Uricase is an important enzyme in the purine metabolic pathway of the organism, which can catalyze the oxygen and uric acid to avoid gout and hyperuricemia caused by excessive accumulation of uric acid in the blood. Urease liposomes (ULPs) overcome the shortcomings of other uricase preparations by packaging drugs in the lipid bilayer, with good stability and high safety, and have a certain function of targeting and sustained release [1,2]. But in the preparation process, its performance will be affected by the buffer system. Tris-HCl and Bicine-NaOH are the two most commonly used buffers, and this paper will summarize their effects on the in vitro properties of ULPs.

Tris-HCl is a buffer system commonly used in biochemical experiments and is widely used as a solvent for nucleic acids and proteins. It has the advantage of little interference to the biochemical process. Bicine-NaOH belongs to the Good's buffer system. It does not participate in and interfere with the biochemical reaction process, and can be resistant to chemical and enzymatic effects. Therefore, they are often used in cell, protein and other biochemical experiments.

Preparation of uricase liposomes

The reverse evaporation method is a very suitable preparation method for encapsulating water-soluble macromolecules. The preparation method has high encapsulation rate, good particle size and good stability, and the preparation method is simple [3]. A certain proportion of lecithin and cholesterol were placed in a round bottom flask, then added a certain amount of chloroform, remove the chloroform under reduced pressure in the rotary evaporator to form a uniform film. The ether was added to redisperse, then a Tris-HCl buffer (pH = 8.5) containing 2mg of uricase was added to the solution. Ice-bath ultrasonic to form uniform emulsion dispersion system, reduced pressure distillation to gel collapse, the uniform milky white milk liquid was formed. Tris-HCl buffer was added and filtered through a 0.22μm filter to prepare ULPs sample. The same method was used to obtain ULPs samples with Bicine-NaOH as the buffer.

Comparison of in vitro properties of uricase liposomes

Stability: Urease liposomes were stored in a dark seal at 4°C and the activity of uricase in the sample was removed at a given time. It was found that the storage stability of uricase liposomes prepared using Bicine-NaOH buffer was more stable.

In summary, Bicine-NaOH buffer was superior to Tris-HCl buffer in the preparation of uricase liposomes, which improved the encapsulation efficiency of ULPs and the activity and stability of uricase in vitro. Suggesting that it will also bring better treatment in clinical administration.

References

[3] Zhang Mi. Effects of Buffer Types on Urease Liposomes. Master's thesis, Chongqing Medical University, 2014.