Multiple Responsiveness of Polymer Actuators.

To improve photosensitivity of polymer materials, an effective protocol is to increase the content of photosensitive moieties. However, most of photosensitive units are toxic. The high content is not acceptable for real-world applications. Therefore, achieving photosensitive polymers with low content of photosensitive moieties but maintaining their photosensitivity remains a challenge. Herein, a protocol is reported to address this challenge by combining photosensitive monomers with hygroscopic monomers, where the synergistic action of two types of functional moieties can improve the photosensitivity of polymer network. Upon exposure to light irradiation, the polymer can be driven by not only the structural isomerization of photosensitive units, but also the photothermal effects. This synergistic effect results in the polymer-based soft actuators capable of showing rapid response to light even at the extremely-low content of photosensitive moieties of 2.6 mol.%. Importantly, the combination of hygroscopic and photosensitive moieties provides polymer with multiple responsiveness including acidochromism, humidity responsiveness, photohardening, shape memory, photochromism, and in situ swelling, making it useful in sensing systems, information transmission, and artificial muscles.

Frequency of occurrence of polymorphic light eruption in patients treated with photohardening and patients treated with phototherapy for other diseases.

BACKGROUND: Medical phototherapy can lead to the manifestation of polymorphic light eruption (PLE), though little is known about the frequency of such events. AIMS: The aim of this Austrian single center study was to retrospectively investigate over a 4-year time period the frequency of PLE in patients prone to the condition and patients with other diseases under phototherapy (mainly narrow-band and broad-band UVB). MATERIALS AND METHODS: The data for analysis were obtained from the electronic health and patient record database and patient files of the Photodermatology Unit, Department of Dermatology, Medical University of Graz, Austria. RESULTS: PLE occurred in 24.3% (18/74) of PLE patients but only 0.7% (3/421) of psoriasis patients under phototherapy (chi-square; P < 0.0001). PLE also occurred in 1.2% (3/257) of patients with atopic eczema, 0.8% (1/118) with prurigo, 3.5% (4/115, P = 0.0206) with parapsoriasis en plaques/mycosis fungoides, 7.4% (2/27, P = 0.0013) with granuloma anulare, 14.3% (1/7, P = 0.0002) with scleroderma, and 16.7% (1/6, P < 0.0001 vs. psoriasis) with pityriasis lichenoides chronica or pityriasis lichenoides eruptiva et varioliformis acuta. DISCUSSION AND CONCLUSION: These results are helpful for treatment allocation and risk estimation of PLE occurrence with regard to obtaining informed consent not only from PLE-prone patients but also from patients with other skin disorders commonly treated by phototherapy.

Mast cells are required for phototolerance induction and scratching abatement.

Dermal mast cells protect the skin from inflammatory effects of ultraviolet (UV) radiation and are required for UV-induced immune suppression. We sought to determine a potential mechanistic role of mast cells in reducing the sensitivity to UV radiation (i.e. phototolerance induction) through photohardening. We administered single UV exposures as well as a chronic UV irradiation regime to mast cell-deficient Kit(W-Sh/W-Sh) mice and their controls. The chronic irradiation protocol was similar to that given for prophylaxis in certain photodermatoses in humans. Compared to controls, UV-exposed Kit(W-Sh/W-Sh) mice were more susceptible to epidermal hyperplasia and dermal oedema which was linked to blood vessel dilation. Unexpectedly, Kit(W-Sh/W-Sh) mice exhibited an excessive scratching behaviour following broadband UVB plus UVA or solar simulated UV irradiation at doses far below their minimal skin-swelling dose. Protection from this UV-induced scratching phenotype was dependent on mast cells, as engraftment of bone marrow-derived cultured mast cells abated it entirely. Kit(W-Sh/W-Sh) mice were entirely resistant to phototolerance induction by photohardening treatment. Compared to controls, these mice also showed reduced numbers of regulatory T cells and neutrophils in the skin 24 h after UV irradiation. While it is well known that mast cell-deficient mice are resistant to UV-induced immune suppression, we have discovered that they are prone to develop photo-itch and are more susceptible to UV-induced epidermal hyperplasia and skin oedema.