Pick Your Poison: Benzalkonium Chloride and Copper Enable Nanocellulose Derivatives to Form Antimicrobial Properties Against a Spectrum of Microorganisms

TEMPO nanofibrillated cellulose (TNFC), nanofibrillated cellulose (NFC), carboxymethyl cellulose (CMC), and lignin were used as templates for the addition of two well-known antimicrobial substances, benzalkonium chloride (BZK) and copper. The resulting hybrid of cellulose and antimicrobial materials were analyzed for biocidal activity in three separate products. Assays of the nanocellulose-antimicrobials were assayed for viability against Escherichia coli in suspension, against Saccharomyces cerevisiae on PVA plastic, and against bacillus lincheniformis in paper additives. Instant biocidal activity was achieved with a minimal inhibitory concentration of 0.116 M BZK-TNFC hybrid suspension. BZK-Lignin and BZK-CMC suspensions demonstrated increased antimicrobial activity with longer exposure times during a 24-hour exposure which completely inhibited the bacteria. BZK was slowly released into the suspension, a desirable trait for long-term antimicrobial activity. PVA plastic incorporated with BZK/Cu-nanocellulose scaffolds created solid films that completely inhibited yeast growth by 270 seconds. Interestingly, lignin-BZK PVA films counteracted each other and showed no biocidal activity at all. The multiple combinations of nanocellulose and biocidal agents in the surface viability assay demonstrates the importance of synergy between both components in designing nanocellulose antimicrobials. TNFC-Cu was more suited to inhibit growth in paper than NFC-Cu as seen in a zone of inhibition assay. The most potent biocidal material in PVA was NFC-BZK. Here we show the diversity of the cellulosic derivatives and their impact on the antimicrobial additive. We employed a variety of assays to assess to biocidal of these nanoparticles against three species of bacteria and yeast relevant to food packaging and medical fields. From our study, there are many factors that play a role in the design of antimicrobial materials; cellulose derivative scaffold, antimicrobial agent, type of final material in which to be incorporated, target organism, and duration of application.