We develop a simple but efficient self-assembled bio-sensor for biomolecular detection. This sensor employs self assembled beta- amyloid (Aβ) fibril as a template. It is designed to meet the urgent demand for early detection of diseases related biomarkers especially micro-RNA. Our design offers fast yet accurate detection (in picomolar level) of small DNA in high-throughput manner without the need of sample enrichment or amplification as traditional methods do. It also brings insight in the development of novel biomaterial-based sensors in nanoscale.