O7.06 * MAGNETIC NANOPARTICLES CONJUGATED TO A RECOMBINANT HEAT SHOCK PROTEIN HSP70 FOR TARGETING EXPERIMENTAL GLIOBLASTOMA

Abstract

Superparamagnetic nanoparticles (SPIONs) due to their unique properties could be applied for theranostic approach in neuro-oncology. Accumulation and retention of the nanoparticles in the tumour can be directly imaged by MRI proving its application as contrast agents. Due to high heating capacity SPIONs could also be applied for thermotherapy of brain tumours. To further increase the biocompatibility and targeted delivery of SPIONs we have functionalized the surface of particles with recombinant heat shock protein Hsp70. Nuclear magnetic resonance (NMR) spectra and magnetic relaxation times of the synthesized conjugates T1, T2, T2* were measured with the help of an NMR spectrometer (CXP-300, Bruker) in a magnetic field of 7.1 T. Hsp70-SPIONs relaxivity corresponded to the properties of negative contrast agents with a hypointensive change of resonance signal in MR imaging. In series of in vitro experiments we observed enhanced internalization of the SPION-Hsp70 conjugates by C6 glioma cells in comparison to control SPIONs. The contrast-enhancing ability of SPION-Hsp70 conjugates was analyzed in the model of intracranial C6 glioma in rodents. The rat images were acquired with the help of a Bruker Avance II NMR spectrometer equipped with a microtomographic accessory at a magnetic field of 11 T. In vivo analysis of the conjugates distribution in the model of intracranial glioma revealed the retention of the functionilzed particles inside the tumour site. Negative contrast tumor enhancement in the T2-weighted MR images was higher in the case of Hsp70-SPIONs in comparison to non-modified SPIONs. Histological analysis of the brain sections confirmed the retention of the Hsp70-SPIONs in the glioma tumor but not in the adjacent normal brain tissues. Immunofluoresence studies confirmed that retention in the glioma of nanoparticles was due to the receptor-mediated endocytosis of the SPION-Hsp70 conjugates via the CD40 receptors. The uptake of SPION-Hsp70 by tumour cells permitted MRI contrast enhancement after systemic delivery while sparring surrounding normal brain tissues.