Janus Magnetic Polymeric Colloids Gradient Thin Films of Amino Dextran Coated Core–Shell Poly (Styrene/Divinylbenzene/Methacrylic Acid) for Ultrasensitive Magnetic Resonance Imaging

The present study focuses on developing novel gradient thin films for surface‐based magnetic resonance imaging of fluids such as water. Four types of magnetic‐polymer colloids were investigated as T2 contrast agents, including Janus magnetic‐polystyrene and core–shell magnetic‐poly(styrene/divinylbenzene/methacrylic acid) particles. These colloids were coated with amino dextran to enhance their performance. Key factors such as emulsion composition, particle size, and surface properties were systematically examined. Gradient thin films were fabricated on glass slides using a layer‐by‐layer self‐assembled multilayer (LbL‐SAMu) technique. The films consisted of positively charged poly(dimethyl diallyl ammonium chloride) and negatively charged magnetic‐polymer colloids. The developed colloids and thin films were characterized by their surface wettability, surface morphology, and zeta potential. These films exhibited relatively improved hydrophilicity and T2 contrast. The utilization of such gradient thin films as molecular probes could enhance clinical MRI for in vitro diagnosis. This study indicated that thin‐film gradients can offer a facile technique for unique cellular imaging via a lab‐on‐chip device to enable effective point‐of‐care molecular diagnostics.