Specord 50 plus uv vis spectrophotometer

The total tannins content (TTC) was determined using the Bate-Smith method as described in [35 ]. The proanthocyanidin concentration was obtained by multiplying the difference in absorbance at 550 nm (Specord 50 PLUS UV/VIS spectrophotometer, Analytik Jena, Jena, Germany) between tube A₂ and tube A₁ by 19.33, which is the absorptivity coefficient of cyanidin after the acidic cleavage of the condensed tannins (Bate-Smith reaction), as summarized in Equation (9): $$Total tannins \left[{\mathrm{g} \mathrm{L}}^{-1}\right]=19.33·\left(A_1-A_2\right)$$
where A₁ is the absorbance of the hydrolyzed sample, A₂ is the absorbance of the unhydrolyzed sample and 19.33 is the calculation factor. The TTC is expressed as the tannins mass over the mass of dry matter (mg g⁻¹). All analyses were performed in duplicate.

DOG, DOG/MOFA, DOG/ICG, and DOG/MOFA/ICG nanoparticles were prepared according to the above screening results. Typically, DOG (24.0 mg); DOG (24.0 mg), and MOFA (2.4 mg); DOG (24.0 mg) and ICG (2.4 mg); DOG (24.0 mg), MOFA (2.4 mg) and ICG (2.4 mg) were respectively dissolved in 4 mL of DMSO in a round-bottomed flask and kept stirring for 4 h. The above solutions were slowly added into 20 mL of ultra-pure water and vigorously stirred for another 2 h. The obtained solutions were transferred into a 3.5 kDa molecular weight cut-off dialysis bag and dialyzed in ultra-pure water for 24 h, and the water was replaced every 4 h.
Next, a series of characterizations on the obtained DOG, DOG/MOFA, DOG/ICG, and DOG/MOFA/ICG nanoparticles were performed. The zeta potential, size distribution, and PDI of obtained nanoparticles were analyzed by laser particle size analyzer. Transmission electron microscopy (TEM) was conducted on an HT7700 transmission electron microscope (Hitachi, Japan). The UV data of different nanoparticles was measured by a Specord^® 50 Plus UV-vis spectrophotometer (Analytik Jena, Germany). The fluorescence spectrum was implemented on the RF-6000 Spectro fluorometer (Shimadzu, Japan).

Total phenolic content (TPC) was determined using the Folin–Ciocalteu method [34 ]. The absorbance was measured at 760 nm (Specord 50 PLUS UV/VIS spectrophotometer, Analytik Jena, Jena, Germany), and the results were expressed as milligrams of gallic acid equivalent per gram of dry matter (mg GAE g⁻¹_dm). All analyses were performed in triplicate.