Tetracycline@silver ions-functionalized mesoporous silica for high bactericidal activity at ultra-low concentration

Impact of Mesoporous Silica Functionalization Fine-Tuning on Antibiotic Uptake/Delivery and Bactericidal Activity

The mesoporous SBA-15 material was surface-functionalized with amino and carboxylic acid groups and used as a platform to investigate the interaction of these chemical groups with tetracycline, kanamycin, and ampicillin antibiotics. The interactions between the antibiotic and the functionalized surfaces were characterized using two-dimensional 1H-13C HETCOR CP MAS and FTIR spectroscopy and indicated that -COO- NH3 + bondings had been formed between chemical groups on the silica surface and drug molecules. The surface modification resulted in higher kanamycin and ampicillin loadings and a slow-release rate, and all synthesized systems showed antibacterial activity against susceptible Escherichia coli bacteria. Almost total death of bacteria was obtained using a few ppm of tetracycline- and kanamycin-loaded systems, whereas the ampicillin-loaded one showed lower bactericidal activity than free ampicillin.

Development of Amino Acids Functionalized SBA-15 for the Improvement of Protein Adsorption

Ordered mesoporous materials and their modification with multiple functional groups are of wide scientific interest for many applications involving interaction with biological systems and biomolecules (e.g., catalysis, separation, sensor design, nano-science or drug delivery). In particular, the immobilization of enzymes onto solid supports is highly attractive for industry and synthetic chemistry, as it allows the development of stable and cheap biocatalysts. In this context, we developed novel silylated amino acid derivatives (Si-AA-NH₂) that have been immobilized onto SBA-15 materials in biocompatible conditions avoiding the use of toxic catalyst, solvents or reagents. The resulting amino acid-functionalized materials (SBA-15@AA) were characterized by XRD, TGA, EA, Zeta potential, nitrogen sorption and FT-IR. Differences of the physical properties (e.g., charges) were observed while the structural ones remained unchanged. The adsorption of the enzyme lysozyme (Lyz) onto the resulting functionalized SBA-15@AA materials was evaluated at different pHs. The presence of different functional groups compared with bare SBA-15 showed better adsorption results, for example, 79.6 nmol of Lyz adsorbed per m² of SBA-15@Tyr compared with the 44.9 nmol/m² of the bare SBA-15.

Enhanced Thermostability and Anticancer Activity in Breast Cancer Cells of Laccase Immobilized on Pluronic-Stabilized Nanoparticles

Laccases are multi-copper oxidase enzymes having widespread applications in various biotechnological fields. However, low stability of free enzymes restricts their industrial use. Development of effective methods to preserve and even increase the enzymatic activity is critical to maximize their use, though this remains a challenge. In the present study we immobilized Trametes versicolor laccase on pH-responsive (and charge-switchable) Pluronic-stabilized silver nanoparticles (AgNPs^Trp). Our results demonstrate that colloidal stabilization of AgNPs^Trp with the amphiphilic copolymer Pluronic F127 enhances enzyme activity (AgNPsTrpF1 + Lac6) by changing the active site microenvironment, which is confirmed by circular dichroism (CD) and fluorescence spectroscopy. Detailed kinetic and thermodynamic studies reveal a facile strategy to improve the protein quality by lowering the activation energy and expanding the temperature window for substrate hydrolysis. The immobilized nanocomposite did not show any change in flow behavior which indirectly suggests that the enzyme stability is maintained, and the enzyme did not aggregate or unfold upon immobilization. Finally, assessing the anticancer efficacy of this nanocomposite in breast cancer MCF-7 cells shows the inhibition of cell proliferation through β-estradiol degradation and cells apoptosis. To understand the molecular mechanism involved in this process, semi qRT-PCR experiments were performed, which indicated significant decrease in the mRNA levels of anti-apoptotic genes, for example, BCL-2 and NF-kβ, and increase in the mRNA level of pro-apoptotic genes like p53 in treated cells, compared to control. Overall, this study offers a completely new strategy for tailoring nano-bio-interfaces with improved activity and stability of laccase.