The term “Epigenetics” was first coined in 1942 by embryologist Conrad Waddington, who described it as the “complex developmental interactions bridging genotype and phenotype.” Over the past five decades, this field has transformed significantly, reshaping our comprehension of developmental biology. Today, epigenetics is understood as the study of inheritable modifications in gene function that occur without alterations to the DNA sequence, influencing traits across generations of cells or organisms (Sophie Beaumont, 2023). Epigenetics has emerged as a transformative focus in modern biological research, revealing the limitations of solely analysing DNA sequences to fully grasp gene expression patterns and phenotypic diversity (Li, 2021). The Human Genome Project highlighted that only a fraction of genes that are active at specific times and locations, underscoring the need to explore regulatory systems that function beyond the genetic code itself. This regulatory complexity, significantly shaped by environmental factors, influences gene expression through chemical modifications that do not alter DNA sequences—a foundational principle of epigenetics (Mattick & Amaral, 2022). Recent insights into cancer’s evolution show that malignancy rarely arises from a single genetic change; instead, it typically develops gradually through a combination of genetic and epigenetic changes over years, leading to uncontrolled cell growth and, in advanced stages, metastasis (Ahmed & Kim, 2024).

Whole-genome sequencing studies, such as those from the Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, have reconstructed the evolutionary trajectories of 2658 cancers across 38 types. These studies reveal that early oncogenesis is driven by mutations in a limited number of driver genes and specific chromosomal changes (Aaltonen et al., 2020). Intriguingly, tumours undergo significant shifts in their mutational profile throughout their development, reflecting a dynamic interplay between intrinsic cellular factors and environmental influences. Statistical data indicate that different cancer types follow unique mutational timelines, with early-stage copy-number gains in glioblastomas and medulloblastomas, while in lung cancers and melanomas, such gains are more frequent in later stages (Xu et al., 2023). The latency period before a cancer diagnosis can span years; for example, ovarian cancer may progress undetected for over a decade, as mutations gradually accumulate. The tumour microenvironment also exerts selective pressures that shape cancer evolution, promoting tumour heterogeneity and influencing cellular behaviour (Nadler & Zurbenko, 2014). Understanding the integration of epigenetic factors into cancer evolution is crucial in advancing diagnostic and therapeutic approaches.

In eukaryotic cells, epigenetic mechanisms such as DNA methylation, histone modification, and non-coding RNA interactions orchestrate gene expression, DNA replication, and repair within the nuclear architecture, with profound implications for tissue-specific gene expression, chromosomal regulation, and cellular differentiation (Ameya and Sekar, 2024, Barta et al., 2016). Importantly, epigenetic modifications are not only central to normal developmental processes but are also implicated in a broad spectrum of diseases, particularly cancer, where alterations in the epigenetic landscape can lead to the abnormal expression of proto-oncogenes and the silencing of tumour suppressor genes, playing a crucial role in carcinogenesis (Feinberg, 2018). This has spurred intensive research into developing epigenetic therapies, with several targeted drugs progressing through clinical trials. Additionally, non-coding RNAs, such as microRNAs, have emerged as powerful modulators of the cancer epigenome, offering valuable insights for advancing cancer diagnostics and therapeutic strategies.

MicroRNAs (miRNAs) are small, non-coding RNA molecules, typically 21 to 23 nucleotides in length, that play essential roles in regulating gene expression across various organisms, including plants and animals (Shreya Reddy, Usman, Ganapathy, & Sekar, 2024). They are primarily involved in post-transcriptional regulation, where they bind to the 3′ untranslated regions (3′ UTRs) of target messenger RNAs (mRNAs) to induce mRNA degradation or translational repression. The discovery of the first miRNA (lin-4) in C. elegans in 1993 was followed by the identification of human miRNA let-7 in 2000, with over 2600 human mature miRNAs now documented in the miRBase database (Bhardwaj et al., 2024, Bofill-De Ros and Vang Ørom, 2024, Berumen Sánchez et al., 2021). The biogenesis of miRNAs begins with transcription from DNA into primary miRNAs (pri-miRNAs), which are processed into precursor miRNAs (pre-miRNAs) and finally mature miRNAs. This process is facilitated by the microprocessor complex, including Drosha and DGCR8, followed by export to the cytoplasm where further processing occurs before incorporation into the RNA-induced silencing complex (RISC) for gene regulation (Cardoso et al., 2016, Cannell et al., 2008).

miRNAs are recognized as significant regulators of various biological processes, including development, cell proliferation, differentiation, and apoptosis. Histone and DNA methylation are two examples of epigenetic changes that have a major impact on miRNA production. It’s interesting to note that miRNAs themselves can control epigenetic modifiers like histone deacetylases (HDACs) and DNA methyltransferases (DNMTs), forming a complicated regulatory network (Nirmaladevi, 2020). For example, miR-140 controls HDAC4. They have been implicated in numerous diseases, such as cancers and viral infections (Kang, Park, Lee, & Bae, 2024). For instance, specific miRNAs have been linked to chronic lymphocytic leukaemia and colonic adenocarcinoma. Interestingly, while miRNAs are primarily known for repressing gene expression, recent studies have shown that they can also activate gene expression under certain conditions (CastroMuñoz et al., 2023). In the context of cancer biology, most miRNAs can either be classified as oncogenes, also referred to as oncomiRs, or as tumour suppressor genes. OncomiRs are mostly present in the higher levels in cancer, and they act to repress those genes that are responsible for tumour suppression. Tumour suppressor miRNA, on the other hand, have a lower expression which results in their target oncogenes being overexpressed. Some, such as miR-7, can influence cells in only one direction acting as either an oncomiR or a tumour suppressor depending on the situation. Furthermore, the changes in expression of these miRNAs and the epigenetic modifications in association with them contribute significantly to the etiology and progression of cancer and therefore, these molecules can be used as potential targets for cancer treatment as well as biomarkers. This dual functionality allows cells to respond rapidly to environmental changes (Cavallari et al., 2021, Cavalcante et al., 2021). Moreover, many miRNAs are evolutionarily conserved across species, indicating their fundamental roles in cellular functions (Morales-Martínez & Vega, 2022).

The dynamic nature of miRNA interactions is influenced by various factors, including the availability of target mRNAs and competing endogenous RNAs. These interactions can be cooperative or competitive, allowing multiple miRNAs to regulate a set of functionally relevant genes or for different mRNAs to compete for binding to the same miRNA. This complexity highlights the importance of understanding the conditional aspects of miRNA-mediated regulation in different biological contexts (Bhardwaj et al., 2024, Chadha et al., 2022). Overall, microRNAs represent a vital component of gene regulatory networks with significant implications for health and disease management. Notably, miRNAs are recognized as important biomarkers for cancer detection and investigation owing to their stability in bodily fluids and distinctive expression profiles in tissues, including cancerous tissues (Condrat et al., 2020). Recent studies indicate that the use of miRNAs as detection markers offers valuable insights into the pathophysiological conditions of individuals afflicted with cancer (Rezayi, Farjami, Hosseini, Ebrahimi, & Abouzari-Lotf, 2019). However, conventional approaches encounter challenges in detecting ultra trace levels of miRNA in fluids due to their inherent characteristics and low concentrations. Therefore, developing more efficient and affordable emerging techniques is essential for early cancer diagnosis and therapy (Dave et al., 2019, Daniels and Pourmand, 2007). To address these challenges, ongoing research has explored different innovative techniques, including miRNA-based electrochemical biosensors for various diseases such as cancer. By leveraging the unique properties of miRNAs and the principles of biosensors, these innovative tools provide enhanced sensitivity testing. Their implementation offers promising prospects for reducing the incidence of cancer and enhancing the chances of survival.

Most biomarker testing for cancer is performed in large, centralized laboratories, leading to high costs and lengthy processing times. To improve efficiency and accessibility, there is a need for smaller, rapid, and cost-effective technologies that can provide analytical data at the point of care (POC) (El Aamri et al., 2020, Feinberg, 2018). Techniques such as electrochemical and photoelectrochemical biosensors have emerged as promising solutions due to their high sensitivity, specificity, ease of use, affordability, and quick response times and this field is enhanced by the use of nanotechnology (Dave et al., 2019, Fu et al., 2023a). Leveraging the advantages of miRNA detection and electrochemical sensing, miRNA-based biosensors offer promising potential for improving accessibility and effectiveness in cancer management, particularly for early screening and regular monitoring. These biosensors use the electrochemical properties of biomolecules to detect analytes, with recognition elements immobilized on their surface to interact with target molecules, producing a measurable signal with other advantages like potential for miniaturization (Pothipor et al., 2021a). The integration of nanotechnology has been pivotal in advancing biosensor development, leading to the creation of various nanomaterial-based sensors with enhanced sensitivity and specificity. Among these innovations, miRNA-based biosensors have attracted considerable attention for their ability to detect specific biomarkers linked to cancer progression.