Vertex 80v

Fourier-transformed infrared (FTIR) Spectroscopy provides information on bonding modes in organic molecules by absorption of infrared radiation, which depends the vibrational response of the functional groups^{60 (link)}. FTIR absorbance spectra of KBr pellets prepared with 0.2% biochar, 0.4% freeze-dried washing solutions or 0.4% freeze-dried control compost were measured with a Vertex 80 v (Bruker) with 128 scans. A KBr pellet without sample was used for background measurements.

To prepare pan-Ab–MNPs, carboxylated MNPs (7.0 mg) were washed successively with 1 mL deionized water and 1 mL MES buffer (10 mM, pH 6.0), and collected using a magnetic separator. Then, the particles were incubated at 37 °C for 30 min with 1 mL MES buffer (10 mM, pH 6.0) containing a mixture (10 μL) of 800 mM EDC and 1 M NHS, followed by washing three times in the same buffer. Partially carboxylated MNPs were incubated with a 100 μg/mL pan-Ab solution for 1.5 h at 37 °C. Subsequently, the remaining carboxyl-activated groups were blocked by incubation with 1 mL of 1% BSA in MES buffer (10 mM, pH 6.0) for 2 h at 25 °C. Finally, the pan-Ab–MNPs were washed three times with the same buffer and stored at 4 °C for further experiments. The optimal EDC/NHS ratio for efficient antibody conjugation (see Figure S1) was determined by zeta potential measurements (Zetasizer Nano ZS, Malvern Panalytical, Malvern, UK). The conjugation of pan-Ab to the MNP surface was characterized by zeta potential measurements, UV–Vis spectroscopy (Optizen POP, Mecasys, Daejon, Korea), Bradford assays, and in vacuo Fourier transform infrared (FT-IR) spectroscopy (VERTEX 80v, Bruker, Ettlingen, Germany).

X-ray diffraction (XRD, Bruker D8 SSS, Karlsruhe, Germany) was used to analyze the phase structure of the prepared materials. The diffractometer was set at 30 kV and 20° to 60° (2θ) at a rate of 1°/min. In addition, a Fourier-transform infrared spectrometer (FTIR, Vertex 80v, Bruker, Karlsruhe, Germany) was used to analyze the various functional groups in the prepared materials. An EZ-Test instrument (Shimadzu, Kyoto, Japan) was used to evaluate the mechanical properties of the samples by determining their diameter tension strength (DTS). Firstly, the samples were printed into cylindrical shapes with a diameter of 6 mm and a height of 2 mm. A compressive speed of 1 mm/s was applied from above until the specimens were crushed. Six independent scaffolds were prepared for this test, and the test was repeated thrice, with the average recorded. The data were recorded in distance (mm) and load (N), and the corresponding stress–strain graph is presented in our results. To observe the surface morphology, the specimens were first dried, then dehydrated in ethanol and coated with platinum prior to observation. A scanning electron microscope (SEM, JEOL JSM-7800F, Tokyo, Japan) at an acceleration voltage of 20 kV was used to observe the surface topography of the specimens.

Infrared spectra were recorded on FTIR spectrometer Vertex 80v (Bruker, Germany) equipped with the liquid nitrogen cooled MCT narrow band detector. The spectral resolution was set at 2 cm^-1. Spectra were acquired by co-adding 400 scans. The sample chamber and the spectrometer were evacuated during the measurements. FTIR spectra were recorded in transmission mode. Samples were deposited at CaF₂ substrate from 100 μM solution and dried in air; blank CaF₂ substrate was used as a reference. Parameters of the bands were determined by fitting the experimental contour with Gaussian-Lorentzian form components using the GRAMS/AI 8.0 (Thermo Scientific, USA) software.