Cellulose-Based Enzyme-Responsive Microgels for Slow Release of Plant Growth Promoters for Sustainable Agriculture

In this study, we report chitosan cross-linked cellulose-based microgels (MCCh MGs) that are enzyme-responsive and can degrade in the presence of cellulase in soil. MCCh MGs are prepared by cross-linking methacrylated cellulose chains with chitosan via aza-Michael addition. These microgels are ∼383 nm in size, and they exhibit 8.2% loading efficiency and 86.5% encapsulation efficiency for 6-BA, which acts as a plant growth hormone. MCCh MGs exhibit an ∼40% release of 6-BA at pH 4.2 over 144 h. In contrast, ∼48% and ∼73% release of 6-BA is observed in the presence of 10U and 15U cellulase, respectively. Further investigations reveal that 6-BA@MCCh MGs significantly enhance seed germination, overall plant height, and weight for both black-eyed beans (Vigna unguiculata) and black chickpea (Cicer arietinum) seeds. Moreover, the assessment of black-eyed bean and black chickpea leaves obtained from plants treated with 6-BA@MCCh MGs exhibit 82 ± 0.12 mg/g and 40.51 ± 0.05 mg/g chlorophyll content, respectively, which is higher than the control leaves. These results clearly show the potential of developed microgel formulation for enhancing crop growth in a sustainable manner.