Dma 2980 dynamic mechanical analyzer

The ¹H NMR spectra were recorded using a ECX400 (JEOL, Akishima, Tokyo, Japan), ECA600 (JEOL), and a BioSpin AV-300 spectrometer (Bruker, Yokohama, Kanagawa, Japan). The powder XRD measurements were performed using a X’Pert Pro MPD diffractometer (PANalytical B.V., Almelo, The Netherlands) with Ni-filtered Cu Kα radiation (λ = 0.15418 nm). GPC measurements were conducted using a system consisting of a LC-20AD pump (Shimadzu, Kyoto, Japan), a CTO-10A column oven, an RID-10A refractive index detector, and two TSK gel Super HZM-N (4.6 × 150 mm; TOSOH, Tokyo, Japan) columns. Chloroform was used as the eluent at a flow rate of 0.25 mL/min at 40 °C. Polystyrene samples were used as standards. The DMA were performed using a DMA 2980 Dynamic Mechanical Analyzer (TA Instruments, Tokyo, Japan) at heating rate of 5 °C/min at 1 Hz using a supramolecular polymeric film (5 mm × 20 mm).

A DMA 2980 Dynamic Mechanical Analyzer (TA Instruments, New Castle,
DE) was used to determine Young’s modulus of the hydrogels.
Hydrogel samples in vitro were prepared as described
in Section 2.3, at
20 wt % (corresponding to 1:2, 1:5 molar ratios of maleimide:furan
moieties in the polymers), whereas the same concentration and ratios
of the ex vivo hydrogels were formed in vitreous,
as described in Section 2.7. After extracting the hydrogels from the porcine eye vitreous
body, the gels were cut to allow mechanical tests. All hydrogels (ex vivo and in vitro) were prepared with
approximately 3 mm × 4 mm in height and diameter. The gels were
placed between parallel plates, and a force ramp was applied at a
rate of 0.5 N/min up to a total force of 8 N at room temperature.
The raw data were analyzed using TA Universal Analysis software, and
Young’s modulus (E) was calculated from the
slope of the linear section (from 0 to 22% strain) of the stress–strain
curve. Data are represented as mean ± standard deviation (SD)
(n = 3 for in vitro gel and n = 6 in two porcine eyes for the ex vivo formed gels).