Relationship Between Particle And Biological Properties Of Emulsion-Templated, Freeze-Dried Lopinavir Nanoparticle Dispersions

Abstract

Background Nanomedicine has the potential to enhance bioavailability and delivery of low-solubility compounds to sanctuary sites. Lopinavir (LPV) is a protease inhibitor (PI) with low bioavailability (<2%) that requires boosting with ritonavir. We assessed relationships between size (z-average), surface charge (zeta potential), and polydispersity with cytotoxicity, cellular accumulation ratio (CAR), and transcellular permeability of a LPV nanodispersion library. Methods Seventy-four dispersions containing 0.1 micro Ci 3H-LPV were generated. Cellular accumulation in lymphocytes (CEM), monocytes (THP1), monocyte-derived macrophages (ATHP1), hepatic (HepG2), and intestinal (Caco-2) cells as well as apical to basolateral (A>B) permeability across Caco-2 monolayers was determined. Data were log transformed and models to describe relationships between particle properties and biological characteristics were constructed using multiple linear regression. Results Median (range) z-average, polydispersity, and zeta potential were 436 (184 to 3145) nm, 0.3 (0.1 to 0.9), and –3.7 (–56.7 to 39.7) mV, respectively. Dispersions exhibiting higher and lower values than aqueous solutions were observed for all biological characteristics. Cytotoxicity of dispersions was lower in all cells compared to aqueous LPV and predictable from models containing z-average and zeta potential (e.g., r = 0.47; p = 0.001 for CEM). A number of dispersions exhibited higher CAR than for aqueous LPV. E.g., median (range) CAR was 17.0 (2.8 to 105.1) in CEM compared to 13.1 for aqueous LPV. In HepG2 (r = –0.38), Caco-2 (r = –0.39), THP1 (r = –0.14), and CEM (r = –0.09) inverse correlations with polydispersity were observed but in phagocytic ATHP1 cells a direct relationship was evident (r = 0.28). In all cells, CAR was predictable from models containing z-average and polydispersity (e.g., r = 0.41; p = 0.006 for Caco-2). The rate of A>B permeation across Caco-2 cells was 6.3 (1.8 to 20.7)%/h compared to 2.5%/h for aqueous LPV but no relationship with particle properties was seen. Conclusions Understanding relationships between particle and biological properties will facilitate generation of effective nanomedicines. We have generated some LPV nanodispersions with greatly enhanced cellular accumulation and transcellular permeability but reduced cytotoxicity. Following careful safety evaluation, the ability to nano-enhance PI could increase bioavailability and thereby alter the requirement for boosting