Figure 2: Magnetic characterization of magnetically tunable hydrogels.

Electron Paramagnetic resonance (EPR) spectra of 20% PEGDMA (a), 50% PEGDMA (c) and GelMA (e) soaked into PBS (control), 10, 30 and 150 mg ml⁻¹ (in PBS) stable radical solution for 10–15 h. Images of gels for a range of concentration. Top (left) and side (right) images of soaked 20% PEGDMA (b), 50% PEGDMA (d) and GelMA (f), which showed a colour change depending on radical concentration. Gels are cylindrical: 3 mm in diameter, 1.5 mm in height. EPR spectra has been performed with the sum of ten scans for each condition. Comparison of spin density in 20% PEGDMA, 50% PEGDMA and GelMA after overnight soaking in stable radical solution (g). Testing antioxidant vitamin E treatment (h and i). EPR spectra (h) and spin densities (i) of samples s1, s2 and s3. Here s1 and s2 are controls, and s3 as the experiment sample. Sample s1: PEGDMA gel was soaked into radical solution. Sample s2: PEGDMA gel was soaked into radical solution, and then transferred into PBS (without vitamin E). Sample s3: PEGDMA gel was soaked into radical solution, and then transferred into 0.5 mg ml⁻¹ vitamin E, (+)-α-Tocopherol acetate. Spin densities were calculated computationally by integrating EPR spectra with trapezoidal rule. Horizontal lines connecting individual groups represent statistically significant difference (P<0.05). PEGDMA is abbreviated as PEG in the figure labels. Error bars represent s.d. from the mean (n=3–6).