BackgroundCoherent anti-Stokes Raman scattering (CARS) microscopy provides fine resolution imaging and displays morphochemical properties of unstained tissue. Here, we evaluated this technique to delineate and identify brain tumors.MethodsDifferent human tumors (glioblastoma, brain metastases of melanoma and breast cancer) were induced in an orthotopic mouse model. Cryosections were investigated by CARS imaging tuned to probe C-H molecular vibrations, thereby addressing the lipid content of the sample. Raman microspectroscopy was used as reference. Histopathology provided information about the tumor's localization, cell proliferation and vascularization.ResultsThe morphochemical contrast of CARS images enabled identifying brain tumors irrespective of the tumor type and properties: All tumors were characterized by a lower CARS signal intensity than the normal parenchyma. On this basis, tumor borders and infiltrations could be identified with cellular resolution. Quantitative analysis revealed that the tumor-related reduction of CARS signal intensity was more pronounced in glioblastoma than in metastases. Raman spectroscopy enabled relating the CARS intensity variation to the decline of total lipid content in the tumors. The analysis of the immunohistochemical stainings revealed no correlation between tumor-induced cytological changes and the extent of CARS signal intensity reductions. The results were confirmed on samples of human glioblastoma.ConclusionsCARS imaging enables label-free, rapid and objective identification of primary and secondary brain tumors. Therefore, it is a potential tool for diagnostic neuropathology as well as for intraoperative tumor delineation.

Spinal cord injury (SCI) induces complex biochemical changes, which result in inhibition of nervous tissue regeneration abilities. In this study, Fourier-transform infrared (FT-IR) spectroscopy was applied to assess the outcomes of implants made of a novel type of non-functionalized soft calcium alginate hydrogel in a rat model of spinal cord hemisection (n = 28). Using FT-IR spectroscopic imaging, we evaluated the stability of the implants and the effects on morphology and biochemistry of the injured tissue one and six months after injury. A semi-quantitative evaluation of the distribution of lipids and collagen showed that alginate significantly reduced injury-induced demyelination of the contralateral white matter and fibrotic scarring in the chronic state after SCI. The spectral information enabled to detect and localize the alginate hydrogel at the lesion site and proved its long-term persistence in vivo. These findings demonstrate a positive impact of alginate hydrogel on recovery after SCI and prove FT-IR spectroscopic imaging as alternative method to evaluate and optimize future SCI repair strategies.

Tracing aetiology and pathogenesis of urinary stone disease is of great importance in order to prescribe appropriate treatment and prevent recurrences. For this purpose, morphological examination combined with determination of chemical composition of urinary stones is fundamental. In this work, we have evaluated the potential of multimodal nonlinear optical imaging for investigation of (micro)structure and chemical composition of human urinary stones. The method provides high‐resolution multimodal images of the cross‐sectioned stones without any labelling or some other pretreatment of the samples. We have shown that various constituents of urinary stones can be well discriminated in the multimodal images according to their optical signals. In addition, small structures (1–5 µm in size) were observed in the cross‐sections of urinary stones of various types. These structures were identified as crystallites of uric acid. They could either act as an active element during formation of urinary stones or, more probably, be accidentally incorporated into their structure, as it is suggested by random distribution of the crystallites. The results of this work show that multimodal nonlinear optical imaging can provide relevant information about growth processes of urinary stones and deliver useful insights in aetiology and pathogenesis of urolithiasis. Copyright © 2016 John Wiley & Sons, Ltd.