Development and Optimization of a Glucose Biosensor Based on Tris [ 5-amino-1 , 10-Phenanthroline ] Iron ( II ) Polymer Films

A bilayered glucose biosensor consisting of tris[5-amino-1, 10-phenanthroline]iron(II) polymer film redox mediator and a glucose oxidase layer was prepared on glassy carbon surfaces. The polymer film of the iron complex was immobilized onto the electrode using cyclic voltammetry via electropolymerization reactions, while the enzyme layer was formed using a BSA and glutaraldehyde crosslinking reaction. The biosensors gave the largest response in the pH range of 7-8 and were evaluated with respect to storage conditions of room temperature and 4C. There was no significant difference between the detection of glucose using the biosensor stored at room temperature versus one stored at 4°C and both bilayered films remained active for 20 days. The detection limit of the biosensors was found to be 0.30 mM which corresponds to a signal to noise ratio of 3:1.


Introduction
Diabetes is a metabolic world-wide disease that results in high blood sugar.The Center for Disease Control (CDC) reports that the estimated economic burden linked with prediabetes, gestational diabetes, and diagnosed diabetes cost the U.S. $322 billion in 2012.The CDC also states that cost alone in treating diabetes was $245 billion in 2014.There are numerous complications that come with diabetes including hypertension, blindness, kidney disease, and an increase risk for a stroke or heart attack.So, the need to monitor blood glucose levels for these people is very clear and necessary.Biosensors are devices that have the ability to do this.Specifically, enzyme-based biosensors are of great importance for their ability to detect important biological molecules (Shen et al. 2017;Nakabayashi et al. 1998;Chuang et al. 1997;Chi and Dong 1993;Creager and Olsen 1995;Shigehara et al. 1981;Battaglini et al. 1999;Dong et al. 1991;Janarthanan and Mottola 1998;Ohara et al. 1994;Mafatle and Nyokong 1997).Some of these biosensors are based on using oxygen as a redox mediator and then detecting the by-product hydrogen peroxide.The drawback in this design is that oxygen levels vary, causing hydrogen peroxide levels and hence analytical signals to fluctuate.Other amperometric biosensors use redox mediators that are electrostatically linked to a polymer backbone.In these latter cases, there is the possibility that the redox mediator can leach from the polymer network attached to the electrode.The process of immobilizing a redox mediator into a hydrogel requires approximately 48 hours to complete (Battaglini et al. 1999), whereas in our electrode modification process, the time is shortened to 6-8 hours, and the electrode is ready to use in one day; electropolymerization of the redox mediator described in this paper takes several minutes to complete.Preparation of a biosensor using ferrocene and an enzyme in a hydrogel matrix is complex and requires more than eight hours to cure the film under vacuum (Chuang, et al, 1997).The goal in this research was to develop a process in designing a biosensor within several hours as opposed to several days.The entire immobilization processs takes less than 10 minutes and the electrode is ready to use the same day.In addition, we show that the electrode can be stored in room temperature or in a cold environment and the biosensor still maintains activity over a 20-day time frame; these biosensors do not need to a prepared each day, but are designed for long-term use.
The glucose biosensor developed in this research is based on a multi-layered stepwise mechanism (Emr et al, 1995).These layers consist of an enzyme layer, redox mediator, and finally the electrode surface.Immobilization of compounds onto electrode surfaces via electropolymerization is a versatile method that can produce robust polymer films consistent in thickness and electrochemical reactivity.The compound used in this research contains multiple -NH 2 groups that allow extensive crosslinking possibilities.Electroplymerization of this compound produces a three-dimensional network of active sites for reactions to occur.In this paper, the construction of the redox polymer film based on tris[5-amino-1, 10-phenanthroline]iron(II), Fe(Phen-NH 2 ) 3 (Figure 1) and an enzyme layer is examined.  .Glucose oxid wder, ≥96%

pH Study
The effect of The biosensor buffer at pH 5 2.00 to 0.00 V this relationsh in this range (

Temperatu
Two biosenso devices at diff For twenty da at their respective temperatures.A paired t-test was used to test the difference between the current response of each electrode every day they were used.Based on the paired t-test that at a 95% confidence level (n=11), there was no significant difference between the responses of the two biosensors stored at room temperature (black graph) versus 4°C (blue graph).

Conclusion
In this paper, the electrochemical behavior of a Fe(Phen NH 2 ) 3 redox polymer film in a glucose biosensor has been investigated by cyclic and hydrodynamic voltammetric techniques.Two biosensors were stored at different temperatures, one at room temperature and the other at 4ºC.Throughout 20 days of storage, both biosensors consistently detected glucose.It was observed that the biosensor performs best in pH range of 7-8 which encompasses the standard blood pH range of 7.35-7.45.The detection limit of the biosensors is 0.30 mM.Based on the studies performed, a durable and sensitive bliayered glucose biosensor can be constructed Fe(Phen NH 2 ) 3 as a redox mediator.
Figure 2 illus correspond to first cycle of e V. Hence the process contin in thickness, a complex was from 2.00 V to and reduction reduction and mechanism of Figure 9. P