Fluorescent polymer as a biosensing tool for the diagnosis of microbial pathogens

Abstract

Diseases and diagnoses are predominant in the human population. Early diagnosis of etiological agents plays a vital role in the treatment of bacterial infections. Existing standard diagnostic platforms are laborious, time-consuming, and require trained personnel and cost-effective procedure, though they are producing promising results. These shortcomings have led to a thirst for rapid diagnostic procedures. Fluorescence-based diagnosis is one of the efficient rapid diagnostic methods that rely on specific and sensitive bacterial detection. Emerging bio-sensing studies on conducting polymers (CPs) are gaining popularity in medical diagnostics due to their promising properties of high fluorescence efficiency, good light stability, and low cytotoxicity. Poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), is the first identified soluble polymer and model material for understanding the fundamental photophysics of conventional CPs. In this present study, MEH-PPV is used as a fluorescent dye for direct pathogen detection applications by interacting with the microbial cell surface. An optimized concentration of MEH-PPV solution used to confirm the presence of selective bacterial structures. The present study endeavours towards bacterial detection based on the emission from bacteria due to interfacial interaction between polymer and bacterial surface.

Figure 1

FTIR Spectrum of PMP, MEHB, MEHDBMB, and MEH-PPV.

Figure 2

UV–vis and PL spectrum of MEH-PPV in toluene.

Figure 3

(a) Shows the growth of E. coli after incubating with solutions of MEH-PPV dissolved in THF, chloroform, toluene, and xylene respectively. The arrow on the digital image shows the direction of inoculum added on the culture plate. (b) Shows the control (without MEH-PPV solution) growth with respect to the same time interval of inoculation of test plate.

Figure 4

Microscopic image (a–d) shows the control and luminescence from E. coli exposed to different concentration of MEH-PPV solution respectively.

Figure 5

PL spectra of MEH-PPV with (solid line) and without (dashed line) E. coli.

Figure 6

Microscopic image (×100) shows the fluorescence from live E. coli cells (under UV exposure) and stains from dead E. coli cells stained with 3 mg mL⁻¹ MEH-PPV solution + 0.5% PVA.

Figure 7

Light microscopic images of unstained (1a–3a), Gram’s stain (1b–3b), Acridine Orange (1c–3c), Rhodamine 6G (1d–3d), and MEH-PPV (1e–3e) stained E. coli (1a–1e), S. aureus (2a–2e), and C. albicans (3a–3e).