Anales RANF

Juan Aparicio Blanco, Ignacio A. Romero, Jean P Benoit, Ana I. Torres Suárez @Real Academia Nacional de Farmacia. Spain 204 observe significant differences in the slopes (***: p<0.001). As shown in Table 2, the steepest slope was achieved for the Labrafac ® -Kolliphor ® HS15 tandem (b = 28.16), whereas the lowest value corresponded to the Labrafil ® -Kolliphor ® HS15 (b = 11.11). This difference in the slopes can be explained by the difference between the HLB values of the poly-ethoxylated surfactants and the triglycerides used as oily phase. The slopes follow this pattern: the closer the HLB affinity between the surfactant and the oily phase, the lower the slope of the linear plot. As a result, the size of nanocapsules can be precisely tailored to each therapeutic purpose within the range of 10- 100 nm. Importantly, since the univariate linear model has been established for surfactants and oily phases with different affinities, this tailoring can also be made in terms of adjusting the excipients to therapeutic needs. For example, solubility issues dictated by a given drug can presumably be addressed by changing the oily phase to one that fully solubilizes it. Alternatively, toxicological concerns related to a given surfactant can be overcome as nanocapsules of the same size can be obtained at a lower surfactant concentration by switching to an emulsifier with a lower HLB or by switching to an oily phase with a higher HLB. This can ultimately help increase the maximum tolerated dose. These latter cases are illustrated in Figure 1. For a given volume diameter, fixed in 30 nm, a formulation with a 0.752 ratio for the Labrafac ® WL1349-Kolliphor ® HS15 tandem can be used. However, according to our results, there are other alternatives. On the one hand, the Kolliphor ® HS15 with a HLB of 15 can be switched to another poly ethoxylated surfactant with a lower HLB (namely, Kolliphor ® ELP with a HLB of 13) and this change will imply a reduction in the surfactant amount, as it will require a higher oil/surfactant ratio (0.922). On the other hand, the oily phase can likewise be modified to ultimately reduce the amount of surfactant. The replacement of Labrafac ® WL1349 with a HLB of 1 by Labrafil ® M 1944 CS with a HLB of 9 will enable 30- nm sized nanocapsules to be obtained at an oil/surfactant ratio of 1.689, which halves the required amount of surfactant. This finding refutes the broadly-agreed requirement for a surfactant with an optimum HLB number for a given oily phase. The reason may lie in the fact that the HLB number concept, defined at 25ºC, only considers the surfactant molecule itself and overlooks the interactions with the aqueous and oily phases under the influence of external parameters. Furthermore, the linear univariate mathematical model serves to predict the particle size of nanocapsules prepared by other authors through not only the PIT method, but also through other phase inversion methods (Table 4). This unequivocally validates that the oil/surfactant mass ratio is the leading parameter that controls size distribution of final suspensions. Table 4: Parameters of the univariate linear regression between the average volume diameter and the oil/surfactant mass ratio for the different combinations tested. Preparation method R 2 Ref. Phase inversion temperature 0.9928 (46) Phase inversion temperature 0.9908 (47) Phase inversion temperature 1 (48) Phase inversion composition 0.99 (49) Phase inversion composition 0.9992 (50) Phase inversion composition 0.993 (51) Phase inversion composition 0.9789 (52) Altogether, these results serve to envisage LNCs prepared by the PIT method as promising carriers for the treatment of brain diseases following a disease-driven design. 3.2. Determination of BBB and glioma targeting ability of fluorescently-labeled LNCs Monodisperse LNCs with the Labrafac ® -Kolliphor ® HS15 tandem were prepared in two different sizes and loaded with fluorescent dyes for particle tracking purposes. Whereas the fluorescent dye DiO was encapsulated for in vitro experiments, we used the fluorescent dye DiD in in vivo experiments because it is excited and emits within the near-infrared window (namely, the wavelength range with the lowest absorption in tissue). Both kinds of fluorescently-labeled LNCs were functionalized with CBD to assess the potential of this cannabinoid to enhance the brain tumor targeting properties. High CBD adsorption efficiencies were achieved with this functionalization strategy (Table S1), which doubled those reported by Balzeau et al with a targeting peptide following a similar procedure (53). These results could be explained by the lower aqueous solubility of CBD than that of peptides, which eventually favors its