Effects of hydrophilic/hydrophobic blocks ratio of PEG-b-PLGA on emission intensity and stability of over-1000 nm near-infrared (NIR-II) fluorescence dye-loaded polymeric micellar nanoparticles

Abstract

Polymeric micellar nanoparticles (PNPs) composed of the amphiphilic block copolymer formed from hydrophilic and hydrophobic blocks and over-thousand-nanometer (OTN) near-infrared (NIR) fluorescent dye are promising fluorophores for dynamic imaging of deep tissue. In this study, we examined the effect of the ratio of hydrophilic/hydrophobic blocks of a block copolymer, poly(ethylene glycol) (PEG)-b-poly(lactide-co-glycolide) (PLGA), on the properties of OTN-PNPs encapsulating IR-1061. OTN-PNPs with a higher molecular weight of PLGA cores showed higher emission and stabilities in physiological conditions. High PEG ratio to PLGA in block copolymer decreased the stability of OTN-PNPs probably due to the invasion of water molecules into the polymer core. The results show that the in vivo stability and fluorescence properties can be tuned by adjusting the chain lengths of block copolymers and estimated using in vitro assays, which evaluates the brightness retention rate of the OTN-PNPs under physiological conditions.

Effect of the enantiomeric structure of hydrophobic polymers on the encapsulation properties of a second near infrared (NIR-II) fluorescent dye for in vivo deep imaging

“…PEG- b -PLLA and PEG- b -PDLLA co-polymers with the same chain lengths (molecular weights; PEG Mw: 2000, PLA Mw: 5000) were used to avoid the potential bias effects of the polymer molecular weights on the encapsulation properties of IR-1061 shown in previous investigations. 33 The stability of IR-1061 in micelles was determined by comparing absorption ( Fig. 3 and 4 ), OTN-NIR fluorescence ( Fig.…”

“…5 Currently, there is a wide variety of OTN-NIR uorescent probes 6 including quantum dots, [7][8][9][10] single-walled carbon nanotubes, [11][12][13][14][15][16][17][18][19][20] lanthanide-doped ceramic nanoparticles, 3,[21][22][23] and organic molecular dyes. [24][25][26][27][28][29][30][31][32][33][34] Compared to inorganic nanoparticles, organic molecular dyes show great potential as probes with low toxicity and low bioaccumulation. 25 IR-1061, a widely used OTN-NIR uorescent dye, has hydrophobic and cationic (polarized) backbones in its molecular structure and a nonpolar counter ion, BF 4 À , that can suppress vibration quenching.…”

Controlling Molecular Dye Encapsulation in the Hydrophobic Core of Core–Shell Nanoparticles for In Vivo Imaging

“…For IR-1061-encapsulated micelles with shells composed of PEG, a biocompatible hydrophilic polymer, the effect of the molecular weight of a PLGA core polymer, which has a high affinity for the dye, was investigated [110]. In this study, the fluorescence performances of micellar nanoparticles encapsulating IR-1061 in PEG-b-PLGA with PLGA molecular weights of 1000, 2000, and 5000, and a PEG molecular weight of 2000 were compared.…”

“…Within this range of PLGA molecular weights (i.e., 1000-5000), the higher the molecular weight of the PLGA core, the higher the dye encapsulation efficiency and fluorescence intensity. Their absorption spectra showed that IR-1061 encapsulated in high-molecular-weight PLGA core was less affected by water molecules with a large phonon energy of polar vibration of hydroxyl bonding [53] in the dispersant [110]. The IR-1061-encapsulated PEG-b-PLGA micelles were highly stable in both in vitro (PBS containing albumin) and in vivo (in the circulating blood of mice) environments, as evidenced by the increase in the molecular weight of PLGA constituting the micelle core [110].…”

“…Their absorption spectra showed that IR-1061 encapsulated in high-molecular-weight PLGA core was less affected by water molecules with a large phonon energy of polar vibration of hydroxyl bonding [53] in the dispersant [110]. The IR-1061-encapsulated PEG-b-PLGA micelles were highly stable in both in vitro (PBS containing albumin) and in vivo (in the circulating blood of mice) environments, as evidenced by the increase in the molecular weight of PLGA constituting the micelle core [110]. Their time-dependent decrease in fluorescence intensity in these physiological environments was attributed to micelle deformation by proteins and salts, suggesting that the molecular weight of the hydrophobic polymer core is involved in the robustness of micelles encapsulating the polymethine dye IR-1061.…”