Silk's cancer applications as a biodegradable material

Silk is a polymer commonly found in silkworm Bombyx mori (B. mori) cocoons and has great potential as the next notable sustainable biomaterial of the medical field. It primarily comprises two proteins: sericin and fibroin, the latter of which is removed in primary silk processing. The regenerated silk solution that results from silk processing may then be converted into a multitude of forms such as gels, foams, nanoparticles, and wafers. Some of its inherent properties such as its high biodegradability, biocom-patibility, mechanical properties, and unique chemical structure have garnered the attention of many researchers across different fields. These many properties are manipulable in nature and offer further routes of optimization in silk's applications, especially in the field of cancer drug delivery. Researchers have managed to exploit some of silk's properties such as its first-order drug release profile and pH sensitivity for applications in the cancer tumor microenvironment, such as sustained drug delivery and pH-triggered drug release of silk nanoparticles. Silk possesses unique advantages in gene delivery, as transfection efficiency can be enhanced through the addition of cationic charges and functional groups (e.g., tumor-homing peptide, nuclear localization sequence) via chemical and physical modifications. Here, we review the in vivo and in vitro applications of silk fibroin as a sustainable and biodegradable biomaterial for cancer drug delivery. (c) 2021 Elsevier Ltd. All rights reserved.