Functionalized two-dimensional nanochannel membranes to distinguish methylated/unmethylated peptides for sensing cellular G9a protein.

Histone methyltransferase G9a-catalyzed histone modifications serve as critical epigenetic marks that regulate diverse cellular functions. Aberrant enzymatic activities of G9a are closely associated with various human pathologies, making them promising biomarkers for disease diagnosis and therapeutic targeting. However, the lack of efficient assays for accurate and sensitive detection of G9a, especially in complex crude cellular extracts, limits elucidation of cancer-related mechanisms and advancements of therapeutic innovations. Here, a G9a detection system based on functionalized 2D solid-state nanochannel membranes through the specific recognition between small molecule Crown probes and dissociative peptide probes was developed. The Crown probe exhibited a strong binding force with the unmethylated peptide through hydrogen bonding, thereby altering the ion transport characteristics within the nanochannels and enabling the differentiation of methylated and unmethylated peptides followed by the detection of histone methyltransferase G9a. The excellent sensing performance enables diverse detection scenarios, including differentiation of different subtypes of breast cancer cells, screening of enzyme inhibitors and sensing of hypoxic cellular environments. This research proposed that the GO-Crown membrane could be an effective detection system for G9a, which provides a powerful tool for cancer research and clinical application.