4-{3-[(Pyridin-4-ylmethyl)amino]-[1,2,4]triazolo[4,3-b][1,2,4]triazin-6-yl}phenol: An improved anticancer agent in hepatocellular carcinoma and a selective MDR1/MRP modulator.

Hepatocellular carcinoma is the most common type of primary liver cancer. However, multidrug resistance (MDR) is a major obstacle to the effective chemotherapy of cancer cells. This report documents the rational design, synthesis, and biological evaluation of a novel series of triazolotriazines substituted with CH2 NH-linked pyridine for use as dual c-Met/MDR inhibitors. Compound 12g with IC50 of 3.06 µM on HepG2 cells showed more potency than crizotinib (IC50 = 5.15 µM) in the MTT assay. In addition, 12g inhibited c-Met kinase at a low micromolar level (IC50 = 0.052 µM). 12g significantly inhibited P-gp and MRP1/2 efflux pumps in both cancerous HepG2 and BxPC3 cells starting from the lower concentrations of 3 and 0.3 µM, respectively. 12g did not inhibit MDR1 and MRP1/2 in noncancerous H69 cholangiocytes up to the concentration of 30 and 60 µM, respectively. Current results highlighted that cancerous cells were more susceptible to the effect of 12g than normal cells, in which the inhibition occurred only at the highest concentrations, suggesting a further interest in 12g as a selective anticancer agent. Overall, 12g, as a dual c-Met and P-gp/MRP inhibitor, is a promising lead compound for developing a new generation of anticancer agents.

Recent Applications of Protoberberines as Privileged Starting Materials for the Development of Novel Broad-Spectrum Antiviral Agents: A Concise Review (2017-2023).

Berberine is a well-known phytochemical with significant antiviral activity against a wide range of viruses. Due to having a unique backbone consisting of four interconnected rings, it can be used as a platform for the design and development of novel semisynthetic antiviral agents. The question here is whether novel broad-spectrum antiviral drugs with enhanced activity and toxicity potential can be obtained by attempting to modify the structure of this privileged lead compound. The present study aims to review the results of recent studies in which berberine and its close analogues (protoberberine alkaloids) have been used as starting materials for the production of new semisynthetic antiviral structures. For this purpose, relevant studies published in high-quality journals indexed in databases such as Scopus, Web of Science, PubMed, etc. in the time frame of 2017 to 2023 were collected. Our selection criterion in the current review focuses on the studies in which protoberberines were used as starting materials for the production of semisynthetic agents with antiviral activity during the indicated time period. Correspondingly, studies were identified in which semisynthetic derivatives with significant inhibitory activity against a wide range of viruses including human immunodeficiency virus (HIV), enterovirus 71 (EV71), zika virus (ZIKV), influenza A/B, cytomegalovirus (CMV), respiratory syncytial virus (RSV), and coxsackieviruses were designed and synthesized. Our conclusion is that, despite the introduction of diverse semisynthetic derivatives of berberine with improved activity profiles compared to the parent natural leads, sufficient derivatization has not been done yet and more studies are needed.

CNS-Active p38α MAPK Inhibitors for the Management of Neuroinflammatory Diseases: Medicinal Chemical Properties and Therapeutic Capabilities.

During the last two decades, many p38α mitogen-activated protein kinase (p38α MAPK) inhibitors have been developed and tested in preclinical/clinical studies for the treatment of various disorders, especially problems with the origin of inflammation. Previous studies strongly suggest the involvement of the p38α MAPK pathway in the pathogenesis of neurodegenerative disorders. Despite the significant progress made in this field, so far no studies have focused on p38α MAPK inhibitors that have the capability to be used for the treatment of neurodegenerative disorders. In the present review, we evaluated a wide range of well-known p38α MAPK inhibitors (more than 140 small molecules) by measuring key physicochemical parameters to identify those capable of successfully crossing the blood-brain barrier (BBB). As a result, we identify about 50 naturally occurring and synthetic p38α MAPK inhibitors with high potential to cross the BBB, which can be further explored in the future for the treatment of neurodegenerative disorders. In addition, a detailed analysis of the previously released X-ray crystal structure of the inhibitors in the active site of the p38α MAPK enzyme revealed that some residues such as Met109 play a critical role in the occurrence of effective interactions by constructing strong H-bonds. This study can encourage scientists to focus more on the design, production, and biological evaluation of new central nervous system (CNS)-active p38α MAPK inhibitors in the future.

Benzoindolizidine Alkaloids Tylophorine and Lycorine and Their Analogues with Antiviral, Anti-Inflammatory, and Anticancer Properties: Promises and Challenges.

Ongoing viral research, essential for public health due to evolving viruses, gains significance owing to emerging viral infections such as the SARS-CoV-2 pandemic. Marine and plant alkaloids show promise as novel potential pharmacological strategies. In this narrative review, we elucidated the potential of tylophorine and lycorine, two naturally occurring plant-derived alkaloids with a shared benzoindolizidine scaffold, as antiviral agents to be potentially harnessed against respiratory viral infections. Possible structure-activity relationships have also been highlighted. The substances and their derivatives were found to be endowed with powerful and broad-spectrum antiviral properties; moreover, they were able to counteract inflammation, which often underpins the complications of viral diseases. At last, their anticancer properties hold promise not only for advancing cancer research but also for mitigating the oncogenic effects of viruses. This evidence suggests that tylophorine and lycorine could effectively counteract the pathogenesis of respiratory viral disease and its harmful effects. Although common issues about the pharmacologic development of natural substances remain to be addressed, the collected evidence highlights a possible interest in tylophorine and lycorine as antiviral and/or adjuvant strategies and encourages future more in-depth pre-clinical and clinical investigations to overcome their drawbacks and harness their power for therapeutic purposes.

An Overview on Anti-COVID-19 Drug Achievements and Challenges Ahead.

The appearance of several coronavirus pandemics/epidemics during the last two decades (SARS-CoV-1 in 2002, MERS-CoV in 2012, and SARS-CoV-2 in 2019) indicates that humanity will face increasing challenges from coronaviruses in the future. The emergence of new strains with similar transmission characteristics as SARS-CoV-2 and mortality rates similar to SARS-CoV-1 (∼10% mortality) or MERS-CoV (∼35% mortality) in the future is a terrifying possibility. Therefore, getting enough preparations to face such risks is an inevitable necessity. The present study aims to review the drug achievements and challenges in the fight against SARS-CoV-2 with a combined perspective derived from pharmacology, pharmacotherapy, and medicinal chemistry insights. Appreciating all the efforts made during the past few years, there is strong evidence that the desired results have not yet been achieved and research in this area should still be pursued seriously. By expressing some pessimistic possibilities and concluding that the drug discovery and pharmacotherapy of COVID-19 have not been successful so far, this short essay tries to draw the attention of responsible authorities to be more prepared against future coronavirus epidemics/pandemics.

Therapeutic prospects of naturally occurring p38 MAPK inhibitors tanshinone IIA and pinocembrin for the treatment of SARS-CoV-2-induced CNS complications.

P38 mitogen-activated protein kinase (p38 MAPK) signaling pathway is closely related to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) replication and hyperinflammatory responses in coronavirus disease 2019 (COVID-19). Therefore, blood-brain barrier-penetrating p38 MAPK inhibitors have good potential for the treatment of central nervous system (CNS) complications of COVID-19. The aim of the present study is the characterization of the therapeutic potential of tanshinone IIA and pinocembrin for the treatment of CNS complications of COVID-19. Studies published in high-quality journals indexed in databases Scopus, Web of Science, PubMed, and so forth were used to review the therapeutic capabilities of selected compounds. In continuation of our previous efforts to identify agents with favorable activity/toxicity profiles for the treatment of COVID-19, tanshinone IIA and pinocembrin were identified with a high ability to penetrate the CNS. Considering the nature of the study, no specific time frame was determined for the selection of studies, but the focus was strongly on studies published after the emergence of COVID-19. By describing the association of COVID-19-induced CNS disorders with p38 MAPK pathway disruption, this study concludes that tanshinone IIA and pinocembrin have great potential for better treatment of these complications. The inclusion of these compounds in the drug regimen of COVID-19 patients requires confirmation of their effectiveness through the conduction of high-quality clinical trials.

Discovery of Chalcone-Based Hybrid Structures as High Affinity and Site-Specific Inhibitors against SARS-CoV-2: A Comprehensive Structural Analysis Based on Various Host-Based and Viral Targets.

Previous studies indicated that natural-based chalcones have significant inhibitory effects on the coronavirus enzymes 3CLpro and PLpro as well as modulation of some host-based antiviral targets (HBATs). In this study, a comprehensive computational and structural study was performed to investigate the affinity of our compound library consisting of 757 chalcone-based structures (CHA-1 to CHA-757) for inhibiting the 3CLpro and PLpro enzymes and against twelve selected host-based targets. Our results indicated that CHA-12 (VUF 4819) is the most potent and multi-target inhibitor in our chemical library over all viral and host-based targets. Correspondingly, CHA-384 and its congeners containing ureide moieties were found to be potent and selective 3CLpro inhibitors, and benzotriazole moiety in CHA-37 was found to be a main fragment for inhibiting the 3CLpro and PLpro. Surprisingly, our results indicate that the ureide and sulfonamide moieties are integral fragments for the optimum 3CLpro inhibition while occupying the S1 and S3 subsites, which is fully consistent with recent reports on the site-specific 3CLpro inhibitors. Finding the multi-target inhibitor CHA-12, previously reported as an LTD4 antagonist for the treatment of inflammatory pulmonary diseases, prompted us to suggest it as a concomitant agent for relieving respiratory symptoms and suppressing COVID-19 infection.

Dual action anti-inflammatory/antiviral isoquinoline alkaloids as potent naturally occurring anti-SARS-CoV-2 agents: A combined pharmacological and medicinal chemistry perspective.

In the search for compounds that inhibit the SARS-CoV-2 after the onset of the COVID-19 pandemic, isoquinoline-containing alkaloids have been identified as compounds with high potential to fight the disease. In addition to having strong antiviral activities, most of these alkaloids have significant anti-inflammatory effects which are often manifested through the inhibition of a promising host-based anti-COVID-19 target, the p38 MAPK signaling pathway. In the present review, our pharmacological and medicinal chemistry evaluation resulted in highlighting the potential of anti-SARS-CoV-2 isoquinoline-based alkaloids for the treatment of COVID-19 patients. Considering critical parameters of the antiviral and anti-inflammatory activities, mechanism of action, as well as toxicity/safety profile, we introduce the alkaloids emetine, cephaeline, and papaverine as high-potential therapeutic agents for use in the treatment of COVID-19. Although preclinical studies confirm that some isoquinoline-based alkaloids reviewed in this study have a high potential to inhibit the SARS-CoV-2, their entry into drug regimens of COVID-19 patients requires further clinical trial studies and toxicity evaluation.

Recruitment of chalcone's potential in drug discovery of anti-SARS-CoV-2 agents.

Chalcone is an interesting scaffold found in the structure of many naturally occurring molecules. Medicinal chemists are commonly interested in designing new chalcone-based structures because of having the α, ß-unsaturated ketone functional group, which allows these compounds to participate in Michael's reaction and create strong covalent bonds at the active sites of the targets. Some studies have identified several natural chalcone-based compounds with the ability to inhibit the severe acute respiratory syndrome coronavirus and Middle East respiratory syndrome coronavirus proteases. A few years after the advent of the coronavirus disease 2019 pandemic and the publication of many findings in this regard, there is some evidence that suggests chalcone scaffolding has great potential for use in the design and development of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) inhibitors. Artificial placement of this scaffold in the structure of optimized anti-SARS-CoV-2 compounds can potentially provide irreversible inhibition of the viral cysteine proteases 3-chymotrypsin-like protease and papain-like protease by creating Michael interaction. Despite having remarkable capabilities, the use of chalcone scaffold in drug design and discovery of SARS-CoV-2 inhibitors seems to have been largely neglected. This review addresses issues that could lead to further consideration of chalcone scaffolding in the structure of SARS-CoV-2 protease inhibitors in the future.

Chalcone-amide, a privileged backbone for the design and development of selective SARS-CoV/SARS-CoV-2 papain-like protease inhibitors.

The newly emerged coronavirus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that caused the COVID-19 pandemic, is the closest relative of SARS-CoV with high genetic similarity. The papain-like protease (PLpro) is an important SARS-CoV/SARS-CoV-2 nonstructural protein that plays a critical role in some infection processes such as the generation of the functional replication complex, maturation of crude polyproteins, and regulation of the host antiviral immune responses. Therefore, the research to discover SARS-CoV-2 PLpro inhibitors could be a sensible strategy to obtain therapeutic agents for the treatment of COVID-19. Aiming to find SARS-CoV/SARS-CoV-2 PLpro inhibitors, various high throughput screenings (HTS) have been performed over the past two decades. Interestingly, the result of these efforts is the identification of hit/lead compounds whose structures have one important feature in common, namely having a chalcone-amide (N-benzylbenzamide) backbone. Structure-activity relationship (SAR) studies have shown that placing an (R)-configurated methyl group on the middle carbon adjacent to the amide group creates a unique backbone called (R)-methyl chalcone-amide, which dramatically increases PLpro inhibitory potency. Although this scaffold has not yet been introduced by medicinal chemists as a specific skeleton for the design of PLpro inhibitors, structural considerations show that the most reported PLpro inhibitors have this skeleton. This review suggests the (R)-methyl chalcone-amide scaffold as a key backbone for the design and development of selective SARS-CoV-2 PLpro inhibitors. Understanding the SAR and binding mode of these inhibitors in the active site of SARS-CoV-2 PLpro can aid the future development of anti-COVID-19 agents.

Application of emetine in SARS-CoV-2 treatment: regulation of p38 MAPK signaling pathway for preventing emetine-induced cardiac complications.

Emetine is one of the most highly potent anti-SARS-CoV-2 agents ever identified. In addition to having strong anti-SARS-CoV-2 activities, emetine has other valuable therapeutic effects such as strong anti-inflammatory and anti-arterial pulmonary hypertension (APH) properties, which are suitable for the treatment of COVID-19. Its proper concomitant therapeutic effect has led researchers to test this compound in clinical trials to combat COVID-19. However, due to the risks of cardiac complications, very low doses of emetine have been used in different studies, which may not have significant therapeutic effects. The p38 MAPK signaling pathway is strongly highlighted as an important operator in cardiac cellular damages such as disruption of cardiac fibroblast function and myopathy/cardiomyopathy. Inhibition of this pathway by appropriate inhibitors has also been considered by scientists as a promising strategy for the treatment of fatal host-related hyper-inflammatory immune responses following SARS-CoV-2 infection. Although remarkable stimulatory effects of emetine on activation of the p38 MAPK pathway have been reported in recent studies and strong evidence suggests that this pathway plays an effective role in the emetine's toxicities, it has not been discussed yet that emetine induced cellular cardiac complications may be due to the activation of this critical pathway. Considering these points could lead to the finding of strategies for applying the valuable potential of emetine in the treatment of COVID-19 at low risks.

Papaverine, a promising therapeutic agent for the treatment of COVID-19 patients with underlying cardiovascular diseases (CVDs).

The causative agent of coronavirus disease-2019 (COVID-19), severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), enters the host cells via an angiotensin-converting enzyme 2 (ACE2)-mediated endocytosis-dependent manner. Because ACE2 is highly expressed in the heart, SARS-CoV-2 can severely infect heart tissue and arteries, causing acute and chronic damage to the cardiovascular system. Therefore, special attention should be paid to finding appropriate agents to protect this vital system during COVID-19 treatment. Papaverine is a unique vasodilator alkaloid that is clinically used in the treatment of vasospasm. Interestingly, this compound has potent and direct effects on a wide range of viruses, and could also prevent viral exploitation mechanisms of the host cell facilities by inhibiting some cellular signaling pathways such as p38 MAPK. This pathway was recently introduced as a promising target for the treatment of COVID-19. Papaverine also has anti-inflammatory effects which is useful in combating the hyper-inflammatory phase of the COVID-19. Unlike some medications that have severe dosage-restrictions in the treatment of COVID-19 due to cardiac side effects, papaverine is recommended for use in many heart disorders. The ability of papaverine to treat COVID-19 has become more promising when the results of some extensive screenings showed the strong ability of this compound to inhibit the cytopathic effects of SARS-CoV-2 with EC50 of 1.1 µM. Having several therapeutic effects along with desired safety profile raises this hypothesis that papaverine could be a promising compound for the suppression of SARS-CoV-2 and prevention of ischemia/vasoconstriction-related complications in COVID-19 disease, especially in patients with underlying cardiovascular diseases (CVDs).

Different Aspects of Emetine's Capabilities as a Highly Potent SARS-CoV-2 Inhibitor against COVID-19.

In the global movement to find the appropriate agents to fight the coronavirus disease of 2019 (COVID-19), emetine is one of the strongest anti-SARS-CoV-2 compounds with sub-micromolar EC50 values, identified in several studies and high-throughput screening efforts. The reported anti-SARS-CoV-2 mechanisms indicate the effect of this compound on both virus-based and host-based targets. In addition to having excellent antiviral effects, emetine can relieve COVID-19 patients by reducing inflammation through inhibitory activity against NF-κB by the mechanism of IκBα phosphorylation inhibition; it can also limit the lipopolysaccharide-induced expression of pro-inflammatory cytokines TNFα, IL-1ß, and IL-6. Emetine also can well reduce pulmonary arterial hypertension as an important COVID-19 complication by modulating a variety of cellular processes such as the Rho-kinase/CyPA/Bsg signaling pathway. The therapeutic value of emetine for combating COVID-19 was highlighted when in vivo pharmacokinetic studies showed that the concentration of this compound in the lungs increases significantly higher than the EC50 of the drug. Despite its valuable therapeutic effects, emetine has some cardiotoxic effects that limit its use in high doses. However, high therapeutic capabilities make emetine a valuable lead compound that can be used for the design and development of less toxic anti-COVID-19 agents in the future. This Review provides a collection of information on the capabilities of emetine and its potential for the treatment of COVID-19, along with structural analysis which could be used for further research in the future.

Recent advances of antitumor shikonin/alkannin derivatives: A comprehensive overview focusing on structural classification, synthetic approaches, and mechanisms of action.

Shikonin and its enantiomeric analogue, alkaninn, are prevailing natural lead compounds in the drug discovery and development of anticancer agents. Despite having numerous biological effects, the most important activity reported for shikonin derivatives is the antitumor effect which is exerted through various mechanisms such as induction of apoptosis and autophagy. The design, synthesis, and development of new shikonin derivatives are continuously performed with the aim of promoting therapeutic effects through increasing cytotoxicity against cancer cells and simultaneously reducing toxicity on normal cells. In spite of significant advances in the development of shikonin derivatives in recent years and the publication of some reviews in this regard, the structural classification, synthesis methods, as well as the diversity of the anti-tumor mechanism of action of these compounds have not been well considered. This review aims to provide comprehensive data in this regard by reviewing studies conducted over the last two decades (from 2000 until now).

Therapeutic potential of chelerythrine as a multi-purpose adjuvant for the treatment of COVID-19.

Multifunctional nature of phytochemicals and their chemical diversity has attracted attention to develop leads originated from nature to fight COVID-19. Pharmacological activities of chelerythrine and its congeners have been studied and reported in the literature. This compound simultaneously has two key therapeutic effects for the treatment of COVID-19, antiviral and anti-inflammatory activities. Chelerythrine can prevent hyper-inflammatory immune response through regulating critical signaling pathways involved in SARS-CoV-2 infection, such as alteration in Nrf2, NF-κB, and p38 MAPK activities. In addition, chelerythrine has a strong protein kinase C-α/-ß inhibitory activity suitable for cerebral vasospasm prevention and eryptosis reduction, as well as beneficial effects in suppressing pulmonary inflammation and fibrosis. In terms of antiviral activity, chelerythrine can fight with SARS-CoV-2 through various mechanisms, such as direct-acting mechanism, viral RNA-intercalation, and regulation of host-based antiviral targets. Although chelerythrine is toxic in vitro, the in vivo toxicity is significantly reduced due to its structural conversion to alkanolamine. Its multifunctional action makes chelerythrine a prominent compound for the treatment of COVID-19. Considering precautions related to the toxicity at higher doses, it is expected that this compound is useful in combination with proper antivirals to reduce the severity of COVID-19 symptoms.

Design, synthesis and biological evaluation of naphthalene-derived (arylalkyl)azoles containing heterocyclic linkers as new anticonvulsants: A comprehensive in silico, in vitro, and in vivo study.

In continuation of our research to find strong and safe anticonvulsant agents, a number of (arylalkyl)azoles (AAAs) containing naphthylthiazole and naphthyloxazole scaffolds were designed and synthesized. The in vivo anticonvulsant evaluations in BALB/c mice revealed that some of them had significant anticonvulsant activity in both maximal electroshock (MES) and pentylenetetrazole (PTZ) models of epilepsy. The best profile of activity was observed with compounds containing imidazole and triazole rings (C1, C6, G1, and G6). In particular, imidazolylmethyl-thiazole C1 with median effective dose (ED50)= 7.9 mg/kg in the MES test, ED50= 27.9 mg/kg in PTZ test, and without any sign of neurotoxicity (in the rotarod test, 100 mg/kg) was the most promising compound. The patch-clamp recording was performed to study the mechanism of action of the representative compound C1 on hippocampal dentate gyrus (DG) cells. The results did not confirm any modulatory effect of C1 on the voltage-gated ion channels (VGICs) or GABAA agonism, but suggested a significant reduction of excitatory postsynaptic currents (EPSCs) frequency on hippocampal DG neurons. Sub-acute toxicity studies revealed that administration of the most active compounds (C1, C6, G1, and G6) at 100 mg/kg bw/day for two weeks did not result in any mortality or significant toxicity as evaluated by assessment of biochemical markers such as lipid peroxidation, intracellular glutathione, total antioxidant capacity, histopathological changes, and mitochondrial functions. Other pharmacological aspects of compounds including mechanistic and ADME properties were investigated computationally and/or experimentally. Molecular docking on the NMDA and AMPA targets suggested that the introduction of the heterocyclic ring in the middle of AAAs significantly affects the affinity of the compounds. The obtained results totally demonstrated that the prototype compound C1 can be considered as a new lead for the development of anticonvulsant agents.

Synthesis, in silico, in vitro and in vivo evaluations of isatin aroylhydrazones as highly potent anticonvulsant agents.

In this study, a series of new isatin aroylhydrazones (5a-e and 6a-e) was synthesized and evaluated for their anticonvulsant activities. The (Z)-configuration of compounds was confirmed by 1H NMR. In vivo studies using maximal electroshock (MES) and pentylenetetrazole (PTZ) models of epilepsy in mice revealed that while most of compounds had no effect on chemically-induced seizures at the higher dose of 100 mg/kg but showed significant protection against electrically-induced seizures at the lower dose of 5 mg/kg. Certainly, N-methyl analogs 6a and 6e were found to be the most effective compounds, displaying 100% protection at the dose of 5 mg/kg. Protein binding and lipophilicity(logP) of the selected compounds (6a and 6e) were also determined experimentally. In silico evaluations of title compounds showed acceptable ADME parameters, and drug-likeness properties. Distance mapping and docking of the selected compounds with different targets proposed the possible action of them on VGSCs and GABAA receptors. The cytotoxicity evaluation of 6a and 6e against SH-SY5Y and Hep-G2 cell lines indicated safety profile of compounds on the neuronal and hepatic cells.

Synthesis and Biological Assessment of 2-Hydroxyiminoethanones as Anti-Inflammatory and ß-Amyloid Aggregation Inhibitors.

Alzheimer's disease (AD) is a neuroinflammatory based pathologic state in which ß-amyloid aggregates are major devastating agents. In this study, a series of 2-hydroxyiminoethanones were synthesized and evaluated as anti-inflammatory in carrageenan and formalin tests and inhibitors of ß-amyloid aggregation. Compounds 1-10b were synthesized through a two-step reaction. Results: Compounds 1-5b showed more ß-amyloid disaggregation ability than reference drugs rifampicin and donepezil and compound 2b was the best compound in this series and could reduce the extent of amyloid aggregation to 50.9%. Interestingly, compounds 1b and 3b showed significant anti-inflammatory activity in carrageenan-induced paw edema compared to control group and equivalent to the reference drug indomethacin. 2-Hydeoxyiminoethanones are privileged scaffold for further drug research and development as anti-neuroinflammatory and neuroprotective agents.

Layer-by-layer assembly of gold nanoparticles and cysteamine on gold electrode for immunosensing of human chorionic gonadotropin at picogram levels.

The development of an electrochemical immunosensor for the detection of human chorionic gonadotropin (hCG) is described with a limit of detection as low as 0.3 pg mL(-1) in phosphate buffer. In this immunosensor, cysteamine (Cys) and gold nanoparticles (AuNPs) were used to immobilize an anti-hCG monoclonal antibody onto a gold electrode (GE). The structure of AuNPs has been confirmed by EDS, SEM, and TEM analysis. Due to the large specific surface area and excellent electrical conductivity of AuNPs, electron transfer was promoted and the amount of hCG antibody was enhanced significantly. A systematic study on the effects of experimental parameters such as pH, incubation time in the hCG solution and urea solution used for experiments on the binding between the immobilized antibody and hCG has been carried out. Under optimal experimental parameters, differential pulse voltammetry (DPV) signal changes of the [Fe(CN)6](3-/4-) are used to detect hCG with two broad linear ranges: 0.001 to 0.2 and 0.2 to 60.7 ng mL(-1). The LOD value proves more sensitive in comparison with previously reported methods. The prepared immunosensor showed high sensitivity and stability. In addition, the immunosensor was successfully used for the determination of hCG in human serum.