Abstract
Owing to a higher demand for glucosamine (GlcN) in metabolic processes in tumor cells than in normal cells (i.e., GlcN effects), tumor imaging in magnetic resonance imaging (MRI) can be highly improved using GlcN-conjugated MRI contrast agents. Here, GlcN was conjugated with polyacrylic acid (PAA)-coated ultrasmall gadolinium oxide nanoparticles (UGONs) (davg = 1.76 nm). Higher positive (brighter or T1) contrast enhancements at various organs including tumor site were observed in human brain glioma (U87MG) tumor-bearing mice after the intravenous injection of GlcN-PAA-UGONs into their tail veins, compared with those obtained with PAA-UGONs as control, which were rapidly excreted through the bladder. Importantly, the contrast enhancements of the GlcN-PAA-UGONs with respect to those of the PAA-UGONs were the highest in the tumor site owing to GlcN effects. These results demonstrated that GlcN-PAA-UGONs can serve as excellent T1 MRI contrast agents in tumor imaging via GlcN effects.
Highlights
The average particle diameter was estimated to be 1.76 nm for the polyacrylic acid (PAA)-ultrasmall gadolinium oxide nanoparticles (UGONs) and GlcNPAA-UGONs from log-normal function fits to the observed particle diameter distributions (Figure 1c,d and Table 1)
The r1 and r2 values of the GlcN-PAA-UGONs were slightly lower than those of the PAA-UGONs (Table 3). This was probably because the PAA with many –COOH groups attracted a larger number of water molecules around the UGONs than GlcN with –OH
The first case allows the GlcN-PAA-UGONs to interact with a fewer number of water proton spins than the PAA-UGONs, and the second case allows the GlcN-PAAUGONs to less strongly interact with water proton spins than the PAA-UGONs, resulting in lower r1 and r2 values in the GlcN-PAA-UGONs
Summary
Higher positive (brighter or T1 ) contrast enhancements at various organs including tumor site were observed in human brain glioma (U87MG) tumor-bearing mice after the intravenous injection of. GlcN-PAA-UGONs with respect to those of the PAA-UGONs were the highest in the tumor site owing to GlcN effects. These results demonstrated that GlcN-PAA-UGONs can serve as excellent T1. Magnetic resonance imaging (MRI), a noninvasive imaging technique in which radiofrequency proton spin signals are processed, has been widely applied in tumor diagnosis because of its high anatomical resolution and sensitivity due to the ample existence of protons in the body [3,4]
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