Challenges and Future Prospects of Superparamagnetic Iron Oxide Nanoparticles (SPIONs) in Nanomedicine: A Focus on Toxicity, Imaging, and Theranostics

Background: Superparamagnetic iron oxide (SPIO) nanoparticles is a magnetic sentinel lymph node (SN) tracer. Since no radioisotope (technetium, Tc99) is used, there is no need for a nuclear medicine department. Compared to the use of Patent Blue V® (PB), no allergic reactions have been reported so far. However, a long lasting skin staining has been observed. We compared skin staining in women who were injected with both SPIO (MagTrace®) and PB. Methods: SPIO, Tc99 and PB were injected in all women in the SentiDose study (2017-2019), a SPIO dose optimizing trial, including six Swedish hospitals. For PB, a 1.0ml sub/intradermal, peri-areolar injection was administred. For SPIO either a 1.5ml retro-areolar (Cohort 1.5, n=163) or a 1.0ml peri-tumoral (Cohort 1.0, n=164) interstitial injection was administred. Staining was assessed by telephone interviews at 6, 12 and 24 months post surgery, and mean size calculations only included women with a stain. Mastectomy cases (n=63) were excluded from the analysis. SN detection rates will be reported elsewhere. Results: In Cohort 1.5, 27.7% (33/119) of the women had a SPIO stain and 25.2% (30/119) a PB stain at 6 months (p=0.66). The mean stain sizes were 13.4 and 9.1cm2 (p=0.16), respectively. At 12 months, 20.8% still had a SPIO stain and 17.6% a PB stain (p=0.91), with mean sizes of 4.1 and 3.7 cm2 (p=0.73), respectively. At 24 months, from the 11 women followed so far, all 3 with an earlier SPIO stain and 7 of 8 with an earlier PB stain are now stain free. In Cohort 1.0, 16.5% (25/145) had a SPIO stain and 16.9% (24/139) had a PB stain at 6 months (p=0.94). The mean stain sizes were 11.8 and 8.4 cm2 (p=0.42), respectively. Nine women were not injected with PB. After 12 months, 15.9% still had a SPIO stain and 12.4% a PB stain (p=0.42). The mean sizes were 5.1 and 2.6 cm2 (p=0.99), respectively. Comparing all women at 6 months, 22.0% had a SPIO stain and 20.5% a PB stain (p=0.12) with mean sizes 12.5 and 8.6 cm2 (p=0.83), respectively. At 12 months, 17.8% had a residual SPIO stain and 14.9% a PB stain (p=0.37) with mean sizes 4.6 and 3.3 cm2 (p=0.16), respectively. The difference in incidence of SPIO staining between Cohort 1.5 and Cohort 1.0 was statistically significant at 6 months, but not at 12 months, 27.7% vs. 16.5%, (p=0.04) and 20.8% vs 15.9% (p=0.28), respectively. The difference in SPIO stain sizes between the cohorts was neither significant at 6 months, 13.4 vs 11.8 cm2(p=0.61) nor at 12 months, 4.1 vs 5.1 cm2 (p=0.30). Conclusion: No statistically significant differences in incidence or stain size were observed between SPIO and PB. The 2-year follow up will be completed during 2021. The 1.0ml compared to 1.5ml SPIO dose, resulted in fewer but equally large stains at 6 months, but there was no difference at 1 year. Table 1. Skin staining after SPIO and Patent Blue (PB) for sentinel lymph node detectionTracerStaining/SizeStaining/Size6 months12 monthsSPIO 1.5ml, n=11927.7%/13.4cm220.8%/4.1cm2SPIO 1.0ml, n=14516.5%/11.8 cm215.9%/5.1 cm2PB, n=25820.5%/8.6 cm214.9%/3.3 cm2 Citation Format: Madeleine Warnberg, Andreas Karakatsanis, Fredrik Nilsson, Christine Obondo, Lida Pistiolis, Imad Mohammad, Carlos Dussan Luberth, Staffan Eriksson, Abdi-Fatah Hersi, Fredrik Wärnberg. A prospective comparison of skin staining after sentinel lymph node biopsy, using blue ink (PB) and superparamagnetic iron oxide nanoparticles (SPIO) tracers [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS1-52.

The major challenges in clinical oncology are the selective delivery of large amounts of therapeutic agents into tumor cells, accurate evaluation of the drug delivery, and timely assessment of the therapeutic response. Theranostic nanoparticles with the abilities to target tumors, carry therapeutic agents, and produce contrasts or signals for tumor imaging offer an exciting means to address these challenges and have a great promise for effective cancer treatment. We have developed a multifunctional theranostic magnetic iron oxide nanoparticle (IONP) platform that utilizes receptor-targeted IONPs to carry single or multiple therapeutic agents for drug delivery and optical and magnetic resonance imaging (MRI) for monitoring the delivery and response. To overcome physical and intrinsic barriers that reduce efficiency of drug delivery and confer drug resistance in human cancers, our theranostic IONPs are targeted to urokinase plasminogen activator receptor (uPAR), thereby taking advantage of high levels of uPAR expression in tumor cells, angiogenic endothelial cells, and active tumor stromal cells. These IONPs allow the drug to overcome the physical barrier in stroma-rich tumors, such as pancreatic cancer and triple-negative breast cancer (TNBC), by serving as carrier vehicles for passage through the tumor endothelial cell layer and stromal fibroblasts, thereby increasing the efficiency of delivery into tumors but not into normal tissues. Moreover, these uPAR-targeted IONPs can destroy tumor blood vessels, producing an antiangiogenesis effect that enhances treatment efficacy. To make the IONPs suitable for repeat administrations, a recombinant amino terminal fragment (ATF) of the receptor binding domain of uPA, a high affinity natural ligand for uPAR, was produced in a bacterial expression system to minimize the immune response. ATF peptides were conjugated to amphiphilic polymer-coated IONPs to produce the receptor-targeted MRI contrast nanoparticles. The ATF can also be labeled with a new near-infrared dye (NIR-830) developed by our group prior conjugation to generate uPAR-targeted IONPs with dual optical and MR imaging modalities. Based on the surface functionalization of the IONPs and chemical properties of drug molecules, we developed approaches for encapsulating hydrophobic drugs or conjugating hydrophilic drugs to the IONPs, resulting in theranostic IONPs which carry chemotherapy drugs, such as doxorubicin (ATF-IONP-Dox) and gemcitabine (ATF-IONP-Gem). After delivery into tumor cells, the drug molecules can be released efficiently from the nanoparticles using pH-sensitive and/or lysosomal enzyme-sensitive drug release mechanisms. Targeted delivery, intracellular drug release, and the cytotoxic effect have been demonstrated in breast and pancreatic cancer cell lines as well as in an endothelial cell line. The efficacy of ATF-theranostic IONPs and the ability of MRI to monitor drug delivery and response were examined in orthotopic animal tumor models, including a triple-negative mouse mammary tumor model, a basal type human breast ductal carcinoma in situ xenograft model, and a human pancreatic cancer xenograft model. We found that systemic administration of ATF-IONP-Dox significantly inhibited the growth of orthotopic breast and pancreatic tumors in these animal models. Additionally, preoperative treatment of primary tumors with ATF-IONP-Dox significantly decreased the growth of primary tumors and further inhibited local recurrence and lung metastasis in 4T1 mouse mammary tumor model. Using our established MRI methods, the efficiency of intratumoral drug delivery and changes in tumor sizes and tissue contrasts can be detected by T1- and T2-weighted MRI using a clinical field strength MRI scanner in the tumor models. Histological analysis showed that the uPAR-targeted theranostic IONPs are selectively accumulated in primary breast tumor, and primary and peritoneal metastatic pancreatic tumor lesions. Theranostic IONP-mediated doxorubicin delivery reduced systemic toxicity since pathological changes in the liver and heart tissues and serological abnormalities were detected in mice treated with free doxorubicin at a dose of 10 mg/Kg of body weight but not in mice after treatment with an equivalent dose of ATF-IONP-Dox. The effect of ATF-IONP-Gem on the growth of orthotopic human pancreatic cancer was also examined in an orthotopic human pancreatic cancer xenograft model. ATF-IONP-Gem showed significant tumor growth inhibition in the tumor-bearing mice that received systemic delivery of ATF-IONP-Gem containing 2 mg/kg of body weight of gemcitabine. However, there was no significant tumor growth inhibition in the mice that received an equivalent dose of free gemcitabine or nontargeted IONP-Gem. The presence of IONP-drug in the tumor lesion can be detected as bright signals using an ultra-short TE MRI scan method. At present, we are developing uPAR-targeted IONPs carrying multiple therapeutic agents in a single IONP to further enhance the efficacy of the treatment. Our theranostic IONPs have the potential to significantly impact cancer treatment in neoadjuvant therapy of TNBC or locally advanced pancreatic cancer. Preoperative neoadjuvant chemotherapy is usually administered to patients with TNBC to reduce the size of the primary tumor and to treat locally advanced tumors and micrometastatic lesions in order to lower the incidence of local and distant recurrence. The unique differential response to chemotherapy within the TNBC patient population makes it crucial to assess early tumor responses to the therapy and to ensure the most effective chemotherapies while avoiding unnecessary toxicity. About 40% of pancreatic cancer patients are diagnosed with unresectable locally advanced disease at presentation because their tumors have directly invaded into adjacent normal structures and blood vessels. It is feasible to treat these patients with the targeted theranostic IONPs to reduce the burden of the primary tumor and peritoneal metastatic lesions so that the patients can be candidates for potentially curative surgical resection. Additionally, NIR optical signal produced from the dual imaging theranostic IONPs allows optical image-guided surgery to detect and completely remove residual tumors that are resistant to drug treatment. In summary, uPAR-targeted theranostic IONPs developed by our research team have great potentials for the development of an integrated treatment-imaging protocol for pancreatic cancer and TNBC. Such a protocol can significantly improve the survival rate of cancer patients. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr SY20-02. doi:10.1158/1538-7445.AM2011-SY20-02

Nanotechnology, the area of study involving nanoparticles, century; medical fields. The nanotechnology is one of the fastest growing sectors of the high-tech economy in the 21st industry, it is currently undergoing unprecedented development in nowadays especially in areas of biological research for clinical, environmental and life science applications. The most frequently used nanoparticles are superparamagnetic iron oxide (SPIO) nanoparticles and semiconductor quantum dots (QDs). SPIO nanoparticles with nanometer sizes and superparamagnetic properties are widely used for labeling and sorting cells or organelles, magnetic resonance imaging, targeted drug delivery, and hyperthermia. QDs combined the unique size-dependent physical properties, excellent chemical and photochemical stability, controlled and increased endocytosis, enhanced cooperative binding activity, and easy introduction of multi-functionality for targeted delivery and imaging, and became the most promising labeling tool for life science studies. Both types of nanomaterials provide special approaches for complex studies and play very important roles in modern biomedical research. However, non-specific uptake of QDs and SPIO nanoparticles is a major concern because it can lead to false positives or false results. Hence, we report cellular uptake studies on SPIO nanoparticles and QDs conducted on breast cancer cell line SK-BR3. The results show that both QDs and SPIO nanoparticles have very strong non-specific cellular uptake. With specially designed blocking buffer (BBB) the non-specific signals were significantly decreased.

Super paramagnetic iron oxide nanoparticles (SPIONs) have proved that they have tremendous potential to use in various biomedical applications. But the surface of pure iron oxide nanoparticles so fast oxidized, that is a major drawback for biomedical applications. Covered SPIONs have good surface activity. Therefore, the first goal was to synthesize the naked SPIONs. Then we modified with 3-Aminopropyltriethoxysilane (APTES) and trichlorotriazine (TCT). Several techniques measurements were used for characterization the size and special features of naked SPIONs and TCT modified SPIONs. These results show that the SPIONs were synthesized. After that the SPIONs are coated with casein and indicate that there is an interaction between them. Moreover, we have investigated magnetic properties and anticancer effects of casein-coated SPIONs. Therefore, we showed casein could be used to increase the biocompatibility of the surface of SPIONs. At the end, we show that bonding of dipyridamole (DIP) to the surface of casein-coated SPIONs have good magnetite properties for targeted drug delivery. We find that the release of DIP by casein-coated SPIONs-DIP was sensitive to pH. Both release curves in pH 5.5 and 7.4 showed the release of DIP by β-casein coated SPIONs-DIP better than α-casein coated SPIONs-DIP. The cell culture studies of the casein-coated SPIONs-DIP provide good anticancer effects against both breast and prostate cancer cell lines. Here, we propose a simple and inexpensive chemical method for preparation of highly biocompatible core–shell SPIONs and binding of drug for using in targeted drug delivery system. Communicated by Ramaswamy H. Sarma

We report on the fabrication of organic/inorganic hybrid micelles of amphiphilic block copolymers physically encapsulated with hydrophobic drugs within micellar cores and stably embedded with superparamagnetic iron oxide (SPIO) nanoparticles within hydrophilic coronas, which possess integrated functions of chemotherapeutic drug delivery and magnetic resonance (MR) imaging contrast enhancement. Poly(ε-caprolactone)-b-poly(glycerol monomethacrylate), PCL-b-PGMA, and PCL-b-P(OEGMA-co-FA) amphiphilic block copolymers were synthesized at first by combining ring-opening polymerization (ROP), atom transfer radical polymerization (ATRP), and post- modification techniques, where OEGMA and FA are oligo(ethylene glycol) monomethyl ether methacrylate and folic acid-bearing moieties, respectively. A model hydrophobic anticancer drug, paclitaxel (PTX), and 4 nm SPIO nanoparticles were then loaded into micellar cores and hydrophilic coronas, respectively, of mixed micelles fabricated from PCL-b-PGMA and PCL-b-P(OEGMA-co-FA) diblock copolymers by taking advantage of the hydrophobicity of micellar cores and strong affinity between 1,2-diol moieties in PGMA and Fe atoms at the surface of SPIO nanoparticles. The controlled and sustained release of PTX from hybrid micelles was achieved, exhibiting a cumulative release of ~61% encapsulated drugs (loading content, 8.5 w/w%) over ~130 h. Compared to that of surfactant-stabilized single SPIO nanoparticles (r(2) = 28.3 s(-1) mM(-1) Fe), the clustering of SPIO nanoparticles within micellar coronas led to considerably enhanced T(2) relaxivity (r(2) = 121.1 s(-1) mM(-1) Fe), suggesting that hybrid micelles can serve as a T(2)-weighted MR imaging contrast enhancer with improved performance. Moreover, preliminary experiments of in vivo MR imaging were also conducted. These results indicate that amphiphilic block copolymer micelles surface embedded with SPIO nanoparticles at the hydrophilic corona can act as a new generation of nanoplatform integrating targeted drug delivery, controlled release, and disease diagnostic functions.

Iron oxide (IO) nanoparticles hold great promise as diagnostic and therapeutic agents in oncology. Their intrinsic physical properties make IO nanoparticles particularly interesting for simultaneous drug delivery, molecular imaging, and applications such as localized hyperthermia. Multiple non-targeted IO nanoparticle preparations have entered clinical trials, but more exciting, new tumortargeted IO nanoparticle preparations are currently being tested in preclinical settings. This paper will analyze the challenges faced by this new theranostic modality, with a specific focus on the interactions of IO nanoparticles with the innate and adaptive immune systems, and their effect on nanoparticle biodistribution and tumor targeting. Next, we will review the critical need for innovative surface chemistry solutions and strategies to overcome the immune interactions that prevent existing tumor-targeted IO preparations from entering clinical trials. Finally, we will provide an outlook for the future role of IO nanoparticles in oncology, which have the promise of becoming significant contributors to improved diagnosis and treatment of cancer patients.

Superparamagnetic iron oxide (SPIO) nanoparticles have become a popular strategy of cancer treatment and molecular imaging because of their versatile properties and biocompatibility. A variety of studies have shown the exciting potential of functionalized SPIO nanoparticles, such as surface-coated, targeted ligandconjugated, and/or drug-loaded SPIO nanoparticles, as powerful tools for targeted imaging and therapy. Moreover, the applications of SPIO nanoparticles that integrate diagnosis and therapy in SPIO nanoparticles facilitate the monitoring of therapeutic efficacy during treatment. In the present review, we primarily concentrate on the recent advancements in the field of SPIO nanoparticles in terms of synthesis, targeted therapy, and cancer imaging.

Influence of iron oxide nanoparticles on bending elasticity and bilayer fluidity of phosphotidylcholine liposomal membranes

Supermagnetic Iron Oxide Nanoparticles (SPIONs) are nanoparticles that have an iron oxide core and a functionalized shell. SPIONs have recently raised much interest in the scientific community, given their exciting potential diagnostic and theragnostic applications. The possibility to modify their surface and the characteristics of their core make SPIONs a specific contrast agent for magnetic resonance imaging but also an intriguing family of tracer for nuclear medicine. An example is 68Ga-radiolabeled bombesin-conjugated to superparamagnetic nanoparticles coated with trimethyl chitosan that is selective for the gastrin-releasing peptide receptors. These receptors are expressed by several human cancer cells such as breast and prostate neoplasia. Since the coating does not interfere with the properties of the molecules bounded to the shell, it has been proposed to link SPIONs with antibodies. SPIONs can be used also to monitor the biodistribution of mesenchymal stromal cells and take place in various applications. The aim of this review of literature is to analyze the diagnostic aspect of SPIONs in magnetic resonance imaging and in nuclear medicine, with a particular focus on sentinel lymph node applications. Moreover, it is taken into account the possible toxicity and the effects on human physiology to determine the SPIONs' safety.

There is an enormous interest in exploiting nanoparticles in various biomedical applications since their size scale is similar to that of biological molecules (e.g., proteins, DNA) and structures (e.g., viruses and bacteria). As the field continues to develop, quantitative and qualitative studies on particle-cell interaction, with respect to their size and surface, are required in order to advance nanotechnology for biomedical applications. This will be important for assessing nanoparticle toxicity (i.e. translocation into cells and interference with viability and cellular function), for advancing nanoparticles for imaging, drug delivery, and therapeutic applications (i.e. targeting specific cells, organs, or tumors), and for designing multifunctional nanoparticles. Due to the lack of systematic study to date, data are difficult to compare since the parameters and particles in each of the published studies differ substantially. However, the scientific community, in general, agrees that the size and colloidal behavior play a crucial role in cellular interaction/uptake, biodistribution, clearance and cytotoxicity. Surface functionalization of nanoparticles still remains a difficult task and represents not only a chemical challenge but constitutes a basic requirement for future scientific investigations. Alteration of surface charges and/or stabilization by the addition of bi- / multi-functional molecules, such as differently charged proteins or plasmids, frequently leads to particle flocculation and rapid sedimentation. The biological functionality, in such cases, is achieved by covalent binding of bio-active molecules on a preexisting single surface coating. A fixed bed magnetic reactor has been developed with a quadrupole repulsive arrangement of permanent magnets which allows for surface derivatization by magnetically immobilizing superparamagnetic iron oxide nanoparticles (SPIONs). The yield and quality of the resulting functionalized SPIONs was significantly improved with reduction in reaction times using solid phase synthesis strategy. In this way, pH changes across the isoelectric point, washing steps or even solvent exchanges could be easily tolerated thereby avoiding the problems of colloidal instability during the derivatization steps. It was shown that the surface functionalization of SPIONs using a magnetic fixed bed reactor was superior to the liquid phase reaction in terms of reaction yield, particle size distribution, colloidal stability and scalability. In particular, cell organelle targeting peptide derivatized on SPIONs surface was obtained from the reactor. The combination of functionalized SPIONs and their ability to be recovered using a magnetic column coupled with biomolecular mass spectrometry has allowed to explore a complex intracellular pathway using a peptide that is known to target HeLa cell organelle. Here the concept of biomolecular interaction network elucidation with an organelle-targeting peptide was demonstrated. Besides that, the colloidal stability and cellular uptake of polymer coated SPIONs were also studied. Preliminary results showed that minor modifications of the nanoparticle surface lead to an altered behavior in stability, uptake, and toxicity. Also, different charges on the particle surfaces were found responsible for differential uptake of particles in cell media. Colloidal stability and its influence on biological properties will provide a profound base for future discussions on toxicity and potential application of nanoparticles in the field of biomedicine.

The next-generation nanoparticles overcome the drawbacks of early nanoplatforms by integrating multiple functions, such as drug delivery, controlled drug release, and combination therapy, into a single system. This study examines the biomedical applications of quantum dots, carbon nanotubes, superparamagnetic iron oxide nanoparticles, and layered double hydroxides for the delivery of breast cancer drugs. They are termed as "nextgeneration" nanoparticles, as they are advanced nanocarriers that offer a comprehensive and alternative approach towards breast cancer treatment, providing enhanced specificity and efficacy compared to their predecessors. The development of these nanoplatforms has significantly enhanced drug bioavailability and reduced toxicity. A comprehensive analysis of a nanotechnology-based drug delivery system was conducted. The keywords used for this review were "Breast Cancer", "Targeted Drug Delivery", "Quantum Dots", "Carbon Nanotubes", "Layer Double Hydroxides", and "Superparamagnetic Iron Oxide Nanoparticles". The inclusion criteria consisted of studies focusing on breast cancer, targeted drug delivery, and therapeutic applications of these nanocarriers. In contrast, exclusion criteria included studies focusing on the synthesis of nanocarriers and the diagnostic applications of these nanostructures. The study underscores their mechanisms, limitations, and future development directions. Additionally, the study tracks the evolution of the nanocarriers since their early discovery. Next-generation nanocarriers (QDs, CNTs, SPIONs, and LDHs) have strong therapeutic potential owing to their precisely engineered properties, such as size, shape, morphology, and surface modifications. Their trigger-initiated drug release mechanisms enable targeted delivery with a better rate of tumor penetration, while their ability to co-deliver multiple therapeutic agents addresses drug resistance issues and provides synergistic effects. Comparative analyses have revealed that these advanced nanoplatforms significantly outperform early-generation carriers in terms of bioavailability, reduced toxicity, and treatment efficacy across various breast cancer types. Next-generation nanoplatforms offer unprecedented opportunities for targeted and efficient cancer treatment. Continued research and innovation are necessary to address existing challenges and to optimize their therapeutic potential for clinical applications.

The superparamagnetic iron oxide nanoparticle (SPIO) ‘theranostics’, which contain imaging probes for tumor diagnosis and therapeutic compounds for therapy in a single nanoparticle, might provide significant benefits compared with exiting tumor imaging and therapeutic strategies. In this review, we summarize the progress of SPIO ‘theranostics’ that integrate tumor targeting, multimodality imaging, and gene delivery or targeted drug and prodrug delivery. This review describes various methods of SPIO synthesis, surface coating and characterization. Different tumor-targeting strategies, such as antibody fragments, nucleotides and receptor ligands, are discussed to improve SPIO delivery for multimodality imaging. We also examine the utility of SPIOs for gene delivery, siRNA delivery and imaging. Several methods for drug encapsulation and conjugation onto SPIOs are compared for targeted drug delivery, site-specific release and imaging-guided drug delivery. Finally, we also review the pharmacokinetics (including biodistribution) of SPIOs based on their characteristics.

Hierarchical self-assembly of magnetic nanoclusters for theranostics: Tunable size, enhanced magnetic resonance imagability, and controlled and targeted drug delivery

Superparamagnetic iron oxide (SPIO) nanoparticles are prevalent as nanoprobes for molecular magnetic resonance imaging (MRI), providing negative contrast by locally affecting the spin-spin (T2) proton relaxation of water. SPIO nanoparticles are typically Fe3O4 nanocrystals and are commonly used as a negative MRI contrast agent, implementing various surface functionalization techniques to provide molecular targeting to biological macromolecules. The authors recently demonstrated molecular MRI (Figure 1) of epidermal growth factor receptor (EGFR), an extensively studied oncoprotein, in human prostate and head-and-neck cancer cell lines using monoclonal antibodies covalently conjugated to phospholipid micelle encapsulated 12 nm single crystalline SPIO nanoparticles, demonstrating molecular targeting capabilities via surface functionalization [1].

Molecular imaging of cancer is a rapidly growing field given the enhanced specificity of disease detection it can achieve. As a radiation-free tomographic instrument, magnetic particle imaging (MPI) continues to demonstrate its effectiveness in molecular imaging. However, a long-standing issue within nanomedicine for tumor detection is the sparse uptake of superparamagnetic iron oxide nanoparticles (SPIONs) at the tumor site, thereby limiting its detection by MPI. To support achieving the full potential of MPI, SPION properties must be carefully modified for each application. The SPIONs size, magnetization, and surface coating impacts its biodistribution, tumor specificity and accumulation thereby influencing the generated MPI signal. Here we compare commercially available PrecisionMRX SPIONs in three coatings: a carboxylic acid functionalized SPION, a methoxypolyethylene glycol functionalized SPION and a Trastuzumab conjugated SPION. Our results demonstrated the influence SPION modifications have on magnetic relaxation and therefore the MPI sensitivity of the tracer. Modification of SPIONs also impacted their blood circulation time, inherently the carboxylic acid SPION cleared almost immediately from circulation, while the methoxypolyethylene glycol SPION displayed exceptional immune evasion and remained in the blood pool for over 6 hours. In a xenograft ovarian cancer mouse model, we achieved significant tumor uptake of the SPION through intravenous delivery and accurately quantified the iron amount both in and ex vivo using MPI and ICP-MS. This study furthers our understanding of SPION behavior in MPI and continues the exploration for a safe and potent tumor imaging strategy, presenting a powerful, biocompatible SPION platform that holds immense potential for the future of MPI.