Browsing by Author "Ahumada, Manuel"
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Publication Biofunctional Polyvinyl Alcohol/Xanthan Gum/Gelatin Hydrogel Dressings Loaded with Curcumin: Antibacterial Properties and Cell Viability(2025) Rivera, María; Cament, Alejandro; Ahumada, Manuel; Corrales, Teresa; García, Verónica; Pablos, Jesús; Osorio, Javiera; Ramos, Giselle; Vargas, Leslie; Marcelo Ezquer; Ezquer, Marcelo; Ortiz, J. AndrésThis study explores the development of biocompatible hydrogel dressings incorporating curcumin as an alternative antibacterial agent. In this context, hydrogels were prepared using polyvinyl alcohol, xanthan gum, gelatin, and curcumin as a therapeutic component. FTIR spectroscopy confirmed the successful incorporation of curcumin into the hydrogel matrix, while release profiles demonstrated sustained release. Mechanical testing indicated that xanthan gum reduced elongation and strength in hydrogels, while the combination of xanthan gum and gelatin increased stiffness without loss of elasticity. Curcumin had no major effect on the tensile and rheological properties, preserving the structural integrity of the hydrogels. The hydrogels demonstrated antibacterial activity against Pseudomonas aeruginosa and Staphylococcus aureus ATCC strains, as well as multidrug methicillin-resistant Staphylococcus aureus (MRSA) clinical isolates. Biocompatibility was confirmed through viability assays with immortalized human keratinocytes (HaCaT) and adult human dermal fibroblasts (HDFa), showing no acute cytotoxic effects after 48 h of exposure. Their effective action against clinically relevant bacteria and high cytocompatibility position these hydrogels as promising candidates for infection management and antibiotic resistance mitigation in wound care applications.Publication Electrospun Polyvinyl Alcohol/Sodium Alginate Nanocomposite Dressings Loaded with ZnO and Bioglass: Characterization, Antibacterial Activity, and Cytocompatibility(2025) Ortiz, Andrés; Sepúlveda, Francesca; Flores, Siomara; Saavedra, Marcela; Sáez, Suhelen; Jiménez, Thomas; Murgas, Paola; Troncoso, Scarlett; Sanhueza, Camila; Ulloa, María; Porte, Lorena; Ahumada, Manuel; Corrales, Teresa; Palza, Humberto; Zapata, PaulaChronic wounds pose a great challenge due to their slow healing and susceptibility to infections, hence the need for innovative alternatives to conventional antibiotics, as increasing bacterial resistance limits the efficacy of current treatments. This paper addresses the development of novel electrospun membranes based on polyvinyl alcohol (PVA) and sodium alginate, incorporating therapeutic ZnO and bioglass (54SiO2:40CaO:6P2O5) nanoparticles. While nanocomposites presented smaller fiber diameters than pure polymers, ternary nanocomposites displayed higher values, e.g., in porous areas, values were in the ca. 80-240 nm range and 0.06-0.60 μm2, respectively. The Young's modulus of the PVA/SA membrane, initially 15.9 ± 2.0 MPa, decreased by 65% with 10 wt.% ZnO NPs, whereas 10 wt.% BG NPs increased it by 100%. The membranes demonstrated efficacy against Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA) isolated from a human wound secretion, as well as two ATCC strains: Staphylococcus aureus and Staphylococcus epidermidis. A cell viability assay conducted with HaCaT cells demonstrated nearly complete survival following 72 h of membrane exposure. Their combined Gram-positive antibacterial activity and cytocompatibility support their potential application as biofunctional dressings for the management of chronic and hospital-acquired topical infections, while also contributing to the global effort to combat antibiotic resistance.Item The pore forming capacity of Sticholysin I in dipalmitoyl phosphatidyl vesicles is tuned by osmotic stress(Elsevier, 2017) Ahumada, Manuel; Calderon, Cristian; Lissi, E; Alvarez, Carlos; Lanio, MariaThe osmotic condition modulates the properties of liposomes, particularly those related to their stability and response to external agents such as membrane-active proteins or peptides. In a previous work, we have demonstrated that an osmotic shock can increase, per se, water influx/efflux and the exit of the fluorophore calcein entrapped in the aqueous pool of dipalmitoylphosphatidylcholine (DPPC) and DPPC:sphingomyelin (SM) large unilamellar vesicles (LUVs), suggesting a loss of integrity of the liposome bilayer. In the present work, we have extended our study in order to assess how an osmotic imbalance prior to or synchronous with the addition of a recombinant variant of the pore-forming toxin sticholysin I (rSt I) modifies its pore forming capacity in DPPC and DPPC:SM (1:1) LUVs. Our results conclusively show the capacity of hypotonic gradients to improve the pore forming capacity of rSt I molecules, even in pure DPPC liposomes, rendering pore-formation less dependent on the presence of sphyngomyelin. In fact, non-active toxins in DPPC liposomes become active by a hypotonic imbalance in a similar way to those containing SM as a second component.