New hydrogels in the poly-N-vinylpyrrolidone – RE(NO3)3×xH2O (RE=La, Gd, Yb) system: Fabrication, structure, bactericidal properties

Composite hydrogels in the poly-N-vinylpyrrolidone – RE(NO3)3 × xH2O system with RE = La, Gd, Yb were prepared in various forms (native, native dried in the air, dried in air and ground into powder). They were studied by methods of wide- and small-angle X-ray scattering, differential scanning calorimetry, scanning electron microscopy, and electron microprobe analysis. The composition of native PVP and PVP with powdered RE(NO3)3 × xH2O includes 4 types of structural water, which content depends on the RE type. The PVP/La(NO3)3 × 6H2O surface includes “flower-like structures” consisting of whisker fragments up to 15–20 μm in size. The size of structural inhomogeneities of air-dried and then swollen in water hydrogels decreases with decreasing RE radii as well as the degree of the swelling. The antimicrobial activity (AMA) in the dark relative to Staphylococcus aureus, Escherichia coli, and Candida albicans is characteristic of all the samples. The AMA of RE(NO3)3 × xH2O (RE = La, Gd, Yb) is more effective by as compared with PVP/RE(NO3)3 × xH2O besides PVP/La(NO3)3 × 6H2O. This can be explained by different composition of particles with lanthanum on the surface of hydrogels as compared with La(NO3)3 × 6H2O. The relationship of AMA with the size of structural inhomogeneities in hydrogels, surface morphology, water content, and the role of microorganisms is not ruled out. [Display omitted] •Poly-N-vinylpyrrolidone-based hydrogels with rare earth nitrates were prepared.•The type of rare earth affects the content of structural water in the hydrogels.•All composite hydrogels possess antimicrobial activity in the dark.•The hydrogels microstructure depends on the type of rare earth.