Spectroscopic properties of various blood antigens/antibodies

Analytical Techniques for the Characterization and Quantification of Monoclonal Antibodies

Monoclonal antibodies (mAbs) are a fast-growing class of biopharmaceuticals. They are widely used in the identification and detection of cell makers, serum analytes, and pathogenic agents, and are remarkably used for the cure of autoimmune diseases, infectious diseases, or malignancies. The successful application of therapeutic mAbs is based on their ability to precisely interact with their appropriate target sites. The precision of mAbs rely on the isolation techniques delivering pure, consistent, stable, and safe lots that can be used for analytical, diagnostic, or therapeutic applications. During the creation of a biologic, the key quality features of a particular mAb, such as structure, post-translational modifications, and activities at the biomolecular and cellular levels, must be characterized and profiled in great detail. This implies the requirement of powerful state of the art analytical techniques for quality control and characterization of mAbs. Until now, various analytical techniques have been developed to characterize and quantify the mAbs according to the regulatory guidelines. The present review summarizes the major techniques used for the analyses of mAbs which include chromatographic, electrophoretic, spectroscopic, and electrochemical methods in addition to the modifications in these methods for improving the quality of mAbs. This compilation of major analytical techniques will help students and researchers to have an overview of the methodologies employed by the biopharmaceutical industry for structural characterization of mAbs for eventual release of therapeutics in the drug market.

Spectroscopic Characteristics of Xeloda Chemodrug

Introduction: Spectroscopic properties of Xeloda chemodrug have been studied over varying concentrations ranging between 0.001 and 10 mg/mL, using laser-induced fluorescence (LIF) spectroscopy. The alternative photoluminescence (PL) and near infrared (NIR) measurements are carried out to authenticate the obtained results by the LIF method. Methods: The XeCl laser as the excitation coherent source with 160 mJ/pulse at 308 nm is employed for LIF measurements of the fluorophore of interest in the modular spectroscopic set-up. Results: Xeloda as a significant chemodrug acts as a notable fluorophore. LIF, PL and NIR spectroscopy techniques are employed to investigate the spectral properties of the chemodrug in terms of concentration. The maximum LIF peak intensity of Xeloda is achieved at λmax=410.5 nm and the characteristic concentration of CP1=0.05 mg/mL. PL signals are in good agreement with the data given by the LIF measurements. The characteristic NIR spectra of Xeloda as solid evidence of chemical bonding formation attest to fluorescence quenching at the fluorophore concentration of ~ 0.2 mg/ mL. Besides, the spectral shift of fluorescence signals which is obtained in terms of fluorophore concentration- demonstrating as a diagnostic marker for the purpose of optimized chemotherapy. Conclusion: Xeloda exhibits outstanding fluorescence properties over the allowable concentration in human serum (Cmax). These characteristics could benefit potential advantage of simultaneous laser-based imaging of cell-chemodrug interaction over in-vivo studies.

Fluorescence emission quenching of RdB fluorophores in attendance of various blood type RBCs based on Stern-Volmer formalism

In this work, the optical properties of Rhodamine B (RdB) are investigated in the attendance of various red blood cells (RBCs). RdB fluorophores, as biological markers, is excited using SHG-CW Nd:YAG laser at 532 nm. In fact, the addition of biomolecules of interest to the reference fluorophore notably changes the fluorescence properties of the suspension. Here, laser induced fluorescence (LIF) spectrophotometry based on Stern-Volmer quenching formalism and field emission scanning electron microscope (FESEM) are employed here. According to the given fluorescence spectra, the spectral shift of emissions as well as quenching coefficients are assessed subsequently. The Stern-Volmer formalism is used to determine the quenching coefficients. In fact, RdB + RBCs suspensions contain a plenty of bioconjugates leading to the signal reduction and notable red shift in RdB fluorescence emissions. Furthermore, it is demonstrated that the positive blood type RBCs exhibit the higher quenching coefficients and the larger red shifts against those of negative blood types. This mainly arises from the nature of specific sugar antigens available on the RBC membranes as to N-acetylgalactosamine and galactose attached to the O-antigen terminal would enhance further quenching of the species. Moreover, a significant correlation appears between Stern-Volmer coefficients and the corresponding RBCs. In fact, distinct discrepancy takes place in quenching coefficients in terms various positive/negative blood types to envisage a facile method of blood typing.

Au-coated Fe3O4 core-shell nanohybrids with photothermal activity for point-of-care immunoassay for lipoprotein-associated phospholipase A2 on a digital near-infrared thermometer

A portable photothermal immunoassay based on Au-coated magnetic Fe₃O₄ core-shell nanohybrids (Au-Fe₃O₄) was developed for point-of-care (POC) testing of lipoprotein-associated phospholipase A₂ (Lp-PLA₂) on a digital near-infrared (NIR) thermometer. Au-Fe₃O₄ photothermal materials were first synthesized through reverse micelle method, and then functionalized with polyclonal rabbit anti-human Lp-PLA₂ antibody. A sandwiched immunoreaction was carried out in polyclonal mouse anti-human Lp-PLA₂ antibody-coated microplate using Au-Fe₃O₄-labeled antibody as the detection antibody. With formation of sandwich-type immunocomplex, the captured Au-Fe₃O₄ on the plate converted the light into heat under an 808-nm laser irradiation (1.5 W cm^-2), thereby resulting in the increasing temperature of the detection solution. The temperature variations relative to surrounding temperature was determined on a portable NIR thermometer. Several labeling protocols with gold nanoparticle, Fe₃O₄ nanoparticle, or Au-Fe₃O₄ nanohybrids were investigated for determination of Lp-PLA₂ and improved analytical features were achieved with the core-shell Au-Fe₃O₄ nanohybrids. Under optimum conditions, Au-Fe₃O₄-based immunoassay exhibited good photothermal responses for the detection of Lp-PLA₂ with a dynamic linear range of 0.01-100 ng mL^-1 at a low detection limit of 8.6 pg mL^-1. Good reproducibility and intermediate precision were less than 9.7%. Other biomarkers or proteins did not interfere with responses of this system. An acceptable accuracy was acquired for analysis of human serum sample between Au-Fe₃O₄-based photothermal immunoassay and commercialized human Lp-PLA₂ ELISA kit.