Is Viscosan™ less inflammatory than other chitosans?

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).

How do I best dissolve Viscosan™ to make a Viscosan™ solution having a neutral or alkaline pH?

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.

At what degree of deacetylation (DD) is the solubility of Viscosan™ highest at neutral pH?

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)

In what concentrations can I use Viscosan™ at neutral pH?

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.

Is the stability of a solution of Viscosan™ sensitive to changes in pH?

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.

How is Viscosan™ degraded in vivo?

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)

What quality of Viscosan™ should I use if I want a slower biodegradation?

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 Carbohydrate Research, 299, 99-101 (1997)

Has Viscosan™ been tested in humans?

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.

Can I sterilize a solution of Viscosan™, if so, how?

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.

Is there a Quality Data File (QDF) for Viscosan™?

Yes, there is a file ready for submission to the regulatory authorities (FDA/EMEA/NIHS)

Can Flexichem scale up and deliver Viscosan™ in large quantities?

Yes, please contact us for discussion.