Current studies indicate that homogenously deacetylated chitosans are substantially less prone to induce inflammatory responses.
See, D. Fong et. al., Biomaterials 129, 127-138, (2017) and Inflammation and cell toxicity, impact of chitosan acetylation pattern, (2018).
The fastest way of making a neutral solution of Viscosan is to dissolve it under acidic conditions, e.g. pH 4-5 and adjust to desired pH when a clear solution has formed.
The solubility is highest at a DD close to 50%. See references 1,2.
1. Sannan et. al., Makromol.Chem.177, 3589-3600 (1976)
2. M. Vårum et. al., Carbohydrate Polymers, 25, 65-70, (1994)
The solubility of Viscosan™ is a function of several parameters i.e. its molecular weight, degree of deacetylation, pH and buffer concentration. Generally speaking most Viscosan™ solutions (pH 7) can be made in concentrations exceeding 1% (w/w) and practically, if molecular weight is fairly low and if DD is close to 50% solutions up to approximately 5% (w/w) can be made.
A Viscosan™ solution is stable at neutral and alkaline pH. At low pH and at room temperature it will start to degrade (slowly), seen as a successive loss in viscosity.
The in vivo degradation is done by enzymes. Most important of these are by far Lysozyme but there are other chitin- and chitosanases contributing to some minor part5.
5. T. Kean and M. Thanou, Advanced Drug Delivery Reviews.,62, 3-11 (2010)
The higher the DD the slower the biodegradation. A 40% deacetylated Viscosan™ degrades much faster than a corresponding 70% deacetylated material6.
6. K-M Vårum et.al. Carbohydrate Research, 299, 99-101 (1997)
Yes, Viscosan™ in the form of a cross linked hydrogel has been clinically evaluated as an adjuvant in a vaccine trial. See: Evaluation of safety and efficacy as an adjuvant for the chitosan-based vaccine delivery vehicle ViscoGel in a single-blind randomised Phase I/IIa clinical trial4.
4. Neimert-Andersson T. et al. Vaccine. Nov 8;29(48):8965-73. (2011) doi: 10.1016/j.vaccine.2011.09.041.
A solution of Viscosan can most often be sterilized by autoclaving. Important is to use a short ramping time. When autoclaved a small reduction in viscosity is typically observed.
Alternatively, sterile filtration can sometimes be used. It depends on the concentration of the solution, its pH and the type of filter used.
Yes, there is a file ready for submission to the regulatory authorities (FDA/EMEA/NIHS)
Yes, please contact us for discussion.