NONINVASIVE OPTICAL IMAGING OF STAPHYLOCOCCUS AUREUS INFECTION IN VIVO USING AN ANTIMICROBIAL PEPTIDE FRAGMENT BASED NEAR-INFRARED FLUORESCENT PROBES

Yueqing Gu,Cuicui Liu

doi:10.1142/s1793545813500260

Abstract

The diagnosis of bacterial infections remains a major challenge in medicine. Optical imaging of bacterial infection in living animals is usually conducted with genetic reporters such as light-emitting enzymes or fluorescent proteins. However, there are many circumstances where genetic reporters are not applicable, and there is an urgent need for exogenous synthetic probes that can selectively target bacteria. Optical imaging of bacteria in vivo is much less developed than methods such as radioimaging and MRI. Furthermore near-infrared (NIR) dyes with emission wavelengths in the region of 650–900 nm can propagate through two or more centimeters of tissue and may enable deeper tissue imaging if sensitive detection techniques are employed. Here we constructed an antimicrobial peptide fragment UBI29-41-based near-infrared fluorescent imaging probe. The probe is composed of UBI29-41 conjugated to a near infrared dye ICG-Der-02. UBI29-41 is a cationic antimicrobial peptide that targets the anionic surfaces of bacterial cells. The probe allows detection of Staphylococcus aureus infection (5 × 107 cells) in a mouse local infection model using whole animal near-infrared fluorescence imaging. Furthermore, we demonstrate that the UBI29-41-based imaging probe can selectively accumulate within bacteria. The significantly higher accumulation in bacterial infection suggests that UBI29-41-based imaging probe may be a promising imaging agent to detect bacterial infections.

Highlights

It has been reported that almost 85% of critically ill patients in hospitals have fever but show no apparent signs of infection.[1]
Radiological (X-ray computed tomography) and magnetic resonance imaging (MRI) techniques are often not suitable for the early detection of infection because such techniques are focused on specic body parts and provide information only if morphological changes have occurred in the applied areas
The crude product UBI29-41-ICG02 wasrst conrmed by thin layer chromatography (TLC) and subsequently puried byltration over Sephadex G-15

Summary

Introduction

It has been reported that almost 85% of critically ill patients in hospitals have fever but show no apparent signs of infection.[1]. Staphylococcus aureus (S. aureus) is among the most pathogenic bacteria causing a wide spectrum of diseases ranging from minor wound infections to life-threatening infections such as endocarditis, septicemia, pneumonia and toxic shock syndrome.[2] Radiological (X-ray computed tomography) and magnetic resonance imaging (MRI) techniques are often not suitable for the early detection of infection because such techniques are focused on specic body parts and provide information only if morphological changes have occurred in the applied areas. In the case of bacterial targeting, previously reported a±nity ligands include antibodies,[3] sugars,[4] bacterial binding peptides,[5] enzyme substrates.[6] Antibodies are popular, since they can bind tightly to specic molecular targets on the surfaces of both Gram-positive and Gram-negative bacterial cells. While antibodies have the potential advantage of high specicity, their large molecular size ($ 150 kD) is a limitation for in vivo imaging because of slow tissue di®usion and blood clearance rate.[7]

Methods

Results

Conclusion