Search

Nanosize structures activated by near-infrared (NIR) photoexcitation can provide an optical platform for the image-guided removal of small tumor nodules. We have engineered nanoparticles derived from erythrocytes that can be doped with NIR fluorophore indocyanine green (ICG). We refer to these constructs as NIR erythrocyte-derived transducers (NETs). The objective of this study was to determine if ICG-bound albumin (IbA), as the doping material, could enhance the fluorescence emission of NETs, and evaluate the capability of these nanoprobes in imaging cancer cells. Erythrocytes were isolated from bovine whole blood and depleted of hemoglobin to form erythrocyte ghosts (EGs). EGs were then extruded through nanosize porous membranes in the presence of 10-100 μm ICG or Iba (1:1 molar ratio) to form ICG- or IbA-doped NETs. The resulting nanosize constructs were characterized for their diameters, zeta-potentials, absorption, and fluorescence emission spectra. We used fluorescence microscopic imaging to evaluate the capability of the constructs in imaging SKOV3 ovarian cancer cells. Based on dynamic light-scattering measurements, ICG- and IbA-doped NETs had similar diameter distributions (Z-average diameter of 236 and 238 nm, respectively) in phosphate-buffered saline supplemented with 10% fetal bovine serum, which remained nearly constant over the course of 2 h at 37 °C. Despite a much-lower loading efficiency of IbA (∼0.7-8%) as compared to ICG (10-45%), the integrated normalized fluorescence emission of IbA-NETs was 2- to 6-fold higher than ICG-doped NETs. IbA-NETs also demonstrated an enhanced capability in fluorescence imaging of SKOV3 ovarian cancer cells, and can serve as potentially effective nanoprobes for the fluorescence imaging of cancerous cells.

Particle-based systems provide a capability for the delivery of imaging and/or therapeutic payloads. We have engineered constructs derived from erythrocytes, and doped with the FDA-approved near infrared dye, indocyanine green (ICG). We refer to these optical particles as NIR erythrocyte-mimicking transducers (NETs). A particular feature of NETs is that their diameters can be tuned from micron- to nano-scale. Herein, we investigated the effects of micron- (≈2.6 μm diameter), and nano- (≈145 nm diameter) sized NETs on their biodistribution, and evaluated their acute toxicity in healthy Swiss Webster mice. Following tail vein injection of free ICG and NETs, animals were euthanized at various time points up to 48 hours. Fluorescence analysis of blood showed that nearly 11% of the injected amount of nano-sized NETs (nNETs) remained in blood at 48 hours post-injection as compared to ≈5% for micron-sized NETs (μNETs). Similarly, at this time point, higher levels of nNETs were present in various organs including the lungs, liver, and spleen. Histological analyses of various organs, extracted at 24 hours post-injection of NETs, did not show pathological alterations. Serum biochemistry profiles, in general, did not show elevated levels of the various analyzed biomarkers associated with liver and kidney functions. Values of various hematological profiles remained within the normal ranges following the administration of μNETs and nNETs. Results of this study suggest that erythrocyte-derived particles can potentially provide a non-toxic platform for delivery of ICG.