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Cellular expression of the 70 kDa heat shock protein (HSP-70) is observed following hyperthermia and is correlated with transient resistance to subsequent heating. Photodynamic therapy (PDT) mediated oxidative stress can also induce transcriptional and translational expression of a variety of genes including HSP-70. However, PDT-mediated HSP-70 expression can vary as a function of photosensitizer type and incubation conditions. In the current study we used three clinically relevant photosensitizers, a porphyrin (Photofrin), a purpurin (SnET2), and a chlorin (NPe6), to examine PDT-mediated HSP-70 expression profiles and photosensitivity characteristics in parental radiation-induced fibrosarcoma cells (RIF-1) and in thermal resistant RIF-1 clones. We observed that in vitro PDT treatments using either SnET2 or NPe6 induced HSP-70 expression but that comparable PDT treatments using Photofrin did not result in increased HSP-70 levels. We also observed that PDT sensitivity in parental and heat-resistant cell clones were similar for each photosensitizer while thermal sensitivity was significantly reduced in the RIF clones which constitutively overexpressed HSP-70. These results indicate that definable differences can exist in the molecular pathways induced by PDT for different photosensitizers. Our results also demonstrate that constitutive overexpression of HSP-70 does not modulate PDT photosensitivity regardless of whether PDT treatments induce HSP-70 expression. We conclude that HSP-70 expression does not play a significant role in cellular PDT photosensitivity.

Kava is one of the most widely sold herbal dietary supplements in the United States. It has been reported that, besides exhibiting hepatotoxicity, kava also possesses photosensitivity and induces dermopathy in humans. In this study, we determined that UVA irradiation of kava in the presence of a lipid, methyl linoleate, generated lipid peroxidation which was mediated by singlet oxygen generated during photoirradiation. The six major kavalactones(yangonin, 7,8-dihydrokawa in, kawain, 7,8-dihydromethysticin, methysticin, and 5,6-dehydrokawain) were also studied in parallel; only 5,6-dehydrokawain and yangonin-induced a low level of lipid peroxidation. UVA irradiation of kava in human HaCaT skin keratinocytes induced cytotoxicity which was mediated by oxidative stress, led to DNA strand cleavage, and produced 8-hydroxy-2′-deoxyguanosine (8-OHdG) adduct. Study by the electron spin resonance (ESR) method revealed that UVA irradiation of kava produced singlet oxygen and carbon-centered radicals. The overall results suggest that kava is photocytotoxic and photogenotoxic, both mediated by free radicals generated during photoirradiation.

In this study, an ${\mathrm{\text{In}}}_{1-x}{\mathrm{\text{Ga}}}_x\mathrm{\text{As}}$ nanowire metal oxide semiconductor field effect transistor (MOSFET) photosensor with zinc oxide (metallic ZnO), which act as a transparent optical window over channel has been investigated. The electrical characterization of ${\mathrm{\text{In}}}_{1-x}{\mathrm{\text{Ga}}}_x\mathrm{\text{As}}$ nanowire MOSFET was compared to their silicon counterpart. ${\mathrm{\text{In}}}_{1-x}{\mathrm{\text{Ga}}}_x\mathrm{\text{As}}$ nanowire MOSFET responds to visible-near infrared (600 nm to 1.7 nm) under light illumination as opposite to silicon nanowire MOSFET, which respond to ultraviolet to visible spectra (Peak @ 400 nm). ZnO–${\mathrm{\text{SiO}}}_2$–InGaAs device is characterized by responsivity $(R_{\lambda })$ of $0.25{\mathrm{\text{A W}}}^{-1}$, photoconductive gain of $65\times 10^5$%, with reasonable available photocurrent of $\times 10^8$ and sensitivity $(I_{\mathrm{\text{illumination}}}/I_{\mathrm{\text{dark}}})$ of $\times 10^6$. The present work demonstrates the potential for high performance visible to near-infrared ${\mathrm{\text{In}}}_{1-x}{\mathrm{\text{Ga}}}_x\mathrm{\text{As}}$ detectors with tunable band gaps for applications like interactive display, indoor communication and optical sensors.

A detailed study of photosensitivity and noise characteristics of ultrafast InGaAsP/InP avalanche photodiodes (APDs) with separate absorption, grading, charge and multiplication regions was carried out. Carrier multiplication and noise factors were evaluated. Noise origin in investigated APDs is 1/f, generation-recombination and shot noises. Different quality samples have been investigated and it is shown that noise characteristics well reflect APD quality problems. It is shown that low-frequency noise and excess shot noise characteristics are very sensitive to the APD quality problems and clear up physical processes in device structure. Noise characteristic analyses can be used for the APD quality problems revealing and optimal design development.

To obtain an optimum absorption layer based on hydrogenated polymorphous and nanocrystalline silicon thin films in a plasma-enhanced chemical vapor deposition, radio frequency (RF) power was varied from 25W to 100W using a mixture of dichlorosilane and hydrogen. By Raman spectroscopy, the crystalline fraction was found to be varied from 7% to 69%, and RF power value of 75W was found to be suitable with an appropriate mixture of amorphous and crystalline phases, respectively. Thickness measurements performed by profilometry were cross-checked with the value obtained from the cross-sectional scanning electron microscopy micrographs. Micrographs obtained using high-resolution transmission electron microscopy confirmed the presence of silicon nanocrystals in the range of 2–5nm with a strong probability of confinement effect. B and gap value of 1.55eV at 75W upheld the suitability of this particular RF power for active absorption layer, which has also shown maximum photosensitivity.

The proposed design uses Quantum Dots (QDs) and basic MEMS fabrication techniques to create a flexible thin-film optical heart rate sensor. Fields including health sciences, fitness sciences and psychophysiological studies can benefit from a biosensor that detects heart rate (HR) in a noninvasive manner. Optical heart rate sensors achieve this by being able to collect signals simply through contact with the user. While the sensing method itself is nothing new, the nature of the flexible thin-film structure will allow the device to achieve maintained unobtrusive contact with minimal effort.

The ZnO film prepared by doctor blade method are highly porous in presence of structure directing agent PEG and then can be easily sensitized by various molecules. In the present work, the nanostructured ZnO/dye hybrid film prepared by doctor blade method has been investigated in conductivity and photoconductivity measurements in view of applications in dye-sensitized solar cells (DSSC) and in optoelectronics, since electron transport in these devices plays a decisive role for the electron collection efficiency and therefore for the overall efficiency. The absorption of ZnO film sensitized by Rose Bengal dye (RB) has been studied by UV spectroscopy which indicates that after the dye is adsorbed on the ZnO electrode, its absorption spectra showed red-shift in the peak position compared to the absorbance spectra of dye in ethanol. Highly porous ZnO films are found to have high dark conductivity, probably because of a higher n-doping, which is due to higher concentration of Zn atoms in the film. On the other hand, ZnO/RB hybrid film is found to show a much higher sensitivity to illumination with visible light in photoconductivity measurements due to a higher absolute photoconductivity and lower conductivity in the dark.

Enhanced photosensitivity has been observed in hydrogen-loaded tin-phosphosilicate fibres by using a 248 nm excimer laser. Isothermal measurements up to 860 K demonstrated significant advantages over fibre gratings written in conventional H-loaded fibres. Gratings written in this fibre require a considerably shorter post-fabrication thermal annealing in order to satisfy the stability requirements of telecom components.