Developing gold cellulose nanofibril material for E. coli detection

In this thesis, a method for the detection of Escherichia coli (E. coli) bacteria was developed using Raman techniques and Raman mapping methods. Firstly, gold nanorod particles were synthesized and subsequently surface functionalized with a strengthened DTNB (5,5-dithio-bis-(2-nitrobenzoic acid)) molecule which is a tagging molecule for surface enhanced Raman spectroscopy (SERS). They were then modified by interacting with antibodies specific to E. coli bacteria. Afterwards, into a cellulose nanofibril solution, Gold (III) chloride solution (HAuCl4) was added and was allowed to interact at a high temperature. By the end of the interaction period, the gold solution had become nano-sized. This solution was dried to remove the water content, resulting in a paper-like gold cellulose nanofibril hybrid surface. The resulting surface was modified by interacting with antibodies specific to E. coli. Modified gold cellulose nanofibril surfaces were interacted with different concentrations of E. coli solutions and E. coli bacteria were attached to the surface. E. coli bound gold cellulose nanofibril surfaces were interacted with gold nanorod and SERS measurements were taken. The limit of detection was determined as 2 cfu/mL bacteria. Analysis period; the time of interaction between the bacteria and the modified gold cellulose nanofibril surface was 30 minutes and the modified gold nanorod particle interaction time with bacteria attached to the modified surface was 30 minutes, resulting in the total interaction time being 1 hour. By using the Raman mapping method of the developed technique, the distribution density of the target molecule (DTNB) on the surface was shown visually and subsequently the results were found to be supported. Finally, this newly developed determination method was first tested on lettuce as a biological sample. It has been shown that the method developed within the scope of the thesis can detect E. coli bacteria at low concentrations.