A　new　and　disposable　electrochemical　immunosensor　was　designed　for　detection　of　alpha-fetoprotein　(AFP),　as　a　model　analyte,　with　sensitivity　enhancement　based　on　enzyme-catalyzed　silver　deposition　onto　irregular-shaped　gold　nanoparticles　(ISGNPs).　The　assay　was　carried　out　with　a　sandwich-type　immunoassay　protocol　by　using　ISGNP-labeled　anti-AFP　antibodies　conjugated　with　alkaline　phosphatase　(ALP-Ab(2))　as　detection　antibodies.　The　enzymatically　catalytic　deposition　of　silver　on　the　electrode　could　be　measured　by　stripping　analysis　in　KCl　solution　due　to　the　Ag/AgCl　solid-state　voltammetric　process.　Several　labeling　protocols　including　spherical　gold　nanoparticle-labeled　ALP-Ab(2)　and　ISGNP-labeled　ALP-Ab(2)　were　investigated　for　determination　of　AFP,　and　improved　analytical　properties　were　achieved　with　the　ISGNP　labeling.　With　the　ISGNP　labeling　method,　the　effects　of　incubation　time　and　incubation　temperature　for　antigen-antibody　reaction,　and　deposition　time　of　silver　on　the　current　responses　of　the　electrochemical　immunosensors　were　also　monitored.　Under　optimal　conditions,　the　electrochemical　immunosensor　exhibited　a　wide　dynamic　range　from　0.01　ng　mL(-1)　to　200　ng　mL(-1)　with　a　detection　limit　of　5.0　pg　mL(-1)　AFP.　The　immunosensor　displayed　a　good　stability　and　acceptable　reproducibility　and　accuracy.　No　significant　differences　at　the　95%　confidence　level　were　encountered　in　the　analysis　of　10　clinical　serum　samples　between　the　developed　immunoassay　and　the　commercially　available　electrochemiluminescent　method　for　determination　of　AFP.　(C)　2012　Elsevier　B.V.　All　rights　reserved.