Smart alginate-based hydrogels: An approach for optimized nutrient distribution to plant-associated microbiomes | Poster Board #681

Sustainable agriculture stands as a paramount environmental engineering challenge for the 21st century, as recognized by the National Academies. Conventional farming practices often employ broad fertilization strategies, where over 50% of applied fertilizers fail to reach intended crop plants. These methods overlook the potential of harnessing the soil microbiome to bolster plant health. Arbuscular mycorrhizal (AM) fungi, forming symbiotic associations with over 80% of crop plants, play a pivotal role in nutrient acquisition, particularly nitrogen and phosphorus, thereby enhancing plant nutrient and water use efficiencies as well as resistance against pathogens. However, existing agricultural approaches inadequately address the nurturing of this mutualistic relationship. In this study, we introduce "smart" controlled release systems, originally derived from biomedical engineering, into sustainable agriculture to foster symbiotic interactions between AM fungi and plants. As a model system, alginate hydrogels cross-linked with iron (Fe) ions were explored, considering the capacity of AM fungi to release iron chelating siderophores, thus potentially facilitating gel degradation. These "nutrient patches," synthesized in the presence of nitrogen or phosphate ions, were designed for targeted delivery to plants and AM fungi. Hydrogels, approximately 8 mm in size, were fabricated via ion-induced cross-linking in molds. The encapsulation of nitrogen was validated through Raman spectroscopic analysis, confirming concentrations of 1140 mg/ml. Subsequent release kinetics from the patches into agar culture media were assessed using Raman spectroscopy, monitoring both spatial distribution and temporal profiles. Moreover, patch dissolution dynamics were examined in the presence of general and AM fungal-specific siderophores, revealing a significant increase in dissolution over 24 hours when siderophores were present. Furthermore, a comprehensive biocompatibility evaluation of these nutrient patches was conducted in conjunction with AM fungi and their respective plant hosts. Collectively, our findings demonstrate the proof-of-concept of employing "smart" release systems tailored for the soil microbiome, underscoring their potential in advancing fertilization strategies for sustainable agriculture.