Characterization of surface modification on self-assembled monolayer-based piezoelectric crystal immunosensor for the quantification of serum α-fetoprotein

Probing surface properties of organic molecular layers by scanning tunneling microscopy

In view of the relevance of organic thin layers in many fields, the fundamentals, growth mechanisms, and dynamics of thin organic layers, in particular thiol-based self-assembled monolayers (SAMs) on Au(111) are systematically elaborated. From both theoretical and practical perspectives, dynamical and structural features of the SAMs are of great intrigue. Scanning tunneling microscopy (STM) is a remarkably powerful technique employed in the characterization of SAMs. Numerous research examples of investigation about the structural and dynamical properties of SAMs using STM, sometimes combined with other techniques, are listed in the review. Advanced options to enhance the time resolution of STM are discussed. Additionally, we elaborate on the extremely diverse dynamics of various SAMs, such as phase transitions and structural changes at the molecular level. In brief, the current review is expected to supply a better understanding and novel insights regarding the dynamical events happening in organic SAMs and how to characterize these processes.

Optimally Configured Optical Fiber Near-Field Enhanced Plasmonic Resonance Immunoprobe for the Detection of Alpha-Fetoprotein

The detection of trace biomarkers is an important supplementary approach for early screening and diagnoses of tumors. An optical fiber near-field enhanced plasmonic resonance immunoprobe is developed for the detection of the hepatocellular carcinoma biomarker, i.e., the alpha-fetoprotein. Generic principles based on dispersion models and finite element analysis (FEA) models are developed to realize the optimized configuration of spectral characteristics of the immunoprobe. Dispersion models provide theoretical guidance for the design of the multilayer sensing structure from the perspective of the ray optics theory. FEA models provide theoretical guidance for the selection of coating materials from the perspective of the self-defined dielectric constant ratio, i.e., the ratio of the real part to the imaginary part. The optimized configuration of the antibody coupling further improves the biosensing performance of the immunoprobe. The limit of detection (LOD) can reach down to 0.01 ng mL^-1 , which is one order of magnitude lower than those relevant reported works. Such a low LOD can more effectively avoid the accuracy degradation of detection results due to measurement errors. Human serum samples have also been detected, with the good precision achieved. This work shows promising prospects in applications of label-free, low-cost, rapid, and convenient early screening of tumors.

A simple, sensitive, label-free electrochemical immunosensor based on the chitosan-coated silver/cerium oxide (CS@Ag/CeO2) nanocomposites for the detection of alpha-fetoprotein (AFP)

Metal oxide-based sensors have the benefit of inexpensive, quick response, and high sensitivity in detecting specific biological species. In this article, a simple electrochemical immunosensor was fabricated using antibody-chitosan coated silver/cerium oxide (Ab-CS@Ag/CeO₂) nanocomposites on a gold electrode for sensitive alpha-fetoprotein (AFP) diagnosis in human serum samples. Successfully synthesis of AFP antibody-CS@Ag/CeO₂conjugates was confirmed through Fourier transform infrared spectra of the prototype. The amine coupling bond chemistry was then used to immobilize the resultant conjugate on a gold electrode surface. It was observed that the interaction of the synthesized Ab-CS@Ag/CeO₂nanocomposites with AFP prevented an electron transfer and reduced the voltammetric Fe(CN)₆^3-/4-peak current, which was proportional to the amount of AFP. The linear ranges of AFP concentration were found from 10^-12-10^-6g.ml^-1. The limit of detection was calculated using the calibration curve and came out to be 0.57 pg.ml^-1. The designed label-free immunosensor successfully detected AFP in human serum samples. As a result, the resulting immunosensor is a promising sensor plate form for AFP detection and could be used in clinical bioanalysis.

Multi-marker diagnosis method for early Hepatocellular Carcinoma based on surface plasmon resonance

Early diagnosis of Hepatocellular Carcinoma (HCC) is an important means to raise the survival rate of patients. Multi-marker combined detection is a powerful tool of early HCC diagnosis. Traditional detection methods are not effective and accurate because it is difficult to achieve combined detection of multiple markers. In this paper, we selected Alpha Fetoprotein (AFP) and miRNA-125b as the combined detection markers to improve the simultaneously diagnostic sensitivity and specificity. The anti-AFP monoclonal antibody and the DNA probes paired with the miRNA-125b were modified on the surface of surface plasmon resonance (SPR) sensor respectively to specifically recognize AFP and miRNA-125b in serum. In order to enhance the SPR response signal and detection sensitivity, Double Antibody Sandwich Method (DASM) and S9.6 antibody enhanced method were applied to achieve low detection limit of the two markers. Experimental results showed that AFP (25-400 ng/mL) was accurately detected by DASM and the detection limit of miRNA-125b by S9.6 antibody enhanced method reached 123.044 pM. These results verified the feasibility of the multi-marker detection method in early diagnosis of HCC.

Assessing the responses of cellular proteins induced by hyaluronic acid-modified surfaces utilizing a mass spectrometry-based profiling system: over-expression of CD36, CD44, CDK9, and PP2A

The cell responses to biopolymer surface at the early adhesion stages can be critical for cell survival. The purpose of this research was to assess formation of hyaluronic acid (HA) biopolymer surface, the fibroblasts were used as an experimental model to evaluate the responses of cellular proteins induced by biopolymer materials using a mass spectrometry-based profiling system. Surfaces were covered by multi-walled carbon nanotubes (CNT), chitosan (CS), and HA to increase the surface area, enhance the adhesion of biopolymer and promote the rate of cell proliferation. The amount of adhered fibroblasts on CNT/CS/HA electrodes of quartz crystal microbalance (QCM) were greatly exceeded those on other surfaces that were consistent with cell-count technique. Moreover, analyzing differential protein expressions of adhered fibroblasts on those biopolymer surfaces by proteomic approaches identified CD36, CD44, PP2A, and CDK9 as key proteins. To validate the influences of those four proteins on adhesions of fibroblasts on biopolymers, the cells were blocked by antibodies of the proteins and the adhesions of cells on the tested biopolymer surfaces were examined using a QCM technique, flow cytometric analysis and morphological observations. The results of significantly decreasing the weights and densities of the blocked fibroblasts adhering to CNT/CS/HA surfaces were obtained, and validate those proteins found by proteomic approaches. Utilizing mass spectrometry-based proteomics to evaluate cell adhesions on biopolymers is proposed.