Continuous Near-infrared Laser Research Articles

Near-infrared light propelled motion of needlelike liquid metal nanoswimmers

We report a needlelike liquid metal gallium nanoswimmer (LMGNS) with a controllable motion under the exposure of a near-infrared (NIR) laser. The needlelike LMGNS is constructed by a nanoporous template-assisted plastic molding technique. Under the irradiation of a continuous NIR laser, LMGNSs can autonomously move in a direction of tip forward, and their speed could reach up to 31.22 μm s−1 at a laser intensity of 5 W cm−2. The speed of motion and on/off behavior of LMGNSs can be conveniently modulated by controlling the intensity of a NIR laser. Computer simulations reveal that the propulsion of LMGNS is attributed to the self-thermophoresis caused by the temperature gradient along its longitudinal axis, which is induced by the difference of diameters of the two ends. The speed of LMGNS is higher on the substrate with lower surface potential because the thermoosmosis effect, as a resistance, is weaker. Such needlelike liquid metal nanoswimmers have a potential for biomedical applications and active soft matter materials.

Increasing the heating efficiency and ignition rate of certain secondary explosives with absorbing particles under continuous infrared laser radiation

The possibility of increasing the heating efficiency and the ignition rate of secondary explosives with photo-absorbing additives under continuous near-infrared laser radiation was studied. The samples were used in the form of capsules obtained by pressing powders of the following materials: PETN, TNT and ε-CL-20. Carbon black, CuO, nanoscale Al (nAl) and carbon nanotubes were used as photosensitizers. It has been demonstrated that nAl is the most suitable photosensitizer for use with explosives, as it has rather high absorption properties, comparable to those of carbon black, but is easier and more evenly dispersed within the volume of the energetic material. The process of laser heating of PETN, TNT and ε-CL-20 has been studied with different mass fractions of nAl. It has been demonstrated that the addition of nAl can increase the efficiency of ε-CL-20 laser heating by 10–100 times. The dependence of ignition delay of nAl-containing ε-CL-20 on the power of laser radiation has been studied. Relatively short (2–10 ms) ignition delay has been achieved for ε-CL-20+nAl (0.5%) with relatively low continuous laser radiation power (1–4 W) at 0.98 μm wavelength.

Functionalized polymeric nanoparticles loaded with indocyanine green as theranostic materials for targeted molecular near infrared fluorescence imaging and photothermal destruction of ovarian cancer cells.

Ovarian cancer remains the deadliest malignancy of the female reproductive system. The ability to identify and destroy all ovarian tumor nodules may have a termendous impact on preventing tumor recurrence, and patient survival. The objective of this study is to investigate the effectiveness of a nano-structured system for combined near infrared (NIR) fluorescence imaging of human epidermal growth factor receptor-2 (HER2) over-expression, as a biomarker of ovarian cancer cells, and photothermal destruction of these cells in vitro. The nano-structured system consists of the near infrared dye, indocyanine green (ICG), encapsulated within poly(allylamine) hydrochloride chains cross-linked ionically with sodium phosphate. The surface of the construct is functionalized by covalently attached polyethylene glycol, and monoclonal antibodies against HER2 using reducitve amination methods. We use dynamic light scattering, and absorption and fluorescence spectroscopy for phyiscal characterization of the constructs. Flow cytometry and fluorescence microscopy are used to investigate molecular targeting and imaging capabilities of the constructs against SKOV3 and OVCAR3 ovarian cancer cell lines, which have relatively high and low expression levels of the HER2 receptor, respectively. Continuous NIR laser irradiation at 808 nm is used to investigating the utility of the constructs in mediating photothermal destruction of SKOV3 cells. Flow cytometry results indicate that the functionalized nano-constructs are more effective in targeting the HER2 receptor than non-encapsulated ICG and non-functionlaized constructs (P < 0.005). Fluorescence microscopic images show the capaiblity of the functionalized constructs in NIR imaging of HER2 overexpression. The functionalized nano-constructs are also capable of inducing a significantly greater increase in photothermal destruction of SKOV3 cells than free ICG and non-functionalized constructs (P < 0.005). We have demonstrated the efficacy of polymeric nano-structured constructs loaded with ICG, and functionalized with the monoclonal antibodies, as thernaostic materials for targted molecular NIR imaging of the HER2 receptor overexpression on ovarian cancer cells, and photothermal destruction of these cells. These nanoparticles may prove useful towards intraoperative detection, imaging, and phototherapy of small ovarian cancer nodules.

Thermal damages on the surface of a silicon wafer induced by a near-infrared laser

Laser-induced thermal damages of a silicon wafer surface subjected to continuous near-infrared laser irradiation were investigated. Silicon wafer specimens were illuminated by a continuous-wave fiber laser beam (1070-nm wavelength) with irradiances from 93 to 186 W/cm 2 , and the surface morphology of each specimen was analyzed using optical microscopy. With increasing irradiance, straight cracks in the <110> direction appeared first, and partial melting and complete melting were subsequently observed. The mechanism of these laser-induced thermal damages in the silicon wafer surface was discussed with numerical analysis based on the heat transfer and thermoelasticity model. The irradiances initiating the cracking and melting were predicted by determining the irradiances in which the calculated thermal stress and temperature exceeded the corresponding limits of the fracture strength and melting point, respectively. These predictions agreed well with the experimental findings. Laser-induced thermal damages of the silicon wafer surface subjected to a continuous near-infrared laser irradiation were identified based on these investigations.

The electrophysiological properties of voltage-gated potassium channels on cultivated porcine retinal ganglion cells irradiated with continuous near-infrared laser

To investigate the influence of continuous near-infrared (CNI) laser to potassium ion channels on retinal ganglion cell (RGC). Experiment study. Porcine RGC was cultured with enzymatic digestion method in vitro by taking off the retina from the piglets. Whole-cell patch clamp mode recordings were obtained from primary cultured porcine RGC. Whole-cell currents of porcine RGC irradiated with a single-mode CNI laser of 845 nm wavelength and 30 mW power were also recorded. The primary cultured porcine RGC were divided into laser irradiation group and control group according to whether they accepted CNI laser of 845 nm wavelength. t test was used to analyze the average peak amplitude between the two groups. The cells had the morphological characteristics of typical neurons after one week cultured observed by inverted phase contrast microscope. The body and bumps with yellow-green fluorescence was positive cell which observed by immune cell fluorescence chemical testing. CNI laser had a regulation on outward potassium current of porcine RGC in a voltage-dependent manner. There was significant difference on the average peak amplitude of potassium current between the laser irradiation group [(634.4 ± 86.8) Pa] and the control group [(580.5 ± 116.4) Pa], respectively (n = 30, t = 7.923, P = 0.000). CNI laser can change the properties of outward K(+) channel. Therefore, formation and releasing of action potential is affected. Further, physiological functions of RGC are regulated, which might contribute to the protection and restoration of injured RGC. It can be provided a new scholar direction for the protection of the RGC, which are injured by glaucoma.

Fundamental Examination of Nanoparticle Heating Kinetics Upon Near Infrared (NIR) Irradiation

Near infrared (NIR) light, which spans wavelengths from ~700-1100 nm holds particular promise in bionanotechnology-enabled applications because both NIR light and nanoparticles (NPs) have the potential for remote activation leading to exquisite localization and targeting scenarios. In this study, aqueous solutions of carbon and metal-based NPs (carbon black, single-walled carbon nanotubes, silver nanoparticles and copper nanoparticles) were exposed to continuous NIR laser (λ = 1064 nm) irradiation at powers of 2.2W and 4.5W. The differential heating of bulk aqueous suspension of NPs with varying physicochemical properties revealed maximum temperatures of 67 °C with visible evidence of condensation and bubble formation. The basis of the NP heating is due to the strong intrinsic optical absorbance in the NIR spectral window and the transduction of this NIR photon energy into thermal energy. In this regard, UV-vis measurements can accurately predict NP heating kinetics prior to NIR irradiation. Further, a uniform thermodynamic heating model demonstrates close agreement with the experimental data for the low NIR-absorbing NPs. However, the uniform thermodynamic heating model used in this study does not accurately portray the energy release upon localized NP heating because of bubble formation for the highly absorbing NPs. Therefore, this study reveals the differential heating kinetics of NPs excited with NIR with implications in the development of novel NIR-NP-based systems.

Temperature-dependent Activation of Neurons by Continuous Near-infrared Laser

Optical control of neuronal activity has a number of advantages over electrical methods and can be conveniently applied to intact individual neurons in vivo. In this study, we demonstrated an experimental approach in which a focused continuous near-infrared (CNI) laser beam was used to activate single rat hippocampal neurons by transiently elevating the local temperature. Reversible changes in the amplitude and kinetics of neuronal voltage-gated Na and K channel currents were recorded following irradiation with a single-mode 980 nm CNI-laser. Using single-channel recordings under controlled temperatures as a means of calibration, it was estimated that temperature at the neuron rose by 14 degrees C in 500 ms. Computer simulation confirmed that small temperature changes of about 5 degrees C were sufficient to produce significant changes in neuronal excitability. The method should be broadly applicable to studies of neuronal activity under physiological conditions, in particular studies of temperature-sensing neurons expressing thermoTRP channels.

Laser-Driven Microsecond Temperature Cycles Analyzed by Fluorescence Polarization Microscopy

We demonstrate a novel technique to achieve fast thermal cycles of a small sample (a few femtoliters). Modulating a continuous near-infrared laser focused on a metal film, we can drive the local temperature from 130 to 300 K and back, within a few microseconds. By fluorescence microscopy of dyes in a thin glycerol film, we record images of the hot spot, calibrate its temperature, and follow its variations in real time. The temperature dependence of fluorescence anisotropy, due to photophysics and rotational diffusion, gives a steady-state temperature calibration between 200 and 350 K. From 200 to 220 K, we monitor temperature more accurately by fluorescence autocorrelation, a probe for rotational diffusion. Time-resolved measurements of fluorescence anisotropy give heating and cooling times of a few microseconds, short enough to supercool pure water. We designed our method to repeatedly cycle a single (bio)molecule between ambient and cryostat temperatures with microsecond time resolution. Successive measurements of a structurally relevant variable will decompose a dynamical process into structural snapshots. Such temperature-cycle experiments, which combine a high time resolution with long observation times, can thus be expected to yield new insights into complex processes such as protein folding.