Chitosan-Folic Acid as system for site specific drug delivery

Antonio Di Martino

Tomas Bata University in Zlin Czech Republic

dimartino@ft.utb.cz

ChitosanObtained from Chitin by partial or total deacetylation

Deacetylation Chemical Enzimatic

Chitosan properties are related to Deacetylation Degree (DD) Molecular Weight (Mw)

Chitosan properties-I

Chemical properties

Cationic polyamine with low pKa High charge density at pH below 6.5 Forms gels with polyanions Adheres to negatively charged surfaces Chelates transition metals Amenable to chemical modification Both amino and hydroxyl groups can be selectively modified

CH2OH

HO

O

ONH-C-CH3

O

CH2OH

O

NH2O

NH2HO

CH2OH

O O

HO

x

Chitosan properties-IIBiological properties

Biocompatible Biodegradable Hemostatic Bacteriostatic Fungistatic Spermicidal Anti-cancer Anticholesterolemic

Folic Acid  Its biological importance is due to tetrahydrofolate and other derivatives after its

conversion to dihydrofolic acid 

Humans cannot synthesize folate de novo

It is essential for numerous bodily function synthesize DNA repair DNA methylate DNA aiding cell rapid division and growing cofactor in many biological reaction

Folic Acid receptors

Folate Receptor 1 –FOLR1 (adult) Folate Receptor 2 – FOLR2 (fetal) Folate Receptor 3 – FOLR3 RTBDN

FOLR1 FOLR2

Folate Receptors

FOLR1can be overexpressed by a number of epithelial-derived tumors including ovarian, breast, renal, lung, colorectal, and brain

FOLR2 was originally thought to exist only in placenta, but is also detected in spleen, bone marrow, and thymus

Chitosan – Folic Acid

+

Reaction is carried out in presence of EDC and NHS

Degree of functionalization is related with the Folic Acid concentration, the DD and Mw of Chitosan

Not necessary to obtain high degree of functionalization

Chitosan-Folic Acid Nanoparticles Nanoparticles can be prepared by Polyelectrolytes Complexation (PEC) Method

using Dextran Sulfate as polyanions

PEC is an easy, low cost and solvent free method to prepare nanoparticles in suspension

Particles dimension, PDI and z-potential can be changed according with the positive and negative charges ratio

Possibility to encapsulate more than one drug simultaneously

Possibility to encapsulate pDNA or linear DNA

Simultaneous encapsulation of DNA and drug is also possible

PolyElectrolyte Complexation method (PEC)

Polyanion solution

Step I: Add the solution containing drug to polyanion solution

Drug in solution

Drug + Polyanion in solution

Step II

Step II: Add drop-wise A to B under magnetic stirring

Drug + Polyanion in solution

(A)

CS-Folic Acid in solution(B)

Nanocomplex in suspension

Polycation Polyanion

Drug

Encapsulation Efficiency The Encapsulation Efficiency is related with

the positive- negative charges ratio

Chemical and physical properties of the drug in solution ( positive or negative charged, polar or apolar)

CS-Folic Acid – drug ratio (w/w) In case of DNA encapsulation is necessary to consider the

(N/P ratio) Encapsulation Efficiency can be calculate by

spectrophotometric methods ( UV-Vis)

Release Kinetic

• Generally, in this kind of systems the release rate is strictly influenced by the pH of the media

• Chitosan based system show prolonged release (even 2-3 weeks) at pH lower than 4.5. The release rate is related with the kind of drug and the encapsulation efficiency.

• An in initial burst often occurs, especially when high amount of drug is loaded

Conclusion

• Chitosan represents one of the more suitable biopolymer for controlled drug and gene delivery

• The presence of amino groups make chitosan easy to functionalize with different kind of molecules in order to improve the cell uptake

• Chitosan based nanoparticles can be prepared by solvent free methods

• Possibility to change size and z-potential of the nanoparticles• Possibility to encapsulate different kind of molecules by

electrostatic interactions• Release rate is pH and Temperature dependent