YES! There is a risk of liposomes transporting impurities past the body's safety barriers. You should use quality ingredients and be careful with experimenting on yourself -- especially with plant extracts. Stick with highly purified, isolated ingredients.
There also is a second danger to beware of with liposomal vitamin C: You must use the SODIUM ASCORBATE form of vitamin C, or add baking soda to the Ascorbic Acid in the proper ratio to form Sodium Ascorbate. If you just use Ascorbic Acid, you could cause Acidosis, which is acidification of the blood. This extremely dangerous, and very possibly fatal.
Please do not kill yourself with this powerful technology. You will get vitamin C banned for the rest of us.