Study On The Regularity In Preparing PLGA Nanoparticles Loading Different Drugs

Because of their advantages, nanoparticles (NP) are being studied widely withbiocompatible and biodegradable polymers as the carrier material. Some problemsand limitation emerged to NP. First, the entrapment rates (ER), drug loading (DL)and drug release in vitro are different. Second, the quality of NP is affected by thecarder material, preparation method and drug. At present, there is no report aboutthe systemic study on the relation between the parameters and the result.In this paper, PLGA was chosen as the carrier material. Colchicine (Col),Tetramethylpyrazine (TMP), TanshinoneⅡ_A (T_A) and Curcumin (Cur) were chosenas model drugs. Nanoprecipitation method and emulsion evaporation method wereused as the preparation methods. The ER, DL and Recovery of drug (R) were usedas the main guiders to optimize NP's formulations in order to find the effect of allkinds of parameters on the NP's preparation. After prepared with the optimumtechnology, NP were characterized by the ER, DL, R, particle size and itsdistribution, Zeta potential, morphology, crystallinity and release in vitro. Accordingto the test condition and the result, the difference among NP was analyzed for thesake of finding the inner regularity in preparing drug-loaded NP.Singe factor test was used to optimize the formulation of Col-PLGA-NP. Intwo preparation methods, the type and concentration of stabilizers, the concentrationof PLGA and Col and the volume ratio of the water phase to the organic phase wereall ineffective for the entrapment of Col. The ER of Col-PLGA-NP prepared bynanoprecipitation and emulsion evaporation methods were 0.93% and 1.24%respectively, the DL were 0.10% and 0.25%, the R were 102.86% and 101.52%, theparticle size were 258 nm and 205 nm, the Zeta potential were -0.0548 mV and -0.0654 mV, and the entrapped drug contents were 1.91μg and 10.07μg. Thequality of NP prepared by emulsion evaporation method was better than that of NPprepared by nanoprecipitation method.Singe factor test and orthogonal design test were used to optimize theformulation of TMP-PLGA-NP. Increasing the amount of TMP and/or decreasingthe solubility of TMP in water phase could improve the entrapped drug content. TheER of TMP-PLGA-NP prepared by nanoprecipitation and emulsion evaporationmethods were 0.07% and 0.59% respectively, the DL were 0.18% and 0.30%, the Rwere 85.56% and 83.40%, the particle size were 255 nm and 186 nm, the Zetapotential were -0.0791 mV and 0.102 mV, and the entrapped drug contents were3.59μg and 29.84μg. The quality of NP prepared by emulsion evaporation methodwas better than that of NP prepared by nanoprecipitation method. The release invitro test showed that TMP could not have sustained release from theTMP-PLGA-NP.Singe factor test and central composite design test were used to optimize theformulation of T_A-PLGA-NP. When nanoprecipitation method was used, the factorthat had the maximal effect on the result was the concentration of the stabilizer withwhich the result has a positive correlation. When emulsion evaporation method wasused, the factor that had the maximal effect on the result was the drug concentrationin the organic phase with which the result has a negative correlation. The ER ofT_A-PLGA-NP prepared by nanoprecipittation and emulsion evaporation methodswere 95.49% and 87.99% respectively, the DL were 2.03% and 0.16%, the R were38.42% and 17.59%, the particle size were 225 nm and 183 nm, the Zeta potentialwere -3.03 mV and -5.58 mV, and the entrapped drug contents were 27.52μg and12.38μg. The quality of NP prepared by nanoprecipitation method was better thanthat of NP prepared by emulsion evaporation method. The release in vitro testshowed that TMP had good sustained release from the T_A-PLGA-NP prepared bytwo methods.Singe factor test and orthogonal design test were used to optimize theformulation of Cur-PLGA-NP. When nanoprecipitation method was used, the mostimportant factors were the concentration of PLGA with which the ER had a positivecorrelation and the DL had a negative correlation and the drug concentration withwhich the R had a negative correlation. When emulsion evaporation method wasused, the most important factors were the drug concentration with which the ER had a negative correlation and the DL had a positive correlation and the stabilizerconcentration with which the R had a positive correlation. The ER of Cur-PLGA-NPprepared by nanoprecipitation and emulsion evaporation methods were 45.99% and72.90% respectively, the DL were 1.83% and 5.00%, the R were 80.21% and90.23%, the particle size were 160 nm and 172 nm, the Zeta potential were -0.0191mV and -0.449 mV, and the entrapped drug contents were 18.44μg and 98.67μg.The quality of NP prepared by emulsion evaporation method was better than that ofNP prepared by nanoprecipitation method. The release in vitro test showed that Curhad good sustained release from the Cur-PLGA-NP prepared by two methods.For nanoprecipitation method, the entrapped efficiency had a negativecorrelation with the drug solubility in the water phase and had a positive correlationwith the speed of separating out when drugs encountered the water phase. The orderof the solubility in water phase of the four drugs was Col＞TMP＞Cur＞T_A, the orderof the speed of separating out was T_A＞Cur＞TMP＞Col, and the order of theentrapped efficiency was T_A＞Cur＞TMP＞Col. For those drugs whose solubilitycould not be increased by the stabilizer, their entrapped efficiency could beimproved through enhancing the stabilizer concentration. For those drugs whosesolubility could be increased by the stabilizer, their entrapped efficiency could beimproved through decreasing the drug concentration and enhancing the PLGAconcentration. The particle size was relational with the concentration of PLGA andstabilizer and was almost not affected by the type of drugs in nanoprecipitationmethod. Both the drug peaks and the PLGA peaks disappeared in the DSC curve offour drugs loaded NP prepared by nanoprecipitation method. There were only thestabilizers peaks. The result showed that drugs were entrapped by a similar modethat was not affected by the drug and the stabilizers. The release in vitro was similarand was not affected by the type of drugs for lipophilic drugs loaded NP prepared bynanoprecipitation method.For emulsion evaporation method, the entrapped efficiency had a negativecorrelation with the speed of separating out when drugs encountered the water phase.Col and TMP didn't separate out when encountering the water, so their entrappedefficiency was bad. If the amount of TMP was more than the solubility in the water,TMP would separate out and the entrapped efficiency was improved. The separatingspeed of T_A was faster than that of Cur, so the entrapped efficiency of Cur was betterthan that of T_A. The particle size was not relational with the concentration of PLGA and stabilizer and was almost not affected by the type of drugs in emulsionevaporation method. Most drug peaks disappeared and the PLGA and stabilizerspeaks all existed in the DSC curve of four drugs loaded NP prepared by emulsionevaporation method. The result showed that drugs were entrapped by a similar modeon which the type of drugs had little effect. The release in vitro was relational withthe type of the lipophilic drugs.The drug loading efficiency was found to be lower for the hydrophilic drugsthan lipophilic drugs either using the nanoprecipitation method or using theemulsion evaporation method. The entrapped efficiency was relational with the usedmethod for lipophilic drugs. For drugs whose solubility could not be increased bythe stabilizer, the nanoprecipitation method was suitable. For drugs whose solubilitycould be increased by the stabilizer, the emulsion evaporation method was suitable.The adsorbed drug in NP prepared by nanoprecipitation method was more than thatin NP prepared by emulsion evaporation method because the former release speedwas faster than the latter in the initial stage.The research results showed that the drugs solubility and the preparationmethod were the most important factors in preparing drug loaded PLGA-NP. Thedrugs had better to be lipophilic and not to be hydrophilic because the hydrophilicdrugs couldn't have sustained release from their PLGA-NP.This paper did systemic study on the drug loaded PLGA-NP by using differentpreparation methods and choosing different drugs. The work enriches the content ofNP as the drug delivery system. The regularity educed from our work provides thetheoretic basis and reference for the future study on drug loaded NP. We gain theexpected ends.