Preparation And Evaluation Of PEG-PCL Loading Baicalin Nano-Drug Delivery Systems

Baicalin is a major flavonoid component extracted from the rhizomes of Scutellaria baicalensis Georgi.It has multiple pharmacological activities such as anti-inflammatory,antibacterial,antioxidant,antiallergic,anti-tumor.However,the poor water solubility of baicalin results in low bioavailability,in addition to instablity and easy to degrad into alkaline solution,which limits its clinical application.Theamphiphilicblockpolymerpolyethyleneglycol-polycaprolactone?PEG-PCL?is biocompatible and can self-assemble into different structures polymer nano-carriers which can solve the problem of poor water solubility and poor stability of the drug.In addition,the sustained release and EPR effect of the carries could reduce toxicity of drug and increase efficiency.In this study,baicalin was used as a model drug,polymer PEG-PCL with two molecular weights as carriers,nano drug delivery systems?BAN-PEG-PCL-NPs?were prepared.The aim was to improve the solubility and stability of baicalin.The details are as follows:1.BAN-PEG-PCL-NPs were prepared by dialysis method,which utilized the interaction of baicalin with the hydrophobic chain to physically load the baicalin into the nanoparticles.Firstly,by comparing the particle size and appearance of nanoparticles prepared by 10000 and 7500 molecular weight PEG-PCL,it was found that BAN-PEG₅₀₀₀-PCL₅₀₀₀-NPs prepared by 10000-molecular weight PEG-PCL had an uniform particle size and was more stable.Then the orthogonal experiment were performed and evaluated by the partical size,entrapment efficiency and drug loading.The optimal formulation was determined as 3:10 ratio of baicain to PEG-PCL?w/w?,8 g/L?w/v?carries concentration,5 mL initial water volume,25?dialysis temperature.BAN-PEG₅₀₀₀-PCL₅₀₀₀-NPs prepared with the optimal formulation were dispersed evenly in water and had a particle size of 48.2±2.4nm,polydispersity index?PDI?of 0.115±0.01,Zeta potential of-6.08mV,entrapment efficiency?EE%?of62.34%and drug loading of 15.8%.The solubility of BAN-PEG₅₀₀₀-PCL₅₀₀₀-NPs increased 22 times in water compared with free BAN.The morphology of nanoparticles was nearly spherical by oil microscopy and had a transparent cavity in the middle.Differential scanning calorimetry?DSC?showed that baicalin was successfully loaded and existed as an amorphous form.BAN-PEG₅₀₀₀-PCL₅₀₀₀-NP_S had a sustained release with a cumulative release of 55.3%within 48 h,which fitted to the Ritger–Peppas modal.2.Membrane hydration method was performed to load baicalin in PEG-PCL delivery system.Baicalin in phosphate-buffered saline was used as hydration solution,and then loaded into the system.The problem of poor water solubility of baicalin was avoided.Two molecular weights,10000and 7500,of PEG-PCL,was used to prepare the drug delivery system,and it was found that BAN-PEG₂₅₀₀-PCL₅₀₀₀-NPs had an uniform particle size and an obvious opalescence.So the orthogonal experiment was done to optimize the formulation of BAN-PEG₂₅₀₀-PCL₅₀₀₀-NPs by the partical size,entrapment efficiency and drug loading.The optimal formulation was 3:8 ratio of baicain to PEG-PCL?w/w?,5.33 g/L?w/v?carries concentration,5 mL hydration volume,and25?hydrationtemperature.Thecharacteristicsof BAN-PEG₂₅₀₀-PCL₅₀₀₀-NPs were particle size as 108.3±2.23nm,polydispersity index?PDI?as 0.168±0.01,zeta potential as-2.52mV,entrapment efficiency?EE?as 77.23%and drug loading as 22.4%.The nanoparticles were observed using a microscopy,which were nearly spherical and has aa transparent cavity in the middle.The Fourier transform infrared spectroscopy?FT-IR?analysis confirmed the formation of the drug delivery system and indicated that PEG-PCL had been changed from crystalline to amorphous status due to the interaction between drugs and carrires.It is the system isolated baicalin from the external environment that contributed to the remarkably stabler status of baicalin loaded in PEG-PCL than in PBS buffer.The logP value of BAN-PEG₂₅₀₀-PCL₅₀₀₀-NPs was-0.889 as free baicalin was-1.500.It was inferred baicalin in nano system improved the biofilm permeability compared to the freebaicalin.The results of drug release in vitro showed that BAN-PEG₂₅₀₀-PCL₅₀₀₀-NPs had an obvious sustained release compared to control groups.3.The antibacterial and anti-tumor bioactivity of the baicalin-loaded PEG-PCL nano drug delivery systems were studied in vitro against Staphylococcus aureus and breastcancercell?MCF-7?.BAN-PEG₅₀₀₀-PCL₅₀₀₀-NPsand BAN-PEG₂₅₀₀-PCL₅₀₀₀-NPs maintained the antibacterial activity as baicalin.At the high concentration?4000?g/mL?,the nanoparticles exhibited a stronger activity due to its sustained release.Cellular uptake experiments showed that the uptake amount of drug delivery systems by MCF-7 cells was higher than that of small-molecule phosphors within 4 hours.The anti-tumor activity assay showed that PEG-PCL was not toxic to MCF-7 cell,while the inhibition of MCF-7 cells by all samples had a time-and concentration-dependentmanner.BAN-PEG₅₀₀₀-PCL₅₀₀₀-NPsand BAN-PEG₂₅₀₀-PCL₅₀₀₀-NPs showed higher cytotoxicity than free BAN at the concentration of 2000?g/mL.The above results indicated that the baicalin PEG-PCL nano drug delivery systems enhanced the antibacterial and antitumor activity of baicalin.In conclusion,the baicalin-loaded PEG-PCL nano drug delivery systems constructed improved the water solubility of baicalin,enhances the transmembrane properties of the drug,and can be uptaken in large quantities by cells to improve the bioavailability of drugs.It should be a potential clinical application in future.