BME Postdocs Seminar: Sandra Mara Ferreira & Daniela P. Valdés

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Dr. Sandra Mara Ferreira: “GABA modulates pancreatic beta-cell function through Ca2+ signaling”
Dr. Daniela P. Valdés: “Do scientists dream of plastic mice? Phantoms in Magnetic Hyperthermia and Magnetic Particle Imaging”
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Sandra Mara Ferreira, PhD
Postdoctoral Fellow, Phelps Lab
Biomedical Engineering, University of Florida

“GABA modulates pancreatic beta-cell function through Ca2+ signaling”

Abstract: Pancreatic islets are endocrine micro-organs located in the pancreas and are composed of multiple endocrine cell types (beta, alpha, and delta). These cells secrete different hormones (insulin, glucagon, and somatostatin, respectively) that modulate blood glucose and, in a paracrine fashion, control the adjacent cells. An imbalance of the secretions of these hormones can lead to metabolic diseases. Type 1 diabetes results from the failure or loss of insulin secretion. The pancreatic islets also secrete signaling molecules that modulate the pancreatic islet function. One of these molecules is the neurotransmitter gamma-aminobutyric acid (GABA), synthesized and secreted by beta cells. GABA is an inhibitory neurotransmitter in the central nervous system (CNS), and beta cells are the location that has the most GABA outside of the CNS, indicating GABA is essential for pancreatic islet function. However, the exact role of GABA in the pancreatic islets is not yet clear. Here, we investigated the modulation of beta cell function by GABA to clarify and reveal its role in the islet in both normal and disease states.

Bio: Dr. Sandra Mara Ferreira is a postdoctoral assistant in the Phelps Lab. Originally, she is from Brazil and got her undergraduate degree in Biological Sciences from the University of Maringa, in southern Brazil. She got her Master’s and PhD in Molecular and Functional Biology at the University of Campinas, Sao Paulo, Brazil. Her studies have been focused on pancreatic islet biology, specifically on the mechanisms that control pancreatic beta cell function.
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Daniela P. Valdés, PhD
Postdoctoral Fellow, Rinaldi-Ramos Lab
Chemical Engineering, University of Florida

“Do scientists dream of plastic mice? Phantoms in Magnetic Hyperthermia and Magnetic Particle Imaging”

Abstract: Biomedical imaging and therapeutic-technology development have traditionally relied on animal models for their testing and validation. Synthetic phantoms engineered to replicate physiological and/or anatomical properties offer a controlled alternative that supports the ethical principles of the 3Rs: replace animal use where possible, reduce the number of animals required, and refine protocols to minimize pain. This seminar will highlight how phantoms enable the simulation of complex in vivo scenarios and advance magnetic nanoparticle (MNP) research in therapy and imaging.

Magnetic hyperthermia, as a cancer treatment modality, relies on heat generation through the relaxation of MNPs within the intracellular environment. The efficiency of this process, often quantified by the specific power absorption (SPA), can be influenced by the viscosity of the medium in which the MNPs are dispersed [1]. To address this, we used adjustable-viscosity polyacrylamide gels [2] as a cytosol emulator to characterize MNP behavior under physiologically relevant conditions. Moreover, the temperature increment during hyperthermia experiments was measured with a thermographic camera and spatio-temporal profiles were obtained from the videos, contributing to the development of non-invasive temperature monitoring techniques [3]. To translate these findings into a realistic treatment workflow, we use phantom mice with a fillable breast cancer tumor to test MNPs and experimental conditions, as well as develop a treatment workflow.

For these novel MNP-based treatments, information on the particle distribution is key to evaluating their effectiveness as the literature suggests that only 0.7% of the injected dose reaches the target regions [4]. In magnetic particle imaging (MPI), MNPs that are being injected into a subject for treatment can be also used as tracers to get a distribution map that can be registered with an anatomical image. We used an anatomically correct mouse phantom based on the Digimouse atlas for imaging of different in vivo scenarios. The fillable liver was used to emulate MNP accumulation due to macrophage uptake and a set of capillaries was placed in cavities to evaluate different types of tumors: superficial (flank), internal (brain) and metastasis (lung). The segmentation of the MPI signals in the target sites was done through threshold (with 50% of the maximum criteria) and constant volume spheres. Quantification of the iron mass in these segments was done conventionally and by subtracting the signal in a background scan with a filled liver but no capillary, accounting for the spillover effect from the adjacent liver [5].

These phantom-based experiments enable the systematic investigation of MNP behavior under relevant conditions, both physiologically and anatomically, supporting both imaging and therapeutic development. These results not only advance the precision of MNP-based therapies but also contribute to reproducible and ethically-responsible research aligned with the 3Rs framework.

References
[1] D. Cabrera, J Nanoparticle Res 17, 121 (2015)
[2] T. Yano, Biosci Biotechnol Biochem 57, 528 (1993)
[3] D.P. Valdés et al., Phys Rev Applied 19, 014042 (2023)
[4] S. Wilhelm et al., Nat Rev Mater 1, 5 (2016)
[5] A. Shakeri-Zadeh et al., npj imaging 3, 20 (2025)

Bio: Dr. Daniela P. Valdés is a Postdoctoral Associate in the Rinaldi-Ramos Laboratory, Department of Chemical Engineering at the University of Florida (2025), where she focuses on magnetic nanoparticle (MNP) based imaging and therapeutic technologies. In particular, she generates workflows for magnetic particle imaging (MPI) segmentation and quantification of MNPs in vitro and in vivo. She earned her PhD in Physics at the Magnetic Resonance Laboratory, Centro Atómico Bariloche, supported by a CONICET scholarship in 2024. Her doctoral thesis, supervised by Dr. Emilio De Biasi and Dr. Enio Lima Jr., is titled Magnetic Hyperthermia in Phantoms: From Theory to Experiment. Daniela has also served as a teaching assistant for the Experimental Physics I (2019-2022) and Quantum Mechanics II (2023-2024) courses at Instituto Balseiro. She holds an MSc in Physics (2018) and a BSc in Physics (2017) from Instituto Balseiro, where she investigated the MNP interaction effect magnetic hyperthermia treatment performance.