Influence of carbon nanomaterial defects on the formation of protein corona

The Hybrid Nano-Biointerface between Proteins/Peptides and Two-Dimensional Nanomaterials

In typical protein-nanoparticle surface interactions, the biomolecule surface binding and consequent conformational changes are intermingled with each other and are pivotal to the multiple functional properties of the resulting hybrid bioengineered nanomaterial. In this review, we focus on the peculiar properties of the layer formed when biomolecules, especially proteins and peptides, face two-dimensional (2D) nanomaterials, to provide an overview of the state-of-the-art knowledge and the current challenges concerning the biomolecule coronas and, in general, the 2D nano-biointerface established when peptides and proteins interact with the nanosheet surface. Specifically, this review includes both experimental and simulation studies, including some recent machine learning results of a wide range of nanomaterial and peptide/protein systems.

Probing interaction of atherogenic lysophosphatidylcholine with functionalized graphene nanosheets: theoretical modelling and experimental validation

CONTEXT

The potential of graphene derivatives for theranostic applications depends on their compatibility with cellular and biomolecular components. Lysophosphatidylcholine (LPC), a lipid component present in oxidized low-density lipoproteins, microvesicles and free circulation in blood, plays a critical role in the pathophysiology of various diseases. Using density functional theory-based methods, we systematically investigated the interaction of atherogenic LPC molecule with different derivatives of graphene, including pristine graphene, graphene with defect, N-doped graphene, amine-functionalized graphene, various graphene oxides and hydroxylated graphene oxides. We observed that the adsorption of LPC on graphene derivatives is highly selective based on the orientation of the functional groups of LPC interacting with the surface of the derivatives. Hydroxylated graphene oxide exhibited the strongest interaction with LPC with adsorption energy of - 2.1 eV due to the interaction between the hydroxyl group on graphene and the phosphate group of LPC. The presence of aqueous medium further enhanced this interaction indicating favourable adsorption of LPC and graphene oxide in biological systems. Such strong interaction leads to substantial change in the electronic structure of the LPC molecule, which results in the activation of this molecule. In contrast, amine-modified graphene showed the least interaction. These theoretical results are in line with our experimental fluorescence spectroscopic data of LPC/1-anilino-8-napthalene sulfonic acid complex. Our present comprehensive investigation employing both theoretical and experimental methods provides a deeper understanding of graphene-lipid interaction, which holds paramount importance in the design and fabrication of graphene-based nanomaterials for biomedical applications.

METHODS

In this study, we employed the density functional theory-based methods to investigate the electronic and structural properties of graphene derivatives and LPC molecule using the Quantum Espresso package. The exchange-correlation functional was described within generalized gradient approximation (GGA) as parameterized by Perdew, Burke and Ernzerhof (PBE). The valence electrons were represented using plane wave basis sets. `The Grimme's dispersion method was used to include the van der Waals dispersion correction.

Exploring CVD Method for Synthesizing Carbon-Carbon Composites as Materials to Contact with Nerve Tissue

The main purpose of these studies was to obtain carbon-carbon composites with a core built of carbon fibers and a matrix in the form of pyrolytic carbon (PyC), obtained by using the chemical vapor deposition (CVD) method with direct electrical heating of a bundle of carbon fibers as a potential electrode material for nerve tissue stimulation. The methods used for the synthesis of PyC proposed in this paper allow us, with the appropriate selection of parameters, to obtain reproducible composites in the form of rods with diameters of about 300 µm in 120 s (CF_PyC_120). To evaluate the materials, various methods such as scanning electron microscopy (SEM), scanning transmission electron microscope (STEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and tensiometer techniques were used to study their microstructural, structural, chemical composition, surface morphology, and surface wettability. Assessing their applicability for contact with nervous tissue cells, the evaluation of cytotoxicity and biocompatibility using the SH-SY5Y human neuroblastoma cell line was performed. Viability and cytotoxicity tests (WST-1 and LDH release) along with cell morphology examination demonstrated that the CF_PyC_120 composites showed high biocompatibility compared to the reference sample (Pt wire), and the best adhesion of cells to the surface among all tested materials.

Post-administration labeling with Palladium(II) ions enables ICP-MS-based determination of the biodistribution of carbonized nanogels

Carbonized nanogels (CNGs) are carbon-based nanomaterials possessing excellent antibacterial and antiviral activities for treating infectious diseases. Thus, investigations of the biodistribution of CNGs are crucial in ensuring their biosafety for in vivo applications. In this study, we combined a labeling scheme, employing tetrachloropalladate (PdCl₄^2-) ions to selectively label the administered CNGs in solubilized tissue samples, and an automatic sample pretreatment scheme, using a knotted reactor to effectively separate the PdCl₄^2--labeled CNGs from the free PdCl₄^2- ions and the tissue matrices, to enable reliable and interference-free quantification of CNGs through measuring the signal intensities of Pd using inductively coupled plasma mass spectrometry (ICP-MS). After optimizing the labeling conditions and the separation scheme, we observed that the PdCl₄^2- ions bound strongly to the CNGs (dissociation constant: 23.0 nM), with the method's detection limits reaching 1.6 fg L^-1 and 0.9 μg L^-1 within working ranges from 10^-4 to 1 μg L^-1 and from 1 to 1000 μg L^-1, respectively. We verified the reliability and applicability of this analytical method through spike analyses of solubilized rat liver, spleen, kidney, lung, brain, and blood samples (recoveries ranging from 96 to 102%) and through analyses of these rat organ and tissue samples after giving rats an intravenous dose of CNGs (2.5 mg kg^-1 body weight). The biodistribution data indicated that these administered CNGs deposited mainly in the liver, lung, and spleen at 10 min and 1 h post-administration. Our study revealed that this post-administration labeling scheme coupled with ICP-MS allows accurate determination of the biodistribution of carbonized nanomaterials.

Toward the Specificity of Bare Nanomaterial Surfaces for Protein Corona Formation

Aiming at creating smart nanomaterials for biomedical applications, nanotechnology aspires to develop a new generation of nanomaterials with the ability to recognize different biological components in a complex environment. It is common opinion that nanomaterials must be coated with organic or inorganic layers as a mandatory prerequisite for applications in biological systems. Thus, it is the nanomaterial surface coating that predominantly controls the nanomaterial fate in the biological environment. In the last decades, interdisciplinary studies involving not only life sciences, but all branches of scientific research, provided hints for obtaining uncoated inorganic materials able to interact with biological systems with high complexity and selectivity. Herein, the fragmentary literature on the interactions between bare abiotic materials and biological components is reviewed. Moreover, the most relevant examples of selective binding and the conceptualization of the general principles behind recognition mechanisms were provided. Nanoparticle features, such as crystalline facets, density and distribution of surface chemical groups, and surface roughness and topography were encompassed for deepening the comprehension of the general concept of recognition patterns.

Molecular Modeling of Protein Corona Formation and Its Interactions with Nanoparticles and Cell Membranes for Nanomedicine Applications

The conformations and surface properties of nanoparticles have been modified to improve the efficiency of drug delivery. However, when nanoparticles flow through the bloodstream, they interact with various plasma proteins, leading to the formation of protein layers on the nanoparticle surface, called protein corona. Experiments have shown that protein corona modulates nanoparticle size, shape, and surface properties and, thus, influence the aggregation of nanoparticles and their interactions with cell membranes, which can increases or decreases the delivery efficiency. To complement these experimental findings and understand atomic-level phenomena that cannot be captured by experiments, molecular dynamics (MD) simulations have been performed for the past decade. Here, we aim to review the critical role of MD simulations to understand (1) the conformation, binding site, and strength of plasma proteins that are adsorbed onto nanoparticle surfaces, (2) the competitive adsorption and desorption of plasma proteins on nanoparticle surfaces, and (3) the interactions between protein-coated nanoparticles and cell membranes. MD simulations have successfully predicted the competitive binding and conformation of protein corona and its effect on the nanoparticle-nanoparticle and nanoparticle-membrane interactions. In particular, simulations have uncovered the mechanism regarding the competitive adsorption and desorption of plasma proteins, which helps to explain the Vroman effect. Overall, these findings indicate that simulations can now provide predications in excellent agreement with experimental observations as well as atomic-scale insights into protein corona formation and interactions.

Advancing Rational Control of Peptide-Surface Complexes

Understanding peptide-surface interactions is crucial for programming self-assembly of peptides at surfaces and in realizing their applications, such as biosensors and biomimetic materials. In this study, we developed insights into the dependence of a residue's interaction with a surface on its neighboring residue in a tripeptide using molecular dynamics simulations. This knowledge is integral for designing rational mutations to control peptide-surface complexes. Using graphene as our model surface, we estimated the free energy of adsorption (ΔA_ads) and extracted predominant conformations of 26 tripeptides with the motif LNR-CR-Gly, where LNR and CR are variable left-neighboring and central residues, respectively. We considered a combination of strongly adsorbing (Phe, Trp, and Arg) and weakly adsorbing (Ala, Val, Leu, Ser, and Thr) amino acids on graphene identified in a prior study to form the tripeptides. Our results indicate that ΔA_ads of a tripeptide cannot be estimated as the sum of ΔA_ads of each residue indicating that the residues in a tripeptide do not behave as independent entities. We observed that the contributions from the strongly adsorbing amino acids were dominant, which suggests that such residues could be used for strengthening peptide-graphene interactions irrespective of their neighboring residues. In contrast, the adsorption of weakly adsorbing central residues is dependent on their neighboring residues. Our structural analysis revealed that the dihedral angles of LNR are more correlated with that of CR in the adsorbed state than in bulk state. Together with ΔA_ads trends, this implies that different backbone structures of a given CR can be accessed for a similar ΔA_ads by varying the LNR. Therefore, incorporation of context effects in designing mutations can lead to desired peptide structure at surfaces. Our results also emphasize that these cooperative effects in ΔA_ads and structure are not easily predicted a priori. The collective results have applications in guiding rational mutagenesis techniques to control orientation of peptides at surfaces and in developing peptide structure prediction algorithms in adsorbed state from its sequence.

Molecular Control of Interfacial Fibronectin Structure on Graphene Oxide Steers Cell Fate

The use of graphene-based materials (GBMs) for tissue-engineering applications has been growing exponentially because of the seemingly endless multifunctional and tunable physicochemical properties of graphene that can be exploited to influence cellular behavior. Despite many demonstrations wherein cell physiology has been modulated on different GBMs, a clear mechanism connecting the different physicochemical properties of GBMs to cell fate has remained elusive. In this work, we demonstrate how different GBMs can be used to bias cell fate in a multiscale study-starting from serum protein (fibronectin) adsorption and its molecular scale morphology, structure, and bioactivity and ending with stem cell response. Using heat to chemically reduce graphene oxide without changing physical properties, we show that graphene chemistry controls surface-adsorbed molecular conformation and morphology, epitope presentation, and stem cell attachment. Moreover, this subtle change in the protein structure was found to drive increased bone differentiation of stem cells, suggesting that the physicochemical properties of graphene biases cell fate by directly influencing the adsorbed protein structure and subsequent biochemical activity.

Biostimulation and toxicity: The magnitude of the impact of nanomaterials in microorganisms and plants

Background

Biostimulation and toxicity constitute the continuous response spectrum of a biological organism against physicochemical or biological factors. Among the environmental agents capable of inducing biostimulation or toxicity are nanomaterials. On the < 100 nm scale, nanomaterials impose both physical effects resulting from the core’s and corona’s surface properties, and chemical effects related to the core’s composition and the corona’s functional groups.

Aim of Review

The purpose of this review is to describe the impact of nanomaterials on microorganisms and plants, considering two of the most studied physical and chemical properties: size and concentration.

Key Scientific Concepts of Review

Using a graphical analysis, the presence of a continuous biostimulation-toxicity spectrum is shown considering different biological responses. In microorganisms, the results showed high susceptibility to nanomaterials. Simultaneously, in plants, a hormetic response was found related to nanomaterials concentration and, in a few cases, a positive response in the smaller nanomaterials when these were applied at a higher level. With the above, it is concluded that: (1) microorganisms are more susceptible to nanomaterials than plants, (2) practically all nanomaterials seem to induce responses from biostimulation to toxicity in plants, and (3) the kind of response observed will depend in a complex way on the nanomateriaĺs physical and chemical characteristics, of the biological species with which they interact, and of the form and route of application and on the nature of the medium -soil, soil pore water, and biological surfaces- where the interaction occurs.

Proteomic exploration of soft and hard biocorona onto PEGylated multiwalled carbon nanotubes

In nanomedicine, carbon nanotubes (CNTs) are considered potential candidates as drug delivery systems. The absorption of proteins onto CNTs, after their administration in physiological environment, forms the protein corona or biocorona, which is able to influence their biological properties and biocompatibility. For this reason, characterization of protein corona is a crucial aspect in the research to control CNTs toxicity and capability to target cells. Multiwalled carbon nanotubes (MWCNTs) were functionalized with polyethylene glycol (PEG), chosen considering its well-known biocompatibility, and then incubated in human plasma to create the biocorona. Plasma proteins, which bound around PEGylated CNTs, were detached using five different solutions, grouped into native and denaturant buffers, and used to characterize the two components of biocorona. The proteomic fingerprinting of biocorona was performed by SDS-PAGE and 2D-PAGE separation and mass spectrometry analysis. Native eluents were able to capture proteins of soft corona, characterized by complex secondary structures, and formed by both β-sheet and α-helices domains. Denaturant buffers have eluted many proteins with a high percentage of the α-helix structure that could be involved in specific interactions responsible for the formation of hard corona.

Interfacial charge transfer with exfoliated graphene inhibits fibril formation in lysozyme amyloid

Amyloid fibrillation is known to contribute in a variety of diseases including neurodegenerative disorders (e.g., Alzheimer's and Parkinson's disease) and type II diabetes. The inhibition of fibrillation has been suggested as a possible therapeutic strategy to prevent neuronal and pancreatic β-cell death associated with amyloid diseases. To this end, strong hydrophobic and π-π interactions between proteins and nanomaterials at the nanobio interface could be used to mitigate the stacking of amyloid structures associated with fibrillation. In this study, the authors show that exfoliated graphene effectively inhibits the formation of amyloid fibrils using a model amyloid-forming protein, viz., hen egg white lysozyme (HEWL). While previous theoretical models posit that hydrophobic and π-π stacking interactions result in strong interactions between graphene and proteins, the authors experimentally identified the presence of additional interfacial charge transfer interactions between HEWL and graphene using micro-Raman spectroscopy and Kelvin probe force microscopy. Their photoluminescence spectroscopy and transmission electron microscopy studies evince that the interfacial charge transfer combined with hydrophobic and π-π stacking interactions, specifically between the nanomaterial and the amino acid tryptophan, increase HEWL adsorption on graphene and thereby inhibit amyloid fibrillation.

Linking graphene-based material physicochemical properties with molecular adsorption, structure and cell fate

Graphene, an allotrope of carbon, consists of a single layer of carbon atoms with uniquely tuneable properties. As such, graphene-based materials (GBMs) have gained interest for tissue engineering applications. GBMs are often discussed in the context of how different physicochemical properties affect cell physiology, without explicitly considering the impact of adsorbed proteins. Establishing a relationship between graphene properties, adsorbed proteins, and cell response is necessary as these proteins provide the surface upon which cells attach and grow. This review highlights the molecular adsorption of proteins on different GBMs, protein structural changes, and the connection to cellular function.

Adsorption of amino acids on graphene: assessment of current force fields

We compare the free energies of adsorption (ΔAads) and the structural preferences of amino acids on graphene obtained using the non-polarizable force fields-Amberff99SB-ILDN/TIP3P, CHARMM36/modified-TIP3P, OPLS-AA/M/TIP3P, and Amber03w/TIP4P/2005. The amino acid-graphene interactions are favorable irrespective of the force field. While the magnitudes of ΔAads differ between the force fields, the relative free energy of adsorption across amino acids is similar for the studied force fields. ΔAads positively correlates with amino acid-graphene and negatively correlates with graphene-water interaction energies. Using a combination of principal component analysis and density-based clustering technique, we grouped the structures observed in the graphene adsorbed state. The resulting population of clusters, and the conformation in each cluster indicate that the structures of the amino acid in the graphene adsorbed state vary across force fields. The differences in the conformations of amino acids are more severe in the graphene adsorbed state compared to the bulk state for all the force fields. Our findings suggest that the force fields studied will give qualitatively consistent relative strength of adsorption across proteins but different structural preferences in the graphene adsorbed state.

Carbon Nanotubes and Graphene as Nanoreinforcements in Metallic Biomaterials: a Review

Current challenges in existing metallic biomaterials encourage undertaking research in the development of novel materials for biomedical applications. This paper critically reviews the potential of carbon nanotubes (CNT) and graphene as nanoreinforcements in metallic biomaterials for bone tissue engineering. Unique and remarkable mechanical, electrical, and biological properties of these carbon nanomaterials allow their use as secondary-phase reinforcements in monolithic biomaterials. The nanoscale dimensions and extraordinarily large surface areas of CNT and graphene make them suitable materials for purposeful reaction with living organisms. However, the cytocompatibility of CNT and graphene is still a controversial issue that impedes advances in utilizing these promising materials in clinical orthopedic applications. The interaction of CNT and graphene with biological systems including proteins, nucleic acids, and human cells is critically reviewed to assess their cytocompatibity in vitro and in vivo. It is revealed that composites reinforced with CNT and graphene show enhanced adhesion of osteoblast cells, which subsequently promotes bone tissue formation in vivo. This potential is expected to pave the way for developing ground-breaking technologies in regenerative medicine and bone tissue engineering. In addition, current progress and future research directions are highlighted for the development of CNT and graphene reinforced implants for bone tissue engineering.

Variations in biocorona formation related to defects in the structure of single walled carbon nanotubes and the hyperlipidemic disease state

Ball-milling utilizes mechanical stress to modify properties of carbon nanotubes (CNTs) including size, capping, and functionalization. Ball-milling, however, may introduce structural defects resulting in altered CNT-biomolecule interactions. Nanomaterial-biomolecule interactions result in the formation of the biocorona (BC), which alters nanomaterial properties, function, and biological responses. The formation of the BC is governed by the nanomaterial physicochemical properties and the physiological environment. Underlying disease states such as cardiovascular disease can alter the biological milieu possibly leading to unique BC identities. In this ex vivo study, we evaluated variations in the formation of the BC on single-walled CNTs (SWCNTs) due to physicochemical alterations in structure resulting from ball-milling and variations in the environment due to the high-cholesterol disease state. Increased ball-milling time of SWCNTs resulted in enhanced structural defects. Following incubation in normal mouse serum, label-free quantitative proteomics identified differences in the biomolecular content of the BC due to the ball-milling process. Further, incubation in cholesterol-rich mouse serum resulted in the formation of unique BCs compared to SWCNTs incubated in normal serum. Our study demonstrates that the BC is modified due to physicochemical modifications such as defects induced by ball-milling and physiological disease conditions, which may result in variable biological responses.

The biocorona: a challenge for the biomedical application of nanoparticles

Formation of the biocorona on the surface of nanoparticles is a significant obstacle for the development of safe and effective nanotechnologies, especially for nanoparticles with biomedical applications. Following introduction into a biological environment, nanoparticles are rapidly coated with biomolecules resulting in formation of the nanoparticle-biocorona. The addition of these biomolecules alters the nanoparticle's physicochemical characteristics, functionality, biodistribution, and toxicity. To synthesize effective nanotherapeutics and to more fully understand possible toxicity following human exposures, it is necessary to elucidate these interactions between the nanoparticle and the biological media resulting in biocorona formation. A thorough understanding of the mechanisms by which the addition of the biocorona governs nanoparticle-cell interactions is also required. Through elucidating the formation and the biological impact of the biocorona, the field of nanotechnology can reach its full potential. This understanding of the biocorona will ultimately allow for more effective laboratory screening of nanoparticles and enhanced biomedical applications. The importance of the nanoparticle-biocorona has been appreciated for a decade; however, there remain numerous future directions for research which are necessary for study. This perspectives article will summarize the unique challenges presented by the nanoparticle-biocorona and avenues of future needed investigation.

Charge-transfer interactions induce surface dependent conformational changes in apolipoprotein biocorona

Upon introduction into a biological system, engineered nanomaterials (ENMs) rapidly associate with a variety of biomolecules such as proteins and lipids to form a biocorona. The presence of "biocorona" influences nano-bio interactions considerably, and could ultimately result in altered biological responses. Apolipoprotein A-I (ApoA-I), the major constituent of high-density lipoprotein (HDL), is one of the most prevalent proteins found in ENM-biocorona irrespective of ENM nature, size, and shape. Given the importance of ApoA-I in HDL and cholesterol transport, it is necessary to understand the mechanisms of ApoA-I adsorption and the associated structural changes for assessing consequences of ENM exposure. Here, the authors used a comprehensive array of microscopic and spectroscopic tools to elucidate the interactions between ApoA-I and 100 nm Ag nanoparticles (AgNPs) with four different surface functional groups. The authors found that the protein adsorption and secondary structural changes are highly dependent on the surface functionality. Our electrochemical studies provided new evidence for charge transfer interactions that influence ApoA-I unfolding. While the unfolding of ApoA-I on AgNPs did not significantly change their uptake and short-term cytotoxicity, the authors observed that it strongly altered the ability of only some AgNPs to generate of reactive oxygen species. Our results shed new light on the importance of surface functionality and charge transfer interactions in biocorona formation.

Biological and environmental surface interactions of nanomaterials: characterization, modeling, and prediction

The understanding of nano-bio interactions is deemed essential in the design, application, and safe handling of nanomaterials. Proper characterization of the intrinsic physicochemical properties, including their size, surface charge, shape, and functionalization, is needed to consider the fate or impact of nanomaterials in biological and environmental systems. The characterizations of their interactions with surrounding chemical species are often hindered by the complexity of biological or environmental systems, and the drastically different surface physicochemical properties among a large population of nanomaterials. The complexity of these interactions is also due to the diverse ligands of different chemical properties present in most biomacromolecules, and multiple conformations they can assume at different conditions to minimize their conformational free energy. Often these interactions are collectively determined by multiple physical or chemical forces, including electrostatic forces, hydrogen bonding, and hydrophobic forces, and calls for multidimensional characterization strategies, both experimentally and computationally. Through these characterizations, the understanding of the roles surface physicochemical properties of nanomaterials and their surface interactions with biomacromolecules can play in their applications in biomedical and environmental fields can be obtained. To quantitatively decipher these physicochemical surface interactions, computational methods, including physical, statistical, and pharmacokinetic models, can be used for either analyses of large amounts of experimental characterization data, or theoretical prediction of the interactions, and consequent biological behavior in the body after administration. These computational methods include molecular dynamics simulation, structure-activity relationship models such as biological surface adsorption index, and physiologically-based pharmacokinetic models. WIREs Nanomed Nanobiotechnol 2017, 9:e1440. doi: 10.1002/wnan.1440 For further resources related to this article, please visit the WIREs website.

Defect density in multiwalled carbon nanotubes influences ovalbumin adsorption and promotes macrophage activation and CD4(+) T-cell proliferation

Carbon nanotubes (CNTs) are of great interest for the development of drugs and vaccines due to their unique physicochemical properties. The high surface area to volume ratio and delocalized pi-electron cloud of CNTs promote binding of proteins to the surface forming a protein corona. This unique feature of CNTs has been recognized for potential delivery of antigens for strong and long-lasting antigen-specific immune responses. Based on an earlier study that demonstrated increased protein binding, we propose that carboxylated multiwalled CNTs (MWCNTs) can function as an improved carrier to deliver antigens such as ovalbumin (OVA). To test this hypothesis, we coated carboxylated MWCNTs with OVA and measured uptake and activation of antigen-presenting cells (macrophages) and their ability to stimulate CD4⁺ T-cell proliferation. We employed two types of carboxylated MWCNTs with different surface areas and defects (MWCNT-2 and MWCNT-30). MWCNT-2 and MWCNT-30 have surface areas of ~215 m²/g and 94 m²/g, respectively. The ratios of D- to G-band areas (I_D/I_G) were 0.97 and 1.37 for MWCNT-2 and MWCNT-30, respectively, samples showing that MWCNT-30 contained more defects. The increase in defects in MWCNT-30 led to increased binding of OVA as compared to MWCNT-2 (1,066±182 μg/mL vs 582±41 μg/mL, respectively). Both types of MWCNTs, along with MWCNT–OVA complexes, showed no observable toxicity to bone-marrow-derived macrophages up to 5 days. Surprisingly, we found that MWCNT–OVA complex significantly increased the expression of major histocompatibility complex class II on macrophages and production of pro-inflammatory cytokines (tumor necrosis factor-α and interleukin 6), while MWCNTs without OVA protein corona did not. The coculture of MWCNT–OVA-complex-treated macrophages and OVA-specific CD4⁺ T-cells isolated from OT-II mice demonstrated robust proliferation of CD4⁺ T-cells. This study provides strong evidence for a role for defects in carboxylated MWCNTs and their use in the efficient delivery of antigens for the development of next-generation vaccines.

Biomolecular Interactions and Biological Responses of Emerging Two-Dimensional Materials and Aromatic Amino Acid Complexes

The present work experimentally investigates the interaction of aromatic amino acids viz., tyrosine, tryptophan, and phenylalnine with novel two-dimensional (2D) materials including graphene, graphene oxide (GO), and boron nitride (BN). Photoluminescence, micro-Raman spectroscopy, and cyclic voltammetry were employed to investigate the nature of interactions and possible charge transfer between 2D materials and amino acids. Graphene and GO were found to interact strongly with aromatic amino acids through π-π stacking, charge transfer, and H-bonding. Particularly, it was observed that both physi and chemisorption are prominent in the interactions of GO/graphene with phenylalanine and tryptophan while tyrosine exhibited strong chemisorption on graphene and GO. In contrast, BN exhibited little or no interactions, which could be attributed to localized π-electron clouds around N atoms in BN lattice. Lastly, the adsorption of amino acids on 2D materials was observed to considerably change their biological response in terms of reactive oxygen species generation. More importantly, these changes in the biological response followed the same trends observed in the physi and chemisorption measurements.