Rapid development in nanomaterial synthesis and functionalization has led to advanced studies in actuation and manipulation of cellular functions for biomedical applications. Often these actuation techniques employ externally applied magnetic fields to manipulate magnetic nanomaterials inside cell bodies in order to drive or trigger desired effects. While cellular interactions with low-frequency magnetic fields and nanoparticles have been extensively studied, the fundamental mechanisms behind these interactions remain poorly understood. Additionally, modern investigations on these concurrent exposure conditions have been limited in scope, and difficult to reproduce. This study presents an easily reproducible method of investigating the biological impact of concurrent magnetic field and nanoparticle exposure conditions using an in-vitro CHO-K1 cell line model, with the purpose of establishing grounds for in-depth fundamental studies of the mechanisms driving cellular-level interactions. Cells were cultured under various nanoparticle and magnetic field exposure conditions from 0 to 500 μg/ml nanoparticle concentrations, and DC, 50 Hz, or 100 Hz magnetic fields with 2.0 mT flux density. Cells were then observed by confocal fluorescence microscopy, and subject to biological assays to determine the effects of concurrent extreme-low frequency magnetic field and nanoparticle exposures on cellnanoparticle interactions, such as particle uptake and cell viability by MTT assay. Current results indicate little to no variation in effect on cell cultures based on magnetic field parameters alone; however, it is clear that deleterious synergistic effects of concurrent exposure conditions exist based on a significant decrease in cell viability when exposed to high concentrations of nanoparticles and concurrent magnetic field.
A temperature detection system using a micropipette thermocouple sensor was developed for use within mammalian cells during laser exposure with an 8.6-μm beam at 532 nm. We have demonstrated the capability of measuring temperatures at a single-cell level in the microscale range by inserting micropipette-based thermal sensors of size ranging from 2 to 4 μm into the membrane of a live retinal pigment epithelium (RPE) cell subjected to a laser beam. We setup the treatment groups of 532-nm laser-irradiated single RPE cell and in situ temperature recordings were made over time. Thermal profiles are given for representative cells experiencing damage resulting from exposures of 0.2 to 2 s. The measured maximum temperature rise for each cell ranges from 39 to 73°C; the RPE cells showed a signature of death for all the cases reported herein. In order to check the cell viability, real-time fluorescence microscopy was used to identify the transition of pigmented RPE cells between viable and damaged states due to laser exposure.
We investigated the potential for using polydimethylsiloxane microfluidic devices in a biological assay to explore the cellular stress response (CSR) associated with hyperthermia induced by exposure to laser radiation. In vitro studies of laser-tissue interaction traditionally involved exposing a monolayer of cells. Given the heating-cooling dynamics of the cells and nutrient medium, this technique produces a characteristic “bulls-eye” temperature history that plagues downstream molecular analyses due to the nonuniform thermal experience of exposed cells. To circumvent this issue, we devised an approach to deliver single cells to the laser beam using a microfluidic channel, allowing homogeneous irradiation and collection of sufficient like-treated cells to measure changes in CSR after laser heating. To test this approach, we irradiated Jurkat-T cells with a 2-μm-wavelength laser in one branch of a 100-μm-wide bifurcated channel while unexposed control cells were simultaneously passing through the other, identical channel. Cell viability was measured using vital dyes, and expression of HSPA1A was measured using reverse transcription polymerase chain reaction. The laser damage threshold was 25±2 J/cm 2 , and we found a twofold increase in expression at that exposure. This approach may be employed to examine transcriptome-wide/proteome changes and further comparative work across stressors and cell types.
We present herein a silver nanostructure-assisted sensing platform which consists of a combined structure of Ag nanowire (NW) and nanodot (ND) array. Highly enhanced fluorescence from fluorophore is attributed to a strongly coupled optical near-field interaction between proximately located Ag NW and NDs. We obtained enhanced fluorescence intensity with up to 140 folds, as contrasted from background intensity, reaching a theoretical maximum value. On the other hand, fluorescence lifetime was greatly reduced to 0.27 ns (from 2.17 ns for the same fluorophores without nanostructure). This novel platform can be a promising utility for optical imaging and labeling of biological systems with a great sensitivity.
Many applications require delivery of small quantities of functional materials into locations on a substrate in the form of liquid solution. Consequently, interest in nongraphical inkjet printing is growing. In addition, higher resolution for printing flexible electronics is becoming more critical to enhance the performance of printing electronics. Since the resolution of inkjet process is limited by the nozzle size and the statistical variation of droplet flight and spreading phenomena, hybrid inkjet printing has emerged as an attractive processing method. In this work, surface monolayer protected gold nanoparticle was printed in a liquid solution form and cured by laser irradiation to fabricate electrically conductive microlines on glass or polymer substrate at a reduced temperature. Continuous laser curing enabled local heating and the morphology could be controlled as well. Thermal penetration into the substrate could be minimized by using pulsed laser beam. Nanoparticle film was effectively removed by applying femtosecond laser, so that small feature size was obtained. Printing on a heated substrate has advantages over room temperature printing. The solvent evaporates soon after contact, so that a thick layer can be deposited with high jetting frequency. The rapid liquid evaporation also eliminated uneven wetting problems and the smaller feature size was obtained.