Design of Over-1000 nm Near-Infrared Fluorescent Polymeric Micellar Nanoparticles by Matching the Solubility Parameter of the Core Polymer and Dye

Polymericmicellarnanoparticles (PNPs) encapsulating over-thousand-nanometer(OTN) near-infrared (NIR) fluorescent dye molecules in block polymershaving hydrophobic and hydrophilic chains are promising agents forthe dynamic imaging of deep tissue. To achieve OTN-NIR fluorescentPNPs (OTN-PNPs) having high brightness, it is crucial to increasethe affinity between the core polymer and dye molecules by matchingtheir polarities; thus, criteria and methods to evaluate the affinityare required. In this study, we used the Hansen solubility parameter(HSP), including the polarity term, to evaluate the affinity betweenthe two substances. HSP values of the OTN-NIR fluorescent dye IR-1061and four core polymers, poly-(lactic-co-glycolic acid)(PLGA), poly-(lactic acid) (PLA), poly-(& epsilon;-caprolactone) (PCL),and polystyrene (PSt), were calculated using the Hansen solubilitysphere method and molecular group contribution method, respectively.The relative energy density between IR-1061 and each core polymercalculated using their HSP values revealed that the affinities ofPLGA and PLA for IR-1061 are higher than those of PCL and PSt. Therefore,OTN-PNPs composed of PLGA, PLA, and PCL core polymers were preparedand compared. The OTN-PNPs having PLGA and PLA cores could be loadedwith larger amounts of IR-1061, had higher photoluminescence intensities,and showed higher stability in phosphate buffered saline than thosehaving PCL cores. Moreover, the OTN-PNPs having PLGA or PLA coreswere used for the dynamic imaging of live mice. Thus, matching thesolubility parameters of the core polymer and dye molecule is a usefulapproach for designing high-performance OTN-NIR fluorescent probes.

Automated summary

This study evaluated the affinity between the OTN-NIR fluorescent dye IR-1061 and four core polymers using Hansen solubility parameters, and compared the performance of OTN-PNPs. The results showed that PLGA and PLA had higher affinity for IR-1061 compared to PCL and PSt, resulting in OTN-PNPs with PLGA and PLA cores exhibiting superior characteristics in terms of loading capacity, fluorescence intensity, and stability.