Binary Biobased Supramolecular Colloidal Suspensions: A Model for Sustainable Antibacterial Coatings and Soft Carrier Systems

Applying antibacterial coatings onto food processing surfaces is essential for mitigating bacterial contamination, ensuring food safety, and maintaining hygienic standards in food production environments. This study explores environmentally friendly and food-safe antibacterial colloidal suspensions consisting of aggregated chitosan-pectin (CTS-Pec) coacervate complexes for applications in spray coatings and stimuli-responsive nanocarriers. Motivated by the lack of comprehensive studies on colloidal suspensions consisting of aggregated CTS-Pec coacervation complexes and the antibacterial properties of positively charged coacervate suspensions, this work serves as a complementary contribution to this area. Aqueous spontaneous ionic gelation was employed to synthesize CTS-Pec coacervate suspensions, systematically examining the effects of the biopolymer concentration, order of addition, mass ratio, and solution pH on coacervate formation. Analytical techniques were utilized to determine the physicochemical properties, while particle size and zeta potential analyses revealed that excess Pec led to negatively charged particles. The latter yielded larger particles versus particles prepared with excess CTS ratios, which yielded positively charged particles. Comprehensive MIC assays showed the antibacterial effectiveness of the positively charged nanoparticles, highlighting the role of surface charge and pH dependency. Notably, this study demonstrated that lower Pec concentrations could still produce positively charged particles, even at excess Pec-stoichiometric ratios, making them suitable for spray-on coatings. Additionally, the stimuli-responsive properties of the aggregated CTS-Pec coacervate systems were validated through pH-responsive absorption and pH- and temperature-dependent drug release behavior using methylene blue (MB) as a model system. These findings underscore the potential of aggregated CTS-Pec coacervate systems as sustainable, multifunctional materials for antibacterial applications and advanced drug delivery.