In vivo evaluation of safety of nanoporous silicon carriers following single and multiple dose intravenous administrations in mice

Abstract

Porous silicon (pSi) is being extensively studied as an emerging material for use in biomedical applications, including drug delivery, based on the biodegradability and versatile chemical and biophysical properties. We have recently introduced multistage nanoporous silicon microparticles (S1MP) designed as a cargo for nanocarrier drug delivery to enable the loaded therapeutics and diagnostics to sequentially overcome the biological barriers in order to reach their target. In this first report on biocompatibility of intravenously administered pSi structures, we examined the tolerability of negatively (-32.5±3.1mV) and positively (8.7±2.5mV) charged S1MP in acute single dose (10(7), 10(8), 5×10(8) S1MP/animal) and subchronic multiple dose (10(8) S1MP/animal/week for 4 weeks) administration schedules. Our data demonstrate that S1MP did not change plasma levels of renal (BUN and creatinine) and hepatic (LDH) biomarkers as well as 23 plasma cytokines. LDH plasma levels of 145.2±23.6, 115.4±29.1 vs. 127.0±10.4; and 155.8±38.4, 135.5±52.3 vs. 178.4±74.6 were detected in mice treated with 10(8) negatively charged S1MP, 10(8) positively charged S1MP vs. saline control in single and multiple dose schedules, respectively. The S1MPs did not alter LDH levels in liver and spleen, nor lead to infiltration of leukocytes into the liver, spleen, kidney, lung, brain, heart, and thyroid. Collectively, these data provide evidence of a safe intravenous administration of S1MPs as a drug delivery carrier.

Figure 1

Scanning Electron Micrographs of hemispherical shaped nanoporous silicon S1MPs used in this study. Low magnification image (5K), showing a uniform size and shape distribution of microfabricated nanocarriers (upper image); and high magnification image (20K) presenting the porous structure of the S1MP where the S2NP can be loaded (lower image).

Figure 2

S1MP tissue accumulation. The liver and spleen were harvested from the mice injected with S1MP (10⁸ in saline) via tail vein and fixed with formalin. Five micron paraffin sections were stained with H&E to identify the localization of S1MP. The red circles and zoom-in areas indicate the S1MP accumulation in the liver and spleen (final magnification = × 400, bar 20μm).

Figure 3

LDH levels in spleen and liver following single (left column) or multiple dose (four weekly doses, right column) i.v. administration of various pSi S1MP nanovectors. Various doses of negatively (oxidized) and positively (APTES) charged pSi particles were injected and saline and silicic acid were used as controls. The results are presented as mean ± S.D.

Figure 4

Plasma cytokine levels 24 hours following single dose i.v. administration of various pSi S1MP nanovectors. The treatments included saline, silicic acid equivalent to the 5×10⁸ of the particles injected, negatively (oxidized) and positively (APTES) charged S1MP particles at the doses of 10⁷, 10⁸ and 5×10⁸ particles per mouse. The results are presented as mean ± S.D (n=4–6)

Figure 5

Plasma cytokine levels following multiple dose (four weekly doses) i.v. administration of various pSi S1MP nanovectors. The animals were sacrificed on the 5^th week from the first injection. The treatments included saline, silicic acid equivalent to the 10⁸ of the S1MP particles injected, negatively (oxidized) and positively (APTES) charged particles at the dose of 10⁸ particles per mouse (n=4–6).