Abstract
A miscibility study between oppositely charged polyelectrolytes, namely hyaluronic acid and a lactose-modified chitosan, is here reported. Experimental variables such as polymers’ weight ratios, pH values, ionic strengths and hyaluronic acid molecular weights were considered. Transmittance analyses demonstrated the mutual solubility of the two biopolymers at a neutral pH. The onset of the liquid-liquid phase separation due to electrostatic interactions between the two polymers was detected at pH 4.5, and it was found to be affected by the overall ionic strength, the modality of mixing and the polymers’ weight ratio. Thorough Dynamic Light Scattering (DLS) measurements were performed to check the quality of the formed coacervates by investigating their dimensions, homogeneity and surface charge. The whole DLS results highlighted the influence of the hyaluronic acid molecular weight in affecting coacervates’ dispersity and size.
Highlights
The perfect balance between attractive and repulsive interactions among oppositely charged polyelectrolytes often results in the formation of a variety of complex structures possessing different physical-chemical and biological properties that potentially could be translated toward clinical applications [1,2].Concerning drug delivery systems, complex coacervation between oppositely charged polymers is an attractive method to encapsulate and subsequently vehiculate payload therapeutics [3]
A plethora of micro-/nano-structures assembled via complex coacervation are documented in the literature, for instance stimuli responsive nanocapsules made of alginate and chitosan [6,7] or those based on the interaction between chitosan and hyaluronic acid [8,9], polysaccharides and proteins [5,10,11,12], or simple coacervation involving a single polymer and a multivalent ion [13]
We investigated the role played by polymer mixing (CTL dropped into an HA90 solution during stirring - indicated as CTL/HA90 - and vice versa, i.e., HA90/CTL) and the final polymers’ weight fraction, indicated as reported as polymers’ weight fraction (rHA) for convenience
Summary
The perfect balance between attractive and repulsive interactions among oppositely charged polyelectrolytes often results in the formation of a variety of complex structures possessing different physical-chemical and biological properties that potentially could be translated toward clinical applications [1,2]. CTL is a lactose-derivative of chitosan showing an improved solubility at neutral pH [17] and an interesting bioactivity toward mammalian cells [18,19] This engineered polysaccharide behaves as a polycation in acidic conditions [17], as a result of which it is prone to promote electrostatic interactions with oppositely charged ions or macromolecules depending on the ionic strength [13,20,21,22]. Since experimental variables are expected to influence resulting colloids features with a potential impact on their final application, this contribution expands current knowledge on the CTL-HA system and provides key guidelines for assembling nano-networks to be used as carrier candidates in the Drug Delivery sector
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