RF plasma-enhanced conducting Polymer/W5O14 based self-propelled micromotors for miRNA detection.

Functionalized micro/nanomotors having immobilized biological molecules provide excellent and powerful tools for the detection of target molecules. Based on surface modifications and mobilities of micromotors, we report herein a new experimental design of high-speed, self-propelled and plasma modified micromotors for biomedical applications. Within this scope, in the first step, poly (3,4-ethylenedioxythiophene) (PEDOT) was in-situ synthesized onto W5O14 (tungsten trioxide) wires by using radio frequency (RF) rotating plasma reactor. Then, W5O14/PEDOT-Platinum (Pt) hybrid micromotors were fabricated by using magnetron sputtering technique. The detection of miRNA-21 was performed using both single-stranded DNA (ssDNA) (probe DNA) immobilized W5O14-Pt and W5O14/PEDOT-Pt micromotors. The fluorescence signals were determined after hybridization of probe DNA immobilized these novel W5O14-Pt and W5O14/PEDOT-Pt micromotors with different molar concentrations of the synthetic target (6-carboxyfluorescein dye (FAM)-labeled miRNA-21). The changes in the micromotor speeds after the hybridization process were also evaluated. W5O14/PEDOT-Pt micromotors presented better sensor properties compared to the W5O14-Pt micromotors. A good linearity for miRNA-21 concentration between 0.1 nM and 100 nM was obtained for these micromotors based on their fluorescence intensities. The detection limit was found as 0.028 nM for W5O14/PEDOT-Pt micromotors (n = 3). Thus, sensor and motor characteristics of the W5O14-Pt micromotors were improved by RF plasma enhanced PEDOT coatings. The new catalytic W5O14 based micromotors demonstrated here had great potential for the development of sensitive and simple sensing platforms for detection of miRNA-21.

Biosensing applications of titanium dioxide coated graphene modified disposable electrodes.

In the present work, preparation of titanium dioxide coated graphene (TiO2/graphene) and the use of this nanocomposite modified electrode for electrochemical biosensing applications were detailed. The nanocomposite was prepared with radio frequency (rf) rotating plasma method which serves homogeneous distribution of TiO2 onto graphene. TiO2/graphene was characterized with scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis. Then, this nanocomposite was dissolved in phosphate buffer solution (pH 7.4) and modified onto disposable pencil graphite electrode (PGE) by dip coating for the investigation of the biosensing properties of the prepared electrode. TiO2/graphene modified PGE was characterized with SEM, EDS and cyclic voltammetry (CV). The sensor properties of the obtained surface were examined for DNA and DNA-drug interaction. The detection limit was calculated as 1.25mgL(-1) (n=3) for double-stranded DNA (dsDNA). RSD% was calculated as 2.4% for three successive determinations at 5mgL(-1) dsDNA concentration. Enhanced results were obtained compared to the ones obtained with graphene and unmodified (bare) electrodes.

Poly(3,4-ethylenedioxythiophene) coated chitosan modified disposable electrodes for DNA and DNA-drug interaction sensing.

The need for sensitive, selective, rapid and low-cost detection systems for DNA and DNA-drug interactions are in crucial demand for diagnostics and real-world applications. This work details the preparation of poly(3,4-ethylenedioxythiophene) (PEDOT) coated chitosan (CHIT) and the use of PEDOT coated CHIT modified disposable pencil graphite electrodes (PGEs) for DNA and DNA-anticancer drug interaction sensing. PEDOT coated CHIT (PEDOT/CHIT) was prepared with rotating plasma polymerization using radio frequency (RF: 13.56 MHz) power generator. Then, modification of PEDOT/CHIT onto PGE was performed. The use of the prepared electrode was carried out using differential pulse voltammetry (DPV). Cyclic voltammetry (CV) and scanning electron microscopy (SEM) were used to characterize the PEDOT/CHIT/PGE. The performance of the electrode was compared with CHIT/PGE and unmodified PGE. The electrode exhibited high sensitivity for the investigation of DNA sensing and DNA-anticancer drug interaction. Such disposable sensing platform hold considerable promise for diverse bioapplications.

Electrospun chitosan/PEDOT nanofibers.

Plasma-modified chitosan and poly(3,4-ethylenedioxythiophene) were blended to obtain conducting nanofibers with polyvinyl alcohol as a supporting polymer at various volumetric ratios by electrospinning method. Chemical compositions and molecular interactions among nanofiber blend components were determined using Fourier transform infrared spectroscopy (FTIR). The conducting blends containing plasma-modified chitosan resulted in a superior antibacterial activity and thinner fiber formation than those containing chitosan without plasma-modification. The obtained nanofiber diameters of plasma-modified chitosan were in the range of 170 to 200 nm and those obtained from unmodified chitosan were in the range of 190 to 246 nm. The electrical and electrochemical properties of nanofibers were also investigated by four-point probe conductivity and cyclic voltammetry measurements.

RF hydrazine plasma modification of chitosan for antibacterial activity and nanofiber applications.

Chitosan nano powders were modified using RF hydrazine plasma produced at low pressure (26.66Pa) with 13.56MHz frequency at a power of 100W for 30min. Characterization and investigation of the properties of plasma-modified chitosan (PMCh) and non-modified chitosan (Ch) were carried out using an optical monochromator, FTIR, florescence analysis, TGA, SEM, and X-ray techniques. FTIR spectra of PMCh indicated a band broadening at 3436cm(-1) that confirmed increasing functional groups based on H-bonding. The number of NH(2) groups was determined from fluorescence analysis. TGA analysis shows that the moisture absorption is three times higher in the PMCh structure. Ch and PMCh in PVA solutions were used to produce nanofibers by the electrospinning method; average fiber diameters were 480 and 280nm for Ch and PMCh, respectively. It was found that the antibacterial effect of PMCh is better than the Ch for Gram-positive strains.

Elimination of Aspergillus parasiticus from nut surface with low pressure cold plasma (LPCP) treatment.

Low pressure cold plasma (LPCP) using air gases and sulfur hexafluoride (SF(6)) was developed and tested for anti-fungal efficacy against Aspergillus parasiticus on various nut samples. Artificially A. parasiticus contaminated hazelnuts, peanuts, and pistachio nuts were treated with air gases plasma and SF(6) plasma for up to 20 min duration. The sterilizing effect of LPCP on A. parasiticus was higher during the early treatment period than the later treatment period. Air gases plasma treatment for 5 min resulted in 1-log reduction of A. parasiticus and a further 5 min treatment resulted in additional 1-log reduction. SF(6) plasma application was more effective resulting in approximately a 5-log decrease in fungal population for the same duration. When effectiveness of plasma treatment against aflatoxins were tested, 20 min air gases plasma treatment resulted in a 50% reduction in total aflatoxins (AFB1, AFB2, AFG1, and AFG2), while only a 20% reduction in total aflatoxin was observed after 20 min SF(6) plasma treatment. In this study, a rapid, functional clean-up method for the elimination of aflatoxin producing fungus from shelled and unshelled nuts was investigated as a suitable fungal decontamination method.

Decontamination of grains and legumes infected with Aspergillus spp. and Penicillum spp. by cold plasma treatment.

The objective of this study was to determine the efficacy of a self-designed low pressure cold plasma (LPCP) system using air gases or SF6. For the inactivation and/or elimination of two pathogenic fungi, Aspergillus spp. and Penicillum spp. artificially contaminated on seed surface. The plasma decontamination process was performed by batch process in vacuum chamber, using gas injection followed by plasma discharge for the duration of 5-20 min. The plasma treatment reduced the fungal attachment to seeds below 1% of initial load depending on the initial contamination level, while preserving germination quality of the seed. A significant reduction of 3-log for both species was achieved within 15 min of SF6 plasma treatment time. Air gases plasma and SF6 plasma in particular provides an interesting surface decontamination alternative for seeds.

Exact solution for the generalized Bohm criterion in a two-ion-species plasma.

For a weakly collisional two-ion species plasma, it is shown that the minimum phase velocity of ion acoustic waves (IAWs) at the sheath-presheath boundary is equal to twice the phase velocity in the bulk plasma. This condition provides a theoretical basis for the experimental results that each ion species leaves the plasma with a drift velocity equal to the IAW phase velocity in the bulk plasma [D. Lee et al., Appl. Phys. Lett. 91, 041505 (2007)10.1063/1.2760149]. It is shown that this result is a consequence of the generalized Bohm criterion and fluid expressions for the IAW phase velocities.