Servizio Comunitario di Informazione in materia di Ricerca e Sviluppo - CORDIS

Final Report Summary - MOEBIUS (Multifunctional Organic-inorganic Elements with Biosensing re-Usability)

In the second phase of MOEBIUS project the target enzymes: glucose oxidase (GOx), horseradish peroxidase (HRP), 3‐α‐hydroxyl‐steroid dehydrogenase, bile acid sulfate sulfatase (BBS), β‐hydroxysteroid dehydrogenase (βHSD), purine nucleoside phosphorylase (PNP), xanthine oxidase (XOD) and NADH oxidase (NHO) have been immobilized onto oxide surfaces previously functionalized with active dyad molecules and embedded into the nano-channels of the ion-track membranes.

The obtained structures have been tested in a prototype bio-diagnostics instruments for detection of human liver diseases and their operational parameters under different photo-excitation conditions have been determined. The sensing mechanisms were assessed through the interplay between the first-principles calculations of the organic - inorganic interfaces and conductometric responses of the biosensors.

Because porphyrins are closely packed and near the surface, emerging van der Waals (vdW) interactions are examined using Grimme’s D2 method. The dispersion correction stabilizes the porphyrins in tilted lamellar structures. The molecular dynamics (MD) simulations of such interface demonstrated that variations of interatomic distances (3-5%) have essential effect on the strength of coupling / decoupling between the LUMO or LUMO + 1 of the porphyrine and the oxide conduction band that finally affect the electron transfer. Accounting the surface vibrations and natural transition orbital analysis for ZnO– porphyrine system at “close-to-surface” conformation shows that after photon absorbance, an electron from the porphyrine molecule has higher rate of injection into the ZnO surface. The calculations indicate that electron injection occurs efficiently if the LUMO level of porphyrine dye is located sufficiently far above the bottom of the conduction band at the most favorable receptor-to-surface conformations.

The spin Hamiltonian parameters of intrinsic defects in SnO2 are examined through the first-principles electronic structure calculations based on density functional theory. The electron paramagnetic resonance signals with g-tensor value in the range of 1.89–1.94 were found for tin vacancy (VSn) and its complex with oxygen vacancy (VSn-VO). The calculated parameters are consistent with experimental observations. Within the second coordination shell of the tin vacancy, the VO may stabilize in the singly ionized charge state, which is otherwise considered to be unstable for isolated oxygen vacancy in the bulk of SnO2. The obtained results have a positive impact on the explanation of the high-temperature ferromagnetism observed in oxide nanowires and will be used for creation of the magnetic biosensor prototypes based on the developed ion-track nanostructures.

For the test purposes the construction of the total bile acid and adenosine deaminase sensors utilizes two polymer membrane structures that are combined with each other so that the electrolyte is spread over three compartments. The final implementation of the TEMPOS structures is performed on the microfabricated substrates with sizes down to a few mm only, which allow array strategy for a sequential enzymatic analysis. The test measurements of the oxidation current over time demonstrate that constructed sensors are capable of distinguishing varying μmol levels of NADH and hydrogen peroxide generated by changes in bile acid and adenosine deaminase concentrations.

The developed device can be used to detect physiologically relevant biomarker concentrations between 5µM and 1M. The sensitive catalytic sensor can be made re-usable due to the production of diffusible products from the oxidative biomolecular recognition event. We have demonstrated both the simplicity with which this sensor can be produced and the stability of the enzyme embedded in the nanopores. Beyond the identification of key liver biomarkers, this work will be further expanded for the development of a growing list of diseases that can be identified with the developed platform sensor technology.

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