Sara Puertas

Taking Advantage of Unspecific Interactions to Produce Highly Active Magnetic Nanoparticle−Antibody Conjugates

Several strategies for linking antibodies (Abs) through their Fc region in an oriented manner have been proposed at the present time. By using these strategies, the Fab region of the Ab is available for antigen molecular recognition, leading to a more efficient interaction. Most of these strategies are complex processes optimized mainly for the functionalization of surfaces or microbeads. These methodologies imply though the Ab modification through several steps of purification or the use of expensive immobilized proteins. Besides, the functionalization of magnetic nanoparticles (MNPs) turned out to be much more complex than expected due to the lack of stability of most MNPs at high ionic strength and non-neutral pH values. Therefore, there is still missing an efficient, easy and universal methodology for the immobilization of nonmodified Abs onto MNPs without involving their Fab regions during the immobilization process. Herein, we propose the functionalization of MNPs via a two-steps strategy that takes advantage of the ionic reversible interactions between the Ab and the MNP. These interactions make possible the orientation of the Ab on the MNP surface before being attached in an irreversible way via covalent bonds. Three Abs (Immunoglobulin G class) with very different isoelectric points (against peroxidase, carcinoembryonic antigen, and human chorionic gonadotropin hormone) were used to prove the general applicability of the strategy here proposed and its utility for the development of more bioactive NPs.

Designing novel nano-immunoassays: antibody orientation versus sensitivity

There is a growing interest in the use of magnetic nanoparticles (MNPs) for their application in quantitative and highly sensitive biosensors. Their use as labels of biological recognition events and their detection by means of some magnetic method constitute a very promising strategy for quantitative high-sensitive lateral-flow assays.In this paper, we report the importance of nanoparticle functionalization for the improvement of sensitivity for a lateral-flow immunoassay. More precisely, we have found that immobilization of IgG anti-hCG through its polysaccharide moieties on MNPs allows more successful recognition of the hCG hormone.Although we have used the detection of hCG as a model in this work, the strategy of binding antibodies to MNPs through its sugar chains reported here is applicable to other antibodies. It has huge potential as it will be very useful for the development of quantitative and high-sensitive lateral-flow assays for its use on human and veterinary, medicine, food and beverage manufacturing, pharmaceutical, medical biologics and personal care product production, environmental remediation, etc.

Improving immunosensor performance through oriented immobilization of antibodies on carbon nanotube composite surfaces

We report the straightforward oriented covalent attachment of antibodies (Abs) on the surface of carboxylated multiwalled carbon nanotube-polystyrene (MWCNT-PS) materials. The combination of this composite material, applied as a robust electrochemical transducer platform, and its covalent functionalization with Abs in a controlled way by means of a two-step process, could contribute to the development of highly sensitive immunosensor devices. Using the simple and versatile carbodiimide chemistry, Abs were attached to the carboxylic groups of the MWCNT-PS composite surfaces via their superficial amine groups. By taking into account the Ab isoelectric point and the net charge of the composite surface, we engineered an immobilization process to achieve the oriented binding of the Ab molecules by favoring an ionic pre-adsorption step before covalent binding occurred. Thus, the antigen binding capacity of the attached Abs was enhanced by up to 10 times with respect to the capacity estimated for a random spatial distribution of these molecules. The proposed strategy would also serve as a model for the efficient biofunctionalization of other carboxylated carbon-based polymer composite materials with potential applications in the biosensor field.

Tips for the functionalization of nanoparticles with antibodies.

Multiple antibody immobilization methodologies have been developed for several applications including affinity chromatography, immunosensing, and drug delivery. Most of them have been carried out without considering the orientation of the antigen binding site of the antibody, or after the chemical modification of the antibody. An efficient immobilization to improve the biological activity of the antibody is one of the key fundamental issues to pursue. A simple and effective methodology for well-oriented covalently immobilization of antibodies on nanoparticles is reported in this chapter.

Surface engineered magnetic nanoparticles for specific immunotargeting of cadherin expressing cells

This work was supported by SAF2014-54763-C2-R (Ministerio de Economia y Competitividad), ERC-Starting Grant 239931-NANOPUZZLE project, Fondo Social Europeo (FSE; Gobierno de Aragon), Communaute de Travail des Pyrenees (P5/13 Gobierno de Aragon and 13010774 Region Aquitaine), SUDOE Train2 program and institutional funding from CNRS. BS was supported by a post-doctoral fellowship from the Instituto de Salud Carlos III in the Sara Borell program.

Chapter 10 - Biosensors Based on Nanoparticles and Electrochemical Detection

Abstract Gold nanoparticles (GNPs) have been used for analytical and biomedical purposes for many years. Rapid and simple chemical synthesis, optical, electrical, and catalytic properties, a narrow size distribution, a large surface-to-volume ratio, and efficient coating by thiols, and other bioligands have made AuNPs ideal transducers for several biorecognition binding applications. The availability of a versatile chemistry for further functionalization of AuNP surface allows the coupling of biomolecules such as proteins (enzymes, antibodies) or DNA to AuNPs, and these bioconjugates provide a useful platform for their application in biomedical diagnostics and analytics. These biomolecular recognition events occurring at the nanoparticle surface have an influence on the optical and/or electrical properties of the system allowing the development of more sensitive and flexible sensing systems. In this chapter, we describe recent advances in the field of AuNPs for sensing applications based on their unique physical properties.