Title
Chemical modification of alginate with L-cysteine to extend its use in drug delivery systems
Authors
YUBEXI CORREA MARCANO and MARCOS A. SABINO G

Received It is an honor for us to contribute a small but valuable piece of our work to this special issue dedicated to the 70^th anniversary of Acad. Bogdan C. Simionescu. Congratulations on this 70^th anniversary and continued success.
Published Volume 52 Issue 7-8 July-August
Keywords alginic acid, L-cysteine, thiolated biopolymer, mucoadhesives, ionic gelation, nanoparticles

Abstract
In this research, alginic acid was chemically modified by coupling it with the amino acid L-cysteine to improve its solubility, biocompatibility and mucoadhesive properties, which allows expanding its use in pharmacological applications. L-Cysteine was grafted in different ratios (2:1, 1:1 and 2:3 molar ratios) and these alginate-L-cysteine conjugates were characterized by Infrared Spectroscopy (ATR-FTIR) and Nuclear Magnetic Resonance (1H-NMR). The concentration of the thiol group from the coupled cysteine was determined. The improvement in mucoadhesivity was demonstrated by mechanical tensile studies, and the conjugate with the ratio of 2:1 presented the highest adhesion capacity. From these modified biopolymers, micro/nanoparticles were synthesized by the ionic/microemulsion gelation method (Zn+2 divalent ion). Using Scanning Electron Microscopy (SEM), the morphology of the obtained micro and nanometric spherical particles was observed. The results indicated that thiolated alginate may have potential for use in drug delivery systems, especially in those where it is required to extend the residence time in the epithelial mucosa.