Investigation on the Interaction of Hydroxyethyl Starch 130/0.4 (Voluven) and Serum Albumin for Pharmacokinetic and Toxicological Implications

Effect of hydroxyethyl starch on drug stability and release of semaglutide in PLGA microspheres

The degradation of peptide drugs limits the application of peptide drug microspheres. Structural changes of peptides at the water-oil interface and the destruction of their spatial structure in the complex microenvironment during polymer degradation can affect drug release and in vivo biological activity. This study demonstrates that adding hydroxyethyl starch (HES) to the internal aqueous phase (W1) significantly enhances the stability of semaglutide and optimizes its release behavior in PLGA microspheres. The results showed that this improvement was due to a spontaneous exothermic reaction (ΔH = -132.20 kJ mol-1) facilitated by hydrogen bonds. Incorporating HES into the internal aqueous phase using the water-in-oil-in-water (W1/O/W2) emulsion method yielded PLGA microspheres with a high encapsulation rate of 94.38 %. Moreover, microspheres with HES demonstrated well-controlled drug release over 44 days, unlike the slower and incomplete release in microspheres without HES. The optimized h-MG2 formulation achieved a more complete drug release (83.23 %) and prevented 30.65 % of drug loss compared to the HES-free microspheres within the same period. Additionally, the optimized semaglutide microspheres provided nearly three weeks of glycemic control with adequate safety. In conclusion, adding HES to the internal aqueous phase improved the in-situ drug stability and release behavior of semaglutide-loaded PLGA microspheres, effectively increasing the peptide drug payload in PLGA microspheres.

Progress and prospects of polysaccharide-based nanocarriers for oral delivery of proteins/peptides

The oral route has long been recognized as the most preferred route for drug delivery as it offers high patient compliance and requires minimal expertise. Unlike small molecule drugs, the harsh environment of the gastrointestinal tract and low permeability across the intestinal epithelium make oral delivery extremely ineffective for macromolecules. Accordingly, delivery systems that are rationally constructed with suitable materials to overcome barriers to oral delivery are exceptionally promising. Among the most ideal materials are polysaccharides. Depending on the interaction between polysaccharides and proteins, the thermodynamic loading and release of proteins in the aqueous phase can be realized. Specific polysaccharides (dextran, chitosan, alginate, cellulose, etc.) endow systems with functional properties, including muco-adhesiveness, pH-responsiveness, and prevention of enzymatic degradation. Furthermore, multiple groups in polysaccharides can be modified, which gives them a variety of properties and enables them to suit specific needs. This review provides an overview of different types of polysaccharide-based nanocarriers based on different kinds of interaction forces and the influencing factors in the construction of polysaccharide-based nanocarriers. Strategies of polysaccharide-based nanocarriers to improve the bioavailability of orally administered proteins/peptides were described. Additionally, current restrictions and future trends of polysaccharide-based nanocarriers for oral delivery of proteins/peptides were also covered.

Asymmetric polymersomes, from the formation of asymmetric membranes to the application on drug delivery

Nano drug delivery systems have attracted researchers' growing attention and are gradually emerging into the public views. More and more nano-formulations are being approved for marketing or clinical use, representing the field's booming development. Copolymer self-assembly systems such as micelles, nanoparticles, polymersomes occupy a prominent position in the field of nano-drug delivery carriers. Among them, polymersomes, unlike micelles or nanoparticles, resemble liposomes' structure and possess large internal hollow hydrophilic reservoirs, allowing them to carry hydrophilic drugs. Nevertheless, their insufficient drug loading efficiency and unruly self-assembly morphology have somewhat constrained their applications. Especially for the delivery of biomacromolecule such as peptides, the encapsulation efficiency is always considered to be a formidable obstacle, even if the enormous hydrophilic core would render the polymersomes to have considerable potential in this regard. Reassuringly, the emergence of asymmetric polymersomes holds the prospect of solving this problem. With the development of synthetic technology and a deeper understanding of the self-assembly process, the asymmetric polymersomes which are with different inner and outer shell composition have been gradually recognized by researchers. It has made possible elevated drug loading, more controllable assembly processes and release performance. The internal hydrophilic blocks different from the outer shell could be engineered to have a more remarkable affinity to the cargos or could contain a non-watery aqueous phase to enable the thermodynamically preferred encapsulation of cargos, which would allow for a substantial improvement in drug encapsulation efficiency compared to the conventional approach. In this paper, we aim to deepen the understanding to asymmetric polymersomes and lay the foundation for the development of this field by describing four main elements: the mechanism of their preparation and asymmetric membrane formation process, the characterization of asymmetric membranes, the efficient drug loading, and the special stimulus-responsive release mechanism.