# Cellulose-Encapsulated Magnetite Nanoparticles for Spiking of Tumor Cells Positive for the Membrane-Bound Hsp70

## TL;DR

Researchers developed magnetic cellulose microspheres that can detect and isolate tumor cells based on their surface protein Hsp70, showing higher efficiency for tumor cells compared to non-tumor cells.

## Contribution

A novel method using TKD-functionalized magnetic cellulose microspheres for selective tumor cell isolation based on membrane-bound Hsp70.

## Key findings

- TKD@MSCMNs extracted mHsp70-positive C6 glioma cells with 28% efficiency, significantly higher than for mHsp70-negative cells.
- Magnetic cellulose microspheres showed an average magnetic core size of ~17 nm and were successfully functionalized for targeted binding.
- The specificity of TKD peptide binding was confirmed using Flamma648-labeled Hsp70 and control microspheres.

## Abstract

The development of highly sensitive approaches for detecting tumor cells in biological samples remains a critical challenge in laboratory and clinical oncology. In this study, we investigated the structural and magnetic properties of iron oxide nanoparticles incorporated into cellulose microspheres of two size ranges (~100 and ~700 μm) and evaluated their potential for targeted tumor cell isolation. In the smaller microspheres, magnetite-based magnetic nanoparticles (MNPs) were synthesized in situ via co-precipitation, whereas pre-synthesized MNPs were embedded into the larger microspheres. The geometrical characteristics of the resulting magnetic cellulose microspheres (MSCMNs) were assessed by confocal microscopy. Transmission electron microscopy and X-ray diffraction analyses revealed an average magnetic core size of approximately 17 nm. Magnetic properties of the MNPs within MSCMNs were characterized using a highly sensitive nonlinear magnetic response technique, and their dynamic parameters were derived using a formalism based on the stochastic Hilbert–Landau–Lifshitz equation. To evaluate their applicability in cancer diagnostics and treatment monitoring, the MSCMNs were functionalized with a TKD peptide that selectively binds membrane-associated Hsp70 (mHsp70), yielding TKD@MSCMNs. Magnetic separation enabled the isolation of tumor cells from biological fluids. The specificity of TKD-mediated binding was confirmed using Flamma648-labeled Hsp70 and compared with control alloferone-conjugated microspheres (All@MSCMNs). The ability of TKD@MSCMNs to selectively extract mHsp70-positive tumor cells was validated using C6 glioma cells and mHsp70-negative FetMSCs controls. Following co-incubation, the extraction efficiency for C6 cells was 28 ± 14%, significantly higher than that for FetMSC (7 ± 7%, p < 0.05). These findings highlight the potential of TKD-functionalized magnetic cellulose microspheres as a sensitive platform for tumor cell detection and isolation.