Strong and elastic, yet degradable: protein-based bioplastics

Date:
February 11, 2022
Source:
Wiley
Summary:
More than eight million tons of plastic end up in the oceans
every year - - a serious danger for the environment and
health. Biodegradable bioplastics could provide an alternative. A
research team has now introduced a new method for the production of
protein-based plastics that are easily processable, biodegradable,
and biocompatible, as well as having favorable mechanical
properties.



FULL STORY ==========================================================================
More than eight million tons of plastic end up in the oceans every year --
a serious danger for the environment and health. Biodegradable bioplastics could provide an alternative. In the journal Angewandte Chemie, a research
team has now introduced a new method for the production of protein-based plastics that are easily processable, biodegradable, and biocompatible,
as well as having favorable mechanical properties.


========================================================================== Whether as packaging or toys, mulch films or cars, plastics based on petrochemicals are ubiquitous -- demand is rising, and so are the piles of garbage. Bioplastics based on natural materials like starch, or synthetic biomaterials like polylactic acid, have exhibited inadequate durability, biocompatibility, and/or biodegradability in most cases. In addition,
they often require complex, energy-intensive processing methods and
toxic chemicals.

A team led by Jingjing Li and Yawei Liu (Chinese Academy of Sciences, Changchun, China), as well as Bo Wei (First Medical Center of PLA General Hospital) have now introduced novel bioplastics with properties that can
be tailored according to need. To do this they developed two lysine-rich proteins and produced them in bacterial cultures: "ELP" is a polypeptide similar to the connective tissue protein elastin. It does not have defined folding, which leads to toughness and elasticity. "SRT" consists of ELP
plus crystalline segments of a squid protein with a b-sheet structure.

ELP (or SRT) is crosslinked with a polyethylene glycol (PEG) derivative
by way of its lysine amino side-groups. (PEG is used in pharmaceuticals,
among other things.) If the crosslinking occurs in water, the material
can then simply be dried in a mold. The result is a tough, transparent, solvent-resistant bioplastic. Its mechanical properties can be varied
by changing the proportion of PEG. This allows for the production of bioplastics with high mechanical strength at room temperature in any
shape desired, and without toxic chemicals or complex processing steps
such as liquefaction, extrusion, or blow molding.

Their breaking stress exceeds those of many commercial plastics. One
problem left is that they swell in water.

If ELP is crosslinked in a water/glycerol solution, the material gels
into soft, elastic bioplastics. The team also used wet spinning to
produce biofibers that are as strong as some biotechnological spider
silks. The natural enzyme elastase completely degrades all of the new protein-based bioplastics.

It is conceivable to make toys with this new, nontoxic bioplastic that
can be dyed with food coloring. This material may also be used to seal
wounds as it has hemostatic effects. Implants were completely broken
down within a few weeks.

To store information, ELP could be polymerized together with peptides that
have been programmed with codes by means of their specific amino acid sequences. The information could be read back through sequencing. This
would allow for higher information density than is possible with DNA
data storage.

========================================================================== Story Source: Materials provided by Wiley. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Juanjuan Su, Kelu Zhao, Yubin Ren, Lai Zhao, Bo Wei, Bin Liu,
Yi Zhang,
Fan Wang, Jingjing Li, Yawei Liu, Kai Liu, Hongjie
Zhang. Biosynthetic Structural Proteins with Super Plasticity,
Extraordinary Mechanical Performance, Biodegradability,
Biocompatibility and Information Storage Ability. Angewandte Chemie
International Edition, 2022; DOI: 10.1002/ anie.202117538 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220211102033.htm

--- up 9 weeks, 6 days, 7 hours, 13 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)