**3. Application of the electropolymerized film in analytical areas**

Significant advances in electropolymerization areas during the 1990's are certain to facilitate the application of the sensors to different analytical areas. To date, electropolymerized films have been widely used for clinical and environmental detection purpose.

Non-conductive polymers obtained from amino acid or their derivates have also obtained particular interest because they bears specific groups which can interact with some electroactive species through the formation of covalent bonds between either the amino and aldehyde or amino and carboxyl groups. We have used cyclic voltammetric method to form the L-cysteine modified electrode for the detection of sinomenine [10] , dopamine [11], terbinafine [12] and adenine [13]. Cystein was electropolymerized on a glassy carbon electrode in 0.04 M HCl solution in the scan range from -1.20 to 2.60 V at the scan rate of 100

Fig. 2. The process for the preparing of the Phenol film by electrochemical method.

 polyphenol polyphenylendiamine

**3. Application of the electropolymerized film in analytical areas** 

have been widely used for clinical and environmental detection purpose.

Fig. 3. Structures of some non-conductive polymerfilms

overoxidized polypyrrole

Significant advances in electropolymerization areas during the 1990's are certain to facilitate the application of the sensors to different analytical areas. To date, electropolymerized films

Fig. 3 illustrated the structures of some of the non-conductive films obtained by electropolymerization method. They included the already discussed polyphenol, polymers of phenylendiamines and the overoxidized polypyrrole (PPy). These polymers can be used as a novel support matrix for the immobilization of biomolecules to construct different electrochemical sensors. We would discuss the preparation and application of these films in

mV/s [13].

the following section.

### **3.1 Electropolymerized films for clinical monitoring**

Electrochemical sensors in clinical assay was developed from 1962 by Clark and Lyons who used the glucose oxidase (GOx) enzyme to construct an amperometric electrode for dissolved oxygen detection [14]. From that time, the application of electrochemical sensors to determine the concentration of substances and other parameters of biological interest has represented a rapidly expanding field of instrument. The electrochemical sensors have been widely used in clinical analysis because of their high sensitivity and selectivity, portable field-based size, rapid response time and low-cost. Some of these sensor devices have been routinely used in clinical, industrial, environmental, and agricultural areas. Many works and reviews related on this area have been reported. Lakshmi D et al has reviewed the application of electrochemical sensors for uric acid detection in mixed and clinical samples[15]. Ronkainen et al reviewed the application of electrochemical biosensors from two points: biocatalyst and affinity [16].

Since the original work reported by Diaz et al. [17], the films prepared by electropolymreization method have attracted considerable interest due to their versatility. Polymers have gain considerable interest in the clinical analysis area because of their unique and biochemical properties. In 1992, Davies et al have extensively reviewed the application of the polymer membranes in clinical sensor application [18]. In this work, the authors were concerned with the relationship between the polymer design and the proposed application. They highlighted the permeability, permselectivity and transmembrane potential of the polymer membranes and the role of polymer membranes as matrices for the immobilization of reactive chemical and biological agents. Cosnier reviewed the application of the electropolymerized films on the construction of affinity sensor[19]. He compared the different strategies for the immobilization of biomolecules on electropolymerized films to construct affinity sensors which can be used as clinical sensors. Table 1 [20-52] summarized the numerous of recent applications in clinical areas based on the electropolymerized films. The information on the analytes, the polymer films, and the characters of the sensors has been listed**.** 

Non-conductive polymer from polyphenylenediamines has been used as a matrix for the entrapment of enzymes. Glucose oxidase has been caged into the microtubule structures of polycarbonate membrane by using poly (1, 3- phenylenediamine) to fill the pores. The sensitivity of the sensor increased 60 times [23]. Different techniques for the electropolymerization of 1,2-, 1,3- and 1,4-phenylenediamine, such as cyclic voltammetry and chronoamperometry, were compared by Currulli et al [53]. When heparin was coimmobilized with glucose oxidase during the electropolymerization of a non-conductive poly (1,2- phenylenediamine) film, an implantable glucose biosensor could be constructed [54]. This sensor could prevent the fibrin formation and clotting when the glucose sensor was exposed to blood.

Phenol and its derivative have also been widely used for clinical analysis. The electropolymerization of phenol derivatives is similar to that of phenol. We reported the polymerization of the acid chrome blue K on a glassy carbon electrode by cyclic viltammetric method in 0.05 M pH 7.0 phosphate buffer solution in the potential range from -0.4 V to 1.5 V at the scan range of 100 mV/s by 25 cycles [28]. This film can be used to separate the electrochemical response of dopamine (DA), ascorbic acid (AA) and uric acid (UA). Under the optimum conditions, the calibration curves for DA, AA and UA were obtained in the range of 1.0–200.0, 50.0–1000.0 and 1.0–120.0μM, respectively. Both poly

Electrochemical Sensors Based on Electropolymerized Films 193

(3-aminophenol) film [30] and poly (2-aminophenol) [31] film have been used for the selectively detection of uric acid. The poly (2-aminophenol) film was electrochemically prepared on Pt electrodes at a constant potential of 0.3 V from a deoxygenated aqueous solution of monomer dissolved in 0.1 M KCl. This film modified electrode allows the penetration of large amounts of uric acid while blocking the electrochemical activity of

Electrochemical sensors play very important roles in the protection of our environment. They can monitor the pollutant on-site and address some other environmental needs. Several electrochemical devices, such as pH- or oxygen electrodes based on the polymerized films, have been used routinely for years in environmental analysis. The electropolymerized pyrrole [55,56], aniline, thiophene, benzene derivatives and others [57,58] have been used for the preparation of pH chemical sensors. Herlem, G et al prepared the polyglycine-like thin film on platinum electrode by anodic oxidation. The film can be used as a pH sensor in the pH range 2-12 because of the proton affinity towards amino groups of polyglycine [59].

Analyte monomer linearity or detection limit Ref

ammonia pyrrole 10- 200 µM 69 Ca2+ melatonin 6.210-7- 1.010-4 M 70

methyl-parathion para-phenylenediamine 0.01 to 10 mg/L 75

chloride 3-octylthiophene 10-8 – 10-1 M 77 4-nitrophenol carmine 50 nM – 10µM 78

2-mercaptobenzothiazole 1.0-160.0 nM 62 2,6-diaminopyridine 10 µ M -0. 1 M 63 3-methylthiophene 1.4 µg/ L 64

carbon nanotube-anillin 0.2µM -3.1 mM 66

functionalized thiadiazole 0.05 -16µM 68

carbon nanotubes 0.1 - 20 µM 71

ethylenebis(salicylideneiminato)) 4.0 -69µM 73

pyrrole 50 nM- 0.01 M 72

aniline 0.006-5 mM 74

0.1-2.5 mM 76

ionic liquid 0.5-67.9 µ M 65

pyrrole 10µM -1 mM 65

ascorbic acid in the potential region examined.

Hg2+

nitrite

Cu2+

sulfite

para-nitrophenol

microbial

**3.2 Electropolymerized film for environmental monitoring** 

methylene blue-carbon nanotubes-

2-aminothiazole)-multi-walled

copper salen (salen=N,N'-

4-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)benzenamine (SNS-NH2) polymer

Table 2. Examples of electropolymerized films for environmental analysis


Table 1. Examples of electropolymerized films for clinical analysis

analyte monomer linearity or detection

thioaniline functionalized gold

poly(1,2-diaminobenzene) as the template for the electropolymerization of polyaniline

pyrrole

gold nanoparticles/p-aminobenzoic

silver nanoparticles/3-(3-pyridyl) acrylic

m-phenylenediamine, 2 3 diaminonaphthalene, and 5-amino-1-naphthol polymers

leptin Au-pyrrole propylic acid-pyrrole

Myeloperoxidase o-phenylenediamine/multi-wall carbon

<sup>17</sup>- estradiol 3,4-ethylenedioxylthiopene/gold

interleukin 5 pyrrole-pyrrolepropylic acid-gold

Table 1. Examples of electropolymerized films for clinical analysis

uric acid 3-aminophenol 30

Human IgG pyrrole-3-carboxylic acid 40 urea styrene sulphonate-aniline 0-75 mM 41 hemoglobin pyrrole-gold nanoparticles 60-180 µg/mL 42

cholesterol 2-mercaptobenzimidazole 5-30µM 49

toluidine blue O 0.1-1.2 mM 20 preoxidized catecholamines 0.3 μM 21

nanoparticle 0-200 mM 22 1,3-phenylenediamine 0.25 μM – 18 mM 23 thioaniline-modified glucose oxidase 24

N-methylpyrrole 0.1- 10 μM 25 aniline/gold nanoparticles 3-115 μM 26 1-aminoanthracene 0.56-100 μM 27 acid chrome blue K 1.0 – 200.0 μM 28

2-aminophenol 0.5 – 0.9 mM 31

ferrocene-functionalized pyrrole 0.1-200 nM 35

acid/carbon nanotubes 1.0 fmol -50 nM 36 gold nanoparticles/L-lysine 0.1 - 10 fmol 37

acid/carbon nanotubes 9.0 fmol-9.0 nM 38

nanotubes -ionic liquid/gold nanoparticles 0.25-350 ng/mL 43

eugenol or o-phenylenediamine 45 poly(toluidine blue) 0.18-86µM 46

meldola blue/chitosan 10 nM-600µM 48

phenothiazine 70 nM 50 pyronin B 1.0 - 500 µM 51

nanocomposite 10 fg/mL 52

nanocomposite 10-100000 ng/mL 39

Nanocomposite <sup>44</sup>

glucose

dopamine

prostate specific antigen

DNA

nitric oxide

nicotinamide adenine dinucleotide limit Ref

1-100 pg/mL 29

From nM to µM 47

 32 3.7-370 nM 33 0.16 -3.5 fmol 34 (3-aminophenol) film [30] and poly (2-aminophenol) [31] film have been used for the selectively detection of uric acid. The poly (2-aminophenol) film was electrochemically prepared on Pt electrodes at a constant potential of 0.3 V from a deoxygenated aqueous solution of monomer dissolved in 0.1 M KCl. This film modified electrode allows the penetration of large amounts of uric acid while blocking the electrochemical activity of ascorbic acid in the potential region examined.
