Molecular simulation of flavin adenine dinucleotide immobilized on charged single-walled carbon nanotubes for biosensor applications

Untangling the Effects of Doping Carbon with Diverse Heteroatoms on the Bioelectrochemistry of Glucose Oxidase

Great enthusiasm for doping carbon materials with nonmetallic heteroatoms for promoting electrical contact of redox enzymes with electrodes in bioelectronics has been aroused. However, systematic studies of different heteroatoms on enzyme activities are still lacking. Herein, choosing glucose oxidase (GOD) as a model enzyme, carbon nanotubes (CNTs) are used as electron carriers to evaluate the effects of heteroatoms' species on the direct electron transfer and catalytic activities of GOD. Experimental data demonstrate that phosphorus (P)-doped CNTs provide the most intimate electrical contact with GOD compared to other elements (B, N, and S) doping, delivering a 3-fold increase in rate constant (k_s, 2.1 s^-1) and an enhanced turnover rate (k_cat, 2.74 × 10^-9 M cm^-2 s^-1) in comparison with CNTs. Meanwhile, theoretical modeling clarifies that the active center of GOD interacts more strongly with P-doped CNTs and maintains their conformation well compared to other CNTs. This study will help to understand the mechanism of heteroatom doping of carbon on the enzymatic electron transfer and shed light on the design of efficient bioelectrocatalytic interfaces.

Recent advances in computational methods for biosensor design

Biosensors are analytical tools with a great application in healthcare, food quality control, and environmental monitoring. They are of considerable interest to be designed by using cost-effective and efficient approaches. Designing biosensors with improved functionality or application in new target detection has been converted to a fast-growing field of biomedicine and biotechnology branches. Experimental efforts have led to valuable successes in the field of biosensor design; however, some deficiencies restrict their utilization for this purpose. Computational design of biosensors is introduced as a promising key to eliminate the gap. A set of reliable structure prediction of the biosensor segments, their stability, and accurate descriptors of molecular interactions are required to computationally design biosensors. In this review, we provide a comprehensive insight into the progress of computational methods to guide the design and development of biosensors, including molecular dynamics simulation, quantum mechanics calculations, molecular docking, virtual screening, and a combination of them as the hybrid methodologies. By relying on the recent advances in the computational methods, an opportunity emerged for them to be complementary or an alternative to the experimental methods in the field of biosensor design.

Molecular Modeling and Simulation Tools in the Development of Peptide-Based Biosensors for Mycotoxin Detection: Example of Ochratoxin

Mycotoxin contamination of food and feed is now ubiquitous. Exposures to mycotoxin via contact or ingestion can potentially induce adverse health outcomes. Affordable mycotoxin-monitoring systems are highly desired but are limited by (a) the reliance on technically challenging and costly molecular recognition by immuno-capture technologies; and (b) the lack of predictive tools for directing the optimization of alternative molecular recognition modalities. Our group has been exploring the development of ochratoxin detection and monitoring systems using the peptide NFO4 as the molecular recognition receptor in fluorescence, electrochemical and multimodal biosensors. Using ochratoxin as the model mycotoxin, we share our perspective on addressing the technical challenges involved in biosensor fabrication, namely: (a) peptide receptor design; and (b) performance evaluation. Subsequently, the scope and utility of molecular modeling and simulation (MMS) approaches to address the above challenges are described. Informed and enabled by phage display, the subsequent application of MMS approaches can rationally guide subsequent biomolecular engineering of peptide receptors, including bioconjugation and bioimmobilization approaches to be used in the fabrication of peptide biosensors. MMS approaches thus have the potential to reduce biosensor development cost, extend product life cycle, and facilitate multi-analyte detection of mycotoxins, each of which positively contributes to the overall affordability of mycotoxin biosensor monitoring systems.

Endocytosed nanoparticles hold endosomes and stimulate binucleated cells formation

Background

Nanotechnology developed rapidly in cellular diagnosis and treatment, the endocytic system was an important pathway for targeting cell. In the research of developing macrophages as drug carriers or important therapeutic targets, an interesting phenomenon, internalized nanoparticles induced to form binucleated macrophages, was found although the particles dose did not cause obvious cytotoxicity.

Results

Under 25 μg/ml, internalized 30 nm polystyrene beads(30 nm Ps nanoparticles) induced the formation of binucleated macrophages when they entered into endosomes via the endocytic pathway. These internalized 30 nm Ps nanoparticles (25 μg/ml) and 30 nm Au-NPs (1.575 ng/ml) also induced markedly rise of binucleated cell rates in A549, HePG-2 and HCT116. This endosome, aggregated anionic polystyrene particles were dispersed and bound on inner membrane, was induced to form a large vesicle-like structure (LVLS). This phenomenon blocked transport of the particles from the endosome to lysosome and therefore restricted endosomal membrane trafficking through the transport vesicles. Early endosome antigen-1 and Ras-related protein-11 expressions were upregulated; however, the localized distributions of these pivotal proteins were altered. We hypothesized that these LVLS were held by the internalized and dispersed particles decreasing the amount of cell membrane available to support the completion of cytokinesis. In addition, altered distributions of pivotal proteins prevented transfer vesicles from fusion and hampered the separation of daughter cells.

Conclusions

30 nm Ps nanoparticles induced formation of LVLS, blocked the vesicle transport in endocytic system and the distributions of regular proteins required in cytokinesis which led to binucleated cells of macrophages. Markedly raised binucleated rate was also observed in human lung adenocarcinoma epithelial cell line(A549), human hepatoma cell line(HePG-2) and human colorectal cancer cell line(HCT116) treated by 30 nm Ps nanoparticles and Au-NPs.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-016-0173-1) contains supplementary material, which is available to authorized users.