EFFECT OF THE PARAMETERS OF THE NANOPARTICULATE FORM OF DOXORUBICIN BASED ON PLGA ON THE DISTRIBUTION BETWEEN HUMAN BLOOD PLASMA AND RED BLOOD CELLS

Relevance. One of the features of the pharmacokinetics of nanoparticle-based drug formulations is the different distribution of free and carrier-bound drugs (nanoparticles, liposomes) between plasma and blood cells. Aim. Evaluation of in vitro binding of doxorubicin-loaded nanoparticles (NPs) based on a copolymer of lactic and glycolic acids (PLGA) modified with poloxamer 188 (Dox-PLGA) to human red blood cells at a concentration of 10-100 μg/ml and the influence of physicochemical parameters of NPs on their binding to red blood cells. Material and methods. Dox-PLGA NPs were obtained by a "double emulsion" method. A 1% PVA solutions in phosphate buffer at pH 7.4 (Dox-PLGA/7.4) and 6.4 (Dox-PLGA/6.4) were used as the external aqueous phase. The purified Dox-PLGA/7.4(G-25) and Dox-PLGA/6.4(G-25) NPs were obtained by separation of the free fraction of doxorubicin (non-nanoparticle-bound) by gel filtration. The kinetics of doxorubicin release from NPs in vitro was determined in a 1% solution of poloxamer 188. To assess the binding of the NPs to red blood cells, the distribution coefficients KRBC/Plasma (red blood cells – plasma) and KBlood/Plasma (whole blood – plasma) were calculated after incubation in whole blood within 5, 15 and 30 minutes. The doxo-rubicin content in plasma was estimated by HPLC. Results. Compared to the Dox-PLGA/7.4 NPs (average size 114±1 nm), the Dox-PLGA/6.4 NPs (average size 142±2 nm) had a lower encapsulation efficiency (79.7±1.1% vs 91.0±0.7%, respectively) and a higher release rate of doxorubicin in vitro. Based on the calculated KBlood/Plasma values, the total amount of doxorubicin bound to red blood cells after 5 minutes of incubation was ~ 33% for both nanoparticulate formulations and free doxorubicin (control) over the entire concentration range. The equilibrium degree of binding (after 15 minutes of incubation) was 58-63% for free doxorubicin, 57-58% for Dox-PLGA/6.4 and 46-49% PLGA/7.4. The Dox-PLGA/6.4(G-25) NPs had the lowest equilibrium degree of binding to red blood cells (~ 34%). Conclusion. Binding of the nanoparticle-bound doxorubicin (Dox-PLGA) to human red blood cells evaluated in vitro in the concentration range of 10-100 μg/ml is lower as compared with free doxorubicin. The NPs with a higher encapsulation efficiency and loading of doxorubicin exhibit lower distribution coefficients of doxorubicin between red blood cells and blood plasma (KBlood/Plasma and KRBC/Plasma).