Oriented immobilization of antibody through carbodiimide reaction and controlling electric field

Bevacizumab encapsulation into PLGA nanoparticles functionalized with immunouteroglobin-1 as an innovative delivery system for atherosclerosis

Atherosclerosis represents one of the main causes of death in the Western world. It is a multifactorial pathology characterized by lesions that reduce the lumen of the vessels causing serious clinical events. The extradomain-B of fibronectin is overexpressed during angiogenesis and in tissues undergoing growth and extensive remodeling, i.e., atherosclerotic plaque. Bevacizumab is a recombinant humanized monoclonal antibody that can play a role against the angiogenesis process reducing the risk associated with this process in atherosclerosis. In this work, an innovative drug delivery device for target delivery of bevacizumab to the atherosclerotic lesion is proposed. A production protocol for poly(lactic-co-glycolic acid)-polyethylene glycol nanoparticles loaded with bevacizumab and functionalized with immunouteroglobin-1 was designed. Once immunouteroglobin-functionalized nanoparticles were produced, they were characterized regarding morphology, mean diameter, ζ-potential, association and conjugation efficiencies, bevacizumab release profile both in phosphate buffered saline and in serum, bevacizumab stability after release, cytocompatibility, and hemocompatibility. Nanoparticle mean diameter was in the range of 217-265 nm, their surface charge was between -21 and - 8 mV, and the association and conjugation efficiency of about 76 and 59 %, respectively. Fourier transform infrared spectroscopy analysis confirmed the functionalization of their surface with immunouteroglobin-1. In vitro assays showed that the studied nanoparticles were cytocompatible, once in contact with human endothelial and murine macrophages cell line up to 72 h, and hemocompatible, once in contact with red blood cells, at different concentrations of encapsulated BEV (0.1, 1, 10, and 100 μg_BEV/mL).

Oriented immobilization of antibodies onto sensing platforms - A critical review

The immunosensor has been proven a versatile tool to detect various analytes, such as food contaminants, pathogenic bacteria, antibiotics and biomarkers related to cancer. To fabricate robust and reproducible immunosensors with high sensitivity, the covalent immobilization of immunoglobulins (IgGs) in a site-specific manner contributes to better performance. Instead of the random IgG orientations result from the direct yet non-selective immobilization techniques, this review for the first time introduces the advances of stepwise yet site-selective conjugation strategies to give better biosensing efficiency. Noncovalently adsorbing IgGs is the first but decisive step to interact specifically with the Fc fragment, then following covalent conjugate can fix this uniform and antigens-favorable orientation irreversibly. In this review, we first categorized this stepwise strategy into two parts based on the different noncovalent interactions, namely adhesive layer-mediated interaction onto homofunctional support and layer-free interaction onto heterofunctional support (which displays several different functionalities on its surface that are capable to interact with IgGs). Further, the influence of ligands characteristics (synthesis strategies, spacer requirements and matrices selection) on the heterofunctional support has also been discussed. Finally, conclusions and future perspectives for the real-world application of stepwise covalent conjugation are discussed. This review provides more insights into the fabrication of high-efficiency immunosensor, and special attention has been devoted to the well-orientation of full-length IgGs onto the sensing platform.

Study on covalent coupling process and flow characteristics of antibody on the surface of immunoassay microfluidic chip

The immune response system of immunoassay microfluidic chips is a dynamic reaction process that continuously sends reactants to the surface of a solid carrier. Signal acquisition results from the heterogeneous immune reactions and reactant transport. Antibody immobilization is the most important part of heterogeneous immune reactions, and reactant transport is reflected in the form of fluid velocity. Here, we reported several surface modification processes on polystyrene substrates that are employed to study the relationship between the antibody immobilization and flow behavior in heterogeneous immune response processes. The antibody was immobilized using covalent grafting. Based on the mechanism of sandwich enzyme linked immunosorbent assay, a fluorescence quantitative detection method was used to evaluate the immune response process. The effects of different surface modification processes on immune response and flow behavior were studied. We identified an optimal flow velocity in the dynamic immune response system in the microfluidic chip. The immune response signal was the strongest when the average flow velocity was approximately 0.2 mm/s in the procalcitonin detection system. Compared with the amino and aldehyde group substrates, the epoxy group substrate has the highest antibody immobilization efficiency; compared with the surface modified by small molecular groups, the introduction of Poly-L-Lysine can increase the amount of antibody immobilization.

Single-step label-free nanowell immunoassay accurately quantifies serum stress hormones within minutes

A non-faradaic label-free cortisol sensing platform is presented using a nanowell array design, in which the two probe electrodes are integrated within the nanowell structure. Rapid and low volume (≤5 μl) sensing was realized through functionalizing nanoscale volume wells with antibodies and monitoring the real-time binding events. A 28-well plate biochip was built on a glass substrate by sequential deposition, patterning, and etching steps to create a stack nanowell array sensor with an electrode gap of 40 nm. Sensor response for cortisol concentrations between 1 and 15 μg/dl in buffer solution was recorded, and a limit of detection of 0.5 μg/dl was achieved. Last, 65 human serum samples were collected to compare the response from human serum samples with results from the standard enzyme-linked immunosorbent assay (ELISA). These results confirm that nanowell array sensors could be a promising platform for point-of-care testing, where real-time, laboratory-quality diagnostic results are essential.

Antibody-Oriented Strategy and Mechanism for the Preparation of Fluorescent Nanoprobes for Fast and Sensitive Immunodetection

Nanoprobes have been widely used in biomedical engineering. However, antibodies are generally conjugated onto nanoparticles disorderly, which reduces their antigen recognition ability. The existing antibody orientation approaches are usually complex. Here, we developed and demonstrated a simple antibody-oriented strategy for the lateral flow immunoassay of cardiac troponin I by conjugating antibodies onto polystyrene nanospheres at the optimal pH. The binding amount and orientation of antibodies as well as the detection sensitivity were significantly improved. Although pH regulation is commonly used to optimize antibody conjugation, this paper illustrates the mechanism of its antibody orientation enhancement ability for the first time and reveals the important influences of the density, the charge distribution and hydrophilicity of the antibody, the control of the velocities of physical adsorption and chemical coupling, and other factors on antibody orientation. It is of great significance to understand and regulate antibody conjugation on the surface of micro- or nanospheres to construct high-performance probes for in vitro diagnosis applications.

Hapten-Grafted Programmed Probe as a Corecognition Element for a Competitive Immunosensor to Detect Acetamiprid Residue in Agricultural Products

We have developed an effective competitive electrochemical immunosensor assay based on hapten-grafted programmed probe (HGPP) as a corecognition element for highly sensitive and selective detection of acetamiprid. Starting with the synthesis of hapten, HGPP was prepared using carboxyl group in the hapten and amino group in the 5' end of the programmed probe through covalent conjugation. Acetamiprid present in samples competes with HGPP to bind with capture antibody on the electrodes by specific recognition interaction. Methylene blue probe (MBP) was used as the electrochemical redox probe to capture the hybridized HGPP on the electrodes. The competitive reaction changes in accordance with the quantity of the target acetamiprid in the sample, as the amounts of the hybridized HGPP and the immobilized antibody are constant, i.e., the more acetamiprid samples are added, the less MBP is combined on the electrodes. In the optimal conditions, thus, biosensor output showed a linear relationship from 5 to 10⁵ ng L^-1 for the acetamiprid assay with a detecting limit of 3.2 ng L^-1. The biosensor was successful in quantifying the amount of acetamiprid in spiked strawberry and cabbage extracts. This competitive immunosensor assay represents a rapid and sensitive technology for acetamiprid assay or other small molecule targets in food.