Synthesis and Biopharmaceutical Characterization of Amphiphilic Squalenyl Derivative Based Versatile Drug Delivery Platform

Abstract

Limited drug loading capacity (LC), mostly below 5% w/w, is a significant drawback of nanoparticulate drug delivery systems (DDS). Squalenoylation technology, which employs bioconjugation of squalenyl moiety and drug, allows self-assemble of nanoparticles (NPs) in aqueous media with significantly high LC (>30% w/w). The synthesis and particle preparation of squalenoylated prodrugs are, however, not facile for molecules with multiple reactive groups. Taking a different approach, we describe the synthesis of amphiphilic squalenyl derivatives (SqDs) as well as the physicochemical and biopharmaceutical characterizations of their self-assembled NPs as DDSs. The SqDs included in this study are (i) cationic squalenyl diethanolamine (ii) PEGylated SqD (PEG 750 Da), (iii) PEGylated SqD (PEG 3,000 Da), and (iv) anionic squalenyl hydrogen sulfate. All four SqDs self-assemble into NPs in a size range from 100 to 200 nm in an aqueous solution. Furthermore, all NP derivatives demonstrate appropriate biocompatibility and adequate colloidal stability in physiological relevant pH environments. The mucoprotein binding of PEGylated NPs is reduced compared to the charged NPs. Most importantly, this technology allows excellent LC (at maximum of 45% w/w) of a wide range of multifunctional compounds, varying in physicochemical properties and molecular weight. Interestingly, the drug release profile can be tuned by different loading methods. In summary, the SqD-based NPs appear as versatile drug delivery platforms.

Tofacitinib Loaded Squalenyl Nanoparticles for Targeted Follicular Delivery in Inflammatory Skin Diseases

“…TFB-C was manufactured to enhance the water solubility of TFB and was in this study used to prepare an aqueous drug reference solution. SqD was synthesized as described previously [43,44]. Ammonium acetate (LC-MS grade) was purchased from Sigma-Aldrich, Munich, Germany.…”

“…Most importantly, such a high LC of TFB in SqD NPs enhanced the TFB solubility in phos-buffer up to 2 mg TFB/mL, which was around 40 times higher than the maximum solubility of TFB alone in the same buffer (47.9 ± 0.2 µg/mL). The negative zeta-potential of the drug-free SqD NPs (−54.5 ± 1.7 mV, Table 3) did not change upon drug loading (−59.9 ± 2.3 mV, Table 3), which led to the assumption that TFB might be loaded rather via hydrophobic than charged interactions into SqD NPs [44]. It is worth noting that the pH value plays a crucial role in the optimization of TFB loading.…”

“…TFB SqD NPs were prepared using free base TFB and anionic squalenyl derivative (SqD)-squalenyl hydrogen sulphate ( Figure 1)-whose detailed synthesis and characterization can be found in our previous work [43,44]. The optimal TFB SqD NPs were produced by solvent evaporation technique.…”

“…The anionic SqD (Figure 1) containing a hydrophilic hydrogen sulfate head-group and a hydrophobic squalenyl moiety potentially allows the loading of TFB (Figure 1) in both compartments via charged and hydrophobic interactions, respectively. We have previously reported the significant drug LC of SqD NPs yet also pointed out that the loading of small molecules-containing polar groups and having rather poor water-solubility-is challenging, only allowing e.g., the maximum LC at around 10% of a quorum sensing inhibitor [43] or at around 9% of Nile red [44]. In this study, it is surprising that the LC of TFB could be maximized at 20.1% ± 2.2%, with a corresponding EE at 19.8% ± 3.6%.…”

“…Recently, we have reported an alternative to the squalenoylation approach, in which we used amphiphilic squalenyl derivatives to formulate the surfactant-free self-assembled NPs allowing significantly high drug LC in both hydrophilic and hydrophobic compartments [42][43][44].…”