Adaptation of a Bacterial Bioluminescent Assay to Monitor Bioeffects of Gold Nanoparticles.

Our current study aimed to adapt a bioluminescent bacteria-based bioassay to monitor the bioeffects of gold nanoparticles (AuNPs). Luminous marine bacteria Photobacterium phosphoreum and AuNPs modified with polyvinylpyrrolidone were employed; low-concentration (≤10-3 g/L) bioeffects of AuNPs were studied. Bioluminescence intensity was used as an indicator of physiological activity in bacteria. Two additional methods were used: reactive oxygen species (ROS) content was estimated with a chemiluminescent luminol method, and bacterial size was monitored using electron microscopy. The bacterial bioluminescent response to AuNPs corresponded to the "hormesis" model and involved time-dependent bioluminescence activation, as well as a pronounced increase in the number of enlarged bacteria. We found negative correlations between the time courses of bioluminescence and the ROS content in bacterial suspensions, demonstrating the relationship between bioluminescence activation and bacterial ROS consumption. The combined effects of AuNPs and a beta-emitting radionuclide, tritium, revealed suppression of bacterial bioluminescent activity (as compared to their individual effects) and a reduced percentage of enlarged bacteria. Therefore, we demonstrated that our bacteria-based bioluminescence assay is an appropriate tool to study the bioeffects of AuNPs; the bioeffects can be further classified within a unified framework for rapid bioassessment.

The Role of Periodic Structures in Light Harvesting.

The features of light propagation in plant leaves depend on the long-period ordering in chloroplasts and the spectral characteristics of pigments. This work demonstrates a method of determining the hidden ordered structure. Transmission spectra have been determined using transfer matrix method. A band gap was found in the visible spectral range. The effective refractive index and dispersion in the absorption spectrum area of chlorophyll were taken into account to show that the density of photon states increases, while the spectrum shifts towards the wavelength range of effective photosynthesis.

In Vivo Cancer Cells Elimination Guided by Aptamer-Functionalized Gold-Coated Magnetic Nanoparticles and Controlled with Low Frequency Alternating Magnetic Field.

Biomedical applications of magnetic nanoparticles under the influence of a magnetic field have been proved useful beyond expectations in cancer therapy. Magnetic nanoparticles are effective heat mediators, drug nanocarriers, and contrast agents; various strategies have been suggested to selectively target tumor cancer cells. Our study presents magnetodynamic nanotherapy using DNA aptamer-functionalized 50 nm gold-coated magnetic nanoparticles exposed to a low frequency alternating magnetic field for selective elimination of tumor cells in vivo. The cell specific DNA aptamer AS-14 binds to the fibronectin protein in Ehrlich carcinoma hence helps deliver the gold-coated magnetic nanoparticles to the mouse tumor. Applying an alternating magnetic field of 50 Hz at the tumor site causes the nanoparticles to oscillate and pull the fibronectin proteins and integrins to the surface of the cell membrane. This results in apoptosis followed by necrosis of tumor cells without heating the tumor, adjacent healthy cells and tissues. The aptamer-guided nanoparticles and the low frequency alternating magnetic field demonstrates a unique non-invasive nanoscalpel technology for precise cancer surgery at the single cell level.

Noninvasive Microsurgery Using Aptamer-Functionalized Magnetic Microdisks for Tumor Cell Eradication.

Magnetomechanical cell disruption using nano- and microsized structures is a promising biomedical technology used for noninvasive elimination of diseased cells. It applies alternating magnetic field (AMF) for ferromagnetic microdisks making them oscillate and causing cell membrane disruption with cell death followed by apoptosis. In this study, we functionalized the magnetic microdisks with cell-binding DNA aptamers and guided the microdisks to recognize cancerous cells in a mouse tumor in vivo. Only 10 min of the treatment with a 100 Hz AMF was enough to eliminate cancer cells from a malignant tumor. Our results demonstrate a good perspective of using aptamer-modified magnetic microdisks for noninvasive microsurgery for tumors.

Electrochemical aptasensor for lung cancer-related protein detection in crude blood plasma samples.

The development of an aptamer-based electrochemical sensor for lung cancer detection is presented in this work. A highly specific DNA-aptamer, LC-18, selected to postoperative lung cancer tissues was immobilized onto a gold microelectrode and electrochemical measurements were performed in a solution containing the redox marker ferrocyanide/ferricyanide. The aptamer protein targets were harvested from blood plasma of lung cancer patients by using streptavidin paramagnetic beads and square wave voltammetry of the samples was performed at various concentrations. In order to enhance the sensitivity of the aptasensor, silica-coated iron oxide magnetic beads grafted with hydrophobic C8 and C4 alkyl groups were used in a sandwich detection approach. Addition of hydrophobic beads increased the detection limit by 100 times. The detection limit of the LC-18 aptasensor was enhanced by the beads to 0.023 ng/mL. The formation of the aptamer - protein - bead sandwich on the electrode surface was visualized by electron microcopy. As a result, the electrochemical aptasensor was able to detect cancer-related targets in crude blood plasma of lung cancer patients.