Abstract
Black porous silicon nanoparticles (BPSi NPs) are known as highly efficient infrared light absorbers that are well-suitable for photothermal therapy (PTT) and photoacoustic imaging (PAI). PTT and PAI require a sufficient number of effectively light-absorbing NPs to be accumulated in tumor after intravenous administration. Herein, biodistribution of PEGylated BPSi NPs with different sizes (i.e., 140, 200, and 300 nm in diameter) is investigated after intravenous administration in mice. BPSi NPs were conjugated with fluorescent dyes Cy5.5 and Cy7.5 to track them in vitro and in vivo, respectively. Optical imaging with an in vivo imaging system (IVIS) was found to be an inadequate technique to assess the biodistribution of the dye-labeled BPSi NPs in vivo because the intrinsic strong absorbance of the BPSi NPs interfered fluorescence detection. This challenge was resolved via the use of inductively coupled plasma optical emission spectrometry to analyze ex vivo the silicon content in different tissues and tumors. The results indicated that most of the polyethylene glycol-coated BPSi NPs were found to accumulate in the liver and spleen after intravenous injection. The smallest 140 nm particles accumulated the most in tumors at an amount of 9.5 ± 3.4% of the injected dose (concentration of 0.18 ± 0.08 mg/mL), the amount known to produce sufficient heat for cancer PTT. Furthermore, the findings from the present study also suggest that techniques other than optical imaging should be considered to study the organ biodistribution of NPs with strong light absorbance properties.
Highlights
An efficient and safe cancer treatment with nanomedicines should ideally exhibit preferential tumor accumulation, lowering the administration dose and reducing side effects in healthy organs at the same time.[1]
Effective accumulation in tumors is important for the treatment modalities that rely on external triggers, such as magnetic hyperthermia[2] and hyperthermia induced by radiofrequency radiation,[3−5] ultrasound,[6,7] or light [photothermal therapy (PTT)]
We have previously demonstrated the feasibility of Black porous silicon (BPSi) NPs for cancer PTT following intratumoral injection.[24]
Summary
An efficient and safe cancer treatment with nanomedicines should ideally exhibit preferential tumor accumulation, lowering the administration dose and reducing side effects in healthy organs at the same time.[1]. The effects of the different particle sizes (i.e., 140, 200, and 300 nm in diameter) and surface modifications of BPSi NPs on their cellular uptake and biocompatibility were investigated in vitro We further studied their organ biodistribution and passive tumor targeting (syngeneic CT26 tumor model) in vivo qualitatively with optical imaging and quantitatively with inductively coupled plasma-optical emission mass spectrometry (ICP-OES MS) analysis after intravenous injection. Cell viability experiments were used to study cytotoxicity of CT26 cancer cells exposed to BPSi NPs with different particle sizes and surface coatings. Cy5.5, and PEG-BPSi-Cy5.5) and sizes (140, 200, and 300 nm) were washed with deionized H2O and dispersed in cell culture medium at four different concentrations (0.05, 0.1, 0.2, and 0.5 mg/ mL).
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