Emerging clinical applications in oncology for non‐invasive multi‐ and hyperspectral imaging of cell and tissue autofluorescence

Abstract

Hyperspectral and multispectral imaging of cell and tissue autofluorescence is an emerging technology in which fluorescence imaging is applied to biological materials across multiple spectral channels. This produces a stack of images where each matched pixel contains information about the sample's spectral properties at that location. This allows precise collection of molecularly specific data from a broad range of native fluorophores. Importantly, complex information, directly reflective of biological status, is collected without staining and tissues can be characterised in situ, without biopsy. For oncology, this can spare the collection of biopsies from sensitive regions and enable accurate tumour mapping. For in vivo tumour analysis, the greatest focus has been on oral cancer, whereas for ex vivo assessment head‐and‐neck cancers along with colon cancer have been the most studied, followed by oral and eye cancer. This review details the scope and progress of research undertaken towards clinical translation in oncology.

Towards label‐free non‐invasive autofluorescence multispectral imaging for melanoma diagnosis

“…The transformation of a normal cell into a cancerous one tends to be accompanied by changes and dysfunctions in cell metabolism [25]. A common phenomenon with cancer cells is the Warburg effect, where aerobic glycolysis and glucose uptake are increased, and this has a role in cancer cell proliferation [26–28]. The metabolic fingerprint of a cell can be reflected through native fluorophores present within the cell, making them potentially valuable biomarkers [29].…”

“…The metabolic fingerprint of a cell can be reflected through native fluorophores present within the cell, making them potentially valuable biomarkers [29]. Essential autofluorescent co‐enzymes contributing to the cell metabolism include nicotinamide adenine dinucleotide (NAD(P)H) and flavins [26, 30, 31]. The native fluorescence signal of NAD(P)H has excitation maxima at 290 and 351 nm and emission maxima at 440 and 460 nm [26].…”

“…Essential autofluorescent co‐enzymes contributing to the cell metabolism include nicotinamide adenine dinucleotide (NAD(P)H) and flavins [26, 30, 31]. The native fluorescence signal of NAD(P)H has excitation maxima at 290 and 351 nm and emission maxima at 440 and 460 nm [26]. The autofluorescent emission of flavin adenine dinucleotide (FAD), an important flavins representative, peaks at 535 nm induced by 450 nm excitation light [26].…”

“…The native fluorescence signal of NAD(P)H has excitation maxima at 290 and 351 nm and emission maxima at 440 and 460 nm [26]. The autofluorescent emission of flavin adenine dinucleotide (FAD), an important flavins representative, peaks at 535 nm induced by 450 nm excitation light [26]. These native fluorophores have been used to monitor metabolic processes due to their involvement in cellular respiration [32].…”

“…These native fluorophores have been used to monitor metabolic processes due to their involvement in cellular respiration [32]. In particular, the optical redox ratio (here defined as the ratio of the optical signals of flavins and NAD(P)H) can reflect the activity of the electron transport chain and ATP production [26, 33]. Changes in these fluorophores and the redox ratio may indicate a dysregulated cellular metabolism typical in cancer, and therefore, have high potential to be useful in oncology applications [26].…”