Hyaluronic acid gel with small silicone phase separating

Hi all,
We are developing a serum with 2% sodium hyaluronate and a small silicone phase in suspension, but in stability we are seeing the gel separate after about 2 weeks at 45oC and about 4-6 weeks at 25oC, leaving a clear water layer on the bottom that slowly increases, and an upper milky layer. We are also developing a vitamin serum at the same time with the same base formula which is not displaying this behavior, so I am thinking it has to do with the hyaluronic acid - not sure if maybe there are too many water absorbing ingredients in competition for the water? Below is the formula, pH about 5 and forms a very thin gel.

QS water (about 73%)
5% glycerin
4% propanediol
0.03% citric acid
0.5% probiotic in maltodextrin 
0.2% sodium gluconate
3% spectrastat PHL (Caprylhydroxamic Acid,1,2-Hexanediol, Propanediol)
0.15% xanthan gum
0.1% sodium hyaluronate >1.8 MDa
0.1% sodium hyaluronate 1 - 1.8 MDa
0.2% sodium hyaluronate 0.2 - 0.6 MDa
1.6% sodium hyaluronate <20 kDa
6% dimethicone 100 cS
2% dimethicone/dimethiconol
2% liquid shea butter
1.6% Simulgel NS (Hydroxyethyl Acrylate/Sodium Acryloyldimethyl Taurate Copolymer, Squalane, Polysorbate 60)

Any ideas what might be causing the separation and how to counter it? We have tried replacing the xanthan with Sepimax Zen, but same result (and started separating about a week earlier). We don't want to increase the viscosity because of the packaging. Thanks in advance for any advice!

Comments

  • GordofGordof Member
    hi there 
    I think your idea to reduce some of the water-loving Components to not over-push the water and force it out of the gel could be a good try. 

    normally 2 % hyaluronic acid should be not problematic but maybe the combination makes it too much for the system. 

    if you maybe reduce the Xantangum and some of the glycerin as well as the propanediol and at some more water maybe it solves the issue. 

    Would love to hear if you could solve it 

    Tobias 
  • chemicalmattchemicalmatt Member, Professional Chemist
    @harryc, you have reached the limit of that oil load carry for the Simulgel product, especially considering that dimethicone gum blend has an ultra-high MW dimethicone imbedded within - difficult to suspend or emulsify in any circumstance besides a 100% silicone formula or a w/Si emulsion. Furthermore, your electrolyte load (sodium, sodium and more sodium) exacerbates the functional stability of that acrylate copolymer itself at the same time. Sepimax Zen and xanthan gum will not solve All the World's Problems either, as you've discovered (and many of our CC colleagues have yet to). 
  • @harryc I agree with @chemicalmatt. Polymeric surfactants don't work for every type of emulsions, and need to be aided sometimes by more traditional HLB-emulsifiers. Now, for heavy silicones (like gums), it could be worth to try using silicone emulsifiers, which were specifically designed for these systems.
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