Cellulose nanofibrils (CNF) as a conjugate carrier and its potential as a high-barrier, UV-blocking, and low-intensity visible light-responsive antimicrobial packaging material

Abstract

Food quality deteriorates due to bacteria contamination, hence the need for antimicrobial packaging. Reactive oxygen species (ROS) have drawn interest as an antimicrobial strategy through combination of light irradiation, oxygen, and photosensitive components. In this study, titanium dioxide (TiO₂) and tetrakis(4-carboxyphenyl)porphyrin (TCPP) were combined to acquire conjugates with visible-light responsive photosensitivity. The conjugate was next incorporated into a low-pressure homogenized (0–25 cycles) cellulose nanofibril (CNF) matrix to address the notorious self-aggregation/quenching tendency. The novel, antibiotics-absent antimicrobial films successfully inactivated Escherichia coli completely after 72 h under 6000 lux-light irradiation, on top of the UV-A/B/C total blocking performance. Post-homogenization, surface smoothness (Sa, 2.5 from 7.0 μm), mechanical (TS, 44 from 25 MPa; TM, 5 from 3 MPa; EAB, 11 from 9 %), thermal (T_d,5 %, 295 from 100 °C; %W at 700 °C, 49 from 17 %), and contact angle (0–60 s) properties were also improved, confirming the influence of enhanced fibrillation and subsequent inter/intra-molecular hydrogen bonding. Low oxygen permeability at 50 %RH (0.05 cc.μm/m².day.kPa) was confirmed, comparable to reference values of several commercial high-barrier polymers (e.g., ethylene-vinyl alcohol brand of EVAL™ F, 0.05 cc.μm/m².day.kPa). This work ultimately certified CNF’s capability as a natural and biodegradable carrier of conjugate, as also confirmed morphologically by the even dispersion of conjugate. These findings showcased the promising potential for a myriad of antibacterial packaging applications even under considerably-low intensities of visible light.