Team:NWU-CHINA-A/Design
Introduction
We want to design a new type of antibacterial adhesive bandage, which has good biocompatibility and antibacterial effect. Our ideal product can reduce the risk of creating antibiotic resistance and it will not cause pollution to environment. Therefore, we chose AMP(antimicrobial peptide) as the antimicrobial agent of our adhesive bandage and PHA as its carrier. At the same time, in order to add AMP to PHA material better, we fused PhaP(PHA Binding Protein) with AMP as a bridge between antimicrobial peptide and PHA material.
And we used bacterial mucin to connect the central island made of PHA and outer non-woven. Finally, in order to protect the safety of our laboratory, we used a glucose-based starvation suicide switch.
AMP
Injuries are inevitable in daily life, and we are vulnerable to the threat of infection after injury because of ubiquitous bacteria. Antibiotics have been widely used to treat infections for a long time, but there is always a concern that excessive use of antibiotics will cause antibiotic resistance and even lead to superbugs. Therefore, many people turn their attention to non-antibiotic antibacterial substances. AMPs(antimicrobial peptides) are most promising because of their broad-spectrum antimicrobial activity and low tendency to induce drug resistance. Normally, AMP is a kind of cationic peptide, which can insert into the plasma membrane with negatively charge by electrostatic interaction, causing the cell membrane to perforate or collapse and kill bacteria.
PHA
For the sake of good user experience and environmental protection, we hope to use biocompatible and biodegradable material to make our adhesive bandage. PHA(polyhydroxyalkanoate) is a kind of intracellular polyester, which can be synthesized by a variety of bacteria, and has these properties we desired. Moreover, there have been many studies on PHA material and its related binding protein, PhaP. So, it is the best choice for our project.
PhaP
In order to organically combine PHA and AMP to form our adhesive bandage, we fused PhaP and AMP to express them first. Then we used the natural binding characteristics of PhaP and PHA material to bind them. PhaP(polyhydroxyalkanoate (PHA)-granule-associated protein) is an amphiphilic protein, which is the main protein attached to the surface of PHA particles, containing a hydrophobic particle binding domain and a hydrophilic domain. So PhaP-tagged protein can interact with various types of hydrophobic surfaces and are effective anchors for surface functionalization of hydrophobic polymers. It is the bridge of our adhesive bandage.
PhaP-Linker-AMP
Based on the literature and experimental principles, we constructed the following gene circuit. Between PhaP and AMP, we add a (Gly4Ser) 2 flexible connector to separate PhaP from AMP so that they can fold correctly to play their role.
Gene circuit of the co-expression system
Schematic of expression product
PHA-PhaP-structure
Bacterial Mucin
PHA is the material for making the central island of adhesive bandage, which has antibacterial activity and plays a major bacteriostatic role. The outer layer of the adhesive bandage is non-woven fabric. In order to connect the non-woven fabric with PHA, we chose the bacterial mucin from 2019 GreatBay SCIE team under the suggestion of Beijing_4ELEVEN team. Bacterial mucin is consists of two types of proteins, adhesion protein and cohesive protein. Cohesion protein can be self-assembled into fibers, while adhesion protein is responsible for interfacial bonding. The combination of two types proteins forms the basis of bioadhesives.
Suicide Switch
In order to prevent the engineering bacteria constructed in our laboratory from escaping to the natural environment and causing genetic contamination, we used the glucose starvation suicide switch that SZPT-CHINA team used in 2019 at the suggestion of SZPT-CHINA team. When glucose is deficient in the environment, glucose starvation induces the overexpression of autolysin gene in the T-α crp promoter(acmA).
Suicide Switch Scheme