Development of a Compensated Förster Resonance Energy Transfer Imaging for Improved Assessment of the Intrapulmonary Distribution of Polymeric Nanoparticles.

Inhalation-based drug delivery systems have gained attention as potential therapeutic options for various respiratory diseases. Among these systems, nanoparticles are being explored as drug carriers because of their ability to deliver therapeutic agents directly to the lungs. It is essential to accurately evaluate the intrapulmonary behavior of nanoparticles to optimize drug delivery and achieve selective targeting of lung lesions. Prior research used the Förster resonance energy transfer (FRET) phenomenon to study the in vivo behavior of nanoparticles as drug carriers. In this study, image reconstruction involving bleed-through compensation was used to quantitatively assess the behavior of FRET nanoparticles in the lungs. When the nanoparticles for FRET fluorescence imaging, which employed 1,1'-dioctadecyl-3,3,3',3'-tetramethylindodicarbocyanine, 4-chlorobenzenesulfonate salt (DiD) as the donor and as 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine iodide (DiR) the acceptor, were administered to mouse lungs, whole-body in vivo imaging could not compensate for the influence of respiration and heartbeat. However, ex vivo imaging of excised lungs enabled the quantitative evaluation of the time-concentration profiles and distribution of nanoparticles within the lungs. This imaging technique is particularly useful for the development of inhalable nanoparticles that specifically target the lesions and exhibit controlled-release capabilities within the lungs.

Development of visualization and analysis methods for evaluating intratumoral nanoparticle kinetics for tumor-targeted drug delivery using Förster resonance energy transfer in vivo live imaging and tissue clearing techniques.

In this study, the imaging methods for evaluating the kinetics of nanoparticles as drug delivery systems in tumor tissues were improved in BxPC3 tumor-bearing mice. First, Förster resonance energy transfer (FRET) live imaging was selected to quantitatively evaluate nanoparticle kinetics in the tumor tissue of mice. Briefly, and 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine iodide (as an acceptor)-and 1,1'-dioctadecyl-3,3,3',3'-tetramethylindodicarbocyanine, 4-chlorobenzenesulfonate salt (as a donor)-coloaded nanoparticles were administered intravenously to the mice, and imaging was performed using a fluorescence in vivo imager. The fluorescence intensities of images were acquired in the FRET, donor, and acceptor channels, and the nanoparticle kinetics in the tumor region was quantified by compensating for bleed-through. Second, in the cleared tumor tissue of mice, the difference in evaluation properties between the two- and three-dimensional visualization of the nanoparticles was examined. In brief, 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI)-loaded nanoparticles were intravenously administered to the mice after fluorescently labeled tomato lectin treatment to visualize tumor vessels. Excised tumor tissue was cleared and observed using laser-scanning confocal microscopy, and three-dimensional images were reconstructed. The three-dimensional minimum distances traveled by DiI from the tumor vessels were calculated using information about the two-dimensional distance and the slicing position using the Pythagoras theorem. These imaging techniques should facilitate the development of drug delivery systems for cancer.

Evaluation of tissue-clearing techniques for intraorgan imaging of distribution of polymeric nanoparticles as drug carriers.

OBJECTIVE: The development of drug delivery systems using nanocarriers requires intraorgan imaging techniques for evaluating the distribution of nanocarriers. In this study, we evaluated the tissue-clearing techniques for the imaging of polymeric nanoparticles, a nanocarrier, in the liver used as a model of pigment-rich organ in mice. SIGNIFICANCE: The intraorgan imaging method of polymeric nanoparticles was examined without sectioning of organ samples for evaluating the delivery efficiency in preclinical studies. METHODS: DiI-loaded polymeric nanoparticles and fluorescence-tagged tomato lectin for fluorescence labeling of liver general structures were intravenously administered to mice. Tissue-clearing treatment of the mouse liver was performed using ClearT2, ScaleSQ(0), clearing agent comprising fructose, urea, and glycerol for imaging (FUnGI), clear unobstructed brain/body imaging cocktails and computational analysis (CUBIC), and modified CUBIC techniques. Intraorgan fluorescence imaging in the liver was performed by confocal laser microscopy. RESULTS: ClearT2 treatment exhibited insufficient clearing capability in the mouse liver. Although CUBIC treatment exhibited the best clearing capability, the CUBIC caused DiI leakage. ScaleSQ(0), FUnGI, and modified CUBIC treatments exhibited better clearing capability than ClearT2 technique while preserving the DiI. In the fluorescence imaging, the CUBIC and modified CUBIC exhibited deeper visualization than with the ScaleSQ(0) and FUnGI; however, the CUBIC led to a change in DiI distribution. The modified CUBIC enabled the deepest visualization while preserving the distribution of DiI. CONCLUSION: The intraorgan imaging method was established using modified CUBIC technique by the intravenous administration of fluorescence-tagged tomato lectin for evaluating the distribution of polymeric nanoparticles in mouse pigment-rich organs.

Multiscale Live Imaging Using Förster Resonance Energy Transfer (FRET) for Evaluating the Biological Behavior of Nanoparticles as Drug Carriers.

To develop targeted drug delivery systems using nanoparticles for treating various diseases, the evaluation of nanoparticle behavior in biological environments is necessary. In the present study, the biological behavior of polymeric nanoparticles was directly traced in living mice and cells. The dissociation of nanoparticles was detected by Förster resonance energy transfer (FRET) imaging. DiR and DiD were encapsulated in the nanoparticles for near-infrared FRET imaging, and they were traced using in vivo FRET imaging and intravital FRET imaging at the whole-body and tissue scales, respectively. In vivo FRET imaging revealed that the nanoparticles dissociated over time following intravenous administration. Intravital FRET imaging revealed that the nanoparticles dissociated in the liver and blood vessels following intravenous administration. DiI and DiO were encapsulated in nanoparticles for FRET imaging using confocal microscopy, and they were traced using in vitro FRET imaging in HepG2 cells. In vitro FRET imaging revealed that the nanoparticles dissociated and released fluorescent dyes that distributed in the cell membrane. Finally, live imaging was performed using FRET at the whole-body, tissue, and cellular scales. This method is suitable for obtaining information regarding the biological kinetic properties of nanoparticles and their use in targeted drug delivery.

Intratumoral delivery and therapeutic efficacy of nanoparticle-encapsulated anti-tumor siRNA following intrapulmonary administration for potential treatment of lung cancer.

This study evaluated the delivery efficiency and antitumor effects of the intrapulmonary administration of antitumor small interfering ribonucleic acid (siRNA)-containing nanoparticles to mice with metastatic lung tumor. Fluorescence-labeled, siRNA-containing nanoparticles were administered using Liquid MicroSprayer® to mice with metastatic lung tumors induced by the murine melanoma cell line B16F10. Fluorescent signals in the whole lung and in the tumor region following the intrapulmonary administration of siRNA-containing nanoparticles were stronger than those following intravenous administration. The intrapulmonary administration of nanoparticles containing a mixture of siRNA against MDM2, c-Myc, and vascular endothelial growth factor (VEGF) significantly improved survival and prolonged the survival of mice with metastatic lung tumor. In addition, after the intrapulmonary or intravenous administration of the mixture, the activity levels of interleukin-6 and -12, markers of systemic toxicity, were similar to those of nontreatment. These results indicate that the antitumor siRNA-containing nanoparticles were delivered efficiently and specifically to tumor cells, effectively silencing the oncogenes in the lung metastasis without any significant systemic toxicity.