β-cyclodextrin dendritic derivatives as permeation mediators to enhance the in vitro albendazole cysticidal activity by the improvement of the diffusion component

Abstract

The improvement of permeation of drugs across parasites' membranes to promote their diffusion component represents a challenge to achieve better therapeutic effects, including the avoidance of drug resistance. In the context of medicinal chemistry, suitable structural modifications can be made, either on a drug or a nanocarrier, to trigger different mechanisms that promote the influx across membranes. This study aimed to demonstrate the potential of a set of dendritic derivatives of β-cyclodextrin (m2G, h2G, and m3G) as nanocarriers, based on their physicochemical and biological behavior in terms of (i) stability, monitored by ¹H NMR at pH 7 for seven days, (ii) ability to complex, and subsequently release around 50-80% of the cargo molecule (albendazole) in a biphasic medium and (iii) the absence of in vitro cysticidal effect in cysticercus cultures. The albendazole/nanocarrier inclusion complexes (ICs) were proved in the T. crassiceps model. According to the EC₅₀ values related to the cysticidal activity of albendazole, either free or complexed, the potency of this drug in the ICs experienced a significant increase, which may be attributed to the enhancement of its solubility but also to a better permeation mediated by the amphiphilic dendritic moieties, which ultimately positively impacts the diffusion of this drug through the tegument of the cysticerci. Additional considerations akin to synthetic ease of the dendritic nanocarriers, and production cost, along with the obtained outcomes, allowed us to place m2G followed by m3G as the best options to be considered for further in vivo assays.

Fig. 1. Three nanocarriers based on the primary face substitution of βCD with polyester dendrons. Mono-substitution-second generation dendron (m2G), hepta-substitution-second generation dendron (h2G), mono-substitution-third generation dendron (m3G).

Fig. 2. Stability study at physiological conditions. ¹H NMR spectra of m2G, m3G and h2G in DMSO-d₆. Comparison between the initial and final time (7 days).

Fig. 3. ¹H NMR spectra in DMSO-d₆ : D₂O (3 : 1) of ABZ in ICs with m2G (ABZ-m2G), m3G (ABZ-m3G) and h2G (ABZ-h2G).

Fig. 4. Release profiles by extraction experiments over time of ABZ on a biphasic medium (octanol–water). Each point represents the mean of percentage of ABZ found in the organic phase ±SD n = 3.

Fig. 5. ABZ diffusion to vesicular fluid of Taenia crassiceps cysts (percentage of ABZ found in vesicular fluid ±SD) after in vitro exposure to: free ABZ (black bars) and ABZ-ICs (purple, yellow and green bars). n = 3. *p < 0.05 against free ABZ. #p > 0.05 between dendritic nanocarriers.

Fig. 6. Morphological appearance of T. crassiceps cysts after in vitro treatments. (A) control group (0.19% DMSO in DMEM), (B) m2G dendritic nanocarrier (7.24 μM) and (C) ABZ (0.45 μM). Bars represent 3 mm.

Fig. 7. Cysticidal activity. Concentration-response curves of free ABZ and ABZ in ICs. Each point represents the mean ± SE. n = 6.

Fig. 8. Indirect carrier structure-ABZ activity relationship. Correlation at 8 h between diffusion and cysticidal activity of ABZ.