Biosensing of Alpha-Fetoprotein: A Key Direction toward the Early Detection and Management of Hepatocellular Carcinoma

Abstract

Hepatocellular carcinoma (HCC) is currently one of the most prevalent cancers worldwide. Associated risk factors include, but are not limited to, cirrhosis and underlying liver diseases, including chronic hepatitis B or C infections, excessive alcohol consumption, nonalcoholic fatty liver disease (NAFLD), and exposure to chemical carcinogens. It is crucial to detect this disease early on before it metastasizes to adjoining parts of the body, worsening the prognosis. Serum biomarkers have proven to be a more accurate diagnostic tool compared to imaging. Among various markers such as nucleic acids, circulating genetic material, proteins, enzymes, and other metabolites, alpha-fetoprotein (AFP) is a protein marker primarily used to diagnose HCC. However, current methods need a large sample and carry a high cost, among other challenges, which can be improved using biosensing technology. Early and accurate detection of AFP can prevent severe progression of the disease and ensure better management of HCC patients. This review sheds light on HCC development in the human body. Afterward, we outline various types of biosensors (optical, electrochemical, and mass-based), as well as the most relevant studies of biosensing modalities for non-invasive monitoring of AFP. The review also explains these sensing platforms, detection substrates, surface modification agents, and fluorescent probes used to develop such biosensors. Finally, the challenges and future trends in routine clinical analysis are discussed to motivate further developments.

Keywords: alpha-fetoprotein; biosensors; diagnostic tools; early detection; hepatocellular carcinoma.

Figure 1

(A) Schematic representation of the detection of AFP using enzyme cascade-amplified immunoassay (ECAIA) based on nanobody–alkaline phosphatase fusion (Nb-ALP) and MnO₂ nanoflakes. (B) UV–vis absorption spectra of different combinations of the detection components in the MnO₂-TMB system. (C) Response measurement and correlation analysis in terms of absorbance versus the mass of A1-ALP [22]. Adapted from [22], with copyright permission.

Figure 2

(A) Schematic representation of lateral flow assay-based detection of AFP using semiconducting polymer PF-TC6FQ/PFCN/PFO and carboxyl-functionalized polystyrene PS-PEG-COOH. The polymer dots were conjugated with AFP antibody and then loaded onto the conjugate pad. (B) Images of the test strips under 365 nm light irradiation after reaction with samples containing AFP antigens (0–20 ng/mL). The bottom panels show their corresponding fluorescence ratios of T/C measured by ImageJ software. The insets in each panel show the calibration curves at antigen concentrations of 3–15 ng/mL. Error bars show standard deviations of 5 replicate measurements [50]. Adapted from [50] with copyright permission.

Figure 3

(A) Schematic illustration of AFP detection using Graphene Oxide-FAM-AFP-aptamer quenching Mechanism. (B) Change in the fluorescence spectra of FAM-ssDNA/GO complex in the presence of increasing concentrations of AFP (0–300 pg/mL). (C) The calibration plot of F/F0 of FAM-ssDNA/GO as a function of AFP concentration. Inset: calibration plot of AFP detection (1–150 pg/mL), where F0 and F are the fluorescence signals in the absence and the presence of AFP, respectively. The excitation and emission wavelengths were 488 nm and 520 nm [56]. Adapted from [56], with copyright permission under the terms of the CC-BY-NC-ND 3.0 license.

Figure 4

(A) Illustration of PS@Ag/SiO₂/Ag chips fabrication process and chemisorption of the DSNB molecules on the SERS substrates, with subsequent covalent binding of anti-AFP-L3 and followed by capture of the corresponding antigen AFP-L3. (B) SERS spectra of DSNB absorbed on the Ag/SiO₂/Ag chips conjugated with antibody and anti-AFP-L3 capture with the AFP-L3 antigen of different concentrations (0, 0.5, 1, 2, 4, and 8 ng/mL). (C) The calibration plot of the intensity ratio of I₁₃₉₀/I₁₀₇₄ against the AFP-L3 concentration [60]. Adapted from [60] with copyright permission.

Figure 5

(A) Schematic representation of nitrogen-doped nanoporous carbon nanomaterials (N-mC)-based aptasensor for the detection of AFP. (B) Electrochemical impedance spectroscopy (EIS) Nyquist plots for the detection of different concentrations of AFP (0.0001, 0.001, 0.01, 0.1, 1, 10, 50, and 100 ng/mL) using the N-mCg-based aptasensor; (C) The corresponding calibration curves between DRct and AFP concentrations (inset: the linear fit plot of DRct as a function of the logarithm of AFP concentration (n = 3) [66]. Adapted from [66], with copyright permission.