Superparamagnetic iron oxide nanoparticles (SPIONs) conjugated with recombinant human epidermal growth factor (SPION–EGF) were studied as a potential agent for magnetic resonance imaging contrast enhancement of malignant brain tumors. Synthesized conjugates were characterized by transmission electron microscopy, dynamic light scattering, and nuclear magnetic resonance relaxometry. The interaction of SPION–EGF conjugates with cells was analyzed in a C6 glioma cell culture. The distribution of the nanoparticles and their accumulation in tumors were assessed by magnetic resonance imaging in an orthotopic model of C6 gliomas. SPION–EGF nanosuspensions had the properties of a negative contrast agent with high coefficients of relaxation efficiency. In vitro studies of SPION–EGF nanoparticles showed high intracellular incorporation and the absence of a toxic influence on C6 cell viability and proliferation. Intravenous administration of SPION–EGF conjugates in animals provided receptor-mediated targeted delivery across the blood–brain barrier and tumor retention of the nanoparticles; this was more efficient than with unconjugated SPIONs. The accumulation of conjugates in the glioma was revealed as hypotensive zones on T2-weighted images with a twofold reduction in T2 relaxation time in comparison to unconjugated SPIONs ( P <0.001). SPION–EGF conjugates provide targeted delivery and efficient magnetic resonance contrast enhancement of EGFR-overexpressing C6 gliomas.

The stress-inducible 72 kDa heat shock protein Hsp70 is known to be expressed on the membrane of highly aggressive tumor cells including high-grade gliomas, but not on the corresponding normal cells. Membrane Hsp70 (mHsp70) is rapidly internalized into tumor cells and thus targeting of mHsp70 might provide a promising strategy for theranostics. Superparamagnetic iron oxide nanoparticles (SPIONs) are contrast negative agents that are used for the detection of tumors with MRI. Herein, we conjugated the Hsp70-specific antibody (cmHsp70.1) which is known to recognize mHsp70 to superparamagnetic iron nanoparticles to assess tumor-specific targeting before and after ionizing irradiation. In vitro experiments demonstrated the selectivity of SPION-cmHsp70.1 conjugates to free and mHsp70 in different tumor cell types (C6 glioblastoma, K562 leukemia, HeLa cervix carcinoma) in a dose-dependent manner. High-resolution MRI (11 T) on T(2)-weighted images showed the retention of the conjugates in the C6 glioma model. Accumulation of SPION-cmHsp70.1 nanoparticles in the glioma resulted in a nearly 2-fold drop of T*(2) values in comparison to non-conjugated SPIONs. Biodistribution analysis using NLR-M(2) measurements showed a 7-fold increase in the tumor-to-background (normal brain) uptake ratio of SPION-cmHsp70.1 conjugates in glioma-bearing rats in comparison to SPIONs. This accumulation within Hsp70-positive glioma was further enhanced after a single dose (10 Gy) of ionizing radiation. Elevated accumulation of the magnetic conjugates in the tumor due to radiosensitization proves the combination of radiotherapy and application of Hsp70-targeted agents in brain tumors.

BackgroundGlioblastoma is the most devastating primary brain tumor of the central nervous system in adults. Magnetic nanocarriers may help not only for a targeted delivery of chemotherapeutic agents into the tumor site but also provide contrast enhancing properties for diagnostics using magnetic resonance imaging (MRI).MethodsSynthesized hybrid chitosan-dextran superparamagnetic nanoparticles (CS-DX-SPIONs) were characterized using transmission electron microscopy (TEM) and relaxometry studies. Nonlinear magnetic response measurements were employed for confirming the superparamagnetic state of particles. Following in vitro analysis of nanoparticles cellular uptake tumor targeting was assessed in the model of the orthotopic glioma in rodents.ResultsCS-DX-SPIONs nanoparticles showed a uniform diameter of 55 nm under TEM and superparamagentic characteristics as determined by T1 (spin-lattice relaxation time) and T2 (spin-spin relaxation time) proton relaxation times. Application of the chitosan increased the charge from +8.9 to +19.3 mV of the dextran-based SPIONs. The nonlinear magnetic response at second harmonic of CS-DX-SPIONs following the slow change of stationary magnetic fields with very low hysteresis evidenced superparamagnetic state of particles at ambient temperatures. Confocal microscopy and flow cytometry studies showed an enhanced internalization of the chitosan-based nanoparticles in U87, C6 glioma and HeLa cells as compared to dextran-coated particles. Cytotoxicity assay demonstrated acceptable toxicity profile of the synthesized nanoparticles up to a concentration of 10 μg/ml. Intravenously administered CS-DX-SPIONs in orthotopic C6 gliomas in rats accumulated in the tumor site as shown by high-resolution MRI (11.0 T). Retention of nanoparticles resulted in a significant contrast enhancement of the tumor image that was accompanied with a dramatic drop in T2 values (P<0.001). Subsequent histological studies proved the accumulation of the nanoparticles inside glioblastoma cells.ConclusionHybrid chitosan-dextran magnetic particles demonstrated high MR contrast enhancing properties for the delineation of the brain tumor. Due to a significant retention of the particles in the tumor an application of the CS-DX-SPIONs could not only improve the tumor imaging but also could allow a targeted delivery of chemotherapeutic agents.

Functionalized superparamagnetic iron oxide nanoparticles (SPIONs) have emerged as potential clinical tools for cancer theranostics. Membrane‐bound 70 kDa heat shock protein (mHsp70) is ubiquitously expressed on the cell membrane of various tumor types but not normal cells and therefore provides a tumor‐specific target. The serine protease granzyme B (GrB) that is produced as an effector molecule by activated T and NK cells has been shown to specifically target mHsp70 on tumor cells. Following binding to Hsp70, GrB is rapidly internalized into tumor cells. Herein, it is demonstrated that GrB functionalized SPIONs act as a contrast enhancement agent for magnetic resonance imaging and induce specific tumor cell apoptosis. Combinatorial regimens employing stereotactic radiotherapy and/or magnetic targeting are found to further enhance the therapeutic efficacy of GrB‐SPIONs in different tumor mouse models.

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The study demonstrated that Hsp70-SPION conjugate intravenously administered in C6 glioma model accumulated in the tumors and enhanced the contrast of their MR images.

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Bone-marrow derived mesenchymal stem cells (MSCs) exert anti-tuberculosis effects due to their potential to repair damaged tissues and modulate inflammatory immune responses. MSCs were reported to be recruited to the Mycobacterium tuberculosis (Mtb) affected sites in the organism. However, due to limitations of presently applied in vivo imaging techniques the trafficking and biodistribution of MSCs in Mtb-infected organisms is not possible. In the current study MSCs were labeled with superparamagnetic iron oxide nanoparticles (SPIONs) as a negative MR contrast agent for imaging the biodistribution of MSCs in vivo. Trafficking of SPIONs-labeled MSCs was analyzed in a preclinical model of renal tuberculosis in male Chinchilla rabbits (n = 18) following intravenous administration on the days 0, 2, 3, and 7 employing a highly sensitive method of non-linear longitudinal magnetic response (NLR-M2) measurements. Within 48 h after injection, nanoparticle-labeled MSCs accumulated predominantly in lung, spleen, liver tissues, and paratracheal lymph nodes with subsequent decrease over the observation period of 7 days. The recruitment of MSCs to Mtb-affected organs was further proven by immunohistological analysis. NLR-M2 allowed the detection of SPIONs-labeled cells at low concentrations in different organs and tissues giving insights of in vivo mesenchymal stem cells trafficking in organism after TB infection.