Designing Silk-silk Protein Alloy Materials for Biomedical Applications

Summary

Blending is an efficient approach to generate biomaterials with a broad range of properties and combined features. By predicting the molecular interactions between different natural silk proteins, new silk-silk protein alloy platforms with tunable mechanical resiliency, electrical response, optical transparency, chemical processability, biodegradability, or thermal stability can be designed.

Abstract

Fibrous proteins display different sequences and structures that have been used for various applications in biomedical fields such as biosensors, nanomedicine, tissue regeneration, and drug delivery. Designing materials based on the molecular-scale interactions between these proteins will help generate new multifunctional protein alloy biomaterials with tunable properties. Such alloy material systems also provide advantages in comparison to traditional synthetic polymers due to the materials biodegradability, biocompatibility, and tenability in the body. This article used the protein blends of wild tussah silk (Antheraea pernyi) and domestic mulberry silk (Bombyx mori) as an example to provide useful protocols regarding these topics, including how to predict protein-protein interactions by computational methods, how to produce protein alloy solutions, how to verify alloy systems by thermal analysis, and how to fabricate variable alloy materials including optical materials with diffraction gratings, electric materials with circuits coatings, and pharmaceutical materials for drug release and delivery. These methods can provide important information for designing the next generation multifunctional biomaterials based on different protein alloys.

Introduction

Nature has created strategies to generate tunable and multifunctional biological matrixes using a limited number of structural proteins. For example, elastins and collagens are always used together in vivo to provide the adjustable strengths and functions required for specific tissues^1,2. The key to this strategy is the blending. Blending involves mixing proteins with specific ratios and is a technological approach to generate simple material systems with tunable and varied properties^3-5. Compared with synthetic engineering strategies^6,7, blending can also improve material uniformity and the ability to process the material due....

Protocol

1. Prediction of Protein Interactions

1. Bioinfomatics Analysis of Protein Molecules
   1. Visit the National Center for Biotechnology Information website (www.ncbi.nlm.nih.gov/protein/), and search the protein names that will be used for the alloy study. Note: For this example, two proteins were used: protein A, which is the wild tussah silk fibroin, and protein B, which is the domestic mulberry silk fibroin. For protein A, the amino acid sequences can be found in “fibroin [Antheraea pernyi] GenBank: AAC32606.1” (Antheraea pernyi is the Chinese (Oak) Tussah Moth). For protein B, the amino acid sequences can be found in “....

Results

Typical protein-protein interactions (e.g., between protein A and protein B) could contain charge-charge (electrostatic) attractions, hydrogen bonding formation, hydrophobic-hydrophilic interactions, as well as dipole, solvent, counter ion, and entropic effects between the specific domains of the two proteins (Figure 2)³. Therefore, fundamentally, we can predict the effects of these interactions by computational simulations.

Discussion

One of the most critical procedures in producing “alloy” protein system is to verify the miscibility of the blended proteins. Otherwise, it is only an immiscible protein mixture or protein composite system without stable and tunable properties. An experimental thermal analysis method can be used for this purpose and to confirm their alloy properties. Protein-protein interactions can be viewed according to Flory-Huggins’s lattice model⁴⁸ as interactions between the “solvent” (the p.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Q100 Differential Scanning Calorimeters (DSC)	TA Instruments, New Castle, DE, USA	N/A	You can use any type of DSC with a software to calculate the heat capacity.
SS30T Vacuum Sputtering System	T-M Vacuum Products, Inc., Cinnaminson, NJ, USA	N/A	With custom built parts; you can use any type of sputtering system to coat.
VWR 1415M Vacuum Oven	VWR International, Bridgeport, NJ, USA	N/A	You can use any type of vacuum oven to physically crosslink the samples.