(B-73) Magnetoelastic Sensing Platform for Evaluating the Effects of Heparin/Collagen Layer-by-Layer Coatings

Introduction:: Magnetoelastic (ME) sensors are mass-sensitive sensors that can be wirelessly interrogated via magnetic fields. These sensors are typically fabricated from commercially available materials and functionalized with chemical/biological sensing elements to suit their specific applications. The non-invasive and functionalizable nature of these sensors make them good candidates for biological sensing. Previous work has shown that these sensors can be used to track cell growth and proliferation. This work focuses on evaluating the effects of heparin/collagen coatings on the growth and proliferation of human Mesenchymal Stromal Cells (hMSCs) in 2D cell culture by tracking cell growth via the magnetoelastic sensing platform.

Materials and Methods:: Bone marrow-derived hMSCs were obtained, expanded, and cryogenically stored in liquid nitrogen. hMSCs (PDL 13) were recovered from liquid nitrogen, thawed, seeded at 5,000 cells/cm², and grown to confluence. The cells were cultured in xeno-free media supplemented with 1% penicillin-streptomycin and xeno-free supplement (RoosterBio). Confluent cells were lifted with trypsin-EDTA, counted using an automatic cell counter and then diluted with media to the target seeding density. Cells were incubated at 37.0 °C, ~93% relative humidity, and under 5% CO₂ in a microbiological incubator.

Sensors were laser-cut from Metglas 2826MB and then coated with 10 µm Parylene-C. Coated sensors were treated with oxygen plasma in a reactive etching system. Experimental sensors were coated using a layer-by-layer (LBL) deposition process to create nine consecutive heparin/collagen layers ending in heparin. The magnetoelastic sensors were interrogated with custom solenoids fitted with magnets and connected to a network analyzer. Each sensor was placed in the rear well of a 2-well chamber slide into a sensor retainer designed to allow it to vibrate freely while remaining at the same position. The chamber slide was placed inside the solenoid to record the resonance spectrum of the sensor inside. To evaluate the effects of the heparin/collagen LBL coatings, an experiment was performed where coated and non-coated sensors were tracked using custom software developed to collect the impedance spectrum once every 15 minutes for 72 hours. Following each experimental procedure, the cells were fixed and stained with Hoescht 33342 nuclei stain. Cell growth profiles were validated using fluorescence microscopy.


Results, Conclusions, and Discussions:: As shown in Figure 1, the layer-by-layer coatings supported a denser and more proliferative population of hMSCs than the sensor surface alone. The greater change in impedance is the result of more cells being attached, which was validated by fluorescent microscope images. The experimentally coated sensors supported hMSC proliferation through 72 hours, while the cells on the control sensor reached a plateau around 52 hours. These results suggest that heparin/collagen layer-by-layer coatings support increased proliferation of cells compared to the non-coated sensors. These results also demonstrate that the magnetoelastic sensing platform can provide value as a process development tool for engineering cell culture surfaces.

The results indicate that magnetoelastic sensors are a viable approach to the continuous tracking of adherent cell growth remotely and non-invasively. Furthermore, this technology can provide biomanufacturers with a novel tool to aid in the design and development of tissue-culture surfaces. Continued development of this technology will focus on the adaptation of the monitoring system for different bioreactor systems. Further investigation into the effects of magnetic fields and mechanical stimulation (generated by the monitoring system) on cell phenotype and quality will be needed to support translation of this technology into clinical and industrial spaces.


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