Abstract
The present work evaluates for the first time the use of urea-crosslinked hyaluronic acid (HA-CL), a novel derivative of native hyaluronic acid (HA), to produce microspheres (MS) by emulsification-solvent evaporation, for dermal delivery of sodium ascorbyl phosphate (SAP). As the term of comparison, HA MS were prepared. A pre-formulation study—investigation of the effects of polymers solutions properties (pH, viscosity) and working conditions—led to the production of optimized HA-CL MS and HA-CL—SAP MS with: almost unimodal size distributions; mean diameter of 13.0 ± 0.7 and 9.9 ± 0.8 µm, respectively; spherical shape and rough surface; high yield, similar to HA MS and HA–SAP MS (≈ 85%). SAP was more efficiently encapsulated into HA-CL MS (78.8 ± 2.6%) compared to HA MS (69.7 ± 4.6%). Physical state, thermal properties, relative moisture stability of HA-CL MS and HA-CL–SAP MS were comparable to those of HA MS and HA–SAP MS. However, HA-CL–SAP MS exhibited an extended drug release compared to HA–SAP MS, despite the same kinetic mechanism—contemporaneous drug diffusion and polymer swelling/dissolution. Therefore, HA-CL formulation showed a greater potential as microcarrier (for encapsulation efficiency and release kinetic), that could be improved, in future, using suitable excipients.
Highlights
Hyaluronic acid (HA) is a naturally occurring glycosaminoglycan, pervasively diffused in the human body: it is found in the extracellular matrix, skin dermis, eye vitreous, hyaline cartilage, synovial fluid, and umbilical cord
The present study showed, for the first time and with a systematic approach, that hyaluronic acid (HA)-CL could be a promising biopolymer to prepare drug-loaded microspheres with a water-in-oil (w/o) emulsification solvent evaporation technique
Appropriate working conditions led to the production of HA crosslinked with urea (HA-CL) MS and HA-CL–sodium ascorbyl phosphate (SAP) MS characterized by almost unimodal size distributions (Span values lower than 3); mean diameter of 13.0 ± 0.7 and 9.9 ± 0.8 μm, respectively; spherical shape and rough surface; high yield—similar to that of HA MS and HA–SAP MS (≈ 85%)
Summary
Hyaluronic acid (HA) is a naturally occurring glycosaminoglycan, pervasively diffused in the human body: it is found in the extracellular matrix, skin dermis, eye vitreous, hyaline cartilage, synovial fluid, and umbilical cord. The aim is to obtain cross-polymers that can act as multifunctional molecules able to deliver active ingredients and to exert, at the same time, a health action [1] Toward this end, we are investigating the possible pharmaceutical, cosmetic, and aesthetic applications of the new HA crosslinked with urea (HA-CL) [9,16,17,18]. HA-CL is a recently patented biocompatible and biodegradable polymer, provided with greater consistency and bioactivity with respect to native HA [9,16,18] This is due to hyaluronan crosslinking with urea, a molecule naturally present in the human body and employed as active substance. All the properties of SAP-loaded as well as unloaded MS of HA-CL were compared to SAP-loaded and unloaded MS of native HA (prepared as reference formulations)
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