Smart Nanoparticles as Near-Infrared
Fluorescent Biomarkers
Vishal Saxena, Drug Delivery &
Biotechnology Laboratory, College of Pharmacy and Allied Health
Professions
Mostafa Sadoqi, Department of Physics,
St. John’s College of Liberal Arts and Sciences
Jun Shao, Department of Pharmacy and
Administrative Sciences, College of Pharmacy and Allied Health
Professions
Abstract
Purpose: The objective of this
study is to develop a stable, biodegradable, biocompatible,
nontoxic and targetable near-infrared nanobiomarker.
Poly(dl-lactic-co-glycolic acid) (PLGA) nanoparticles were
engineered by entrapping near-infrared fluorescent dye Indocyanine
green (ICG) and the overall stability provided to ICG by the
nanoparticle delivery system in aqueous media was established.
Methods: PLGA nanoparticles
entrapping ICG were prepared by a modified spontaneous
emulsification solvent diffusion method. The ICG entrapment in
nanoparticles was determined and physicochemical characterization
of nanoparticles was performed. The degradation kinetics of ICG was
investigated in aqueous solution and aqueous nanoparticles
suspension by steady-state fluorescence technique and order of
degradation was determined. The influence of ICG entrapment in
nanoparticles on fluorescence spectra of ICG and on degradation of
ICG in aqueous media, photodegradation and thermal degradation were
studied. PEG coating of the nanoparticles was performed to prolong
in-vivo circulation time thus providing passive tumor
targeting.
Results: PLGA nanoparticles with
mean diameter of 357 21 nm and ICG entrapment of about 74% were
obtained. The degradation of ICG in aqueous solution and in aqueous
nanoparticles suspension follows first order kinetics for the time
period studied. The entrapment of ICG in nanoparticles causes a
shift in its wavelength of peak fluorescence and decrease in its
peak fluorescence intensity. The entrapment in nanoparticles
provides high stability to ICG degradation in aqueous medium along
with efficient photostability and thermal stability to ICG. An
efficient PEG coating of the nanoparticle surface was obtained.
Conclusions: This investigation
shows that the degradation of ICG in aqueous media follows first
order kinetics. The nanoparticles formulation provides overall
stability to degradation of ICG in aqueous media and thus emerges
as an efficient near-infrared fluorescent nanobiomarker system
having a tumor targeting ability.