FT-IR Analysis of P. aeruginosa Bacteria Inactivation by Femtosecond IR Laser Radiation.

We report the successful inactivation of P. aeruginosa strain by femtosecond infrared (IR) laser radiation at the resonant wavelengths of 3.15 µm and 6.04 µm, chosen due to the presence of characteristic molecular vibrations in the main structural elements of the bacterial cells in these spectral ranges: vibrations of amide groups in proteins (1500-1700 cm-1), and C-H vibrations in membrane proteins and lipids (2800-3000 cm-1). The underlying bactericidal structural molecular changes were revealed by the stationary Fourier-transform IR spectroscopy, with the spectral peaks parameters being obtained by Lorentzian fitting with the hidden peaks revealed by the second derivative calculations, while no visible damage to the cell membranes was identified by scanning and transmission electron microscopy.

Standoff Detection and Identification of Liquid Chemicals on a Reflective Substrate Using a Wavelength-Tunable Quantum Cascade Laser.

Standoff chemical detection and identification techniques are necessary for ensuring safe exposure to dangerous substances. Molecular fingerprints of unknown chemicals can be measured using wavelength-tunable quantum cascade lasers operating in long-wavelength infrared. In this work, we present a method that can identify liquid chemicals on a reflective substrate via diffuse reflection spectra measurement from 50 cm away and multiple nonlinear regression analysis. Experimental measurements and numerical analyses were conducted for different chemical surface densities and angles of light incidence using diethyl phthalate (DEP) and dimethyl methylphosphonate (DMMP). Candidate substances can be classified using a deep learning model to reduce analysis time.

Utilizing Laser Activation of Photothermal Plasmonic Nanoparticles to Induce On-Demand Drug Amorphization inside a Tablet.

Poor aqueous drug solubility represents a major challenge in oral drug delivery. A novel approach to overcome this challenge is drug amorphization inside a tablet, that is, on-demand drug amorphization. The amorphous form is a thermodynamically instable, disordered solid-state with increased dissolution rate and solubility compared to its crystalline counterpart. During on-demand drug amorphization, the drug molecularly disperses into a polymer to form an amorphous solid at elevated temperatures inside a tablet. This study investigates, for the first time, the utilization of photothermal plasmonic nanoparticles for on-demand drug amorphization as a new pharmaceutical application. For this, near-IR photothermal plasmonic nanoparticles were tableted together with a crystalline drug (celecoxib) and a polymer (polyvinylpyrrolidone). The tablets were subjected to a near-IR laser at different intensities and durations to study the rate of drug amorphization under each condition. During laser irradiation, the plasmonic nanoparticles homogeneously heated the tablet. The temperature was directly related to the rate and degree of amorphization. Exposure times as low as 180 s at 1.12 W cm-2 laser intensity with only 0.25 wt % plasmonic nanoparticles and up to 50 wt % drug load resulted in complete drug amorphization. Therefore, near-IR photothermal plasmonic nanoparticles are promising excipients for on-demand drug amorphization with laser irradiation.

The Effect of the Molecular Weight of Polyvinylpyrrolidone and the Model Drug on Laser-Induced In Situ Amorphization.

Laser radiation has been shown to be a promising approach for in situ amorphization, i.e., drug amorphization inside the final dosage form. Upon exposure to laser radiation, elevated temperatures in the compacts are obtained. At temperatures above the glass transition temperature (Tg) of the polymer, the drug dissolves into the mobile polymer. Hence, the dissolution kinetics are dependent on the viscosity of the polymer, indirectly determined by the molecular weight (Mw) of the polymer, the solubility of the drug in the polymer, the particle size of the drug and the molecular size of the drug. Using compacts containing 30 wt% of the drug celecoxib (CCX), 69.25 wt% of three different Mw of polyvinylpyrrolidone (PVP: PVP12, PVP17 or PVP25), 0.25 wt% plasmonic nanoaggregates (PNs) and 0.5 wt% lubricant, the effect of the polymer Mw on the dissolution kinetics upon exposure to laser radiation was investigated. Furthermore, the effect of the model drug on the dissolution kinetics was investigated using compacts containing 30 wt% of three different drugs (CCX, indomethacin (IND) and naproxen (NAP)), 69.25 wt% PVP12, 0.25 wt% PN and 0.5 wt% lubricant. In perfect correlation to the Noyes-Whitney equation, this study showed that the use of PVP with the lowest viscosity, i.e., the lowest Mw (here PVP12), led to the fastest rate of amorphization compared to PVP17 and PVP25. Furthermore, NAP showed the fastest rate of amorphization, followed by IND and CCX in PVP12 due to its high solubility and small molecular size.

Combinatorial screening of halide perovskite thin films and solar cells by mask-defined IR laser molecular beam epitaxy.

As an extension of combinatorial molecular layer epitaxy via ablation of perovskite oxides by a pulsed excimer laser, we have developed a laser molecular beam epitaxy (MBE) system for parallel integration of nano-scaled thin films of organic-inorganic hybrid materials. A pulsed infrared (IR) semiconductor laser was adopted for thermal evaporation of organic halide (A-site: CH3NH3I) and inorganic halide (B-site: PbI2) powder targets to deposit repeated A/B bilayer films where the thickness of each layer was controlled on molecular layer scale by programming the evaporation IR laser pulse number, length, or power. The layer thickness was monitored with an in situ quartz crystal microbalance and calibrated against ex situ stylus profilometer measurements. A computer-controlled movable mask system enabled the deposition of combinatorial thin film libraries, where each library contains a vertically homogeneous film with spatially programmable A- and B-layer thicknesses. On the composition gradient film, a hole transport Spiro-OMeTAD layer was spin-coated and dried followed by the vacuum evaporation of Ag electrodes to form the solar cell. The preliminary cell performance was evaluated by measuring I-V characteristics at seven different positions on the 12.5 mm × 12.5 mm combinatorial library sample with seven 2 mm × 4 mm slits under a solar simulator irradiation. The combinatorial solar cell library clearly demonstrated that the energy conversion efficiency sharply changes from nearly zero to 10.2% as a function of the illumination area in the library. The exploration of deposition parameters for obtaining optimum performance could thus be greatly accelerated. Since the thickness ratio of PbI2 and CH3NH3I can be freely chosen along the shadow mask movement, these experiments show the potential of this system for high-throughput screening of optimum chemical composition in the binary film library and application to halide perovskite solar cell.

Ultrafast extraction of proteins from tissues using desorption by impulsive vibrational excitation.

A picosecond IR laser (PIRL) can be used to blast proteins out of tissues through desorption by impulsive excitation (DIVE) of intramolecular vibrational states of water molecules in the cell in less than a millisecond. With PIRL-DIVE proteins covering a range of a few kDa up to several MDa are extracted in high quantities compared to conventional approaches. The chemical composition of extracted proteins remains unaltered and even enzymatic activities are maintained.

Manipulation of cell membrane using carbon nanotube scaffold as a photoresponsive stimuli generator.

We describe, for the first time, the perforation of the cell membrane in the targeted single cell based on the nanosecond pulsed near-infrared (NIR) laser irradiation of a thin film of carbon nanotubes that act as an effective photon absorber as well as stimuli generator. When the power of NIR laser is over 17.5 µJ/pulse, the cell membrane after irradiation is irreversibly disrupted and results in cell death. In sharp contrast, the perforation of the cell membrane occurs at suitable laser power (∼15 µJ/pulse) without involving cell termination.

Self-oscillating Water Chemiluminescence Modes and Reactive Oxygen Species Generation Induced by Laser Irradiation; Effect of the Exclusion Zone Created by Nafion.

Samples of water inside and outside an exclusion zone (EZ), created by Nafion swollen in water, were irradiated at the wavelength l = 1264 nm, which stimulates the electronic transition of dissolved oxygen from the triplet state to the excited singlet state. This irradiation induces, after a long latent period, chemiluminescence self-oscillations in the visible and near UV spectral range, which last many hours. It occurs that this effect is EZ-specific: the chemiluminescence intensity is twice lower than that from the bulk water, while the latent period is longer for the EZ. Laser irradiation causes accumulation of H2O2, which is also EZ-specific: its concentration inside the EZ is less than that in the bulk water. These phenomena can be interpreted in terms of a model of decreasing O2 content in the EZ due to increased chemical activity of bisulfite anions (HSO3-), arisen as the result of dissociation of terminal sulfonate groups of the Nafion. The wavelet transform analysis of the chemiluminescence intensity from the EZ and the bulk water gives, that self-oscillations regimes occurring in the liquid after the latent period are the determinate processes. It occurred that the chemiluminescence dynamics in case of EZ is characterized by a single-frequency self-oscillating regime, whereas in case of the bulk water, the self-oscillation spectrum consists of three spectral bands.

Laser-assembled conductive 3D nanozyme film-based nitrocellulose sensor for real-time detection of H2O2 released from cancer cells.

In this work, a nanostructured conductive film possessing nanozyme features was straightforwardly produced via laser-assembling and integrated into complete nitrocellulose sensors; the cellulosic substrate allows to host live cells, while the nanostructured film nanozyme activity ensures the enzyme-free real-time detection of hydrogen peroxide (H2O2) released by the sames. In detail, a highly exfoliated reduced graphene oxide 3D film decorated with naked platinum nanocubes was produced using a CO2-laser plotter via the simultaneous reduction and patterning of graphene oxide and platinum cations; the nanostructured film was integrated into a nitrocellulose substrate and the complete sensor was manufactured using an affordable semi-automatic printing approach. The linear range for the direct H2O2 determination was 0.5-80 µM (R2 = 0.9943), with a limit of detection of 0.2 µM. Live cell measurements were achieved by placing the sensor in the culture medium, ensuring their adhesion on the sensors' surface; two cell lines were used as non-tumorigenic (Vero cells) and tumorigenic (SKBR3 cells) models, respectively. Real-time detection of H2O2 released by cells upon stimulation with phorbol ester was carried out; the nitrocellulose sensor returned on-site and real-time quantitative information on the H2O2 released proving useful sensitivity and selectivity, allowing to distinguish tumorigenic cells. The proposed strategy allows low-cost in-series semi-automatic production of paper-based point-of-care devices using simple benchtop instrumentation, paving the way for the easy and affordable monitoring of the cytopathology state of cancer cells.

One-Step Laser Nanostructuration of Reduced Graphene Oxide Films Embedding Metal Nanoparticles for Sensing Applications.

The combination of two-dimensional materials and metal nanoparticles (MNPs) allows the fabrication of novel nanocomposites with unique physical/chemical properties exploitable in high-performance smart devices and biosensing strategies. Current methods to obtain graphene-based films decorated with noble MNPs are cumbersome, poorly reproducible, and difficult to scale up. Herein, we propose a straightforward, versatile, surfactant-free, and single-step technique to produce reduced graphene oxide (rGO) conductive films integrating "naked" noble MNPs. This method relies on the instantaneous laser-induced co-reduction of graphene oxide and metal cations, resulting in highly exfoliated rGO nanosheets embedding gold, silver, and platinum NPs. The production procedure has been optimized, and the obtained nanomaterials are fully characterized; the hybrid nanosheets have been easily transferred onto lab-made screen-printed electrodes preserving their nanoarchitecture. The Au@rGO-, Ag@rGO-, and Pt@rGO-based electrodes have been challenged to detect caffeic acid, nitrite, and hydrogen peroxide in model solutions and real samples. The sensors yielded quantitative responses (R2 ≥ 0.997) with sub-micromolar limits of detections (LODs ≤ 0.6 µM) for all the analytes, allowing accurate quantification in samples (recoveries ≥ 90%; RSD ≤ 14.8%, n = 3). This single-step protocol which requires low cost and minimal equipment will allow the fabrication of free-standing, MNP-embedded rGO films integrable into a variety of scalable smart devices and biosensors.

IRMPD spectroscopy and quantum-chemical simulations of the reaction products of cisplatin with the dipeptide CysGly.

The inorganic antineoplastic drug cisplatin was made to react in solution with the dipeptide cysteinylglycine (CysGly), chosen as a functional model of glutathione, and the reaction products were analyzed using electrospray ionization mass spectrometry (ESI-MS). Selected complexes, i.e., the primary substitution product cis-[PtCl(NH3)2(CysGly)]+ and the chelate cis-[PtCl(NH3)(CysGly)]+, were submitted to IR multiple photon dissociation (IRMPD) spectroscopy obtaining their vibrational features. The experimental IR ion spectra were compared with the calculated IR absorptions of different plausible isomeric families, finding CysGly to bind preferentially platinum(II) via its deprotonated thiolic group in the monovalent complex, cis-[PtCl(NH3)2(CysGly)]+, and to evolve in the S,N-bound chelate structure cis-[PtCl(NH3)(CysGly)]+ through the SH and NH2 functionality of the cysteine residue. Moreover, our findings indicate that the platination reaction does not affect the CysGly peptide bond, which remains in its trans configuration. These results provide additional insights into the reactivity of Pt(II)-complexes with glutathione which is involved in cellular cisplatin resistance.

Elusive intermediates in cisplatin reaction with target amino acids: Platinum(II)-cysteine complexes assayed by IR ion spectroscopy and DFT calculations.

The reactivity of a widely used metal based antineoplastic drug, cisplatin, cis-PtCl2(NH3)2, with L-cysteine (Cys) has been investigated using a combination of electrospray ionization mass spectrometry (ESI-MS), IRMPD gas phase ion spectroscopy and DFT calculations. The cysteine lateral chain represents one of the main platination sites in proteins, which is believed to be related to the resistance mechanisms to cisplatin. The vibrational features of the mass-selected substitution product cis-[PtCl(NH3)2(Cys)]+ and the intercepted cis-[PtCl(NH3)2(H2O)(Cys)]+ intermediate complex were compared to calculated IR spectra, enabling the assessment of the sampled ions structures. In cis-[PtCl(NH3)2(Cys)]+, cysteine was found to bind platinum through the sulfur atom as a thiolate zwitterion, highlighting the enhanced acidity of the cysteine thiol group upon metal coordination. The cis-[PtCl(NH3)2(H2O)(Cys)]+ structure complies with the non-covalent encounter complex, formed by cis-[PtCl(NH3)2(H2O)]+ and neutral cysteine. This species is able to undergo the substitution process to produce cis-[PtCl(NH3)2(Cys)]+ when activated as a mass-isolated ion suggesting its participation in the reaction mechanism of cisplatin with cysteine in solution. Finally, the DFT-calculated energy profile for the substitution reaction was correlated with the peculiar gas-phase reactivity of this non-covalent complex, resulting to be 10-fold less reactive toward substitution than the corresponding methionine complex.

Development of compact CW-IR laser deposition system for high-throughput growth of organic single crystals.

We developed a compact continuous-wave infrared (CW-IR) laser deposition system for the high-throughput growth of organic single crystals. In this system, two CW-IR lasers are used for the sample heating and thermal evaporation of materials. The CW-IR laser heating is simple and allows good control of the deposition rate and growth temperature, in response to the on/off laser switching. Six samples can be loaded simultaneously in a chamber, which allows one-by-one sequential deposition for high-throughput experiments, without breaking the vacuum. Using this setup, we studied the effect of ionic liquids on the growth of C60 crystals in vacuum.

High-throughput CW-IR laser deposition and laser microscope imaging of binary ionic liquids in vacuum.

A combinatorial library of binary mixtures of ionic liquids with various mixing ratios was fabricated on a single sapphire substrate using the composition-spread technique combined with a continuous-wave infrared (CW-IR) laser deposition method; the mixtures were condensed in the form of micro-scale droplets. The mixing ratio within the droplets was examined by Raman spectroscopy. The contact angle of the droplets was found to systematically vary with the mixing ratio. Their thermal behavior was characterized with an ultrahigh-vacuum laser microscope, revealing the dependence of the evaporation rate on the mixing ratio.

Gas-phase hydration of the lysozyme ion produced by infrared-laser ablation of a droplet beam studied by photodissociation and fluorescence spectroscopy.

Biomolecules function in an aqueous environment. Elucidation of the hydration structures of biomolecules is hence important to understand their functions. Here, we investigated the hydration structure of lysozyme (Lys) in the gas phase by photodissociation and fluorescence spectroscopy in combination with droplet-beam laser ablation mass spectrometry. We found that water molecules are held inside and on the surface of the Lys molecule, and the hydration structure around the tryptophan residue changes by photoexcitation. This study provides a novel method to observe the hydration structures of large biomolecules at the molecular level.

Fabrication of a Chalcogenide Glass Microlens Array for Infrared Laser Beam Homogenization.

Infrared (IR) microlens arrays (MLA) have attracted increasing interest for use in infrared micro-optical devices and systems. However, the beam homogenization of IR laser light is relatively difficult to achieve because most materials absorb strongly in the IR wavelength band. In this paper, we present a new method for the application of double-sided quasi-periodic chalcogenide glass (ChG) MLAs to infrared laser homogenization systems. These are non-regular arrays of closely spaced MLAs. The double-sided MLAs were successfully prepared on the ChG surface using a single-pulse femtosecond laser-assisted chemical etching technique and a precision glass molding technique. More than two million close-packed microlenses on the ChG surface were successfully fabricated within 200 min. By taking advantage of ChG's good optical performance and transmittance (60%) in the infrared wavelength band (1~11 µm), the homogenization of the IR beam was successfully achieved using the ChG quasi-periodic MLA.

Surface Superconductivity Changes of Niobium Sheets by Femtosecond Laser-Induced Periodic Nanostructures.

Irradiation with ultra-short (femtosecond) laser beams enables the generation of sub-wavelength laser-induced periodic surface structures (LIPSS) over large areas with controlled spatial periodicity, orientation, and depths affecting only a material layer on the sub-micrometer scale. This study reports on how fs-laser irradiation of commercially available Nb foil samples affects their superconducting behavior. DC magnetization and AC susceptibility measurements at cryogenic temperatures and with magnetic fields of different amplitude and orientation are thus analyzed and reported. This study pays special attention to the surface superconducting layer that persists above the upper critical magnetic field strength Hc2, and disappears at a higher nucleation field strength Hc3. Characteristic changes were distinguished between the surface properties of the laser-irradiated samples, as compared to the corresponding reference samples (non-irradiated). Clear correlations have been observed between the surface nanostructures and the nucleation field Hc3, which depends on the relative orientation of the magnetic field and the surface patterns developed by the laser irradiation.

Muscle Recovery Is Highlighted by IR Laser Therapy.

Introduction: In sports medicine, laser application has been well-established for the recovery of muscles. The mechanisms by which benefits of this kind of therapy can be studied is molecular research approach. Protein-protein interaction network analysis as one of the important complementary studies of proteomics can accelerate this goal by the identification of novel contributing markers. Methods: By the use of Cytoscape V3.7.1 and its applications, a network of differential expressed proteins (DEPs) from IR laser treatment samples were constructed and analyzed. Six hub-bottlenecks were determined, 4 of which were from differentially expressed proteins. Results: ClueGO discovered 4 biological processes related to these hub-bottlenecks that their function could alter due to IR laser therapy. Conclusion: In fact, by the expression changes of hub-bottlenecks including the up-regulation of HSP90s, one of the prominent biological processes in muscle recovery could be activated. This process is called nitric oxide synthase (NOS) activation that could be proposed as one of the underlying mechanisms of IR laser treatments in muscle recovery.

Drug Implants of Hydrogels via Collective Behavior of Microgel Colloids for On-Demand Cancer Therapy.

In nature, the collective behaviors such as the growth of bacteria and the cooperation of insects possess great superiority and can create functional materials through diversified interactions for accomplishing complex tasks that cannot be performed by a single unit. Here we develop a new protocol for fabricating drug implants of hydrogels via the collective behavior of jagged magnetic microgels constructed by further coating Au nanorod@SiO2 with the thermo- and magnetic-responsive polymer shells, poly(N-isopropylacrylamide-co-magnetic ionic liquids). The magnetism of resultant macroscale hydrogels was enhanced nearly 5-fold because of the self-organization process, presenting new evidence for the essence of magnetism generation at a molecular level. By virtue of using a near-IR laser excitation stimulus, minimal cytotoxicity, and high biocompatibility, the implants of hydrogels not only have the potential to be local drug implants for sustaining drug release over 30 days but also achieve on-demand release for the enhanced therapeutic effect. The formation of microgel colloids provides an unprecedented strategy to rearrange molecular magnets and a unique potential and possibility for magnetism enhancement. This enhancement motivates an improvement of solid tumor therapy and also supplies a force for the real implementation of the on-demand drug treatment.

Mid-infrared pulsed laser ultrasonic testing for carbon fiber reinforced plastics.

Laser ultrasonic testing (LUT) can realize contactless and instantaneous non-destructive testing, but its signal-to-noise ratio must be improved in order to measure carbon fiber reinforced plastics (CFRPs). We have developed a mid-infrared (mid-IR) laser source optimal for generating ultrasonic waves in CFRPs by using a wavelength conversion device based on an optical parametric oscillator. This paper reports a comparison of the ultrasonic generation behavior between the mid-IR laser and the Nd:YAG laser. The mid-IR laser generated a significantly larger ultrasonic amplitude in CFRP laminates than a conventional Nd:YAG laser. In addition, our study revealed that the surface epoxy matrix of CFRPs plays an important role in laser ultrasonic generation.