Bacterial Receiver Prototype for Molecular Communication Using Rhamnose Operon in a Microfluidic Environment.

Bacterial populations are promising candidates for the development of the receiver and transmitter nanomachines for molecular communication (MC). A bacterial receiver is required to uptake the information molecules and produce the detectable molecules following a regulation mechanism. We have constructed a novel bacterial MC receiver using an inducible bacterial L-rhamnose-regulating operon. The proposed bacterial receiver produces green fluorescent protein (GFP) in response to the L-rhamnose information molecules following a quite fast regulation mechanism. To fabricate the receiver, the bacterial population has been transformed using a plasmid harboring L-rhamnose operon genes and gene expressing GFP in a microfluidic environment. We mathematically model the reception process of information molecules and characterize the model parameters by comparing the simulation results of the model in the employed microfluidic environment and the data obtained from the experimental setup. Based on the experimental results, the receiver is able to switch between different low and high concentrations. This work paves the way for the fabrication and modeling of any bacterial operon-based receiver with any proteins rather than GFP. Further, our experimental results indicate that the proposed bacterial receiver has a faster response to information molecules compared to the previous bacterial receiver based on the quorum sensing (QS) process.

Fabrication of sensitive glutamate biosensor based on vertically aligned CNT nanoelectrode array and investigating the effect of CNTs density on the electrode performance.

In this report, the fabrication of vertically aligned carbon nanotube nanoelectrode array (VACNT-NEA) by photolithography method is presented. Electrochemical impedance spectroscopy as well as cyclic voltammetry was performed to characterize the arrays with respect to different diffusion regimes. The fabricated array illustrated sigmoidal cyclic voltammogram with steady state current dominated by radial diffusion. The fabricated VACNT-NEA and high density VACNTs were employed as electrochemical glutamate biosensors. Glutamate dehydrogenase is covalently attached to the tip of CNTs. The voltammetric biosensor, based on high density VACNTs, exhibits a sensitivity of 0.976 mA mM(-1) cm(-2) in the range of 0.1-20 µM and 0.182 mA mM(-1) cm(-2) in the range of 20-300 µM glutamate with a low detection limit of 57 nM. Using the fabricated VACNT-NEA, the sensitivity increases approximately to a value of 2.2 Am M(-1) cm(-2) in the range of 0.01 to 20 µM and to 0.1 A mM(-1) cm(-2) in the range of 20-300 µM glutamate. Using this electrode, a record of low detection limit of 10 nM was achieved for glutamate. The results prove the efficacy of the fabricated NEA for low cost and highly sensitive enzymatic biosensor with high sensitivity well suited for voltammetric detection of a wide range of clinically important biomarkers.

Mediator-less highly sensitive voltammetric detection of glutamate using glutamate dehydrogenase/vertically aligned CNTs grown on silicon substrate.

A sensitive glutamate biosensor is prepared based on glutamate dehydrogenase/vertically aligned carbon nanotubes (GLDH, VACNTs). Vertically aligned carbon nanotubes were grown on a silicon substrate by direct current plasma enhanced chemical vapor deposition (DC-PECVD) method. The electrochemical behavior of the synthesized VACNTs was investigated by cyclic voltammetry and electrochemical impedance spectroscopic methods. Glutamate dehydrogenase covalently attached on tip of VACNTs. The electrochemical performance of the electrode for detection of glutamate was investigated by cyclic and differential pulse voltammetry. Differential pulse voltammetric determinations of glutamate are performed in mediator-less condition and also, in the presence of 1 and 5 µM thionine as electron mediator. The linear calibration curve of the concentration of glutamate versus peak current is investigated in a wide range of 0.1-500 µM. The mediator-less biosensor has a low detection limit of 57 nM and two linear ranges of 0.1-20 µM with a sensitivity of 0.976 mA mM(-1) cm(-2) and 20-300 µM with a sensitivity of 0.182 mA mM(-1) cm(-2). In the presence of 1 µM thionine as an electron mediator, the prepared biosensor shows a low detection limit of 68 nM and two linear ranges of 0.1-20 with a calibration sensitivity of 1.17 mA mM(-1) cm(-2) and 20-500 µM with a sensitivity of 0.153 mA mM(-1) cm(-2). The effects of the other biological compounds on the voltammetric behavior of the prepared biosensor and its response stability are investigated. The results are demonstrated that the GLDH/VACNTs electrode even without electron mediator is a suitable basic electrode for detection of glutamate.

Biodesulfurization of dibenzothiophene by a newly isolated Rhodococcus erythropolis strain.

A new dibenzothiophene (DBT) desulfurizing bacterium was isolated from oil-contaminated soils in Iran. HPLC analysis and PCR-based detection of the presence of the DBT desulfurization genes (dszA, dszB and dszC) indicate that this strain converts DBT to 2-hydroxybiphenyl (2-HBP) via the 4S pathway. The strain, identified as Rhodococcus erythropolis SHT87, can utilize DBT, dibenzothiophene sulfone, thiophene, 2-methylthiophene and dimethylsulfoxide as a sole sulfur source for growth at 30 degrees C. The maximum specific desulfurization activity of strain SHT87 resting cells in aqueous and biphasic organic-aqueous systems at 30 degrees C was determined to be 0.36 and 0.47 micromol 2-HBP min(-1) (gdrycell)(-1), respectively. Three mM DBT was completely metabolized by SHT87 resting cells in the aqueous and biphasic systems within 10h. The rate and the extent of the desulfurization reaction by strain SHT87 suggest that this strain can be used for the biodesulfurization of diesel oils.