Crosslinked palygorskite-chitosan beads as diclofenac carriers

Beads are versatile spherical drug delivery units that can be coated, filled into capsules or compressed as tablets to be orally administered. Crosslinking of chitosan (CS) and polyanions such as tripolyphosphate (TPP) results in beads with mechanical properties that could be improved by the addition of clay mineral particles to the bead network. Hybrid systems of palygorskite and chitosan have been shown to have advanced properties in biomedical applications as a result of the synergic effects of their combination. In this paper chitosan was intercalated with palygorskite (Pal) and the resultant hybrid was loaded with diclofenac, an anti-inflammatory drug. Chitosan (CS) beads crosslinked with sodium tripolyphosphate (TPP) were prepared and their properties compared to palygorskite/Chitosan (Pal/CS) beads. The synergic effects resulting from the clay/polymer hybrids were evaluated by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning transmission electron microscopy (SEM) and thermal analysis (thermogravimetric analysis, TGA, and differential scanning calorimetry, DSC). The results showed that chitosan and palygorskite interaction took place. Diclofenac sodium (DFNa) was used as model drug to reveal the effects of Pal within the bead structure. DFNa was successfully loaded into beads and FTIR analyses confirmed its presence. A drug release test was carried out in phosphate buffer medium (pH. 6.8). The results indicated that only 33% (w/w) of total drug was released from DFNa-Pal/CS compared to 66% (w/w) from DFNa-CS. The total amount of drug released fell significantly with the addition of palygorskite to the chitosan matrix. Pal/CS beads crosslinked with TPP were shown to be able of carrying diclofenac sodium, meaning they could possibly be used as drug carriers.