Nano-preparation Of 5-aminolevulinic Acid And Its Biological Application

5-aminolevulinic acid (ALA) is a natural amino acid, as one of second generation photosensitizers, ALA is widespread in agriculture and medical science.In this work, ALA was chemically synthesized with succinic acid mono-ester as monomer, ALA had a purity of 98.7% by recrystallization; Stability of ALA in aqueous solution was studied, and it was found that temperature, concentration and the PH of the solution influenced the degradation of ALA. ALA was unstable when in higher temperature and alkaline solution, an increased decomposition rate of ALA was shown when the temperature was over 37℃, at pH of 7 and 10, the ALA content declined by 50-60%. The instability was closely related to the concentration of ALA solution, the higher concentration, the stronger instability.We prepared size controllable PLGA nanoparticles(NPs) and PLGA-ALA NPs by electrospraying. SEM images showed that particles was well dispersed, having narrow size distribution. Parameters such like voltage, rate and concentration of solution had a great effect on the morphology and size of NPs; 200-1000nm PLGA-ALA NPs with different amounts of ALA was produced by adjusting the outer and inner flow rate ratio, the drug loading efficiency was determined by HPLC, which was 60-75%.FT-IR、 DSC/TGA curves illustrated that ALA was successfully encapsulated in PLGA NPs, besides, PLGA after electrosprayed proved to be less crystallized. The release profiles of ALA from NPs showed a shorter time of burst release and a delayed release of ALA, thus improving the bioavailability of drug.PLGA-ALA NPs was used for the PDT treatment in HSC-3 cells. It was found that exposing light dose、incubation time and concentration of ALA greatly affected the cytotoxicity against HSC-3 cells; PLGA-ALA NPs had certain cytotoxicity against HSC-3 cells, causing 25%-40% cell death when cells were incubated with 0.5-1mM PLGA-ALA solutions, however, because of the delayed release of ALA, groups with PLGA-ALA NPs showed less cytotoxicity than that of the same amount of pure ALA, and the cytotoxicity against HSC-3 cells was directly induced by the ROS from the fluorescent kinetic of intracellular PpIX and ROS; multiple PDT was performed on HSC-3 cell, cell viability decreased by 20-21%, predicting that multiple PDT could be used to enhance the cytotoxicity of PLGA-ALA NPs against HSC-3 cells.