Ultrasonic modulation of tissue optical properties in ex vivo porcine skin to improve transmitted transdermal laser intensity.

BACKGROUND AND OBJECTIVE: Applications of light-based energy devices involving optical targets within the dermis frequently experience negative side-effects resultant from surface scattering and excess optical absorption by epidermal melanin. As a broadband optical absorber, melanin decreases the efficacy of light-based treatments throughout the ultraviolet, visible, and near-infrared spectra while also generating additional heat within the surface tissue that can lead to inflammation or tissue damage. Consequently, procedures may be performed using greater energy densities to ensure that the target receives a clinically relevant dose of light; however, such practices are limited, as doing so tends to exacerbate the detrimental complications resulting from melanin absorption of treatment light. The technique presented herein represents an alternative method of operation aimed at increasing epidermal energy fluence while mitigating excess absorption by unintended chromophores. The approach involves the application of continuously pulsed ultrasound to modulate the tissue's optical properties and thereby improve light transmission through the epidermis. MATERIALS AND METHODS: To demonstrate the change in optical properties, pulsed light at a wavelength of 532 nm from a Q-switched Nd:YAG laser was transmitted into 4 mm thick samples of porcine skin, comprised of both epidermal and dermal tissue. The light was transmitted using an optical waveguide, which allowed for an ultrasonic transducer to be incorporated for simultaneous paraxial pulsation in parallel with laser operation. Light transmitted through the tissue was measured by a photodiode attached to an integrating sphere. RESULTS: Increasing the driving voltage of ultrasonic pulsation resulted in an increase in mean transmitted optical power of up to a factor of 1.742 ± 0.0526 times the control, wherein no ultrasound was applied, after which the optical power increase plateaued to an average amplification factor of 1.733 ± 0.549 times the control. CONCLUSIONS: The increase implies a reduction in light either back-scattered or absorbed within the tissue, which would allow for a greater proportion of incident energy to be delivered to the clinical target, thereby improving procedural efficacy and potentially reducing the severity of detrimental side-effects. Apparatus Lasers Surg. Med. 49:666-674, 2017. © 2017 Wiley Periodicals, Inc.

Evanescent Field Based Photoacoustics: Optical Property Evaluation at Surfaces.

Here, we present a protocol to estimate material and surface optical properties using the photoacoustic effect combined with total internal reflection. Optical property evaluation of thin films and the surfaces of bulk materials is an important step in understanding new optical material systems and their applications. The method presented can estimate thickness, refractive index, and use absorptive properties of materials for detection. This metrology system uses evanescent field-based photoacoustics (EFPA), a field of research based upon the interaction of an evanescent field with the photoacoustic effect. This interaction and its resulting family of techniques allow the technique to probe optical properties within a few hundred nanometers of the sample surface. This optical near field allows for the highly accurate estimation of material properties on the same scale as the field itself such as refractive index and film thickness. With the use of EFPA and its sub techniques such as total internal reflection photoacoustic spectroscopy (TIRPAS) and optical tunneling photoacoustic spectroscopy (OTPAS), it is possible to evaluate a material at the nanoscale in a consolidated instrument without the need for many instruments and experiments that may be cost prohibitive.

Photoacoustic measurement of refractive index of dye solutions and myoglobin for biosensing applications.

Current methods of determining the refractive index of chemicals and materials, such as ellipsometry and reflectometry, are limited by their inability to analyze highly absorbing or highly transparent materials, as well as the required prior knowledge of the sample thickness and estimated refractive index. Here, we present a method of determining the refractive index of solutions using the photoacoustic effect. We show that a photoacoustic refractometer can analyze highly absorbing dye samples to within 0.006 refractive index units of a handheld optical refractometer. Further, we use myoglobin, an early non-invasive biomarker for malignant hyperthermia, as a proof of concept that this technique is applicable for use as a medical diagnostic. Comparison of the speed, cost, simplicity, and accuracy of the techniques shows that this photoacoustic method is well-suited for optically complex systems.

A physical and chemical comparison of material from a conventional spray-dried system and a single particle spray-dried system.

When assessing the suitability of potential drug/polymer systems for improving drug bioavailability, substantial efficiency gains can be achieved through the development and application of rapid miniaturised screening methods. For this to be possible new methods of small-scale formulation manufacture that produce materials equivalent to full-scale manufacture are urgently required. In this work, we use Atomic Force Microscopy (AFM) and Confocal Raman Microscopy (CRM) to investigate the potential physical and chemical equivalence of individually dried particles generated using a DRYING KINETICS ANALYZER™ (DKA) with material from a conventional spray-drier. For our model system of griseofulvin (at loadings of 2.5%, w/w and 20%, w/w) and PEG 6000, the results demonstrate physicochemical equivalence between the two spray-drying methods for the same drug loading. Thus we suggest that single particle spray drying offers a viable and novel route to the production of materials for miniaturised methods of screening candidate drug/polymer formulations.

Nanoparticle mediated thermal ablation of breast cancer cells using a nanosecond pulsed electric field.

In the past, ablation of cancer cells using radiofrequency heating techniques has been demonstrated, but the current methodology has many flaws, including inconsistent tumor ablation and significant ablation of normal cells. Other researchers have begun to develop a treatment that is more selective for cancer cells using metallic nanoparticles and constant electric field exposure. In these studies, cell necrosis is induced by heating antibody functionalized metallic nanoparticles attached to cancer cells. Our approach to studying this phenomenon is to use similarly functionalized metallic nanoparticles that are specific for the T47D breast cancer cell line, exposing these nanoparticle cell conjugates to a nanosecond pulsed electric field. Using fluorescent, polystyrene-coated, iron-oxide nanoparticles, the results of our pilot study indicated that we were able to ablate up to approximately 80% of the cells using 60 ns pulses in increasing numbers of pulses and up to approximately 90% of the cells using 300 ns pulses in increasing numbers of pulses. These quantities of ablated cells were achieved using a cumulative exposure time 6 orders of magnitude less than most in vitro constant electric field studies.

Photoacoustic spectroscopy of ß-hematin.

Malaria affects over 200 million individuals annually, resulting in 800,000 fatalities. Current tests use blood smears and can only detect the disease when 0.1-1% of blood cells are infected. We are investigating the use of photoacoustic flowmetry to sense as few as one infected cell among 10 million or more normal blood cells, thus diagnosing infection before patients become symptomatic. Photoacoustic flowmetry is similar to conventional flow cytometry, except that rare cells are targeted by nanosecond laser pulses to induce ultrasonic responses. This system has been used to detect single melanoma cells in 10 ml of blood. Our objective is to apply photoacoustic flowmetry to detection of the malaria pigment hemozoin, which is a byproduct of parasite-digested hemoglobin in the blood. However, hemozoin is difficult to purify in quantities greater than a milligram, so a synthetic analog, known as ß-hematin was derived from porcine haemin. The specific purpose of this study is to establish the efficacy of using ß-hematin, rather than hemozoin, for photoacoustic measurements. We characterized ß-hematin using UV-vis spectroscopy, TEM, and FTIR, then tested the effects of laser irradiation on the synthetic product. We finally determined its absorption spectrum using photoacoustic excitation. UV-vis spectroscopy verified that ß-hematin was distinctly different from its precursor. TEM analysis confirmed its previously established nanorod shape, and comparison of the FTIR results with published spectroscopy data showed that our product had the distinctive absorbance peaks at 1661 and 1206 cm(-1). Also, our research indicated that prolonged irradiation dramatically alters the physical and optical properties of the ß-hematin, resulting in increased absorption at shorter wavelengths. Nevertheless, the photoacoustic absorption spectrum mimicked that generated by UV-vis spectroscopy, which confirms the accuracy of the photoacoustic method and strongly suggests that photoacoustic flowmetry may be used as a tool for diagnosis of malaria infection.

Total internal reflection photoacoustic spectroscopy for the detection of ß-hematin.

Evanescent field sensing methods are currently used to detect many different types of disease markers and biologically important chemicals such as the HER2 breast cancer receptor. Hinoue et al. used Total Internal Reflection Photoacoustic Spectroscopy (TIRPAS) as a method of using the evanescent field to detect an optically opaque dye at a sample interface. Although their methods were successful at detecting dyes, the results at that time did not show a very practical spectroscopic technique, which was due to the less than typical sensitivity of TIRPAS as a spectroscopy modality given the low power (≈ 1 to 2 W) lasers being used. Contrarily, we have used an Nd:YAG laser with a five nanosecond pulse that gives peak power of 1 MW coupled with the TIRPAS system to increase the sensitivity of this technique for biological material sensing. All efforts were focused on the eventual detection of the optically absorbing material, hemozoin, which is created as a byproduct of a malarial infection in blood. We used an optically analogous material, ß-hematin, to determine the potential for detection in the TIRPAS system. In addition, four properties which control the sensitivity were investigated to increase understanding about the sensor's function as a biosensing method.

High loading efficiency and sustained release of siRNA encapsulated in PLGA nanoparticles: quality by design optimization and characterization.

Poly(DL-lactide-co-glycolide acid) (PLGA) is an attractive polymer for delivery of biopharmaceuticals owing to its biocompatibility, biodegradability and outstanding controlled release characteristics. The purpose of this study was to understand and define optimal parameters for preparation of small interfering RNA (siRNA)-loaded PLGA nanoparticles by the double emulsion solvent evaporation method and characterize their properties. The experiments were performed according to a 2(5-1) fractional factorial design based on five independent variables: The volume ratio between the inner water phase and the oil phase, the PLGA concentration, the sonication time, the siRNA load and the amount of acetylated bovine serum albumin (Ac-BSA) in the inner water phase added to stabilize the primary emulsion. The effects on the siRNA encapsulation efficiency and the particle size were investigated. The most important factors for obtaining an encapsulation efficiency as high as 70% were the PLGA concentration and the volume ratio whereas the size was mainly affected by the PLGA concentration. The viscosity of the oil phase was increased at high PLGA concentration, which explains the improved encapsulation by stabilization of the primary emulsion and reduction of siRNA leakage to the outer water phase. Addition of Ac-BSA increased the encapsulation efficiency at low PLGA concentrations. The PLGA matrix protected siRNA against nuclease degradation, provided a burst release of surface-localized siRNA followed by a triphasic sustained release for two months. These results enable careful understanding and definition of optimal process parameters for preparation of PLGA nanoparticles encapsulating high amounts of siRNA with immediate and long-term sustained release properties.

In vitro evaluation of cell proliferation and collagen synthesis on titanium following plasma electrolytic oxidation.

Titania-based coatings produced by plasma electrolytic oxidation are being investigated as bioactive surfaces for titanium implants. In this study, plasma electrolytic oxidation was performed in calcium- and phosphorus-based electrolytes under DC conditions, resulting in coatings of thickness of approximately 8-15 mum. Coating morphologies, microstructures, and compositions were examined by scanning electron microscopy with energy-dispersive X-ray analysis, X-ray diffraction, and electron probe microanalysis. The coatings revealed a cratered morphology, with incorporated calcium and phosphorus species. Proliferation rates of primary human osteoblasts cells on the coatings were up to approximately 37% faster than those for uncoated titanium and 316L stainless steel reference materials. Further, the coatings assisted cell adhesion and generation and anchorage of collagen. The amount of collagen was upto approximately 2.4 times greater than for the reference substrates. (c) 2010 Wiley Periodicals, Inc. J Biomed Mater Res, 2010.

Detection of low levels of amorphous lactose using H/D exchange and FT-Raman spectroscopy.

PURPOSE: To demonstrate the potential of monitoring H/D exchange by FT-Raman spectroscopy as a tool for the detection and quantification of low levels of amorphous lactose in formulations. METHODS: Samples containing different proportions of amorphous and crystalline lactose were prepared. H/D exchange was carried out by exposing the samples to a flow of D(2)O vapour. A calibration curve was constructed from the FT-Raman spectra of the deuterated samples by integrating the nu(OD) band and normalizing to an internal standard. This method was benchmarked against a conventional approach using Raman spectroscopy where the ratio of Raman bands associated with crystalline and amorphous lactose is used to estimate the amorphous content. RESULTS: The H/D exchange method revealed a linear response over the entire composite range with an excellent correlation coefficient (R (2) = 0.999). The sensitivity of this approach in detecting the amount of amorphous lactose present in a blend is significantly greater than that offered by conventional FT-Raman in the 0-10% level of amorphous material. CONCLUSIONS: A non-destructive method that is capable of providing reproducible measurements of low levels of amorphous material in lactose has been demonstrated and this method has enhanced sensitivity relative to approaches using Raman spectroscopy without deuteration.

Photoelectron spectroscopy of S1 toluene: I. Photoionization propensities of selected vibrational levels in S1 toluene.

Laser photoelectron spectra have been obtained following the preparation of eight vibrational states in S(1) toluene. For four of the vibrational states (up to approximately 550 cm(-1) excess energy) excitation and ionization with nanosecond laser pulses give rise to photoelectron spectra with well-resolved vibrational peaks. For the other states (>750 cm(-1) excess energy) the photoelectron spectra show a loss of structure when nanosecond pulses are used, as a result of intramolecular dynamics [see Whiteside et al., J. Chem. Phys. 123, 204317 (2005), following paper]. A number of vibrational peaks in the photoelectron spectra are assigned, and we find that the common series of ion vibrational peaks observed following the ionization of p-fluorotoluene in various S(1) vibrational states is not reproduced in toluene.

Photoelectron spectroscopy of S1 toluene: II. Intramolecular dynamics of selected vibrational levels in S1 toluene studied by nanosecond and picosecond time-resolved photoelectron spectroscopies.

We present results which suggest that the photophysics of S(1) toluene is significantly more complicated than that of the related molecules p-fluorotoluene or p-difluorobenzene. We have measured a range of photoelectron spectra for a number of S(1) internal energies, on different time scales and at different temperatures, in an attempt to unravel the competing processes, but the final conclusion remains outstanding.

An unusual pi* shape resonance in the near-threshold photoionization of S1 para-difluorobenzene.

Previously reported dramatic changes in photoelectron angular distributions (PADs) as a function of photoelectron kinetic energy following the ionization of S1 p-difluorobenzene are shown to be explained by a shape resonance in the b(2g) symmetry continuum. The characteristics of this resonance are clearly demonstrated by a theoretical multiple-scattering treatment of the photoionization dynamics. New experimental data are presented which demonstrate an apparent insensitivity of the PADs to both vibrational motion and prepared molecular alignment, however, the calculations suggest that strong alignment effects may nevertheless be recognized in the detail of the comparison with experimental data. The apparent, but unexpected, indifference to vibrational excitation is rationalized by considering the nature of the resonance. The correlation of this shape resonance in the continuum with a virtual pi* antibonding orbital is considered. Because this orbital is characteristic of the benzene ring, the existence of similar resonances in related substituted benzenes is discussed.