In this work, we prepared four different shaped silver nanoparticles (AgNPs) (spherical, rod, hexagonal, and flower shaped) by using the green synthesis approach. The synthesized AgNPs were characterized by UV-vis spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy, which showed that AgNPs have a very narrow size distribution with visible and confined geometry and shape. The synthesized AgNPs were modified by 2-bromoisobutyryl bromide, developed as a nanoinitiator, and then used for the synthesis of phenformin-imprinted polymers (MIP@AgNPs). A comparative study was performed between different shaped MIP-modified AgNPs; in addition, the effect of AgNPs on electrocatalytic activity, surface area, adsorption capacity, and electrochemical and photoluminescence sensing of phenformin was also explored. Among the different shaped MIP@AgNPs, the anisotropic AgNPs have multiple facets and planes, i.e., the flower-shaped AgNPs showed the best performance and were successfully applied for trace-level detection of phenformin in an aqueous sample. Furthermore, the MIP@AgNPs were also applied for the detection of phenformin in human serum, plasma, and urine samples without any cross-reactivity effect, suggesting a bright prospect for the use of anisotropic nanomaterials in future clinical trials. (C) 2017 Elsevier B.V. All rights reserved.