Bioevaluation of magnetic mesoporous silica rods: cytotoxicity, cell uptake and biodistribution in zebrafish and rodents

Abstract

Cytotoxicity; Bioevaluation

Citotoxicidad; Bioevaluación

Citotoxicitat; Bioavaluació

Mesoporous silica nanoparticles (MSN) characterized by large surface area, pore volume, tunable chemistry, and biocompatibility have been widely studied in nanomedicine as imaging and therapeutic carriers. Most of these studies focused on spherical particles. In contrast, mesoporous silica rods (MSR) that are more challenging to prepare have been less investigated in terms of toxicity, cellular uptake, or biodistribution. Interestingly, previous studies showed that silica rods penetrate fibrous tissues or mucus layers more efficiently than their spherical counterparts. Recently, we reported the synthesis of MSR with distinct aspect ratios and validated their use in multiple imaging modalities by loading the pores with maghemite nanocrystals and functionalizing the silica surface with green and red fluorophores. Herein, based on an initial hypothesis of high liver accumulation of the MSR and a future vision that they could be used for early diagnosis or therapy in fibrotic liver diseases; the cytotoxicity and cellular uptake of MSR were assessed in zebrafish liver (ZFL) cells and the in vivo safety and biodistribution was investigated via fluorescence molecular imaging (FMI) and magnetic resonance imaging (MRI) employing zebrafish larvae and rodents. The selection of these animal models was prompted by the well-established fatty diet protocols inducing fibrotic liver in zebrafish or rodents that serve to investigate highly prevalent liver conditions such as non-alcoholic fatty liver disease (NAFLD). Our study demonstrated that magnetic MSR do not cause cytotoxicity in ZFL cells regardless of the rods' length and surface charge (for concentrations up to 50 μg ml-1, 6 h) and that MSR are taken up by the ZFL cells in large amounts despite their length of ∼1 μm. In zebrafish larvae, it was observed that they could be safely exposed to high MSR concentrations (up to 1 mg ml-1 for 96 h) and that the rods pass through the liver without causing toxicity. The high accumulation of MSR in rodents' livers at short post-injection times (20% of the administered dose) was confirmed by both FMI and MRI, highlighting the utility of the MSR for liver imaging by both techniques. Our results could open new avenues for the use of rod-shaped silica particles in the diagnosis of pathological liver conditions.

The authors acknowledge financial support from the Spanish Ministry of Science and Innovation through the PID2021-122645OB-100 project, the ‘Severo Ochoa’ Programme for Centers of Excellence in R&D (CEX2019-000917-S). The Generalitat de Catalunya, projects 2017SGR765 and 2017SGR1427, are also acknowledged. The authors participate in the Aerogels COST ACTION (CA 18125). J. G. has received financial support through the “la Caixa” INPhINIT Fellowship Grant for Doctoral Studies at Spanish Research Centers of Excellence (grant code: LCF/BQ/DI17/11620041), “la Caixa” Banking Foundation (ID100010434), Barcelona, Spain. J. G. was enrolled in the doctoral program in Materials Science at the UAB. M. T. (ref. RYC2019-026841-I) has a post-doctoral fellowship “Ramón y Cajal” supported by the “Ministerio de Ciencia e Innovación”, Spanish Government. A. G. has been supported by the fellowship from Instituto de Salud Carlos III with FEDER funds (FI17/00073). A. Rosell takes part of the RICORS-STROKE network from Instituto de Salud Carlos III with FEDER funds (RD21/0006/0007). This research work was performed in the framework of the Nanomedicine CSIC HUB (ref. 202180E048). Dr Daniel Padro is acknowledged for the supervision of MRI in vivo experiments in ReDIB-Molecular and Functional Imaging Facility at CIC BiomaGUNE which were accessible through the Spanish network of Singular Scientific and Technical Infrastructure (ICTS). Authors thanks Dr Fernando Herranz (IQM-CSIC) for fruitful discussions.