{
    "protocol": "Layer-by-layer (LbL) deposition method of polyelectrolytes involves successive deposition of polycations and polyanions onto the surface of a material, with a rinsing step after each deposition. Various methods can be employed for the build-up of LbL coatings, including dip-coating, spin-coating, and spraying, with dip-coating being the most commonly used but also time-consuming. To develop coatings, different parameters such as temperature, pH, and ionic strength must be controlled. The formation of coatings requires careful selection of polyelectrolytes to ensure desired properties, and evaluation methods such as quartz crystal microbalance with dissipation monitoring (QCM-D), atomic force microscopy (AFM), confocal microscopy, or ellipsometry may be used to assess film thickness.To synthesize hydrophilic polymers with functional groups, prepare polycations (PAR30 and chitosan variants) and polyanions (28 different polymers) at 0.5 mg/mL in either Tris/NaCl buffer (10 mM Tris, 0.15 M NaCl, pH 7.4) for PAR30 or sodium acetate buffer (70 mM sodium acetate, 80 mM NaCl, pH 5) for chitosan. Clean a SiO2 coated crystal for 30 min with 2% Hellmanex, rinse with water, and perform final cleaning with 1 M HCl for 10 min, followed by rinsing with water. Deposit the chosen polycation onto the crystal for 5 min, then rinse with the respective buffer for 5 min. Repeat the deposition and rinsing steps for a total of 8 bilayers at a flow rate of 250 µL/min."
}