Using the Color Change Characteristics of a Polydiacetylene Embedded Polyurethane Nanoweb to Detect the Presence of Escherichia coli (E. coli).
LEE, JUNG SOON
Polydiacetylene(PDA) is a conjugated polymer that undergoes changes in conductivity, absorption, its emission spectrum according to changes in the environment. It has a polymeric form of amphiphilic monomers. . In solution, the monomer, diacetylene, has the advantage of easy self-assembly in a three-dimensional structure. Unlike other conjugated polymers, PDA can be polymerized easily by photopolymerization without any other specific mechanism, such as the use of a solvent. The three-dimensional structure that is formed is polymerized between the monomer nearest to 254 nm and the triple bond. At this point, the colorless solution turns blue and has its maximum absorption wavelength at 650 nm. The color of PDA changes from blue to red (550 nm) when it is exposed to external environmental factors, such as temperature, pH, chemicals, and biomaterials (e.g., bacteria, proteins, and peptides). In addition, when the color change occurs, the characteristic fluorescence of PDA appears. Due to its color change properties, PDA has been studied extensively in the applied research areas related to biosensors.
In this study, Polyurethane (PU) nanofibers with different ratio of embedded contents were fabricated by using PDA, which has colorimetric characteristics and can be used as a sensor material. We used PDA to investigate whether nanofibers can detect E. coli based on color change.
The spinning solution of nanofibers was made by adjusting the ratio of PU and 10,14-(PCDA) from 1:4 to 1:6 to make a 12 wt. % spinning solution. The manufacturing conditions of the nanoweb were fixed at radial a distance of 15 cm, an applied voltage of 12 kV, and a fluid velocity of 0.6 ml/h to manufacture the nanofibers. The PCDA/PU nanoweb was photopolymerized via irradiation with UV light.
In the evaluation of the nanoweb’s ability to detect bacteria, the culture plates were prepared with E.coli in an agar medium in contact with a two-layer nanoweb on the medium, and they were incubated for 12 hr. at 37 ℃. After the blue PDA/PU nanoweb was exposed to the E.coli plate, it turned red immediately after exposure. In addition, in order to investigate whether the bacteria had permeated the nanoweb, we examined the color change of the inner side on the second layer of the two-layer nanoweb. We found that the nanoweb was still blue, so it was apparent that the bacteria had not permeated the nanoweb.
In conclusion, the colorimetric change from blue to red was observed when the nanoweb was exposed directly to E. coli, thereby detecting the presence of the bacteria. We also found that the bacteria were not transmitted to other layers on the nanoweb. Thus, PDA-containing nanofibers can be used for protective clothing, medical textile products, and respiratory protective masks due to their ability to detect bacteria by a change in color and their ability to inhibit the bacteria from moving between the layers of the fabric.s