Improved tumor contrast achieved by single time point dual-reporter fluorescence imaging

Abstract

Abstract. In this study, we demonstrate a method to quantify biomarker expression that uses an exogenous dualreporter imaging approach to improve tumor signal detection. The uptake of two fluorophores, one nonspecific and one targeted to the epidermal growth factor receptor (EGFR), were imaged at 1 h in three types of xenograft tumors spanning a range of EGFR expression levels (n ¼ 6 in each group). Using this dual-reporter imaging methodology, tumor contrast-to-noise ratio was amplified by >6 times at 1 h postinjection and >2 times at 24 h. Furthermore, by as early as 20 min postinjection, the dual-reporter imaging signal in the tumor correlated significantly with a validated marker of receptor density (P < 0.05, r ¼ 0.93). Dual-reporter imaging can improve sensitivity and specificity over conventional fluorescence imaging in applications such as fluorescence-guided surgery and directly approximates the receptor status of the tumor, a measure that could be used to inform choices of biological therapies.

Comprehensive spectral endoscopy of topically applied SERS nanoparticles in the rat esophagus

“…For example, normal tissues can exhibit stronger signals than tumors due to higher retention of contrast agent, i.e. inverse contrast [31,32], while in some other cases, tumors exhibit stronger signals than normal tissues due to EPR [33][34][35]. In addition, contrast agents are seldom distributed evenly when administered via systemic or topical application (Figs.…”

“…3(e), 3(g), 4(e), 4(f) and 5(c)). To eliminate these sources of image ambiguity, various groups are utilizing and witnessing the power of a dual-reporter ratiometric detection strategy, in which one negative reporter serves as a control to assess the behavior of a simultaneously delivered positive reporter for accurate identification and quantification of molecularly specific binding [23,31,32,34]. SERS NPs are ideal reporters for such ratiometric strategies since they are excited at a single illumination wavelength (785 nm), ensuring that all NP reporters in a single measurement are interrogated identically in terms of illumination intensity, detection area, and effective excitation depth.…”

“…For example, normal tissues can generate stronger signals than tumors due to higher nonspecific retention of contrast agents, i.e. inverse contrast [31,32]. On the other hand, the opposite effect -enhanced penetration and retention (EPR) in tumors versus normal tissues -is also often observed [33][34][35].…”

“…On the other hand, the opposite effect -enhanced penetration and retention (EPR) in tumors versus normal tissues -is also often observed [33][34][35]. Regardless of the functional mechanisms for the accumulation of contrast agents in tissues, there is increasing agreement that utilizing a dual-reporter ratiometric detection strategy, in which one negative reporter serves as a control for a simultaneously delivered positive probe, is valuable to accurately identify and quantify molecularly specific binding [23,31,32,34]. SERS NPs are particularly suited for this ratiometric strategy, not only due to their excellent multiplexing capability but also due to the fact that they can be excited at a single illumination wavelength, ensuring that all NP flavors in a single measurement are interrogated identically in terms of illumination intensity, spot size and effective excitation depth.…”

Tomography of epidermal growth factor receptor binding to fluorescent Affibodyin vivostudied with magnetic resonance guided fluorescence recovery in varying orthotopic glioma sizes

“…Recently, a novel dual-tracer technique was introduced to overcome the problem of nonspecific uptake in molecular imaging and, thus, enable quantitative estimation of receptor concentration in vivo. [1][2][3] In this approach, two tracers are imaged simultaneously, one targeted to the receptor of interest and the other a nontargeted reference tracer. Comparing the uptake of these dyes enables recovery of binding potential, BP, a quantitative parameter proportional to the concentration of receptors available for binding.…”