Glycine-spacers influence functional motifs exposure and self-assembling propensity of functionalized substrates tailored for neural stem cell cultures

Francesca Taraballi

doi:10.3389/neuro.16.001.2010

Abstract

The understanding of phenomena involved in the self-assembling of bio-inspired biomaterials acting as three-dimensional scaffolds for regenerative medicine applications is a necessary step to develop effective therapies in neural tissue engineering. We investigated the self-assembled nanostructures of functionalized peptides featuring four, two or no glycine-spacers between the self-assembly sequence RADA16-I and the functional biological motif PFSSTKT. The effectiveness of their biological functionalization was assessed via in vitro experiments with neural stem cells (NSCs) and their molecular assembly was elucidated via atomic force microscopy, Raman and Fourier Transform Infrared spectroscopy. We demonstrated that glycine-spacers play a crucial role in the scaffold stability and in the exposure of the functional motifs. In particular, a glycine-spacer of four residues leads to a more stable nanostructure and to an improved exposure of the functional motif. Accordingly, the longer spacer of glycines, the more effective is the functional motif in both eliciting NSCs adhesion, improving their viability and increasing their differentiation. Therefore, optimized designing strategies of functionalized biomaterials may open, in the near future, new therapies in tissue engineering and regenerative medicine.

Highlights

The “bottom up” approach for creating new biomaterials in nanomedicine and tissue engineering is achieving a consistent approval among the scientific community (Gazit, 2007)
We investigated the self-assembled nanostructures of functionalized peptides featuring four, two or no glycine-spacers between the self-assembly sequence RADA16-I and the functional biological motif PFSSTKT.The effectiveness of their biological functionalization was assessed via in vitro experiments with neural stem cells (NSCs) and their molecular assembly was elucidated via atomic force microscopy, Raman and Fourier Transform Infrared spectroscopy
glycine spacer (Gs) were used as hinges between the two peptide segments not to compromise the self-assembly of the RADA16-I part and the exposure of the biological motif

Summary

Introduction

The “bottom up” approach for creating new biomaterials in nanomedicine and tissue engineering is achieving a consistent approval among the scientific community (Gazit, 2007). Self-assembling peptides can be prepared via solid-phase synthesis with precise control over sequence, molecular dimension and functionalization Zhang and his coworkers developed short amphiphilic peptides (e.g. RADA16-I) able to mimic the extra cellular matrix, so to be intriguing scaffolds for tissue engineering applications (Yokoi et al, 2005). The 12- to 16-mer peptide class discovered by Zhang folds into double layered β-sheets to form nanofibers featuring folded molecular structures similar to amyloid proteins (Yokoi et al, 2005). In this peptide class the process of assembling is triggered by physiological ranges of pH and temperature. A wide range of FPs have been developed, adding different biological motifs at Frontiers in Neuroengineering www.frontiersin.org

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