Degradation of Regenerated Silk Fibroin in Soil and Marine Environments

Abstract

There is a compelling need to find new materials that meet stringent performance requirements for application in food, water, and agriculture industries while addressing biodegradability, circular life cycle, and sustainable sourcing at scale. Regenerated silk fibroin (SF) is a structural biopolymer with applications in biomedicine, optoelectronics, food, water, and agriculture. Extracted from largely available Bombyx mori cocoons through a water-based process, SF is fabricated into advanced materials that have competitive performance and merits of natural origin and nontoxicity. As a protein, SF is considered slowly degradable in the human body, but as a material, it is known to be environmentally stable, and its biodegradation is mostly unknown. In this study, the degradation of SF in different soil and water environments is investigated. The effects of SF polymorphism, ionic strength, and the presence of microorganisms on proteinaceous material degradation are investigated. Modulation of beta-sheet content allowed us to control the degradation rate of SF films in soil of increasing NaCl concentration. Microbial activity was a key driver for silk degradation under different environmental conditions. Bacterial colonization accelerated silk film degradation, a process that was further enhanced by encapsulation of bacteria in SF materials at the point of material assembly. Together, these data show that SF biodegradation can be controlled by material design and by regulating the interaction with microorganisms present in the environment.

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

“…The biodegradable nature of silk fibroin also does not indicate reduced reliability or increased instability of the silk MPs tag. It has been widely reported in the literature that silk can be degraded by certain proteolytic enzymes (e.g., protease XIV and α-chymotrypsin), soil microbes and in marine environment, and the degradation rates vary from days to years depending on the crystallinity of silk ( 44 , 45 ). As such, silk is considered as a biodegradable material, which we believe is an advantage as compared to nonbiodegradable materials such as gold nanoparticles and certain plastics that have been used in making PUFs before ( 17 ).…”

Design of Biodegradable, Climate-Specific Packaging Materials That Sense Food Spoilage and Extend Shelf Life

“…Silk fibroin is considered non-biodegradable in vivo by the US pharmacopoeia due to the slow resorption of silk-based suture threads. , However, biodegradation in vivo of silk materials has been largely studied, together with the protein biodegradation in soil and marine environments . The three COFs considered in this study are also known to degrade .…”

“…40,41 However, biodegradation in vivo of silk materials has been largely studied, 42 together with the protein biodegradation in soil and marine environments. 31 The three COFs considered in this study are also known to degrade. 43 To explore the biodegradation of the proposed SF-COF materials, we investigated their loss of mass when exposed to soil.…”

“…SF, extracted from Bombyx mori cocoons, is an edible structural protein widely used for various applications owing to excellent mechanical properties, nontoxicity, hydrophobicity, and programmable biodegradability (Figure A). − The polymorphism and controlled transition from random coil to beta-sheet provide high flexibility, conformability, and tunable permeability to water and oxygen in the regenerated film format, , which enables the potential use of SF as packaging material to extend food shelf life. The COF, an emerging crystalline porous material, has received increasing attention due to its tunable porosity and modifiable skeletons .…”

Drug Delivery in Plants Using Silk Microneedles

“…The fabrication material, silk fibroin—a structural protein extracted from cocoons of Bombyx mori —is processed in water, is considered nontoxic, edible and it is biodegradable. [ 2b,32 ] In addition, silk fibroin has shown capability to preserve labile compounds, indicating the possibility of using silk‐based microneedles to deliver environment‐sensitive agrochemicals.…”