Different strategies have been exploited with interesting results, for example, in the preparation of bioconjugates obtained by covalently Binimetinib linking HA to a cytotoxic drug such as, for example paclitaxel [39, 40] or doxorubicin [41, 42]. These topics are out of the scope of this paper where only strategies consisting in the design of HA decorated nanosystems will be discussed in depth. 3. Chemical Conjugation of HA to Lipid-Based Nanocarriers Different approaches can be used to bind HA to the lipid-based nanocarriers, depending on the molecular weight of the HA as well as on the need to start from preformed nanocarriers

or from Inhibitors,research,lifescience,medical pure lipids that will be then used to prepare particles. HA binding to preformed nanocarriers was the firstly used method [43] and offers the advantage to conjugate the HA only on the external surface of the particle. Inhibitors,research,lifescience,medical Of course, this approach makes all targets difficult the control of the density of attachment of HA on the carrier surface. Moreover, the lower specificity of the linkage, due to the possibility to bind different amino groups, results in a consequent multipoint attachment of the polymer on the nanocarrier that is then difficult to characterize. Alternatively, HA can be previously conjugated

to a pure lipid and then added in the lipid mixture during the preparation of the nanoparticles. Inhibitors,research,lifescience,medical This procedure permits the introduction of a controlled amount of HA on nanocarriers, but could require a more elaborated synthetic method. 3.1. HA Binding to Preformed Nanocarrier Inhibitors,research,lifescience,medical High molecular weight (HMW) HA was attached to the surface of preformed liposomes through amidation reaction between the aminoreactive group of a lipid on the

liposome surface, generally a phosphatidylethanolamine (PE), and HA glucuronic carboxylate (Figure 2) [13, 14, 43]. The amidation reaction was performed preactivating HA by incubation with the Inhibitors,research,lifescience,medical 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) condensing agent in acidic medium and then adding the activated HA to the nanocarrier suspension in a basic Brefeldin_A medium. Elimination of the excess of reagent and reaction byproducts was obtained by centrifugation and repeated washing. Figure 2 Strategies to prepare HA-coated nanocarriers. A schematic representation. (a) HA binding to preformed nanocarrier. Amidation reaction between HA-carboxyl group and aminoreactive group of lipid on the liposome surface. (b) Synthesis of HA-PE conjugates … 3.2. Preparation of HA-PE Preformed Conjugates HA conjugation to the lipid before nanocarrier preparation was carried out with both high and low molecular weight (LMW) polymers [12, 19]. In all cases, HA reacted with an aminoreactive group present on the lipid that was PE, also in this case (Figure 2). Two different conjugation methods have been proposed depending on the HA molecular weight.