Method for depositing nano-objects on the surface of a polymer gel comprising zones with distinct rigidities

A method of depositing nano-objects on the surface of a gel comprising a polymer matrix comprising at least two contiguous zones of distinct rigidity, said method comprising:

• a) providing a gel comprising a polymer matrix and a solvent within the polymer matrix, the polymer matrix forming a three-dimensional network capable of swelling in the presence of said solvent, wherein the solubility of the polymer matrix at 1 bar and 25° C. in the solvent is less than 1 g/L, the polymer matrix comprising at least two contiguous zones of distinct rigidity exhibiting a rigidity gradient greater than or equal to 0.1 kPa/μm, then
• b) depositing nano-objects with an average diameter of 1 to 1000 nm on the surface of the gel, then
• c) evaporating the solvent from the gel at least until a variation in a rate of evaporation of the solvent from at least one least rigid zone of the gel is not constant over time, by which the nano-objects migrate towards at least one more rigid zone of the gel and a gel is obtained whose surface is at least partially coated with the nano-objects, and where the surface density of the nano-objects of the at least one most rigid zone among the at least two contiguous zones is greater to that of the at least one least rigid zone among the at least two contiguous zones, wherein evaporation of the solvent comprises at least two periods, a first evaporation period and a second evaporation period;
• wherein during the first evaporation period, solvent is continuously removed from the gel surface by capillary forces and the solvent content decreases at a constant rate;
• wherein during the second evaporation period, the diffusion forces become predominant over the capillary forces and the removal of the solvent from the gel is controlled by the diffusion of the solvent into the pores of the gel towards its surface;
• wherein during c), the evaporation rate reaches a critical evaporation rate at a critical evaporation time Tc, which marks the transition between the first and the second evaporation periods,
• wherein said critical evaporation time Tc is not identical between the at least one most rigid zone and the at least one least rigid zone,
• wherein the polymer matrix of the gel comprises a polyacrylamide, said polyacrylamide being obtained from the polymerization of acrylamide and N,N′-methylenebisacrylamide;
• wherein the solvent present within the polymer matrix of the gel is an aqueous solution;
• wherein the nano-objects are not cells;
• and
• wherein when the nano-objects are proteins and/or peptides and/or polysaccharides, and
• wherein the method further comprises:
• d) covalent grafting of the proteins and/or the peptides and/or the polysaccharides on the gel.