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We fabricate and experimentally characterize a broadband fractal acoustic metamaterial that can serve to attenuate the low-frequency sounds at selective frequencies ranging from 225 to 1175 Hz. The proposed metamaterials are constructed by the periodic Hilbert fractal elements made of photosensitive resin via 3D printing. In analogy to electromagnetic fractal structures, it is shown that multiple resonances can also be excited in the acoustic counterpart due to their self-similar properties, which help to attenuate the acoustic energy in a wide spectrum. The confinement of sound waves in such subwavelength element is evidenced by both numerical and experimental results. The proposed metamaterial may provide possible alternative for various applications such as the noise attenuation and the anechoic materials.

Controllable modification of biological molecules and supramolecular components of connective tissue are important for biophysical and biomedical applications. Through the use of second harmonic generation imaging, two-photon fluorescence microscopy, and spectrofluorimetry, we found that hypericin, a natural pigment, induces photosensitized destruction of collagen fibers but does not affect elastic fibers and lipids in chicken tendon, skin, and blood vessels. We demonstrated the dynamics and efficiency of collagen photomodification and investigated mechanisms of this processes. Our results suggest that hypericin–mediated photoprocesses in biological tissues may be useful in biomedical applications that require selective modification of connective tissues.

In this letter, we propose an efficient methodology of investigating dynamic properties of sulforhodamine B and rhodamine B hexyl ester molecules transporting across ex-vivo human stratum corneum with and without oleic acid enhancement. Three-dimensional, time-lapse fluorescence images of the stratum corneum can be obtained using two-photon fluorescence microscopy. Furthermore, temporal quantifications of transport enhancements in diffusion parameters can be achieved with the use of Fick's second law. Dynamic characterization of solutes transporting across the stratum corneum is an effective method for understanding transient phenomena in transdermal delivery of probe molecules, leading to improved delivery strategies of molecular species for therapeutic purposes.

Transdermal delivery of nanocarriers provides an alternative pathway to transport therapeutic agents, alleviating pain, improving compliance of patients, and increasing overall effectiveness of delivery. In this work, enhancement of transdermal delivery of fluorescent nanoparticles and sulforhodamine B with assistance of oleic acid was visualized utilizing multiphoton microscopy (MPM) and analyzed quantitatively using multi-photon excitation-induced fluorescent signals. Results of MPM imaging and MPM intensity-based spatial depth-dependent analysis showed that oleic acid is effective in facilitating transdermal delivery of nanoparticles.

Using multiphotonautofluorescence (MAF) and second harmonic generation(SHG)microscopy, we investigate the morphology and the structure of the corneal epithelium and stroma collagen of bovine cornea following injection of Pseudomonas aeruginosa. We found that corneal epithelial cells are damaged and stromal collagen becoming increasingly autofluorescent with time. We also characterized infected cornea cultured for 0, 6, 12, and 24 h by quantitative ratiometric MAF to SHG index (MAFSI) analysis. MAFSI results show that the destruction of the stromal collagen corresponds to a decrease in SHG intensity and increase of MAF signal with time.

We performed intravital multiphoton microscopy to image and analyze normal and carcinogen treated skintissues of nude mice in vivo. Using intravital images and the quantitative pixel to pixel ratiometric processing of multiphotonautofluorescence to second harmonic generation index (MAFSI), we can visualize the interaction between epithelial cells and extracellular matrix. We found that as the imaging depth increases, MAFSI has different distribution in normal and treated cutaneous specimens. Since the treated skin eventually became squamous cellcarcinoma, our results show that the physiological changes to mouse skin en route to become cancer can be effectively tracked by multiphoton microscopy.

We performed multiphoton excited autofluorescence and second harmonic generationmicroscopy for the distinction of normal, lung adenocarcinoma (LAC), and squamous cell carcinoma (SCC) specimens. In addition to morphological distinction, we derived quantitative metrics of cellular redox ratios for cancer discrimination. Specifically, the redox ratios of paired normal/SCC and normal/LAC specimens were found to be 0.53 ± 0.05 / 0.41 ± 0.06 and 0.56 ± 0.02 / 0.35 ± 0.06 , respectively. The lower redox ratios in cancer specimens, indicating an increase in metabolic activity. These results show that the combination of morphological multiphotonimaging along with redox ratio indices can be used for the discrimination of normal and pulmonary cancertissues.

Conventional diagnosis for hepatocellular carcinoma (HCC) is time consuming in sample preparation and deficient in quantitative examination. In this work, we developed multiphoton autofluorescence (MAF) microscopy as an effective and efficient tool in HCC diagnosis with qualitative imaging and quantitative measurement. We found that MAF imaging effectively identifies cellular architecture in the liver specimens. Our results also demonstrate the capability of using tissue quantitative parameters of multiphoton autofluorescence intensity ratio, the nuclear number density, and nuclear-cytoplasmic ratio for tumor discrimination. This approach has the potential in clinical diagnosis of HCC and the in vivo investigation of liver tumor development in animal models.

Through monitoring the evolution of the x-ray diffraction peaks, the transient low temperature melting of Au nanoparticles and following alloying with the substrate were demonstrated via in situ synchrotron radiation x-ray diffraction. Upon heating, the broad diffraction peak of nanosized Au particles with the average diameter of 2.5 nm was suppressed at about 200 °C and soon became sharp due to melting and subsequent solidification. If the test was conducted on a Ni film, an unstable intermetallic compound Au3Ni appeared with crystallized Au, which resulted from the reaction between the supercooled liquid of Au and Ni. However, it decomposed at 275 °C and above.

We performed multiphotonimaging on fungi of medical significance. Fungal hyphae and spores of Aspergillus flavus, Micosporum gypseum, Micosoprum canis, Trichophyton rubrum, and Trichophyton tonsurans were found to be strongly autofluorescent but generate less prominent second harmonic signal. The cell wall and septum of fungal hyphae can be easily identified by autofluorescenceimaging. We found that fungi of various species have distinct autofluorescence characteristics. Our result shows that the combination of multiphotonimaging and spectralanalysis can be used to visualize and identify fungal species. This approach may be developed into an effective diagnostic tool for fungal identification.

Time-lapse second harmonic generation (SHG) microscopy was applied for the extraction of thermodynamic parameters of collagen thermal denaturation. We found that at sufficiently high temperatures, temporal dependence of SHG intensity from the isothermal treatment of chicken dermal collagen was single exponential and can be modeled by the Arrhenius equation. Activation energy and the frequency factor of chicken dermal collagen thermal denaturation were determined using temporal decays of SHG intensity at different temperatures. Our results show that time-lapse, high temperature SHG imaging can be used to quantify kinetic properties of collagen thermal denaturation within a microscopic volume of 1 nl.

Important biological molecules such as collagen and myosin are strong second harmonic generators. The polarization dependence of second-harmonic generation(SHG) is a property of the second order susceptibility elements ( χ tensor) of the molecules that produce the signal. In this work, we used polarizationSHGmicroscopy to image and map pixel scale polarization anisotropy information of collagen-muscle junction of chicken wing and the dermis of human skin. We show that the variation in the χ tensor components can be displayed as images to show the contrast between different molecular sources of SHG.