Atomic force microscopy fishing and mass spectrometry identification of gp120 on immobilized aptamers

AFM-fishing technology for protein detection in solutions

The review considers the possibility of using atomic force microscopy (AFM) as a basic method for protein detection in solutions with low protein concentrations. The demand for new bioanalytical approaches is determined by the problem of insufficient sensitivity of systems used in routine practice for protein detection. Special attention is paid to demonstration of the use in bioanalysis of a combination of AFM and fishing methods as an approach of concentrating biomolecules from a large volume of the analyzed solution on a small surface area.

Aptamers in Virology-A Consolidated Review of the Most Recent Advancements in Diagnosis and Therapy

The use of short oligonucleotide or peptide molecules as target-specific aptamers has recently garnered substantial attention in the field of the detection and treatment of viral infections. Based on their high affinity and high specificity to desired targets, their use is on the rise to replace antibodies for the detection of viruses and viral antigens. Furthermore, aptamers inhibit intracellular viral transcription and translation, in addition to restricting viral entry into host cells. This has opened up a plethora of new targets for the research and development of novel vaccines against viruses. Here, we discuss the advances made in aptamer technology for viral diagnosis and therapy in the past decade.

Detection of Circulating Serum microRNA/Protein Complexes in ASD Using Functionalized Chips for an Atomic Force Microscope

MicroRNAs, which circulate in blood, are characterized by high diagnostic value; in biomedical research, they can be considered as candidate markers of various diseases. Mature microRNAs of glial cells and neurons can cross the blood-brain barrier and can be detected in the serum of patients with autism spectrum disorders (ASD) as components of macrovesicles, macromolecular protein and low-density lipoprotein particles. In our present study, we have proposed an approach, in which microRNAs in protein complexes can be concentrated on the surface of AFM chips with oligonucleotide molecular probes, specific against the target microRNAs. MicroRNAs, associated with the development of ASD in children, were selected as targets. The chips with immobilized molecular probes were incubated in serum samples of ASD patients and healthy volunteers. By atomic force microscopy (AFM), objects on the AFM chip surface have been revealed after incubation in the serum samples. The height of these objects amounted to 10 nm and 6 nm in the case of samples of ASD patients and healthy volunteers, respectively. MALDI-TOF-MS analysis of protein components on the chip surface allowed us to identify several cell proteins. These proteins are involved in the binding of nucleic acids (GBG10, RT24, RALYL), in the organization of proteasomes and nucleosomes (PSA4, NP1L4), and participate in the functioning of the channel of active potassium transport (KCNE5, KCNV2).

Aptamer-Sensitized Nanoribbon Biosensor for Ovarian Cancer Marker Detection in Plasma

The detection of CA 125 protein in buffer solution with a silicon-on-insulator (SOI)-based nanoribbon (NR) biosensor was experimentally demonstrated. In the biosensor, sensor chips, bearing an array of 12 nanoribbons (NRs) with n-type conductance, were employed. In the course of the analysis with the NR biosensor, the target protein was biospecifically captured onto the surface of the NRs, which was sensitized with covalently immobilized aptamers against CA 125. Atomic force microscopy (AFM) and mass spectrometry (MS) were employed in order to confirm the formation of the probe–target complexes on the NR surface. Via AFM and MS, the formation of aptamer–antigen complexes on the surface of SOI substrates with covalently immobilized aptamers against CA 125 was revealed, thus confirming the efficient immobilization of the aptamers onto the SOI surface. The biosensor signal, resulting from the biospecific interaction between CA 125 and the NR-immobilized aptamer probes, was shown to increase with an increase in the target protein concentration. The minimum detectable CA 125 concentration was as low as 1.5 × 10−17 M. Moreover, with the biosensor proposed herein, the detection of CA 125 in the plasma of ovarian cancer patients was demonstrated.

Nanowire Aptamer-Sensitized Biosensor Chips with Gas Plasma-Treated Surface for the Detection of Hepatitis C Virus Core Antigen

Herein, we have demonstrated highly sensitive real-time biospecific detection of a protein marker of hepatitis C—the core antigen of hepatitis C virus (HCVcoreAg)—using a nanowire (NW) biosensor. The primary element of the NW-biosensor is a chip with p-type conductance, bearing silicon-on-insulator (SOI) nanowire structures on its surface. The nanowire structures are fabricated by gas-plasma treatment and electron beam lithography. The detection specificity was provided by sensitization of the sensor surface with aptamers against HCVcoreAg. The influence of buffer pH on the sensor response signal was studied. The effect of reverse polarity of the biosensor response signal with change from the acidic buffer pH to the neutral one was found. The lowest detectable HCVcoreAg concentration was determined to be 2.0 × 10−15 M in both acidic (pH 5.1) and neutral (pH 7.4) buffer solution. The proposed aptamer-sensitized sensor was also successfully applied to detect HCVcoreAg in serum samples of hepatitis C patients.

Immuno-MALDI MS dataset for improved detection of HCVcoreAg in sera

Complicated and large-scale challenge the contemporary biomedical community faces are development of highly-sensitive analytical methods for detection of protein markers associated with development of pathogenic mechanisms [2]. The atomic force microscopy (AFM) method in combination with specific fishing is unique among other analytical protein detection approaches; it allows visualization and counting of single protein molecules [3–6]. The present dataset focus on mass spectrometry method for detection of human hepatitis C virus core antigen (HCV core Ag) taking into account the potential modification with cations in blood serum samples, using mica chips for the atomic force microscopy (AFM-chips). To conduct specific protein fishing, we used flat AFM-chips preliminary sensibilized with molecular probes – aptamers, which are single-stranded DNA sequences. In our study we used four types of aptamers up to 85 nucleotides specific against the target protein – HCVcoreAg [3,4]. Working (n = 19) and control (n = 11) AFM-chips with aptamers were preliminarily immobilized on the surface in four zones and incubated in blood serum samples (See Supplementary fig. 1). Analysis of MS data regarding modification of marker protein peptides with Na+, K+, K2Cl+, and Na2Cl + ions enables to enhance the reliability of target proteins detection in the serum thereby demonstrating a high diagnostic potential.

Detection of Hepatitis C Virus Core Protein in Serum Using Aptamer-Functionalized AFM Chips

In the present study, we demonstrate atomic force microscopy (AFM)-based detection of hepatitis C virus (HCV) particles in serum samples using a chip with aptamer-functionalized surface (apta-based AFM chip). The target particles, containing core antigen of HCV (HCVcoreAg protein), were biospecifically captured onto the chip surface from 1 mL of test solution containing 10 µL of serum collected from a hepatitis C patient. The registration of aptamer/antigen complexes on the chip surface was performed by AFM. The aptamers used in the present study were initially developed for therapeutic purposes; herein, these aptamers have been successfully utilized as probe molecules for HCVcoreAg detection in the presence of a complex protein matrix (human serum). The results obtained herein can be used for the development of detection systems that employ affine enrichment for protein detection.

Atomic Force Microscopy for Protein Detection and Their Physicoсhemical Characterization

This review is focused on the atomic force microscopy (AFM) capabilities to study the properties of protein biomolecules and to detect the proteins in solution. The possibilities of application of a wide range of measuring techniques and modes for visualization of proteins, determination of their stoichiometric characteristics and physicochemical properties, are analyzed. Particular attention is paid to the use of AFM as a molecular detector for detection of proteins in solutions at low concentrations, and also for determination of functional properties of single biomolecules, including the activity of individual molecules of enzymes. Prospects for the development of AFM in combination with other methods for studying biomacromolecules are discussed.

Highly sensitive protein detection by biospecific AFM-based fishing with pulsed electrical stimulation

We report here the highly sensitive detection of protein in solution at concentrations from 10-15 to 10-18 m using the combination of atomic force microscopy (AFM) and mass spectrometry. Biospecific detection of biotinylated bovine serum albumin was carried out by fishing out the protein onto the surface of AFM chips with immobilized avidin, which determined the specificity of the analysis. Electrical stimulation was applied to enhance the fishing efficiency. A high sensitivity of detection was achieved by application of nanosecond electric pulses to highly oriented pyrolytic graphite placed under the AFM chip. A peristaltic pump-based flow system, which is widely used in routine bioanalytical assays, was employed throughout the analysis. These results hold promise for the development of highly sensitive protein detection methods using nanosensor devices.

Detection of hepatitis C virus core protein in serum by atomic force microscopy combined with mass spectrometry

A method for detection and identification of core antigen of hepatitis C virus (HCVcoreAg)-containing particles in the serum was proposed, with due account taken of the interactions of proteotypic peptides with Na(+), K(+), and Cl(-) ions. The method is based on a combination of reversible biospecific atomic force microscopy (AFM)-fishing and mass spectrometry (MS). AFM-fishing enables concentration, detection, and counting of protein complexes captured on the AFM chip surface, with their subsequent MS identification. Biospecific AFM-fishing of HCVcoreAg-containing particles from serum samples was carried out using AFM chips with immobilized antibodies against HCVcoreAg (HCVcoreAgim). Formation of complexes between anti-HCVcoreAgim and HCVcoreAg-containing particles on the AFM chip surface during the fishing process was demonstrated. These complexes were registered and counted by AFM. Further MS analysis allowed reliable identification of HCVcoreAg within the complexes formed on the AFM chip surface. It was shown that MS data processing, with account taken of the interactions between HCVcoreAg peptides and Na(+), K(+) cations, and Cl(-) anions, allows an increase in the number of peptides identified.