One of my M Pharm students is working with natural gum for preparation of microspheres. When we were searching the literature, we came across the paper published in AAPS PharmSciTech (2006; 7 (3) Article 74) entitled "Cross-Linked Guar Gum Microspheres: A Viable Approach for Improved Delivery of Anticancer Drugs for the Treatment of Colorectal Cancer"
In this paper, the method of preparation of microspheres is as described below:
Drug-loaded guar gum microspheres were prepared by the emulsification method.20 An aqueous dispersion of guar gum (40 g) containing 2% wt/wt of guar gum (an accurately weighed amount of gum was dispersed in a specified volume of cold water containing the drug and allowed to swell for 2 hours) was dispersed in 100 g of castor oil containing 3 g of Span 80 using a mechanical stirrer at 4000 rpm. After complete mixing, 0.2 mL of concentrated sulfuric acid and 1.5 mL of glutaraldehyde were added to the dispersion, followed by stirring at a constant speed for 4 hours at 50-C. The microspheres formed were collected by sedimentation followed by decantation of oil, then washed with several fractions of isopropyl alcohol. The final preparation was a free-flowing powder consisting of spherical micron-sized particles.
What is the reason for the addition of sulfuric acid?
Gluteraldehyde is cross linking agent and it requires acidic condition for cross linking.