Counterion of Chitosan Influences Thermodynamics of Association of siRNA with a Chitosan-Based siRNA Carrier

Abstract

Purpose:The work aimed to compare quality of a siRNA carrier prepared with chitosan of two different sources having similar degree of deacetylation and molecular weights. Differences were analyzed from thermodynamic characteristics of interactions with siRNA. Methods: The siRNA carrier (chitosan-coated poly(isobutylcyanoacrylate) nanoparticles) was prepared with home-prepared, CS Lab , and commercial, CS Com , chitosans. Chitosan counterion was identified and chitosans CS Com mod1 and CS Com mod2 were obtained from CS Com exchanging counterion with that found on CS Lab . Carrier quality was checked considering the size, zeta potential and siRNA association capacity by gel electrophoresis. Thermodynamic parameters of interactions between siRNA and chitosans in solution or immobilized at the carrier surface were determined by (ITC). Results: CS Lab and CS Com mod2 having a high content of acetate counterion associated better siRNA than CS Com and CS Com mod1 which counterion included mainly chloride. ITC measurements indicated that siRNA interactions with chitosan and the siRNA carrier were driven by entropic phenomena including dehydration, but thermodynamic parameters of interactions clearly differed according to the nature of the counterion of chitosan. The influence of chitosan counterions was interpreted considering their different lyotropic character. Conclusion: Association of siRNA with our siRNA carrier was influenced by the nature of counterions associated with chitosan. Driven by entropic phenomena including dehydration, interactions were favored by acetate counterion. Although more work would be needed to decipher the influence of the counterion of chitosan during association with siRNA, it was pointed out as a new critical attribute of chitosan to consider while formulating siRNA carrier with this polysaccharide.

Nanoparticles facing the gut barrier: Retention or mucosal absorption? Mechanisms and dependency to nanoparticle characteristics

“…Chitosan was purified preparing a solution at 2 g in 50 cm 3 of hydrochloric solution 0.1M that was dialyzed (Spectra/Por ® membrane, MWCO 3 500g/mol) against 1 L of hydrochloric acid solution (0.1 N) twice for 1 h and once overnight. Purified chitosan was recovered after frozen at -20 °C by lyophilization in an Alpha 1-2 LD plus lyophilizator (Bioblock Scientific) for 24 h. This chitosan was associated with a chloride counter ion (13.9% in weight as determined by elemental analysis) (Zandanel et al, 2020). The degree of deacetylation was 92% as determined by RMN (Zandanel et al, 2020) The purified mucins from porcine stomach were used a model of mucins in the ITC experiments.…”

“…Purified chitosan was recovered after frozen at -20 °C by lyophilization in an Alpha 1-2 LD plus lyophilizator (Bioblock Scientific) for 24 h. This chitosan was associated with a chloride counter ion (13.9% in weight as determined by elemental analysis) (Zandanel et al, 2020). The degree of deacetylation was 92% as determined by RMN (Zandanel et al, 2020) The purified mucins from porcine stomach were used a model of mucins in the ITC experiments. The commercial preparation was dispersed in Milli-Q ® water at a concentration of 1g/L for 2 h at room temperature and frozen at -20°C as aliquots of 1 cm 3 for storage until use.…”

Fundamental and Practical Aspects in the Formulation of Colloidal Polyelectrolyte Complexes of Chitosan and siRNA

“…[98] When the ionization rate of chitosan is increased, either by lowering the pH or decreasing the DA, K increases too, which is expected for a complexation mechanism dominated by the electrostatics. [85] It was also shown that the siRNA sequence [8] and the nature of the counter ion associated with chitosan [105] can influence the binding affinity, which for the latter can be explained by considering the polyelectrolyte complexation as a kind of substitution reaction of counterions. [17] In general, there is a strong correlation between the binding constant and the encapsulation efficiency of siRNA in complexes.…”

Chitosan‐based biomaterials: From discovery to food application

“…Corresponding experiments showed that chitin is a nontoxic and degradable polymer, with a certain ability to inhibit the growth of microorganisms 40,41 . Chitosan not only has the excellent properties of chitin, but also has other characteristics, such as being a hemostatic agent, a detoxifying agent, and a biological carrier 42‐46 …”