Biosensors & Bioelectronics

A Microbial Fuel Cell (MFC) based biosensor for the determination of Assimilable Organic Carbon (AOC) in seawater was developed by establishing an anodophilic marine biofilm on the surface of an electrode poised at +250 mV (vs Ag/AgCl) rather than the traditionally used potentials of about -300 mV. A linear correlation (R²>0.99) between electrochemical signals (peak current) and acetate concentration ranging 10 to 55 μM was achieved.Using the positive anodic potential enabled the rapid establishment of the electrochemically active anodophilic biomass within a period of less than 8 days, a higher sensitivity (0.017 mA/μM acetate added) and a lower detection limit (2.5 μM acetate, 0.16 mg O₂/L of Biological Oxygen Demand (BOD)) compared to the negative anodic potential. Further, it was shown that this bio-electrochemical AOC sensor could tolerate the presence of low concentrations of dissolved oxygen. The established potentiostat controlled MFC biosensor could be used for the purpose of online water quality monitoring for seawater desalination plants prone to biofouling of RO membranes.

Context: With regard to two-dimensional (2D) cell cultures in flat dishes, most of the three-dimensional (3D) cell cultures have advantages and gain importance in life sciences. But, their higher complexity requires adaptation of existing methods or different measurement systems in order to achieve accurate results. Bio-Impedance spectroscopy (Bio-IS) is a label- free and non-destructive method that is considered for analysis of 3D cell models.

Purpose: We design a new Bio-IS measurement system for a 3D liver cell model to assess cell seeding and drug effects.

Experiment Methods: We measured reflection coefficient S11 with differently (disc- and needle-like) shaped electrodes, which are in defined contact with the 3D liver cell model, metabolic activity (MTT test), and cytotoxicity (LDH assay). Results: We demonstrate that reflection coefficient S11 may be utilized to assess the 3D liver cell system in the frequency range of β-dispersion at 73 MHz only by means of the needle-like electrodes. This enables a reliable label-free and non-destructive determination of cell seeding and drug effects in the 3D liver cell culture model. The physical results have been verified by destructive biochemical methods (LDH and MTT assay).

Conclusion: Our Bio-IS system for 3D liver cell models using needle-like electrodes enables label-ree and nondestructive determination of cell seeding and drug effects.

We developed a simple procedure for the complete regeneration of silane-grafted gold surface. This method allowed the reuse of the regenerated gold chip for custom refunctionalization. In addition, we performed highly reproducible immunoassays using these chips over several cycles. The developed procedure was optimized and comprised of consecutive treatments of functionalized Au chip with 12 M HCl for 10 min and 29 W oxygen (O2)- plasma for 5 min. Monitoring and surface characterization of the developed methodology was performed with ellipsometry and Rutherford back scattering. The developed procedure was demonstrated on SPR-based Human Fetuin A (HFA) immunoassay, where the amino groups of APTES-functionalized Au chip were cross linked to the carboxyl groups of anti-HFA antibody using 1-ethyl-3-[3-dimethylaminopropyl] carbodiimide hydrochloride and sulfo- N-hydroxy succinimide. The APTES-functionalization, anti-HFA antibody immobilization and HFA binding on the regenerated SPR Au chip were highly reproducible over 40 HFA immunoassay cycles.

We have developed a novel, rapid, highly sensitive biosensor protocol for diagnosis and characterization of influenza viruses in the early stage of the epidemic. Using Surface-Enhanced Raman Scattering (SERS) technique and nitrocellulose membrane, detection limit as low as 30 ng/mL was achieved with high selectivity to different subtypes of influenza virus tested. Moreover, the SERS measurement can be completed in less than 2 h, thus making the protocol useful in early diagnosis and impediment of propagation of potential influenza pandemic.