Rapid Fluorescence Quenching Detection of Escherichia coli Using Natural Silica-Based Nanoparticles

Abstract

The development of fluorescent silica nanoparticles (SNP-RB) from natural amorphous silica and its performance as an Escherichia coli (E. coli) biosensor is described in this paper. SNP-RB was derived from silica recovered from geothermal installation precipitation and modified with the dye, Rhodamine B. The Fourier Infrared (FTIR) confirms the incorporation of Rhodamine B in the silica matrix. Transmission Electron Microscopy (TEM) micrographs show that the SNP-RB had an irregular structure with a particle diameter of about 20–30 nm. The maximum fluorescence spectrum of SNP-RB was recorded at 580 nm, which was further applied to observe the detection performance of the fluorescent nanoparticles towards E. coli. The sensing principle was based on the fluorescence-quenching mechanism of SNP-RB and this provided a wide linear E. coli concentration range of 10–105 CFU/mL with a limit detection of 8 CFU/mL. A rapid response time was observed after only 15 min of incubation of SNP-RB with E. coli. The selectivity of the biosensor was demonstrated and showed that the SNP-RB only gave quenching response only to live E. coli bacteria. The use of SNP-RB as a sensing platform reduced the response time significantly compared to conventional 3-day bacterial assays, as well having excellent analytical performance in terms of sensitivity and selectivity.

Recent Advances in the Use of Mesoporous Silica Nanoparticles for the Diagnosis of Bacterial Infections

“… Hemin encapsulated, DNA gated MSN E. coli O157:H7 (ATCC 35150) S. aureus (ATCC 25923) Chemiluminescence 3.0 CFU/mL 2.5 CFU/mL [ 76 ] Different sized SiO2-NP E. coli Electrochemical – [ 78 ] Anti- E. coli Ab-grafted SiO2-NP E. coli MRE 162 Electrochemical 2x10 3 CFU/mL [ 79 ] MSN@CUR@ZnO@pAbs nanoparticles (MCZP NPs) S . Typhimurium Colorimetric Fluorescence 63 CFU/mL 40 CFU/mL [ 86 ] Rhodamine B modified silica nanoparticles (SNP-RB) E. coli (InaCC-B5) Fluorescence 8 CFU/mL [ 87 ] Aptamer-functionalized silica magnetic nanoparticles S. aureus Fluorescence 682 CFU/mL [ 94 ] Abbreviations: MSN, mesoporous silica nanoparticle; SiO2-NP, non-porous silica nanoparticle; Ab, antibody; MSN@CUR@ZnO@pAbs, mesoporous silica nanoparticle@curcumin@zinc oxide@polyclonal antibody. …”

“… 92 In this sense, the optical properties of MSN are intensively exploited to design optical biosensors with the desired features for bacterial detection. 93 , 94 Remarkably, MSN is inert against photons as well as optically transparent and presents fascinating platform to construct novel, stable optical sensors with sensitivity and rapid response. 95 , 96 Sol-gel approaches are employed for the production of MSN and superior possibilities for the incorporation of conventional luminophores (organic dyes) and inorganic luminophores by employing in situ incorporation strategies, for instance by employing approaches in Figure 3A .…”

“…From the standpoint of silica based transducer development, Jenie et al have developed Rhodamine B (RB), a well-known as a pink fluorescent dye, incorporated silica NPs (SNP-RB) from natural amorphous silica and investigated its performance as E. coli biosensor. 94 The sensing principle was designed by the fluorescence-quenching mechanism of SNP-RB and a wide linear E. coli concentration range of 10–10 5 CFU/mL could be obtained with a LOD of 8 CFU/mL. 94 In practice, the preparation of SNP-RB was carried out by employing co-condensation of RB into silica matrix and no structural changes of SNP was presented to compare with/without RB incorporation, and the obtained results were only concluded as to be sufficient enough to meet the demanded sensitivity and selectivity for E. coli .…”

“… 94 The sensing principle was designed by the fluorescence-quenching mechanism of SNP-RB and a wide linear E. coli concentration range of 10–10 5 CFU/mL could be obtained with a LOD of 8 CFU/mL. 94 In practice, the preparation of SNP-RB was carried out by employing co-condensation of RB into silica matrix and no structural changes of SNP was presented to compare with/without RB incorporation, and the obtained results were only concluded as to be sufficient enough to meet the demanded sensitivity and selectivity for E. coli . However, it could be beneficial to investigate the dispersibility of SNP from the point of quenching aspects since the aggregation‐caused quenching (ACQ) and leakage of dyes at high loading of fluorophores are important challenges of such designs.…”

“…This could be used to recognize the significant signal changes after the attachment of the analyte through the bio-recognition entities accommodated into the pores of silica NP. 94 …”