- Plasmonic Tools for Characterizing the Surface of Enveloped Virus Particles
There is growing evidence that glycosphingolipids (GSLs) play a key role in enabling the human immunodeficiency virus type 1 (HIV-1) to utilize dendritic cells (DCs) to accomplish an efficient transfer to CD4+ T cells. To identify the role of GSLs in viral trans-infection, various strategies have been employed to control the GSL concentration in the viral envelope. However, it is currently unclear by how much each individual depletion strategy reduces the GSL envelope concentration, and whether the observed decrease in DC capture is solely due to GSLs density reduction or whether additional factors such as an altered spatial distribution of GSLs contribute as well. In this project, we are going to develop a new optical method for the rapid quantification of viral envelope components, including GSLs, at the single virus level. In addition, we are going to investigate the spatial distribution of these components in wild type and modified forms of virus through optical and electron microscopy. The optical approach takes advantage of plasmonic coupling of 40 nm gold nanoparticles targeted at specific functionalities on the virus surface. The density of the gold nanoparticles on the virion increases with the density of the target in the viral envelope.
Differences in the nanoparticle density can be optically measured, since an increase in nanoparticle density leads to a greater scattering intensity and a red shift of the plasmonic resonance wavelength. In order to make this technique a rapid, high-throughput and multi-task tool with single-virus level sensitivity, we will apply multispectral imaging method to record the scattering spectra. The latter is a wide field microscopy that facilitates a spectral characterization of hundreds of virus particles in the field of view, simultaneously within seconds. Once the implementation of this optical assay is completed, we are going to calibrate the results of this method with ICP-MS, as a direct way of measuring the number of gold particles per virus. Also, the spatial distribution of these components will be investigated through 2 nm gold labeling and imaging with high-resolution TEM. Furthermore, we will apply this enabling technology to characterize patient HIV-1 samples to correlate GSL concentration and virulence. So far, we have implemented a labeling strategy for targeting GM1 GSL on HIV-1 virus-like particles (VLPs, noninfectious form of virus due to lacking genetic material). We have used biotinylated cholera toxin as a ligand for GM1, neutravidin as a linker and 40 nm gold particles coated by a mixture of Biotin PEGs and Acid PEGs in this labeling procedure. The scattering spectra of the labeled VLPs have been recorded and SEM images have validated successful labeling of the target. In the next step, this technique will be further optimized to amplify the differences in the scattering spectra of various VLPs with different GM1 densities. Our aim is to implement a tool that can discriminate even small variations of GM1 densities in viral envelopes.
Optimizing the performance of electrochemical biosensors using a continuous system of fabrication and qualifying the best combination of different strip variables
Abstract: The possibility of making some improvements in the overall structure of the electrochemical portable biosensors to reduce the amount of their error and obtain a higher performance was investigated. Glucose biosensor was chosen as a case study, because it is now commercially produced and widely used, so the results of this study can be compared with a reliable source. This optimizing process was performed by designing and manufacturing a new complex of systems for producing the biosensor test strips, using novel methods such as inkjet printing of conductive electrodes and enzyme solution. Also, the design of the electrical circuits and digital monitoring system was developed.
This project resulted in registering some patents on a digital monitor for showing the concentration of different analytes in blood, capable of working with all available commercial test strips and an optimized semi-industrial production line for biosensor test strips.
Producing a carbon monoxide sensor based on PEDOT-PSS as a conductive polymer
Abstract: Poly (3,4-ethylenedioxy) thiophene–poly (styrenesulfonate) has been used as a base to produce a carbon monoxide chemiresistive detector. Poly (3,4-ethylenedioxy) thiophene/poly (styrenesulfonate) (PEDOT/PSS) thin films were prepared by spin coating method. The polymer was tested by some common gases in the atmosphere to determine its discrimination ability to detect CO. Particular impositions of Fe, Al and morpholine were also added to the polymer solution to improve thin films sensitivity (percent of resistance variations with respect to its initial value) to recognize carbon monoxide from other gases like water vapor. Room air contains a partial pressure of water vapor which has the main effect on pure polymer. As doping agents were added to the polymer, prepared thin films showed a satisfying sensitivity to CO which was now comparable with the effects of room air. The sensor behavior in approach to room air and carbon monoxide and also the effect of dopants on the polymer has been described. (Results were published here.)