Recent innovations in silk biomaterials

Silk contains a fibre forming protein, fibroin, which is biocompatible, particularly after removing the potentially immunogenic non-fibroin proteins. Silk can be engineered into a wide range of materials with diverse morphologies. Moreover, it is possible to regenerate fibroin with a desired amount of crystallinity, so that the biodegradation of silk materials can be controlled. These advantages have sparked new interest in the use of silk fibroin for biomedical applications, including tissue engineering scaffolds and carriers for sustained release of biologically active molecules. This article summarizes the current research related to the formation of silk materials with different morphologies, their biocompatibility, and examples of their biomedical applications. Recent work on the preparation of silk particles by mechanical milling and their applications in silk composite scaffolds is also discussed

Protein fiber particles for biomedical applications

Ultrafine protein particles have been fabricated from natural fibres, such as silk and wool. Our studies suggested that particles could be used for fabricating tough macro-porous composites scaffolds for tissue engineering. They are also efficient for reversible binding of metal ions. We are currently analyzing the sorption properties, biocompatibility and biodegradability of a range of particles to evaluate possibility for biomedical and healthcare applications

Biodegradable Eri silk nanoparticles as a delivery vehicle for bovine lactoferrin against MDA-MB-231 and MCF-7 breast cancer cells

This study used the Eri silk nanoparticles (NPs) for delivering apo-bovine lactoferrin (Apo-bLf) (~2% iron saturated) and Fe-bLf (100% iron saturated) in MDA-MB-231 and MCF-7 breast cancer cell lines. Apo-bLf and Fe-bLf-loaded Eri silk NPs with sizes between 200 and 300 nm (±10 nm) showed a significant internalization within 4 hours in MDA-MB-231 cells when compared to MCF-7 cells. The ex vivo loop assay with chitosan-coated Fe-bLf-loaded silk NPs was able to substantiate its future use in oral administration and showed the maximum absorption within 24 hours by ileum. Both Apo-bLf and Fe-bLf induced increase in expression of low-density lipoprotein receptor-related protein 1 and lactoferrin receptor in epidermal growth factor (EGFR)-positive MDA-MB-231 cells, while transferrin receptor (TfR) and TfR2 in MCF-7 cells facilitated the receptor-mediated endocytosis of NPs. Controlled and sustained release of both bLf from silk NPs was shown to induce more cancer-specific cytotoxicity in MDA-MB-231 and MCF-7 cells compared to normal MCF-10A cells. Due to higher degree of internalization, the extent of cytotoxicity and apoptosis was significantly higher in MDA-MB-231 (EGFR+) cells when compared to MCF-7 (EGFR-) cells. The expression of a prominent anticancer target, survivin, was found to be downregulated at both gene and protein levels. Taken together, all the observations suggest the potential use of Eri silk NPs as a delivery vehicle for an anti-cancer milk protein, and indicate bLf for the treatment of breast cancer

Fabricating and characterising silk powder for biomedical and sorption applications

This research developed a milling technology for ultrafine silk particles and designed novel biocompatible and biodegradable silk composites for repairing hard tissue defects. It also demonstrated high and rapid reversible ion binding properties of silk particles and thereby opened up their application opportunities as advanced green sorbents

Drug loading and release studies for milled silk particles of different sizes

Milled silk particles with volume median particle size (d(0.5)) of 7 μm and 281 nm as well as silk snippets were used for loading of model drugs Orange G, Azophloxine, Rhodamine B, and Crystal Violet. Loading and release of these chemicals depended on the size of silk particles, pH, and the structure and properties of model drugs. Both types of silk particles reached equilibrium loading in less than 10 min due to high surface area whereas silk fibres needed more than 2-3 days to reach equilibrium, depending on the drug type. The uptake rate in fibres could be improved by increasing temperature. Both fibres and particles could slowly release the drugs over many days at 37 °C without a significant initial burst. As particle size decreased, the amount of model drug release also decreased. The release of drugs by the silk fibres was quicker than the silk particles