Brewed and Renewed: Preliminary Characterization and Antibiotic Potential of Chitosan Nanogels Loaded with Arabica (Coffea arabica) Spent Coffee Grounds

Abstract

Aims: The study aimed to determine the physicochemical characteristics of the C. arabica SCG-loaded nanogel, its wound healing potential through antibiotic activity in vitro, and its safety and stability through cytotoxicity and pH tests, respectively. Study Design: The study is experimental in nature and employed a Research and Development (R&D) research design. Place and Duration of Study: San Isidro College Wet Laboratory, Coffee Wagon, Central Mindanao University, and Mindanao State University, between February and March of 2025. Methodology: SCG extract was obtained through the solvent extraction method and prepared for use. Chitosan-based nanogels were then formulated, utilizing the ionic gelation method. Subsequently, the nanogels were characterized using Dynamic Light Scattering for particle size and UV-Vis spectrophotometer for drug loading capacity and encapsulation efficiency. Antibiotic activity was then measured in vitro through the Kirby-Bauer Disk Diffusion Assay for measurement of zone of inhibition while cytotoxicity was measured using the Brine Shrimp Lethality Assay across five (5) concentrations for preliminary cytotoxicity effects, and pH testing was replicated four (4) times. Results: The C. arabica SCG-loaded nanogels obtained a particle size ranging from 4470 nm to 6280 nm, indicating potential aggregation, and the particle PDI was reported at 0.01, suggesting uniformity of particles. Meanwhile, the nanogel exhibited a drug loading capacity of 4.76% and an encapsulation efficiency of 99.77%, attributed to having lower mass ratios. For the antibiotic testing, no zones of inhibition were formed. Furthermore, the nanogel was generally non-toxic and stable, with lethality of 11 out of 50 brine shrimp and a pH of 4.5, respectively. Conclusion: The findings suggest that the antibiotic activity of the nanogel may be limited due to prolonged release kinetics in which the in vitro study could not contain. Future studies may explore improvement of formulation process as well as utilizing other activity testing such as in vivo assays for a more definitive result.