Encapsulation of Manganese Oxide Nanoparticles to Maximize MRI Signal Intensity

Mara Looney-Sanders*, Celia Martinez de la Torre, Andrey Bobko, and Margaret Bennewitz

Department of Chemical and Biomedical Engineering, West Virginia University, Morgantown, WV 265062 and Department of Biochemistry, West Virginia University, Morgantown, WV 26506

Presentation Category: Physical Sciences & Engineering (Poster Presentation #145)

Student’s Major: Engineering

Breast cancer is one of the most common cancers affecting women worldwide. To detect breast cancerearly, magnetic resonance imaging (MRI) currently uses gadolinium (Gd) chelatesas the main contrast agent. However, Gd chelatesdo not differentiate between malignant and benign tumors, which leads to false positives (misdiagnosed benign breast tumors),and cancer may be missed (false negatives). Manganese oxide (MnO) nanoparticles (NPs)have superior MRI signalsand show potential in targeting malignant tumors using pH sensitivity, where the contrast willturn “ON” after internalization by the cancer cells. The ultimate goal of ourresearchis to develop a contrast agent to reduce falsepositive and falsenegative imaging results associated with current breast MRI. Two methods were tested to make the MnO NPs hydrophilic: 1) MnO NPs were encapsulated with poly(lactic-co-glycolic) acid (PLGA) polymer using an oil-in-water emulsionprocedure or 2) MnO NPs were coated with phospholipid micelles. Based on transmission electron microscopy (TEM),dynamic light scattering (DLS), and Fourier transform infraredspectroscopy (FTIR), PLGA encapsulation resulted in smaller NP diameters. As smaller particles have a higher surface-area-to-volume ratio, they were expected to dissolve faster in low pH conditions. PLGA MnO NPswere incubated at three pHs over 24hrincluding pH 7.4 (blood pH), 6.5 (pH of tumor extracellular space), and 5 (endosome/lysosome pH). Significant MRI contrast and reducedT1values wereonly observedat pH 5, meaning that PLGA MnO NPsneed to be targeted inside cancer cellsto create a robust bright signal.

Funding: West Virginia University

Program/mechanism supporting research/creative efforts: WVU's Research Apprenticeship Program (RAP) & accompanying HONR 297-level course