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In this paper we have used second harmonic generation (SHG) and phasor approach to auto fluorescence lifetime imaging (FLIM) to obtain fingerprints of different collagens and then used these fingerprints to observe bone marrow fibrosis in the mouse femur. This is a label free approach towards fast automatable detection of fibrosis in tissue samples. FLIM has previously been used as a method of contrast in different tissues and in this paper phasor approach to FLIM is used to separate collagen I from collagen III, the markers of fibrosis, the largest groups of disorders that are often without any effective therapy. Often characterized by an increase in collagen content of the corresponding tissue, the samples are usually visualized by histochemical staining, which is pathologist dependent and cannot be automated.

Porous silica is an attractive biomaterial in many applications, including drug-delivery systems, bone-graft fillers and medical devices. The issue with porous silica biomaterials is the rate at which they resorb and the significant role played by interfacial chemistry on the host response in vivo. This paper explores the potential of diatom-biosilica as a model tool to assist in the task of mapping and quantifying the role of surface topography and chemical cues on cell fate. Diatoms are unicellular microalgae whose cell walls are composed of, amorphous nanopatterned biosilica that cannot be replicated synthetically. Their unique nanotopography has the potential to improve understanding of interface reactions between materials and cells. This study used Cyclotella meneghiniana as a test subject to assess cytotoxicity and pro-inflammatory reactions to diatom-biosilica. The results suggest that diatom-biosilica is non-cytotoxic to J774.2 macrophage cells, and supports cell proliferation and growth. The addition of amine and thiol linkers have shown a significant effect on cytotoxicity, growth and cytokine response, thus warranting further investigation into the interfacial effects of small chemical modifications to substrate surfaces. The overall findings suggest diatom-biosilica offers a unique platform for in-depth investigation of the role played by nanotopography and chemistry in biomedical applications.

Mammalian cell membranes have different phospholipid composition and cholesterol content, displaying a profile of fluidity that depends on their intracellular location. Among the dyes used in membrane studies, LAURDAN has the advantage to be sensitive to the lipid composition as well as to membrane fluidity. The LAURDAN spectrum is sensitive to the lipid composition and dipolar relaxation arising from water penetration, but disentangling lipid composition from membrane fluidity can be obtained if time resolved spectra could be measured at each cell location. Here we describe a method in which spectral and lifetime information obtained in different measurements at the same plane in a cell are used in the phasor plot providing a solution to analyze multiple lifetime or spectral data through a common visualization approach. We exploit a property of phasor plots based on the reciprocal role of the phasor plot and the image. In the phasor analysis each pixel of the image is associated with a phasor and each phasor maps to pixels and features in the image. In this paper the lifetime and spectral fluorescence data are used simultaneously to determine the contribution of polarity and dipolar relaxations of LAURDAN in each pixel of an image.

Quantitative analysis of fluorescence signals from cells reacted with fluorescently labeled probes is a widely-used method for assessing cell biology. This method has become especially powerful for screening novel nanostructured materials for their influence on cell behavior. However, the effect of nanostructured surface on fluorescence intensity has largely been ignored, which likely leads to erroneous conclusions about cell behavior. This paper investigates this possibility by using fibroblasts cultured on nanoporous gold (np-Au) as a model nanostructured material system. We found that fibroblasts stained for f-actin using phalloidin conjugated with common fluorophores display different levels of fluorescence on np-Au, planar gold, and glass, suggesting different levels of f-actin composition. However, direct quantification via western blots indicates that the actin expression is the same across all conditions. We further investigated whether the fluorescence intensity depended on np-Au feature size, complementing the findings with reflection dark field measurements from different np-Au surfaces. Overall, our experimental measurements in agreement with our electrodynamic simulations suggest that nanostructured surfaces alter the fluorescence intensity of fluorophores by modulating both the excitation and light emission processes. We conclude that comparison of fluorescence on materials with different nanostructures should be done with a quantification method decoupled from the nanostructure's influence.