Preparation,Pharmacokinetic And Pharmacodynamicstudy On The New Oral Formulations Of Marine Polysaccharide PSS

With the deep development of marine resources, the research and development on marine drugs attract more and more attention, especially the bioactive marine polysaccharides. Propylene glycol alginate sodium sulfate (PSS) is the first marine polysaccharide drug in China, a milestone for marine drug research. Currently, the routes of administration of PSS are oral tablets and intravenous injection in clinical. However, there are some side effects of PSS with intravenous administration. Furthermore, the oral bioavailability of PSS is low due to poor absorption. Due to the limitations of traditional analysis techniques and methods, there are not many suitable methods to study the pharmacokinetic characteristics of PSS.Therefore, it is significant to establish more sensitive and reliable quantitative method in the biological samples, to study the pharmacokinetic characteristics in vivo and to develop new oral formulations of PSS in order to improve its oral absorption and oral bioavailability.Two quantitative methods of PSS in rat plasma were established, which were the fluorescent labeling method and the high performance liquid chromatographic method with postcolumn fluorescence derivatization. The results showed that both methods were sensitive, accurate and reliable, and suitable for the pharmacokinetic study of PSS in vivo. Compared with HPLC method with postcolumn fluorescence derivatization, the fluorescent labeling method was complicated, time-consuming and could not be applied to pharmacokinetic studies in people. It was easy to operate and didn’t need the pretreatment of samples by the HPLC method with postcolumn fluorescence derivatization, and it was suitable for the pharmacokinetic studies in people. Therefore, the HPLC method with postcolumn fluorescence derivatization was chosen as the method of the pharmacokinetic study in vivo of marine polysaccharide drug PSS. The pharmacokinetic results showed that the oral bioavailability of PSS was low and the absorbance into blood was slow, which may be due to the large molecular weight of PSS and its difficulty through the tissue spaces and biofilm barrier.Nanotechnology is the key technology of the 21st century, in view of several notable relevant characteristics, such as the smaller size, higher capacity of loading hydrophilic drugs, and a better performance of controlled release, etc. Nanotechnology is now used in improving the oral absorption of protein, peptide and polysaccharides. Poly lactic-co-glycolic acid (PLGA) is extensively used as a pharmaceutical material because of its biocompatibility and biodegradability. In order to improve the oral availability of PSS, PSS-loaded PLGA nanoparticles (PSS-NP) were prepared by the double (W1/O/W2) emulsion and solvent evaporation methods. The preparation conditions of PSS-NP were optimized and the average size of PSS-NP was 181.8 nm, the zeta potential was-17.8 mV, the entrapment efficiency was 75.80%and the drug loading efficiency was 10.83%. The drug release in vitro was investigated and the results showed that PSS-NP underwent two stages, sudden release first and then sustained release, which indicated that the drug-loaded modes of PSS-NP were by surface absorption and internal embedment. The pharmacodynamic results of PSS-NP showed that PSS-NP had a good hypoglycemic effect after continuous oral administration of PSS-NP to normal mice for 12 days, which revealed that nano formulations can improve the oral absorption of PSS and enhance its oral pharmacodynamics.Taking into account of the low oral pharmacodynamics of PSS and its structural characteristics, it was speculated that PSS may degrade and lose its effective active groups under the acidic environment in the stomach, so its oral pharmacodynamics were affected. In this study, the changes of molecular weight of PSS powder and tablets and the APTT time changes in vitro were tested in artificial gastrointestinal fluid at different times. The results indicated that the molecular weights of PSS powder and tablets were significantly reduced in artificial gastric solution after different times, while there was little change in artificial intestinal solution. Furthermore, the APTT time of PSS in vitro was significantly reduced in artificial gastric solution. It can be inferred that molecular weights of PSS were decreased and its active groups may lose in the acidic environment in the stomach, which affected the oral efficacy of PSS. In order to avoid the degradation and inactivation of PSS in the acid environment, the enteric-coated nano formulations of PSS were prepared on the basis of PSS-NP in this study. Eudragit L30D-55 was chosen as the enteric coating material and the preparation conditions were optimized. The average size of enteric PSS-NP was 372.1 nm, the zeta potential was-13.4 mV, the entrapment efficiency was 68.78% and the drug loading efficiency was 8.79%. Compared with PSS-NP (39.06%), the cumulative release percentage of enteric PSS-NP within 2 hours in artificial gastric solution was 8.38%, which reduced PSS releasing effectively and avoided the degradation and inactivation of PSS in acidic environment in the stomach.The pharmacokinetic characteristics of PSS and its two novel oral formulations—PSS-NP and enteric PSS-NP were compared by the HPLC method with postcolumn fluorescence derivatization. The results showed that PSS-NP and enteric PSS-NP can improve the plasma concentrations of PSS and improve the oral bioavailability of PSS, and the enteric PSS-NP was better than PSS-NP. Furthermore, PSS-NP can prolong the residence time of PSS in plasma and exhibit the sustained release character. While enteric PSS-NP can be intestinal absorbed better and absorbed into the blood faster. The results of the pharmacodynamics in vivo of PSS, PSS-NP and enteric PSS-NP showed that PSS-NP and enteric PSS-NP can prolong the APTT time and reduce the blood glucose level of normal rats compared with PSS. In addition, PSS enteric nanoparticles could significantly lower the serum total cholesterol and increase the insulin levels, regulate the blood glucose and lower the body weight in db/db mice.The above results showed that the specific, sensitive, accurate and reliable method established in this study can provide the basis for the pharmacokinetic study methods of PSS and other marine polysaccharide drugs. In order to improve the oral absorption and enhance the oral pharmacodynamics of PSS, two new oral formulations—PSS-NP and enteric PSS-NP were prepared in this study, which provided a theoretical basis and method reference for the development of the new oral formulations of PSS and other marine polysaccharide drugs.