Although apoptosis and necrosis have distinct features, the identification and discrimination of apoptotic and necrotic cell death in vitro is challenging. Immunocytological and biochemical assays represent the current gold standard for monitoring cell death pathways; however, these standard assays are invasive, render large numbers of cells and impede continuous monitoring experiments. In this study, both room temperature (RT)-induced apoptosis and heat-triggered necrosis were analyzed in individual Saos-2 and SW-1353 cells by utilizing Raman microspectroscopy. A targeted analysis of defined cell death modalities, including early and late apoptosis as well as necrosis, was facilitated based on the combination of Raman spectroscopy with fluorescence microscopy. Spectral shifts were identified in the two cell lines that reflect biochemical changes specific for either RT-induced apoptosis or heat-mediated necrosis. A supervised classification model specified apoptotic and necrotic cell death based on single cell Raman spectra. To conclude, Raman spectroscopy allows a non-invasive, continuous monitoring of cell death, which may help shedding new light on complex pathophysiological or drug-induced cell death processes.

The extracellular matrix (ECM) is extensively remodeled in tumor tissues. Overproduction of collagens, pathological collagen crosslinking and alignment of fibers are major processes that ultimately result in an increased tissue stiffness. Although it is known that glycosaminoglycans (GAGs) play an important role in tumor signaling, their contribution to the biomechanical properties of tumor ECM is unknown. In this study, ECM structures of human colon carcinoma and normal (control) colon tissues were histologically identified. Using atomic force microscopy (AFM) nanoindentation, we show that the collagen-rich regions within the ECM of colon carcinoma tissues were significantly stiffer than the submucosal collagen-rich layer of control tissues. Screening of these regions with Raman microspectroscopy revealed significantly different molecular fingerprints for collagen fibers in colon carcinoma tissues compared to control tissues. We further showed an increased alignment of collagen fibers and elevated levels of GAG immuno-reactivity within the collagen network of colon carcinoma tissues. GAGs such as heparan sulfate and chondroitin sulfate were detected in significantly elevated levels in collagen fibers of carcinoma tissues. Moreover, immunodetection of the collagen-associated proteoglycan decorin was significantly decreased in carcinomas tissues of individual patients when compared with the corresponding control tissues. Overall a strong patient-to-patient variability was evident in the ECM composition, structure and biomechanics of individual colon carcinoma tissues. Although, biomechanical characteristics of tumor ECM were not directly impacted by GAG content, GAGs might play an important role during the mechanical and structural remodeling of pathological tumor ECM. To manipulate GAG expression and deposition in tumor microenvironments could represent a novel potential therapeutic strategy.

Electroconductive substrates are emerging as promising functional materials for biomedical applications. Here, the development of biohybrids of collagen and pristine graphene that effectively harness both the biofunctionality of the protein component and the increased stiffness and enhanced electrical conductivity (matching native cardiac tissue) obtainable with pristine graphene is reported. As well as improving substrate physical properties, the addition of pristine graphene also enhances human cardiac fibroblast growth while simultaneously inhibiting bacterial attachment (Staphylococcus aureus). When embryonic-stem-cell-derived cardiomyocytes (ESC-CMs) are cultured on the substrates, biohybrids containing 32 wt% graphene significantly increase metabolic activity and cross-striated sarcomeric structures, indicative of the improved substrate suitability. By then applying electrical stimulation to these conductive biohybrid substrates, an enhancement of the alignment and maturation of the ESC-CMs is achieved. While this in vitro work has clearly shown the potential of these materials to be translated for cardiac applications, it is proposed that these graphene-based biohybrid platforms have potential for a myriad of other applications-particularly in electrically sensitive tissues, such as neural and neural and musculoskeletal tissues.