A team of researchers recently published a paper in the journal ACS Applied Nano Materials that demonstrated the effectiveness of specific chemically-modified nanohole edges in reduced graphene oxide (rGO) in binding proteins.
Biosensors are gaining considerable prominence owing to the rising significance of quantitative or qualitative detection of biological markers and early prognosis of diseases. Such a shift is necessitating the development of accessible, accurate, and rapid techniques.
Biosensors based on graphene, where graphene is used as a transducer or buffer, have attracted wide attention due to the exceptional properties of graphene, such as effect-free high permittivity and high carrier mobility.
Graphene combined with nanoparticles has been investigated as a biosensor in previous research; however, during the development of such biosensors, certain properties of graphene can potentially affect the detection limit of the sensor. Thus, the surface specificity of graphene must be modified for certain molecules to use in biosensors.
Modifying Graphene Nanohole Edges
In this study, researchers initially synthesized rGO nanomembrane (NMG), with nanoholes in the scale of 40-60 nm center-to-center distances and 20-25 nm in diameter, following two distinct approaches that are based on gold nano-islands (Au-NIs) and gold nanoparticles (AuNPs). Later, they performed a specific covalent chemical modification of the nanohole edges in the NMG and evaluated their effectiveness in capturing biological molecules.
rGO-AuNPs were fabricated by depositing an rGO monolayer over a self-assembled AuNP monolayer and then removing the NPs. rGO-Au-NIs were also formed in a similar manner excluding the self-assembled AuNP monolayer, which was replaced by an Au-NI layer.
Ultraviolet (UV) spectroscopy, infrared spectroscopy, and scanning electron microscope (SEM) were used to characterize the deposited layers after and before removing the NIs or the NPs.
The chemical groups in the layers were defined and investigated by Fourier transform infrared (FTIR) spectroscopy.
3-(aminopropyl) triethoxysilane (APTES) was utilized to modify the holes’ edges, while N-ethyl-N′-(3-(dimethylamino) propyl) carbodiimide/N-hydroxysuccinimide) (EDC/NHS) was applied as coupling agents to facilitate coupling between the NMG nanohole edges and a biological moiety such as an antibody.
The successful modification of the NMG edges and the scope of monitoring protein binding were investigated by attaching the angiotensin-converting enzyme 2 (ACE2) antibody to the edges, and subsequently measuring the binding ability of the edges to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein.
A number of control experiments were performed to verify the successful specific binding between the antibody/bioreceptor/ACE2 protein and the target molecule/SARS-CoV-2 spike protein.
Achieving Successful Protein Binding
NMG was successfully synthesized on the rGO layer using AuNPs and Au-NIs. The rGO films appeared as separated wrinkled flakes owing to the deformation after exfoliation and restacking processes, indicating the formation of a high-quality rGO-layered structure nanosheet.
The flakes appeared as a uniformed background after the rGO monolayer was deposited on the glass slide, and demonstrated a 97.7% transparency at a wavelength of 550 nm.
The FTIR spectrum of the GO layer displayed characteristic peaks of hydroxyl, carboxyl, aromatic, carboxy, epoxy group, whereas the FTIR spectrum of the chemically reduced GO or rGO lacked the peaks of oxygen groups that include epoxy and hydroxyl groups. Additionally, the intensities of characteristic peaks of oxygen were reduced in rGO, indicating a high degree of reduction of the GO sheet.
The aromatic groups represented the only remaining peaks at 1585 and 1623 cm-1 in the rGO.
NIs were distributed homogenously with a diameter of 25-35 nm after annealing. A high concentration of hydroxyl groups was observed at the nanohole edges in the NMG after its formation. The absorption peaks associated with nitrogen-hydrogen (N−H) bending and carbon-hydrogen (C−H) swing were observed at 1582 and 1380 cm-1 after the NMG was silanized with APTES, indicating the functionalization of NMG with APTES.
After the functionalization, the amine group was observed in the NMG with a separate peak at 1414 cm-1, which corresponded to the oxygen-hydrogen (O−H) bending vibration of the carboxyl group.
An amide bond was observed at 1533 cm-1 after the application of coupling agents at NMG edges, and more bands at 3280 and 1641 cm-1 emerged after the covalent bond interactions with the ACE2.
The amide bond was created between the carboxyl groups on the antibody and APTES-modified NMG edges owing to the presence of the amine groups at the edges. The intensity of the 1641 cm-1 peak after antibody interaction was higher compared to the peak observed in the NH2-NMG, indicating the successful antibody surface functionalization on NH2-NMG.
The FTIR spectra of NMG and rGO were measured by modifying and activating both of them with APTES and EDC/NHS. No change in peak positions was observed in rGO. However, the intensity of the amide bond increased substantially in NMG, indicating the specificity of protein binding only to hole edges and not to the surface.
Real-time binding measurements demonstrated an affinity constant of 0.93 × 109 M-1 and a dissociation constant (KD) of 1.08 nM.
Taken together, the findings of this study demonstrated a versatile and robust mechanism to perform specific modifications of NMG edges to use NMG as a real-time highly sensitive biosensor.
As they grow, solid tumors surround themselves with a thick, hard-to-penetrate wall of molecular defenses. Getting drugs past that barricade is notoriously difficult. Now, scientists at UT Southwestern have developed nanoparticles that can break [...]
In an article recently published in the journal Talanta, researchers demonstrated a new approach to enable the specific detection of biomarkers in human tear by employing an aptamer-based graphene affinity nanosensor. The ability to detect [...]
Selenium (Se) is an essential element found in aquatic feeds that promotes the proper development, wellbeing, and fitness of marine animals. Selenium can be transformed into nanomaterials that are more easily accessible, absorbed, and consumed by [...]
In an article recently published in the journal Nanotechnology, researchers employed a single particle imaging method for fluorescence excitation with moderate intensity to achieve spatial resolution. Here, the semiconductor nanocrystals were accessed, whose emission lifetimes [...]
Grinding is an essential manufacturing process, yet the heat due to friction associated with the process causes damage to the part being processed. Lubrication is used to reduce friction; however, traditional petroleum-based lubricants can [...]
A team of researchers from HSE University, Skoltech, MPGU, and MISIS have developed a nanophotonic-microfluidic sensor whose potential applications include cancer detection, monitoring and treatment response assessment. Today, the device can identify gases and [...]
Researchers have made a scientific breakthrough with the development of ‘nanomachines’ that can kill cancerous cells. The research team headed by Dr Youngdo Jeong from the Center for Advanced Biomolecular Recognition at the Korea Institute of Science and Technology (KIST) has engineered [...]
A novel freeze-dissolving approach has been devised that offers greater efficiency and sustainability compared to the classic freeze-drying process to make superfine powder or nanoparticles. In the research published in the journal ACS Sustainable Chemistry & Engineering, sphere-shaped [...]
Participants wanted for study on the regulation of what future AI-driven nanomedicines should look like
Would you like to help in some research on the regulation of what future AI-driven nanomedicines should look like? If so, researchers at the University of Bristol are looking for volunteers to discuss ethical [...]
In an article recently published in the journal Applied Surface Science, the researchers synthesized green fluorescent carbon dots (G-CDs) from 3,5-diaminobenzoic acid and citric acid. The as-prepared G-CDs were used to target the nucleolus and [...]
Doxorubicin (DOX) is a powerful anti-cancer medication, and efforts have been made to design nanostructures for delivering it to cancerous cells. The nanostructures increase the cytotoxic effects of DOX on cancerous cells, while reducing the negative effects [...]
A team of Brown University researchers has developed a new responsive material that is able to release encapsulated cargo only when pathogenic bacteria are present. The material could be used to make wound dressings [...]
Novel three-drug regimen used to manage life-threatening developments. In April 2021, a 42-year-old man reached out to Brian Hill, MD, PhD, for a second opinion after being diagnosed with hairy cell leukemia following a bone [...]