymeric matrixes (e.g., biodegradable films). Cellulose nanoparticles have numerous advantages: they are inexpensive and biodegradable, and they originate from renewable sources. Here, cellulose nanofibers (CNFs) were isolated from banana peel by chemical (alkaline treatment and bleaching followed by acid hydrolysis with 0.1, 1, or 10% (v/v) H2SO4) and mechanical (high pressure homogenizer) treatments. Atomic Force Microscopy (AFM) analysis showed all treatments effectively isolated banana fibers at the nanometer scale (average diameter of 3.72 nm). CNFs displayed -potential values ranging from -37.60 to -67.37 mV, which prevented their aggregation. CNFs had high crystallinity values, from 63.1 to 66.4%, which indicated they could be good reinforcing agents. FTIR results confirmed that the chemical and mechanical treatments removed the amorphous fractions. Regarding cytotoxicity, low CNF concentrations (50-500 g/mL) did not cause cell death, but CNFs at concentrations above 1000 g/mL significantly decreased cell viability. The use of different sulfuric acid concentrations provided more detailed knowledge of the treatment methods and CNF features, which could help to improve the CNF production process. The combination of chemical and mechanical treatments proved to be an efficient strategy to prepare CNFs from banana peels as a potential reinforcing agent of polymeric matrixes (e.g., food packaging).The authors would like to acknowledge the financial support provided by Coordenaçao de Aperfeiçoamento de Pessoal de Nível ~ Superior (2952/2011), Conselho Nacional de Desenvolvimento Científico e Tecnologico (150523/2013-0 and 140274/2014-6), and CAPES/FCT 349/13 for the PhD exchange program. Joana T. Martins acknowledges the Foundation for Science and Technology for her fellowship (SFRH/BPD/89992/2012). This study was supported by FCT under the scope of the strategic funding of UID/BIO/04469/ 2013 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684) and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte. This study was also supported by FCT under the scope of the Project RECI/BBBEBI/0179/2012 (FCOMP-01-0124-FEDER-027462). The authors would also like to acknowledge the Brazilian Nanotechnology National Laboratory (LNNano) for allocation of the TEM and AFM apparatus.