Fluorescent sensor for bacterial recognition

doi:10.1016/j.saa.2013.02.041

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy

Volume 108, May 2013, Pages 338-341

https://doi.org/10.1016/j.saa.2013.02.041 Get rights and content

Abstract

Boronic acid-based fluorescent sensor is one of the non-enzymatic methods used for the recognition of saccharides. Since bacterial membrane has polysaccharides with diol groups, boronic acids probe could be applied for rapid bacterial recognition. Escherichia coli (XL-1 blue) were recognized by applying (3-(5-(dimethylamino) naphthalene-1-sulfonamide) phenyl) boronic acid (DNSBA) as a sensor and the fluorescence recorded by fluorometer micro-plate reader. Results showed that, fluorescence records of DNSBA increase in a dose dependent manner upon increasing the bacterial cell numbers. Moreover, the increase in the number of bacterial cells induces a shift in the spectra due to the formation of the anionic form of boronic acid complex. Therefore, DNSBA is an efficient sensor for monitoring bacterial cells.

Graphical abstract

(3-(5-(dimethylamino) naphthalene-1-sulfonamido)phenyl) boronic acid (DNSBA) were synthesized. DNSBA is considered as a biosensor for detection of Escherichia coli. There are strong interactions between boronic acid and diols in E. coli membrane. Schematic diagram representing the assembly of DNSBA on E. coli membrane through boronate ester formation with lipopolysaccharids (LPSs) layer.

Highlights

► Boronic acid-based fluorescent sensor were applied for monitoring Escherichia coli. ► Fluorescence enhancement of the sensor were observed upon increasing E. coli cells. ► Boronic acid-based sensor could be effective for monitoring E. coli cells.

Introduction

Infectious disease is the main cause of mortality in the world and the rapid increase of antibiotic resistance amongst pathogenic bacteria is becoming a serious public health problem. Antimicrobial resistance is becoming a factor in virtually all hospital-acquired infections; therefore, some bacterial infections may soon become untreatable. These concerns have led to considerable research efforts to discover alternative strategies – that could be used to identify trace amount of infectious pathogens rapidly, accurately and with high sensitivity in order to prevent epidemics and loss of lives [1]. Fluorescent sensors are proving to be promising in meeting these needs in diagnosis. One of the widely used groups of fluorescence sensing molecules is boronic acid (BA) based sensor. The development of BA based fluorescent chemo-sensors has been widely studied because of their high sensitivity and wide applicability for sugar determination [2]. Several unique characteristics of BAs make them well suited for biomedical applications. One of which is the lack of apparent toxicity whereas, Boron is present in various foods and a variety of consumer products [3].

A series of BA based saccharide sensors based on the Photoinduced electron transfer (PET) mechanism have been designed [4], [5], [6], [7], [8]. BA acts as a receptor whereas fluorophore acts as a readout unit. Moreover, the boron–nitrogen (B–N) interaction modulates the PET process and leads to fluorescence changes before and after the interaction of the BA group with saccharides [9].

The most significant chemical characteristic that has led to the efficiency of BAs in the area of biomedical applications is the ability to form reversible covalent complexes with diol [10], [11]. Although BAs sensors are sensitive, they lack specificity and thus they will bind to all diol containing compounds [12].

In previous studies the fluorescent boronic acid derivative (3-(5-(dimethylamino) naphthalene-1-sulfonamide) phenyl) boronic acid (DNSBA) was prepared and its binding properties were studied [13]. Whereas, results showed that DNSBA bound to a diol quencher via a boronic ester linkage, and this combination demonstrated fluorescence recovery upon exposure to saccharides. Therefore, DNSBA can be useful in clinical applications as a novel and safe sensor for Sugars. Since bacterial membrane has polysaccharides with diol groups [14], [15], BAs seem to be promising for the rapid monitoring and quantification of the total bacteria [16] whereas, BA receptor joins saccharides by covalent interactions to form the corresponding boronate ester [17], [18], [19]. In the current study, we attempted to use a previously synthesized DNSBA as a fluorescent sensor for bacterial detection.

Section snippets

Synthesis of boronic acid-based derivative

The BA based derivative used in the current study was typically prepared from 3-aminophenyl boronic acid and 5-(dimethylamino) naphthalene-1-sulfonyl chloride as described previously [13]. In brief, (3-(5-(dimethylamino)naphthalene-1-sulfonamide) phenyl) boronic acid (DNSBA) was synthesized by adding 10 ml of an aqueous potassium carbonate solution (50 mM) to 20 ml of a stirred solution of 3-aminophenyl boronic acid (320 mg, 2 mmol) in acetone. A solution of

Results and discussion

Boronic acids are ligands that can selectively bind with diol-compounds ‘for example’ saccharide, glycate-protein [17] and nucleotides [18]. The fluorescence spectra of the prepared DNSBA showed one band in the range of 460–660 nm with a maximum peak at 532 as found before [13] (Fig. 1); therefore fluorescence micro-plate reader with excitation at 480 nm and emission at 532 nm was used to measure the fluorescence resulting from the biosensing assay. Fluorescence enhancements of the prepared DNSBA

Conclusions

In conclusion, (3-(5-(dimethylamino) naphthalene-1-sulfonamide)phenyl)boronic acid (DNSBA) has developed as a novel sensor. DNSBA seems to be an effective sensor for monitoring the number of E. coli cells. Moreover, aggregation of DNSBA molecules due to conjugation with bacterial membrane enhance DNSBA self quenching of the fluorescence. In general, this research is a preliminary step toward developing boronic acid based microbial sensor.

Acknowledgements

This work was supported by the Bibliotheca Alexandrina, Center for Special Studies and Programs (BA/CSSP-2009).

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Short CommunicationFluorescent sensor for bacterial recognition

Abstract

Graphical abstract

Highlights

Introduction

Section snippets

Synthesis of boronic acid-based derivative

Results and discussion

Conclusions

Acknowledgements

Tetrahedron

Polymer

Anal. Chim. Acta

Biosens. Bioelectron.

Anal. Biochem.

Adv. Supramol. Chem.

Crit. Rev. Food Sci. Nutr.

J. Mater. Chem.

Org. Lett.

J. Am. Chem. Soc.

J. Org. Chem.

J. Am. Chem. Soc.

Sensors

Short Communication
Fluorescent sensor for bacterial recognition