Novel carbon dot coated alginate beads with superior stability, swelling and pH responsive drug delivery

Novel carbon dot coated alginate beads (CA-CD) exhibiting superior stability and swelling properties have been successfully prepared. CA-CD show exceptional stability in ambient condition and are stable at room atmosphere and temperature even after 60 days. Moreover, CA-CD show excessive swelling in comparison to calcium alginate (CA) beads. The beads were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and optical microscopy. The CA and CA-CD beads were investigated for their use as pH dependent sustained drug delivery vehicles taking tetracycline (TC) and tetracycline associated with beta-cyclodextrin (beta-TC) as model drug systems. It was observed that TC loading was 35% and 77% with CA and CA-CD, respectively. Tetracycline associated with beta-cyclodextrin (beta-TC) shows 48% loading for CA and much greater loading (as high as 90%) for CA-CD. At pH 1, CA-CD and CA beads show maximum drug release with TC cumulative release of 70% and 37% at 96 h, respectively. However, the delivery rates at pH 1 were slower in case of tetracycline associated with beta-cyclodextrin (beta-TC) loading showing 61% release for CA-CD and 22% for CA after 96 h. Thus, CA-CD can be suitably used as an effective drug delivery vehicle with maximum release obtained at pH 1 emphasizing its use in the gastrointestinal tract where pH is low. Also, the use of beta-cyclodextrin with the drug as an inclusion complex renders the CA and CA-CD beads useful for slow and long-term drug administration.