Real‐Time Noninvasive Monitoring of In Vivo Inflammatory Responses using a pH Ratiometric Fluorescence Imaging Probe

Abstract

It is often difficult to continuously monitor and quantify inflammatory responses in vivo. These dynamic responses however are often accompanied by specific pH changes. A new ratiometric optical pH probe is developed by combining pH-sensitive (CypHer5E) and pH-insensitive (Oyster800) fluorescent dyes into nanoparticles for in vivo optical imaging. By taking the ratio of fluorescence intensities at different wavelengths, these nanosized sensors provide excellent measurement capabilities, and unique mapping, of the continuous in vivo pH changes for three different inflammation models. In each model a strong positive correlation is found between ratiometric pH changes and the corresponding inflammatory response measured by histological analyses. These results indicate that ratiometric imaging can provide a noninvasive, rapid, and highly sensitive optical readout for the pH-ratio changes in vivo. Furthermore this technique may be used to monitor the real-time dynamics of inflammatory processes.

Non-invasive Characterization of Immune Responses to Biomedical Implants

“…3c and 3d). 99 These results support that pH imaging probes can be used to assess the potential impact (inflammatory responses and toxicity) of biomaterial implants on the surrounding tissues. Furthermore, pH ratiometric imaging probes can also be used to assess the microenvironment and health of transplanted cells in scaffolds for tissue engineering application.…”

“…The ability of the pH ratiometric probes for in vivo determination of degree of acidosis was then tested in ischemic kidney injury, tumorigenesis and foreign body reaction models. 99 Indeed, we found that there was a very good relationship between tissue acidosis (pH values 7.4) and inflammatory cell accumulation (based on histological analyses) (Figs. 3c and 3d).…”

“…To overcome these limitations, an pH ratiometric imaging probe has recently been developed by chemically conjugating a pH-sensitive dye (CypHer5E dye) and a pHinsensitive dye (Oyster Ò -800) onto a biocompatible PNIPAM nanoparticle which is used as a carrier. 99 The ability of ratiometric probes to quantitate pH changes was evaluated both in vitro and in vivo. Using in vitro system, we first determined that the ratio of the average fluorescence intensities between CypHer5E and Oyster Ò -800 had a strong linear correlation with pH values from 5.53 to 7.55.…”

“…Abbreviations for particles made of different materials-PEG (polyethylene glycol); PLA (poly-L-lactic acid); PNIPAM-NH 2 (amine-rich poly-N-isopropylacrylamide-co-N-(3-aminopropyl) methacryl-amide); PS (polystyrene); SiO 2 (silicone dioxide). Adapted from Tsai et al99 …”

Ratiometric Reactive Oxygen Species Nanoprobe for Noninvasive <I>In Vivo</I> Imaging of Subcutaneous Inflammation/Infection

“…27 250 µl of solution containing H 2 O 2 (6.0 mM) and IR750-NP-L012 probes (0.4mg/ml) were added into each well, and then these phantoms were placed between the solution and the emission light pathways during image collection. Using a Kodak In Vivo FX Pro System (Kodak, USA) (f/stop, 2.5; 4×4 binning), the chemiluminescence intensities were collected with an exposure time of 5 min, and the fluorescence intensities were recorded with an exposure time of 30 sec (excitation at 760 nm, emission at 830 nm).…”