Enhanced Thermal Stability and Biocompatibility of Gold Nanorods by Graphene Oxide

In the present study, the effect of nanosized graphene oxide layer on thermal stability and biocompatibility of gold nanorods has been examined. The graphene oxide-wrapped gold nanorods were prepared by electrostatic interaction between negatively charged graphene oxide and positively charged nanorods. The resulting nanohybrids were then heated at different time intervals to 95 °C in a water bath to assess the effect of heat on the rods morphology. The structural changes in gold nanorods were monitored via UV-Vis spectroscopy measurements and transmission electron microscopy images. In similar experiments, the graphene oxide used to wrap gold nanorods was reduced by ascorbic acid in a 95 °C water bath. Our results indicate that while bare gold nanorods are highly vulnerable to elevated temperatures, graphene oxide and reduced graphene oxide-coated gold nanorods remain thermally stable with no structural changes. We also confirmed that the enhanced thermal stability is highly dependent on the concentration of deposited graphene oxide available on the surface of the gold nanorods. In addition, we performed an MTT (3-[4,5-dimethylthiazol-2yl]-2,5-diphenyltetrazoliumbromide) assay to make a comparison between the cytotoxicity of the nanohybrids and their primary building blocks on human dermal fibroblast cells as a normal cell line. We found evidence that graphene oxide can enhance the biocompatibility of the rods through covering toxic chemicals on the surface of them.

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Evaluation of the toxicity effects of silk fibroin on human lymphocytes and monocytes

Silk fibroin nanoparticles (SFNPs) as a natural polymer have been utilized in biomedical applications such as suture, tissue engineering‐based scaffolds, and drug delivery carriers. Since there is little data regarding the toxicity effects on different cells and tissues, we aimed to determine the toxicity mechanisms of SFNPs on human lymphocytes and monocytes based on reliable methods. Our results showed that SFNPs (0.5, 1, and 2 mg/mL) induced oxidative stress via increasing reactive oxygen species production, mitochondrial membrane potential (?Ψ) collapse, which was correlated to cytochrome c release and Adenosine diphosphate (ADP)/Adenosine tri phosphate (ATP) ratio increase as well as lysosomal as another toxicity mechanism, which led to cytosolic release of lysosomal digestive proteases, phosphor lipases, and apoptosis signaling. Taken together, these data suggested that SFNPs toxicity was associated with mutual mitochondrial/lysosomal cross‐talk and oxidative stress on human lymphocytes and monocytes with activated apoptosis signaling.     

SPIN2: Predicting sequence profiles from protein structures using deep neural networks

Designing protein sequences that can fold into a given structure is a well‐known inverse protein‐folding problem. One important characteristic to attain for a protein design program is the ability to recover wild‐type sequences given their native backbone structures. The highest average sequence identity accuracy achieved by current protein‐design programs in this problem is around 30%, achieved by our previous system, SPIN. SPIN is a program that predicts sequences compatible with a provided structure using a neural network with fragment‐based local and energy‐based nonlocal profiles. Our new model, SPIN2, uses a deep neural network and additional structural features to improve on SPIN. SPIN2 achieves over 34% in sequence recovery in 10‐fold cross‐validation and independent tests, a 4% improvement over the previous version. The sequence profiles generated from SPIN2 are expected to be useful for improving existing fold recognition and protein design techniques. SPIN2 is available at http://sparks-lab.org .     

Permeability enhancement of Escherichia coli by single‐walled carbon nanotube treatment

This research investigated the use of single‐walled carbon nanotubes (SWNTs) as an additive to increase the permeability of a bacterial cell wall. Recombinant Escherichia coli BL21 (DE3) that expressed β‐lactamase were exposed to SWNTs under various levels of concentration and agitation. Activity of β‐lactamase in the culture fluid and transmission electron microscopy (TEM) were used to determine the amount of released protein, and visually examine the permeability enhancement of the cells. It was found that β‐lactamase release in the culture fluid occurred in a dose‐dependent manner with treatment by SWNTs and was also dependent on agitation rate. Based on TEM, this treatment successfully caused an increase in permeability without significant damage to the cell wall. Consequently, SWNTs can be used as an enhancement agent to cause the release of intracellular proteins. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:654–657, 2017