By changing the ratio of acrylic acid to styrene, the loading amount of fluorescent dye can be increased and the optical properties of the resulting bioimaging probe can be improved.
Polymeric
micellar
nanoparticles (PNPs) encapsulating over-thousand-nanometer
(OTN) near-infrared (NIR) fluorescent dye molecules in block polymers
having hydrophobic and hydrophilic chains are promising agents for
the dynamic imaging of deep tissue. To achieve OTN-NIR fluorescent
PNPs (OTN-PNPs) having high brightness, it is crucial to increase
the affinity between the core polymer and dye molecules by matching
their polarities; thus, criteria and methods to evaluate the affinity
are required. In this study, we used the Hansen solubility parameter
(HSP), including the polarity term, to evaluate the affinity between
the two substances. HSP values of the OTN-NIR fluorescent dye IR-1061
and four core polymers, poly(lactic-co-glycolic acid)
(PLGA), poly(lactic acid) (PLA), poly(ε-caprolactone) (PCL),
and polystyrene (PSt), were calculated using the Hansen solubility
sphere method and molecular group contribution method, respectively.
The relative energy density between IR-1061 and each core polymer
calculated using their HSP values revealed that the affinities of
PLGA 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 prepared
and compared. The OTN-PNPs having PLGA and PLA cores could be loaded
with larger amounts of IR-1061, had higher photoluminescence intensities,
and showed higher stability in phosphate buffered saline than those
having PCL cores. Moreover, the OTN-PNPs having PLGA or PLA cores
were used for the dynamic imaging of live mice. Thus, matching the
solubility parameters of the core polymer and dye molecule is a useful
approach for designing high-performance OTN-NIR fluorescent probes.
Fluorescence imaging in the over-thousand nanometer (OTN-) near-infrared (NIR) wavelength region is an emerging technique for real-time bioimaging. OTN-NIR probes are made from micellar nanoparticles encapsulating IR-1061 dye in the core of poly(ethylene glycol) (PEG) phospholipid (PL), such as 1, 2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE)-N-[methoxy PEG] micelles. The property investigation revealed that the probe is less stable in albumin and PBS while remaining unchanged in water and saline. The results are critical for applying OTN-NIR probe from DSPE-PEG micelles in physiological environments.
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