The Effect of Sterilization on the Characteristics of Silk Fibroin Nanoparticles

Abstract

In recent years, silk fibroin nanoparticles (SFNs) have been consolidated as drug delivery systems (DDSs) with multiple applications in personalized medicine. The design of a simple, inexpensive, and scalable preparation method is an objective pursued by many research groups. When the objective is to produce nanoparticles suitable for biomedical uses, their sterility is essential. To achieve sufficient control of all the crucial stages in the process and knowledge of their implications for the final characteristics of the nanoparticles, the present work focused on the final stage of sterilization. In this work, the sterilization of SFNs was studied by comparing the effect of different available treatments on the characteristics of the nanoparticles. Two different sterilization methods, gamma irradiation and autoclaving, were tested, and optimal conditions were identified to achieve the sterilization of SFNs by gamma irradiation. The minimum irradiation dose to achieve sterilization of the nanoparticle suspension without changes in the nanoparticle size, polydispersity, or Z-potential was determined to be 5 kiloGrays (kGy). These simple and safe methods were successfully implemented for the sterilization of SFNs in aqueous suspension and facilitate the application of these nanoparticles in medicine.

Optimizing the Preparation of Silk Fibroin Nanoparticles and Their Loading with Polyphenols: Towards a More Efficient Anti-Inflammatory Effect on Macrophages

“…Once the nanoparticles were loaded with CUR, Q and RES, before being used for the biological tests, their suspensions at 10 mg·mL −1 in ultrapure water were irradiated at 2.5 kGy for sterilization as previously described [ 21 ] without appreciable changes in the color or aggregation state. Only a statistically significant reduction in the Z ave of SFN-CUR (Tukey, p < 0.05) was appreciated after the sterilization.…”

“…SFN prepared for the biological assays, either naked or loaded with PPh, were sterilized by γ-irradiation, as previously described [ 21 ], and stored at 4 °C until use.…”

“…Free PPh (CUR, Q and RES) were dissolved in dimethyl sulfoxide (DMSO) at a concentration of 10 mg·mL −1 . Working solutions at a concentration of 1000 μg·mL −1 for each of the tested nanoparticles were prepared from the SFN-PPh suspensions at 10 mg·mL −1 (sterilized by γ-irradiation at 2.5 kGy as previously described [ 21 ]) by dilution with sterile phosphate-buffered saline (PBS), pH = 7.4 (Biowest, Nuaillé, France). Serial dilutions of the stocks were made at the appropriate concentration in complete cell-culture medium (CCM) prior to being used in the in vitro assays.…”

“…Additionally, the method based on the precipitation of dialyzed aqueous solutions of fibroin is time-consuming and requires large volumes of water to remove the necessary salts for the dissolution of natural silk fibers. As the production of SFN for biomedical applications is expected to increase in the coming years [ 21 ], having a fast and scalable production method is mandatory.…”

Liquid-type plasma-controlled in situ crosslinking of silk-alginate injectable gel displayed better bioactivities and mechanical properties

“…The final concentration of silk fibroin solution was 8–10 ​wt% and it was stored in a refrigerator until use. A 1% (w/v) alginate powder was dissolved homogeneously in concentrated silk fibroin solution and autoclaved at 121 ​°C for 5 ​min [ [26] , [27] , [28] ]. Three groups of solutions were prepared as follows: (1) alginate, (2) silk-alginate, and (3) LTP-treated silk-alginate, and all three solutions were mixed with calcium chloride solution (250 ​mM) as crosslinker ( Table S1 ).…”