Acute myocardial infarction (AMI) is considered to be one of the predominant causes of human death; therefore, a rapid and accurate diagnostic method for AMI is urgently required. In this work, a highly sensitive lateral flow immunoassay (LFIA) platform was designed and fabricated for the quantitative determination of cardiac troponin I (cTnI) using a scanner, a smartphone and a colloidal gold immunoassay analyzer. To overcome the limitation of low sensitivity of traditional colloidal gold-based LFIA, three-dimensionally assembled gold nanoparticles (AuNPs) within a dendritic mesoporous silica nanoparticle (DMSN) scaffold were fabricated as signal labels. The assembly structure greatly enhanced the light extinction ability of a single label for signal amplification. The DMSNs@Au-based LFIA strips exhibited excellent detection performance including a high sensitivity (LOD = 70 pg mL