Direct Detection Of Biomolecules Research Articles

Recent advances in surface-enhanced Raman scattering for liver cancer detection

As one of the most common cancers, liver cancer has seriously endangered human life and health. The diagnosis of liver cancer is of great importance to improve the overall treatment outcome of patients. Surface-enhanced Raman scattering (SERS) is an attractive analytical technique for detecting liver cancer, which has the advantages of high sensitivity, low cost and high specificity. This review summarizes the advances in SERS analysis techniques for the diagnostic detection of liver cancer. In particular, extrinsic label and label-free are the two main methods, generally used for indirect or direct detection of biomolecules. First, we describe the methods and materials used for label SERS to detect tumor markers within hepatocellular carcinoma. We then describe recent advances in label-free SERS for detecting liver cancer. The conclusion section summarizes the current challenges and provides an outlook on SERS detection.

Real‐Time Monitoring of Glucose Export from Isolated Chloroplasts Using an Organic Electrochemical Transistor

AbstractBiosensors based on organic electrochemical transistors (OECT) are attractive devices for real‐time monitoring of biological processes. The direct coupling between the channel of the OECT and the electrolyte enables intimate interfacing with biological environments at the same time bringing signal amplification and fast sensor response times. So far, these devices are mainly applied to mammalian systems; cells or body fluids for the development of diagnostics and various health status monitoring technology. Yet, no direct detection of biomolecules from cells or organelles is reported. Here, an OECT glucose sensor applied to chloroplasts, which are the plant organelles responsible for the light‐to‐chemical energy conversion of the photosynthesis, is reported. Real‐time monitoring of glucose export from chloroplasts in two distinct metabolic phases is demonstrated and the transfer dynamics with a time resolution of 1 min is quantified, thus reaching monitoring dynamics being an order of magnitude better than conventional methods.

Highly sensitive field effect charge sensor for direct detection of biomolecules

A field effect transistor (FET) charge sensor is proposed to work at a special operating condition in order to become extremely sensitive to the gate charge change caused by biomolecules. A device model has been established and the simulation results justify the hypothesis. It is found that at the depletion operating condition the proposed FET charge sensor will shift a gate voltage up to 1 mV in response to every electron per square micron, which is much more sensitive than other existing FET sensors.

A simple and direct biomolecule detection scheme based on a microwave resonator

Although several successful biosensors exist, they often require complex fabrication sequence or time-consuming sensing processes such as an off-site verification of a sensing result. At the same time, the biosensors generally focus on high sensitivity. This paper reports a cost-competitive biosensor that is capable of simple and direct detection of biomolecules without any off-site verification. The biosensor is realized with a microwave passive with a simple structure, a coplanar waveguide (CPW)-to-slotline ring resonator (CSRR) that resonant frequency is 3.375 GHz. The CSRR biosensor was then modified for higher sensitivity by increasing the effective sensing area. Two kinds of the CSRR biosensor were realized using micromachining technology. After simple fabrication, the biosensors were electrically characterized by measuring the resonant frequency shift as the biotin and streptavidin attached on the CSRR biosensor. The biotin and streptavidin induce a resonant frequency decrease of 65 and 10 MHz for the original CSRR biosensor, and 79 and 18 MHz for the modified CSRR biosensor, respectively. Based on the measurement of the resonant frequency shift, the relative permittivity of the biomolecules was calculated by numerical simulation, and was found to be 9800 for biotin and 500 for streptavidin.

A Dielectric Biosensor Using the Capacitance Change with AC Frequency Integrated on Glass Substrates

Glass-based microchannel chips were fabricated using photolithographic technology, and Pt thin-film microelectrodes as dielectric biosensors were integrated on them. From capacitance-frequency measurements at various interelectrode distances and ionic concentrations, a significant difference between deionized (DI) water and tris-ethylenediaminetetraacetic acid (EDTA) (TE) buffer was observed in the low-frequency region. Although the capacitance (CM) of the DI water decreased as the interelectrode distance increased, that of the TE buffer was similar up to a frequency of 100 Hz, after which it was spilt in the same manner as the DI water above 100 Hz. As the ionic concentration increased, the CM of the TE buffer increased and the slope in the low frequency region changed from -0.875 to -0.425. The point where the slope changed shifted towards the frequency increase. These observations were clarified from the viewpoint of interfacial phenomena, such as the electrical double layer and Faradaic reactions, the dielectric constant related to conductivity, and the capacitance inversely proportional to the interelectrode distance. The addition of deoxyribonucleic acid (DNA) molecules (10 ng/µl) increased the capacitance and dielectric loss in the TE buffer at low frequency. It is feasible to use dielectric properties for the rapid and direct detection of biomolecules, particularly DNA molecules, without using labels or indicators.

Direct detection of biomolecules in a capillary electrophoresis-chemiluminescence detection system.

Direct detection of biomolecules, such as alpha-amino acids, peptides, and proteins, was accomplished using a capillary electrophoresis-chemiluminescence detection system, in which a luminol-hydrogen peroxide-Cu(II)-catalyzed chemiluminescence reaction was utilized. Biomolecules migrated in the capillary, where they mixed with luminol and the Cu(II) catalyst included in the running buffer. The capillary outlet was inserted into a batch-type chemiluminescence detection cell with hydrogen peroxide-supplemented electrolyte solution. Chemiluminescence was observed at the tip of the capillary outlet. The chemiluminescence peak from biomolecules appeared due to the enhancement of Cu(II) catalytic activity for luminol-hydrogen peroxide chemiluminescence. The Cu(II) was more catalytically active when it interacted with biomolecules forming Cu(II)-biomolecule complexes. In this study, biomolecules were directly separated and detected in a capillary electrophoresis-chemiluminescence detection system. Twenty alpha-amino acids, 4 peptides, and 11 proteins were examined. Most of them were detected with satisfactory CL intensity response. Glutamic acid, an alpha-amino acid, was detected at concentrations ranging from 2.0 x 10(-7) to 1.2 x 10(-5) M with a detection limit (S/N = 3) of 1.0 x 10(-7) M (0.6 fmol). Glycylglycine, a peptide, was detected at concentrations ranging from 1.7 x 10(-7) to 1.2 x 10(-5) M with a detection limit (S/N = 3) of 1.7 x 10(-7) M (0.9 fmol). Hemoglobin, a heme protein, in which the heme structure was independently catalytically active, was detected at concentrations ranging from 1.2 x 10(-7) to 1.0 x 10(-5) M with a detection limit (S/N = 3) of 1.2 x 10(-7) M (0.6 fmol). Representative mixtures of alpha-amino acids and peptides were well detected with superior separation.