## Materials and Methods
### Magnetic Nanoparticles Preparation and Characterization  
The magnetic composite was prepared starting from the functionalization of microcrystalline cellulose (MCC). The reaction was performed using chlorosulfonic acid (CISO\({}_{3}\)H) according to the procedures already reported in the literature [55; 56; 57; 58] with some slight modifications. First, 10 g of MCC were dried overnight at 90 \({}^{\circ}\)C and suspended in 40 mL of dry hexane in inert atmosphere under vigorous mechanical stirring at room temperature. Then, 4 g of chlorosulfonic acid (36 mmol) were suspended in 10 mL of dry hexane and added dropwise at room temperature for 2 h. The mixture was stirred for additional 4 h at room temperature after finishing the addition. The obtained pale-yellow solid was washed several times with hexane (40 mL), water (100 mL), acetone (60 mL), and dried at vacuum pump. The sulfonic derivative was characterized via Fourier transform infrared (FTIR), elemental analysis, SEM, and acid-base titration with 0.1 N NaOH and phenolphthalein as an indicator in order to determine its acid content.  
The final magnetic nanoparticles were prepared using a [PERSON]'s co-precipitation procedure adapted for the preparation of biopolymeric composites reported by [PERSON] and coworkers [59]. First, 10 g of SC were placed in a three-necked round-bottom flask in dry conditions with 6.508 g of FeCl\({}_{3}\)-6 H\({}_{2}\)O (24 mmol) and 3.578 g of FeSO\({}_{4}\)-7 H\({}_{2}\)O (13 mmol). Therefore, 250 mL of distilled water were added, and the mixture heated at 60 \({}^{\circ}\)C for 20 min. Hence, the solution was heated at 80 \({}^{\circ}\)C, and 50 mL of 17.5% w/w of NaOH solution were added dropwise (2 mL/min ca. rate), maintaining a strong stirring to prevent the aggregation of the solid. After the end of the dripping, the suspension was maintained under energic stirring at 80 \({}^{\circ}\)C for another 60 min. During the process, the solution turned from an initial light brown color to a black one, signaling the end of the reaction. The black suspension obtained was cooled at room temperature and decanted with an Nd magnet externally to the flask. The supernatant was removed, and the solid was washed with distilled water until neutral pH. Finally, the product was washed three times with ethanol and dried at vacuum pump, obtaining 12.2 gr of magnetic brown powder (2.2 g of adsorbed magnetite). The product was characterized using FTIR and SEM.  
Elemental analysis was performed with a varioMICRO CHNS V4.0.10 (Elementar Analysensysteme GmbH, Langenselbold, DE, Germany) analyzer allowing obtaining the degree of substitution (DS) of the SC per glucose unit, using the following Equation (1) [60]:  
\[\text{DS}_{\text{S}}=\frac{\text{S}_{\text{N}}/32}{\text{C}_{\text{N}}/72}. \tag{1}\]  
FTIR spectra were acquired by a Shimadzu IRAffinity-IS Spectrometer (Shimadzu Italia S.r.l., Milano, IT, Italy) in the spectral region of 375 and 4000 cm\({}^{-1}\) with a resolution of 1 cm\({}^{-1}\), setting 50 scans for a single analysis and using the KBr pellets technique. The KBr pellets were obtained by mixing the sample with dry KBr powder (ratio 1:100) and pressing with a hydraulic press, at the pressure of 10 tons for 5 min. The resulting pellets were placed in the appropriate compartment of the instrument and exposed to the FTIR light beam for analysis.  
Surface characterization of the materials was carried out by a LEO 420 digital scanning electron microscope (SEM) (LEO Electron Microscopy, Ltd., Cambridge, UK); all samples were placed on a standard holder (stub) and stained with a gold alloy to avoid electric charges and to improve the quality of the images. Observations were made using a 15,000 V electron beam at a working distance of 9 mm and an incline of 20\({}^{\circ}\).