Antibody Epitope and Affinity Determination of the Myocardial Infarction Marker Myoglobin by SPR-Biosensor Mass Spectrometry

Surface-enhanced Raman spectroscopy for the characterization of filtrate portions of blood serum samples of myocardial infarction patients using 30 kDa centrifugal filter devices

Myocardial infarction (MI) is the leading cause of death and disability worldwide. It occurs when a thrombus forms after an atherosclerotic plaque bursts, obstructing blood flow to the heart. Prompt and accurate diagnosis is crucial for improving patient survival. Surface-enhanced Raman spectroscopy (SERS) offers quick response and excellent resolution for qualitative and quantitative analysis of body fluids, making it a valuable diagnostic tool. This study explores SERS for identifying proteins in blood serum samples from MI patients, focusing on cardiac Troponin I (cTnI), a key biomarker. Due to the small size and low concentration of cTnI, its SERS signal may be weak or absent. To address this, 30 kDa filtering devices are used to obtain filtrate portions of serum samples from cTnI-positive patients and healthy individuals. SERS spectral analysis of these filtrates identifies key SERS bands associated with biomolecular changes related to cTnI levels. Principal component analysis (PCA) effectively differentiates SERS spectra from healthy and MI-positive patients. Partial least squares regression (PLSR) quantifies cTnI levels based on SERS features, with a model showing R2 value of 0.79 and RMSEC of 1.37, validating its accuracy.

Target-regulated Ag2S/FeOOH heterojunction activity: a direct label-free photoelectrochemical immunosensor

Myoglobin (Mb), an important cardiac marker, plays a crucial role in diagnosing, monitoring, and evaluating the condition of patients with cardiovascular diseases. Here, we propose a label-free photoelectrochemical (PEC) sensor for the detection of Mb through target regulated the photoactivity of Ag2S/FeOOH heterojunction. The Ag2S/FeOOH nanospindles were synthesized and served as a sensing platform for the fabrication of bio-recognized process for Mb. Mb-aptamer was used as the responsive group to grasp the target Mb in a real sample due to its advantages of strong affinity, high stability, and ease of preparation. Mb-aptamer immunocomplex is formed in the presence of Mb, which hinders the interfacial electron transfer and then reduce the photocurrent. The proposed PEC aptasensor exhibited excellent analytical performance including wide linear range (1.0 pg mL-1 ~ 50 ng mL-1), low limit of detection (0.28 pg mL-1), and good selectivity and stability. This work introduces an innovative approach to PEC aptasensor, offering a promising method for precise determination of human biomarkers.

Fluorescence turn-off detection of myoglobin as a cardiac biomarker using water-stable L-glutamic acid functionalized cesium lead bromide perovskite quantum dots

Water dispersible L-glutamic acid (Glu) functionalized cesium lead bromide perovskite quantum dots (CsPbBr3 PQDs), namely CsPbBr3@Glu PQDs were synthesized and used for the fluorescence "turn-off" detection of myoglobin (Myo). The as-prepared CsPbBr3@Glu PQDs exhibited an exceptional photoluminescence quantum yield of 25% and displayed emission peak at 520 nm when excited at 380 nm. Interestingly, the fluorescence "turn-off" analytical approach was designed to detect Myo using CsPbBr3@Glu PQDs as a simple optical probe. The developed probe exhibited a wide linear range (0.1-25 µM) and a detection limit of 42.42 nM for Myo sensing. The CsPbBr3@Glu PQDs-based optical probe provides high ability to determine Myo in serum and plasma samples.

Epitope characterization of proteins and aptamers with mass spectrometry

The way in which professor Michael Przybylski has combined the spirit of research with entrepreneurship has set an example for any and all scientists. He has made significant achievements in the fields of mass spectrometry, biochemistry and medicine, and has initiated important technological developments in the area of protein analysis. Between 2016 and 2023 professor Przybylski's scientific focus shifted on protein interactions with emphasis on aptamer-protein and antibody-protein analysis. This review focuses on professor Przybylski's achievements in the last few years highlighting his impact on the scientific community, on his students and colleagues.

A Novel Rabbit Anti-Myoglobin Monoclonal Antibody's Potential Application in Rhabdomyolysis Associated Acute Kidney Injury

Myoglobin (Mb) is the main constituent of vertebrate skeletal muscle and myocardium and plays an essential role in oxygen binding, storage, transport, and earliest disease diagnosis. This study focuses on preparing the novel recombinant rabbit anti-Mb monoclonal antibody and applying it to a diagnosis of Mb deposition in rhabdomyolysis-associated acute kidney injury (RM-AKI). The full-length coding sequence of rat Mb was cloned and expressed, and the high-quality and titer rabbit anti-Mb polyclonal antibodies were produced by the immunogen His-Mb fusion protein. A new hybridoma cell was obtained by hybridoma screening technology. With the help of DNA sequencing and a molecular clonal, anti-Mb monoclonal antibody heavy and light chains expression plasmid was constructed. Finally, the recombinant rabbit anti-Mb monoclonal antibody with extraordinarily high affinity (K_D = 1.21 pM) was obtained. Meanwhile, it had broad species reactivity (mouse, rat, human, and horse) and good tissue specificity (skeletal muscle and myocardium). It also had a very good performance in western blotting, immunohistochemistry, and immunofluorescence assay to detect the Mb level in the kidney, myocardium, and skeletal muscle of RM-AKI. This study will be significantly helpful for Mb-associated disease diagnosis, and pathogenesis exploration, and further may act as a neutralizing antibody for disease treatment.

Identification and Affinity Determination of Protein-Antibody and Protein-Aptamer Epitopes by Biosensor-Mass Spectrometry Combination

Analytical methods for molecular characterization of diagnostic or therapeutic targets have recently gained high interest. This review summarizes the combination of mass spectrometry and surface plasmon resonance (SPR) biosensor analysis for identification and affinity determination of protein interactions with antibodies and DNA-aptamers. The binding constant (KD) of a protein-antibody complex is first determined by immobilizing an antibody or DNA-aptamer on an SPR chip. A proteolytic peptide mixture is then applied to the chip, and following removal of unbound material by washing, the epitope(s) peptide(s) are eluted and identified by MALDI-MS. The SPR-MS combination was applied to a wide range of affinity pairs. Distinct epitope peptides were identified for the cardiac biomarker myoglobin (MG) both from monoclonal and polyclonal antibodies, and binding constants determined for equine and human MG provided molecular assessment of cross immunoreactivities. Mass spectrometric epitope identifications were obtained for linear, as well as for assembled ("conformational") antibody epitopes, e.g., for the polypeptide chemokine Interleukin-8. Immobilization using protein G substantially improved surface fixation and antibody stabilities for epitope identification and affinity determination. Moreover, epitopes were successfully determined for polyclonal antibodies from biological material, such as from patient antisera upon enzyme replacement therapy of lysosomal diseases. The SPR-MS combination was also successfully applied to identify linear and assembled epitopes for DNA-aptamer interaction complexes of the tumor diagnostic protein C-Met. In summary, the SPR-MS combination has been established as a powerful molecular tool for identification of protein interaction epitopes.

Development of a novel ssDNA aptamer targeting cardiac troponin I and its clinical applications

Cardiac troponin I (cTnI) is a specific biomarker of acute myocardial infarction (AMI). However, cTnI detection kits prepared with antibodies have many defects. Nucleic acid aptamers are sequences of single-strand DNA or RNA that can overcome the deficiency of antibodies. Herein, sandwich ELONA methods were established based on aptamers. Two selected ssDNA aptamers (Apt3 and Apt6) showed high binding affinity and sensibility (Apt3: Kd = 1.01 ± 0.07 nM, Apt6: k = 0.68 ± 0.05) and did not bind to the same domain of cTnI. Therefore, these two aptamers can be applied to the ELONA methods. The detection range of cTnI using the dual-aptamer sandwich ELONA method was 0.05-200 ng/mL, and the bioanalytical method verification results can meet the national standard of Chinese Pharmacopoeia (2020 Edition). There was no difference between results of the dual-aptamer sandwich ELONA method and the diagnostic results of serum obtained from 243 people (P = 0.39, P ˃ 0.05). The sensitivity and specificity of the ELONA with cTnI in serum were 96.46% and 93.85%, respectively. Compared with the FICA kit, which is clinically used, the consequences of ELONA method are closer to the diagnostic results. This study suggests that the aptamers Apt3 and Apt6 have high affinity and strong specificity and that the dual-aptamer sandwich ELONA method has a wide detection range and can be used to determine cTnI in serum, with potential applications in the diagnosis of AMIs.