Microencapsulation of High‐Content Actives Using Biodegradable Silk Materials

Abstract

There is a compelling need across several industries to substitute non‐degradable, intentionally added microplastics with biodegradable alternatives. Nonetheless, stringent performance criteria in actives’ controlled release and manufacturing at scale of emerging materials hinder the replacement of polymers used for microplastics fabrication with circular ones. Here, the authors demonstrate that active microencapsulation in a structural protein such as silk fibroin can be achieved by modulating protein protonation and chain relaxation at the point of material assembly. Silk fibroin micelles’ size is tuned from several to hundreds of nanometers, enabling the manufacturing—by retrofitting spray drying and spray freeze drying techniques—of microcapsules with tunable morphology and structure, that is, hollow‐spongy, hollow‐smooth, hollow crumpled matrices, and hollow crumpled multi‐domain. Microcapsules degradation kinetics and sustained release of soluble and insoluble payloads typically used in cosmetic and agriculture applications are controlled by modulating fibroin's beta‐sheet content from 20% to near 40%. Ultraviolet‐visible studies indicate that burst release of a commonly used herbicide (i.e., saflufenacil) significantly decreases from 25% to 0.8% via silk fibroin microencapsulation. As a proof‐of‐concept for agrochemicals applications, a 6‐day greenhouse trial demonstrates that saflufenacil delivered on corn plants via silk microcapsules reduces crop injury when compared to the non‐encapsulated version.

Charge, Aspect Ratio, and Plant Species Affect Uptake Efficiency and Translocation of Polymeric Agrochemical Nanocarriers

“…Previous studies have also shown that a positive charge can promote uptake of “hard” nanoparticles such as carbon dots and nanoceria by leaf mesophyll cells and chloroplasts of cotton and maize plants after foliar topical delivery . The current results also suggest that the charge of “soft” materials such as these polymer nanocarriers, or biopolymers that have been proposed as nanocarriers, , may behave similarly to the charge from “hard” particles with respect to nanomaterial-mesophyll cell interactions despite differences in their stiffness. However, the influence of other properties such as the flexibility of polymer nanomaterials may affect their ability to penetrate through plant barriers such as the cell wall and cell membrane.…”

Integrating biopolymer design with physical unclonable functions for anticounterfeiting and product traceability in agriculture

“…1A and fig. S1A) ( 29 ), followed by water annealing of those particles to induce formation of ordered molecular structures and render them water insoluble ( 30 ). The choice of the spray drying technique was based on its high efficiency in producing grams of protein powders per hour and its wide use in the industry ( 31 ).…”

Drug Delivery in Plants Using Silk Microneedles

“…Future work may extend to the encapsulation of micro-and nanomaterials into microneedles both in the form of payloads or carriers for other actives, such as metal nanoparticles for micronutrients and mesoporous silicon nanoparticles, for controlled release, where on-site in vitro aggregation and thus dysfunction of nanomaterials may be prevented. [3,34] The properties of microneedles can also be tuned to decrease burst release and target a sustained release of payloads via alternative biomaterials and post-treatment. [35]…”