{
    "protocol": "Preparation of HPAA-PAM coating: The substrates after UV irradiation were immersed into the PAA-PAM monomer solution (4.26 g AM, 1.08 g AA, 0.02 g APS and 0.05 g MBAA, 30 mL H2O) for SCIRP to grow a hydrogel coating. After removal from the monomer solution, the substrates aged for 5 min at room temperature, followed by rinsing with deionized water five times. Preparation of HPNIPAM-PAA coating: The substrates after UV irradiation were immersed into the monomer solution (6.78 g NIPAM, 0.864 g AA, 0.02 g APS and 0.05 g MBAA, 40 mL H2O) for SCIRP for 25 min. Following removal from the monomer solution, the substrates were allowed to age for 5 min at room temperature and then rinsed with deionized water five times. Preparation of HPVA-PHEMA coating: 6.5 g HEMA, 0.01 g MBAA, 0.02 g APS and 0.1 g AA were dissolved in 50 mL H2O (solution A), while 20 g PVA was dissolved in 100 mL H2O (solution B). Solution A was mixed with solution B at a ratio of 1.5:1. The substrates after UV irradiation were immersed in the mixed monomer solution for SCIRP for 25 min, followed by a freeze-thaw process (-40 °C to 20 °C for 3 cycles) and rinsed with deionized water five times. Preparation of HPOEGMA-PAA coating: The substrates after UV irradiation were immersed into the POEGMA-PAA monomer solution (6.5 g OEGMA, 1.08 g AA, 0.01 g MBAA, 0.02 g APS, 40 mL H2O) for SCIRP for 25 min, then aged for 5 min at room temperature and rinsed with deionized water five times. Preparation of HPOEGMA-PAA-PHEMA coating: The substrates after UV irradiation were immersed in the POEGMA-PAA monomer solution (3.75 g OEGMA, 3.25 g HEMA, 1.08 g AA, 0.01 g MBAA, 0.02 g APS, 20 mL H2O) for SCIRP for 25 min, aged for 5 min at room temperature, then rinsed with deionized water five times.Preparation of HPVA-PAA-PAM coating on Ti substrate: First, 4.26 g AM, 1.08 g AA, 0.02 g APS and 0.05 g MBAA were dissolved in 30 mL H2O (solution C), 20 g PVA was dissolved in 100 mL H2O and heated to 100°C until complete dissolution (solution B); then, solution C was mixed with solution B at a volume ratio of 1:1; finally, the substrates after UV irradiation were immersed in the above mixed monomer solution to perform SCIRP for 2 min and put into the freeze-dryer to experience freezing (-40°C) and thawing (20°C) for 3 cycles. After the cyclic freezing-thawing process, the Ti substrate with the HPVA-PAA-PAM coating was rinsed with deionized water five times to remove unreacted monomers.  Preparation of HPHEMA-SA-Ca coating on Ti substrate: First, 6.5 g HEMA, 0.01 g MBAA, 0.02 g APS and 1 g SA were dissolved in 50 mL H2O and stirred until complete dissolution; then, the substrates after UV irradiation were immersed into the above monomer solution to perform SCIRP for 2 min; finally, the Ti substrate with HPHEMA-SA coating was immersed into CaCl2 solution (2%) for 2 h. Preparation of patterned hydrogel coating on Ti substrate: First, 5.91 g CA and 5.09 g FeCl3·6H2O were dissolved in 150 mL deionized water, and 1 mol/L NaOH solution was added to the above solution until the pH reached 4.0. Then, the substrate deposited with the PDA coating was immersed into the above mixed solution for 3 h. Subsequently, the treated substrate was placed under the programmable UV light source of a 3D printer for 5 min to reduce Fe3+. Next, the substrate after irradiation with UV light was immersed in monomer solution A to grow a patterned hydrogel coating for a certain time. Correspondingly, the Ti substrate with the growed patterned PAA-PAM hydrogel coating after removal from the monomer solution was allowed to naturally age for 5 min at room temperature. Finally, the sample after aging was rinsed with deionized water five times to further remove unreacted monomers.1. Immerse PDA-decorated medical devices in an aqueous solution of dopamine (2 mg/mL, in 10 mM Tris buffer, pH 8.5) under stirring for 24 h to decorate the PDA layer. 2. Rinse the PDA-decorated devices with deionized water and alcohol to remove unreacted chemicals. 3. Dissolve 5.91 g CA and 5.09 g FeCl3·6H2O in 150 mL deionized water. 4. Add 1 mol/L NaOH solution until the pH reaches 4.0. 5. Immerse the PDA-decorated devices in the mixed solution for 3 h. 6. Expose the devices to UV light (365 nm, 15 mW/cm2) for 2 min to produce Fe2+ in situ. 7. Immerse the devices in solution A to grow hydrogel coatings for a specified time. 8. Allow the devices with grown PAA-PAM hydrogel coating to naturally age for 5 min at room temperature. 9. Rinse the aged devices with deionized water five times to further remove unreacted monomers."
}