The authors thank Rowan University for support of this research. XH also thanks Dr. David L. Kaplan at Tufts University and the NIH P41 Tissue Engineering Resource Center (TERC) for previous technical trainings.&#160;

1.&#160;Prediction of Protein Interactions
<ol>
	<li>Bioinfomatics Analysis of Protein Molecules
	<ol>
		<li>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 &#8220;fibroin [Antheraea pernyi] Ge...

No conflicts of interest declared.

One of the most critical procedures in producing &#8220;alloy&#8221; 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&#8217;s lattice model48 as interactions between the &#8220;solvent&#8221; (the p...

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 tissues1,2. 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 properties3-5. Compared with synthetic engineering strategies6,7, blending can also improve material uniformity and the ability to process the material due to the ease of operation8-16. Therefore, designing multifunctional, biocompatible protein alloy materials is an emerging area of medical research. This technology will also provide systematic knowledge of the impact of natural protein matrices on cell and tissue functions both in vitro and in vivo10,17. By optimizing molecular interfaces between different proteins, protein-based alloy materials can encompass a range of physical functions, such as thermal stability at different temperatures, elasticity to support diverse tissues, electrical sensitivity in variable organs, and optical properties for corneal tissue regeneration3,18-27. The outcome of these studies will provide a new protein-materials platform in the field of biomedical science with direct relevance to tunable tissue repairs and disease treatments and further lead to biodegradable implant devices where their novel therapeutic and diagnostic features can be envisioned3.
Many natural structural proteins have critical physical and bioactive properties that can be exploited as candidates for the biomaterial matrixes. Silks from different worm species, keratins from hairs and wools, elastins and collagens from different tissues, and various plant proteins are some of the most common structural proteins used for designing variable protein-based materials (Figure 1)18-27. In general, these proteins can form different molecular secondary structures (e.g., beta sheets for silks, or coiled coils for keratins) due to their unique repetitive primary amino acid sequences3,28-35. These features promote the formation of self-assembled macroscopic structures with unique functions at biological interfaces prompting their utility as a treasured resource of biopolymer materials. Here, two types of structural proteins were used (protein A from wild tussah silk and protein B from domesticated mulberry silk as an example) to demonstrate the general protocols of producing various protein alloy biomaterials. The protocols demonstrated include part 1: protein interaction predictions and simulations, part 2: production of protein alloy solutions, and part 3: fabrication of protein alloy systems and for optical, electrical, and pharmaceutical applications.
<img alt="Figure 1" fo:content-width="5in" src="/files/ftp_upload/50891/50891fig1highres.jpg" width="500" /> 
Figure 1. Raw materials of various structural proteins that are commonly used in our laboratory for designing protein-based materials, including silks from different worm species, keratins from hairs and wools, elastins from different tissues, and various plant proteins.

<table border="0" cellpadding="0" cellspacing="0" width="1050">
	<tbody>
		<tr height="84">
			<td height="84" style="height:84px;width:216px;">Q100 Differential Scanning Calorimeters (DSC)</td>
			<td style="width:143px;">TA Instruments, New Castle, DE, USA 
			&#160;</td>
			<td style="width:169px;">N/A</td>
			<td style="width:523px;">You can use any type of DSC with a software to calculate the heat capacity</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:216px;">SS30T Vacuum Sputtering System&#160;</td>
			<td style="width:143px;">T-M Vacuum Products, Inc., Cinnaminson, NJ, USA</td>
			<td style="width:169px;">N/A</td>
			<td>With custom built parts; You can use any type of sputtering system to coat</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">VWR 1415M Vacuum Oven&#160;</td>
			<td style="width:143px;">VWR International, Bridgeport, NJ, USA</td>
			<td style="width:169px;">N/A</td>
			<td>You can use any type of vacuum oven to physically crosslink the samples</td>
		</tr>
	</tbody>
</table>

designing silk-silk protein alloy materials for biomedical applications

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.

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.
<p class="jove_content" fo:keep-together.within-page="al...

Watch this Scientific Journal Video about Designing Silk-silk Protein Alloy Materials for Biomedical Applications at JoVE.com

Designing Silk-silk Protein Alloy Materials for Biomedical Applications

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.

Fibrous proteins display different sequences and structures that have been used for various applications in biomedical fields such as biosensors, ...

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