The invention provides a new method of synthesizing cross-linked hyaluronic acids, compositions thereof, tubes and syringes containing such compositions alone or in combination with PRP/BMC, new devices for PRP/BMC preparation, and uses thereof in cell culture, skincare and joint preservation. The invention provides in particular a method for the production of a crosslinked gel (preferably of desired molecular weight and/or concentration) from at least one first polymer (preferably hyaluronic acid), comprising the steps of: viii) homogenizing said first polymer, ix) hydrating said first polymer in a basic solution, x) crosslinking said basic solution by adding at the least one crosslinking agent at a higher temperature than room temperature, xi) neutralizing said basic solution in an acidic solution, xii) homogenizing said solution, xiii) mixing said solution with a supplemental quantity of a second polymer (preferably a second polymer of substantially the same molecular weight and/or concentration as said first polymer), and xiv) purifying said solution.
