The free-radical polymerization method was used to prepare crosslinked polymers as tramadol carriers for the controlled release process. The polymers were based mainly on ethylene glycol dimethacrylate (EGDMA) and methacrylic acid (MAA) in two different molar levels: 15 and 13. These two polymers represented the non-imprinted polymers (NIPs). Other corresponding polymers were prepared by adding tramadol hydrochloride during the synthesis that was removed at the end of the preparation process to produce tramadol-imprinted polymers (TIPs). The four polymers were loaded with tramadol for testing their in vitro release at various parameters such as soaking times, pH, and temperatures. The effect of molar ratio and imprinting process on tramadol release was studied. FTIR, TGA, and UV -absorption techniques were used to investigate the prepared and loaded polymers and the releasing process. More physical interactions were observed between the loaded tramadol and the matrix in TIPs than in NIPs. TIP with a molar ratio of crosslinker to polymer equals 13 demonstrated the highest control of releasing tramadol over 12-hour.

A simple method for adsorption and recognition of tramadol-HCl in molecular imprinted poly (methacrylic acid-coethylene glycol dimethacrylate); poly (MAA-co-EGDMA), is described. Seven tramadol imprinted polymers (TIPs) were synthesized based on tramadol hydrochloride as the template molecule, methacrylic acid (MAA) as a functional monomer, ethylene glycol dimethacrylate (EGDMA) as a crosslinker, chloroform as a porogenic solvent and benzoyl peroxide (BP) as an initiator. Other seven non-imprinted polymers (NIPs) were prepared with the same compositions as the TIPs without the template molecule. A simple method for determination of tramadol concentration by optical absorption method was described. The effects of crosslinker and functional monomer concentration, soaking time and the pH on the adsorption efficiency of tramadol by the polymers were studied. TIPs exhibited more adsorption affinity than their NIPs counterparts as they acquired recognition sites to capture the tramadol molecules. The TIP polymer with 15 mmol EGDMA and 1.15 mmol MAA stirred for 3h at 7 pH tramadol solution showed 90% adsorption capability for the tramadol, while the corresponding NIP sample showed 55.6% adsorption. SEM images showed the presence of (micro/meso/macro) pores in such TIP sample.