Search Results (2)

The performance of a biosensor is associated with the properties of an immobilization layer on a sensor chip. In this study, gold sensor chips were modified with two different immobilization layers, polytyramine film and 6-mercaptohexanol self-assembled monolayer. The physical, electrochemical and analytical properties of polytyramine film and mercaptohexanol self-assembled monolayer modified gold sensor chips were studied and compared. The study was conducted using atomic force microscopy, cyclic voltammetry and a capacitive DNA-sensor system (CapSenze™ Biosystem). The results obtained by atomic force microscopy and cyclic voltammetry indicate that polytyramine film on the sensor chip surface possesses better insulating properties and provides more spaces for the immobilization of the capture probe than a mercaptohexanol self-assembled monolayer. A capacitive DNA sensor hosting a polytyramine single-stranded DNA-modified sensor chip displayed higher sensitivity and larger signal amplitude than that of a mercaptohexanol single-stranded DNA-modified sensor chip. The linearity responses for polytyramine single-stranded DNA- and mercaptohexanol single-stranded DNA-modified sensor chips were obtained at log concentration ranges, equivalent to 10⁻¹² to 10⁻⁸ M and 10⁻¹⁰ to 10⁻⁸ M, with detection limits of 4.0 × 10⁻¹³ M and 7.0 × 10⁻¹¹ M of target complementary single-stranded DNA, respectively. Mercaptohexanol single-stranded DNA- and polytyramine single-stranded DNA-modified sensor chips exhibited a notable selectivity at an elevated hybridization temperature of 50 °C, albeit the signal amplitudes due to the hybridization of the target complementary single-stranded DNA were reduced by almost 20% and less than 5%, respectively. Full article

A sensitive and reliable potentiometric biosensor for determination of penicillin has been developed by exploiting the self-limiting growth of the non-conducting polymer, polytyramine. Optimum polytyramine-penicillinase (PTy-PNCnase) films for potentiometric detection of penicillin were accomplished with monomer solutions which contained 0.03 M tyramine, 37 U/mL penicillinase, 0.01 M KNO₃,and 3 mM penicillin with an applied current density of 0.8 mA/cm² and an electropolymerisation time of 40 seconds. The potentiometric biosensor gave a linear concentration range of 3–283 µM for penicillin and achieved a minimum detectable concentration of 0.3 µM. The biosensor was successfully utilized for the detection of Amoxycillin and gave an average percentage recovery of 102 ± 6%. Satisfactory recoveries of penicillin G were also achieved in milk samples with the potentiometric biosensor when concentrations are ≥20 ppm. Full article