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.
Graphene-Based Biosensors
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.
News
Largest-Ever Physics Survey Raises New Doubts About Our Model of the Universe
Physicists around the world remain deeply divided on key mysteries of the universe, from dark matter to quantum gravity. The standard cosmological model failed to gain majority support, and no leading theory dominated the [...]
Scientists Just Overturned a 100-Year-Old Belief About Bacteria in the Lungs
New findings raise questions about the role of microbes living in the lungs. More than 35 trillion bacteria live throughout the human body, forming microbiomes in the gut, mouth, lungs, skin, and urogenital tract. [...]
GHCE Concept
From the preface of the book Global Health Care Equivalency in the Age of Nanotechnology, Nanomedicine and Artificial Intelligence, Edited by Frank Boehm: Since the publication of my first book (Nanomedical Device and Systems [...]
Novartis, Ionis drug failure spurs questions
Pelacarsen didn’t protect heart health despite lowering levels of a protein particle, “Lp(a),” in a large clinical trial — a result with important implications for cardiovascular drug research. Dive Brief: An RNA drug from [...]
New injectable treatment helps the brain rebuild after stroke
Biomedical engineers at Duke University have created an injectable biomaterial that may help the brain recover from damage left behind by an ischemic stroke. In experiments with mice, the material transformed the cavity created [...]
Scientists Discover a Hidden “Immune Organ” Inside the Skull
Researchers discovered lymph node-like immune hubs inside skull bone marrow that appear to act as rapid-response centers for the brain. For decades, the brain was thought to operate largely apart from the immune system. [...]
Engineered tRNAs and lipid nanoparticles target nonsense mutation cystic fibrosis
Researchers have developed a potential new approach for treating a form of cystic fibrosis caused by so-called nonsense mutations, combining chemically modified transfer RNAs with lipid nanoparticles designed to deliver the therapy directly to [...]
New pancreatic cancer drug carries a $39,800 monthly list price
A groundbreaking treatment for one of the most common forms of pancreatic cancer has been approved in pill form by the FDA. Revolution Medicines’ oral tablet daraxonrasib, branded as Rasonque, reduced the risk of [...]
Researchers Have Discovered a New Way To Reduce Chronic Nerve Pain
A cancer-linked protein called BRAF may help drive chronic nerve pain, and existing cancer drugs targeting it reduced pain sensitivity in preclinical models. Chronic nerve pain can persist long after an injury and often [...]
Our books now available worldwide!
Online Sellers other than Amazon, Routledge, and IOPP Indigo Global Health Care Equivalency in the Age of Nanotechnology, Nanomedicine and Artifcial Intelligence Global Health Care Equivalency In The Age Of Nanotechnology, Nanomedicine And Artificial [...]
Quantum-Enabled Regenerative Health: Reimagining Wellness, Precision Health and Longevity Medicine
Introduction Healthcare is approaching a frontier where the quantum portfolio could influence not only how disease is diagnosed and treated, but how health itself is measured, modeled, predicted and preserved. Quantum computing, quantum simulation, [...]
FDA Clears First-of-Its-Kind Nonmedication Treatment for PTSD
The FDA has cleared a system that uses brain activity data to personalize magnetic stimulation for PTSD, adding a new nonmedication treatment option. Every day in the United States, approximately 17.5 veterans die by suicide, [...]
FDA approves breakthrough drug to treat advanced pancreatic cancer
The Food and Drug Administration (FDA) approved on Wednesday a drug that could extend the survival of those with metastatic pancreatic cancer. The drug, called daraxonrasib, will be sold under the brand name Rasonque [...]
AI Decodes a Hidden DNA Signal Linked to Disease-Causing Mutations
Machine learning identifies the likely “initiator” and enables new predictions about DNA mutations that can cause disease. Every human cell depends on tens of thousands of genes being switched on at the right time [...]
Pope Leo Urges Global Response to Congo’s Deadliest Ebola Outbreak
Pope Leo called for international action to address the Ebola outbreak in the Democratic Republic of Congo. The epidemic has claimed over 2,500 lives and is the nation's largest recorded outbreak. The Pope emphasized [...]
Is there a summer COVID-19 surge this year? Yep, it’s ramping up again
Hantavirus. Ebola. West Nile. Measles. And, of course, cyclospora — that stomach parasite making people miserable across the country. Americans have plenty to worry about this summer. But remember COVID-19? It may not be [...]
