The Effects Of Citric Acid Release Mode And SiO₂ Nanoparticles On Intestinal Protease Activity In Vitro

Oral administration of peptide and protein drugs are strongly limited by the serine proteases based degradation in intestinal and side effects of co-administration protease inhibitor are also obvious.One such concept extensively explored is that of acidic inhibition of proteolysis.However,pH was changed with the intestinal peristalsis,and it could affect the inhibition effect of protease activity.Therefore,a sustainable acidic environment was designed in this paper to avoid degradation of peptide and protein drugs happens in the enzymatic environment.Amino acid esters substrates and casein were used to verify the changes in the proteases activity in vitro while the pH value rises up from acidic conditions,and inactivated proteases by acid could be reactivated immediately with environmental pH recovery to 5.0 regardless of how long the proteases inactivation lasted.A sustained-release tablet containing citric acid was designed and prepared,and it could effectively reduce the pH value below 5.0 and maintain the pH for 4 h in the dissolution-reaction medium.And higher than 80%of the substrates were survived within 5.0 h of incubation in an open system simulated the flow environment in small intestine,indicating that the sustained-release tablet loading CA can efficiently inhibit the?-CT and trypsin activities.When nanomaterials are exposed to a physiological fluid,the proteins contained in these fluids will immediately adsorb onto the surface forming“protein corona”,which may affect the biological characteristics of the protein.SiO₂ nanoparticle as the commonly used drug excipient enters the gastrointestinal tract with oral drug may also absorb protease and inhibit the protease activity.In this paper,three different sizes of SiO₂ nanoparticles were prepared to investigate the interaction with?-CT and trypsin in different mediums.The formation of protein corona was found and protease adsorption amount was related to particle size and concentration of protease.Nanoparticles size was increased and negative values of Zeta potential was decreased after adsorbent process and the proteases activity on nanoparticles surface was declined comparing to the free protease.With the spectroscopic investigation,the conformation was changed after absorbing.The hydrophobic groups of protease exposed,and?-helix content decreased.So SiO₂ nanoparticles could affect the intestinal physiological environment and the medical security of it needs to be further studied.