A microfiber biosensor for detection of AKT protein in human embryonic kidney cell lysate based on the vernier effect

•Proposed a parallel tapered seven-core fiber biosensor based on the vernier effect for AKT protein detection.•Ultra-low limit of detection of 44 pg/mL is achieved.•Detection of AKT protein in human embryonic kidney cell lysate compared with western blotting method.•The PTSCF biosensor has great stability, ultrahigh sensitivity and excellent specificity. The AKT protein is closely related to the cancer and diabetes. Rapid detection of AKT is very important in medical diagnosis. This paper proposed a parallel connected tapered seven-core fiber (PTSCF) biosensor to utilize vernier effect to improve sensitivity. Experimental results showed that 5.99 times improvements have been achieved in the refractive index sensing in the ranges of 1.333–1.337. By functionalizing AKT-Ab on the PTSCF sensor surface, a fast detection (