A Biosensor Based on Bay Leaf (Laurus nobilis L.) Tissue Homogenate: Improvement of the Stability Characteristics by a Simple Bio-imprinted Technique

Figures & data

Figure 1.  pH dependence of the biosensors [(▪) imprinted PPO biosensor; (▴) PPO biosensor. Working conditions: Catechol concentration was injected to a final concentration of 200 µM. Sodium phosphate buffer with different pH values, 50 mM and 25 °C].

Table 1. pH stabilities of the biosensors.

	Initial activity	Incubation period (h)	Residual activity (%)
Biosensor 1^a	100	20	94
Biosensor 2^b	100	20	100

pH stabilities of the biosensors were carried out at pH 8.5, 50 mM sodium phosphate buffer.

^aThe biosensor with unmodified.

^bThe biosensor modified with thiourea.

Figure 2.  Temperature dependence of the biosensors [(▪) imprinted PPO biosensor; (▴) PPO biosensor. Working conditions: Catechol concentration was injected to a final concentration of 200 µM. Sodium phosphate buffer, 50 mM and pH 8.5].

Table 2. Thermal stabilities of biosensors.

	Initial activity	Incubation period (h)	Residual activity (%)
Biosensor 1^a	100	20	80
Biosensor 2^b	100	20	94

Thermal stabilities of the biosensors were carried out at 35°C and pH 8.5, 50mM sodium phosphate buffer. The concentration of catechol used in the experiments was 200 µM.

^aThe biosensor unmodified.

^bThe biosensor modified by thiourea.

Figure 3.  Calibration graphs of the biosensors for catechol [(▪) imprinted PPO biosensor; (▴) PPO biosensor. Working conditions: Sodium phosphate buffer pH 8.5, 50 mM and 35 °C].

Table 3. Repeatabilities of biosensors.

	Average value(µM)	n	S.D.(µM)	C.V.(%)
Biosensor 1^a	192.5	10	±9.42	4.9
Biosensor 2^b	198	10	±5.76	2.9

The concentration of catechol used in the experiments was 200 µM.

^aThe biosensor with unmodified.

^bThe biosensor modified with thiourea.

Figure 4.  Operational stabilities [(▪) imprinted PPO biosensor; (▴) PPO biosensor. Working conditions: Catechol concentration was injected to a final concentration of 200 µM. Sodium phosphate buffer pH 8.5, 50 mM and 35 °C].

Table 4. Subsrate specificities of the biosensors.

	Activity(%)
Phenolic compound	Biosensor1^a	Biosensor2^b
Catechol	100	100
Pyragallol	63.7	71.4
Caffeic acid	18.2	23.8
Phenol	9.1	14.3
Sinapinic acid	11.4	9.5
Ellagic acid	11.4	4.8
Naphtol	18.2	ND*
Ferulic acid	11.4	ND

Concentrations of substrates tested by biosensors were 200 µM.

Working conditions: sodium phosphate buffer 50 mM, pH 8.5, and T= 35°C.

^aThe biosensor with unmodified.

^bThe biosensor modified with thiourea.

*Not determined.