The emergence of 2-dimensional (2D) materials could herald numerous advanced scientific methodologies for both fundamental and applied research. These ultrathin materials can be functionalized and, thus, have the potential to make new devices and sensors that are both highly efficient and sensitive. In addition to being mechanically robust, the 2D materials can be engineered to provide sensor architectures that further increase their inherent high surface area by creating 3D geometries using layer by layer assembly to make stacked devices that could potentially be transparent. The increased sensor surface area would deliver increased signal-to-noise and sensitivity. Here highly sensitive and selective electrochemical detection of bio-analytes using some of engineered 2D materials such as graphene nano-ribbons, fluorinated graphene, and molybdenum disulfide is presented. It is found that surface moieties, defects and surface charges in these ultra-thin layers result in enhanced electron transfer kinetics between the electrodes and biomolecules. This in turn results in an oxidation or reduction of biomolecules with a high peak current, indicating the possible uses of 2D materials for various point-of-care devices. A novel stable 3D electrode geometry has been found to have enhanced heterogeneous electron transfer properties compared to 2D electrodes and provides evidence that electrode geometry and surface area could significantly impact the performance of biosensors.

There is increased interest towards the application of carbon based nanomaterials to biosensors since these can be used to quickly detect presence of the toxins in food, agricultural and environmental systems. The accurate, faster and early detection of food toxins is presently very important for ensuring safety and shelf life of agricultural commodities resulting from food contamination. The carbon materials (CNTs) and recently discovered graphene have been predicted to be promising candidates in the development of electrochemical biosensor owing to their exceptionally large surface area and interesting electrochemical properties. We focus on some of the recent results obtained in our laboratories pertaining to the development of biosensors based on multi-walled carbon nanotubes and graphene for mycotoxin(aflatoxin ) detection.

The need for improved medical sensors based on lab-on-a-chip technologies has increased significantly because of the dramatic growth in the number of people with chronic diseases and the associated costs for their healthcare. Development and initial results of a hybrid plastic microfluidic device with an integrated graphene-protein biosensor chip for use in point-of-care (POC) is described. The initial prototype is a glucometer that uses optimized glucose oxidase bound to a graphene field effect sensor. Technologies required for development of the prototype include modification of the glucose oxidase for improved performance by protein engineering, methods to bind the enzyme to the graphene attached to the silicon oxide surface of sensor chip, and integration into a thermoplastic microfluidic device. Initial results indicate the prototype glucometer can measure glucose concentrations from low physiological levels to molar concentrations.

Using all-atom molecular dynamics simulations in water environment, it was possible to demonstrate spontaneous and tight encapsulation of glucose oxidase (GOx) dimer by graphene 7 nm x 7 nm sheets linked together by linkers of different width and forming a flower-like or cross-like shapes. The partially overlapping graphene sheets compacted the structure of GOx dimer, bringing the monomers much closer to one another. We found that the most complete wrapping of the enzyme was achieved for the cross-like graphene. Encapsulation can be a useful way to obtain a large contact surface. However, an exceptionally tight binding by the graphene can also influence the positions of amino acids in the enzyme binding site resulting in less efficient catalytic reaction. Furthermore, such extensive encapsulation could block the access of the substrate to the active site of the enzyme. Contrary, a partial encapsulation by graphene using nano-sheets caused only small distortions of GOx structure while the contact surface with graphene was high.

HER-conjugated hollow nanoparticles (HER–HNP, ca. 50 nm in diameter) are fabricated using a dissolution and re-deposition method and used to encapsulate camptothecin (CPT). The HER-HNP-CPT is used as an anti-cancer agent for human breast cancer SK-BR-3. It has excellent mono-dispersity and a high loading efficiency for CPT. Two kind of cell lines are used in this study; SK-BR-3 and RAW 264.7. SK-BR-3 and RAW 264.7 are used as targeting and controlling cell line, respectively. When SK-BR-3 cells are treated with HER-HNP-CPT, the viability decreased to 55%, which is ca. 1.5 times higher anti-cancer efficiency in comparison to RAW 264.7. The HER-HNP-CPT system offers a new opportunity to facilitate implementation of a hydrophobic drug for effective anti-cancer treatment of SK-BR-3 cells.

Fundamental understanding of the oxygen reduction reaction (ORR) electrocatalyzed by nitrogen-doped carbon requires a well-defined structure to correlate structure to function. Well-characterized N-doped graphitic nanostructures derived from benzene derivatives have been synthesized in our group, and shown to catalyze a four-electron ORR under alkaline conditions. Density functional theory calculations have been performed on a model N-doped graphitic nanostructure, C50N2H20, to determine an oxygen activation mechanism. With guidance through an experimentally determined Pourbaix diagram, DFT calculations clearly indicate that the catalyst must undergo a 2e−,1H+ reduction to generate a reactive carbanionic intermediate that activates oxygen with a spin inversion.