Direct encapsulation of small molecule hydrophilic and hydrophobic actives in alginate microspheres using a novel impinging aerosols method

The hydrophilic antibacterial (metronidazole, MZ) and a hydrophobic non-steroidal anti-inflammatory drug (ketoprofen, KET) were directly encapsulated in alginate microspheres (mean size < 40ym), using the impinging aerosols method. Maximum loadings of 7 and 0.4 % were obtained for MZ and KET respectively with corresponding encapsulation efficiencies of 21 and 4 %. Around 75 and 96 % of the MZ content was released from hydrated and dried microspheres respectively in simulated gastric fluid within 20 min. Similarly, rapid release of 100 % of MZ occurred in SIF within 20 min for both hydrated and dried preparations but with retained anti-bacterial activity. Alginate microspheres encapsulating KET released less than 60 % of the drug in SGF within 2 h. Complete extraction of KET was obtained from hydrated microspheres in SIF in 2 h but was limited to around 70 % from dried samples; moreover KET release was sustained for 7 h. These findings demonstrate the utility of the impinging aerosols method for direct encapsulation of small molecule therapeutics, having a wide range of aqueous solubility in alginate microspheres.