Carboxyl of Poly(D,L-lactide-co-glycolide) Nanoparticles of Perfluorooctyl Bromide for Ultrasonic Imaging of Tumor

Abstract

Perfluorooctyl bromide (PFOB) enclosed nanoparticles (NPs) as ultrasonic contrasts have shown promising results in the recent years. However, NPs display poor contrast enhancement in vivo. In this work, we used the copolymers poly(lactide-co-glycolide) carboxylic acid (PLGA-COOH) and poly(lactide-co- glycolide) poly(ethylene glycol) carboxylic acid (PLGA-PEG-COOH) as a shell to encapsulate PFOB to prepare a nanoultrasonic contrast agent. The NPs were small and uniform (210.6 ± 2.9 nm with a polydispersity index of 0.129 ± 0.016) with a complete shell nuclear structure under the transmission electron microscopy (TEM). In vitro, when concentration of NPs was ≥10 mg/ml and clinical diagnostic frequency was ≥9 MHz, NPs produced intensive enhancement of ultrasonic gray-scale signals. NPs could produce stable and obvious gray enhancement with high mechanical index (MI) (MI > 0.6). In vivo, the NPs offered good ultrasound enhancement in tumor after more than 24 h and optical imaging also indicated that NPs were mainly located at tumor site. Subsequent analysis confirmed that large accumulation of fluorescence was observed in the frozen section of the tumor tissue. All these results caused the conclusion that NPs encapsulated PFOB has achieved tumor-selective imaging in vivo.

Exploring and Analyzing the Systemic Delivery Barriers for Nanoparticles

“…Although the MPS and RES are relevant for nanoparticle clearance and sequestration, the literature references these terms inconsistently. [18][19][20][21][22][23] Chronologically, the term "RES" was first used in 1924 to describe any cell that accumulated systemically administered vital stains (i.e., dyes that stain living tissues), which were thought to be endothelial cells. [24] The term "MPS" was introduced in 1972 as a replacement when it was discovered that many of the cells involved in clearing macromolecules and foreign particulates from the blood were monocytes or originated from bone marrow.…”

Fundamentals and applications of nanoparticles for ultrasound‐based imaging and therapy

“…Moreover, NPs made up of liquid PFOB and PLGA‐COOH or PLGA‐PEG‐COOH could offer good tumor‐selective US enhancement. [ 118 ] Perfluoropropane (C 3 F 8 )‐filled PLGA NPs have been reported to increase the US contrast imaging ability by enhancing the signal intensity as the US contrast imaging agent based on ex vivo and in vivo studies. [ 119 ] PFP/PLGA‐PEG‐folic acid NPs have been designed for targeted US imaging by phase shift induced by low‐intensity focused US irradiation.…”