Fluorescence enhancement of fluorescein isothiocyanate-labeled protein a caused by affinity binding with immunoglobulin g in bovine plasma

Nanoporous Polystyrene Inverse Opal Materials with Optical Interference Properties for Label-Free Biosensing

Colloidal crystal nanomaterials have been proven to be valuable substrates for optical-based biosensing due to their ordered macroporous nanostructure and brilliant optical properties. In this work, silica colloidal crystal (SCC) thin films, as well as polystyrene-SCC composite films and inverse opal (IO) polystyrene films fabricated using SCC as templates, are investigated for their application as substrate materials in optical interferometric biosensors. The SCC films formed by the self-assembly of silica colloidal crystals have the most densely packed nano-3D structure, also known as the opal structure. IO films are fabricated by filling the opal pores of SCC with polystyrene and then removing the template, resulting in an interconnected nano-3D ordered macroporous structure, as indicated by the name inverse opal. The performance of the three materials was compared and discussed based on an ordered porous layer interferometry optical platform, focusing on refractive index response, protein adsorption response, and biomolecular interaction response. These results could potentially offer innovative material support for the advancement of label-free optical biosensors, which can be used for more biological/biochemical/biomolecular reaction monitoring studies.

Antibody mix-and-read assays based on fluorescence intensity probes

Antibodies and Fc fusion proteins are a rapidly growing class of pharmaceuticals. Cell culture and purification process development and operation require frequent measurement of product concentrations, commonly by complex enzyme-linked immunosorbent assay and high-performance liquid chromatography methods. Here we report a fast (<30 s), and simple antibody Fc assay based on mix-and-read reporting by fluorescence emission. A soluble fluorescein-labeled Fc-affinity reporter produced by standard peptide synthesis is mixed with an Fc-containing sample to produce an immediate shift in both fluorescence polarization and intensity, compatible with on- and at-line measurements and microbioreactor monitoring. We observed significant shifts in fluorescence intensity in Chinese hamster ovary cell culture fluid spiked with IgG and detected an adalimumab biosimilar down to 100 ng/mL (10^-4 g/L), despite the interferents in the complex sample matrix. Neither the fluorescence polarization nor the fluorescence intensity assay is significantly affected by the addition of clarified lysate of 2 million CHO-k1 cells/mL, suggesting applicability even to cultures of low viability. Biochemical and molecular docking approaches suggest that the fluorescence intensity enhancement is caused by changes in the fluorophore's local microenvironment upon binding to IgG Fc, especially by interactions with Fc His433.Abbreviations: CCF: Cell Culture Fluid; CHO: Chinese Hamster Ovary cells; ELISA: Enzyme Linked Immunosorbent Assay; Fc: Fragment Crystallizable of antibody; HPLC: High-Performance Liquid Chromatography; HPβCD: hydroxypropyl-β-cyclodextrin; IgG: ImmunoglobulinG; mAb: Monoclonal Antibody; PBS: Phosphate-Buffered Saline; PDB: Protein Data Bank; SpA: Staphylococcal protein A; SpG: Staphylococcal protein G.

The Spectrophotometric Characteristic of Immunoglobulin Conjugates for Diagnostics of Causative Agents of Especially Dangerous Infections

The possibility of characterizing fluorescent immunoglobulins using spectrophotometric analysis as a testing method is considered. The comparative analysis of optical properties of fluorescent immunoglobulin preparations and their components-immunoglobulins and fluorochrome-is carried out. The obtained results testify that the proposed methodological approach of optical detection of labeled immunoglobulin molecules can be promising for tests on obtaining conjugates used in immunological tests on revealing specific antigens of causative agents of especially dangerous infections.

Facile fabrication of poly(acrylic acid) coated chitosan nanoparticles with improved stability in biological environments

Chitosan is one of the most important and commonly used natural polysaccharides in drug delivery for its biocompatible and biodegradable properties. However, poor blood circulation of the chitosan nanoparticles due to their cationic nature is one of the major bottlenecks of chitosan-based drug delivery systems. To address this problem, a versatile platform based on poly(acrylic acid) (PAA) coated ionically cross-linked chitosan/tripolyphosphate nanoparticles (CTS/TPP-PAA NPs), is reported. The zeta potentials of CTS/TPP and CTS/TPP-PAA NPs are approximately 33mV and -25mV, respectively. CTS/TPP NPs quickly aggregate in PBS (phosphate buffered saline) and DMEM (Dulbecco's modified Eagle's medium). Conversely, CTS/TPP-PAA NPs exhibit excellent colloidal stability in plasma solution for more than 24h. The PAA coating also endows CTS/TPP-PAA NPs with decreased protein adsorption capacity and improved buffering capacity. More importantly, the residual carboxyl and amino groups on CTS/TPP-PAA NPs provide abundant reactive sites for further functional modifications. Therefore, the CTS/TPP-PAA NPs reported here may be useful as an alternative drug delivery system.

Hyaluronic acid-supported combination of water insoluble immunostimulatory compounds for anti-cancer immunotherapy

A novel powder-form combination adjuvant system containing two immunostimulatory compounds was firstly developed and evaluated as a therapeutic intervention for cancer immunotherapy. With the help of hyaluronic acid (HA), water insoluble monophosphoryl lipid A (MPL), QS21 and imiquimod (R837), could be easily dispersed in aqueous solution and lyophilized as powder-form, which have an advantage in room-temperature storage stability compared with those conventional liquid formulation that requires cold storage. Two kinds of HA-based combination vaccine adjuvants (HA/MPL/QS21, HMQ and HA/MPL/R837, HMR) contributed to the increase of both humoral and cellular immunity, which is very important for efficient cancer immunotherapy. Through the challenge experiments in EG7-OVA (mouse lymphoma-expressing OVA) tumor-bearing mice model, we found out that the immunostimulatory effects of HMQ and HMR were successful in the inhibition of tumor proliferation. Taken together, both HA-based powder-form combination adjuvant systems are expected to be used as potent prophylactic and therapeutic cancer vaccine.

Quantization of bovine serum albumin by fluorescence enhancement effects and corresponding binding of macrocyclic host-protein assembly

The present paper reports the investigations on the spectroscopic behavior of the binary complexes of the dye aurintricarboxylic acid (ATA) with protein bovine serum albumin (BSA) and 18-crown 6 (CW) (ATA·BSA, ATA·CW) and the ternary complex ATA·CW·BSA by using UV-vis steady state and time resolved fluorescence spectroscopy. The primary aim of the work is to determine the protein (BSA) quantization by fluorescence enhancement method and investigate the 'enhancer' activity of crown ether (CW) on it to increase the resolution. Steady state and time resolved fluorescence measurements demonstrated how fluorescence intensity of ATA could be used for the determination of the protein BSA in aqueous solution. The binding of dye (probe/fluorescent medicinal molecule) with protein and the denaturing effect in the polar environment of acetonitrile of the dye protein complex act as drug binding as well as drug release activity. Apart from its basic research point of view, the present study also possesses significant importance and applications in the field of medicinal chemistry.