New antimicrobial systems based on zeolites with RE = La, Gd functional ions

Antibiotic resistance necessitates the transition to fundamentally new drugs, in particular RE(NO₃)₃× xH₂O salts [1]. To reduce the active substance (RE ion) content in drugs while maintaining their functionality, RE/MFI and RE/BEA systems based on MFI and BEA zeolites are offered.

Composites with MFI ((H_x)[(Fe³⁺_xSi⁴⁺_12-x)O₂₄] with Si/Fe=25,68: MFI(Fe25), MFI(Fe68); [(Ti⁴⁺_xSi⁴⁺_12-x)O₂₄] with Si/Ti=47,60: MFI(Ti47), (MFI(Ti60)); and BEA ((H_x)[(Al³⁺_xSi⁴⁺_12-x)O₂₄] with Si/Al=12,150: BEA(Al12), BEA(Al150)) and RE(NO₃)₃×6H₂O (RE=La,Gd) salts were obtained using the cold impregnation method, with solid-phase mixing of the components (1:1.2), grinding (~4 minutes), and annealing (250°C, 1 hour).

The compositions of RE/BEA include amorphous components. Moreover, the samples differ in their particle/associate sizes (N, µm), which are greater with MFI (N=12.5-35 µm) than with BEA (N=7.5-8 µm), except for RE/MFI(Ti60).

The growth inhibition zones (D,mm) of the bacteria S.aureus, E.coli, P.aeruginosa, A.baumannii, and K.Pneumonia and the fungi C.albicans, C.glabrata, and C.parapsilosis on the salts change from D=28 to D=50 mm with D_max for S.aureus on Gd; from D=45 to D=56 mm with D_max for C.albicans on La, which is a record for these microorganisms; and D=0 mm for zeolites. The microorganisms showed high sensitivity to the composites—A.baumannii and P.aeruginosa with D_max=38 mm on Gd/MFI(Ti60) and Gd/MFI(Fe68); and C.parapsilosis with D_max= 45 mm on Gd/MFI(Fe68)—but less compared to that seen for the salts, while maintaining their excellent biocidal properties. Аll the new systems demonstrated antimicrobial activity higher than that of the antibiotic penicillin, which makes them promising for biomedical purposes.

Funding: Funding was received from the Ministry of Science and Higher Education of the Russian Federation, grant number FSFZ-2024-0003.

[1] Kuz’micheva G.M. et all. Crystallography Reports. 2020. V. 65. P. 922-932.