Synthesis, antimicrobial activity, and sustainable release of novel α-aminophosphonate derivatives loaded carrageenan cryogel

Novel α-aminophosphonates 4 were synthesized via one pot three-component reaction of 4-aminoantipyrine,
aldehydes, triphenylphosphite and Lewis acid catalyst. The chemical structures of all the synthesized compounds
were elucidated by IR, NMR and MS spectral analysis. The antimicrobial activity of 4 was tested in vitro against
pathogenic microbes such as E. coli, S. aureus, A. niger and C. albicans. Three of them (4f–h) exhibited high antimicrobial activity and were loaded to carrageenan cryogel for drug delivery studies. With the aid of cellulose
nanofibrils (CNF) as reinforcing material and glyoxal as a cross-linking agent, porous cryogels with improved mechanical properties were obtained. Among all, CAR-7 presents the optimum cryogel sample, which contained
around 16% CNF and 0.2 mL/15 mL polymer blend. CAR-7 demonstrated highest mechanical compressive
strength, porosity (80%), and swelling capacity (75%). Sustainable release behavior over 24 h was observed for
the loaded cryogels. The antimicrobial activity of cryogels against S. aureus showed marginal differences between
samples. CAR-9 (loaded with 4f) showed the highest reduction percentage in number of bacterial colonies
(99.94%) followed by CAR-11 (loaded with 4h, 99.3%) and finally CAR-10 (loaded with 4g, 99.29%).