Removal of biofilms by impinging water droplets

The process of impinging water droplets on Streptococcus mutans biofilms was studied experimentally and numerically. Droplets were experimentally produced by natural breakup of a cylindrical liquid jet. Droplet diameter and velocity were varied between 20 and 200¿µm and between 20 and 100 m/s, respectively. The resulting erosion process of the biofilm was determined experimentally with high-speed recording techniques and a quantitative relationship between the removal rate, droplet size, and velocity was determined. The shear stress and the pressure on the surface during droplet impact were determined by numerical simulations, and a qualitative agreement between the experiment and the simulation was obtained. Furthermore, it was shown that the stresses on the surface are strongly reduced when a water film is present

Pulsed heat shocks to enhance collagen production of human dermal fibroblasts in ex vivo skin

No abstract

Mechanical properties and failure of Streptococcus mutans biofilms, studied using a microindentation device

Knowledge of mechanical properties and failure mechanisms of biofilms is needed to determine how biofilms react on mechanical stress. Methods currently available cannot be used to determine mechanical properties of biofilms on a small scale with high accuracy. A novel microindentation apparatus in combination with a confocal microscope was used to determine the viscoelastic properties of Streptococcus mutans biofilms. The apparatus comprises a small glass indenter and a highly sensitive force transducer. It was shown that the present biofilm, grown under still conditions, behaves as a viscoelastic solid with a storage modulus of 1–8 kPa and a loss modulus of 5–10 kPa at a strain of 10%. Biofilm failure was investigated visually through a confocal microscope by dragging the indenter through the biofilm. It was shown that the tensile strength of the biofilm is predominantly determined by the tensile strength of the extracellular polysaccharide matrix. The combination of microindentation and confocal microscopy is a promising technique to determine and characterize the mechanical properties of soft materials in various fields of microbiology

Heat shocks enhance procollagen type I and III expression in fibroblasts in ex-vivo human skin

Keywords:human skin;fibroblasts;heat shock;procollagen;rejuvenation Background: The well-known characteristics of aging skin are the development of fine lines and wrinkles, but changes in skin tone, skin texture, thickness and moisture content are also aspects of aging. Rejuvenation of the skin aims at reversing the signs of aging and can be established in the epidermis as well as in the dermis. Aged dermis, in fact, has a degenerated collagen matrix. To regenerate this matrix, fibroblasts need to be stimulated into synthesizing new collagen. Aims: In this study, the effects of heat shocks of different temperatures on human dermal fibroblasts in ex vivo skin on the expression of procollagen 1, procollagen 3, heat shock protein (hsp)27, hsp47, and hsp70 are investigated. Materials and methods: The heat shocks were applied on ex vivo skin samples by immersing the samples in heated phosphate-buffered saline of 45 °C or 60 °C. Metabolic activity was measured and at similar time points propidium–iodide–calceine staining was performed to establish cell viability. Quantitative polymerase chain reaction (qPCR) was performed after the heat shock to determine gene expression levels relative to the reference temperature. Furthermore, PicroSirius Red and hematoxylin stainings were performed to visualize the collagen network and the cells. Results: The skin samples were shown to be viable and metabolically active. Histology indicated that the heat shocks did not influence the structure of the collagen network or cell appearance. qPCR results showed that in contrast to the 45 °C heat shock the 60 °C heat shock resulted in significant upregulations of procollagen type I and III, hsp70 and hsp47. Conclusion: A 60 °C, heat shock stimulates the human dermal fibroblasts in ex vivo skin to upregulate their procollagen type I and type III expression

Pulsed heat shocks to enhance collagen production of human dermal fibroblasts in ex vivo skin

No abstract

Excitation transfer in chlorosomes of green photosynthetic bacteria

The formation of excited states and energy transfer in chlorosomes of the green photosynthetic bacteria Chlorobium limicola and Chloroflexus aurantiacus were studied by measurements of flash-induced absorbance changes and fluorescence. Upon excitation with 35 ps, 532 nm flashes, large absorbance decreases around 750 nm were observed that were due to the disappearance of ground state absorption of the main pigment, bacteriochlorophyll (BChl) c. The absorbance changes decayed after the flash with a time constant of approx. 1 ns, together with faster components. Absorbance changes that could be ascribed to formation of excited BChl a were much smaller than those of BChl c. The yields of BChl c and BChl a fluorescence were measured as a function of the energy density of the exciting flash. At high energy a strong quenching occurred caused by annihilation of singlet excited states. An analysis of the results shows that energy transfer between BChl c molecules is very efficient and that in C. limicola excitations can probably move freely through the entire chlorosome (which contains about 10 000 BChls c). The chlorosome thus serves as a common antenna for several reaction centres. The small amounts of BChl a present in the chlorosomes of both species form clusters of only a few molecules. Upon cooling to 4 K the sizes of the domains of BChl c for energy transfer decreased considerably. The results are discussed in relation to recently suggested models for the pigment organization within chlorosomes

Clinical, biophysical, immunohistochemical, and in vivo reflectance confocal microscopy evaluation of the response of subjects with sensitive skin to home-use fractional non-ablative photothermolysis device

BACKGROUND: Fractional photothermolysis using professional devices is a well-accepted and a widely used technique for skin rejuvenation. Recently, the technology has also been implemented in devices for home-use. Yet, a subpopulation of consumers exists that reacts excessively to this stimulation and reports "sensitive skin" (SS). OBJECTIVE: The goal of this study was to evaluate the response of subjects with SS and NSS to fractional non-ablative photothermolysis to provide additional insights in the pathophysiology of SS. METHODS: Subjects with SS and non-sensitive skin (NSS), selected using a proprietary questionnaire were stimulated by applying a home-use fractional non-ablative photothermolysis device. Self-reported perceptions and objective effects were evaluated after 0.5, 8, 24, and 72 hours by clinical, biophysical and immunohistochemical assessment, and in vivo reflectance confocal microscopy (RCM). RESULTS: Significantly fewer mast cells were found in SS compared to NSS subjects, 0.5 and 72 hours after stimulus based on tryptase staining, and SS subjects report discomfort more frequently. Immunohistochemical biomarkers revealed new insights in the effects of fractional non-ablative photothermolysis, which were supported by RCM: peri- and interlesional epidermal proliferation, and changes in keratinocyte differentiation. CONCLUSION: Previously, we have already reported that SS could be elicited by mechanical and chemical stimuli. Thus, mild yet excessive self-reported perceptions described here supports the hypothesis about existence of generalized skin sensitivity. Furthermore, it supports a view point suggesting involvement of TRPV1 receptors in this phenomenon. While histological evaluation, in line with our previous results points to the role of mast cells in SS, overall, however, fractional non-ablative photothermolysis causes only mild damage, nearly equal in SS and NSS and could be used as an in vivo model for skin regeneration without manipulating the skin barrier. Lasers Surg. Med. 48:474-482, 2016. (c) 2016 Wiley Periodicals, Inc