Cancer stem cells (CSCs) are the main culprits involved in therapy resistance and disease recurrence in colorectal carcinoma (CRC). Results using cell culture, animal models and tissues from patients with CRC suggest the indispensable roles of colorectal CSCs in therapeutic failure. Conventional therapies target proliferating and mature cancer cells, while CSCs are mostly quiescent and poorly differentiated, thereby they can easily survive chemotherapeutic insults. The aberrant activation of Wnt/β-catenin, Notch, Hedgehog, Hippo/YAP (Yes-associated protein) and phosphatidylinositol 3-kinase/protein kinase B facilitates CSCs with excessive self-renewal and therapy resistance property in CRC. CSCs survive the chemo-radiotherapies by escaping therapy mediated DNA damage via altering the cell cycle checkpoints, increasing DNA damage repair capacity and by an efficient scavenging of reactive oxygen species. Furthermore, dysregulations of miRNAs e.g., miR-21, miR-93, miR-203, miR-215, miR-497 etc., modulate the therapeutic sensitivity of colorectal CSCs by regulating growth and survival signalling. In addition, a reversible quiescent G0 state and the re-entering cell cycle capacity of colorectal CSCs can accelerate tumour regeneration after treatment. Moreover, switching to favourable metabolic signatures during a therapeutic regimen will add more complexity in therapeutic outcomes against CSCs. Therapeutic strategies targeting these underlying mechanisms of CSCs’ therapy resistance could provide a promising outcome, however, deep understanding and concerted research are necessary to design novel therapies targeting CSCs. To conclude, the understanding of these mechanisms of CSC in CRC could lead to the improved management of patients with CRC.

We report the spatial maps of the localized surface plasmon resonances associated photon emission in a truncated tetrahedral gold nanoparticle on a silicon substrate. Site-specific cathodoluminescence spectroscopy and imaging in a scanning electron microscope shows stronger photon emission in the visible range near the tips of the particle in contact with the substrate compared to the edges of the particle. Strong local field variations on a length scale as short as 19 nm are resolved. We also perform FDTD simulations of both the spectra and, for the first time, the full cathodoluminescence images. Excellent agreement is obtained with the experimental results, and the detailed information available from the simulated results makes it possible to identify the signature of out-of-plane higher order modes in the truncated tetrahedral gold particle.

Employing cathodoluminescence (CL) spectroscopy and imaging in a field emission gun (FEG) scanning electron microscope (SEM), we study localized surface plasmon (LSP) modes on individual tilted gold nanodecahedron sitting on a silicon substrate. We experimentally resolve three distinct LSP modes in the far-field radiation acquired via CL. The experimental spectra and intensity maps of plasmon modes are in excellent agreement with the spectra and 2D-CL image obtained from finite difference time domain (FDTD) simulations. Detail analysis reveals the signature of a quadrupolar surface plasmon mode in addition to the two dipolar modes along azimuthal and polar direction of the decahedron. The experimental method and the theoretical formalism presented here provide useful insight into the plasmonic behavior of complex shaped metal nanoparticle supported by a high index substrate.

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We performed cathodoluminescence (CL) spectroscopy and imaging in a high-resolution scanning electron microscope to locally and selectively excite and investigate the plasmonic properties of a multi-branched gold nanostar on a silicon substrate. This method allows us to map the local density of optical states from the nanostar with a spatial resolution down to a few nanometers. We resolve, both in the spatial and spectral domain, different plasmon modes associated with the nanostar. Finite-difference time-domain (FDTD) numerical simulations are performed to support the experimental observations. We investigate the effect of the substrate on the plasmonic properties of these complex-shaped nanostars. The powerful CL-FDTD combination helps us to understand the effect of the substrate on the plasmonic response of branched nanoparticles.