The fabrication of self-assembling peptides into nanofiber scaffolds through molecular self-assembly
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The fabrication of self-assembling peptides into nanofiber scaffolds through molecular self-assembly Xiaojun Zhao¶, Jessica Dai¶ & Shuguang Zhang* Center for Biomedical Engineering NE47-379, Massachusetts Institute of Technology, Cambridge, MA 02139-4307, USA ¶ Both authors contributed equally. [email protected] http://web.mit.edu/lms/www
ABSTRACT We designed and fabricated a class of self-assembling peptides into nanofiber scaffolds. KLDL-12 has been shown to be a permissible nanofiber scaffold for chondrocytes in cartilage 3-D cell cultures. However, the biochemical, structural, and biophysical properties of KLDL12 remain unclear. We show that KLDL-12 peptides form stable β-sheet structures at different pH values and that KLDL-12 and RIDI-12 self-assemble into nanofibers. The nanofiber length, though, is sensitive to pH changes. These results not only suggest the importance of electrostatic attraction or repulsion affecting the fiber lengths but also provide us with useful information for rational design and fabrication of peptide scaffolds. INTRODUCTION Tissue regeneration and tissue engineering present a very complex task and require a multidisciplinary approach. Cells need to grow in a 3-dimentional scaffold that should mimic the extracellular matrix to help regulate many aspects of cell development, including survival, differentiation, migration, and maturation (1-5).
Currently, the scaffolds used in tissue
engineering are largely made from biopolymers such as PLA, PLGA, and others or animalderived proteins such as collagen and fibrin (1-5). These biomaterials have greatly accelerated tissue engineering and regenerative medicine research. However, this endeavor not only needs more suitable biological materials, it also needs materials that can be designed and fabricated according to specific needs.
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In the last decade, we discovered, developed, and fabricated a new class of biological materials that can undergo self-assembly into nanofibers and further form hydrogels with extremely high water content, 99-99.9% water (w/v) (6-28). One of these peptide scaffolds is KLDL-12, which formed hydrogels that fostered chondrocyte growth and cartilage tissue formation (10). However, KLDL-12 and its derivative RIDI-12 have not been characterized for their biochemical, structural and biophysical properties. To understand the relationship between structure and function, we used several different types of tools, including AFM, Circular Dichrosim (CD) and dynamic light scattering (DLS), to study these peptides and their nanofiber structural formations. MATERIALS AND METHODS Peptide solutions Self-assembling peptide, KLDL-12 (AcN-KLDLKLDLKLDL-CNH2) and RIDI-12 (AcNRIDIRIDIRIDI-CNH2), powder were dissolved in Milli-Q water at 0.5% (w/v) and diluted with Milli-Q water to different concentrations for further experiments. The pH values of the diluted solutions were adjusted using 0.1 N HCl or 0.1 N NaOH. Circular Dichroism (CD) spectroscopy CD spectroscopy was performed on sample solutions with an
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