Degradation of Particle Laden Silk Fibroin Sponges for Controlled Payload Release

Silk Fibroin (SF), a protein derived from Bombyx mori silk fibers, has demonstrated significant potential as a versatile biomaterial for medical applications. SF can be processed into biocompatible, biodegradable, and highly customizable forms such as gels, sponges, and particles, making it ideal for tissue engineering [1, 2]. A key challenge in these applications is the controlled delivery of small molecules in specific quantities and sequences to guide tissue regeneration. To address this, we propose a hybrid material consisting of SF particles [3] embedded in an SF sponge [4]. The sponge structure provides a scaffold for cell infiltration and molecule retention, while the particles enable controlled release of small molecules.

We hypothesize that this particle-laden sponge will retain the mechanical properties of the bulk sponge while adding an enhanced level of controlled release. The sponges were prepared via lyophilization of frozen SF solution, followed by water annealing, while the particles were formed through liquid-liquid phase separation of SF and PVA solutions [1, 3]. To create the hybrid material, SF particles were incorporated into the SF solution used to form sponges [4, 5], followed by freezing, lyophilizing, and water annealing, which induced beta-sheet formation. The beta-sheet content is known to influence degradation rate, providing a tunable property based on annealing conditions (temperature, time, and pressure) [5-7].

To study the degradation kinetics of the hybrid material, we conducted a comparative analysis of pure SF sponges and 50/50 particle-laden sponges, degrading the samples with Protease XIV or Collagenase and visualizing changes using scanning electron microscopy. Time-dependent degradation data was fitted to a Michaelis-Menten kinetic model, yielding a modified first-order rate constant to describe the material's degradation and the associated release rate of an encapsulated payload [7]. Our results offer insights into how material composition and preparation can be optimized for tissue engineering applications.

References:

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[2] M. O. Pacheco et al., "Progress in silk and silk fiber-inspired polymeric nanomaterials for drug delivery," Front Chem Eng, Mini Review vol. 4, 2022, doi: 10.3389/fceng.2022.1044431.

[3] M. O. Pacheco et al., "Silk Fibroin Particles as Carriers in the Development of Hemoglobin-Based Oxygen Carriers," (in English), Adv Nanobiomed Res, vol. 3, no. 9, p. 2300019, Sep 2023, doi: 10.1002/anbr.202300019.

[4] E. L. Aikman et al., "Impact of crystalline domains on long-term stability and mechanical performance of anisotropic silk fibroin sponges," (in eng), J Biomed Mater Res A, vol. 112, no. 9, pp. 1451-1471, Mar 12 2024, doi: 10.1002/jbm.a.37703.

[5] J. Rnjak-Kovacina et al., "Lyophilized Silk Sponges: A Versatile Biomaterial Platform for Soft Tissue Engineering," (in eng), ACS Biomater Sci Eng, vol. 1, no. 4, pp. 260-270, Apr 13 2015, doi: 10.1021/ab500149p.

[6] Y. Kambe, Y. Mizoguchi, K. Kuwahara, T. Nakaoki, Y. Hirano, and T. Yamaoka, "Beta-sheet content significantly correlates with the biodegradation time of silk fibroin hydrogels showing a wide range of compressive modulus," Polym Degrad Stabil, vol. 179, p. 109240, 2020/09/01/ 2020, doi: https://doi.org/10.1016/j.polymdegradstab.2020.109240.

[7] J. F. Jameson, M. O. Pacheco, J. E. Butler, and W. L. Stoppel, "Estimating Kinetic Rate Parameters for Enzymatic Degradation of Lyophilized Silk Fibroin Sponges," (in English), Front Bioeng Biotech, Original Research vol. 9, no. 537, p. 664306, 2021-July-06 2021, doi: 10.3389/fbioe.2021.664306.