Nanoplasmonic Biosensing Approach for Endotoxin Detection in Pharmaceutical Field

Adriano Colombelli,Elisabetta Primiceri,Giuseppe Maruccio,Maria Grazia Manera,Anna Grazia Monteduro,Roberto Rella,Silvia Rizzato

doi:10.3390/chemosensors9010010

Abstract

The outer membrane of Gram-negative bacteria contains bacterial endotoxins known as Lipopolysaccharides (LPS). Owing to the strong immune responses induced in humans and animals, these large molecules have a strong toxic effect that can cause severe fever, hypotension, shock, and death. Endotoxins are often present in the environment and medical implants and represent undesirable contaminations of pharmaceutical preparations and medical devices. To overcome the limitations of the standard technique, novel methods for early and sensitive detection of LPS will be of crucial importance. In this work, an interesting approach for the sensitive detection of LPS has been realized by exploiting optical features of nanoplasmonic transducers supporting Localized Surface Plasmon Resonances (LSPRs). Ordered arrays of gold nano-prisms and nano-disks have been realized by nanospheres lithography. The realized transducers have been integrated into a simple and miniaturized lab-on-a-chip (LOC) platform and functionalized with specific antibodies as sensing elements for the detection of LPS. Interactions of specific antibodies anchored on protein A-modified sensor chips with the investigated analyte resulted in a spectral shift in the plasmonic resonance peak of the transducers. A good linear relationship between peak shifts and the LPS concentration has been demonstrated for the fabricated nano-structures with a detection limit down to 5 ng/mL. Integration with a proper microfluidic platform demonstrates the possibility of yielding a prototypal compact device to be used as an analytical test for quality determination of pharmaceutical products.

Highlights

Bacterial endotoxins are the most common and dangerous contaminants found in the finished pharmaceutical preparations and medical devices, which is why Pharmacopoeias strictly regulate its content limits.The outer membrane of Gram-negative bacteria contains a series of bacterial endotoxins known as Lipopolysaccharides (LPS); each cell can contain over two million copies [1].Their function is to screen off damaging compounds, while letting nutrients pass
These large molecules consist of a hydrophobic domain, oligosaccharide core, and a polysaccharide domain known as O-antigen that is responsible for their toxic effect due to the strong immune responses induced in humans and animals
We propose a sensitive biosensing approach exploiting optical and physicochemical properties of plasmonic nanostructures: their ability to concentrate light energy in nanoscale volumes, and subsequently, the increased near field intensity by several orders of magnitude with respect to incident light makes them a valuable transducing platform for endotoxin detection

Summary

Introduction

The outer membrane of Gram-negative bacteria contains a series of bacterial endotoxins known as Lipopolysaccharides (LPS); each cell can contain over two million copies [1]. Their function is to screen off damaging compounds, while letting nutrients pass. Their release into the surrounding medium mainly happens during cell growth and division as well as during cell death. Endotoxins may be introduced into the bloodstream through contaminated intravenous devices or medications The release of such pyrogenic compounds may lead to a rapid inflammation reaction resulting in fever, inflammation, endotoxemia, and septic shock followed in some

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