Super-Macroporous Pulluan Cryogels as Controlled Active Delivery Systems with Controlled Degradability

Here, super-macroporous cryogel from a natural polysaccharide, pullulan was synthesized using a cryo-crosslinking technique with divinyl sulfone (DVS) as a crosslinker. The hydrolytic degradation of the pullulan cryogel in various simulated body fluids (pH 1.0, 7.4, and 9.0 buffer solutions) was evaluated. It was observed that the pullulan cryogel degradation was much faster in the pH 9 buffer solution than the pH 1.0 and 7.4 buffer solutions in the same time period. The weight loss of the pullulan cryogel at pH 9.0 within 28 days was determined as 31% ± 2%. To demonstrate the controllable drug delivery potential of pullulan cryogels via degradation, an antibiotic, ciprofloxacin, was loaded into pullulan cryogels (pullulan-cipro), and the loading amount of drug was calculated as 105.40 ± 2.6 µg/mg. The release of ciprofloxacin from the pullulan-cipro cryogel was investigated in vitro at 37.5 °C in physiological conditions (pH 7.4). The amount of drug released within 24 h was determined as 39.26 ± 3.78 µg/mg, which is equal to 41.38% ± 3.58% of the loaded drug. Only 0.1 mg of pullulan-cipro cryogel was found to inhibit half of the growing Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) colonies for 10 min and totally eradicated within 2 h by the release of the loaded antibiotic. No significant toxicity was determined on L929 fibroblast cells for 0.1 mg drug-loaded pullulan cryogel. In contrast, even 1 mg of drug-loaded pullulan cryogel revealed slight toxicity (e.g., 66% ± 9% cell viability) because of the high concentration of released drug.

Sonochemical synthesis of inorganic cryogel Ag2Mo3O10@Ag/AgO: structural characterization, antibacterial activity, and dye adsorption properties

An additive-free ultrasonic-assisted synthesis of a multi-layered Ag₂Mo₃O₁₀@Ag/AgO cryogel (SMSSO) nanocomposite has been developed, and a possible formation mechanism of multi-layered SMSSO was proposed based on characterization results of scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Raman spectroscopy, and diffuse reflection spectroscopy (DRS). The FE-SEM images demonstrated the formation process of the multi-layered SMSSO cryogel over time under sonication, starting with the growth of Ag₂Mo₃O₁₀ nanowires, and the formation of spherical nuclei which turn into an octahedron in the presence of excess silver ions. The antibacterial activity of the synthesized cryogel and its adsorption behavior for hazardous pollutant removal were explored. The results revealed that SMSSO exhibits excellent adsorption properties, with a maximum adsorption capacity of 277.77 mg g⁻¹ and removal of 99/95% for 150 mg L⁻¹ methylene blue (MB) by 0.005 g adsorbent doses at 60 °C and pH 9. It was also confirmed that the synthesized cryogels have good antibacterial activities against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The selective adsorption capability of the cryogel toward cationic dye molecules and antibacterial activity makes it a competent candidate for water purification.

An ultrasonic-assisted synthesis of Ag₂Mo₃O₁₀@Ag/AgO cryogel (SMSSO) nanocomposite was developed, and a possible formation mechanism of multi-layered SMSSO was proposed based on characterization results of SEM, EDX, XRD, Raman spectroscopy, and DRS.